BIOASSAYS FOR MEASURING THE ACARICIDES SUSCEPTIBILITY OF CATTLE TICK BOOPHILUS MICROPLUS (CANESTRINI, 1887) IN SÃO PAULO STATE, BRAZIL

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BIOASSAYS FOR MEASURING THE ACARICIDES SUSCEPTIBILITY OF CATTLE TICK BOOPHILUS MICROPLUS (CANESTRINI, 1887) IN SÃO PAULO STATE, BRAZIL

M.C. Mendes¹, C.J. Veríssimo², C.N. Kaneto³, J.R. Pereira⁴

1 Centro de Sanidade Animal, Instituto Biológico, Av. Cons. Rodrigues Alves,1252, CEP 04014-002, São Paulo, SP, Brazil. E-mail: [email protected]

ABSTRACT

The susceptibility of Boophilus microplus tick to acaricides was evaluated on farms located in different regions of São Paulo State. The method used for the evaluation was the immersion of engorged tick females in commercial formulation of the chemical groups organophosphate, pyrethroids, amitraz and the association between organophosphate and pyrethroid. The efficacy of pyrethroid acaricides was lower than 50% in all regions studied. The association between the organophosphate and pyrethroid had the mean efficacy higher than 90% in the North Region, and the amitraz had efficacy higher than 90% in the Northwest and Southern Regions. This work shows the low efficacy of pirethroids acaricides on Boophilus microplus in São Paulo State nowadays.

KEY WORDS: Boophilus microplus, pyrethroids, organophosphate, amitraz, resistance.

RESUMO

BIOENSAIO PARA AVALIAR A SENSIBILIDADE DO CARRAPATO Boophilus microplus (CANESTRINI,1887) A CARRAPATICIDAS NO ESTADO DE SÃO PAULO, BRASIL. Foram avaliadas amostras de carrapato Boophilus microplus provenientes de fazendas localizadas em diferentes regiões do Estado de São Paulo. O método usado foi de imersão de teleóginas em formulações comerciais dos grupos químicos organofosforado, piretróide, amitraz e associação organofosforado e piretróide. A eficácia de produtos à base de piretróides foi inferior a 50% em todas as regiões avaliadas; a eficácia média da associação entre o produto organofosforado e o piretróide foi superior a 90% na região norte do Estado. O amitraz teve, em média, eficácia superior a 90% nas regiões sudeste e noroeste. Constatou-se a baixa eficiência que vêm tendo atualmente os produtos piretróides sobre cepas de Boophilus microplus provenientes de várias regiões do Estado de São Paulo.

PALAVRAS-CHAVE: Boophilus microplus, piretróides, organofosforados, amitraz, resistência.

2 Instituto de Zootecnia, Nova Odessa, SP

3 Departamento de Apoio, Produção e Saúde Animal - Curso de Medicina Veterinária – UNESP, Araçatuba, SP

4 Laboratório de Sanidade Animal e Vegetal de Pindamonhangaba - Instituto Biológico, Pindamonhangaba, SP INTRODUCTION

Boophilus microplus is an ectoparasite that causes great harm to susceptible bovines, due to its spoliatory effects and its hemoparasites vectorial hability, producing great economic losses (VERÍSSIMO, 1993).

There is no official policy about tick control in bovines in Brazil. Farmers adopt individual control practices which can become a significant part of the production costs for both milk and meat production.

These parasites can be chemically controlled using strategic applications based on epidemiologic surveys. This can lead to great advantages such as

lower operational and medical costs and lower toxicological risks at the farms. Nevertheless, according to the study made by ROCHA et al., 1999, at Lavras, Minas Gerais State, the majority of producers know the existence of the strategic control but do not use this technology. At these farms, tick control is done based on “traditional” forms, using the acaricide products intensively and unorganized, 12 to 24 times per year. This inadequate use of the acaricides, besides representing economic waste, favors the selection of resistant ticks (LEITE, 1988).

To date there have been more than 45 reports from Australia, Africa, Asia and South America showing

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different degrees of resistance of B. microplus to organophosphates, synthetic pyrethroids and amitraz (MARTINS et al., 1999).

In Brazil, the reports of tick resistance to these chemicals have indicated the lower efficacy of pyrethroid products (VIEIRA et al., 1998; SILVA et al., 1999; CHAVES & COSTA JUNIOR, 1999; GOMES et al., 1999;

ALVES-BRANCO et al., 1999; FARIAS et al., 1999; SOUZA et al., 1999).

Acaricide sensitivity data obtained from some parts of São Paulo state has shown a sensitivity profile analogous to that observed in other Brazilian states (MENDES, 1994; MURAKAMI & SILVA, 1997; OLIVEIRA &

FREITAS, 1998; SOARES et al., 1999).

The present work aimed to analyze the sensitivity of Boophilus microplus tick from different regions of São Paulo State to the chemical groups organophosphates, pyrethroids, amitraz, as well as to investigate the association between organophosphates and pyrethroid.

MATERIALS AND METHODS

Boophilus microplus samples were collected on dairy and beef farms, located in different regions of São Paulo State, from the years 1977 to 1999: a) region known as Vale do Paraíba (ten properties, being three at the city of Pindamonhangaba, 22°9’S - 45°4’W;

three at Jacareí, 23°3’S - 45°9’W; and one at Caçapava, 23°1’S - 45°7’W; Lorena, 22°7’S - 45°1’W; Santa Bran- ca, 23°3’S - 45°8’W; and Mogi das Cruzes, 23°5’S - 46°1’W; cities.); b) the Southern Region (four properties at the cities of Campinas, 22°9’S - 47°W; Porto Feliz, 23°2’S - 47°5’W; Nova Odessa, 22°7’S - 47°2’W; and Americana, 22°7’S - 47°3’W) c) the North Region (four properties being at the cities of São José do Rio Preto, 20°8’S- 49°3’W; Colina, 20°7’S- 48°5’W; Mococa, 21°4’S - 47° W; and Araraquara, 21°7’S - 48°1’W.) d) the Northwest (nine properties, seven located at Araçatuba, 21°2’S - 50°4’W; city and the others located at Birigui, 21°2’S - 50°3’W; and Guararapes 21°2’S - 50°6’W.).

Samples were separated into groups of ten engorged females each, weighed and labeled with the total weight of the ticks, the product name, the property name and date.

Each group was immersed in the different acaricides diluted in water, following the manufacturer's recommendations, for an interval of five minutes, except for the cypermethrin and deltamethrin products (ten minutes). The products used were based on the following principles: amitraz, pyrethroids (deltamethrin, cypermethrin, lambda cyalothrin, alfamethrin and alfa cypermethrin), organophosphates (coumaphos) and the association between pyrethroid and organophosphates

(clorfenvinphos plus cypermethrin). After the immersion period, the engorged females were recovered by passage through plastic filter and dried on paper towel. These ticks were placed on petri’s dishes and incubated at 27-28^oC, 85%-95% relative humidity, for two weeks. After the 15th day the batches of eggs were collected and weighed. These eggs were placed in glass tubes sealed with a cotton plug and kept under the same conditions described above during the whole incubation period; in this way, it was possible to determinate the hatching percentage for each egg mass.

The data obtained with the egg batches from the experimental group and the control group was used to calculate the Reproductive Efficiency (ER) and the Product Efficacy (EP) using the following formulas, by DRUMMOND et al. (1973).

Reproductive Egg weight x hatching x 20 000 Efficiency (ER) =

Weight of females

Product ER (control) - ER (experimental) x 100 Efficacy (EP)=

ER (control)

For the statistical analyses of the data the Variance Analysis and Tukey’s Test were used.

RESULTS AND DISCUSSION

The mean values of efficacy for each acaricide at the different regions studied are shown in Figures 1, 2, 3 and 4. Generalizing, it has been shown that the pyrethroids’ efficacies were lower than 50% in all evaluated regions. The association between the organophosphates and pyrethroid had the mean efficacy higher than 90% in the North region, and amitraz had a mean efficacy higher than 90% in the Northwest and Southern regions.

The efficacies of the acaricides tested on ticks from the Southern and Vale do Paraíba regions were lower than those found with the same products tested on ticks from the North and Northwest regions. This fact may be due to the high predominance of zebuine cattle in North and Northwest regions, leading to a lower acaricide use, when compared with Southeast and Vale do Paraíba regions where the cattle have a higher degree of European bovine genotype, and consequently, higher sensitivity to Boophilus microplus, requiring more acaricide treatments, which in turn leads to the selection for resistance to the acaricides.

The variance analysis (Table 1) of the North region showed a significant difference (p<0.05) between

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Table 1 - Mean efficacy of the acaricide products.

Coumaphos(%) Amitraz(%) Organophosphates +Pyrethroid(%) Pyrethroids(%)

North Region 79.285ab 81.415 *a 94.4 *a 42.18 b

Northwest Region 75.687 ***a 93.068 *** a 83.903 ***a 33.36 b

Southern Region 57.01 ab 95.825 ** a 66.266 ab 20.509 b

Vale do Paraíba 63.94 ab 74.44 **a 87.91*** a 37.55 b

Different letters mean (* p < 0.05; ** p < 0.01; *** p < 0.001)

North Region

0 10 20 30 40 50 60 70 80 90 100

Coumaphos Amitraz Pyretroid + Organophosphate

Pyretroid

Products

Percentages

Mean SD

Northwest Region

0 20 40 60 80 100

Pyretroid

Products

Percentages

Mean SD

Fig. 1 - In vitro efficacy of acaricides on Boophilus

microplus from North region of São Paulo State, Brazil. Fig. 2 - In vitro efficacy of acaricides on Boophilus microplus from Northwest region of São Paulo State, Brazil.

Fig. 4 - In vitro efficacy of acaricides on Boophilus microplus from Vale do Paraíba region of São Paulo State, Brazil.

Fig. 3 - In vitro efficacy of acaricides on Boophilus microplus from Southern region of São Paulo State, Brazil.

amitraz and pyrethroids group; and the association of organophosphates and pyrethroid.

In the Northwest the difference was highly significant (p<0.001) among the groups treated with coumaphos, amitraz, and the association of pyrethroid with organophosphates, compared with the pyrethroid treated group.

Ticks proceeding from Southern region and Vale do Paraíba showed significant difference (p<0,01) between treatments with pyrethroids and amitraz.

Samples from Vale do Paraiba only showed high significance difference (p<0.001) when treated with pyrethroid acaricides compared to the association organophosphates and pyrethroids.

The synthetic pyrethroids were introduced to the Brazilian market in the 1980’s and they have been used with high efficacy by various authors in laboratory, field and stable tests (MASSARD et al., 1982;

STENDEL, 1980; DAVEY et al., 1982; DAVEY & AHRENS, 1984; GRISI & ROCHA, 1985; SOSA, 1985; PEREIRA & LUCAS, 1987). However, Leite (1988) had already demonstrated a decrease in the sensitivity of some B.

microplus strains originating from Rio de Janeiro State, as a result, mainly, of the intense and incorrect use of these products.

Our results are in agreement with those obtained by various authors from São Paulo State (MURAKAMI &

SILVA, 1987; OLIVEIRA & FREITAS, 1998; SOARES et al.,1999)

Vale do Paraíba

0 10 20 30 40 50 60 70 80 90 100

Pyretroid

Products

Percentages

Mean SD Southern Region

0 10 20 30 40 50 60 70 80 90 100 110

Pyretroid

Products

Percentages

Mean SD

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and from other Brazilian States (VIEIRA et al.,1998;

SILVA et al.,1999; CHAVES & COSTA JÚNIOR, 1999; GOMES

et al.,1999; ALVES-BRANCO et al.,1999; SOUZA et al.; 1999) showing the low efficacy of the chemical group of pyrethroids on B. microplus strains from some São Paulo State regions.

Further tests (larval packet test) are necessary to measure the degree of resistance.

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Received on 5/12/00 Accepted on 15/8/01