Ondersteprt Jurnal f Veterinary Research, 66: 1-1 (1999) The epidemilgy f rabies in Zimbabwe. 1. Rabies in dgs {Canis familiaris} J. BINGHAM1*, C.M. FOGGIN1, A.1. WANDELER2 and F.W.G. HILL3 ABSTRACT BINGHAM J., FOGGIN C.M., WANDELER A.I. & HILL FW.G. 1999. The epidemilgy f rabies in Zimbabwe. 1. Rabies in dgs (Canis familiaris). Ondersteprt Jurnal f Veterinary Research, 66:1-1 The epidemilgy f rabies in dgs in Zimbabwe is described using data frm 195, when rabies was re-intrduced after a 37 -year absence, t 1996. Dgs cnstituted 45,7% f all labratry-cnfirmed rabies cases and were the species mst frequently diagnsed with the disease. Slightly mre cases were diagnsed frm June t Nvember than in ther mnths. Frm 195 t the early 198s, mst dg cases were recrded frm cmmercial farming areas, but since the early 198s mst have been recrded frm cmmunal (subsistence farming) areas. This change appears t be due t imprved surveillance in cmmunal areas and nt t any change in the prevalence f rabies. Dg rabies therefre appears t be maintained mainly in cmmunal area dg ppulatins, particularly the large cmmunal area blcks. Urban rabies was nt imprtant except in the city f Mutare. Where dg rabies prevalence was high, the disease was cyclic with perids between peak prevalence ranging frm 4-7 years. Dg rabies cases were, n the whle, independent f jackal rabies and rabies in ther carnivres. There was a significant negative relatinship between the annual number f rabies vaccine dses administered natinally t dgs and the annual number f dg rabies cases lagged by ne year, indicating that the past levels f immunisatin cverage have had a significant effect n the number f rabies cases. Hwever, dg vaccinatin cverage has clearly nt been adequate t prevent the regular ccurrence f rabies in dgs. Keywrds: Canis familiaris, dmestic dg, epidemilgy, rabies, Zimbabwe INTRODUCTION The first reprted cases f rabies in Zimbabwe ccu rred in 192. Dmestic dgs (Canis familiaris) were the principle species invlved in the epidemic and althugh it spread t cver mst f the cuntry, * Authr t whm crrespndence is t be directed Present address: Rabies Labratry, Ondersteprt Veterinary Institute, Private Bag X5, Ondersteprt, 11 Suth Africa 1 Central Veterinary Labratry, P.O. Bx CY551, Causeway, Harare, Zimbabwe 2 Animal Diseases Research Institute, P.O. Bx 113, Statin H, Nepean, Ontari, K2H 8P9, Canada 3 University f Zimbabwe, P.O. Bx MP 167, Munt Pleasant, Harare, Zimbabwe Accepted fr publicatin 2 December 199B-Editr rabies was n lnger present after 1913, apparently due t the large number f dgs killed and the strict dg laws that were intrduced t cntrl the disease (Swanepel, Barnard, Meredith, Bishp, Bruckner, Fggin & Hubschle 1993). Apart frm a minr utbreak in dgs n the Zambian brder in 1938, rabies was nt diagnsed in the cuntry until 195, when it was intrduced acrss the suthern and suth-western brders by dgs. This utbreak spread rapidly in the dg ppulatin and within 4 years the disease was present in mst areas f Zimbabwe (Fggin 1988). Rabies in dmestic dgs was the main surce f human rabies in Zimbabwe between 195 and 1986. During that perid 15 human cases were cnfirmed in the labratry and 9 % f these were caused by dg bites. Dgs als cause mst f the bites which require anti-rabies treatment (Fggin 1988).
Epidemilgy f rabies in Zimbabwe. 1 Cntrl f dg rabies by mass vaccinatin campaigns was initiated in 1951 with Flury lw egg passage (LEP) live vaccine. In the early 198s the use f inactivated tissue culture vaccines supplanted Flury LEP (Fggin 1988). Legislatin stipulates that dgs must be vaccinated at 3 and 12 mnths f age and thereafter within every 3 years. In the cmmunal (subsistence farming) areas the majrity f dg vaccinatins are administered during annual vaccinatin campaigns cnducted free f charge by the Department f Veterinary Services. When rabies prevalence within lcalised areas is high, tw r mre campaigns may be cnducted annually. Urban dgs are vaccinated by gvernment r private veterinarians. In 1986, Brks (199) estimated that 4% f dgs abve the age f 3 mnths had been vaccinated at least nce. The aim f the study reprted in this paper was t determine the epidemilgical patterns f rabies in dgs in Zimbabwe. Cnclusins frm this study culd be imprtant in predicting the future prevalence and patterns f dg rabies and in planning cntrl strategies. The epidemilgy f jackal rabies in Zimbabwe is reprted in a separate paper (Bingham, Fggin, Wandeler & Hill 1999). MATERIALS AND METHODS Data surces Prevalence data n all labratry-cnfirmed rabies cases, which ccurred frm 195-1996 inclusive, were used in the analysis. The diagnsis f rabies was carried ut at the Central Veterinary Labratry, Harare, using specimens cnsisting f glycerl-saline preserved r frmalin-fixed brain tissues. Until 1967 rabies was diagnsed histlgically (Seller's stain) and bilgically (intracerebral inculatin f mice) but thereafter the histlgical test was replaced with the flurescent antibdy test (FAT) (Dean, Abelseth & Atanasiu 1996). Since then, the FAT and the muse inculatin tests (Kprwski 1996) have been the principal means f diagnsis (Fggin 1988). Recrds f each psitive case, which included data n date f receipt f the specimen at the labratry, species, land use type and the gegraphical grid reference at the pint f rigin, were entered int a cmputerised database (dbase 4, Brland). Data n dg vaccinatin recrds were btained frm Department f Veterinary Services' mnthly and annual reprts. Vaccinatin cverage is best expressed as a percent f the ttal dg ppulatin, but as n regular dg census data exists, whereas human census data is available, dg vaccinatins are expressed as dses per 1 peple, with the assumptin that the dg:human rati remains cnstant. Data n human ppulatins were btained frm census reprts (Central Statistics Office 1985, 1994). In the years between censuses, the human ppulatin was calculated frm the inter-census grwth rates. Fr the years 1993-1996, the pre-1992 inter-census grwth rate was used. Data analysis Mst data analysis was carried ut using dbase 4 prgramming language. This included analysis f tempral and spatial trends and relatinships between cases f different species. Gegraphical analysis was assisted by the use f Idrisi fr Windws sftware (Clark University, Wrcester, MA, USA) t display maps with case lcalities and case frequency data. Fr the determinatin f distance (d) between cases a dbase 4 rutine was cmpiled based n the frmula d = -V((1 5X}2 + (11 Oy)2), where x and yare the differences between the lngitude and latitude crdinates, in degrees, respectively. One degree f latitude is 11 km, while ne degree f lngitude varies between 13 and 17 km in Zimbabwe. Using a median lngitude f 15 km gives a maximum distance errr f less than 2%. This was cnsidered sufficiently accurate fr the purpses f this study, particularly as the study was nly cncerned with distances less than 1 km and the reslutin f gegraphical reference c-rdinates was 1 km. Jackal-assciated cases are defined as thse dg rabies cases fr which at least ne jackal rabies case ccurred within a radius f 3 km and a perid f 18 d. In rder t determine the tempral pattern f dg cases in cmmunal areas, cases frm three cmmunal land blcks in which dg rabies had been frequently diagnsed were cunted fr every year. The blcks are shwn in Fig. 7 A as fllws: Blck 1: The areas f the middle eastern regin frm Chiduku t Ndanga Cmmunal Lands Blck 2: The cmmunal areas n the nrth-eastern brder with Mzambique Blck 3: The middle nrthern areas including Gkwe and surrunding cmmunal lands In additin, similar analyses fr dgs were dne fr Mutare city and surrunding areas and fr the Chipinge area, a cmmercial farming area with high dg rabies prevalence alng the eastern brder regin. Regressin analyses were carried ut between the ttal number f dg rabies vaccine dses administered per year and the ttal annual dg cases, and between vaccine dses administered and with cases lagged 1 year and with cases lagged 2 years. 2
J. BINGHAM et al. RESULTS Fig. 1 shws the twns and prvincial bundaries fr purpse f reference and Fig. 2 the species and species grups which were diagnsed with rabies. Mst rabies cases (45,7%) were diagnsed in dmestic dgs, fllwed, in rder f prevalence by jackals (25,2%) and cattle (18,9%). The breakdwn f the different species ccurring in the cmmercial farming, cmmunal and urban sectrs is given in Fig. 3. Prprtinately higher levels f dg rabies were reprted in the cmmunal and urban sectrs, while high levels f jackal and bvine rabies ccurred in cmmercial farming areas. Prevalence in dmestic dgs The number f cases f dg rabies diagnsed annually frm 195 t 1996 is shwn graphically in Fig. 4. Dg cases cnstituted the highest number f rabies cases every year except during years f jackal epidemics, which were 1966-1967,1971-1973, 1981 and 1993-1995. Rabies entered Zimbabwe alng the suthwestern brder and by 1954 was present in mst areas f the cuntry, except the large prtected (wildlife and frest) areas and the Gkwe regin. The reprted prevalence f the disease in dgs during the subsequent 1 years was relatively lw, the cases ccurring principally in the area west f Bulaway and alng the eastern brder. During the 196s mst f the cases ccurred in the eastern third f the cuntry, while during the 197s the suthern areas were als affected. In 1979 and 198, the prevalence increased markedly, the disease ccurring in mst regins except the large prtected areas. Since then the high prevalence and widespread ccurrence f Zambia Mzambique 1 kilmetres Kari Mashnaland Mha~gura West Mashnaland Central Chinhyi Hwange Gkwe Kadma Matabeleland Nrth Kwekwe Midlands Gweru Mutare Manicaland Btswana Plumtree Gwanda Matabeleland Suth Masving Masving Mwenezi Chiredzi Chipinge Mzambique FIG. 1 Map f Zimbabwe shwing the prvinces and the majr urban areas Suth Africa 3
Epidemilgy f rabies in Zimbabwe. 1 Dg 45,7% Dg 32,4% Cat 1,8% Human 1,7% Other wild... E :::'------I animal,3% Other wild camivre 2,7% ~~ ~ Human,3% Other dmestic animal 3,7% Jackal 25,2% FIG.2 Rabies cases in Zimbabwe frm 195-1996 shwing the prprtins f species and species classes Cmmercial farming sectr Dg 61,7% Jackal 36,7% dg rabies has persisted. Frm the mid-198s dg rabies ccurred with higher frequency in Gkwe Cmmunal Land, in which it had previusly been rare. This increase in the number f cases was assciated with the eradicatin f tsetse flies, the transmitters f trypansmiasis, which allwed human settlement in this area. Human 4,3% Seasnality The mnthly ccurrence f all the dg cases frm 195-1996 is shwn in Fig. 5. There was n prnunced seasnal variatin, althugh there were slightly mre cases diagnsed during the mnths f June t Nvember than in the remainder f the year. Gegraphical trends Cmmunal land sectr Bvine 16,9% Of the 4628 labratry-cnfirmed dg cases diagnsed frm 195-1996, 43 % riginated frm cmmercial farming areas, 34 % frm cmmunal areas, 22 % frm urban areas and,8 % frm prtected areas. Frm 1985-1996, when cmmunal area surveillance had imprved, 1 877 dgs were cnfirmed rabid and f these 3,7% riginated frm cmmercial farming areas, 55,6 % frm cmmunal areas, 13,4 % frm urban areas and less than,2 % frm prtected areas. The number f dg cases diagnsed annually in the different landuse sectrs is shwn in Fig. 6. Frm 195 until the early 198s mst cases f rabies in dgs were reprted frm the cmmercial farming sectr. During every year after 1984, the mst dg rabies cases were reprted frm the cmmunal sectr. Fig. 7 A and 7B shw the dg cases diagnsed in the cmmunal areas and cmmercial farming areas, Dg 72,4% Urban sectr Bvine 16% Jackal 12,% Human 2,9% FIG. 3 The prprtins f the different species diagnsed with rabies frm 195-1996 in the three main landuse sectrs in which rabies ccurred 4
J. BINGHAM et al. CI) 1,--------------------------------, 8 ~ 6 -... 1: 4 E :::l Z 2 195 1955 196 1965 197 1975 198 1985 199 1995 4,---------------------------------, 35... -- ----- ---.. ---- ---.. ------------------.. -.. --.. -- -- --.. -- ---- --- ---------.. ---- ------- --- 3 3: 25 n:i u 2 CI.g 15 1 5 O~--,_~~~--~--_r--._--,_--r r 195 1955 196 1965 197 1975 198 1985 199 1995 FIG. 4 Ttal number f rabies cases in animals (slid line) and dgs (dtted line) frm 195-1996 CI) 5,--------------------------------, 4 ~ 3 ' 1i 2 E :::l Z 1 JFMAMJJASONDJ Mnth FIG. 5 The mnths f the year in which all cases f rabies in dgs were diagnsed frm 195-1996 respectively frm 195-1996. The small number f psitive specimens received frm prtected areas came frm small parks r frest areas which were in clse prximity t cmmunal areas r cmmercial farmland, r frm near brder river crssings. CI) n:i U CI CI) n:i U CI 4 35 3 25 2 15 1 5 195 1955 196 1965 197 1975 198 1985 199 1995 4 35 3 25 2 15 1 Tempral trends The cuntrywide dg rabies prevalence by year is shwn in Fig. 4. Hwever, natinal figures bscure mre lcal trends, necessitating analysis f smaller areas. Fig. 8 shws the dg rabies prevalence by year fr three cmmunal land blcks and als fr Mutare city and Chipinge area (mainly cmmercial farmland), all areas where the number f psitive cases was high. Influence f rabies in jackals The epidemilgy f rabies in jackals (Canis adustus and Canis mesmelas) is described in detail elsewhere (Bingham et al. 1999). Hw des jackal rabies affect the patterns f the disease in dgs? The num- 195 1955 196 1965 197 1975 198 1985 199 1995 FIG. 6 Cases f rabies in dgs diagnsed annually in the different land use sectrs frm 195-1996 [cmmercial farmland (tp), cmmunal areas (middle) and urban areas (bttm)]. The slid line represents the ttal number f cases in dgs and the dtted line the cases in the respective landuse sectr bers f jackal-assciated and nn-jackal assciated cases are shwn in Fig. 9, the frmer being thse dg rabies cases fr which at least ne jackal rabies case ccurred within a radius f 3 km and a perid f 18 d_ The number f jackal-assciated cases never exceeded that f nn-jackal-assciated cases, even in years f high jackal rabies prevalence, althugh 5
Epidemilgy f rabies in Zimbabwe. 1 FIG. 7A Dg rabies in cmmunal areas shwing bundaries f cmmunal lands (internal lines) and lcatin f prtected areas (shaded regins), with the delimited blcks fr tempral analysis (dashed lines) during the early 198s and the 199s, when large utbreaks in jackals ccurred, jackal-assciated cases made up a large prprtin f the ttal dg cases. Overall, 21,2% f dg cases were assciated with jackal cases and 74,2 % with ther dg cases within 3 km and 18 d, while 18,1 % were nt assciated with cases in any ther species, 56,6% were assciated with dg cases in the absence f the disease in jackals and 3,5% were assciated with jackal cases in the absence f dg rabies cases. Jackalassciated cases accunted fr 25,7% f dg cases in cmmercial farming areas and 12,8 % f cases in cmmunal areas. Dg vaccinatin The vaccinatin trends f dgs during the perid under review are graphically cmpared t the ttal number f dg cases in Fig. 1. Dg vaccinatin cmmenced in 1951. In the early 196s vaccinatin levels declined, pssibly due t cmplacency caused by the lw numbers f cases diagnsed psitive (Fggin 1988). During the late 197s vaccinatin levels decreased markedly due t the escalatin f civil war, which adversely affected rural animal health prgrammes (Lawrence, Fggin & Nrval 198). After the cessatin f war and independence in 198, the number f dgs vaccinated against rabies increased again. The drp in vaccinatin levels seen after 199 was prbably related t declining Veterinary Department resurces and t the diversin f available resurces t ther disease prgrammes. There was a significant negative relatinship between natinal annual vaccine dses administered and cases lagged ne year (r=,35; P=,19), but 6
J. BINGHAM et al. FIG. 7B Dg rabies in cmmercial farmland shwing bundaries f cmmunal lands (internal lines) and lcatin f prtected areas (shaded regins) there was n significant relatinship with same-year cases nr with cases lagged 2 years. DISCUSSION Zimbabwe is divided int fur majr landuse categries: cmmercial farmland, cmmunal farmland, urban areas and prtected areas. Cmmercial farmland, which cnstitutes 43 % f the ttal land area, is mainly privately wned, the predminant activities being cmmercial crp and livestck prductin and game ranching. In recent histry cmmercial farmland has been wned predminantly by farmers f Eurpean descent wh have practised mdern farming techniques. Many f these farms have mderate t large labur frces, which reside n the prperties with their families. A small prprtin f this sectr als includes "small-scale" farming enterprises, wned by farmers f African descent. Since independence in 198 a certain amunt f cmmercial farmland has been acquired fr resettlement schemes and has been settled by families riginating frm ver-ppulated cmmunal areas. In 1986, resettled land amunted t almst 7% f ttal land area (16% the cmmercial farming land area) (Brks 199) and since then the resettlement prgramme has cntinued expanding. Human ppulatins vary frm lw in the extensive ranching areas in the suth, west and central regins, t mderate in the mre intensive crp farming areas in the nrth. Dgs densities are lw mainly because many cmmercial farmers d nt allw their labur frce t keep dgs (Brks 199). Cmmunal farming areas are settled by lw-incme families practising mainly subsistence agriculture using traditinal farming techniques. These areas, which cmprise 42% f the cuntry's surface area, 7
Epidemilgy f rabies in Zimbabwe. 1 (1) (.) '" OJ c (1) (.) '" OJ c 6,--------------------------------, 5...... - 4 3 2,~ }' -...- 1,"'\"'i";"...,. \, I " ',' -- ~-... :.:::..<::~_.\-\----/-.":"':.. \. -..!.--------\- / \ O~--------_.--------_.----------~ 198 1985 199 1995 6,--------------------------------, 5 195 1955 196 1965 197 1975 198 1985 199 1995 FIG.8 Numbers f dgs diagnsed per year in (tp) three cmmunalland blcks, as given in Fig. 7 A, frm 198-1996 (Blck 1: slid line; Blck 2: dashed line; Blck 3: dtted line) and (bttm) in and arund Mutare city (slid line) and in the Chipinge area (dtted line) frm 195-1996 25-,---------------------------------, 2....... ~ 15... N9.n.:j~!<~~J ~.? s.s.qt::i~t~.9... (.) '" OJ ~ 1 5-195 1955 196 1965 197 1975 198 1985 199 1995 FIG.9 Jackal-assciated (dtted line) and nn-jackal'assciated (slid line) rabies cases in dgs diagnsed each year frm 195-1996. Jackal-assciated cases are defined as thse with at least ne case f rabies in a jackal within a radius f 3 km and a perid f 18 d cntain 51,4 % f Zimbabwe's human ppulatin (Central Statistics Office 1994). Veterinary infrastructure histrically has been prly develped in the cmmunal areas: it was nt until after independence in 198 that the veterinary infrastructure was devel- (1) (.) '" OJ c 4 --,--------------------------------,- 8 G> is. 7 g C 6 g 5 ::: 4! -g 3 ~ c: 2.~ 35 3 25 2 15 1.... 5, ~ 1 ~... J '\,' -'/'" +---.-----.---,---.---.----,---.---.----r-- c 1~1~1~1~1~1ml~1~1~1~1~ FIG. 1 Annual number f cases f rabies in dgs in Zimbabwe frm 195-1996, shwing the number f dses f vaccine (per 1 peple) administered t dgs in each f the years ped by building animal health centres staffed by extensin persnnel. Prtected areas are specially designated areas fr the prtectin f habitats and include gvernment r parastatal-run natinal parks, frest land, safari areas and recreatinal parks. These areas cnsist mstly f marginal land unsuitable fr agriculture, but may supprt large ppulatins f wild animals, including jackals. Brks (199) fund that Zimbabwe had a ttal dg ppulatin f 1,3 millin in 1986 and the dg ppulatin grwth rate was estimated at 4,7% per annum. Mst f the dgs (71,3%) lived in the cmmunal areas, where the dg-t-human rati was 1 :4.5. Dg ppulatins had densities f between 1,4 and 6,7 dgs per km2, depending n the prvince. In a subsequent survey cmmunal area dgs had an average age f 2 years and 41,8 % were belw 1 year f age (Butler 1995). The average estimated dg density fr seven cmmunal lands was 21 dgs per km 2. Cmmunal area dgs live an almst entirely unrestricted life althugh very few are nt wned. Althugh the highest number f reprted dg rabies cases riginated frm the cmmercial farming areas during 195-1996, in the mre recent part f the study perid the majrity had been reprted frm the cmmunal areas. Since this apparent change in the relative prevalence within the landuse sectrs cincided with the imprvement f rabies surveillance in cmmunal areas, it is pssible that the earlier prevalence figures are nt a true reflectin f the prevailing situatin as it was then. Despite the imprvement in cmmunal area surveillance, it is still cnsidered inadequate, particularly in the mre remte regins where the large majrity f cases are prbably nt being reprted. Surveillance in the cmmercial and urban sectrs is unlikely t have changed significantly during the perid under review. Dg rabies, 8
J. BINGHAM et al. therefre, appears t have been maintained predminantly in the cmmunal areas. This is t be expected, given that abut 71,3% f dgs in Zimbabwe live in these areas (Brks 199). Rabies in dgs was mst frequently diagnsed in the large cmmunal land blcks with high human ppulatins. Cmmunal lands in the agriculturally marginal areas in the western, nrthern and suth-eastern regins f the cuntry, which d nt supprt dense human ppulatins, had fewer reprted cases. Small islated cmmunal areas als had few cases. It is cnsidered that this is related t the different cmmunal land dg ppulatin sizes; small islated ppulatins being unable t maintain rabies. Urban dg rabies des nt appear t be imprtant, except in the city f Mutare. The reasn fr the high frequency in Mutare cmpared t ther urban areas may be related t the clse assciatin f this city with susceptible dg ppulatins frm adjacent cmmunal areas (Fig. 7A and B). Dg cases in cmmercial farming areas (Fig. 7B) were mst frequent in the eastern regins. There was als a high density in the Mashnaland regin and sme f these cases were assciated with jackal epidemics. That large numbers f cases which are nt assciated with jackal rabies and ccurred in the cmmercial farming areas sme distance frm cmmunal areas indicates that these areas are prbably als capable f maintaining dg rabies. Examinatin f the gegraphical spread f rabies ver the different years f the study perid reveals n prnunced gegraphical pattern f disease mvement, except fr thse cases which were assciated with the large jackal epidemics. Hwever, the detectin rate f cases may have been inadequate t demnstrate such a pattern with accuracy. In areas where the dg rabies prevalence was high it was cyclical in frequency with perids f 4-7 years (Fig. 8). Interestingly, the cycles in the different blcks appear t be smewhat synchrnized, with high and lw prevalence perids ccurring cncurrently. It is pssible that these rabies cycles fllw natural dg ppulatin density fluctuatins. Vaccinatin levels and surveillance may als affect rabies prevalence, but these factrs are likely t affect the prevalence nly at a lcal level and nt the bserved majr tempral trends. T what extent is dg rabies influenced by rabies in ther vectr species, particularly jackals? Jackals cnstitute ver 25 % f diagnsed cases and are a majr vectr f the disease in the cmmercial farming sectr (Bingham et al. 1999). Hwever, jackalassciated cases, which are thse with at least ne jackal case ccurring within a radius f 3 km and a perid f 18 d, never exceeded nn-jackal-assciated cases, even in years f high jackal rabies preva- lence, althugh during the early 198s and the 199s, when large jackal utbreaks ccurred, jackalassciated cases made up a large prprtin f the ttal dg cases. Althugh this assciatin des nt prve that jackals were respnsible fr transmissin t jackal-assciated dg cases, it des give sme indicatin f hw much influence jackal rabies may have had n the prevalence f the disease in dgs. In mst years this appears t be small in the cmmercial farming areas and prbably insignificant in the cmmunal areas. The numbers cnstituting ther carnivre species, such as dmestic cats (Felis dmestica), mngses f varius species (Family Herpestidae), hney badgers (Mellivra capen sis) and civets (Civettictis civetta), were cnsidered t lw t have had any significant effect n dg rabies epidemilgy, and may rather have been spillver frm dgs and jackals. It is evident that dgs are reservir hsts f rabies and are capable f maintaining the disease fr lng perids withut the presence f rabies in ther species. Nevertheless, at least ne utbreak in dgs was initiated by jackals. This ccurred in the Hurungwe area in 1982 after the large jackal epidemic f the early 198s in Mashnaland (Fggin 1988; Kennedy 1988). The vaccinatin level at which utbreaks f rabies will be prevented is generally regard t be arund 7 % (Cleman & Dye 1996). Brks (199) estimated that 4% f dgs in Zimbabwe were vaccinated in 1986. Frm Fig. 1 it wuld appear that the 1986 vaccinatin level (as dses per 1 peple) may have been exceeded nly during the late 196s and early 197s and frm 1987-1991, while lwer levels were reprted in ther years. Extraplating frm 4% vaccinatin cverage in 1986, vaccinatin levels may therefre have varied between abut 1% and 5 %. The significant negative crrelatin between dgs vaccinated and dg cases implies that these past levels f ppulatin immunity are likely t have had, nt surprisingly, sme influence n disease levels. Hwever, these vaccinatin levels are clearly inadequate in cntrlling dg rabies, as evidenced by the high rabies prevalence. Dg rabies vaccinatin levels are expressed in dses per 1 peple because n regular data n dg ppulatin numbers are available. It is assumed that the dg ppulatin is directly prprtinal t the natinal human ppulatin. This is cnsidered justified as dgs in Zimbabwe appear t be entirely dependent n humans fr their resurce requirements and the number f truly unwned dgs appears t be lw (Brks 199; Butler 1995). The expressin f dg vaccinatin levels in dses per 1 peple als assumes that peples' dg keeping habits are cnstant frm year t year. Because the dg:human rati is different in the different land use sectrs (Brks 199), this rati will be influenced by demgraphic changes between land use sectrs. Hwever, analysis f changes in human ppulatin demgraphy as 9
Epidemilgy f rabies in Zimbabwe. 1 it may relate t dg husbandry is beynd the scpe f this study. The use f natinal figures fr vaccine dses administered and case numbers may bscure mre significant crrelatins present in lcal areas. It wuld be useful t cmpare dg rabies cases and vaccinatin figures fr limited areas. Such a study, using prvincial data, has been carried ut by Fggin (1988). Hwever, mre accurate answers culd be fund by using areas f unifrm sci-eclgical attributes, such as individual cmmunal area blcks r urban areas. Unfrtunately vaccinatin figures fr specific areas were nt readily available and such analysis is beynd the scpe f this study. Given accurate and lng-term data n lcal vaccinatin levels, hwever, this analysis wuld be an imprtant study t determine the effect f vaccinatin n the prevalence f rabies and n determining the vaccinatin levels required t bring abut cntrl f rabies. This study characterized sme f the epidemilgical features f dmestic dg rabies in Zimbabwe. Fr the cntrl f dg rabies, it will be imprtant t increase the vaccinatin cverage f dgs, particularly in the large cmmunal area blcks, where rabies appears t be maintained. Effective vaccinatin campaign strategies need t be develped in rder t raise this cverage, as cnventinal vaccinatin strategies clearly have nt succeeded in achieving adequate cntrl. ACKNOWLEDGEMENTS Assistance with the use f gegraphical sftware was gratefully received frm Russel Kruska f the Internatinal Livestck Research Institute, Kenya and Chris Ncube and Chris Karunkm bth f the Central Veterinary Labratry, Harare. Theresa Munymbwe (Central Veterinary Labratry, Harare) helped with statistical analysis. Dr Brian Perry is thanked fr his criticism f the manuscript. REFERENCES BROOKS, R. 199. Survey f the dg ppulatin f Zimbabwe and its level f rabies vaccinatin. The Veterinary Recrd, 127:592-596. BINGHAM, J., FOGGIN, C.M., WANDELER, A. I. & HILL, F.w.G. Epidemilgy f rabies in Zimbabwe. 2. Rabies in jackals (Canis adustus and Canis mesmelas). Ondersteprt Jurnal f Veterinary Research, 66:11-23. BUTLER, J.RA 1995. A survey f cmmunal land dgs in Zimbabwe with reference t imprving rabies vaccinatin cverage, in Prceedings f the Third Internatinal Cnference f the Suthern and Eastern African Rabies Grup, Harare, Zimbabwe, 7-9 March 1995, edited by J. Bingham, G.C. Bishp & AA King. Lyn : Fndatin Marcel Merieux: 81-94. CENTRAL STATISTICS OFFICE. 1985. 1982 Ppulatin Census. Main demgraphic features f the ppulatin f Zimbabwe: An advance reprt based n a ten percent sample. Harare: Central Statistics Office. CENTRAL STATISTICS OFFICE. 1994. Census 1992: Zimbabwe Natinal Reprt. Harare: Central Statistics Office. COLEMAN, P.G. & DYE, C. 1996. Immunizatin cverage required t prevent utbreaks f dg rabies. Vaccine, 14:185-186. DEAN, D.J., ABELSETH, M.K. & ATANASIU, P. 1996. The flurescent antibdy test, in Labratry Techniques in Rabies, 4th ed., edited by F.-X. Meslin, M.M. Kaplan & H. Kprwski. Geneva: WHO. FOGGIN, C.M. 1988. Rabies and rabies-related viruses in Zimbabwe: Histrical, virlgical and eclgical aspects. PhD. thesis, University f Zimbabwe. KENNEDY, D.J. 1988. An utbreak f rabies in nrth-western Zimbabwe 198 t 1983. The Veterinary Recrd, 122:129-133. KOPROWSKI, H. 1996. The muse inculatin test, in Labratry Techniques in Rabies, 4th ed., edited by F.-X. Meslin, M.M. Kaplan & H. Kprwski. Geneva: WHO. LAWRENCE, JA, FOGGIN, C.M. & NORVAL, RAI. 198. The effects f war n the cntrl f disease f livestck in Rhdesia (Zimbabwe). The Veterinary Recrd, 17:82-85. SWANEPOEL, R., BARNARD, B.J.H., MEREDITH, C.D., BISHOp, G., BROCKNER, FOGGIN, C.M. AND HOBSCHLE, O.J.B. 1993. Rabies in suthern Africa. Ondersteprt Jurnal f Veterinary Research, 6:325-346. 1