WO2006082213A1

WO2006082213A1 - Compositions for controlling parasites comprising synergic combination of amitraz and chlorpyrifos

Info

Publication number: WO2006082213A1
Application number: PCT/EP2006/050614
Authority: WO
Inventors: Hyun Sun Cho; Edival Santos
Original assignee: Intervet International B.V.
Priority date: 2005-02-03
Filing date: 2006-02-02
Publication date: 2006-08-10
Also published as: ZA200705786B; AR053804A1; BRPI0606794A2

Abstract

The present invention relates to compositions for controlling parasites, comprising a combination of amitraz and chlorpyrifos and the use of such compositions in the preparation of a medicament for controlling acarine parasites on animals.

Description

COMPOSITIONS FOR CONTROLLING PARASITES COMPRISING SYNERGIC COMBINATION OF AMITRAZ AND CHLORPYRIFOS

The present invention relates to compositions for controlling parasites and the use of such compositions in the preparation of a medicament for controlling acarine parasites.

Ticks are important blood feeding arthropod parasites that belong together with mites (Family: Psoroptidae) to the order Acarina (acarine parasites). There are two well- established families of ticks, the Ixodidae (hard ticks), and Argasidae (soft ticks). The Ixodidae species is of most economic importance and include the important species Boophilus spp., Rhipicephalus spp, Ixodes spp, Hyalomma spp., Amblyomma sp p. and Dermacentor spp.

The cattle tick Boophilus microplus is the most economically important bovine parasite in Brazil, causing economic losses in the order of US$ 2 billion each year

(Grisi et al., 2002). Furlong et al. (2004) assert that this parasite causes severe damage by its direct action, provoking anemia, myiasis predisposition, leather depreciation, as well as by its indirect action, characterized by haemoparasites inoculation and costs from chemical treatment. Bovine development and production are highly damaged by B. microplus, and its control varies, according to climatic conditions (Oliveira et al., 1973) and breed of the animals (Veπssimo, 1990).

Each of the five Boophilus spp. has a one-host life cycle that may be completed in 3 to 4 weeks and results in a heavy tick burden. Treatment of hosts with acaricides to kill attached larvae, nymphs, and adults of ticks has been the most widely used control method. Chemical products are the major way of control of ticks. In the first half of the 20^th century, the main acaricide was arsenic trioxide. Subsequently, organochlorines, organophosphates, carbamates, amidines, pyrethroids, and avermectins have been used in different parts of the world. However, its frequent utilization led to resistant parasite population selection. Acaricide products resistance is widespread in the world and contemplates a lot of chemical products (Kunz & Kemp, 1994).

Thus, acaricide products inefficacy is very common. The first case of organophosphate resistant Boophilus microplus in Brazil was reported in Santa

Ambrosia, Rio Grande do SuI, in 1963 (Wharton & Roulston, 1975), and its isolated use for ticks control was stopped in 1976 in the south of Brazil. In relation to synthetic pyrethroids, resistance was firstly identified in Sao Paulo (Pereira & Lucas, 1987), Rio de Janeiro (Leite, 1988) and Rio Grande do SuI (Laranja et al., 1989) states. Strains of ticks were shown resistant to amitraz in Rio de Janeiro state (Gloria et al., 1993; Flausino et al., 1995) and Rio Grande do SuI (Martins et al., 1995; Vargas et al., 2003). In the macrocyclic lactones group, Martins and Furlong (2001) have already verified bad efficacy of doramectin, moxidectin and ivermectin against Boophilus microplus.

Chemical parasiticides are a non renewable resource, and as resistance is installed, it looses its utility forever, as the phenomenon is unchangeable. So, prudent use is recommended to take advantage of the products for a longer time. Different drugs combination is a suggested strategy to overcome resistance (FAO, 2003). In this kind of treatment, ticks are exposed to more than one active. A necessary condition for drugs combination efficacy is that there is no crossed resistance between the actives, i.e., that the action mechanisms and metabolic ways are different (Kunz & Kemp,

1994).

However, to obtain an acaricidal composition which shows no cross-resistance with existing insecticidal and acaricidal agents, has no toxicity problems and has little negative impact on the environment, is extremely difficult. Therefore, a means to delay or prevent the development of resistant strains of pest species is always being sought. In order to apply an effective agent as long as possible, a rotational application of agents with different mechanisms of action is adopted for good pest management practice.

However, this approach does not necessarily give satisfactory pest control. Therefore, after a resistance problem has occurred, a countermeasure to resistance by combining insecticidal and acaricidal agents has been studied. However, a high synergistic action has not always been found.

Therefore, it is an object of this invention to provide an acaricidal composition which demonstrates a high controlling effect even against ticks of Boophilus sp., which acquired resistance against amitraz and/or certain organophosphate compounds.

The invention thus relates to a veterinary composition for the control of acarine parasites on animals comprising as active ingredient a synergistic combination of amitraz and chlorpyrifos. Amitraz is a known insecticide and acaricide and is the common name for N,N-bis (2,4-xylyliminomethyl)methylamine. Amitraz presents adrenergic activity by monoaminooxidasis inhibition, leading to noradrenalin and serotonin at central nervous system.

Organophosphate compounds are for a long time used as insecticide and pesticide for plants and livestock as well as anthelmintic for animals. The acaricidal action of organophosphate compounds is due to the inhibition of the enzyme acetylcholinesterase, resulting in the accumulation of the neurotransmitter acetylcholine, at nerve endings. This results in excessive transmission of nerve impulses, which causes mortality in the target pest.

Examples of organophosphate compounds are Profenofos, Dichlorvos, Fenamiphos, Fenitrothion, EPN , Diazinon Chlorpyrifos, Acephate, Prothiofos, Fosthiazate,

Cadusafos, Dislufoton Isoxathion, Isofenphos, Ethion (I), Etrimfos, Quinalphos,

Dimethylvinphos, Dimethoate, Sulprofos.Thiometon, Vamidothion, Pyraclofos

Pyridaphenthion, Pirimiphos-methyJ Propaphos, Phosalone, Formothion, Malathion,

Tetrachlovinphos, Chlorfenvinphos, Cyanophos ,Trichlorfon, Methidathion, Phenthoate, Dimethylethylsulfilisopropyl thiophosphate (common name: ESP),

Azinphos-methyl, Fenthion, Heptenophos, Methamidphos, Paration.

Especially preferred is Chlorpyrifos. The chemical name of chlorpyrifos is 0,0 - Diethyl-O-S.S.Θ-trichloro^-pyridylphosphorothioate.

For the preparation of the composition of the invention, it is suitable to formulate the composition e.g. as a wettable powder, aqueous concentrate, emulsifiable concentrate (EC) , liquid concentrate, sol (flowable agent), powder, aerosol, or the like, by conventional methods such as admixing the compounds separately with a suitable carrier and auxilliaries, such as emulsifiers, dispersants, stabilizers, suspending agents, penetrants, and the like and than combine the formulations for direct administration to the animal, optionally after diluting.

Amitraz is preferably formulated as wettable powder and the organophosphate compound (e.g. chlorpyrifos) as emulsifiable concentrate and the final composition is mixed with water immediately before application to the animal. . Alternatively amitraz and the organophosphate compound (e.g. chlorpyrifos) are formulated as wettable powder and mixed with water immediately before application to the animal to form the final formulation.

An emulsifiable concentrate comprises the active ingredient dissolved in water- immiscible solvent which is formed into an emulsion with water in the presence of an emulsifying agent.

A dispersible or wettable powder usually comprises the active ingredients in admixture with a suitable surfactant and an inert powder diluent such as china clay.

Suitable formulations are usually composed of 0.001 to 99 parts by weight, preferably 0.01 to 95 parts by weight, more preferably 0.01 to 80 parts by weight of an active ingredient and 1 to 99.999 parts by weight, preferably 5 to 99.99 parts by weight, more preferably 20 to 99.99 parts by weight of suitable carrier and auxilliaries.

The composition may be formulated for application by a particular method, for example spraying, in which case the formulation may be presented as an aerosol using a liquid or gas propellent.

As the suitable carrier and auxilliaries, there may be mentioned carriers, emulsifiers, suspending agents, dispersants, extenders, penetrating agents, wetting agents, thickeners, defoaming agents, stabilizers or antifreezing agents. They may be added as the case requires.

The ratio of the organophosphate compound to amitraz in the acaricidal composition of the invention is about 1 weight part of the amitraz to about 0.5-10 weight parts, preferably about 1-5 weight parts, of the organophosphate compound

In commercially useful formulations, the composition of the invention may also be present in a mixture with other active agents, for example various insecticidal, or acaricidal agents in order to expand its applicability. Such pesticide compounds may include active ingredients which have an immediate effect, rather than the relatively slowly acting IGR. Other ingredients that may be included in the composition of the current invention are pesticidial active ingredients e.g. synthetic pyrethroids ( e.g permethrin, deltamethrin, cypermethrin, lambdacyhalothrin, fenvalerate, resmethrin, tralomethrin), acetylcholinesterase Inhibitors as carbamates (e.g. carbaryl, benziocarb, fenoxycarb, proxopur), acetylcholine mimics (e.g. nicotine, imidacloprid), GABA Antagonists (e.g. fipronil).

In another embodiment the invention relates to the use of the composition according to the invention for the manufacture of a veterinary medicament for the control of parasites, especially parasitic acarid- infestations on host animals.

In example 3 the therapeutic efficacy and residual period of the composition according to the invention was evaluated, after spray administration of the water- diluted composition manufactured according to example 1 to Boophilus microplus infested cattle in different Brazilian regions. These experiments conducted in cattle demonstrated that the association showed a higher efficacy against ticks of Boophilus sp., when compared to the efficacy of the separate compounds.

The compositions of the invention are intended for use for controlling a parasitic acarid infestation. The term "controlling a parasitic acarid infestation" refers to preventing, reducing or eliminating an infestation by such parasites on animals preferably by killing the insects and/ or acarids within hours or days. The term "parasitic acarid" refers to ectoparasites e.g. acarine pests that commonly infest or infect animals. Examples of such ectoparasites include the egg, larval, pupal, nymphal and adult stages of mites and ticks.

Various techniques for administration to the animal are available. When pasture or lot conditions and management systems are favourable, animals may be dipped in a bath with water diluted acaricide. Dipping vats are constructed so that animals are thoroughly immersed in the vat fluid, and the liquid that drains from the animals, returns to the vat.

Aqueous emulsions or suspensions may also be applied by spraying. Sprayers are generally portable and may be hand- or motor-driven, and only enough acaricide to treat a specific number of animals needs be prepared. Hand application of insecticides as washes, ointments, dusts, mist sprays, spray foams, aerosols, etc, can also be done.

Ear ticks may be controlled by insecticides applied directly into the ears. Other treatments applied by hand include the pour-on method, which consists of applying a water-diluted, emulsifiable concentrate or a ready-to-use formulation. The liquid should be poured along the backline from the shoulders to the hip bones. The spot-on treatment method consists of applying a small volume of concentrated insecticide to a single spot on the animal's back

The compositions of the invention may be employed in many forms and are often most conveniently prepared in aqueous form immediately prior to use.

One method of preparing such a composition is referred to as "tank mixing" in which the ingredients in their commercially available form are mixed together by the user in a quantity of water.

In addition to tank mixing immediately prior to use the compositions containing amitraz and the organophosphate may be formulated into a more concentrated primary composition which is diluted with water or other diluent before use. Such compositions may comprise a surface active agent in addition to the active ingredients.

It can be a dispersable solution which comprises the active ingredient dissolved in a water-miscible solvent with the addition of a disperging agent. Alternatively it can comprise the ingredients in the form of a finely ground powder in association with a disperging agent and intimately mixed with water

For preparation of the final formulation for administration to the animal the active ingredients are diluted in water. The final concentration of amitraz and the organophosphate in the diluted ready to use formulation is between 50 ppm and 800 ppm. In a preferred embodiment the diluted composition contains 250 ppm amitraz and 500 ppm chlorpyrifos. The diluted composition is preferably administered to the animal by spray or dip. Preferably 5 liters of the diluted composition are applied to each animal.

Preferably, the active ingredients are formulated separately and they are mixed together immediately before administration to the animal.

Preferably the host animal is a bovine. The method may be also be used to treat or control parasites on a variety of other animals including livestock animals as sheep, deer, goats, pigs, and companion animals as horses, dogs and cats. The composition according to the invention is used to control acarine parasites on animals, especially for the control of ticks, especially Boophilus sp.. The composition of the invention is further illustrated in the following examples.

References

FAO. Resistencia a los antiparasitarios: estado actual con enfasis en America Latina. Roma: FAO, Salud Animal, p. 1-52, 2003.

FLAUSINO, J.R.N.; GOMES, CCG. ; GRISI, L. Avaliagao da resistencia do carrapato B. microplus a piretrόides no municipio de Seropedica, Rio de Janeiro. In: Seminario Brasileiro de Parasitologia Veterinaria, 8. 1995. Campo Grande. Anais...Campo Grande. 1995. p. 45. FURLONG, J.; MARTINS, J.R.S.;PRATA, M.C.A. Controle estrategico do carrapato dos bovinos. A Hora Veterinaria , ano 23, n. 137, p. 53-56, 2004.

GLORIA, M.A.; FLAUSINO, J.R.N.; GRISI, L. Resistencia do Boophilus microplus ao amitraz no estado do Rio de Janeiro, com base em testes de imersao de femeas ingurgitadas. In: Seminario Bras, de Parasitologia Veterinaria, 7., 1993, Londrina. Anais... Londrina. 1993. p. A7.

GRISI, L. et al. lmpacto econδmico das principals ectoparasitoses em bovinos no Brasil. A Hora Veterinaria , ano 21, n. 125, p. 8-10, 2002.

KUNZ, E. S.; KEMP, H. D. Insecticides and acaricides: resistance and environmental impact. Rev. Sci. Tech. Off. Int. Epiz. v.13, .4, p.1249-1286, 1994. LARANJA, R.J.; MARTINS, J. R.; CERESERV, H.; CORREA, B.L.; FERRAZ, C

Identificaςao de uma estirpe de Boophilus microplus resistente a carrapaticidas piretrόides no Estado do Rio Grande do SuI. In: Seminario Brasileiro de Parasitologia

Veterinaria, Bage, 1989, Bage. Anais...1989. p.83.

LEITE, CL. Boophilus microplus (can.1887); Susceptibilidade, uso atual e retrospectivo de carrapaticida em propriedades das regiδes fisiogeograficas da baixada do grande-Rio e Rio de Janeiro, uma abordagem epidemiolόgica. Rio de

Janeiro. UFRRJ. 1988. 122p. Tese (Doutorado). Universidade Federal Rural do Rio de Janeiro. 1988.

MARTINS, J. R.; FURLONG, J. Avermectin resistance of the cattle tick Boophilus microplus in Brazil. Veterinary Record, v. 149, n. 2, p. 64, 2001.

MARTINS, J.R.S. CORREA, B.L.; CERESER, V.H.; ARTECHE, C.C.P.A. Situation report on resistance to acaricides by the cattle tick Boophilus microplus in the state of Rio Grande do SuI, southern Brazil. In: Seminario International de Parasitologia Animal, 3. Anais... Acapulco, Mexico, 1995. OLIVEIRA, G.P.; PAULA COSTA, R.; MENEGUELI, CA. MELLO, R.P. Estudo ecolόgico da fase nao parasitaria do Boophilus microplus (Canestrini, 1889) (Acarina: Ixodidae) no Rio de Janeiro. Arquivos da Universidade Federal do Rio de Janeiro, v.4, n.1 , p. 1-10, 1974. PEREIRA, M. C; LUCAS, R. Estudos in vitro da eficiencia de carrapaticidas em linhagem de Boophilus microplus proveniente de Jacaref, SP, Brasil. Rev. Fac. Med. Vet. Zoo. USP., v.24, n.1, p. 7-11 , 1987.

ROULSTON, W.J.; STONE, B.F.; WILSON, J.T.; WHITE, LT. Chemical control of an organophosphorus and carbamate-resistant strain of Boophilus microplus (Can.) from Queensland. Bulletin of Entomology Research., v.58, p.379-392, 1968.

VARGAS, M.S.; CESPEDES, N.S.; SANCHES, H. F.; MARTINS, J.R.; CESPEDES, C.O.C.. Avaliagao in vitro de uma cepa de campo de Boophilus microplus (Acari: Ixodidae) resistente a amitraz. Ciencia Rural, v.33, n.4, p. 737-742, 2003. VERiSSIMO, CJ. Estudo da resistencia e susceptibilidade do carrapato bovino (Boophilus microplus) em rebanho mestiςo. Jaboticabal, 1990. 163p. Dissertagao (Mestrado em Zootecnia, Area de Concentragao em Produgao Animal), 1990. WHARTON, R.H.; ROULSTON, W.J. Acaricide resistance in Boophilus microplus in Australia. Hemoparasite Workshop. CaIi, Colombia. Centra International de Agricultura Tropical. 1975. WHARTON, R.H.; ROULSTON, W.J.; UTECH, K.B.W.; KERR, J. D. Assessment of the efficiency of acaricides and their mode of application against the cattle tick Boophilus microplus. Australian Journal of Agriculture Research, v.21 , p.985-1006, 1970.

EXAMPLES:

Example 1 : Preparation of the composition amitraz wettable powder + chlopyrifos EC

1) Amitraz wettable powder: Composition for 10O g:

Amitaz technical 50.00Og

Paraformaldehyde 3.00 g

Cresol formaldehyde sulfonate condensate 10.00 g

Aerosol OT-B 1.00 g Amorphous alumina silicate 19.0O g

Precipitated calcium carbonate up to 100.00 g

2) Chlorpyrifos emulsifiable concentrate (EC) Composition for 100 ml:

Chlorpyrifos 50.00 g

Calcium phenylsulpfonate 3.5O g

*Nonil phenol 6 EO (etoxylated) 6.75 g

**Ester polyglycolic of fatty acid 36 EO (etoxylated) 3.25 g

Soybean oil epoxylated LOO g

Butyl hydroxytoluen 0.01O g

Solvesso 150 44.040 g

*Brand name: Renex 60 (from Oxiteno)

**Brand name: Surfom 400 (from Oxiteno)

For preparation of the final formulation for administration to the animal the active ingredients are diluted in water. The two active ingredients are formulated separately and they are mixed just before use.

To get 20 liter of the diluted composition containing amitraz 250 ppm + chlorpyrifos 500 ppm in water, the amount of each formulation is: 10 g of amitraz wp and 20 ml_ of chlorpyrifos EC. Then it is administrated over the animal by spraying on or dip. Example 2: Preparation of the composition amitraz wp + chlopyrifos wettable powder

1 ) Amitraz wettable powder (wp): Composition for 100 g:

Amitaz technical 50.0Og

Paraformaldehyde 3.00 g

Cresol formaldehyde sulfonate condensate 10.00 g

Aerosol OT-B . 1 0O g Amorphous alumina silicate 19.0O g

Precipitated calcium carbonate up to 100.00 g

2) Chlorpyrifos wettable powder (wp): Composition for 100 g

Chlorpyrifos 50.00 g

Cresol formaldehyde sulfonate condensate** 10.00 g

Aerosol OT-B* 1.00 g

Starch up to 100.0O g

*Aerosol OT-B is ducosate sodium which is an anionic surfactant ** suspending agent.

To get 20 liter of the diluted composition containing amitraz 250 ppm + chlorpyrifos 500 ppm in water, the amount of each formulation is: 10 g of amitraz wp and 20 g of chlorpyrifos wp.

Example 3: Efficacy of amitraz + chlorpyrifos composition against tick infestation of cattle

Material and methods: Six experiments were conducted to evaluate the therapeutic efficacy and residual period of the amitraz + chlorpyrifos association prepared according to example 1. In all of them, the same methodology was used, as described below.

Three counts of ticks between 4.5 and 8.0 mm of diameter on the left side of naturally infested bovine were performed on three consecutive days. The animals were grouped by the means of the counts, constituting groups of 10 animals with similar average number of ticks (Wharton et al., 1970). Treatments were randomly attributed to the groups, with one kept as control, without any administration of tickicide product.

The treatments for each experiment are listed on Table 1. In all the cases, the bovine was sprayed with the product after its dilution, in a quantity of at least 5 liters per animal.

Table 1 : Description of the experiments, describing tested products and sites of execution.

Experiment Local Treatments (dilution)

Amitraz (250 ppm) + chlorpyrifos (500 ppm)

Pindamonhangaba,

I Chorpyrifos (500 ppm) SP

Amitraz (250 ppm)

Amitraz (250 ppm) + chlorpyrifos (500 ppm)

H Formiga, MG

Amitraz (250 ppm)

Amitraz (250 ppm) + chlorpyrifos (500 ppm)

III Formiga, MG

Amitraz (250 ppm)

Pindamonhangaba, Amitraz (250 ppm) + chlorpyrifos (500 ppm)

IV

SP Amitraz (250 ppm)

Amitraz (250 ppm) + chlorpyrifos (500 ppm)

V Cassia, MG Flumethrin (30 ppm) + coumaphos (400 ppm)

Amitraz (250 ppm)

Amitraz (250 ppm) + chlorpyrifos (500 ppm)

Vl Cassia, MG

Cypermethrin (80 ppm) + ethion (600 ppm) For the products tickicide effect estimative, new counts were done on days +1 , +3, +7, post treatment and then weekly, until significant efficacy could be perceived. Efficacy was calculated by the methodology proposed by Roulston et al. (1968), considering geometric means of the counts of each group: Efficacy = 100 x 1 - (Ta x Cb) / (Tb x Ca)

Ta - mean count in treatment group on a specific day Tb - mean count in treatment group on day zero Ca - mean count in control group on a specific day Cb - mean count in treatment group on day zero (day zero was considered as the average count of the three previous days).

Statistical analysis was conducted after data logarithm transformation (Little & Hills, 1978), applying F test, and comparing the means with Tukey test. Ticks counts and efficacy values of treated and control animals in Experiments I, II, III, IV, V and Vl are shown in Table 2.

Results and Discussion: Geometric means of left side sited 4.5 to 8 mm Boophilus microplus female counts in all the experiments, as well as efficacy perceptual of the evaluated products, are presented on Table 2. Efficacy values are illustrated on Graph 1.

Comparison of efficacy of the association and the isolated actives

In experiment 1 , the efficacy of the association was compared to the efficacy of the isolated actives. Ticks counts in chlorpyrifos + amitraz treated animals differed from the control group from day + 1 to day +21 post treatment. Expressive efficacy of isolated chlorpyrifos was seen only until day +7. Amitraz presented almost no efficacy, and the counts in this group didn't differ from control group from day + 14. Amitraz results were very poor, making evident the occurrence of resistance against this active. Thus, the association performance was highly better than when the actives were administered at isolated form.

The association was compared to amitraz in three experiments (II, III and IV). In all of them, ticks counts for association treated animals differed from control from day +1 to day +28 post treatment, reflecting its expressive effectiveness. Statistical difference between the association and amitraz treatments is shown on days +21 (Exp II), +7 and +14 (Exp Il and IV) and +3 (Exp. IV). Taking these experiments together, it can be presumed that amitraz resistant tick strains are present. However, when the active is associated to chlopyrifos, good control could be obtained.

Comparison between chlorpyrifos + amitraz and some pyrethroid+ organophosphorous associations

The combination of chlorpyrifos + amitraz was compared in experiments V and Vl to some commercially available pyrethroid+ organophosphorous associations on Brazilian market. In experiment V, higher values of efficacy were seen from amitraz+ chlorpyrifos than from flumethrin+ coumaphos, although it could not be demonstrated statistically. In this experiment, amitraz treated animals presented higher number of ticks (p<0,05) on days +3 and +21 post treatment than amitraz+ chlorpyrifos treated ones, corroborating the efficacy of the new association on amitraz resistant tick strains.

In experiment Vl, 100% of efficacy was presented by amitraz+ chlorpyrifos from day +3 to day + 21. It caused higher reduction in tick amounts than cypermethrin+ ethion on days +3, +21 , +28 and +35 post treatment.

When all the experiments results are considered, it can be concluded that the combination of amitraz+chlorpyrifos improved has improved efficacy over the single compounds amitraz and chlorpyrifos, acting even against amitraz resistant ticks. Considering the problem represented by acaricide resistant Boophilus microplus in Brazil, this association is a useful approach in the control of this important parasite in bovine animals.

Table 2: Geometric means of Boophilus microplus female counts (between 4.5 and 8.0 mm of diameter) in bovine, and efficacy percentage

EXP Days post treatment / Number of B. microplus female ticks (Efficacy %)

ZERO 1 3 7 14 21 28 35

CONTROL 60,20^a 51,40^a 66,40^a 83,80^a 18,00^a 42,30^a

Amitraz (25Q ppm) + 62,10^a 6,50^b 0,70° 0,20^d 0,80° 10,80^b chlorpyrifos (5QQ ppm) (87,80%) (99,00%) (99,70%) (95,90%) (75,20%)

I 63,20^a 9,90^b 2,10° 2,60° 5,00^b 24,60^a

Chlorpyrifos (500 ppm) (81,60%) (96,90%) (97,00%) (73,30%) (44,60%)

64,70^a 42,60^a 23,40^b 38,00^b 9,1O³⁶ 44,30^a

Amitraz (250 ppm) (22,80%) (67,20%) (57,80%) (52,80%) (2,50%)

CONTROL 30,91 ^a 59,32^a 30,12^a 27,82^a 35,28^a 66,30^a 50,79^a

Amitraz (250 ppm) + 33,43^a 20,94^b 4,68^b 2,90^b 9,70^b 1,59° 7,23° chlorpyrifos (500 ppm) Il (67,35%) (85,62%) (90,35%) (74,57%) (97,78%) (86,83%)

Amitraz (250 ppm) 30,16^a 18,93^b 18,02^b 6,11 ^b 17,96* 11 ,18^b 21 ,69^b (67,29%) (38,68%) (77,48%) (47,81%) (82,71%) (56,22%)

CONTROL 44,05^a 81,57^a 80,13^a 40,19^a 53,32^a 16,17" 40,65^a

Amitraz (250 ppm) + 44,79^a 17,27^b 2,17^b 0,07° 0,28° 0,15^b 10,61^b chlorpyrifos (500 ppm) III (79,18%) (97,34%) (99,82%) (99,48%) (99,09%) (74,33%)

44,21 ^a 13,08" 2,45" 3,44^b 4,88^b 0,89^b 15,00"

Mmiiraz ^Zou ppm^

(83,02%) (95,23%) (89,24%) (88,42%) (92,50%) (48,87%)

CONTROL 38,38^a 27,20^a 28,49^a 33,89^a 36,74^a 70,80^a 82,28^a

Amitraz (250 ppm) + 37,93^a 6,97^b 1,61° 0,87° 2,73° 0,83^b 50,64^a chlorpyrifos (500 ppm) IV (74,06%) (94,28%) (97,41%) (92,48%) (98,81%) (37,71%)

Amitraz (250 ppm) 38,80^a 8,80^b 6,06^b 5,91 ^b 12,54^b 1,65^b 59,99^a (67,97%) (78,95%) (82,74%) (66,23%) (97,69%) (27,88%)

CONTROL 31,58^a 26,48^a 11 ,56^a 17,56^a 37,98^a 9,12^a

Amitraz (250 ppm) + 32,43^a 2,66^C 0,95° 0,00° 0,32^c 0,15° chlorpyrifos (500 ppm) (90,21%) (91,99%) (100,00%) (99,17%) (98,39%)

Flumethrin (30 ppm) + V 29,55^a 7,75" 2,01 " 1,16" 1,05^K 0,32^b coumaphos (400 ppm) (68,72%) (81,41%) (92,94%) (97,04%) (96,25%)

30,15^a 2,50° 0,78^b 0,43^b 2,01^b 0,58^b

Amitraz (250 ppm) (90,11%) (92,93%) (97,43%) (94,45%) (93,33%)

CONTROL 27,93^a 30,09^a 44,06^a 26,79^a 28,29^a 28,11^a 31 ,64^a 9,94^a

Amitraz (250 ppm) + 29,09^a 3,83^b 0,00° 0,00^b 0,00^b 0,00° 4,49^b 2,62^b chlorpyrifos (500 ppm) Vl (87,79%) (100,00%) (100,00%) (100,00%) (100,00%) (86,38%) (74,72%)

Cypermethrin (80 ppm) 29,26^a 8,16^b 2,77^b 0,91 ^b 0,12^b 1,84^b 34,24^a 18,95^a

+ ethion (600 ppm) (74,11%) (94,00%) (96,75%) (99,60%) (93,76%) (0,00%) (0,00%)

Means followed by at least a common letter, in the rows, don't differ by Tukey Test (P>0,05)

Claims

CLAIMS:

1. A veterinary composition for the control of acarine parasites on animals comprising as active ingredient a synergistic combination of amitraz and chlorpyrifos.

2. The composition according to claim 1, characterized in that the ratio of amitraz : chlorpyrifos is from 1 to 0.5-10 by weight.

3. The composition according to claims 1 or 2, characterized in that it is a liquid aqueous formulation

4. Use of a composition according to any of claims 1 to 3 for the preparation of a medicament for controlling acarine parasites on host animals.

5. Use according to claim 5, characterized in that the host animal is a bovine.

6. Use according to claims 5 or 6 characterized in that the acarine parasite is a tick.