In recent years Giardia duodenalis and Cryptosporidium parvum have been considered by some investigators to be important causes of diarrhea. The role of G. duodenalis as an enteropathogen in animals remains undetermined. Limited information is available concerning the effect of age and season on G. duodenalis and C. parvuni infection in calves. A year long prospective longitudinal study was conducted to determine the effect of age and a cross sectional study was conducted to determine the effect of season on infection rates and shedding intensity. Associations between Giardia and Cryptosporidium infections and abnormal stools were also determined. A separate case control study was conducted to investigate the association between Giardia, and Cryptosporidium infections and diarrhea in young dogs admitted to two animal shelters.

Giardia and Cryptosporidium cysts/oocysts were frequently identified in fecal samples from calves. Giardia cysts and Cryptosporidium oocysts were found in 54% and 24% of samples respectively from 1 day to 387 day-old calves. About 80% of individual calves had at least one positive sample for Giardia and Cryptosporidium infections.

Age was a significant factor in determining Giardia and Cryptosporidium infections and cyst/oocyst shedding levels (P< 0.01). The highest proportion of Cryptosporidium-positive samples was from 2 week-old calves. Giardia cysts were most frequently identified in samples from 8 week-old calves and about 80% of samples had cysts.

Giardia cysts were less frequently found in samples collected in winter than in other seasons (P <0.01). Detection of Cryptosporidium oocysts was not influenced by season. Among infected calves, Cryptosporidium oocyst shedding levels were higher in winter than in other seasons.

Giardia cysts were more frequently found in normal stools than in abnormal su)ols (P 0.01). Lrvptosporu.tiiein oocysts were more frequently identified in abnormal stools than in normal stools (0R3.5; P <0.001) and among infected calves higher oocyst shedding levels were observed in abnormal stools than in normal stools (P <0.01).
No association between Giardia cyst and Cryptosporidiuni oocyst shedding levels and diarrhea was observed in the young dogs studied. Giardia infections were more common in females than in male dogs (P- 0.03). Gender was not associated with i3pru,,poriduun infections (Pr- 0.32). but higher mean oocyst shedding was observed in males than in females (P < 0.01 ). Mean body condition scores of cases was slightly lower than that of control dogs (P= 0.04).