Isoenzyme typing was used to study a number of oocyst isolates of Cryptosporidium parvum from different geographical locations and of human or animal origin. All isolates showed identical enzyme motility when glucose phosphate isomerase (GPI; 23 isolates tested) or lactate dehydrogenases (LDH; 20 isolates tested) was assayed. However, two isoenzyme forms were observed with phosphoglucomutase (PGM; 9 animal isolates showed one form, while 8/9 human isolates showed a second form) and hexokinase (HK; 4 human isolates showed one form and 6 animal isolates showed a second form). Thus, PGM and HK each exhibit 2 isoenzymes corresponding to 2 parasite populations associated with separate hosts. The data from this study, plus supportive evidence obtained by different methods and by independent researchers, lend support to the hypothesis that separate cycles of transmission of C. parvum may exist within human and animal hosts.
Statistical data were collected from 20 sheep flocks in which enzootic abortion of ewes (EAE) was diagnosed by examination of fetal material and maternal blood samples. The abortion rate in the 10,645 ewes in these flocks was 7.6 per cent. Thirteen of the flocks were fully vaccinated against EAE but the abortion rate in these was still in the order of 6.5 per cent. EAE was the major cause of the problem as ascertained from the laboratory examination of samples from a wide range of cases of abortion. There is therefore evidence that, in some flocks in south east Scotland, the efficacy of the vaccine against EAE is unsatisfactory. The reasons for this are discussed.
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