On Schistosoma curassoni, S. haematobium and S. bovis from Senegal: development in Mesocricetus auratus, compatibility with species of Bulinus and their enzymes

Abstract

A comparative study on the development of Senegalese isolates of Schistosoma curassoni, S. haematobium and S. bovis in hamsters is reported, together with the compatibility of these parasites with Bulinus spp. and enzymes of adult worms.

The mean worm return from 35 hamsters exposed to 100 cercariae each of S. curassoni was 11·5%, and of these 54% were paired, the remainder were single males. The growth and maturation of the worms were recorded from 40 to 100 days. The cross-over point (when paired females are of the same length as paired males) was reached at 42 days post-infection when the worms averaged 13·7 mm in length. The majority of tissue eggs (84·5%) were recovered from the liver, compared with 11% in the colon, 2·5% in the caecum and 1·6% in the small intestine. Estimates of the fecundity of paired females averaged 167 eggs/day per female worm. Snail-infection experiments showed S. curassoni to be compatible with B. umbilicatus, marginally compatible with B. senegalensis and incompatible with B. forskalii, B. jousseaumei and B. guernei. S. curassoni is marginally compatible with B. bavayi, B. beccarii, B. camerunensis and B. cernicus, (members of the B. forskalii group) and B. obtusispira, a species placed in the B. africanus group. The mean worm return from 35 hamsters exposed to 100 cercariae each of S. haematobium was 9·1%, and of these 46·7% were paired, 42·1% were single male worms and the remaining 11·2% were single female worms. The growth of the worms was recorded from 40 to 100 days, the maturation from 60 to 100 days. The cross-over point was reached at about 62 days post-infection when the worms averaged 8·3 mm long. The majority of tissue eggs (95·3%) was recovered from the liver, compared with 2·8% and 1·9% from the small intestine and colon, respectively. Estimates showed that the average fecundity of paired females was 86 eggs/day per female worm. Snail-infection experiments showed that S. haematobium is marginally compatible with B. senegalensis, but incompatible with B. guernei and B. forskalii. The mean worm return from 35 hamsters exposed to 100 cercariae each of S. bovis was 26·6%, and of these 53·1% were paired, the remainder were single males. The growth and maturation of worms were recorded from 40 to 100 days. The cross-over point was reached just before 40 days: at 40 days the paired males averaged 9·5 mm in length, the paired female 9·6 mm in length. The majority of eggs (53·1%) was recovered from the liver, compared with 20·7% from the small intestine and 19·8% from the colon.

Estimates of the fecundity of paired females averaged 95 eggs/day per female worm. Snail-infection experiments showed S. bovis to be compatible with B. guernei, fairly compatible with B. forskalii, and marginally compatible with B. umbilicatus. B. senegalensis appeared to be sensitive to S. bovis under laboratory conditions with large numbers dying after one week of exposure.

Enzymes in 3017 extracts of adult schistosomes, obtained from natural and laboratory infections, have been analysed by isoelectric focusing. Enzymes studied include glucose 6-phosphate dehydrogenase (G6PDH), phosphoglucomutase (PGM), lactate dehydrogenase (LDH), acid phosphatase (AcP), malate dehydrogenase (MDH), hexokinase (HK) and glucose phosphate isomerase (GPI). S. bovis was clearly differentiated from S. haematobium by patterns of G6PDH, GPI, HK and AcP. Similarly, S. bovis and S. curassoni were distinguishable by the different patterns of PGM, GPI, HK and AcP. S. haematobium and S. curassoni were differentiated by patterns of PGM and HK. Heterogeneity was seen in all species. In a natural infection of a sheep S. bovis and S. curassoni were found paired together.