Anthelmintic resistance in a herd of alpacas (Vicugna pacos)

In July and August of 2010, a series of 5 adult alpacas were presented to the University of Missouri, Veterinary Medical Teaching Hospital for severe anemia, hypoproteinemia, and weight loss (Table 1). Quantitative fecal egg counts revealed the presence of high numbers of strongyle-type eggs per gram of feces in 3 of the 5 animals (Table 1). These findings, in conjunction with anemia and hypoproteinemia, led to a presumptive diagnosis of haemonchosis. All of the animals were treated with whole blood transfusions. Each animal had been treated with an anthelmintic at or shortly before admission to the hospital (Table 1). Based on follow-up fecal egg counts performed 6 to 13 d (Table 1) after hospital admission it appeared that the parasites may have been resistant to fenbendazole (Panacur; Intervet-Schering Plough, Summit, New Jersey, USA) in 1 of the cases, whereas there was a > 95% reduction in the fecal egg count in an animal treated with pyrantel (Anthelban; IVX Animal Health, St. Joseph, Missouri, USA) and an animal treated with levamisole (Prohibit; Agri-Laboratories, St. Joseph, Missouri, USA). The remaining 2 animals had insufficient data to draw any preliminary conclusions about anthelmintic efficacy. These preliminary findings suggested that there might be resistance to fenbendazole in this herd. To further explore this suspicion, a herd investigation was conducted in September of 2010 to evaluate animal husbandry and efficacy of anthelmintics that were in common use on the farm. Table 1 Summary of data from patient records for 5 adult alpacas presented for severe anemia and weight loss