ABSTRACT.-Sczesny-Moraes E.A., Bianchin I., Silva K.F., Catto J. Among the methods of control of gastrointestinal worms in sheep, the use of chemicals is the most common. However, the continued, and indiscriminate, use of these products has selected populations of resistant helminths to anthelmintics, a phenomenon reported in the whole world. This study aimed to identify the species of gastrointestinal parasites and diagnose the status of anthelmintic resistance in sheep in the State of Mato Grosso do Sul Brazil. Feacal egg count reduction tests (FECRT) were performed in flocks of sixteen farms, and the seven formulations used contained the following pharmacological bases: Albendazole, Ivermectin, Levamizol, Trichlorfon, Moxidectin, Closantel and one containing the first three in association. The species identified at necropsy, in adult sheep, were: Haemonchus contortus, Trichostrongylus colubriformis, Cooperia curticei, C. punctata, C. pectinata and Oesophagostomum columbianum, in order of prevalence. The formulations containing Albendazole and Ivermectin did not show efficacy in reducing the EPG in the flocks tested, with average reductions of 0.7 and -19.6%, respectively. Closantel presented an average efficacy of 6.7%; Levamisolee, Moxidectin and Trichlorfon, 28.7, 26.8 and 65% respectively, the combination of three bases (Albendazole, Ivermectin and Levamizol), an average efficacy of 55.8 %. The average percentages of infective larvae recovered in the faecal cultures, pre and post treatment were similar, indicating that resistance to the bases tested is present in all species cited, to a greater or lesser degree. The two genera predominantly resistant are Haemonchus sp., with 86.9%, followed by Trichostrongylus sp., with an average of 47.5%, Strongyloides sp. 33.6%, Oesophagostomum sp.

The hornfly and losses caused by it in Nellore cows and pre-weaning calves where studied, using two groups of 60 animals each, one group with a natural infestation and the other without hornfly, during four consecutive years. It was seen that the number of flies on the cows did not exceed an average of 80 flies/animal in all years of observation. The majority of the cows (83%) had few flies, whereas 17% had larger numbers. The calves were infested with few flies. Rainfall in excess of 100 mm during short periods diminished fly infestation. Weight gain in the cows without flies (treated with insecticides) as well as their calves was greater than in the control cows, but not statistically significant (P>0.05). Mean percentage pregnancy during the four years was 15% more in treated cows than the non-treated animals, and this difference was probably due to the infestation of the bulls.

II Controle alternativo de nematódeos gastrintestinais dos ruminantes: atualidade e perspectivas

Endo- and ectoparasite infections are among the most important causes of disease and production losses in beef cattle in tropical and subtropical regions. Nevertheless, most treatments are given without epidemiological information and without evaluating their effect on the development of the animals. In this work we present the results of a study of the effect of treatments against endo- and ectoparasites in crossbred steers, during three cycles of field trials in the Brazilian Cerrado region. Three anthelmintic treatments during the winter and three acaricidal treatments during the spring/summer provided significant additional weight gain in three and two experimental trials, respectively. In the trials, steers treated for gastrointestinal nematodes gained a mean of 33 kg more and those treated for ectoparasites had additional mean weight gains of 13 kg compared with non-treated steers.

A presente investigação foi realizada devido à escassez, no Brasil, de informações sobre os possíveis danos decorrentes da ação hematófaga da mosca-dos-chifres, Haematobia irritans (L.), em bovinos da raça Nelore. O estudo foi realizado durante quatro estações chuvosas (outubro a abril), de 1991 a 1995. Em cada ano, 80 bovinos foram utilizados de acordo com os seguintes tratamentos: 28 touros com um ano de idade divididos em quatro grupos; 20 bois com idade de dois anos divididos em quatro grupos, e 32 bois com três anos e divididos em oito grupos. Metade dos grupos de animais de cada idade eram tratados contra H. irritans com intervalos de 28 dias e os demais mantidos como grupos controle. As moscas foram contadas a cada 14 dias e o peso dos bois registrado a cada 28. O número médio de mosca/animal dos grupos controle para o primeiro, segundo, terceiro e quarto anos do estudo foi, respectivamente: cinco, cinco, quatro e cinco, nos animais de um ano; 15, 11, 13 e 27, nos de dois anos e 55, 31, 40 e 51, nos de três anos. Observou-se que maior número de moscas (P<0,05) atacou os animais mais velhos. Houve, em todos os períodos de avaliação, apesar do número de moscas por animal poder ser considerado baixo, um ganho de peso significativo (P<0,05) em prol dos grupos tratados contra H. irritans comparativamente aos grupos não tratados. Os ganhos foram 8,6; 16,0 e 10,4% superiores, respectivamente, para animais de um, dois e três anos de idade. Esse ganho de peso por animal e por ano foi da ordem de 9, 5, 7 e 8 kg para os animais com um ano de idade; de 26, 10, 23 e 12 kg para aqueles de dois anos, e de 16, 8, 9 e 11 kg nos de três anos.