During the kidding season between January and April 2003, 10 farms were selected and divided into two groups of five. The farms in group A had had serious diarrhoeal illness and losses in neonatal kids the previous year, and there were Cryptosporidium parvum infections in kids associated with diarrhoea during the survey. On the farms in group B, there was no history of diarrhoeal disease the previous year and neither C parvum oocysts nor diarrhoea were detected in neonatal kids during the survey. Faecal samples were collected once from 10 adult goats aged between one and seven years on each farm. To assess more accurately the pattern of output of oocysts of C parvum and cysts of Giardia duodenalis by periparturient adult goats, one farm was selected from each group, faecal samples were collected weekly before and after kidding from 12 goats on the farm in group A and from 10 goats on the farm in group B. There was no significant difference in the prevalence of G duodenalis cysts between the group A farms (14 per cent) and the group B farms (12 per cent), and the numbers of cysts excreted ranged from 143 to 400 cysts per gram of faeces (cpg) on the group A farms and 72 to 334 cpg on the group B farms. There was a significant difference (P=0·03) in the prevalence of C parvum oocysts at the group level between the group A farms (20 per cent) and the group B farms (6 per cent). All the adult goats excreted cysts and oocysts at some date around the kidding period; the number of animals excreting cysts of G duodenalis or oocysts of C parvum increased when they gave birth, and seven to 10 times more cysts and oocysts were shed in the three weeks around kidding than in the period more than three weeks from kidding (P<0·001).
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↵Dr Castro-Hermida is also at Laboratorio de Parasitología, Departmento de Microbiología y Parasitología, Facultad de Farmacia, Universidad de Santiago de Compostela, Avenida de Vigo s/n, 15782 Santiago de Compostela, La Coruña, Galicia, Spain