The prevalence of anthelmintic resistance in nematode parasites of sheep in Southern Latin America: Paraguay

Abstract

This survey to detect anthelmintic resistance in nematode parasites of sheep was conducted on 11 farms in the Occidental and 26 farms in the Oriental Regions of Paraguay using the faecal egg count reduction test (FECRT). The anthelmintic groups tested were the benzimidazoles, levamisole and avermectins (both oral and injectable). Overall the levels of resistance were 73%, 68%, 73% and 47%, respectively. Levels of resistance were similar for all three important nematode genera, viz. Haemonchus contortus, Ostertagia and Trichostrongylus. This survey clearly indicates that a large, and ever increasing, proportion of sheep farmers are rapidly approaching the time when they will have exhausted all chemotherapeutic options to control parasites. Unless they face having to abandon their sheep farming operations, radical changes will need to be implemented with urgency.

Domestication of ruminant livestock and the impact of nematode parasites:possible implications for the reindeer industry

“…However resistance to the only remaining group, the macrocyclic lactones, is now rapidly increasing in the most economically important nematodes of sheep and goats (Sangster, 1999). There are now instances, such as in Malaysia, southern Brazil, Paraguay and South Africa, where farmers abandoned farming of sheep and goats because of uncontrolled parasitic disease with annual mortalities exceeding 20%, due to total anthelmintic failure (van Wyk, 1990;Maciel et al, 1996;Chandrawathani et al, 2004). Resistance in cattle nematodes appears to be spreading, but the reports are localised isolations.…”

“…Such systems are unsustainable. The inevitable penalty for suppressive anthelmintic treatment is the development of very high levels of resistance across the entire range of available anthelmintics, with the ultimate consequence that farmers are forced into abandoning their livestock enterprises (van Wyk, 1990;Maciel et al, 1996). The costs of parasites to such livestock producers are obvious.…”

Drug Resistance in Human Helminths: Current Situation and Lessons from Livestock

“…In parts of Paraguay (95) and South Africa (140), helminths are resistant to all available broadspectrum anthelmintics and farmers have started to give up sheep farming because of insurmountable problems with AR (138).…”

Desempenho De Cordeiros Naturalmente Infectados Com Parasitas Gastrintestinais Utilizando O Tratamento Seletivo Com O Método Famacha E O Tratamento Preventivo

“…O tratamento preventivo/supressivo promove a seleção de organismos geneticamente e fisiologicamente resistentes, que sobreviverão ao contato com drogas anti-helmínticas (PRICHARD, 1994). A resistência anti-helmíntica múltipla foi determinada em vários países, como Brasil, Paraguai, África do Sul e Malá-sia (ECHEVARRIA et al, 1996;MACIEL et al, 1996;VAN WYK et al, 1999;CHANDRAWATHANI et al, 2003). Pesquisadores alertam que, com a utilização de drogas de forma pouco criteriosa, muito em breve haverá a redução das fontes de controle químico causando prejuízo para produtores que dependem desta atividade (MOLENTO e PRICHARD, 1999; VAN WYK et al, 1999).…”