Abstract
BackgroundParasitic nematodes can cause substantial clinical and subclinical problems in alpacas and anthelmintics are regularly used to control parasitic nematodes in alpacas. Although anthelmintic resistance has been reported in ruminants worldwide, very little is known about anthelmintic resistance in alpacas. The present study was carried out to confirm a suspected case of anthelmintic resistance in Haemonchus contortus in alpacas in Australia.MethodsPost mortem examination of an alpaca was conducted to determine the cause of its death. To confirm a suspected case of macrocyclic lactone (ML) resistance in H. contortus in alpacas, a faecal egg count reduction test (FECRT) was performed using closantel (7.5 mg/kg) and ivermectin (0.2 mg/kg). Nematode species were identified by morphological and molecular methods.ResultsPost mortem examination of a 1-year-old female alpaca that had died following a brief period of lethargy, anorexia and recumbency revealed severe anaemia, hypoproteinaemia and gastric parasitism by adult Haemonchus contortus, despite recent abamectin (0.2 mg/kg) treatment. Based on these findings and the exclusive use of MLs in the herd over the preceding six years, ML resistance in parasitic nematodes of alpacas on this farm was suspected. FECRT revealed that the efficacy of closantel was 99% (95% CI 93-100), whereas that of ivermectin was 35% (95% CI 0-78), indicating that the treatment failure was likely due to the presence of ML-resistant nematodes. Larval culture of faecal samples collected following ivermectin treatment consisted of 99% H. contortus and 1% Cooperia oncophora, a result confirmed using a PCR assay.ConclusionsThis study provides the first evidence of ML resistance in H. contortus in alpacas in Australia. Based on the extent of anthelmintic resistance in sheep gastrointestinal nematodes in Australia, veterinarians and alpaca owners should be encouraged to implement integrated parasite management strategies to improve nematode control in alpacas.
Highlights
Parasitic nematodes can cause substantial clinical and subclinical problems in alpacas and anthelmintics are regularly used to control parasitic nematodes in alpacas
Alpacas in the herd were routinely vaccinated against clostridial diseases and were drenched orally with macrocyclic lactone (ML) anthelmintics, once each summer and once each winter
Resistance in major gastrointestinal nematodes (GINs) of sheep against all major classes of anthelmintics is well documented in Australia [15,16,17]
Summary
Parasitic nematodes can cause substantial clinical and subclinical problems in alpacas and anthelmintics are regularly used to control parasitic nematodes in alpacas. Anthelmintic resistance has been reported in ruminants worldwide, very little is known about anthelmintic resistance in alpacas. In the last two decades, domesticated South American Camelids (SACs), llamas (Lama glama) and alpacas (Lama pacos), have been farmed increasingly for their fine fleece and adaptability to many climatic regions. Parasitic nematodes can cause substantial clinical and subclinical problems in SACs, leading to economic loss from suboptimal production of fibre, meat and/or leather [3]. Farmers regularly administer various classes of anthelmintics to alpacas to control nematodes. Anthelmintic resistance has been reported in ruminants worldwide, very little is known about anthelmintic resistance in SACs [7,8,9]
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