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A B S T R A C TGastrointestinal helminthosis in ruminants cause considerable economic losses, with marked impairment of productivity of these animals, especially in poor management systems and poor parasite control programs. Infections caused by these helminths represent an obstacle to the expansion of the sheep industry. Furthermore, high parasite burdens were associated with increased mortality in calves. The recommended methods for the control of gastrointestinal helminths not always have practical applicability. We discuss important epidemiological and control aspects concerning gastrointestinal nematodes in sheep and cattle. Thus, sustainable worm control practices are recommended. Each farm has a specific situation and a management system directed to a specific parasitic infection must be adopted.Keywords: cattle, sheep, gastrointestinal helminths, epidemiology, control, sustainability. R E S U M OHelmintíases gastrintestinais em ruminantes acarretam perdas econômicas relevantes, com marcante prejuízo da produção animal, especialmente em sistemas de maneio precários e em programas de controle parasitário deficientes. Infeções causadas por esses helmintos representam um obstáculo para a expansão do mercado ovino. Ademais, altas cargas parasitárias foram associadas à elevada mortalidade em bezerros. Os métodos recomendados para o controle de helmintos gastrintestinais nem sempre apresentam aplicação prática. Nós discutimos os aspectos importantes sobre nematodes gastrintestinais em ovinos e caprinos. Sendo assim, práticas de controle sustentáveis são recomendadas. Cada propriedade possui uma situação em particular e um sistema de maneio direcionado deve ser adotado para as infecções parasitárias específicas.Palavras -chave: bovinos, ovinos, helmintos gastrintestinais, epidemiologia, controlo, sustentabilidade. 665Bresciani et al., Gastrointestinal nematodes in sheep and cattle

The mechanisms responsible for the imbalance between oxidants and antioxidants in sheep infected with Haemonchus contortus are not well established. This study aimed to prove the hypothesis that oxidative stress occurring during infection by H. contortus varies according to breed, and that the parasite burden correlates with hypoalbuminaemia and anaemia. Thus, after deworming and confirming the absence of infection, two different sheep breeds, Suffolk (n = 15) and Santa Ines (n = 22), were orally inoculated with a single dose of 5,000 L3 of H. contortus. The egg counts per gram of faeces (EPG), packed cell volume (PCV) and concentrations of several plasma markers of oxidative stress (lipid peroxidation, albumin, uric acid, total bilirubin, total antioxidant capacity [TAC], total oxidant concentration [TOC] and the oxidative stress index [OSI]) were quantified before (control group) and during the experimental infection (28, 34 and 42 days post-inoculation). In both breeds, TOC increased at 28 days and TAC increased at 42 days. In Suffolk sheep, there was a positive correlation of EPG with oxidant components (28 days) and a negative correlation of EPG with PCV (42 days). In Santa Ines sheep, there was a positive correlation of EPG with bilirubin (r = 0.492; p = 0.020). H. contortus infection caused oxidative stress, which varied according to the breed. Parasite burden was not associated with hypoalbuminaemia, whereas there was a negative correlation with PCV. This research provides the first evidence that the antioxidant status contributes more to the resilience to H. contortus in Santa Ines sheep compared to Suffolk sheep.

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