[Urban transmission of schistosomiasis in children from a neighborhood of Salvador, Bahia]. / Transmissão urbana de esquistossomose em crianças de um bairro de Salvador, Bahia.

In the Subúrbio Ferroviário region of Salvador (Bahia, Brasil) occurrences of schistosomiasis were found. This fact motivated the investigation of the prevalence of the eggs in a group of 268 resident students in one of its neighborhoods (São Bartolomeu). The parasitological test analyzed by the Kato-Katz methodology, showed positive results in 30.2% of the children, ranging from 24 to 2,160 eggsSchistosoma mansoni/gram of feces. Infection was predominant in boys and in those 10 years old and over. Observation revealed that infection predominated in children that live close to natural water bodies. This region was where the three registered cases of hepatosplenicos occurred. Moreover, all the 81 children infected with Schistosoma mansoni eggs were born and live in the study area. Since this neighborhood presents all the elements of the epidemiological chain of Schistosoma mansoni, the evidences strongly suggests the urban transmission of this infection.

Analysis of Schistosoma mansoni population structure using total fecal egg sampling.

Many parasite populations are difficult to sample because they are not uniformly distributed between several host species and are often not easily collected from the living host, thereby limiting sample size and possibly distorting the representation of the population. For the parasite Schistosoma mansoni, we investigated the use of eggs, in aggregate, from the stools of infected individuals as a simple and representative sample. Previously, we demonstrated that microsatellite allele frequencies can be accurately estimated from pooled DNA of cloned S. mansoni adults. Here, we show that genotyping of parasite populations from reproductively isolated laboratory strains can be used to identify these specific populations based on characteristic patterns of allele frequencies, as observed by polyacrylamide gel electrophoresis and automated sequencer analysis of fluorescently labeled PCR products. Microsatellites used to genotype aggregates of eggs collected from stools of infected individuals produced results consistent with the geographic distribution of the samples. Preferential amplification of smaller alleles, and stutter PCR products, had negligible effect on measurement of genetic differentiation. Direct analysis of total stool eggs can be an important approach to questions of population genetics for this parasite by increasing the sample size to thousands per infected individual and by reducing bias.

Transmissão urbana de esquistossomose em crianças de um bairro de Salvador, Bahia / Urban transmission of schistosomiasis in children from a neighborhood of Salvador, Bahia

Na região do Subúrbio Ferroviário da cidade do Salvador (Bahia, Brasil), foram relatados casos de esquistossomose, e isso motivou este estudo de prevalência em 268 escolares residentes em um dos seus bairros (São Bartolomeu). Em 30,2 por cento das crianças, o exame parasitológico (Kato-Katz) foi positivo, com carga parasitária entre 24 a 2.160 ovos de Schistosoma mansoni/g de fezes, predominando entre os meninos e nos maiores de 10 anos de idade. Nas crianças com residências mais próximas das coleções naturais de água, ocorreu maior freqüência de eliminadores de ovos e nela residiam os três únicos casos com a forma hepatosplênica da esquistossomose. Também, todas as 81 crianças com ovos de Schistosoma mansoninas fezes nasceram e sempre residiram na área de estudo. Como nesse bairro há todos os elementos da cadeia epidemiológica do Schistosoma mansoni, são fortes as evidências da transmissão urbana dessa infecção.

In the Subúrbio Ferroviário region of Salvador (Bahia, Brasil) occurrences of schistosomiasis were found. This fact motivated the investigation of the prevalence of the eggs in a group of 268 resident students in one of its neighborhoods (São Bartolomeu). The parasitological test analyzed by the Kato-Katz methodology, showed positive results in 30.2 percent of the children, ranging from 24 to 2,160 eggsSchistosoma mansoni/gram of feces. Infection was predominant in boys and in those 10 years old and over. Observation revealed that infection predominated in children that live close to natural water bodies. This region was where the three registered cases of hepatosplenicos occurred. Moreover, all the 81 children infected with Schistosoma mansoni eggs were born and live in the study area. Since this neighborhood presents all the elements of the epidemiological chain of Schistosoma mansoni, the evidences strongly suggests the urban transmission of this infection.