Kryptosporidieinfektion hos nötkreatur
utvärdering av en ny metod för påvisande av subklinisk infektion
Cryptosporidium parvum is a protozoan parasite causing diarrhoea in many different animal species including cattle and man. It is an important enteric pathogen in neonatal calves and it is the second most common pathogen found in diarrhoeic calves in Sweden. Subclinically infected adult cattle have, in international studies, been shown to shed a low number of oocysts in faeces and this has been recognised as a potential source of infection for new-born calves. The detection methods used for diagnostic purposes are based on microscopic investigation of faecal smears. These methods have a fairly low sensitivity and samples from subclinically infected cattle have to be concentrated before analysis.
The purpose of this study was to establish and evaluate a sodiumchloride-flotation method for concentration of C. parvum oocysts in faecal samples and to use the method to investigate the occurrence of subclinical C. parvum infection in a dairy herd.
Faecal samples were collected from 5 cows, 5 calves without diarrhoea and 5 calves with diarrhoea. To 1 gram of each sample 72 oocysts were added. This was repeated twice for the samples from calves with diarrhoea and cows. Unspiked and spiked samples were treated by the flotation method and analysed using immunofluorescence microscopy. The sensitivity of the method was 80 % for the samples from calves with diarrhoea spiked with 72 oocysts/gram. 70 % and 0 % sensitivity was shown for the samples of adult cattle and calves without diarrhoea, respectively, at this oocyst level. The recovery rate for faeces from adult cattle and calf-diarrhoea was 52 % and 55 % respectively.
In the second part of the study faecal samples were collected from 20 adult cattle in a dairy herd known to have cryptosporidiosis among the calves. The herd comprised 200 cows and were situated in the south of Sweden. When the samples were concentrated and analysed for presence of C. parvum oocysts, oocysts were found in 2 of the samples.
The results showed that the concentration method can be used to detect low levels of oocysts in faeces from adult cattle and from calves with diarrhoea. The result from the samples collected in the dairy herd confirms that there are subclinically infected adult cattle in Sweden that shed oocysts.