Ascaris lumbricoides infection and its relation to environmental factors in the Mbeya region of Tanzania, a cross-sectional, population-based study

• Published in: PloS one Vol. 9; no. 3; p. e92032
• Main Authors: Schüle, Steffen Andreas, Clowes, Petra, Kroidl, Inge, Kowuor, Dickens O, Nsojo, Anthony, Mangu, Chacha, Riess, Helene, Geldmacher, Christof, Laubender, Rüdiger Paul, Mhina, Seif, Maboko, Leonard, Löscher, Thomas, Hoelscher, Michael, Saathoff, Elmar
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 18.03.2014; Public Library of Science (PLoS)
• Subjects: Adolescent; Adult; Analysis; Analysis of Variance; Animals; Annual rainfall; Ascariasis - epidemiology; Ascariasis - parasitology; Ascariasis - transmission; Ascaris lumbricoides; Ascaris lumbricoides - physiology; Bioinformatics; Biology and Life Sciences; Biometrics; Child; Child, Preschool; Confidence intervals; Cross-Sectional Studies; Demographics; Eggs; Environmental conditions; Environmental effects; Environmental factors; Epidemiology; Female; Health aspects; Households; Humans; Infections; Infectious diseases; Intestine; Land surface temperature; Linear analysis; Male; Mean annual precipitation; Medical research; Medicine; Medicine and Health Sciences; Middle Aged; Nonlinear analysis; Odds Ratio; Parasitology; Polynomials; Population; Population studies; Population-based studies; Prevalence; Public health; Rain; Rainfall; Regression analysis; Remote sensing; Research and Analysis Methods; Roundworms; Socioeconomic Factors; Statistical analysis; Studies; Surface temperature; Surveys; Tanzania - epidemiology; Temperature; Trichuris trichiura; Tropical environments; World population; Tanzania; Germany
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0092032

With one quarter of the world population infected, the intestinal nematode Ascaris lumbricoides is one of the most common infectious agents, especially in the tropics and sub-tropics. Infection is caused by oral intake of eggs and can cause respiratory and gastrointestinal problems. To identify high risk areas for intervention, it is necessary to understand the effects of climatic, environmental and socio-demographic conditions on A. lumbricoides infection. Cross-sectional survey data of 6,366 study participants in the Mbeya region of South-Western Tanzania were used to analyze associations between remotely sensed environmental data and A. lumbricoides infection. Non-linear associations were accounted for by using fractional polynomial regression, and socio-demographic and sanitary data were included as potential confounders. The overall prevalence of A. lumbricoides infection was 6.8%. Our final multivariable model revealed a significant non-linear association between rainfall and A. lumbricoides infection with peak prevalences at 1740 mm of mean annual rainfall. Mean annual land surface temperature during the day was linearly modeled and negatively associated with A. lumbricoides infection (odds ratio (OR) = 0.87, 95% confidence interval (CI) = 0.78-0.97). Furthermore, age, which also showed a significant non-linear association (infection maximum at 7.7 years), socio-economic status (OR = 0.82, CI = 0.68-0.97), and latrine coverage around the house (OR = 0.80, CI = 0.67-0.96) remained in the final model. A. lumbricoides infection was associated with environmental, socio-demographic and sanitary factors both in uni- and multivariable analysis. Non-linear analysis with fractional polynomials can improve model fit, resulting in a better understanding of the relationship between environmental conditions and helminth infection, and more precise predictions of high prevalence areas. However, socio-demographic determinants and sanitary conditions should also be considered, especially when planning public health interventions on a smaller scale, such as the community level.