PROTOZOAN PARASITES AFFECTING FOOD ANIMALS, FOOD SAFETY, AND PUBLIC HEALTH
Title: Giardia duodenalis assemblages in weaned cattle on cow-calf operations in the United States
Submitted to: American Society of Parasitologists
Publication Type: Abstract Only
Publication Acceptance Date: February 25, 2011
Publication Date: May 20, 2011
Citation: Santin, M., Dargatz, D., Fayer, R. 2011. Giardia duodenalis assemblages in weaned cattle on cow-calf operations in the United States. American Society of Parasitologists.
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, fecal specimens were collected from 819 6- to18-month-old calves in 20 states. After cleaning and concentrating cysts from feces, DNA was extracted from each specimen. 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 49 operations. The highest prevalence of infection was found in 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 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%). Four calves from Nebraska had a mixed infection with Assemblages A and E. The potentially zoonotic assemblage A was detected in specimens from 4 operations in Nebraska, and 1 each in Iowa and Oregon. These findings indicate that most G. duodenalis found in beef calves was Assemblage E, presenting no known zoonotic threat. However, the presence of Assemblage A in a small number of animals poses a potential risk for human infection.