Drug efficacy of praziquantel and albendazole in school children in Mwea Division, Central Province, Kenya.

The objective of this research was to assess drug efficacy in school children after mass chemotherapy with praziquantel and albendazole conducted in Mwea Division, Kirinyaga District, Central Kenya in 2004. In total 2300 children aged between 4 and 18 years in five primary schools were selected for the study. Before mass chemotherapy, prevalence of infection was 47.4% for Schistosoma mansoni, 16.7% for Necator americanus, 1.6% for Ascaris lumbricoides, and 0.8% for Trichuris trichiura. Post-treatment stool examination was carried out 8 weeks later, and a total of 1942 stool samples were collected. Prevalence decreased to 8.6% for S. mansoni, 0.2% for N. americunus, 0 for A. lumbricoides, and 0.6% for T. trichiura. Efficacy was good for S. mansoni and N. americanus (92.6% and 95.0%, respectively). Results of the first round of treatment of school-age children in Mwea indicate a good reduction in parasite burden.

Cercariometry for detection of transmission sites for schistosomiasis.

Cercariometry provided information on diurnal fluctuation, seasonal and spatial distribution of cercariae in the suitable natural water bodies. There was an apparent mismatch between the results of cercariometry and snail sampling. Water, which cercariometry showed to contain cercariae was potentially infective, although the resultant worm load of sentinel rodents may not bear a linear relationship with cercarial density. Cercariometry has some weakness in practices and analysis of data, however, it provides the valuable information on the active transmission sites of schistosomiasis.

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.

Effect of mass chemotherapy and piped water on numbers of Schistosoma haematobium and prevalence in Bulinus globosus in Kwale, Kenya.

From June 1982 to May 1986 in a small village in Kwale, Kenya, we studied seasonal fluctuations in populations of Bulinus globosus, prevalence of Schistosoma haematobium infection in this snail, and effects of chemotherapy and piped water supply on infection rate of snails. In the perennially-flowing Pemba River, relatively small numbers of snails were collected; they were found only during the hot dry season (December to March). In a tributary stream, the Kadingo River, whose flow ceased at the end of both the cool and hot dry seasons, snail numbers peaked at the end of the cool dry season (October to November) and at the beginning of the hot dry season (January). Large numbers of infected snails were found in the Kadingo River from November to January (short rainy season and beginning of dry season). Selective mass chemotherapy with metrifonate and provision of piped water were begun in February and March 1984. These control measures achieved a significant reduction in the infection rate of snails (P less than 0.001); the annual infection rate for the 2 years before treatment was 9.3% and 13.1%, and for the 2 years after treatment was 3.5% and 3.4%.

Efficacy of metrifonate in a highly endemic area of urinary schistosomiasis in Kenya.

In a community in Kwale district, Kenya, selective mass chemotherapy with metrifonate caused a marked reduction in the intensity of Schistosoma haematobium infection from 46.5 to 9.4 eggs/hr and a sharp fall in prevalence of gross hematuria from 18.3% to 5.1%, although overall prevalence was reduced only slightly from 67.4% to 54%. The effect of metrifonate on cure rate and reduction of infection intensity was limited by both age and pretreatment infection intensity. Rate of improvement from gross hematuria was similar in all ages and in all classes of intensity of infection. Two doses of metrifonate reduced the prevalence of gross hematuria as much as 3 doses did, while the effect of a single dose on morbidity remains to be clarified.