RESUMEN
Heterogeneity of Schistosoma haematobium transmission in irrigated fields. Although irrigated areas exist since a long time in the Niger Valley the distribution of the urinary schistosomiasis does not appear homogeneous, testifying to the existence of limiting or favourable factors. The identification of these factors could lead to a better definition of the distribution of the schistosomiasis risks and to optimise control programmes. The population of five villages about 1,900 inhabitants living in the same irrigated area (Sébéri) was examined at the end of 1999 before treatment and surveyed two and ten months after treatment by praziquantel in order to investigate re-infections. In parallel, the transmission sites were subject to a semi-monthly malacological follow-up from 1998 to 2001 and the water contacts were quantified in the sites of the main village during 2000. Before treatment, schistosomiasis risks appeared related to the proximity between habitat and lateral canals: the infections concerning youngers were all the more intense that the dwellings were close to the canal. The parasitological indices were the highest in the village lacking of other water sources. The morbidity indices followed a similar distribution with maximum values in the children of the 3 villages located to less than 1 km from the canal; however, morbidity was mainly observed in the adult population, in particular male, of the 2 villages which were the most distant from the canal. After treatment, the incidence of the re-infection between 2 and 10 months was comparable in the 3 villages close to the canal (28%) but was significantly weaker in the 2 villages far from the transmission sites (5%). In the villages bordering the canal, the incidence in the children was all the more high since the habitat was close to the canal. Between 1999 and 2000, the collected number of Bulinus truncatus decreased from 1.4 to 0.6 individuals per survey; moreover, no mollusc harbouring parasites was found, representing the decrease of the parasite burden. The abnormal weakness of re-infection, regarding this type of focus, could be explained by the repeated stop of water supply inducing a complete drying out of the canal for 2 months during the year preceding the study. These repeated drying out also resulted in a reduction of the exposure. Whereas the average frequentation of the sites of the canal remained rather comparable between January (cold dry season) and May (dry hot season), it decreased dramatically in September (rainy season but canals were not irrigated this year) from 99 to 11 daily contacts. The use of the lateral canal when filled represented 80% of the contacts. In the event of drying out, 80% of the contacts were transferred in the ponds but not in the river (5% of the contacts whatever the season). These results confirmed (1) that the presence of canals reduced the use of natural sites and (2) that the drying out of the canals induced a total reduction of the contacts.
Asunto(s)
Agricultura/métodos , Schistosoma haematobium/aislamiento & purificación , Esquistosomiasis Urinaria/transmisión , Contaminación del Agua , Agua/parasitología , Adolescente , Adulto , Animales , Bulinus/parasitología , Niño , Preescolar , Desecación , Vectores de Enfermedades , Ambiente , Femenino , Humanos , Incidencia , Lactante , Masculino , Niger/epidemiología , Praziquantel/uso terapéutico , Recurrencia , Riesgo , Ríos , Esquistosomiasis Urinaria/tratamiento farmacológico , Esquistosomiasis Urinaria/parasitología , Esquistosomicidas/uso terapéutico , Estaciones del Año , Orina/parasitología , Abastecimiento de AguaRESUMEN
Located in an area where Schistosoma haematobium is hyperendemic, the town of Niamey is a focus of hypoendemicity. The aim of the malacological follow-up studies undertaken over a one year period was the determination of the mollusc species present in the water bodies, the appreciation of their space-time distribution of the snail and to find out the potential seasons of transmission. The investigation applied to 22 sites of transmission in the urban community. Four molluscs species (Bulinus truncatus, B. forskalii, B. globosus and B. senegalensis) are collected. The first three species are present all the year long, with a peak of density in the dry season. The last species (B. senegalensis) is found only during the rainy season. B truncatus and B. senegalensis are the two naturally infested species. The main site of transmission is the river Niger. The ponds play a secondary role in the peripheral districts. The main intermediate host of S. haematobium is B. truncatus.
Asunto(s)
Schistosoma haematobium/aislamiento & purificación , Esquistosomiasis Urinaria/transmisión , Animales , Bulinus/crecimiento & desarrollo , Bulinus/parasitología , Humanos , Niger/epidemiología , Densidad de Población , Esquistosomiasis Urinaria/epidemiología , Estaciones del Año , Agua/parasitologíaRESUMEN
Urinary schistosomiasis is endemic in the Niger river valley. The aim of the present study was to assess the efficacy and side effects of a single oral dose of praziquantel at 40 mg/kg in the treatment of schistosomiasis. The investigation took place between April 5, 1999 and May 25, 1999. A total of 318 primary school children, aged from 6 to 16 years, of a Schistosoma haematobium endemic area were included in the survey. They underwent a macroscopic and parasitological examinations of the urine before treatment and two and six weeks after treatment. Treatment with praziquantel was given at 40 mg/kg of body weight in a single dose. Side effects due to praziquantel were assessed within the first 4 hours, and 24 hours after. Side effects were frequent (53.7%), especially occurring in the first four hours. Their expression was not associated with the sex of the child nor the intensity of the infestation. We noted that elder children expressed more complaints. The most frequent symptoms were abdominal pains, headaches and pruritus. All these signs were without gravity and resolved within the first twenty-four hours. Before treatment, the prevalence of infestation was 98%. Six weeks after treatment, 32% of children remained positive despite a marked reduction of egg excretion. In this survey, the side effects of the treatment were very frequent but without gravity. Using praziquantel, 68% of the subjects were cured completely. Urinary schistosomiasis control programs can continue to use it for mass treatment without risk.
Asunto(s)
Antihelmínticos/uso terapéutico , Praziquantel/uso terapéutico , Esquistosomiasis Urinaria/tratamiento farmacológico , Antihelmínticos/efectos adversos , Niño , Femenino , Hematuria , Humanos , Masculino , Niger/epidemiología , Recuento de Huevos de Parásitos , Praziquantel/efectos adversos , Esquistosomiasis Urinaria/epidemiología , Esquistosomiasis Urinaria/orinaRESUMEN
During a Schistosoma haematobium morbidity control program in Niger, we conducted a survey to describe rhe resolution of lesions after treatment with praziquantel. to determine reinfection rates and to define retreatment schedules. 114 schoolchildren (7-15 years old) living in an hyperendemic village underwent 10 successive examinations over 34 months following an initial evaluation and the administration of 40 mg/kg of praziquantel. All children, whether apparently infected with S. haematobium or not, were treated. Egg output, microhaematuria, visual aspect of urine and abnormalities of the urinary tract by ultrasound were assessed. The initial prevalence tif infection was 74.5%. Reinfection began 5 months after treatment and the final prevalence was 47.1%. Bladder abnormalities decreased rapidly, but incompletely, probably due to reinfestation: initial prevalence: 89.5%). Their prevalence increased 8 months after treatment to 72.4% at month 34. Dilatations of the upper urinary tract regressed more slowly but constantly until the end of the study (initial prevalence: 43%; 4.6% at month 34), Three years after treatment, despite reinfection, the general morbidity level (prevalence and severity of lesions) was lower than at baseline in our cohort, which would suggest the advantage of a long interval between mass treatments in the epidemiological context of our survey.