Influence of air temperature on children water contacts with respect to schistosomiasis transmission risk in the Sourou Valley, Burkina Faso

Climate and water contacts are among the most important risk factors of human schistosomiasis transmission. This study aimed to determine—through direct field observations—the influence of air temperature on the frequencies of children´s water contacts with respect to human schistosomiasis transmission risk in the Sourou Valley, located in the North-western part of Burkina Faso. The objectives of the study were: (i) to study the air temperature at which children have the sensation of heat and start looking for water as a means for natural cooling; and (ii) to study whether high frequencies of swimming or bathing may lead to a higher risks of schistosomiasis transmission. To do so, swimming or bathing were observed during two different periods: a cold one from 3rd January to 2nd February 2011 and a hot one from 3rd April to 3rd May 2011 in Toma-Île, a village totally surrounded by water. The results showed that daily mean air temperatures never exceeded 30 °C during the coldest period, while they were above this value during the hottest period. In total, swimming activities were observed 11/31 days during the coldest period and 31/31 during the hottest period. Bathing of children below the age of 5 years occurred on 55/62 days. 25 °C was the day mean air temperature from which children felt hot and began playing in water. The hourly occurrence of swimming and bathing showed peaks at 2 PM. This coincides with the diurnal maximum of infective cercariae present in the same water. Thus, in order to freshen up during hot periods of the day, children used to look for freshwater and thus expose themselves to a high schistosomiasis transmission risk.