Academic journal article Bulletin of the World Health Organization

Evolution of Operational Research Studies and Development of a National Control Strategy against Intestinal Helminths in Pemba Island, 1988-92

Academic journal article Bulletin of the World Health Organization

Evolution of Operational Research Studies and Development of a National Control Strategy against Intestinal Helminths in Pemba Island, 1988-92

Article excerpt

Intestinal helminthic infections in Pemba Island, United Republic of Tanzania, have been perceived as a public health problem for many decades. School surveys in 1988 and 1992 and a community survey in 1991 were carried out to assess the distribution of prevalence and the intensity of these infections and to define the most effective strategy for control. The prevalence of helminthic infections exceeded 85% in all the surveys, and intensity was moderate. These studies identified the high-risk age groups, high transmission areas for different parasites, and the most cost-effective anthelminthic drug. This work is an example of how existing health systems and simple analytical tools may be used to generate useful data which, in turn, are used to define suitable intervention strategies. As a result, the Ministry of Health of Zanzibar has developed a national plan for the integrated control of intestinal helminths. This plan envisages periodic mass treatment of school-age children with mebendazole (500 mg, single dose, every four months) for the control of morbidity due to Ascaris, Trichuris, and hookworms.


Infection with intestinal parasites is a widespread problem in the developing world (1)(2). The prevalence and severity of infection is especially high in many developing countries where health and sanitation facilities are unable to cope with the needs of an increasing population (3). The main burden of these infections is borne by young children, with adverse effects on their physical and mental development which may be long-lasting(4)(5)(6).

In Zanzibar, intestinal parasitoses are recognized as a major health problem.(a) A schistosomiasis control programme was initiated in 1986, on the island of Pemba, by the Ministry of Health of Zanzibar, with support from WHO, the Italian Ministry of Foreign Affairs, and the German Pharma Health Fund to deal with the high prevalence of infection with Schistosoma haematobium(7)(8)(9)(10)(11)(12)(13). As an extension to this programme, studies have been performed since 1988 to determine the extent of infection with soil-transmitted helminths such as hookworms, Ascaris and Trichuris, and to test the efficacy of low-cost anthelminthic drugs.

In this paper we present the results and conclusions from operational research studies carried out between 1988 and 1992. This work has led to the initiation of a national plan of action for the control of helminths by the Ministry of Health of Zanzibar in 1992.

Materials and methods

The health administration of the island of Pemba is under the Ministry of Health of Zanzibar. Other relevant features of the island have been described elsewhere (7)(8).

School surveys. Three school surveys were conducted between 1988 and 1992. In the initial survey of 1988, about 10% of the total school population were studied. The study population (3436 children from all classes; age range, 4--20 years) was from eight schools selected randomly from various regions of the island.

The second school survey was initiated in early 1992 to evaluate the impact of periodical anthelminthic chemotherapy on parasitological indicators (prevalence and intensity rates) and growth in schoolchildren. To this end, a random sample of about 1120 students (age range, 9--17 years) was selected from the standard 5 classes of 35 schools in the island.

The latest survey was conducted in late 1992 on 3202 students (age range, 6--12 years) from 10 schools in the island. This was a pre-treatment survey carried out within a drug-efficacy trial (albendazole 400 mg vs mebendazole 500 mg); all children testing positive were treated with either mebendazole or albendazole.

Community survey. One community survey was performed in 1991. Faecal samples were collected from randomly sampled households of two towns (Wete and Chake Chake) and six villages (Makangale, Kiuyu, Shungi, Pujini, Ngwachani, Mzingani). A total of 2247 individuals in all age groups (age range, 1--85 years) were examined and subsequently treated with a single dose of mebendazole 500 mg (children aged<2 years received 250 mg). …

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