Abstract
Controlled-release albendazole capsules (CRCs) are currently registered for use in Australia and New Zealand as anthelmintic treatment in sheep. However, reports on the efficacy of such products on resistant parasite populations are sometimes controversial. This is the first study to report on the efficacy of such products under South African field conditions in sheep harbouring a population of Haemonchus contortus with known multiple anthelmintic resistance, including to albendazole. Treatment groups were comprised of CRC-treated and single dose albendazole-treated sheep, as well as negative controls. Groups were compared by using faecal egg count reduction tests, FAMACHA© anaemia scoring, conception rates and comparative weight gains over three and a half months. Based on a comparison of faecal egg counts, no advantage could be found using CRCs. Moreover, the use of the product actually decreased weight gain when compared with the control group animals.
Highlights
Worldwide, anthelmintic resistance is a major problem in the livestock industry
The controlled-release capsule (CRC) is a tool that has been developed to extend the efficacy of anthelmintics after treatment
The Kruskal-Wallis test revealed that the only significant difference in Faecal egg counts (FEC) between groups existed at day 15 after treatment (H (3) = 16.36, p < 0.001), at which time the single treatment albendazole group had an efficacy of 83.6% (Table 3)
Summary
Anthelmintic resistance is a major problem in the livestock industry. Against this background, novel compound discovery, combinations, methods of delivery, parasite management programmes and even vaccinations have been actively researched in order to make livestock farming more profitable, or in severe cases, even possible. The controlled-release capsule (CRC) is a tool that has been developed to extend the efficacy of anthelmintics after treatment. This would lead to longer treatment intervals with accompanying reduced stress to animals and labour costs. Previous reports have indicated conflicting results as to the efficacy of the sustained-released anthelmintics against resistant parasites (Sutherland et al 1998). One such product registered for use in Australia and New Zealand is a 35% m/m albendazole sustained-release capsule (Extender 100®, Merial, New Zealand) that can provide 100 days of continuous protection against susceptible strains of Haemonchus contortus (H. contortus) (according to the product’s package insert)
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