PATTERN OF CRYPTOSPORIDIUM-PARVUM OOCYST EXCRETION BY EXPERIMENTALLY INFECTED-DOGS

Six 6-week-old Beagle dogs were fed Cryptosporidium parvum oocysts of calf origin. All 6 dogs shed oocysts in faeces. Greater numbers of ooc ysts were detected with a Weber concentration technique (formalin-ethy l acetate extraction and NaCl centrifugal flotation) stained with eith er fluorescent antibody or modified Ziehl-Neelsen than with other form alin-ether or -ethyl acetate extraction methods. Oocyst numbers g(-1) of faeces rose from days 3 to 5 to a first and highest peak lasting to days 7-9, and 5 of the 6 dogs passed oocysts for at feast 80 days. Ho wever, the numbers of oocysts detected in the dogs' faeces were low, o nly 16.1% of the samples in the first month after infection and 2.5% t hereafter contained greater than or equal to 10 000 oocysts g(-1) of f aeces. Oocyst production was cyclical, with 19.3% of samples negative in the first month after infection and 42.5% thereafter. (C) 1997 Aust ralian Society for Parasitology. Published by Elsevier Science Ltd.