On factors possibly restricting the distribution ofSchistosoma intercalatum Fisher, 1934

Summary

Two hypotheses have been postulated explaining the limited distribution ofSchistosoma intercalatum.

The first hypothesis is correlated with physical factors and behaviour of cercariae. Histochemical and ultrastructural studies have shown that in response to increased temperature change the cercariae ofS. intercalatum form aggregates, unlike other schistosome cercariae of man, which are noninfective to the definitive host. The aggregates are formed by the release of the adhesive post-acetabular gland secretion which causes the cercariae to stick together. It is suggested that ifS. intercalatum spread from streams within tropical rain forest to pools and laybys of streams in the savannah, cercariae would be subjected to greater daily temperature changes thus triggering the release of post-acetabular gland secretion, thereby impairing invasion of the definitive host.

The second hypothesis is based on the natural occurrence of hybridisation betweenS. intercalatum andSchistosoma haematobium. With some strains of these two species there are no genetical isolating mechanisms. It is suggested that ifS. intercalatum extended into a savannah environment from tropical rain forest, hybridisation betweenS. intercalatum andS. haematobium would eventually occur. Experimental studies indicate that probably, as a result of introgressive hybridisation, a new strain ofS. haematobium would eventually supersede the originalS. intercalatum.

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References

  1. Appleton, C.C.: Observations on the thermal regime of a stream in the Eastern Transvaal, with reference to certain aquatic Pulmonata. S. Afr. J. Sci.72, 20–23 (1976)

    Google Scholar 

  2. Austin, F.G., Stirewalt, M.A., Danziger, R.E.:Schistosoma mansoni: stimulatory effect of rat skin lipid fractions on cercarial penetration behaviour. Exp. Parasitol.31, 217–224 (1972)

    Google Scholar 

  3. Bolwig, N.: An experimental study of the behaviour and host-recognition in schistosoma cercariae. S. Afr. J. Sci.51, 338–344 (1955)

    Google Scholar 

  4. Deschiens, R., Delas, S.: L'extension géographique de la bilharziose àSchistosoma intercalatum en Afrique tropicale. Trans. roy. Soc. trop. Med. Hyg.63, (Suppl.) 57–65 (1969)

    Google Scholar 

  5. Pitchford, R.J., Du Toit, J.F.: The shedding pattern of three little known African schistosomes under outdoor conditions. Ann. trop. Med. Parasitol.70, 181–187 (1976)

    Google Scholar 

  6. Schwetz, J.: Role of wild rats and domestic rats (Rattus rattus) in schistosomiasis of man. Trans. roy. Soc. trop. Med. Hyg.50, 275–282 (1956)

    Google Scholar 

  7. Southgate, V.R.: Observations on the epidermis of the miracidium and on the formation of the tegument of the sporocyst ofFasciola hepatica. Parasitology,61, 177–190 (1970)

    Google Scholar 

  8. Southgate, V.R., van Wijk, H.B., Wright, C.A.: Schistosomiasis at Loum, Cameroon:Schistosoma haematobium, S. intercalatum and their natural hybrid. Z. Parasitenkd.49, 145–159 (1976)

    Google Scholar 

  9. Wright, C.A., Southgate, V.R., Knowles, R.J.: What isSchistosoma intercalatum Fisher, 1934? Trans. roy. Soc. trop. Med. Hyg.66, 28–64 (1972)

    Google Scholar 

  10. Wright, C.A., Knowles, R.J.: Studies onSchistosoma haematobium in the laboratory III. Strains from Iran, Mauritius and Ghana. Trans. roy. Soc. trop. Med. Hyg.66, 108–118 (1972)

    Google Scholar 

  11. Wright, C.A., Southgate, V.R., van Wijk, H.B., Moore, P.J.: Hybrids betweenSchistosoma haematobium andSchistosoma intercalatum in Cameroon. Trans. roy. Soc. trop. Med. Hyg.68, 413–414 (1974)

    Google Scholar 

  12. Wright, C.A., Southgate, V.R.: Hybridisation of schistosomes and some of its implications. In: Genetic aspects of host-parasite relationships. A.E.R. Taylor and R. Muller eds., Symp. Brit. Soc. Parasitol.14, 55–86 (1976)

  13. Van Wijk, H.B.:Schistosoma intercalatum infection in schoolchildren of Loum, Cameroon. Trop. geogr. Med.21, 375–382 (1969)

    Google Scholar 

  14. Van Wijk, H.B.:Schistosoma intercalatum infection in Mungo Department, Cameroon. Thesis, University of Amsterdam, 1–154 (1975)

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Southgate, V.R. On factors possibly restricting the distribution ofSchistosoma intercalatum Fisher, 1934. Z. Parasitenkd. 56, 183–193 (1978). https://doi.org/10.1007/BF00930749

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Keywords

  • Experimental Study
  • Temperature Change
  • Daily Temperature
  • Rain Forest
  • Physical Factor