Research

Seasonal variations in Schistosoma haematobium egg excretion in school-age girls in rural KwaZulu-Natal Province, South Africa

E E Christensen, M Taylor, S G Zulu, K Lillebo, S G Gundersen, S Holmen, E Kleppa, B J Vennervald, P D Ndhlovu, E F Kjetland

Abstract


Background. A predominant feature of Schistosoma haematobium infection is urinary egg excretion, and microscopic egg detection remains the accepted standard field diagnostic tool. Praziquantel is the drug of choice for schistosomiasis, and the World Health Organization recommends that it should be administered to all children >4 years of age living in schistosomiasis-endemic areas. The frequency of mass drug administration depends on the prevalence rate in the community. Urinary schistosome egg output has a day-to-day and hour-to-hour intrasubject variation. Therefore, it is important to assess possible seasonal variations in egg excretion to improve the planning of drug treatment.

Objectives. To assess the influence of seasonality on urinary schistosome egg excretion in South Africa (SA).

Methods. We performed a prospective cohort study, exploring seasonal variations of S. haematobium egg excretion in 184 girls aged 10 - 12 years from randomly selected schools in a rural area of KwaZulu-Natal Province, SA. The area has a subtropical climate characterised by a cool dry season and a hot humid season. For children, water contact is higher in the latter season. At baseline, 108 girls were examined in the hot season, and 76 in the cold season. In the next year’s cold season the untreated patients were re-investigated before treatment.

Results. There was a decrease in infection in the group initially tested in the hot season compared with the group tested in the cold season at both time points when adjusted for age and water contact (adjusted odds ratio 3.61 (95% confidence interval 1.14 - 11.44); p=0.03).

Conclusions. This unique study shows that schistosomiasis prevalence determined by microscopy exhibits seasonal variation, with a higher prevalence in the hot rainy season. Precise community prevalence estimations are key in decisions to treat communities. There was significantly lower egg output in the cold season, and sampling in that season may therefore underestimate the prevalence of urinary schistosomiasis. The study indicates that sampling in SA should be done in the hot season.


Authors' affiliations

E E Christensen, Norwegian Centre for Imported and Tropical Diseases, Department of Infectious Diseases Ullevaal, Oslo University Hospital; and Faculty of Medicine, University of Oslo, Norway

M Taylor, Discipline of Public Health Medicine, Nelson R Mandela School of Medicine, School of Public Health, College of Health Sciences, University of KwaZulu-Natal, Durban, South Africa

S G Zulu, Discipline of Public Health Medicine, Nelson R Mandela School of Medicine, School of Public Health, College of Health Sciences, University of KwaZulu-Natal, Durban, South Africa

K Lillebo, Norwegian Centre for Imported and Tropical Diseases, Department of Infectious Diseases Ullevaal, Oslo University Hospital; and Faculty of Medicine, University of Oslo, Norway

S G Gundersen, Department of Global Development and Planning, Faculty of Social Sciences, University of Agder, Kristiansand; and Research Department, Sørlandet Hospital HF, Kristiansand, Norway

S Holmen, Norwegian Centre for Imported and Tropical Diseases, Department of Infectious Diseases Ullevaal, Oslo University Hospital; and Faculty of Medicine, University of Oslo, Norway

E Kleppa, Norwegian Centre for Imported and Tropical Diseases, Department of Infectious Diseases Ullevaal, Oslo University Hospital; and Faculty of Medicine, University of Oslo, Norway

B J Vennervald, Section for Parasitology and Aquatic Diseases, Faculty of Health and Medical Sciences, University of Copenhagen, Denmark

P D Ndhlovu, Imperial College London, UK

E F Kjetland, Norwegian Centre for Imported and Tropical Diseases, Department of Infectious Diseases Ullevaal, Oslo University Hospital, Norway; and Discipline of Public Health Medicine, Nelson R Mandela School of Medicine, School of Public Health, College of Health Sciences, University of KwaZulu-Natal, Durban, South Africa

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Keywords

Schistosomiasis; Schistosoma haematobium; Haematobium; Seasonal variation; Variation; Mass drug administration; Prevalence; Epidemiology; Egg count; Microscopy; Immunity

Cite this article

South African Medical Journal 2018;108(4):352-355. DOI:10.7196/SAMJ.2018.v108i4.12775

Article History

Date submitted: 2018-03-28
Date published: 2018-03-28

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