Lymphatic filariasis in kenya since 1910, and the prospects for its elimination: a review.

OBJECTIVES: To provide an overview of lymphatic filiariasis in Kenya from the first time its prevalence was reported to the present day, with suggestions of issues that are yet to be resolved and to present the prospects for its elimination. DATA SOURCES: Published and unpublished reports on filariasis studies in Kenya. STUDY SELECTION: Field-based epidemiological studies covering aspects of clinical, parasitology, entomology, social, economic, diagnosis and control of filariasis. DATA EXTRACTION: Review of published articles in scientific journals and communications, retrieval and review of published scientific articles from the Internet and personal communications. DATA SYNTHESIS: Re-organisation and pooling retrieved published data. CONCLUSIONS: Almost one century after the first documented report of lymphatic filariasis in Kenya, no National Control Programme has been instituted. However, important findings that have implications on its control have been made and they should be utilised to implement a National Control Programme. On implementation of the National Control Programme, research should be focussed on the remaining unresolved issues and conducted within the framework of the Programme. The World Health Organisation has targeted lymphatic filariasis for global elimination by the year 2020. Kenya is well positioned to formulate her National Plan for Elimination of Lymphatic Filariasis (NPELF) and join other endemic countries worldwide, which have already launched their plans, in the global efforts to eliminate lymphatic filariasis as a public health problem.

Cercarial density in the river of an endemic area of schistosomiasis haematobia in Kenya.

The cercarial density in natural water and number of infected Bulinus globosus were monitored over a one-year period to identify the transmission foci in an endemic area of schistosomiasis haematobia in Kenya. Overall prevalence and intensity of infection of the study community were 59.2% and 10.9 eggs/10 ml of urine. Cercariometry was carried out on 456 occasions at 20 study sites while snail sampling was done on 465 occasions at the same sites over a one-year period. Cercariometry was exclusively done at flowing water habitats. The results showed the focality and seasonality of transmission. Cercariae were detected on 44 occasions at 11 sites. The detections were made on seven occasions at two study sites, six occasions at one site, four occasions at four sites, three occasions at one site, two occasions at two sites, and one occasion at one site. Densities of 1-4 cercariae/100 liters of water were found on 31 occasions. Five to nine cercariae/100 liters of water were found on seven occasions, 10-19 cercariae/100 liters of water were found on two occasions, and high cercarial densities greater than 20 cercariae/100 liters of water were found on four occasions. The highest count was 52 cercariae/100 liters of water. The presence of cercariae in natural water was shown to depend on the water temperature, but the intensity and duration of sunlight did not affect the presence of cercariae in water. The monthly variability of cercarial density was proportional to the number of infected snails. Cercarial density was highest in March and April, in the middle of the rainy season, whereas no cercariae were detected in cool dry season. The snail population peaked late in March, the beginning of the long rainy season, remained high for two months, and decreased rapidly late in May when heavy rain occurred. The overall infection rate of snails was 7.3% and the majority of infected snails were collected from March to May. There was no definite correlation between the presence or absence of cercariae and infected snails. Cercariae were frequently found where infected snails were absent and cercariae were sometimes absent where infected snails were present. Cercariometry and snail sampling remain quite complementary in identifying the transmission foci of schistosomiasis.

Effect of piped water supply on human water contact patterns in a Schistosoma haematobium-endemic area in Coast Province, Kenya.

The effect of a piped water supply on human water contact in a Schistosoma haematobium-endemic area in Coast Province, Kenya was studied. After the construction of five community standpipes and one shower unit, there was a 35.1% reduction in the number of people observed using river water, a 44.1% reduction in the frequency of contact with river water, and a 25.4% reduction in the amount of contact. The frequency of river water contact per person also decreased significantly, but the amount of contact per person did not decrease. The total frequency of contact decreased significantly except for washing clothes by the river, washing utensils, and fishing. The frequency per person did not change for most of the activities and significantly increased for washing clothes. The frequency of river water contact in households with high piped water consumption showed a significant decrease compared with those with low piped water consumption. The volume of consumption of piped water was inversely proportional to the distance from the home to the community standpipe. These results indicate that in the study area, the effect of a piped water supply on river water contact behavior was heterologous while the total river water contact decreased significantly, and that the piped water had a beneficial effect on some villagers but very little effect on others.

Hourly change in cercarial densities of Schistosoma haematobium and S. bovis at different depths in the water and distances from the shore of a dam in Kwale District, Kenya.

Hourly change in cercarial densities was studied at different depths in the water and distances from the shore at a dam in Kwale District (Kenya), where Schistosoma haematobium is highly endemic, by using a filtration apparatus for detecting cercariae. The peak of cercarial density at the surface of water (2-3 cm deep) was at 11:00 hours. Those at the middle point (25 cm deep) and the bottom (50 cm deep) were at 12:00 and 13:00 hours respectively. In the morning, the majority of cercariae (79% of the total detected) was obtained at the surface of water, but none at the bottom. After midday, 40% of the cercariae were obtained at the bottom. Cercariae seemed to sink with time resulting in a wider distribution in the water. The numbers of cercariae obtained at a sampling point 20 cm from the shore, which was inside the wire-screened snail-free area, were 3.4-23 times more than those obtained at a sampling point 340 cm from the shore, indicating that cercariae were accumulating immediately near the shore. Winds might cause the accumulation.

Effects of Schistosoma haematobium infection on mental test scores of Kenyan school children.

Adverse effects of Schistosoma haematobium infection on mental activities were studied at a primary school in rural Kenya, where the intensity of infection was light (the average egg count: < 50/10 ml of urine). The school children received three kinds of mental tests, which examine attentiveness and concentration, before and a month after treatment with a single dose of praziquantel. A pretreatment analysis showed that test scores became worse as egg counts of children increased. The praziquantel treatment improved the scores of all three tests among children who got high scores in the first tests. The study showed that even the light infection caused adverse effects on mental activities, which were detectable using simple mental tests.

The usefulness of urinalysis reagent strips in selecting Schistosoma haematobium egg positives before and after treatment with praziquantel.

The effectiveness of urinalysis reagent strips for haematuria and proteinuria in selecting Schistosoma haematobium egg-positive persons was studied on 426 subjects of all ages in a Kenyan community before and 3 months after treatment with praziquantel. Before and after treatment, the degree of urinary blood or protein and prevalence of egg positives were closely associated. Haematuria and proteinuria were positively correlated with urinary egg counts. For selecting egg-positive persons with reagent strips, a combined criterion 'haematuria trace up or proteinuria 1 + up' was considered the best in this area. With this criterion, sensitivity and specificity before treatment were 69.6 and 84.4 respectively. These values remained at the same level (70.7 and 81.2%) even after treatment with praziquantel reduced prevalence from 59.4 to 13.6% (77% reduction) and intensity of infection from 57.2 to 11.3 eggs 10 ml-1 of urine (80% reduction). Although the sensitivity was not very high, heavy infections were not missed. If all those selected with reagent strips were treated and cured, a 98% reduction in total egg excretion by the community would be expected in both our first and second urine examinations.