Biomphalaria alexandrina

About: Biomphalaria alexandrina is a research topic. Over the lifetime, 413 publications have been published within this topic receiving 3781 citations.

Cercarial production from Biomphalaria alexandrina infected with Schistosoma mansoni.

Abstract: The present paper deals with longitudinal and cross-sectional methods of counting cercariae shed from Biomphalaria alexandrina in Egypt, both experimentally and naturally infected with schistosomes. By the longitudinal method, the daily output of cercariae was counted from the first shedding from experimentally infected snails and from the day of collection from naturally infected ones. The results show that the size of the snails at the time of shedding exerts a very large effect on the output of cercariae and that the numbers obtained in the laboratory are not representative of cercarial output in the field. By the cross-sectional method, the cercarial output in the first 24 hours from infected snails collected in different months from the field was counted. The results show that output is size-specific. When the size-specific output is adjusted to the size-composition of infected snails taken from the field, it is estimated that the daily output from infected snails in the field may be 957.7 cercariae. However, this number may vary with the season.

Is Schistosoma mansoni replacing Schistosoma haematobium in the Fayoum

Abstract: Schistosoma mansoni is progressively replacing S. haematobium along the Nile River in Egypt. This change has occurred in the past 15–20 years following construction of the Aswan High Dam in the 1960s. The cause is a shift in relative abundance of the snail vectors Biomphalaria alexandrina and Bulinus truncatus. Biomphalaria is increasing while the latter has disappeared from a village in the Fayoum where formerly only schistosomiasis haematobia was endemic. A cross-sectional household survey in this village in 1991 showed the following prevalence values: S. mansoni, 22.3%; S. haematobium, 3.4%; and mixed infections, 2.8%. Only two children less than 10 years of age had S. haematobium infections. A review of the local Ministry of Health records showed that 1) both species were parasitologically diagnosed during the past 7.5 years, 2) Biomphalaria had been abundantly present in the local waterways for the past 10 years and has been found infected with S. mansoni since 1985, 3) Bulinus has not been detected in the local canals and drains since 1986 and the few found between 1981 and 1985 were not infected, and 4) Biomphalaria in this village and in two others in the Fayoum were believed infected by laborers from the Delta who helped build schools in 1984. This change in the distribution of schistosomiasis will impact upon public health and medical practice in Middle and Upper Egypt as it already has in Lower Egypt.

A molecular survey of biomphalaria in egypt: is b. glabrata present?

Abstract: Two species of Biomphalaria are reported from Egypt, the indigenous Biomphalaria alexandrina and Biomphalaria glabrata, the latter believed to be introduced during the past few decades. Both are known to be excellent hosts of Schistosoma mansoni, the human-infecting blood fluke common in Egypt. Given the concerns regarding the spread of the exotic B. glabrata, this study was carried out to get a more current picture of the status of Biomphalaria in Egypt. Snail collections were undertaken during 2002-2003 from regions between Alexandria and Ismailia in the north of the Nile Delta, to as far south as Abu Simbel at Lake Nasser. Biomphalaria snails were found in 37 out of 76 sampled localities and were widely distributed in the Nile Delta and along the Nile as far south as Aswan. According to the results of species-specific polymerase chain reaction assays that sampled both nuclear and mitochondrial genomes, and according to DNA sequence data, all Biomphalaria collected during this survey were B. alexandrina. There was no evidence of the presence of B. glabrata or of hybridization of B. alexandrina with B. glabrata in the examined sites. The results were surprising given that some field-collected snails strongly resembled B. glabrata in both size and conchology and that previous survey work suggested B. glabrata had established in Egypt. Continued scrutiny to ascertain the possible presence of B. glabrata in Egypt is warranted. Also, the planorbid Helisoma duryi was detected in the Delta and as far south as Aswan, so it is important for Egyptian schistosomiasis workers to accurately distinguish this non-schistosome-transmitting snail from Biomphalaria.