Variation in exposure of children to malaria vectors of the Anopheles gambiae complex was recorded in a Gambian village situated near an irrigated area of rice cultivation. Observations were made in 1987 and 1988 during two dry seasons, when pumped water was used to grow rice, and two rainy seasons, when rice was produced using a combination of irrigated and rainfed paddies. Routine collections of mosquitoes were made from under bednets. Most of these specimens were assumed to have fed on the occupants of the net and thus represented a crude measure of exposure to malaria. Most nets in the village were in good condition, but even these were a poor defence against blood-seeking mosquitoes. Two annual peaks in the numbers of An.gambiae s.l. corresponded with the irrigation of rice paddies in the dry and wet seasons. When there were few vectors in the village the frequency distribution of mosquitoes caught under nets was described best by a Poisson process. When high numbers were present the daily distributions were over-dispersed and fitted a negative binomial model. The spatial distribution of mosquitoes varied between dry and wet seasons and was related to the predominant wind direction at night, suggesting that wind assisted the dispersal of mosquitoes from their breeding sites.(ABSTRACT TRUNCATED AT 250 WORDS)

A randomized, double-'blind', placebo-controlled trial of weekly Maloprim (dapsone-pyrimethamine, D-P) for malaria prophylaxis was conducted at Magoda village in north-eastern Tanzania. The effect of D-P on the incidence of clinical malaria, Plasmodium falciparum prevalence and density, splenomegaly, and packed cell volume (PCV) was investigated in a cohort of 249 children (126 receiving D-P and 123 receiving placebo) aged 1-9 years. The case definition of clinical malaria (malaria fever) was measured axillary temperature > or = 37.5 degrees C and/or reported fever, and P. falciparum asexual parasitaemia > or = 5000/microL. Children aged 1-4 years given D-P experienced 1.56 episodes of clinical malaria per year, whereas children on placebo experienced 2.55 episodes (relative rate [RR] = 0.61, 95% confidence interval [CI] 0.47, 0.80). Thus, D-P protective efficacy against clinical malaria, in this age group, was 39% (95% CI 20%, 53%; P = 0.0002). The annual incidence of clinical malaria among children aged 5-9 years was 0.16 episodes in the D-P group and 0.26 episodes in those receiving placebo (RR = 0.58, 95% CI 0.26, 1.28; P = 0.17). Increased malaria transmission and drug resistance, during the course of the trial, resulted in a reduction in the protective efficacy of D-P. Overall, D-P was able to reduce parasite densities and splenomegaly. D-P prophylaxis also resulted in an increase in PCV but this effect diminished towards the end of the trial. D-P exerted a suppressive effect on asexual parasitaemia throughout the trial.

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BackgroundIn order to use a combination of ivermectin and albendazole for the elimination of lymphatic filariasis, it is important to assess the potential risk of increased adverse events in individuals infected with both lymphatic filariasis and onchocerciasis. We compared the safety and efficacy of albendazole (400 mg) in combination with ivermectin (150 micrograms/kg), for the treatment of co-infections of Wuchereria bancrofti and Onchocerca volvulus with single infection of W. bancrofti.MethodsThe safety study on co-infections was a crossover, double blind design, while for the single infection of bancroftian filariasis an open design comparing two treatments was used. For co-infection, one group was allocated a single dose of ivermectin (150 micrograms/kg) plus albendazole (400 mg) (Group A). The other group received placebo (Group B). Five days later the treatment regime was reversed, with the Group A receiving placebo and Group B receiving treatment. For the single bancroftian filariasis infection, one group received a single dose of albendazole (400 mg) plus ivermectin (150 μg/kg) (Group C) while the other group received a single dose of albendazole (400 mg) alone (Group D). Blood and skin specimens were collected on admission day, day 0, and on days 2, 3, and 7 to assess drug safety and efficacy. Thereafter, blood and skin specimens were collected during the 12 months follow up for the assessment of drug efficacy. Study individuals were clinically monitored every six hours during the first 48 hours following treatment, and routine clinical examinations were performed during the hospitalisation period and follow-up.ResultsIn individuals co-infected with bancroftian filariasis and onchocerciasis, treatment with ivermectin and albendazole was safe and tolerable. Physiological indices showed no differences between groups with co-infection (W. bancrofti and O. volvulus) or single infection (W. bancrofti). The frequency of adverse events in co-infected individuals was 63% (5/8, Group A, albendazole + ivermectin) and 57% (4/7, Group B, placebo) and of mild or moderate intensity. In single W. bancrofti infection the frequency of adverse events was 50% (6/12, Group C, albendazole + ivermectin) and 38% (5/13, Group D, albendazole) and of a similar intensity to those experienced with co-infection. There were no differences in adverse events between treatment groups. There was no significant difference in the reduction of microfilaraemia following treatment with albendazole and ivermectin in groups with single or co-infection.ConclusionOur findings suggest that ivermectin plus albendazole is a safe and tolerable treatment for co-infection of bancroftian filariasis and onchocerciasis.