干旱区生态环境知识资源中心

The desert hamster (Phodopus roborovskii Satunin, 1903) represents a new host of Cryptosporidium muris Tyzzer (1907), 1910. This very first finding was made in the laboratories of the National Veterinary Institute, Prague, Czech Republic. In September 1994 three 11-month and one 3-month desert hamsters were sent for laboratory examination. Parasitological examination post mortem of a 9-month desert hamster revealed ’’large’’ Cryptosporidium oocysts in excrements as well as in the contents of intestines. In all animals in which autopsy was carried out congestion of lungs, spleen and liver, acute catarrhal inflammation and flatulences in portions of gut were observed. Presence of morphologically identical oocysts of cryptosporidia was confirmed in the same group of desert hamsters also during parasitological reexamination carried out in October 1994. Applying the methods according to Breza (1957) and Pavlasek (1991) oocysts of the protozoon under study were detected in pooled samples of excrements of 3, 4, 5, 10 and 11-month animals. Two out of four live 2-3-month desert hamsters were infected naturally, both parents (10-11 months old), sent by the owner to our laboratory to be used for further observation. Both adult animals showed slight tremor, somnolence, rough hair and recumbent position, the male showed paresis of pelvic limbs. For four days in the laboratory conditions excrements of all six live desert hamsters, the interval being 2-12 hours, were examined and in four of them the finding of oocysts of the protozoon was repeatedly positive. Adult animals were euthanasied. From the internal (heart, lungs, liver, spleen, kidneys, brain) organs and from the different parts of stomach and from the full length of small intestine (in the distance of 1-1.5 cm), of caecum and colon impressions and scrapings of mucous epithelium were made and, after fixation by methanol, stained according to Giemsa. In examining smear preparations endogenous developmental stages of Cryptosporidium were detected, sexual stages prevailing, only in the stomach of both desert hamsters. Oocysts of the protozoon were found in higher numbers (1-2 oocysts within one observation field at 450x magnification in examining native preparation) in stomach contents, sporadically in digesta from particular portions of the gut and, obviously, in formed excrements in the colon of animals. After measuring 100 oocysts (50 oocysts obtained from the stomach contents and the same number isolated from excrements of live naturally infected desert hamsters) their size in native preparations was 7.6-8.8 x 4.8-6.08 mu m with the mean of 8.07 x 5.3 mu m. The size most frequently observed was 8.0 x 4.8 mu m. The index of the oocysts was - length/width 1.3-1.7 with the mean of 1.5; width/length 0.59-0.77 with the mean of 0.65. On the basis of localization of endogenous developmental stages and of morphometrical parameters of cryptosporidial oocysts, by comparing our findings with the data of authors cited in the paper who have given information on occurrence of the so called ’’large’’ oocysts of the protozoon in cattle, house rats and mice and also in view of the knowledge gained until now about the species spectrum of coccidia of the genus Cryptosporidium it comes out that desert hamsters have been infected with the C. muris species. At present further studies are going on, using the group of duration 30 desert hamsters, and other observations are carried out aimed at discovering the length of prepatent and patent period of naturally infected animals, studying specificity and pathogenicity of this protozoon.