Excretion of Cryptosporidium oocysts by goats in relation to age and season in the dry zone of Sri Lanka.

Pattern of Cryptosporidium oocyst shedding in relation to age and season was investigated monthly from May 1999 to April 2000 in three groups (24 goats per group) of naturally infected goats (from 1 month of age). The three groups designated 1, 2 and 3 were studied for 12, 6 and 3 months, respectively. An association between Cryptosporidium oocyst counts and age was demonstrated. In Group 1, oocyst excretion in the first, second and fourth months of age were significantly higher than that in 6, 7, 8, 9 and 12 months of age (p<0.01), whereas in Group 2, oocyst excretion in the first month of age was significantly higher than that in 2, 4, 5 and 6 months of age (p<0.01). The 3-month observations made in Group 3 showed high oocyst excretion during 1 and 3 months of age. The mean maximum count for Group 1 was 592 oocyst per gram of feces when the animals were 2 months old, while in Groups 2 and 3, this was observed at 3 months of age and the oocyst counts were 787 and 520, respectively. A close association between the prevalence of the Cryptosporidium infection and age of the animal was also observed (p<0.01). At least one-third of the Group 1 animals were excreting Cryptosporidium oocysts during the first 5 months of age. Goats excreted Cryptosporidium oocysts irrespective of the dry or rainy season. The long periods of Cryptosporidium oocyst shedding by goats may have implications for the epidemiology of the disease in susceptible hosts.