Hostname: page-component-586b7cd67f-r5fsc Total loading time: 0 Render date: 2024-11-30T20:19:51.907Z Has data issue: false hasContentIssue false

A comparative evaluation of snail sampling and cercariometry to detect Schistosoma mansoni transmission in a large-scale, longitudinal field-study in Machakos, Kenya

Published online by Cambridge University Press:  06 April 2009

J. H. Ouma
Affiliation:
Division of Vector-borne Diseases, Ministry of Health, P.O. Box 20705, Nairobi, Kenya
R. F. Sturrock
Affiliation:
Department of Medical Parasitology, London School of Hygiene and Tropical Medicine, Keppel Street (Gower Street), London WC1E 7HT, England
R. K. Klumpp
Affiliation:
147 Laurel Street, Atherton, California 94025, USA
H. C. Kariuki
Affiliation:
Division of Vector-borne Diseases, Ministry of Health, P.O. Box 20705, Nairobi, Kenya

Summary

In an operational Schistosoma mansoni field-study in an area of about 20 km (population approximately 8000), transmission detection by simple snail sampling was compared with cercariometry. Between 1985 and 1987, 62 field sites were sampled at fortnightly intervals. Of a total of 2758 field observations, 89.8% gave full snail data; 64.4% full cercarial data; and 61.7% complete data for both methods. The complete data sets showed significant but not strong correlations between Biomphalaria pfeifferi (total and infected with S. mansoni or other trematodes) and cercarial (S. mansoni and non-human) recoveries. Non-human (but not S. mansoni) cercarial recovery decreased with deteriorating cercariometry filter quality. Both snail and cercarial recoveries diminished significantly with increasing water flows at the time of collection. Many samples yielded infected snails or cercariae, but not both, and neither method detected significantly more transmission sites. The method of choice for detecting transmission in a large-scale field-study depends on logistical and financial considerations. Relatively simple snail sampling allows quick, cheap and widespread data collection adequate for most purposes but more complicated cercariometry is still valuable for specific, small-scale studies.

Type
Research Article
Copyright
Copyright © Cambridge University Press 1989

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

Blumenthal, U. & Jewsbury, J. (1986). Laboratory studies on a differential nitration technique for the recovery of schistosome cercariae from natural waters. Annals of Tropical Medicine and Parasitology 77, 441–2.CrossRefGoogle Scholar
Butterworth, A. E., Capron, M., Cordingley, J. S., Dalton, P. R., Kariuki, H. C., Kimani, R. K., Koech, D., Mugambi, M., Ouma, J. H., Prentice, M. A., Richardson, B. A., Siongock, T. K., Sturrock, R. F. & Taylor, D. W. (1985). Immunity after treatment of human schistosomiasis. II. Identification of resistant individuals and analysis of their immune responses. Transactions of the Royal Society of Tropical Medicine and Hygiene 79, 393408.CrossRefGoogle ScholarPubMed
Butterworth, A. E., Dalton, P. R., Dunne, D. W., Mugambi, M., Ouma, J. H., Richardson, B. A., Siongok, T. K. & Sturrock, R. F. (1984). Immunity after treatment of human schistosomiasis. I. Study design, pretreatment observations and the results of treatment. Transactions of the Royal Society of Tropical Medicine and Hygeine 78, 109–23.Google ScholarPubMed
Dazo, B. C., Hairston, N. G. & Dawood, I. K. (1966). The ecology of Bulinus truncatus and Biomphalaria alexandrina and its implication for the control of bilharzia in the Egypt-49 project area. Bulletin of the World Health Organization 35, 339–56.Google ScholarPubMed
Hairston, N. G. (1965). Statistical analysis of molluscicide field trials. Bulletin of the World Health Organization 32, 289–96.Google Scholar
Hoffman, D. B., Lehman, J. R., Scott, V., Warren, K. S. & Webbe, G. (1979). Control of schistosomiasis. Report of a workshop. American Journal of Tropical Medicine and Hygiene 28, 249–59.CrossRefGoogle ScholarPubMed
Jordan, P. (1985). Schistosomiasis: The St Lucia Project. Cambridge: Cambridge University Press.Google Scholar
Olivier, L. J. & Schneidermann, M. (1956). A method for estimating the density of aquatic snail populations. Experimental Parasitology 5, 109–17.CrossRefGoogle ScholarPubMed
Ouma, J. H., Sturrock, R. F., Butterworth, A. E., Kariuki, H. C., Koech, D. K., Prentice, M. A. & Siongok, T. K. (1989). Immunity after treatment of human schistosomiasis. V. Transmission studies-snail infection rates and cercariometry. East African Medical Journal (in the Press).Google Scholar
Prentice, M. A. (1984). A field-evolved differential filtration method for recovery of schistosomecercariae. Annals of Tropical Medicine and Parasitology 78, 117–27.CrossRefGoogle Scholar
Prentice, M. A. & Barnish, G. (1981). Snail infections following chemotherapy of Schistosoma mansoni in St Lucia, West Indies. Transactions of the Royal Society of Tropical Medicine and Hygiene 75, 713–14.CrossRefGoogle Scholar
Prentice, M. A. & Ouma, J. H. (1984). Field comparison of mouse immersion and cercariometry for assessing the transmission potential of water containing the cercariae of Schistosoma mansoni. Annals of Tropical Medicine and Parasitology 78, 169–72.CrossRefGoogle ScholarPubMed
Rose, G. & Barker, D. J. P. (1986). Epidemiology for the Uninitiated. London: British Medical Journal.Google Scholar
Shiff, C. J. (1964). Studies on Bulinus (Physopsis) globosus in Rhodesia. III. Bionomics of a natural population in a temporary habitat. Annals of Tropical Medicine and Parasitology 58, 240–55.CrossRefGoogle Scholar
Sturrock, R. F. (1973). Field studies on the transmission of Schistosoma mansoni and on the bionomics of its intermediate host, Biomphalaria glabrata, on St Lucia, West Indies. International Journal for Parasitology 3, 175–94.CrossRefGoogle Scholar
Sturrock, R. F. (1975). The distribution of the snail, Biomphalaria glabrata, intermediate host of Schistosoma mansoni within a St Lucian field habitat. Bulletin of the World Health Organization 52, 267–72.Google ScholarPubMed
Sturrock, R. F. (1986). Snail collection to detect schistosome transmission sites. Parasitology Today 2, 13.CrossRefGoogle ScholarPubMed
Sturrock, R. F., Bensted-Smith, R., Butterworth, A. E., Dalton, P. R., Kariuki, H. C., Koech, D., Mugambi, M., Ouma, J. H. & Siongok, T. K. (1987). Immunity after treatment of human schistosomiasis. III. Long-term effects of treatment and retreatment. Transactions of the Royal Society of Tropical Medicine and Hygiene 81, 303–14.CrossRefGoogle ScholarPubMed
Sturrock, R. F., Karamsadkar, S. J. & Ouma, J. H. (1979). Schistosome infection rates in field snails: Schistosoma mansoni in Biomphalaria pfeifferi from Kenya. Annals of Tropical Medicine and Parasitology 73, 369–75.CrossRefGoogle ScholarPubMed
Théron, A. (1979). A differential filtration technique for the measurement of cercarial densities in standing waters. Bulletin of the World Health Organization 57, 971–5.Google ScholarPubMed
THéRon, A. (1986). Cercariometry and the epidemiology of schistosomiasis. Parasitology Today 2, 35.CrossRefGoogle ScholarPubMed
Uemura, K. (1973). Statistical methods. In Epidemiology and Control of Schistosomiasis (Bilharziasis) (ed. Ansari, N.) Basel: S. Karger. pp. 704–39.Google Scholar
Webbe, G. (1962). The transmission of Schistosoma haematobium in an area of Lake Province, Tanganyika. Bulletin of the World Health Organization 27, 5983.Google Scholar
Wilkins, H. A., Blumenthal, U. J., Hagan, P., Hayes, R. J. & Tulloch, s. (1987). Resistance to reinfection after treatment of urinary schistosomiasis. Transactions of the Royal Society of Tropical Medicine and Hygiene 81, 2935.CrossRefGoogle ScholarPubMed
World Health Organization (1980). Epidemiology and control of schistosomiasis. Technical Report Series, No. 643. Geneva: World Health Organization.Google Scholar
World Health Organization (1985). The control of schistosomiasis. Technical Report Series, No. 728. Geneva: World Health Organization.Google Scholar