Resistance to ectoparasiticides as a result of malpractices by farmers. Dr Tom Strydom Malelane Research Unit

Transcription

1 Resistance to ectoparasiticides as a result of malpractices by farmers Dr Tom Strydom Malelane Research Unit

2 One host tick resistance to acaricides increased to alarming rates over past 20 years Reasons: Lack of new groups of actives Farmers buying stud ticks with stud animals movement of cattle with resistant ticks Over-use of existing actives Malpractices from farmers Consequences: Tick resistance a reality Lack of sufficient tick control with production losses Increased incidents of tick borne diseases Redwater (babesioses) Unsafe meat to customers 2

3 R. boophilus spp distribution

4 R. boophilus microplus distribution

5 R. boophilus decoloratus distribution

6 Tick resistance stats 2005 Percentage Rhipicephalus Boophilus spp. samples showing resistance - control with pyrethroids, OP s and amidines less than 90% 80% One active 57% Two actives 51% Three actives 6

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9 History of Resistance Arsenic : 1941 BHC and Toxaphene : 1953 DDT : 1956 Pyrethrin : 1959 Organophosphate and Carbamate : 1967 Pyrethroid : 1981 Amitraz :

10 Groups of actives Carbamates Carbaryl Organophosphates Chlorfenvinphos Diazinon Dichlorphos Triazophos Propetamphos Pyrethroids Flumethrin Deltamethrin Alphamethrin Cypermethrin Cyalothrin Cyfluthrin Formamidines / Amidines 10

11 Pour-On Formulations Pyrethroid: eg. Drastic Deadline - Bayer Pyrethroid + Amidine: eg. Delete All - MSD Pyrethroid + OP: eg. Pouracide - Zoetis 11

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13 Systemic Products Macrocyclic Lactone Ivermectin Doramectin Moxidectin Abamectin Eprinomectin Acaricide Growth Regulator Fluazuron 13

14 Malpractices of farmers Making home made pour-on formulations Treatment with agro-chemical products Using unregistered products on animals Off-label use of registered products game industry Get advice from neighbour farmer what to do 14

15 Home-made pour-on Practice: Water soluble agro-chemical pyrethroid mixed with oil - Sunflower oil, horticultural oil, tractor oil, diesel Applied as a pour-on along the backline of animal Facts: Water soluble concentrate alone does not go in suspension with oil Ticks are not exposed to correct concentrations of active ingredient Pyrethroids are known to act as endocrine disruptors in mammals (Kim et al., 2005; Perry et al.,2007; Sun et al., 2007; Wang et al., 2007; Zhang et al.) 15

16 Consequences of home brews Parasites exposed to low and higher than registered concentrations of active ingredient develop resistance No tissue withdrawal time available for home brew Severe irritation to animal from pyrethroid Exposure of breeding animals to excessive quantities of pyrethroids (more than what it is registered for) causes lower fertility in male animals. (Perry, M.J., Venners, S.A., Barr, D.B. and Xu, X Environmental pyrethroid and organophosphorus insecticide exposures and sperm concentration. Reprod. Tox. 23: ) 16

17 Pyrethroid + sunflower oil Immediately after adding 10 min after vigorous mixing 17

18 Pyrethroid + tractor oil Immediately after adding 10 min after vigorous mixing 18

19 Irritation of pour-on to animal 19

20 Agro-chemical products Practice: Treatment of animals orally with agro-chemically registered fipronil Fact: Veterinary products containing fipronil act by killing parasites on contact Trials: 1) 79% fipronil applied externally to skins of rats only 1 % fipronil taken up into body 2) Goats and rats treated orally 15 to 33 % and 30 to 50% fipronil absorbed by the bodies of these animals respectively, mainly fat tissue Rats treated at high doses developed thyroid cancer. FDA classified fipronil as a possible human carcinogen Long term treatment of rats affected their ability to produce offspring (Ref: National pesticide information: Oregon State University) 20

21 Consequence of use of agro-chemicals No withdrawal time for active ingredient from animal tissue Unsafe meat to customers Fipronil has not been registered as a product to control ticks because of cross resistance with dieldrin resistant ticks. Majority of fipronil taken up by the body is excreted in the faeces and urine. Possible poisoning of birds and fish. The registration of future possible veterinary products compromised? 21

22 Treatment with unregistered products Practice: Fact: Farmers believe claims by non-pharmaceutical companies that natural products are effective and registered for tick control Farmers treating cattle with dettol or turpentine by intra-muscular injection to control ticks If the method of action of the product on the target parasites is unknown, how can it kill the parasite? Veterinary medicinal products are registered with Act 36 of 1947 or Act 101 of 1965 who will allocate a G or S number respectively to the product Anti-parasitics are tested following international accepted guidelines - WAAVP or VICH guidelines Consequence: No information of the effect of these products on the health of the animal or humans No information on interaction with other registered products Lack of effective tick control and lack of production 22

23 Off-label use of registered products Practice: Fact: Game farmers control ecto- and endoparasites in game on game ranches and using unregistered products Incorrect application and under-dosing of animals No information on efficacy data No information on withdrawal times of active ingredients No information on safety of actives for target species Consequence: Ineffective administration of anti-parasitic and under-dosing may contribute to development of parasite resistance Animals do not have any natural resistance to parasites 23

24 Haemonchus contortus (wireworm) in sable 24

25 Ear damage due to R. appendiculatus in eland 25

26 Accepting advice from other farmers? Every farm is unique Habitat for parasites may differ Parasites species may differ Resistance status of parasites differ Disease situation on each farm differ (tick-borne diseases) Parasite management is a science Get professional advice Pharmaceutical companies cannot take responsibility for mismanagement Neither can we take responsibility for lack of knowledge! 26

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