ENVIRONMENTAL FACTORS AND CULTURAL PRACTICES INFLUENCING THE EPIDEMIOLOGY OF SOIL TRANSMITTED HELMINTHS IN IBADAN, NIGERIA

Abstract

Soil-Transmitted Helminths (STHs) which affect approximately two billion people globally is a common public health concern in developing nations. Dynamics of host and environmental factors results in fluctuations in the parasite infectivity rate. Thus demographic information in endemic localities is necessary. Therefore, there is need to constantly update epidemiological data across geographic zones including remote endemic areas. Hence, this study was designed to evaluate the current knowledge, attitude, and practices, as well as environmental factors influencing the prevalence and intensity of STHs in Ibadan. Soil samples (n=1980) were collected at a depth of 2-3 cm from five sampling sites (toilet areas, dumpsites, playgrounds, roadsides, and house vicinities) in the 11 Local Government Areas of Ibadan: South-East, South-West, North-East, North-West, Ibadan North, Akinyele, Ido, Lagelu, Egbeda, Oluyole and Ona-Ara, from January 2017 to December 2018. Faecal samples (n=1100) were also collected from consenting participants visiting Primary Health Centres. Parasite prevalence and intensity in soil and faecal samples were determined using standard methods, while temperature, rainfall, and Relative Humidity (RH) data were obtained from the Nigerian Meteorological Agency. Structured questionnaires were also administered to the consenting participants to obtain information on demographics (age, sex), and hygiene practices. Data were analysed using descriptive statistics, principal component analysis, and ANOVA at α0.05. Soil contamination with at least one STH was recorded in 54.9% of samples examined. Soil parasite prevalence (%) were 39.9 (hookworm larvae), 26.8% (Strongyloides larvae), 19.9% (Strongyloides adult), and 13.4% (Ascaris). Prevalence (%) by location was 49.2 (SouthEast), 48.1 (South-West), 48.3 (North-East), 49.8 (North-West), 47.4 (Ibadan North), 51.1 (Akinyele), 52.2 (Ido), 55.1 (Lagelu), 53.6 (Egbeda), 51.8 (Oluyole), and 54.3 (Ona-Ara). Dumpsites had the highest mean parasite intensity (epg) of 216.2±211.5, 120.4±119.6 (toilet areas), 75.1±73.6 (roadsides), 13.7±11.8 (playgrounds), and 3.4±1.8 (house vicinities). Faecal samples had overall prevalence of 35.9% with Ascaris being the most frequently occurring (41.6%), hookworm (24.5%), Trichuris (23.4%), and Strongyloides (10.4%).vi Highest parasite prevalence (%) in faecal samples was 38 from Ona-Ara, 36 (Lagelu), 35 (Ido), 34 (South-East), 32 (Egbeda), 31 (Akinyele), 30 (North-East), 29 (North-West), 28 (South-West), and 26 (Ibadan North). Overall intensity (epg) of faeces was 1043 (Ascaris), 771 (hookworm), 315 (Trichuris), and 210 (Strongyloides). Parasite prevalence (60.0%) was highest in November (mean temperature 30.9ºC; rainfall: 39 mm; RH: 83%), while intensity (359) was highest in March (27.4ºC; 67mm; 86%). Principal components 1, 2 and 3 accounted for 93.1% of total variations with RH (0.9) and rainfall (0.7) influencing STH prevalence (0.6) and intensity (0.7). Prevalence of infection was significantly higher in male (64.3%) than female (35.7%) participants. Prevalence was highest (23.4%) in 11-20 years and lowest (3.4%) in 51-60 years. Participants practicing open defaecation (22.4%) had a prevalence of 59.9%. However, participants that walk barefooted had STH prevalence of 60.7%. Inadequate knowledge, open defaecation practices, and walking barefooted coupled with favourable climatic factors facilitated transmission of soil helminths in Ibadan.