Portal de Pesquisa da BVS Veterinária

Acta sci. vet. (Impr.); 40(2): Pub. 1028, 2012. tab

Artigo em Português | VETINDEX | ID: biblio-1373550

Resumo

Background: Rhipicephalus (Boophilus) microplus (Canestrini, 1887) traditionally known as cattle tick, is the species that most affects cattle productivity levels in Brazil. The parasite causes annual losses up to US$ 2 billion. Despite several researches carried out all over the globe, it still presents great challenge, especially due to evidence of resistance to chemical products used in plague control. The goal of this project was to verify in vitro efficiency of pesticides in controlling R. (B.) microplus, at Campos dos Goytacazes municipality, Rio de Janeiro, Brazil, in 2007. Materials, Methods & Results: The in vitro test used was the one recommended by FAO's (Food and Agriculture Organization) World Acaricides Resistance Reference Center (WARRC). Engorged females were manually collected off the ground from stalls and separated in two treatments, amitraz 12.5% (commercial dilution 1:500 = 2 mL/1000 mL) and cypermethrin 15% (commercial dilution 1:1000 = 1 mL/1000 mL), each one with six groups of ten parasites. A different solution - 1:10, 1:100, 1:1000, 1:100000 and 1:1000000 - for both acaricides tested was used on each group, and for control was used potable water. The test was started from the highest dilution. Each dilution was repeated three times simultaneously. Recommended dilutions in the research were in the protocol. Each group of engorged females was weighted in analytical precision scale with equivalence in measurement of weights and, further, transferred to a Becker, containing 50 mL of the solution to be tested, previously prepared. The Becker was kept in constant agitation for five min. Afterwards, the engorged females were put upon towel paper (15 cm²) in order to remove excess of the product, being then transferred to Petri plates (100 mm x 20 mm height), identified and taken to a BOD incubator at 28°C (± 1) and 80% humidity. After oviposition, the number of eggs laid by each group were weighted and inserted in previously adapted plastic syringes, identified and taken again to the same incubator. We conducted the reading of the eggs hatching percentage after 30 days, with a stereoscopic microscope, using as reference the hatching observed in the control group that was kept on a different incubator. The reproduction efficiency (RE) was calculated using the equation; RE = eggs' weight/female's weight x % hatching x 20.000. The control percentage was calculated following the equation, considering the arithmetic mean of three repetitions: % control = RE (non-treated) - RE (treated)/RE non-treated x 100. We obtained as results after a 30 days analysis, a mean percentage of total efficiency of 96.60% for amitraz 12.5% and of 98.00% for cypermethrin 15% in the control of eggs hatching. Discussion: The amitraz 12.5% and the cypermethrin 15% presented excellent results in controlling wild strains of R. (B.) microplus that attacks cattle at Campos dos Goytacazes municipality, Rio de Janeiro, agreeing with FAO's WARRC and the Ministério da Agricultura, Pecuária e Abastecimento (MAPA), which established a legally accepted efficacy for acaricides being equal or superior to 80.00% and 95.00%, respectively, over tick strains. Hence the importance of this pioneer project in the region and its contribution to the subject extension.

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