Spontaneous Cryptosporidium infection in weaned rabbits

The first occurrence of Cryptosporidium parvum Tyzzer, 1912 in broiler rabbits in the Czech Republic is reported. The protozoon was determined on the basis of morphometrical parameters of oocysts and of localization of endogenous developmental stages. The dynamics of natural Cryptosporidium infection was studied in a group of 72 young rabbits after weaning (their age ranging from 23-33 to 82-92 days) obtained from six large flocks and used in a feeding experiment. C. parvum was found in rabbits from four farms (Tab. I). Animals under observation were divided into 9 subgroups according to the genotype (Hyla 2000, California White, crosses of New Zealand x California, New Zealand White, Cunistar and Zika) as well as according to the farm of origin. The animals were housed in 28 cages under the conditions of two-floor cage technology. The upper floor consisted of cages housing three head, the lower floor two head each. The animals were fed ad libitum with commercial feed mixture (till the average age of 64.days supplemented with Robenidin as coccidiostat). During the first 10 days of observation pooled samples of droppings from each cage were examinated by flotation-centrifugation method according to Breza (1957) and Pavlasek (1991) in the intervals of three to four days, later one-week intervals. Post mortem scrapings from mucous epithelium taken from young rabbits were examinated (to reveal endogenous developmental stages of C. parvum) together with digesta (to detect oocysts of the protozoon) taken from the full length of the small intestine using method of native preparations and Giemsa stain. In one 37-day dead animal the small and large intestines were examined histologically. The maximum number of young rabbits infected with C. parvum were 30-40 and 33-43 days old (Fig. 1). In animals of this age category the oocysts of the protozoon were found in pooled samples in 11 and 12 cages (39.3 and 42.9%) from totally 28 cages under study. In rabbits of more than 50 days of age the occurrence of infection was significantly decreased (3.7%). During the experiment seven rabbits (9.7%) died; six of them (8.3%) at the age of 30-40 days. All these naturally infected and dead animals represented cases of monoinfection with C. parvum. The major clinical signs were typical diarrhoea lasting 3-5 days, inappetency, apathia, lethargy, prominent signs of exhaustion followed by dehydration of the organism. Atrophy of villi of the ileum in one of young rabbits was found histologically. Table II presents concrete data on significantly lower body weights (the decrease being 7-61.5%) as compared with rabbits of the same age not infected with cryptosporidia. It was not possible to evaluate objectively the differences in susceptibility to C. parvum infection between the individual genotypes of rabbits. As was found in the course of our further studies (unpublished data) a possible source of infection of young rabbits can be represented by their mothers in which oocysts are excreted sporadically shortly before parturition and during several days after it. Cryptosporidium infection (cryptosporidiosis) in flocks of broiler rabbits is taken as a new protozoal disease in the Czech Republic and C. parvum as one of possible agents in cases of disorders of digestive tract, namely in rabbits after weaning.