Date of Award

12-1983

Degree Name

Doctor of Philosophy

Department

Science Education, Mallinson Institute

First Advisor

Dr. Joseph G. Engemann

Second Advisor

Dr. George G. Mallinson

Third Advisor

Dr. Clarence J. Goodnight

Fourth Advisor

Dr. Henry van der Schalie

Abstract

Schistosomiasis is a serious disease in humans. Two species of schistosome, Schistosoma mansoni and Schistosoma haematobium, organisms that cause the disease, parasitize humans in Libya. Schistosomes require aquatic snails in their life cycle. The purpose of this study was to investigate the environmental and the host relationships of the disease in the three regions of Libya where the disease is found. These relationships include:

1) Analyses of the physical-chemical characteristics of the aquatic habitat.

2) Collection of snails to determine: a) the kind of snail species and th e ir abundance; and b) the cercarial infestation rates.

3) Infection rates in humans.

4) A search for relationships among factors that appear to be significant in the distribution of the disease.

Biomphalaria alexandrina or Buiinus truncatus, the intermediate host snails for Schistosoma mansoni and Schistosoma haematobium, were the most abundant species of snails in a ll three locations of the endemic foci - the Mizurata region, the Derna region, and the Fezzan region. In the Mizurata region, 1,742 Biomphalaria snails were found among 2,559 snails. In the Fezzan region, 907 Bulinus snails were found among 968, and in the Uerna region, 75 Bulinus snails were found among 302. The incidence of cercaria in snails was found to be 0.63% in the Mizurata area, 0.44% in the Fezzan region, but none of the Bulinus snails in the Derna region were found to be infected.

Infection rates in males vary with age, region, species of schistosome, and history of residence. The infection rate among students with S. mansoni in the Mizurata region was found to be 65%, whereas the rate in the adult male population was 18.34%. The S. haematobium infection rate among adults in the Fezzan region was found to be 9%, and in the Derna region it was 8.5%. Non-Libyans working in the Libyan agricultural regions had infection rates averaging about 40%, whereas Libyans in the same region had rates of infection averaging about 9%.

Access Setting

Dissertation-Open Access

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