Acaricidal effect of major compounds to control Rhipicephalus microplus (Canestrini, 1887) in dairy cows and possible alternatives for reversing multidrug resistance.

Tick control represent a great challenge to animal health. The objective of this study was to evaluate the efficacy of acaricidal compounds against Rhipicephalus microplus from dairy cattle systems in Paraná State, Brazil. Six farms (PR1-PR6) were selected, where anti-tick products were applied at fixed intervals. Two other farms that adopted alternative protocols; target selective treatment (PRS), and individual-based agroecological protocol (PRA) were also included in the trial. Fully engorged R. microplus were collected for the in vitro adult immersion test (AIT), and the egg hatch test (EHT) in all eight populations. The larval packet test (LPT) was used on PR6 and PRA tick populations. The treatment groups were composed of G1: dichlorvos 45% plus cypermethrin 5%, G2: deltamethrin 2.5%, G3: cypermethrin 15%, chlorpyriphos 25%, plus citronellal 1%, and G4: amitraz 12.5%. The efficacy at PR1 to PR6 revealed that G3 and G4 achieved moderate to high efficacy, from 75.0 to 100.0% and 73 to 98%, respectively. In the LPT, the efficacy at PR6 was 76.0, 67.0, 93.0 and 30.6%, while PRA presented 100.0, 100.0, 100.0, and 54.0%, for G1, G2, G3 and G4, respectively. Sustainable parasite control strategies are discussed.

Aspectos epidemiológicos e clínicos da estefanofilariose em vacas leiteiras e comparação entre métodos de diagnóstico / Epidemiological and clinical features of stephanofilariasis in dairy cows and diagnosis methods confrontation

A estefanofilariose é uma doença mundialmente distribuída e caracteriza-se por lesões na pele causadas por nematódeo do gênero Stephanofilaria. Nos bovinos manifesta-se por uma dermatite crônica associada com erupção papular progredindo para nódulos, alopecia e ulceração crostosa. Apesar de reconhecida há muitos anos, há poucos estudos e relatos sobre a mesma. A literatura é particularmente escassa no Brasil. Esse trabalho teve como objetivos investigar aspectos epidemiológicos e clínicos da estefanofilariose em vacas leiteiras naturalmente acometidas e comparar dois métodos para a confirmação do diagnóstico, o exame histopatológico e o exame direto. Foram investigados aspectos clínicos relacionados à ocorrência natural da estefanofilariose em 58 vacas de leite de sete rebanhos criados nos municípios de Santana do Itararé, PR e de Itaberá, SP durante o período de janeiro de 2006 a agosto de 2008. Dois métodos foram comparados para confirmação do diagnóstico a partir de tecido colhido por biópsia da borda das lesões, o histopatológico (n=24) e o exame direto do sedimento da solução salina isotônica na qual o tecido permaneceu embebido (n=20). A maior prevalência ocorreu de dezembro a março (57 por cento) e a maioria das vacas era lactante (87,9 por cento). As lesões se localizavam nos quartos anteriores do úbere em seu aspecto cranial (96,7 por cento), principalmente próximo à linha média (55 por cento). A lesão típica tinha formato circular era ulcerada com crostas e exibia exsudato sero-sanguinolento. No exame histopatológico evidenciou-se uma dermatite crônica com infiltrado mononuclear e eosinofílico. A presença do parasita não foi detectada em nenhum dos cortes examinados. O exame direto possibilitou a demonstração do agente em todas as amostras examinadas, comprovando-se como um método eficiente para a confirmação do diagnóstico.

Stephanofilariasis is a worldwide disease caused by the nematode Stephanofilaria that determines skin lesions. In cattle, the chronic dermatitis is characteristic begining with papules that progress to nodules, alopecia and ulcers with crusts. Despite it's long time recognition, there are few studies and reports about this disease, specially in Brazil. This work was conducted in order to investigate epidemiological and clinical features of stephanofilariasis in dairy cows and to compare two methods for the diagnosis confirmation. Fifty-eight naturally affected dairy cows from seven herds located in Santana do Itararé, state of Paraná, and Itaberá, state of São Paulo, were studied from January 2006 through August 2008. Two methods for the diagnosis confirmation were compared using biopsied tissues from the border of the skin lesion: the histopathological examination (n=24) and the direct sediment examination of an isotonic saline solution in which the tissue fragment remained soaked (n=20). The prevalence was higher from December to March (57 percent) and lactating cows were primarily affected (87,9 percent). The cranial aspect of the fore mammary glands was the main site of the skin lesions (96,7 percent), chiefly near the ventral midline (55 percent). The characteristic wound was of circular shape, ulcerated with crusts and serosanguineous exudation. Chronic dermatitis with eosinophilic and mononuclaer cell infiltrates was the histopathologic change pattern present. The parasite was not detected in any histologic section examined. The direct sediment examination otherwise proved to be efficient for the diagnosis confirmation revealing the nematode adult and larval forms in all the specimens.