Hookworm Infection and Environmental Factors in Mbeya Region, Tanzania: A Cross-sectional, Population-based study.

Hookworm disease is one of the most common infections and cause of a high disease burden in the tropics and subtropics. Remotely sensed ecological data and model-based geostatistics have been used recently to identify areas in need for hookworm control. Cross-sectional interview data and stool samples from 6,375 participants from nine different sites in Mbeya region, south-western Tanzania, were collected as part of a cohort study. Hookworm infection was assessed by microscopy of duplicate Kato-Katz thick smears from one stool sample from each participant. A geographic information system was used to obtain remotely sensed environmental data such as land surface temperature (LST), vegetation cover, rainfall, and elevation, and combine them with hookworm infection data and with socio-demographic and behavioral data. Uni- and multivariable logistic regression was performed on sites separately and on the pooled dataset. Univariable analyses yielded significant associations for all ecological variables. Five ecological variables stayed significant in the final multivariable model: population density (odds ratio (OR) = 0.68; 95% confidence interval (CI) = 0.63-0.73), mean annual vegetation density (OR = 0.11; 95% CI = 0.06-0.18), mean annual LST during the day (OR = 0.81; 95% CI = 0.75-0.88), mean annual LST during the night (OR = 1.54; 95% CI = 1.44-1.64), and latrine coverage in household surroundings (OR = 1.02; 95% CI = 1.01-1.04). Interaction terms revealed substantial differences in associations of hookworm infection with population density, mean annual enhanced vegetation index, and latrine coverage between the two sites with the highest prevalence of infection. This study supports previous findings that remotely sensed data such as vegetation indices, LST, and elevation are strongly associated with hookworm prevalence. However, the results indicate that the influence of environmental conditions can differ substantially within a relatively small geographic area. The use of large-scale associations as a predictive tool on smaller scales is therefore problematic and should be handled with care

Spatial and Genetic Epidemiology of Hookworm in a Rural Community in Uganda

There are remarkably few contemporary, population-based studies of intestinal nematode infection for sub-Saharan Africa. This paper presents a comprehensive epidemiological analysis of hookworm infection intensity in a rural Ugandan community. Demographic, kinship, socioeconomic and environmental data were collected for 1,803 individuals aged six months to 85 years in 341 households in a cross-sectional community survey. Hookworm infection was assessed by faecal egg count. Spatial variation in the intensity of infection was assessed using a Bayesian negative binomial spatial regression model and the proportion of variation explained by host additive genetics (heritability) and common domestic environment was estimated using genetic variance component analysis. Overall, the prevalence of hookworm was 39.3%, with the majority of infections (87.7%) of light intensity (≤1000 eggs per gram faeces). Intensity was higher among older individuals and was associated with treatment history with anthelmintics, walking barefoot outside the home, living in a household with a mud floor and education level of the household head. Infection intensity also exhibited significant household and spatial clustering: the range of spatial correlation was estimated to be 82 m and was reduced by a half over a distance of 19 m. Heritability of hookworm egg count was 11.2%, whilst the percentage of variance explained by unidentified domestic effects was 17.8%. In conclusion, we suggest that host genetic relatedness is not a major determinant of infection intensity in this community, with exposure-related factors playing a greater role

Studies on the microfilarial density and annual transmission potential of Mansonella perstans by Culicoides species in selected communities of Ogoniland, Rivers State, Nigeria

No Abstract. Nigerian Journal of Parasitology Vol. 26, 2005: 23-2

Mansonellosis in the upper Imo River Basin, Nigeria

The Upper Imo River Basin is endemic for mansonellosis due to Mansonella perstans. No case of M. streptocerca microfilaraemia was found in the studied population. The prevalence of M. perstans microfilariae in the area was 12.5%. Microfilaraemia was higher among older individuals and there was no significant difference in prevalence between sexes. The overall mf GMI among mf positives was 98 mf/ml (103 mf/ml for males and 92 mf/ml for females). There was no significant difference between the overall mf GMI in males and females (t-test; p >0.05). It is generally believed that mansonellosis due to M. perstans does not cause any serious clinical sign or symptom, and consequently there was no examination for clinical manifestations related to this infection in the Upper Imo River Basin of the studied population.Keywords: mansonellosis, Imo River, epidemiologyGlobal Journal of Pure and Applied Sciences Vol. 11(4) 2005: 465-46

A survey of breeding sites and variation of Simulium damnosum in Ini L.G.A. of Akwa Ibom, Nigeria

In the year 2001, a total of 9207 aquatic stages of Simulium damosum were collected from five group of breeding sites; (53.4%), submerged leaves 3263 (35.4%), submerged rocks 723 (7.9%), other object 210 (2.3%) and free water 95 (1.0%) in two streams. The 4556 adults captured were distinguished into 3 complexes based on morphometric methods. The Aquatic stages prevalence shows highest abundant of 1277 in October, the peak adult abundant (485) followed the aquatic stages peak by one month in November. The distinction of S. damnosum by morphometric methods provides a valuable tool in the study and control of onchocerciasis. The Nigerian Journal of Parasitology Vol. 24 2003: 149-15