April 2014
Haemonchus contortus and camelids
By Lisa Williamson DVM
University of Georgia College of Veterinary Medicine
As is the case in sheep and goats, gastrointestinal parasites are a leading cause of illness and death in camelids. The blood-feeding nematode Haemonchus contortus is especially devastating in camelid herds living in endemic areas. Based on a survey conducted in the Athens, Georgia Diagnostic Laboratory last year, haemonchosis was the cause of death in 12% of the llama and alpacas submitted for necropsy [1].
Research conducted by the University of Georgia a few years ago on hundreds of llamas and alpacas living on 26 privately owned farms in the southeastern United States found that Haemonchus contortus was the most prevalent nematode parasite on the farms. Trichostrongylus colubriformis and Nematodirus spp. were the second and third most prevalent parasites, respectively.
Multi-drug resistance was documented in the Haemonchus contortus and Trichostrongylus colubriformis isolates from the llamas and alpacas. Nematodirus spp. were not evaluated for drug resistance. Similar to the anthelmintic profiles seen in sheep and goats in the southeastern United States, ivermectin and benzimidazole resistance was a common finding [2].
Many Haemonchus contortus isolates from camelids were sensitive to levamisole and moxidectin, however [2]. These findings underscore the importance of evaluating the efficacy of anthelmintics used on camelid farms to help manage gastrointestinal nematodes. A reasonable goal is to perform a larval developmental assay or a fecal egg count reduction test on the farm every 2-3 years.
Body condition scores and FAMACHA© scores collected on camelids living on the 26 farms were compared to packed cell volumes and fecal egg counts. Similar to what has been seen in other species, parasite burdens were not evenly distributed among the alpacas and llamas on any of the farms studied. Most herd mates had asymptomatic parasite burdens, but a small percentage of the herd showed signs of parasitism including suboptimal body condition, anemia, weakness, and loss of normal fecal consistency.
Camelids were more challenging to score using the FAMACHA© system than sheep and goats, because many animals resented having a hand placed on their foreheads.
Modification of the approach made scoring them easier. When the examiner approached each eye by sliding the hand up the face to the eye, most llamas and alpacas allowed their ocular globes to be retropulsed, and their lower eyelids to be everted during the FAMACHA© scoring process with little objection. Researchers concluded that the FAMACHA© system has good discriminatory value for detecting anemia associated with haemonchosis in camelids [3].
Further, body condition score was a good indicator of which camelids were harboring the most significant parasite burdens regardless of type. Alpacas and llamas in optimal-to-overweight categories harbored less parasites than camelids with suboptimal body condition scores. In summary, the FAMACHA© system can be used on camelid farms where Haemonchus contortus is a predominant parasite, to determine which camelids are most likely in need of anthelmintic treatment and which ones can be left untreated. Further, body condition score is also a very useful parameter to use when making selective anthelmintic treatment decisions.
References
[1] Edwards EE, Williamson LH, Storey BE, et al. Pathology of Haemonchus contortus in new world camelids in Georgia: a retrospective study (abstract). Science of Veterinary Medicine Symposium, Athens, Georgia, October 10, 2013.
[2] Storey BE, Williamson LH, Howell S, Kaplan RM. Prevalence of anthelmintic resistance in gastrointestinal parasites of South American camelids in the southeastern United States (abstract). World Association for the Advancement of Veterinary Parasitology, Buenos Aires, Argentina, August 21-25, 2011.
[3] Williamson LH, Storey R, Kaplan RM. Evaluation of the FAMACHA© system in South American Camelids (abstract). World Association for the Advancement of Veterinary Parasitology International Meeting, Calgary, Canada, August 8-13 2009.