communal cattle at the wildlife-livestock interface in the Mnisi study area, Mpumalanga, South Africa

Transcription

1 Spatio-temporal variation in the dipping frequency of communal cattle at the wildlife-livestock interface in the Mnisi study area, Mpumalanga, South Africa By Rumbidzai Emily Murapa Submitted in partial fulfilment of the requirements for the MSc Tropical Animal Health to the Department of Veterinary Tropical Disease Faculty of Veterinary Sciences, University of Pretoria Supervisor: Dr J van Rooyen Co-Supervisor: Dr W. H Stoltsz i

2 ACKNOWLEDGEMENTS I would like to express my sincere gratitude the following persons and institutes: The Belgium Development Cooperation (DGD) for providing me with this opportunity by sponsoring this project without which this study would not have been possible. Sincere thanks to my supervisors Dr J van Rooyen and Dr W.H Stoltsz for their advice and guidance. Prof P.N Thompson for the analysis of the data and the advice and guidance. The Department of Agriculture Rural Development Land and Environmental Affairs Mpumalanga province for allowing me to use their records and special thanks to my previous supervisor Dr N.M Ndamase for the encouragement and advice. Special thanks go to my husband Dr Nobert Mangwiro, my daughter Samantha Mangwiro, my father Eben Murapa and my mother Virginia Murapa, it is because of their unfailing motivation and support that I have managed to come this far. ii

3 DECLARATION I, Rumbidzai Emily Murapa hereby declare that the research entitled Spatio-temporal variation in the dipping frequency of communal cattle at the wildlife-livestock interface in the Mnisi communal area, Mpumalanga, South Africa presented in this dissertation, in partial fulfilment of the requirements for the degree MSc (Tropical Animal Health) was executed by myself, under the guidance of my supervisors. I further declare that this dissertation has not been submitted in the past, or is to be submitted for a degree at the University of Pretoria or any other university. Rumbidzai Emily Murapa (BVSc) Date 23/03/2017. iii

4 Table of Contents ACKNOWLEDGEMENTS ii DECLARATION iii LIST OF FIGURES vi LIST OF TABLES vii LIST OF ABBREVIATIONS viii LIST OF APPENDICES ix ABSTRACT x CHAPTER I: INTRODUCTION 1 CHAPTER II: LITERATURE REVIEW Tick control TBDs and other disease risks at the wildlife-livestock interface Influences of dipping frequency on TBDs prevalence Endemic stability Influence of a dipping frequency on ticks Acaricide Resistance Chemical tick control Reasons for dipping Government Dipping Policy Cattle dipping policy in South Africa The gains from a government dipping service to livestock owners The convenience of a dipping service to the government Controlled disease surveillance Non controlled disease surveillance and tick-borne disease control Livestock census Primary animal health care and extension Regulatory (movement and acaricide) Determinants of dipping frequency Factors that affect dipping regimens Socio economic Environmental Political Financial Factors that affect proportion of cattle dipped History of tick control in the Mnisi Study Area 17 iv

5 2.8 Study objectives 18 CHAPTER III: MATERIALS AND METHODS Study area Study design Sample size Data collection Data Analysis 23 CHAPTER IV: RESULTS Dipping frequency Proportion of cattle dipped Seasonal variation Reasons for disruptions 31 CHAPTER V: DISCUSSION Dipping frequency Proportion of cattle dipped Seasonal variation Reasons 40 CHAPTER VI: CONCLUSION 42 REFERENCES 44 APPENDIX 51 Appendix 1: Dip tank monthly register 51 Appendix 2: Animal Ethics Approval 52 v

6 LIST OF FIGURES Figure 1: Cattle dipping at a plunge dip tank 7 Figure 2: Map of the Mnisi study area indicating the geographical distribution of the dip tanks 20 Figure 3: Proportion of dippings and no dipping per annum for all the 16 dip tanks over the 7 year period 25 Figure 4: Proportion of acaricide treatments per dip tank for the period 2006 to Figure 5: Proportion of cattle dipped per annum for all 16 dip tanks 27 Figure 6: Proportion of cattle dipped at each dip tank over the study period 27 Figure 7: Seasonal variation in the frequency of acaricide application for the three seasons a) hot wet (December to March), b) cool dry (April to July), and hot dry (August to November). 28 Figure 8: Seasonal variation in the proportion of cattle dipped for the three seasons a) hot wet (December to March), b) cool dry (April to July), and hot dry (August to November) 29 Figure 9: Reason for disruption in the dipping regimen over the 7 year period 31 Figure 10: Reasons for no dipping across the 16 dip tanks 32 Figure 11: Seasonal distribution of disruptions in dipping 33 Figure 12: Reasons for no dipping across the three seasons 33 vi

7 LIST OF TABLES Table 1: Mnisi communal area dip tanks, mode of dipping practiced and number allocated to the dip tanks for data analysis 21 Table 2: Multiple logistic regression: association of dip tank, year and season with dipping 30 vii

8 LIST OF ABBREVIATIONS & AHT CD CA FAO Fig FMD MCA MSA TB TBDs % and Animal Health Technician Corridor disease Contagious abortion (brucellosis) Food Agricultural Organisation Figure Foot and mouth disease Mnisi communal area Mnisi study area Tuberculosis Tick-borne diseases Percentage viii

9 LIST OF APPENDICES Appendix 1: Dip tank monthly register Appendix 2: Animal Ethics Committee Approval ix

10 ABSTRACT Tick burden and tick-borne diseases (TBDs) in cattle have for centuries plagued most parts of southern Africa, hence the adoption of various tick control strategies. The most commonly used method of tick control has been the application of chemical acaricides to cattle through plunge dipping. Dipping frequency is influenced by factors such as disease risk, eco-climatic conditions, level of vector challenge, animal breed, vector life cycle and the residual effect of the chosen acaricide. Compulsory weekly dipping (intensive tick control) is often implemented by State Veterinary Departments as an aid to effective disease surveillance. Such intensive tick control, however, negatively impacts on endemic stability to TBDs and results in more rapid selection for acaricide resistance, especially amongst one-host ticks. A study was conducted in the Mnisi communal area (MCA), a Corridor disease (CD) and Foot and mouth disease (FMD) controlled area, situated in the north-eastern part of Bushbuckridge Municipality, Mpumalanga, South Africa. Data was collected from 16 sites (dip tanks) corresponding to 16 villages in the area. The study aimed to determine the actual dipping frequency (as opposed to the intended weekly dipping regimen) and factors influencing the dipping frequency. The specific objectives were to determine, a) the number of dipping sessions per dip tank, per season and per year b) the average proportion of cattle dipped per dip tank per session across seasons and years c) to describe the seasonal pattern of dipping frequency and d) the main reasons for variation between actual and intended dipping frequency. A longitudinal, retrospective survey was conducted, based on data obtained from 16 dip tanks of the Veterinary Service of the Department of Agriculture, Rural Development Land and Environmental Affairs in Mpumalanga Province. Descriptive statistics and multiple logistic regression was used to analyse the data. The results indicated a gradual increase in the frequency of dipping over a period of 7 years and across the 16 dip tanks. There was a variation between intended dipping (52 times per annum) and actual dipping (27 times per annum). The dipping frequency and proportion of cattle dipped varied across the seasons and years. The average dipping frequency for the study period was 27 times per annum (53%) and the average proportion of x

11 cattle dipped was 49%.There was a significant difference in the dipping frequency across the three seasons. Disruptions in dipping were noted and the main reasons for not dipping were official leave or temporary reassignment of officials to other disease control programmes and weather conditions mainly rainfall. This study creates an opportunity to discuss the impact of the findings in relation to its implications on acaricide resistance and maintenance of endemic stability to TBDs. The current dipping pattern is discussed and a strategic or less intensive dipping system is recommended. xi

12 CHAPTER I: INTRODUCTION The practice of applying chemical acaricide on cattle as a means of vector control to reduce damage and losses due to ticks and tick-borne diseases (TBDs) dates as far back as the early 19 th century. The most widely used means of chemical control is dipping (Willadsen 2006).Farmers rely on plunge dipping to control ticks and tick-borne diseases. Plunge dipping is the process in which cattle are completely immersed in a tank of water containing a chemical acaricide. In the communal areas dipping is an economic and effective way of applying chemical acaricide because of the number of different herds that are dipped at a time. The number of dippings per unit time can either be strategic or intensive. The intensive dipping system (mainly plunge dipping) involves weekly or twice-weekly applications of acaricides and is the most widely used regimen in Africa (Spickett & Fivaz 1992).Strategic dipping involves application of acaricides at times of the year when tick burden is high. The choice of dipping strategy is mainly influenced by the level of disease risk, eco- climatic zone, tick challenge, the costs of control measures as well as the breed and type of animal (Pegram et al. 1993). It is also influenced by tick life cycle and residual effect of the product being used (De Deken et al. date unknown). It is known that intensive dipping hinders the development of endemic stability to tick-borne diseases where as strategic tick control or reduced dipping frequency permits the development of endemic stability (Cook 1991). The study area is located at the boarder of Kruger National Park in the Bushbuckridge municipal area typical domestic animal-wildlife interface where there is direct or indirect contact characterized by sharing of common grazing or water sources (Motsi et al. 2013). It is a Corridor disease (CD) and Foot and mouth disease (FMD) controlled area according to the Animal Disease Act 35 of Intensive weekly dipping regimen is legislated for Corridor disease (CD) control and as an incentive for cattle owners to bring their cattle weekly for FMD inspection and disease surveillance (Stevens et al. 2007).The dipping and inspection is enforced in line with the government goal of food security and poverty alleviation through ensuring the health of livestock. The regular dipping also facilitates other activities such as animal health extension to stockowners, farmer training and livestock census taking. 1

13 However, it is known that financial, infrastructural and institutional constraints can affect disease control programmes (Norval et al. 1992). A study in the Venda region showed that human resources, attitude and production system had a significant effect on influencing dipping frequency (Randela et al. 2000). Owner attitudes towards tick control, their commitment to other activities and environmental constraints may affect the number of times that they present their cattle for dipping per year (Cook 1991). As a result, the intended dipping frequency of 52 immersions per annum in tick control areas such as the MCA is not always attained for these various reasons. The actual dipping frequency, taking into consideration exogenous factors that may lead to spatio-temporal variation in the area, is not known. Therefore, there is a possibility of diversity in dipping frequencies in the area which can either result in positive or negative consequences for tick control. The investigation of the spatial-temporal variation in the dipping frequency is aimed at evaluating and describing the pattern of the current dipping regimen within the MCA. The actual dipping frequency could be leading to retention or loss of endemic stability to tick-borne diseases at some dip tanks. Knowledge of the actual dipping frequency at the wildlife-livestock interface can lead to influencing farmers and policy makers into considering a strategic and moderated use of acaricide on cattle, which has positive implications in reducing the chance of tick resistance, minimising cost and possibly of achieving and or maintaining endemic stability to TBDs (Sutherst & Comins 1979). The objectives of this study were to determine the number of dipping sessions per dip tank, season and year in the MCA, to determine the average proportion of cattle dipped per dip tank across seasons and years, to describe the seasonal variation in dipping frequency and lastly to determine the main reasons for the observes differences between the actual and intended dipping frequency. 2

14 CHAPTER II: LITERATURE REVIEW 2.1 Tick control Tick-borne diseases such as theileriosis, erlichiosis, babesiosis and anaplasmosis are a major constraint to cattle production. These diseases affect the agriculture sector by hindering sustainability of food security (Jongejan & Uilenberg 2004). In communal areas where livestock is a source of livelihood, losses due to TBDs can be devastating, hence the need for control of ticks and TBDs. Walker (2011) defined tick control as treatment that reduces exposure of livestock to ticks within a specific area and time. It is known that vector reduction or elimination will reduce the effects of the vector and will block transmission of disease that they transmit. In order to achieve the objective of tick and TBDs control various control methods were developed. These include chemical control, chemotherapy, vaccination, use of resistant animals, management and integrated control. The idea of integrated control was first applied in Australia in the 1960s when host resistance and TBDs vaccines were used in combination (de Castro 1997). A study in Australia revealed that pasture rotation combined with dipping reduced the frequency of treatment from 19 per annum to 7 per annum (Wharton et al. 1969). An integrated approach has the advantage of reducing cost of control and delaying development of resistance due to reduced frequency of use of acaricide. No one method is on its own adequate, the most effective and economical control is best achieved by combining vector control, management, chemotherapy and immunisation in a balanced and integrated manner (Irvin 1987) TBDs and other disease risks at the wildlife-livestock interface The wildlife-livestock interface has a great risk of diseases such as FMD, TB, CA and tick-borne CD because of the close proximity of buffaloes and livestock. The African buffalo and other wild animals are reservoirs of disease and they also maintain tick populations. It has been documented in previous studies that buffaloes roam and there is a possibility of livestock sharing grazing land with wildlife (Berrian et al. 2016). In a study conducted in two communal areas that are situated adjacent to wildlife reserves, that is the Zambezi region 3

15 and the Mnisi communal area, most cattle owners sited diseases as major constraint to farming. In the Zambezi region 29% of the respondents mentioned ticks as a major constraint to livestock production and in the MSA area 44 % perceived ticks as their major constraint (Van Rooyen 2017). This indicates the high disease risk in these areas and the need for prioritization with regards to tick control and disease surveillance. Hence there is a need for effective mitigating measures to avoid livestock losses from these diseases Influences of dipping frequency on TBDs prevalence Endemic stability The relationship between dipping frequency and level of tick burden determines whether a state of endemic stability or instability is reached. Endemic stability to TBDs is an epidemiological situation whereby at least 75% of the animals in a given population are seropositive to a particular disease without showing any clinical signs (Rikhotso et al. 2005). For endemic stability to develop cattle must be exposed to a large number of infected ticks (to a certain threshold) at the time when they still have non-specific resistance to certain TBDs (De Deken et al.).the high inoculation rate of calves will lead to infection, seroconversion and development of immunity (Tice et al. 1998). The acquired immunity from this infection will then protect them from future tickborne disease challenge. In such a situation the prevalence of seropositivity in the cattle population is high. Dipping frequency largely determines the prevalence of seropositivity in an animal population (Du Plessis et al. 1992). Cattle that are dipped every 7 to 14 days have low tick burdens, low seropositivity and therefore are at greater risk of being susceptible to TBDs. Intensive tick control does not result in endemic stability to TBDs. Stability has been proven to exist for bovine anaplasmosis, heartwater and babesiosis in areas where the diseases are endemic in Africa (Rikhotso et al. 2005). This endemic stability might not have resulted from efficient dipping policies but more from the failure of intensive dipping regimens which resulted in reduced dipping and therefore development of stability. In a study in the areas adjacent to the Kruger National Park, in spite of the weekly dipping policy the seroprevalence of Anaplasma marginale and Babesia bovis increased towards reaching endemic stability (Stevens et al. 2007). This could be attributed to disruptions in the dipping regimen. 4

16 2.1.3 Influence of a dipping frequency on ticks Acaricide Resistance Tick resistance is when there is an increase in the number of individual ticks in a population that can tolerate a particular dose of acaricide that is normally supposed to be lethal for most ticks within the same species (World Health Organization 2004). It arises as a result of regular exposure of the ticks to an acaricide. Thus there is an association between frequency of acaricide application and likelihood of development of resistance (Willadsen 2006). Increasing dipping frequency can lead to development of resistant ticks. Reduced number of times of application of acaricide reduces selection pressure and delays development of resistance (Kemp 1994). Development of resistance is also influenced by the concentration of acaricide, method of application and the tick genus involved (Kemp 1994). Fernandez-salas et al. (2012) reported that the use of the same acaricide at a frequency of greater than 6 times per annum can lead to emergence of resistance. The rate of development of resistance depends on the number of heterozygous resistant ticks with in the population and selection pressure (Mitchell 1996). A high selection pressure which favours the resistant ticks will lead to development of acaricide resistance faster. The number of times that a tick is exposed to acaricide (acaricide pressure) also has influence on the rate at which resistance develops for example Rhipicephalus microplus spends 3 weeks on a host, If weekly dipping is practiced the tick is exposed to acaricide three times which can result in faster development of resistance. In Africa tick resistance to most acaricides has been reported for Rhipicephalus (Boophilus) microplus and Rhipicephalus (Boophilus) decolaratus (George et al. 2004). These one-host ticks are exposed to the acaricide too frequently if the dipping interval is short. Lack of a dipping policy leads to widespread use of acaricides leading to development of multiple resistance (Okello-Onen et al. 1998). On the other hand a dipping policy might exist but due to disruptions in the system some farmers resort to use of their own acaricide and this uncontrolled use of acaricide and uncontrolled exposure of ticks to acaricides. This can favour selection pressure which could lead to resistant ticks thriving. It is important that resistance be identified early to stop 5

17 further selection for resistant ticks by continuing to use the same acaricide. A government dipping service ensures that only one acaricide is used at a time and this control delays development of multiple resistance Chemical tick control Chemical control by the use of acaricides is the major tick control method employed in most parts of Africa despite challenges such as cost, resistance, environmental pollution and residues (de Castro 1997). The control of ticks on hosts by use of chemicals is an effective tick control method. The methods available for acaricide application are hand spraying, hand dressing, use of a spray race, pour-on and plunge dipping. Cattle plunge dipping is a process whereby cattle are completely immersed in a bath of water containing a chemical acaricide (Fig. 1). The use of a dip tank is considered the most cost effective method of acaricide application. It is the most common method of acaricide application and it is considered a cheaper way than pour-on (Stevens et al. 2007). In the communal areas of Zimbabwe, 71.3% of farmers use the plunge dipping system (Sungirai et al. 2016). 6

18 Figure 1: Cattle dipping at a plunge dip tank There are five strategies that can be used for application of acaricide. a) Intensive control Acaricide is applied regularly that is once to two times a week. It is also known as a suppressive approach which aims at keeping the cattle clean, TBDs free and also free from the physical effects of ticks. This will however lead to an increase in the number of ticks that carry genes for acaricide resistance due to the high exposure of tick to acaricide. b) Strategic control Acaricide is applied tactically to target time of high tick numbers. It is mainly targeted at specific tick generations to eliminate the source for future generations. The aim is to reduce the number of tick vector population. It is more economical than intensive treatment. c) Opportunistic control/threshold control Treatment is done to all animals when the tick numbers are over the economic threshold or acceptable levels. This type of control allows for a greater level of exposure of cattle to infected ticks thereby allowing acquired immunity to develop leading to endemic stability. 7

19 d) Selective control Selected animals are treated, that is those with tick numbers that are above the economic threshold. The advantage of selective treatment is that there is delayed development of resistance e) Alternation The chemical groups of the compound and the formulations are used alternately so that no one compound is used continuously which would lead to the development of resistance. The choice on the strategy to apply is guided by disease incidence, tick pressure, herd size, level of tick resistance and the breed of cattle (Matthewson 1984). Regular dipping might be effective for Bos taurus but it might not be effective or worthwhile for Bos indicus. Required frequency of acaricide application for Bos inducus was found to be 10 to 20% of that required by Bos taurus (Jonsson & Matschoss 1998).Intensive dipping on indigenous breeds cannot be justified from a cost point of view (Frisch 1999). Choice of control is also dependent on the species of tick in the area and the nature of farm (Willadsen 2006). The decision on choice is also guided by considering the policy, type and intensity of control required in order for it to be cost effective (Johnston 1975). Ultimately control strategy need to be economically and socially suitable for the production system of a particular area (de Castro 1997). 2.3 Reasons for dipping In the past dipping programmes in southern Africa where formulated as a strategy for eradication of East Coast Fever.Since its eradication dipping is mainly done to reduce or control the tick vector in order to prevent tick-borne diseases in general. According to Masika et al. (1997) 98% of livestock owners take part in dipping activities for the main purpose of disease control. In a study in the communal area of Limpopo and Mpumalanga in South Africa,90 % of respondents to a questionnaire sited disease control as a reason for dipping (Stevens et al. 2007).Dipping has been shown to reduce mortalities and increase weight gain of livestock (Mbassa et al. 2009). Dipping also prevent the mechanical damage caused by ticks for example the adult Amblyomma variegatum tick which has very sharp mouth parts that can cause extensive damage to teats (Jongejan & Uilenberg 2004). This will result in reduced milk production and will lead to higher calf 8

20 losses. Livestock owners also present their animal for dipping just for the reason of complying with government policies (Masika et al. 1997) Government Dipping Policy A government dipping policy outlines and details the rendering of a dipping service. Government dipping service is defined as the supply of acaricide, personnel and infrastructure by the government animal health authority in communal areas for the purpose of cattle dipping (Limpopo Department of Agriculture 2015). The objectives of a dipping policy are: To ensure herd protection from losses due to TBDs To regulate use of acaricide and the frequency of dipping To improve herd health Controlled and non-controlled disease surveillance To facilitate census data collection and regulate and monitor movement of livestock Tick control policies differ geographically, epidemiologically and ecologically. Due to the east coast fever outbreaks most regions in Africa adopted a short interval dipping although some have now resorted to less intensive dipping system. In Kenya a Cattle Cleansing Act identifies high tick-borne disease risk areas where weekly dipping is made compulsory (Kemp 1994).In some parts of Africa a seasonal intensive dipping or strategic dipping is practiced. For example in Malawi a fortnight dipping in the rainy season November to April is practiced while in winter form May to October there is no dipping. (Kemp 1994).The Swaziland dipping policy states a weekly dipping from November to May and every fortnight for the rest of the year for the eradication of ECF (Kemp 1994). Field experiences in the traditional livestock sector of Zambia show that a weekly dipping regimen is practiced during tick peak seasons that is between November to April the from May to October dipping is discontinued to allow for development of enzootic stability (De Meneghi et al. 2016). 9

21 2.3.2 Cattle dipping policy in South Africa The government views dipping as a key component of disease control in the communal livestock of South Africa. The provincial animal health veterinary service applies the policy by providing the dipping service to ensure control of animal diseases and parasites to promote animal health according to the Animal Disease Act 35 of In the face of an east coast fever outbreak, an order making weekly dipping compulsory was issued and the government constructed structures for the purpose of dipping (Eastern Cape Department of Rural Development and Agrarian Reform 2013). Although east coast fever was eradicated in 1954 the policy still stands due to its benefits that continue to be observed. Frequent dipping continues to be implemented to control buffalo-borne corridor disease which is caused by Theileria parva and transmitted by Rhiphicephalus appendiculatus (Berrian et al. 2016). In communal areas these dip tank facilities are still owned and maintained by the government. The dipping in Mpumalanga is free of charge with the state veterinary services providing the acaricide and personnel. In the Limpopo province a dipping service is only provided in the foot and mouth disease control area. The cattle owner in the province are encouraged to contribute funds through dipping committees for the purchasing of dipping compound (Limpopo Department of Agriculture 2015).In the Eastern Cape province the department provides the acaricide for dipping and all farmers are expected to present their cattle for dipping at interval set by the responsible veterinary authority (Eastern Cape Department of Rural Development and Agrarian Reform 2013) The gains from a government dipping service to livestock owners The benefit of a dipping service to cattle owners is that their cattle are protected from tick transmitted diseases such as babesiosis, anaplasmosis, heartwater, sweating sickness and corridor disease. The reduction of number of ticks on the cattle means that the damage caused by ticks for example damage to the udder, hides and abscesses is also prevented. Other benefits of presenting their animal for dipping is that their animals are 10

22 also inspected for other disease and can receive primary animal health care services at a subsided fee at the dip tank The convenience of a dipping service to the government Dipping is an integral part of government animal disease control programmes in South Africa (de Castro 1997). It brings farmers from a large geographical area together at one point, as one herd making it easier for the department in terms of cutting transport cost of visiting individual farmers. Other disease control activities are done in conjunction with dipping. The department s animal health services disease control benefits from the communal weekly dipping policy in the following ways: Controlled disease surveillance Although the primary purpose for cattle dipping infrastructure was for the control of tick-borne disease which were a major cause of livestock losses in the communal areas, it also now serves other animal health functions such as handling of cattle for the purpose of inspection, vaccination, surveillance. The concentration of cattle at the dipping points allows veterinary services to carry out the compulsory inspection for FMD and also diagnostics for other controlled diseases such as TB and CA surveillance (Randela 2005). FMD inspection would be expensive for the department to organize it on its own without a dipping service and might not receive good turnout by farmers. The use of dipping as an incentive for FMD inspection has potential for FMD inspection to influence dipping into being intensive rather than strategic Non controlled disease surveillance and tick-borne disease control The surveillance and inspection is a potential early warning system to pick up other non-controlled diseases early and to act early should there be need Livestock census The department has an opportunity to take livestock census data for the area which is useful for their planning purpose in terms of procurement of vaccines, acaricide and other working tools for disease control and surveillance. It has been proven that centralized dipping system is a useful tool in collecting information from livestock owners for the purpose of disease control and management (Sungirai et al. 2016). 11

23 Primary animal health care and extension The coming together of farmers at the dip tank allows for extension and advisory services to be rendered to them for example practical training, demonstrations and education on disease awareness (Limpopo Department of Agriculture 2015). Other stake holders can also reach all the livestock owners as they will be congregated at one place. If extension was to be performed independent from dipping it would be unaffordable and unavailing (Randela 2005) Regulatory (movement and acaricide) The government has control over the acaricide used and that they are used at the correct concentration, this has a benefit in that development of resistance is to some extend controlled. However resistance is not only due to misuse of acaricide, but also due to other factors such as frequency of use (Adakal et al. 2013). At the dip tank movement can be controlled and regulated as farmers are required to account for absence of any cattle and movement is authorized through movement permits (Randela 2005). 2.4 Determinants of dipping frequency The number of times that cattle are treated for ticks is dependent on various factors. The major factor is the disease epidemiology of the area, that is the prevalence of tick-borne diseases.the presence of ticks on the animals and prevalence or extend of other problems cause by ticks for example abscesses also influence frequency of treatment. High disease risk areas such as the wildlife-livestock interface have an intensive type of application. An average of 26 immersions for an intensive type of dipping has been recorded in a study in the Limpopo province (Rikhotso et al. 2005) although in some areas in South Africa frequencies of up to times per year are being practiced ( Spickett & Fivaz 1992). Ecology of vector and epidemiological knowledge of ticks determine frequency of application (de Castro 1997). The species of tick in the area can influence the frequency of treatment with acaricide for example Rhiphicephalus (Boophilus) decolaratus can be controlled by a 21 day dipping interval (Regassa et al. 2003). An all year round regimen is adopted for species that reproduce throughout the year for example Ambylomma hebraeum and Rhiphicephalus evertsi evertsi. In the equatorial regions of Africa tick activity is all year round 12

24 meaning that an intensive regimen is justified (De Deken et al.). On the other hand some tick species for example Rhipicephalus appendiculatus, show a seasonal pattern in which the adult tick activity peaks in the late summer (January to February) and drops from March to May (Rechav 1982). It is also important to determine whether the species transmit any diseases because if they are harmless then there would be no need for tick control (Irvin 1987). Frequency of treatment also depends on climate and region (Elder et al. 1980).The dipping interval can be influenced by the season which determines vector abundance which informs a weekly dipping in summer and fortnight dipping in some subtropical regions. The frequency of application depend on the type of acaricide that is to be used (Mbassa et al. 2009).The residual effect of the acaricide also determine how often the acaricide is applied. If there is use of compounds with no residual effect, a weekly dipping regimen is ideal for the control of tick species such as Amblyomma hebraeum, adult Hyalomma species, Rhipicephalus evertsi evertsi (De Deken et al.).unlike old day acaricides modern acaricides with longer residual activity on cattle should be able to assist farmers by lifting the burden of weekly dipping (Walker 2011). Regional variation is caused by differences in tick challenge, level of education and employment of owners in cases were a dipping fee is required. Randel et al. (2000) stated that dipping frequency is influenced by liquidity. Variations in dipping frequency between dip tanks can be influenced by ticks and tick-borne disease knowledge by the farmers, some may not be fully aware of the need for regular dipping (Stevens et al. 2007).Government policies can result in variations in dipping frequencies between regions for example the Limpopo and Mpumalanga dipping frequencies noted by Stevens et al was due to differences in policies whereby in Mpumalanga the dipping service was for free while in Limpopo a levy was required (Stevens et al. 2007). Availability of resources also determines how often an acaricide is applied. Lack of repair of dip tanks, acaricide and water could result in dipping being incoherent and inconsistent (Eisler et al. 2003). Reduced application of acaricide reduces the burden of costs for example a study in a traditional production system in Zambia, intensive acaricide treatment of 36 treatments per year resulted in a benefit to cost ratio of 7:1 13

25 indicating the cost benefits of reduced dipping (Walker 2011).A strategic plan of 12 immersions per year applied only in the wet season gave a benefit to cost ratio of 20:1 (Walker 2011). In a modelling study done in Zimbabwe, a reduced dipping frequency of 21 from the documented 45 emersions per year was reported to reduce cost by 45 % over a period of 20 years (Norval & Deem 1994). A study in Uganda in which a twice a week dipping interval and once a month dipping regimen were compared, it was found that the twice a week dipping yielded good results in reducing mortalities and increasing live weight gain. However an overall financial analysis revealed that higher gross margins were obtained with a once a month dipping system indicating that it was a more cost effective and sustainable means of control (Okello-Onen et al. 1998). 2.5 Factors that affect dipping regimens A set dipping regimen can be interrupted or disturbed due to a number of reasons. These reasons can be classified into the following categories: Socio economic The profile of the farmers that is their age and their occupation will determine if they adhere to a dipping regimen or not. Most cattle owners are geriatrics who might be unable take the cattle to the dip tank regularly, such farmers will participate more during school holidays when there is aid from the young people (Sungirai et al. 2016). Weekly dipping is demanding with regards to the amount of effort that is required from both the owner and veterinary service and also the costs involved (Lawrence, Perry & Williamson 2004). In KwaZulu Natal South Africa the aim is to achieve a maximum dipping of 40 per year but due to factors such as weather and other commitments in disease control the average dipping frequency was actually dippings per annum (Musisi & Dolan 1999) Environmental Interruptions of dipping can be due to drought because dip tanks become non-functional due to lack of water, however the droughts also lead to reduction in the tick population which would make the unintentional reduced frequency ideal for such a situation (R. Norval, Perry & Hargreaves 1992). During the 1983 drought in the Venda region of South Africa, all dip tanks in the region were non-operational, due to lack of water to fill the dip 14

26 tanks (Randela 2007). In a study in the Venda region 14% of farmers indicated that water was a major problem at the dip tanks (Simela 2012).In Malawi it was reported that only 20 to 40% of cattle were dipped regularly as stipulated in their weekly compulsory dipping this was due to weather and acaricide shortage (Kemp 1994).It is evident that shortage of acaricide or water results in cattle not being intensively dipped. Terrain is a constraint that can inhibit farmers to stick to a regular dipping regimen Political Political instability can result in the disruption of a dipping regimen. During the 1972 to 1982 war in Zimbabwe dip tanks were destroyed and that resulted in a halt of all dipping activities (Randela 2007). In a study in Zimbabwe it was indicated that disagreements amongst farmers on the management,duties of re-filling or maintenance, disrupts dipping (Sungirai et al. 2016).The guerrilla war between 1973 and 1979 disrupted the intensive dipping system in Zimbabwe resulting in high cattle mortalities due to tick-borne diseases (R. Norval & Deem ). In the Reitgat area of the Northwest province in South Africa, a regimen of 2.4 times per month in summer and 1.6 times per month in winter was disrupted due to dip tank management issues (Tice et al. 1998).In the southern states of the United States a weekly dipping regimen was disturbed by farmers putting explosives into the dip tank as a way of revolting against a government dipping system (Walker 2011). Although factors such as infrastructure, personnel, transport and acaricide are required for the successful implementation of a tick control programme, political stability is ranked as the most important factor (Lawrence et al. 2004) Financial The cost of a dipping service to the government involves dip construction and maintenance, vehicle service and insurance, stock register stationary, water pumps and connections and the cost of the acaricide (Randela 2005).The global cost of control of tick and tick-borne diseases was estimated to be up to US$ 18.7 billion (de Castro 1997).In Malawi the budget for acaricide is the largest on the operational needs of the veterinary department (Kemp 1994),this could be true for most areas were intensive dipping is practiced. In Tanzania a study indicated that about 25% of farmers believed failure of effective control of tick-borne diseases was due to the cost of acaricide and lack of functioning dip tanks (Mbassa et al. 2009). 15

27 The average volume capacity of a dip tank is from 8000 to litres of water and acaricide requirement would be more than 10 litres to replenish (De Meneghi et al. 2016). Financial constraints that lead to shortage of acaricide can disrupt a dipping regimen. In a study in Zimbabwe delay in acaricide provision from the government would delay dipping with more than a month (Sungirai et al. 2016). When a dip tank is closed for a month or more some farmers will also not dip their cattle for that period of time there by disrupting the dipping regimen.in cases were a dipping levy is required some farmers might not present their cattle due to financial constraints. The introduction of a dipping levy in the Geluk area in Mpumalanga South Africa led to a drop in dipping rate from 71% to 55 % over a period of 3 years (Tice et al. 1998). In Kenya factors such as shortage of money disturbed a regular dipping regimen (Kemp 1994). In Tanzania a quarter of the 2100 dip tanks were not fully operational due to financial constraints, poor maintenance, water shortage and poor policy implementation (Musisi & Dolan 1999). 2.6 Factors that affect proportion of cattle dipped Interruptions in the dipping regimen which result in low turnout of cattle or no turn out at all could be related to distance (if farmers stay far away from the dip tank) and the ability of farmer to herd the cattle to the dip tank regularly. In Zimbabwe some farmers were staying more than 10 kilometres away from the dip tank (Sungirai et al. 2016) making it difficult for them to present the cattle weekly for dipping. In the Eastern Cape the dipping policy requires that there should be a dip tank facility within a 4-5 kilometre radius (Eastern Cape dipping policy).in a study done in a communal area in Zimbabwe, an average dipping turnout of 82% of the total cattle number in the area and a dipping frequency of 17 occasions per year was reported (R. Norval & Deem 1994). Farmers seem to follow a seasonal pattern when it comes to dipping. In winter most farmers present their cattle infrequently for dipping due to the perceived absence of ticks on their animals (De Deken et al. date). Farmers will present their animals more regularly for dipping in the spring and summer period than in winter (Randela 2005).Farmer knowledge on tick TBDs can affect the turn out to dipping events In a study conducted in Zimbabwe only 67.7% of the farmers were aware of TBDs (Sungirai et al. 2016). 16

28 Farmers can also not show up because they will be using other means of tick control apart of the dipping provided for by the government. Farmers supplement the government dipping with other methods of control such as acaricide and traditional (Sungirai et al. 2016). According to a study by Simela, 78% of the farmers who presented their cattle for dipping have other supplementary methods to control ticks (Simela 2012). Other control method such as traditional methods are common in communal areas were resources are lacking (Hlatshwayo & Mbati 2005). It is an essential key for the future of tick control in communal areas to try and understand or to investigate the level of participation by livestock owners in tick control programmes (Sungirai et al. 2016). 2.7 History of tick control in the Mnisi Study Area Livestock rearing is the main mode of farming in the MSA.The majority of herds are Nguni cross breeds (Stevens et al. 2007).The main tick-borne diseases that are prevalent in the area are babesiosis, anaplasmosis and heartwater (Rikhotso et al. 2005).Compulsory weekly dipping has been enforced in the area since the beginning of the 20 th century when there was an outbreak of ECF in South Africa (Hlatshwayo & Mbati 2005).The weekly dipping is combined with the weekly inspection for foot and mouth disease which is a state controlled diseases and the control policy requires that weekly inspections be done. The dipping serves as an incentive to lure farmers for the FMD inspection which is considered highly important as it is a disease of high economic importance. The dipping system is used for application of acaricide as it is easy to apply to the communal herds and it also proves to be effective. A study in the Mnisi area indicated that 90.2 % of the farmers controlled ticks by plunge dipping (Simela 2012). With the communal farming dipping system, cattle belonging to various owners are treated as one herd based on their proximity to a particular dip tank. The AHT records the number of animals dipped per session and the amount of acaricide used and updates stock cards. Acaricide is provided by the government. The major acaricides used in the area are of the amides, organophosphates and the pyrethroid group (Malan 2016). The government is responsible for maintenance of the dipping facilities. Dipping is provided for free by the government. In a study done by Lazarus 82% of the farmers favoured dipping of all the activities at the dip 17

29 tank (Lazarus 2014) meaning dipping pattern or frequency has potential to influence the frequency of other activities. A questionnaire based study conducted in the area based on 72 herds from 11 dip tanks recorded an 82% dipping frequency in summer and a 79% frequency in winter (Stevens et al. 2007). Previous studies in the area indicate that weekly dipping is sometimes disrupted due to infrastructure, budgetary constraints and water shortages especially in the dry season (Berrian et al. 2016).The survey by Berrian et al. (2016) indicated that 35% of cattle farmers did not apply acaricide on their cattle for a whole month. Rikhotso et al. (2005) concluded that intensive cattle dipping was not necessary in the Bushbuckridge region due to the low tick burden in the area. 2.8 Study objectives A weekly dipping for cattle in the Mnisi communal area is intended for the purpose of TBDs control and other disease surveillance. However this is not always achieved due to various constraints. Thus the actual dipping frequency taking into consideration these factors is not known. The objectives of this study were to determine the following: i) The number of dipping sessions per dip tank per year ii) iii) iv) To determine the average proportion of cattle dipped per dip tank across seasons and years To describe the seasonal pattern of dipping frequency of dipping frequency To describe the main reasons for variation between the actual and the intended dipping frequency Knowledge of the actual dipping frequency could be used as a guideline in the review of dipping policies and could assist in the understanding of other aspects such as acaricide resistance and endemic stability in the area. 18

30 CHAPTER III: MATERIALS AND METHODS 3.1 Study area The Mnisi Study Area (MSA) is situated in the north-eastern part of the Bushbuckridge Local Municipality of Mpumalanga, South Africa. The MSA is an area in which the Mnisi Community Programme of the Hans Hoheisen Research Platform of the University of Pretoria conducts a range of research and development activities in association with communities, government and other agencies. The area experiences a subtropical climate characterized by hot and wet summers and cool and dry winters. It has a savannah ecosystem and is a semi-arid region with an average annual rainfall of 550mm (Treydte et al. 2013).The study area covers approximately ha of land (Robbertse et al. 2016).The estimated number of livestock owners are 1,300 and the approximate total number of cattle is 15,000 (Van Rooyen 2017). The area is a foot and mouth disease protection zone (Department of Agriculture, Forestry and Fisheries, Directorate: Animal Health, 2012) where vaccination of all cattle is mandatory three times a year and weekly clinical inspections are done weekly. Surveillance for tuberculosis and brucellosis is also done regularly by local state veterinary services. Ticks and tick-borne diseases are controlled by weekly application of acaricide by means of plunge dipping and hand spraying. The epidemiological unit, which is the dip tank, where cattle are brought for Primary Animal Health Care which includes disease surveillance, inspection (FMD) and dipping for the control of ticks and tick-borne diseases was under the management of provincial veterinary services (Mpumalanga Veterinary Services) who kindly made all dip tank registers available for analyses. The MSA consist of sixteen dipping points of which 14 are plunge dips and 2 are crush pens. These are divided into three Animal Health Wards, Bushbuckridge-1, Bushbuckridge-2 and Bushbuckridge-3 (Fig. 1) with at least 5 dipping points each. Each ward is serviced by an Animal health technician (AHT) and support staff. The department provided for the maintenance of infrastructure, dipping compound, personnel to supervise, coordinate and record all dipping, and inspection activities. 19

31 Figure 2: Map of the Mnisi study area indicating the geographical distribution of the dip tanks 20

32 Table 1: Mnisi communal area dip tanks, mode of dipping practiced and number allocated to the dip tanks for data analysis Name of dip tank Ward Mode of dipping Geographical location Number Allocated Latitude Longitude Athol B2 Plunge Clare A B3 Plunge Clare B B3 Plunge Dixie B2 Plunge Eglington B1 Plunge Gottenburg B3 Plunge Hlalakahle B1 Hand spraying Seville A B2 Plunge Seville B B2 Plunge Share B3 Plunge Shorty B3 Plunge Tlhavekisa B1 Plunge Utha A B2 Plunge Utha Scheme B2 Plunge Welverdiend A B1 Plunge Welverdiend. B B1 Hand Spraying Study design A longitudinal, retrospective survey was conducted over a period of 7 years to determine the spatio-temporal variation in dipping frequency in the MSA. Data collected through the state veterinary services as part of the foot-and-mouth disease control policy from the year 2006 to 2012 was used. 21

33 3.3 Sample size The total population of the cattle in the study were obtained from cattle register records. Data from all cattle in the study area was collected. 3.4 Data collection Animal health technicians completed the cattle register for each dip tank every week during dipping and inspection. The data was captured into Microsoft Excel from paper-based monthly reports submitted by each AHT in the study area to the local state veterinary office as part of routine reporting procedures (Appendix 1).The weekly registers are consolidated into a monthly report for each Ward which consist of five dip tanks each. Data used for this analysis was derived from the archived monthly reports and captured onto excel as follows: i) Name of dip tank, year, month and week of dipping ii) Total number of cattle dipped and/or inspected per session iii) Demographic changes in the total herd at the beginning and at the end of each month iv) Reason recorded by the attending official in the cases where dipping should have but did not occur. No dipping took place over weekends or on public holidays. Data captured for 16 dip tanks was combined on a single day, of which 14 of these were plunge dips and 2 of these were crush pens where the pour-on system is used. The 16 dip tanks were coded number 1 to 16 (Table 1). The dip tanks were further categorised based on geographical location into three wards named B1, B2 and B3. For each dip tank the number of cattle dipped was recorded for each week from February 2006 to December The months were coded 1 to 12, they were further categorised into 3 distinct seasons hot wet (December to March), cool dry (April to July) and hot dry (August to November). The total number of cattle dipped per month was recorded and the demographic changes in the total number of cattle registered to a dip tank were also captured for the cattle register. During data capturing, in cases where no data was recorded for dipping but data was recorded for inspection it was assumed that dipping had not taken place. Where no data for either dipping or inspection was recorded without a reason it was considered a missing value 22

34 When dipping did not take place the reason why it did not take place was recorded by the responsible AHT. For the purposes of this study the reasons provided for non-dipping events were categorised into 10 major groups, that is; staff leave, staff administration related duties, weather conditions mostly rainfall, infrastructural constraints such as no water supply, commitment of staff with other disease control programmes, such as vaccination or a disease outbreak, transport related, staff absent on training and absence of farmers. In cases were the responsible official was on leave, it was recorded as leave in the cattle register although a replacement person would be assigned to continue with the other activities of the day (Dr B. Rikhotso, personal communication). In cases where the reason for no dipping was either not recorded or unknown the incidents were excluded from the analysis. 3.5 Data Analysis Data from all of the 16 dip tanks in the Mnisi communal area was used for the analysis. If one or more records existed for a particular dip tank-month combination, and if records were missing for one or more weeks during that same month, then it was assumed that dipping had not taken place in the week (s) for which the records were missing. However, if no records existed for a dip tank-month combination, the monthly report was missing and data for that month and particular dip tanks were entered as missing. When the number of cattle was recorded for inspection but not for dipping it was assumed dipping did not take place. No data recorded for a particular dip tank for a particular week for either dipping or inspection without a recorded reason, were considered missing values. The unit of analysis was the dip tank-week combination. A dip tank week is defined as a week that cattle were eligible for dipping which is therefore every week of the entire study period. The proportion of the total cattle population that was dipped was calculated as the number dipped divided by a denominator reflecting the total cattle population eligible for dipping during that dip tank-week. For the first and last weeks of each month, this population appeared in the records; for the intervening weeks the population was estimated by adding ⅓ or ⅔ of the difference between ending and starting population (four-week months) or ¼, ½ or ¾ of the difference between ending and starting population (five-week months). In the occasional instances where this calculation 23

35 yielded a proportion greater than 1, the proportion dipped was assumed to be 1. If dipping did not take place, or was assumed not to have taken place during a dip tank-week, the proportion dipped was set to 0. The proportion of the total population dipped was summarized by year, dip tank, month and season. Exact binomial (Clopper-Pearson) 95% confidence intervals were calculated for proportions. The association of dip tank, year and season with whether or not dipping took place was assessed first for each of the three variables by cross-tabulation and the chi-squared test, and then using a multiple logistic regression model to adjust for confounding (Table 2). The reasons for no dipping were assessed by cross tabulation with dip tank and season and significance was assessed using the chi-squared test. All statistical analyses were done using Stata 14 (StataCorp, College Station, TX, U.S.A.) and significance was assessed at P <

36 Frequency (%) CHAPTER IV: RESULTS 4.1 Dipping frequency Of the approximately 5776 dip tank weeks during the period 2006 to 2012 dipping records existed for 4686 dip tank weeks. Dipping occurred on 2498 of these. The average frequency of dipping for the study period was 53.3% per annum. The proportion of dipping for each year is shown in Fig. 3. The dipping frequency increased over the period of years from 2006 to There was significant variation (P< 0.001) in the dipping frequencies across the years. The highest frequency of 70% was in 2012 and the lowest number of dipping sessions was in 2006 (37%) Year dipping Figure 3: Proportion of dippings and no dipping per annum for all the 16 dip tanks over the 7 year period The odd of dipping in 2012 were 4 times (95% CI: ) more than those in the year There was no significant difference in dipping frequency between the years 2006 and 2007.The frequency of dipping also varied across the dip tanks as shown in Fig

37 treatment frequency (%) Dip tank Figure 4: Proportion of acaricide treatments per dip tank for the period 2006 to 2012 The dipping frequency varied across the 16 dip tanks with an average of 53% for all dip tanks over the 7 year period. The dip tank with the highest frequency (73%) was dip tank 14 (Utha scheme) and the dip tank with the lowest frequency (37%) over the 7 year period was dip tank 15 (Welverdiend A). A multiple logistic regression model which adjusted for dip tank, year and season revealed that all dip tanks except dip tank 5 have significantly lower dipping frequencies as compared to the baseline dip tank 14(Table 2). 4.2 Proportion of cattle dipped Over the entire study period the mean proportion of the population that was dipped was 49.1% (95% CI: 47.7, 50.4%). The proportion varied significantly between years and dip tanks (Fig. 5 and Fig. 6). When a dipping event took place the majority of eligible animals were dipped. 26

38 propotion dipped (%) % cattle of dipped year Figure 5: Proportion of cattle dipped per annum for all 16 dip tanks The proportion of cattle dipped increased from 33.4% (95% CI: %) in 2006 to 65.7% (95% CI: %) in 2012(Fig. 6). The highest proportion where dipped in the years 2010 which was 60% (95% CI: %) and 65.7% (95% CI: %) in Dip tank Figure 6: Proportion of cattle dipped at each dip tank over the study period The dip tank with the highest proportion of cattle dipped was dip tank 14 (71%) while dip tank 15 had the lowest proportion of cattle dipped (28%). Of the 16 dip tanks only 7 dip tanks (1, 6, 7, 9, 11, 12 and 15) had a dipping proportion of 50% or above. 27

39 frequency of treatment 4.3 Seasonal variation The frequency of acaricide application varied significantly across the seasons (P<0.001) from 57% in the hot wet season, 53% in the cool dry season, to 50% in the hot dry season (Fig. 7) Hot wet cool dry seasons hot dry Figure 7: Seasonal variation in the frequency of acaricide application for the three seasons a) hot wet (December to March), b) cool dry (April to July), and hot dry (August to November). The proportion of animals dipped per season also showed a similar pattern with the highest proportion being in the hot wet season 52% (95% CI: %) and lowest in the hot dry season 46% (95% CI: %) (Fig. 8). The odds of dipping after adjusting for year and dip tank for the hot wet season was 1.18 more than that of the cool dry season (95% CI: ; P = 0.036) (Table 2). 28

40 proportion treated Hot wet cool dry seasons hot dry Figure 8: Seasonal variation in the proportion of cattle dipped for the three seasons a) hot wet (December to March), b) cool dry (April to July), and hot dry (August to November) 29

41 Table 2: Multiple logistic regression: association of dip tank, year and season with dipping Variable and level Odds Ratio 95% CI (OR) P-value Dip tank Year Season , 0.66 < , 0.54 < , 0.34 < , 0.40 < , , 0.75 < , 0.58 < , , , , , 0.53 < , 0.46 < , 0.25 < , 0.29 < , , , 3.09 < , 3.79 < , 3.31 < , 5.62 <0.001 cold dry 1 hot dry , hot wet ,

42 % reason for no dipping 4.4 Reasons for disruptions Of the total number of disruptions in dipping events (non-dipping on a potential dipping day), reasons were specified in 32.28% of the total disruptions. Where the reason for no dipping was recorded or known, the major reason was due to the responsible official taking leave 35%, followed by the official being committed to other disease surveillance programme (20%) and weather conditions mainly rainfall (18%) (Fig. 9). Infrastructural constraints such as no water supply and no crush pen was the least recorded reason why dipping did not occur (1%). Absence of farmers as a reason why dipping did not occur was an uncommon reason (3%). Administrative duties hindered dipping on 5% of the times. The reason of staff attending training and assisting in other areas was 4% and 7% respectively. Transport related issues accounted for 4% of the times that dipping did not occur Figure 9: Reason for disruption in the dipping regimen over the 7 year period 31

43 % Proportion Dip tank Staff leave Controlled disease surveillance Infrastructural constraints Movement regulation Staff administrative duties Staff Training Farmer absence Staff assisting in other areas Weather conditions(rain) Lack of Transport Figure 10: Reasons for no dipping across the 16 dip tanks The reasons for disruptions varied significantly across the 16 dip tanks (P<0.001). Official leave and controlled disease regulation were the major reasons affecting all dip tanks (Fig. 10). Infrastructure related constraints were recorded for dip tanks 3 (6%), dip tank 6 (2%) and dip tank 11(11%). Farmer absenteeism was highest at dip tanks 7(5%), 8 (7%) and 9 (22%). Weather related constraints affected all dip tanks. 32

44 % frequency % distruptions hot wet cool dry season hot dry Figure 11: Seasonal distribution of disruptions in dipping Level of disruptions varied significantly across the three seasons (P<0.001). Most disruptions were in the hot dry season (35%) while the least were in the hot wet season (31%) (Fig. 11) hot wet cool dry hot dry Figure 12: Reasons for no dipping across the three seasons 33