Epidémiologie de la schistosomiase et des géohelminthiases chez les enfants de 5 à 15 ans dans la province de Ouaddaï de la zone sahélienne au Tchad

Abstract

In developing countries, a child begins to be infected as soon as weaned and continues to be infected throughout his life. In Africa nowadays, helminthiasis arouses less and less interest due to the justified diversion of available resources towards more recent priorities such as HIV/AIDS, avian influenza, malaria, tuberculosis. However, these affections should neither be neglected nor put on the back burner, given the public health risks they bring to all developing nations. In Chad, very little research has been carried out on intestinal parasitosis and schistosomiasis. The present study aimed to evaluate the epidemiology of schistosomiasis and geohelminthiasis in schoolchildren aged 5 to 15 in the Ouaddaï province of Chad in the Sahel Zon. Thirteen schools (6 urban and 7 peri-urban) were randomly selected from which 1,341 pupils were recruited. Their stool samples were examined by the quantitative kato-katz method, while urine samples were analyzed by dipstick testing and centrifugation. The result showed that four parasite species were in the samples studied: Schistosoma haematobium, Schistosoma mansoni, Ascaris lumbricoides and Ancylostoma spp. The 343 (25.58%) participants were infested with at least one parasite species. The prevalences of Schistosoma haematobium, S. mansoni, A. lumbricoides, and Ancylostoma spp. were 28.61%, 6.38%, 9.00% and 1.45% respectively. Apart from Schistosoma mansoni and Ascaris lumbricoides, for which girls were significantly more often infested than boys, no other significant differences in infestation rates were found between genders for the other two parasites. Students in the 11-15 age group were more often infested with Schistosoma haematobium and Schistosoma mansoni than those in the 5-10 age group. The infestation rate among schoolchildren varied according to the source of drinking/cooking water, being nil among those using only tap water and peaking at 30.95% among those with access only to wells. The majority of households in the study area (54.2%) use canaries and jars for water storage, and it was in the latter category of households that children most often harbored intestinal worms (14.44%). Also 2.22% of pupils wearing open shoes were infested with hookworms, and none of those wearing closed shoes (0.0%). Pupils who reported bathing in marshes (30.15) were more likely to discharge S. haematobium eggs in their urine, as were those washing clothes and dishes (34.92%) and those living near streams (8.03%). Curiously, there was no statistical difference in the rate of Schistosoma mansoni infestation between students xxiv who bathed in mariogots and those who did not, and between students who washed in mariogots and those who did not. Polyparasitism by two parasite species was found in 0.30% of all schoolchildren examined, against 25.28% with monoparasitism. Logistic regression analysis revealed that schoolchildren in the 5 to 10 age group living in the peri-urban environment, and children in Abeche compared with those in Abougoudam were significantly more likely to be infested by a parasite species, while those in Chokoyan were half as likely to be infested by a helminth species as those in Abougoudam. Analysis of binary interspecific associations by ecological indices showed that all were very weak. The mean ovule loads of the different intestinal parasite species in the three localities were very light. In addition, microhematuria was observed in 40.08% of S. haematobium non-eggers and 97.89% of eggers. Given the overall prevalence of 25.58%, systematic mass deworming should be carried out at least once every three months. In addition, this result should be used to develop and implement a program to control intestinal helminthiasis and schistosomiasis in Chad.