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United States Department of Agriculture

Agricultural Research Service

Research Project: PROTOZOAN PARASITES AFFECTING FOOD ANIMALS, FOOD SAFETY, AND PUBLIC HEALTH Title: Prevalence and molecular characterization of Cryptosporidium and Giardia species and genotypes in sheep in Maryland

Authors
item Santin-Duran, Monica
item Fayer, Ronald
item Trout, James

Submitted to: Veterinary Parasitology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 23, 2007
Publication Date: April 10, 2007
Citation: Santin, M., Fayer, R., Trout, J.M. 2007. Prevalence and molecular characterization of Cryptosporidium and Giardia species and genotypes in sheep in Maryland. Veterinary Parasitology. 146(2007):17-24.

Interpretive Summary: In the United Kingdom and Australia sheep have been implicated as sources of two parasitic diseases that affect humans. There have been no molecularly based studies in North America to confirm the importance of sheep with regard to these human pathogens. Therefore, a study was undertaken to investigate the prevalence of Cryptosporidium and Giardia in sheep on a farm in Maryland. Fecal samples were collected from 32 pregnant ewes 1, 2, and 3 days after lambing, and from each of their lambs at days 7, 14, and 21 after birth. Samples were analyzed using microscopy and the Polymerase Chain Reaction (PCR). The prevalence of Cryptosporidium in ewes and lambs was 25 and 77.4%, respectively. Three species/genotypes of Cryptosporidium were identified: C. parvum, Cryptosporidium cervine genotype, and a novel Cryptosporidium genotype (ovine genotype). Cryptosporidium parvum as well as the cervine genotype have been reported worldwide infecting humans. The ovine genotype is reported here for the first time. The prevalence of Giardia in ewes and lambs was 12 and 4%, respectively. with all but one of the positive sheep infected with Giardia Assemblage E, a type that is not infectious for humans. The one ewe was excreting assemblage A, a known human pathogen. Ewes and lambs should be considered as a potential source of human infectious cysts/oocyst in the environment.

Technical Abstract: In the United Kingdom and Australia sheep have been implicated as sources of Cryptosporidium and Giardia that affect humans but no such studies have been conducted in North America. Therefore, a study was undertaken to investigate their prevalence in sheep on a farm in Maryland in which feces were collected from 32 pregnant ewes 1, 2, and 3 days after parturition, and from each of their lambs 7, 14, and 21 days after birth. Samples were examined by immunofluorescence microscopy to determine the presence of Cryptosporidium oocysts and Giardia cysts and subjected to DNA extraction, PCR and gene sequence analysis to determine the species and genotypes. PCR consistently detected higher numbers of positive specimens- the prevalence of Cryptosporidium in ewes and lambs being 25 and 77.4%, respectively. Three species/genotypes of Cryptosporidium were identified as: C. parvum, Cryptosporidium cervine genotype, and a novel Cryptosporidium genotype (ovine genotype). Cryptosporidium parvum and the cervine genotype have been reported worldwide infecting humans. The ovine genotype was reported for the first time. The prevalence of Giardia in ewes and lambs was 12 and 4%, respectively, most infected with Assemblage E which is not zoonotic, one ewe infected with zoonotic assemblage A. Two lambs infected with C. parvum and one ewe infected with G. duodenalis assemblage A represents a low prevalence of these zoonoses. However, high numbers of sheep with the zoonotic cervine genotype indicates that sheep should be considered as a potential source of human pathogens in the environment.

Last Modified: 8/1/2014