Duration of naturally acquired giardiosis and cryptosporidiosis in dairy calves and their association with diarrhea

Objective-To determine duration of infection and association of infection w ith diarrhea for dairy calves with naturally acquired cryptosporidiosis and giardiosis. Design-Cohort study. Animals-20 Holstein calves on a single dairy farm. Procedure-Fecal samples were collected 3 times/wk for the first 45 days aft er birth, then weekly until calves were 120 days old and examined for Giard ia duodenalis cysts and Cryptosporidium parvum oocysts, Calves were monitor ed for diarrhea during the first 45 days after birth; during each episode o f diarrhea, fecal samples were examined for parasitic, bacterial, and viral pathogens. Results-All 20 calves shed Giardia cysts and Cryptosporidium oocysts at som e time during the study. Mean ages at which Giardia cysts and Cryptosporidi um oocysts were first detected were 31.5 and 16.3 days, respectively. Mean number of Giardia cysts in feces remained high throughout the study, wherea s Cryptosporidium oocysts decreased to low or undetectable numbers 2 weeks after infection. Eighteen calves had a total of 38 episodes of diarrhea dur ing the first 45 days after birth. Giardia duodenalis was the only pathogen identified during 6 (16%) episodes, C parvum was the only pathogen identif ied during 9 (24%) episodes, and G duodenalis and C parvum were identified together during 10 (26%) episodes. Conclusions-Prevalences of giardiosis and cryptosporidiosis were high in th ese calves, and both parasites were associated with development of diarrhea . Cryptosporidium parvum was an important pathogen when calves were < 1 mon th old, but G duodenalis was more important when calves were older, Calves cleared C parvum infections within 2 weeks; however, G duodenalis infection s became chronic in these calves.