Clinical and parasitological aspects of Bancroftian filariasis in Hale, northeast Tanzania.

OBJECTIVES: To document the endemicity characteristic of Bancroftian filariasis and to validate the effect of blood sampling time adjustment method on microfilarial intensity in relation to sex and age. DESIGN: Community based cross sectional survey. SETTING: Four rural communities in Hale area, Muheza district, northeast Tanzania. SUBJECTS: A sample of 1,025 inhabitants aged one year and above. MAIN OUTCOME MEASURES: Chronic clinical manifestations (elephantiasis and hydrocele), microfilarial prevalence as well as crude and time adjusted microfilarial geometric mean intensity (GMI). RESULTS: Clinically, 6.9% of examined individuals had elephantiasis and 28.5% males aged 15 years and above had hydrocele. Prevalence of Wuchereria bancrofti infection was 31.8%, with females and males showing a microfilarial rate of 32.1% and 31.5% respectively. Both the clinical manifestations and microfilarial prevalence increased with age. The GMI among microfilarial positive individuals for the crude microfilaraemia was 1,122 or 1,175 mf/ml of blood after adjustment of the sample to the expected level if it had been collected at peak hour. In different age and sex groups, the adjusted microfilarial GMI was slightly higher but exhibited a similar pattern to crude microfilaraemia count suggesting that time of blood sampling has similar effect on each age and sex group.

Clinical and parasitological aspects of itching caused by onchocerciasis in Morogoro, Tanzania.

A clinical and parasitological assessment of onchodermatitis was conducted in a rural area of Morogoro district, Tanzania. The study population consisted of 1,005 individuals aged > or = 5 years: 749 from a hyper-endemic community and 256 from a hypo-endemic. The prevalence of troublesome itching was 67.0% in the hyper-endemic community but only 5% (13/256) in the hypo-endemic. The corresponding prevalences of nodules among the adult male subjects were 77.7% (171/220) and 2.3% (2/86). The most common onchocercal skin lesion in the hyper-endemic community was chronic papular onchodermatitis (CPOD) manifested by itching, which was often very severe. There was a strong association between skin itching and endemicity (r = 0.75; P < 0.001). The prevalence of CPOD in the hyper-endemic community was significantly higher in males than females (P< 0.001). CPOD was only observed in subjects aged > or = 7 years. Many of the subjects were checked for microfilaridermia, by skin-snipping. The prevalence of microfilaridermia [58.2% (393/675) v. 6.2% (3/48)] and its geometric mean intensity (8.9 v. 1.0 microfilariae/mg skin snip) were both higher in the hyper-endemic community than the hypo-endemic. Itching appears to be related to reactive onchodermatitis.

Maloprim malaria prophylaxis in children living in a holoendemic village in north-eastern Tanzania.

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.

Immunoglobulin G reactivities to rhoptry-associated protein-1 associated with decreased levels of Plasmodium falciparum parasitemia in Tanzanian children.

In the Muheza region of Tanzania, an area with holoendemic malaria, the proportion of responders with IgG enzyme-linked immunosorbent assay reactivities to recombinant rhoptry-associated protein-1 (rRAP-1) as well as IgG reactivities to a repeat region of the acidic-basic repeat antigen (ABRA) increased with age. The proportion of responders with IgM reactivities to rRAP-1 increased with age in the first three decades. However, levels of IgG reactivities to rRAP-1 did not increase with age, indicating high levels of reactivities among young children. High P. falciparum densities were only detectable in children less than five years of age; in this group the proportion of IgG responders to rRAP-1 and to the ABRA repeat region was low but levels of IgG reactivities to rRAP-1 were inversely correlated with parasite density, suggesting that immune recognition of the antigen may be associated with resistance to infection. On the other hand, levels of IgG reactivities to the repeat region of ABRA increased with parasite densities in children 1-4 years of age. Two different profiles of IgG reactivities to rRAP-1 and to ABRA are detectable in young Tanzanian children and the Ig reactivities against rRAP-1 may be a component of the immune reactions restricting parasite multiplication.

Exposure of Gambian children to Anopheles gambiae malaria vectors in an irrigated rice production area.

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)

Mortality of under-fives in a rural area of holoendemic malaria transmission.

From January 1992 to December 1993, a total of 361 births and 243 deaths were recorded by village reporters in five villages in Muheza District, north eastern Tanzania. Among those aged less than one year 48 deaths were recorded, giving an infant mortality rate of 133 per 1000 live births (95% CI 97.9-168.0). There were 42 deaths among the censused population of 845 children aged 1-4 years (24.8/1000/year, 95% CI: 17.4-32.3). Verbal autopsy questionnaires were administered to parents or close relatives of 83 of the dead infants and children. From analysis of these, 30 of the deaths were tentatively attributed to malaria. The results are discussed in relation to other studies in East and West Africa and to the prospects for reducing mortality by use of insecticide impregnated bednets.

PIP: The rural areas of Muheza District in northeastern Tanzania are holoendemic for malaria. In Tanzania, malaria is the largest single cause of hospital attendance, the second largest cause for hospital admission, and one of the leading causes of hospital deaths. Hospital data, however, only reveal part of the picture of childhood mortality because most such deaths in rural areas occur at home. The authors investigated the causes of infant and child mortality in five villages near Muheza to collect baseline data in preparation for aa large-scale study planned to explore the impact of impregnated bednets upon infant and child mortality. Records of births, deaths, ages at death, and supposed causes of death were collected by village reporters, while verbal autopsies were obtained from parents or close relatives of dead infants and children. The study 361 births and 243 deaths were recorded by the village reporters from January 1992 to December 1993. There were 48 deaths to infants under one year old for an infant mortality rate of 133/1000 live births. 42 deaths were recorded among the censused population of 845 children aged 1-4 years. Verbal autopsy questionnaires were administered to parents or close relatives of 83 of the dead infants and children. On analysis, 30 deaths were tentatively attributed to malaria. These results are discussed in relation to other studies in East and West Africa, and to the prospects for reducing mortality through the use of insecticide-impregnated bednets.