The current status of onchocerciasis in the forest/savanna transition zone of Côte d'Ivoire.

Onchocerca volvulus exists in at least two strains in West Africa, while its black-fly vectors consist of sibling species, dwelling in the savanna and forest/transition zones. In transition and degraded forest zones both parasite strains and different sibling species of the vector can be sympatric. The strain of parasite in infected humans and in vector black-flies was determined in two bioclimes along the Bandama river of Côte d'Ivoire. The upper Bandama is located in the savanna bioclime while the Middle Bandama is located in a degraded forest zone. At both sites, savanna-dwelling sibling species of the Simulium damnosum sensu lato species complex predominated. The severe-strain of O. volvulus was the predominant strain at both sites. However, severe-strain parasites represented a significantly larger proportion of those found in the vector population than in the human population in the degraded forest of the Middle Bandama. These data suggest that in degraded forest areas recently invaded by savanna-dwelling species of S. damnosunz s.l. transmission of the severe-strain of the parasite might be more efficient than transmission of the mild-strain.

The effect of albendazole on Oesophagostomum bifurcum infection and pathology in children from rural northern Ghana.

Ultrasonography has already revealed that up to 50% of individuals in some villages in northern Ghana have colonic pathology induced by Oesophagostomum bifurcum. Approximately 2% of those affected progress to clinical oesophagostomiasis if left untreated. In the present study, ultrasound-positive children living in a heavily infected community were each given 5 days of treatment with albendazole (10 mg/kg.day), early in the dry season. Treatment reduced the prevalence, number, size and half-life of the ultrasound-visible nodules, stopped the excretion of O. bifurcum eggs, and reduced the development of clinical oesophagostomiasis during the subsequent 8 months. However, the treatment had no impact on the new infections that occurred during the following rainy season, and no impact on nodule prevalence by the end of that rainy season. Surgical management may not be essential in non-acute cases of clinical oesophagostomiasis, as albendazole may kill the nodule-dwelling worms.

Emergency vaccination against epidemic meningitis in Ghana: implications for the control of meningococcal disease in West Africa.

BACKGROUND: Recurrent epidemics of meningococcal disease have been reported throughout the African meningitis belt since description of the disease in 1912. Meningooccal polysaccharide vaccines can effectively prevent disease but the optimum strategy for their use in this setting has been controversial. We used data from an outbreak of meningococcal disease in northern Ghana in 1997 to assess the potential effect of different vaccination strategies. METHODS: We identified all reported cases of meningococcal meningitis and estimated the number of cases and deaths that could have been prevented by vaccination through use of a simple mathematical model. We then assessed the potential effect of different vaccination strategies and the burden of these strategies on the public-health system. FINDINGS: In the three affected regions in northern Ghana there were 18703 cases and 1356 deaths reported between November, 1996, and May, 1997. Vaccination began in the third week of February and continued to April, reaching 72% of the at-risk population and preventing an estimated 23% of cases and 18% of deaths. A strategy of routine childhood and adult immunisation would have prevented 61% of cases had this same rate of vaccine coverage been achieved and maintained before the epidemic. If vaccination had started after the onset of the epidemic in January, as currently advocated by WHO guidelines, a similar proportion (61%) of cases could have been prevented. INTERPRETATION: Prevention of epidemics of meningococal disease in west Africa will be difficult until long-lasting conjugate vaccines capable of interrupting transmission of Neisseria meningitidis can be incorporated into routine infant-immunisation schedules. Until then, the strategy of surveillance and response advocated by WHO is as effective and more practical than a strategy of routine childhood and adult vaccination with currently available polysaccharide vaccines.

PIP: This study assessed the potential effects of different vaccination strategies using data from the 1997 meningococcal outbreak in northern Ghana. Since the description of the disease in 1912, recurrent epidemics of meningococcal disease have been reported throughout the African meningitis belt. The use of meningococcal polysaccharide vaccines has been proven to effectively prevent the disease, although the method of vaccine distribution was disputable. Using a simple mathematical model, meningococcal meningitis cases and deaths, which could have been forestalled by vaccination, were identified, and the effect of developed vaccination strategies on the public health system was analyzed. About 18,703 cases and 1356 deaths were reported in 3 regions of northern Ghana between November 1996 and May 1997. Vaccination was conducted between February and April, which covered 72% of the high-risk population and prevented approximately 23% of cases and 18% of deaths. Routine childhood and adult immunization would have prevented 61% of cases had this same rate of vaccine coverage been achieved and maintained before the epidemic. This study suggests that the prevention of the meningococcal disease epidemic in West Africa would be difficult unless long-lasting conjugate vaccines are incorporated into routine infant immunization schedules. For now, the surveillance and response strategies advocated by the WHO serve as an effective and practical intervention.

Community participation in the eradication of guinea worm disease.

As Guinea worm eradication programmes have got under way in endemic countries over the last decade, there has been a shift towards more participatory methods. The approach to surveillance has changed from periodic cross-sectional surveys to monthly village-based reporting of cases by a volunteer village health worker. At the same time, the emphasis regarding control interventions has moved from the provision of safe water supplies to health education. The new approach has proved very effective. The village health volunteers who carry out both surveillance and health education seem to be motivated largely by the social status of their role; still more commitment will be required of them in the final stages of eradication. It is to be hoped that the networks of village health workers established for Guinea worm eradication will find a useful role in health promotion after the worms have gone.