ARS | Publication request: A large scale molecular study of Giardia duodenalis in horses

Submitted to: Veterinary Parasitology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 11, 2013
Publication Date: N/A

Interpretive Summary: Giardia duodenalis is a widespread intestinal parasite of mammals and can cause serious illness in humans. Although Giardia was first reported as a parasite of horses in South Africa in1921 nearly all subsequent reports of giardiasis in horses are based on microscopic studies in which cysts were observed in feces. However, molecular characterization has identified seven major assemblages (A-G) of G. duodenalis that have different host ranges. Recently two studies involving a very small number of horses have detected assemblages A, B, and E in horses. Because assemblages A and B are known to infect humans, horses could represent a reservoir of G. duodenalis with the potential to cause disease in humans through direct contact or by contamination of food and water supplies, or contamination of the environment and potentially affecting other domesticated animals. Therefore, the present study was undertaken to determine the prevalence of G. duodenalis in a large number of horses, and to determine the assemblages present. Utilizing 4 gene sequences to confirm identity, Assemblages A and B, which are potentially infectious for humans, were identified in 34 of the 195 horses examined. This confirms the previous observation that horses may serve as a reservoir of Giardia infectious to humans. This information will be useful to other scientists, veterinarians, and regulatory agencies.

Technical Abstract: The prevalence of Giardia duodenalis genotypes in horses is poorly known. The present study examined feces from 195 horses, 1 month to 17 years of age, in 4 locations in Colombia. Prevalence of infection was determined by PCR and all positives were sequenced to determine the genotypes. Thirty four (17.4%) horses were found positive. The prevalence was higher (21.1%) in horses <1 year of age than in horses > 1yr of age (15.1%) and was higher in female horses (18.9%) than in male horses (15.1%). Molecular characterization using the beta giardin (bg), glutamate dehydrogenase (gdh), triose phosphate isomerase (tpi), and small subunit ribosomal RNA (ssurRNA) genes identified G. duodenalis Assemblages A and B, the assemblages regarded as zoonotic.