Submitted to: Veterinary Parasitology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/1/2004
Publication Date: 8/1/2004
Citation: Trout, J.M., Santin, M., Greiner, E., Fayer, R. 2004. Prevalence of giardia duodenalis genotype in pre-weaned dairy calves. Veterinary Parasitology. 124:179-186
Interpretive Summary: Giardia duodenalis is a group of morphologically identical organisms that can infect a variety of mammals. Within this species group, there are different genotypes or assemblages that have different host ranges. Assemblages A and B are found in humans and other mammals. Assemblage E is found only in hoofed-livestock. Recently Assemblage A Giardia has been reported in cattle. This study examined the prevalence of Giardia genotypes in dairy calves from VT, NY, PA, MD, VA, NC, and FL. Assemblage A Giardia was found on 7 of 14 farms tested, and accounted for 15% of the Giardia isolates, with the remainder being Assmeblage E. Thus dairy calves must be considered a source of Giardia that is potentially infectious for humans.
Technical Abstract: To determine the prevalence of Giardia genotypes in pre-weaned dairy calves, fecal samples were collected from a minimum of 18 one to eight week-old dairy calves per farm on two farms in each of the following states: VT, NY, PA, MD, VA, NC, and FL. Samples were cleaned of fecal debris and concentrated using CsCl density gradient centrifugation. After centrifugation, samples were stained and examined by immunofluorescent microscopy and also subjected to PCR and gene sequence analysis. Prevalence ranged from 13% on a MD farm to 88% on a VT farm, with an average prevalence over all farms of 44%. Gene sequence analysis of the TPI, B-giardin and 16S rRNA genes revealed 84% of the positive samples to be Assemblage E, while 16% were Assemblage A, although the percentages of these genotypes varied significantly from farm to farm, with some farm having no Assemblage A Giardia. Thus while a majority of the calves were infected with a genotype that is not known to be infectious for humans, calves on 7 of 14 farms did harbor Assemblage A Giardia. Therefore calves should be considered as a potential source of human infectious cysts in the environment.