ZOONOTIC PARASITES AFFECTING FOOD SAFETY AND PUBLIC HEALTH
Location: Environmental Microbial and Food Safety Laboratory
Title: Prevalence of Giardia duodenalis assemblages in weaned cattle on cow-calf operations in the United States
Submitted to: Veterinary Parasitology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 22, 2011
Publication Date: January 1, 2012
Citation: Santin, M., Dargatz, Fayer, R. 2012. Prevalence of Giardia duodenalis assemblages in weaned cattle on cow-calf operations in the United States. Veterinary Parasitology. 183:231-236.
Interpretive Summary: This study examined feces from 819 beef calves in 20 states for the presence of the parasite Giardia duodenalis using molecular methods for detection. The prevalence at each of 49 locations examined ranged from 0 (no calves infected) to 100% (all calves infected). The highest prevalence of infection was found in operations in Georgia, Idaho, Nebraska, and Iowa with 100, 90, 87.5, and 85% of the animals infected, respectively. Two genetic types were found, Assemblage E which is known to infect only hooved livestock, and Assemblage which infects many animals and humans. Assemblage E was detected in 31.7% of the calves whereas Assemblage A was detected in 1.2% of calves. Although the presence of Assemblage A in these food animals poses a potential concern for environmental and food safety the prevalence is low and related illness in persons has not been reported.
To determine the prevalence of Giardia duodenalis in weaned beef calves in cow-calf operations in the United States, fecal specimens were collected from 819 calves (6 to18 months of age) in 20 states from 49 locations. After cleaning and concentration procedures to maximize the potential recovery of cysts from feces, DNA was extracted from each of the 819 specimens. The presence of G. duodenalis was determined by nested PCR of a fragment of the SSU rRNA gene. All positive PCR products were subjected to sequence analysis. The overall prevalence of Giardia was 33.5 % with prevalence ranging from 0 to 100% among operations. The highest prevalence of infected beef calves was found in cow-calf operations from Georgia, Idaho, Nebraska, and Iowa with 100, 90, 87.5, and 85% of the animals infected, respectively. Giardia was not detected in 7 operations, 2 cow-calf operations each from Louisiana and Oklahoma, and 1 each from Texas, South Dakota, and California. The molecular analysis of the 274 Giardia-positive samples identified Assemblage E in 260 (31.7%) and Assemblage A in 10 (1.2%). In four calves from a farm in Nebraska a mixed infection with Assemblage A and E was observed. The potentially zoonotic assemblage A was detected in specimens from four operations in Nebraska, and one in each in Iowa and Oregon. These findings indicate that most G. duodenalis found in beef cattle was Assemblage E which represents no known zoonotic threat. However, the presence of Assemblage A in a small number of animals poses a poses a potential risk of infection to humans.