Submitted to: American Association of Veterinary Parasitologists Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 5/11/2007
Publication Date: 7/15/2007
Citation: Trout, J.M., Santin, M., Fayer, R. 2007. A longitudinal study of Giardia duodenalis genotypes in dairy cows. American Association of Veterinary Parasitologists Proceedings, Washington, DC, July 14-18, 2007. Interpretive Summary:
Technical Abstract: Fecal samples were collected from 30 dairy cows on the same farm beginning at 1 week of age and continuing for 2 years. Samples were collected weekly from 1 wk to 8 wks of age, bi-weekly from 2 mo to 6 mo of age and monthly thereafter. The samples were concentrated and cleaned of fecal debris on a CsCl gradient and analyzed for the presence of Giardia spp. by both immunofluorescent microscopy (IFA) and a PCR targeting a portion of the ssu-rRNA gene. All PCR positive samples were subjected to DNA sequencing to determine the genotypes that were present. Overall, PCR detected more positive samples than IFA. Assemblage E was the predominate genotype in the younger animals, with Assemblage A first being detected at 14 wks of age. The point prevalence of Assemblage E peaked at 83% in 4 and 5 week old calves, and the cumulative prevalence reached 100%. The point prevalence of Assemblage A peaked at 20% in 18 wk old animals, and the cumulative prevalence reached 70%. Some animals were infected with both assemblages, either consecutively or concurrently. The prevalence of both genotypes was lower in older animals, however, this could be due to cyst excretion becoming intermittant. The data shows that calves acquire Giardia infections early in life, with Assemblage E being most common. However, infections with Assemblage A can follow or occur concurrently with Assemblage E infections. The age distribution of the two Assemblages suggests that the zoonotic risk of Giardia from cattle could be greater in older animals than in younger ones.