Model predictions for anthelmintic resistance amongst Haemonchus contortus populations in southern Brazil

A computer model developed to study Ostertagia circumcincta resistance to anthelmintics in UK sheep flocks has been adapted for use with Haemonchus contortus under southern Brazilian conditions. The model simulates the effect of different anthelmintic control regimens on the year-to-year pattern of resistance in breeding ewes. The nematode control regimen most used by Brazilian sheep farmers was found to increase the frequency of genes which confer resistance from approximately 3% to 14% in an H. contortus population over a 20 year period. The effect of early versus late season anthelmintic treatment was investigated. This indicated that early season treatment would select for resistance rapidly, whereas late season treatments would not, owing to large numbers of untreated parasites accumulating at the beginning of the season. A model which can predict the development of anthelmintic resistance in parasites of ewes is a valuable tool in the understanding of the effect of different strategies on nematode control programmes and merits further consideration

Efeito do clima sobre a infecção parasitária em bezerros e presença de larvas em manejo rotativo de pasto em Santa Maria, RS, Brasil Climatological effects on parasitic infection in calves and the presence of larvae in a pasture rotation management in Santa Maria, RS, Brazil

O objetivo deste trabalho foi correlacionar os dados climáticos e parasitários através de exames laboratoriais e da pastagem. O experimento foi realizado no período de março a junho de 2004, utilizando 110 bezerros com idade média de cinco meses, em pastos com diferentes relevos. Foi avaliado o número de ovos por grama de fezes (OPG), a coprocultura e o número de larvas na pastagem em intervalos de 15 dias, e dados climáticos deciduais. A coprocultura revelou a presença de 60% de parasitas do gênero Trichostrongylus spp. e 40% de Cooperia spp. assim como Moniezia spp. e oocistos de Eimeria spp. A temperatura permitiu a sobrevivência e o desenvolvimento das larvas infectantes na pastagem durante o experimento. O aumento do número de larvas na pastagem está associado ao acréscimo da precipitação após um período de seca. O relevo com maior número de larvas apresentou maior concentração de massa seca de capim arroz (Echinochloa spp.). Pode-se comprovar que em condições climáticas ideais ocorreu uma rápida contaminação da pastagem com larvas infectantes quando animais naturalmente infectados foram transferidos para a área após colheita de milho.<br>The objective of this work was to correlate climatic and parasitological data from laboratory and field samples. The experiment was executed from March to June of 2004, using 110 naturally infected five months old calves. The counting of eggs per gram of feces (EPG), fecal culture and the number of larva on pasture was evaluated every 15 days in relation to decidual climatic data. The EPG increased during the study. The same observation occurred with the pluviometric level. Coproculture revealed the presence of 60% of Trichostrongylus spp. and 40% of Cooperia spp. as well as Moniezia spp. and Eimeria spp. oocists. The temperature during all the experimental periods was favorable to infecting larvae survival and development on pasture. The area with higher larvae count had the higher dry matter of "capim arroz" (Echinochloa spp.). It can be concluded that in optimal climatic conditions, there is a rapid pasture contamination with infecting larvae after the naturally contaminated animals are transferred to the area after corn harvest

Estudo comparativo da ação anti-helmíntica da batata de purga (Operculina hamiltonii) e do melão de são caetano (Mormodica charantia) em caprinos (Capra hircus) naturalmente infectados Comparative study of the anti-helminthic action of the potato of purges (Operculina hamiltonii) and the cantaloups of São Caetano (Mormodica charatia) in naturally infected goats (Capra hircus)

As helmintoses gastrintestinais ocupam lugar de destaque na produção de pequenos ruminantes como um fator limitante e o seu controle vem sendo realizado por meio do uso indiscriminado de anti-helmínticos favorecendo o surgimento da resistência a medicamentos. Com o objetivo de comparar a ação anti-helmíntica das plantas Operculina hamiltonii (batata de purga), Marmodica charantia (Melão de São Caetano) e do moxedctin a 0,2% sobre as infecções helminticas naturais de caprinos, foram utilizados 40 caprinos, sem raça definida, fêmeas, com idade entre seis e 12 meses, naturalmente infectados, separados em quatro grupos: o GRUPO 1 (G1) - animais controle negativo tratados com água destilada; o GRUPO 2 (G2) - animais tratados com o extrato alcoólico da O. hamiltonii; o GRUPO 3 (G3) - animais tratados com o extrato alcoólico da M. charantia e no GRUPO 4 (G4) - animais controle positivo tratados com moxidectina 0,2%. Todos os grupos receberam os tratamentos por três dias consecutivos. As amostras fecais foram coletadas nos dias 0, 30 e 60 após tratamento, para a realização da contagem de ovos por grama de fezes (OPG) e larvacultura. Para avaliar o efeito dos tratamentos, aplicou-se o teste de redução na contagem de ovos por grama de fezes (RCOF). A RCOF do G2, G3 e G4 foram de 63 e 90; 40 e 40; 100 e 100%, respectivamente para 30 e 60 dias pós-tratamento respectivamente. Durante o período de estudo, observou-se que todas as amostras coletadas estavam positivas para larvas de helmintos da superfamília Trichostrongyloidea, com exceção para o G4, nos dias 30 e 60 pós-tratamento. O Haemonchus foi o parasita mais prevalente nas coproculturas.<br>Gastrintestinal helminthosis occupy a place of prominence in the production of small ruminants as an edge factor. Its control has been carried through the indiscriminate use of anti-helminthic products in favor of the appearing resistance to the medicines. With the objective to compare the anti-helminthic action of the Operculina hamiltonii plants (potato of purges), Marmodica charantia (Cantaloups of Sao Caetano) and of moxedctin at 0.2% about the natural helminthic infections of goats, there had been used 40 goats, without defined race, females, with age between six and 12 months, naturally infected, separated in four groups: GROUP 1 (G1) negative control animals treated with distilled water; GROUP 2 (G2) -animal treated with the alcoholic extract of O. hamiltonii; GROUP 3 (G3) - animal treated with the alcoholic extract of M. charantia and GROUP 4 (G4) - positive control animals treated with moxidectina at 0.2%. All of them had received the treatments for three days in a row. The feces samples were collected at: 0, 30 and 60 days after treatment, for the accomplishment of the egg counting per gram of excrements (EPG) and larvae culture. To evaluate the effect of the treatments, a reduction on the egg counting per gram of excrements (RECE) was applied. The RECE of the G2, G3 and G4 were: 63 and 90; 40 and 40; 100 and 100%, respectively for 30 and 60 days post-treatment, respectively. During the period of study it was observed that all collected samples were positive for larvae of helminths of the superfamily Trichostrongyloidea, except for the G4, throughout 30-60 days and post-treatment. The Haemonchus was the most prevalent parasite in the culture of feces