Molecular approaches to the identification of Bulinus species in south-west Nigeria and observations on natural snail infections with schistosomes.

The current study considers the distribution of a small sample of 138 Bulinus snails, across 28 localities within eight Nigerian states. Snails were identified using a combination of molecular methods involving both DNA sequencing of a partial cytochrome oxidase subunit 1 (cox1) fragment and restriction profiles obtained from ribosomal internal transcribed spacer (its) amplicons. The results showed that the majority of Bulinus samples tested belonged to the species Bulinus truncatus while only two were Bulinus globosus. The use of RsaI restriction endonuclease to cleave the ribosomal its of Bulinus, as a method of species identification, was adopted for the majority of samples, this being a quicker and cheaper method better suited to small laboratory environments. Polymerase chain reaction (PCR) amplification of the schistosome Dra1 repeat within each of the collected Bulinus samples was employed to determine the extent and distribution of infected snails within the sample areas. Successful amplification of the Dra1 repeat demonstrated that 29.7% of snails were infected with schistosomes. Sequencing of the partial schistosome its from a small subset of snail samples suggested that some snails were either penetrated by both Schistosoma haematobium and Schistosoma bovis miracidia or hybrid miracidia formed from the two species.

Squamous cell abnormalities in exfoliated cells from the urine of Schistosoma haematobium-infected adults in a rural fishing community in Nigeria.

Schistosoma haematobium infection is endemic in Nigeria, with substantial transmissions in all the states of the federation and a high prevalence rate in schools. Literature has linked bladder cancer, mostly squamous cell type, with long-term S. haematobium infections. The objective of this descriptive study was to screen exfoliated cells in the urine of S. haematobium-infected patients for squamous cell abnormalities through cytopathological examinations. Study participants were drawn from Imala Odo, a community near Oyan Dam in Abeokuta North Local Government Area, Ogun state, Southwest Nigeria. Due to a considerable day-to-day variation of S. haematobium eggs in urine, 3 rounds of 200 ml of urine samples were collected on 3 different days from 32 infected patients and 10 uninfected controls and examined. Cytological preparations of the infected 15 males and 8 females and 10 controls (5 males and 5 females) were screened for squamous cell abnormalities. Severely dysplastic to frankly malignant squamous cells were observed in 1 (3.1%) male and 2 (6.3%) females, while no abnormality was observed in the controls.

Detection of schistosomes polymerase chain reaction amplified DNA by oligochromatographic dipstick.

The applications of highly specific and sensitive molecular techniques based on polymerase chain reaction (PCR) have constituted a valuable tool for the diagnosis of schistosomiasis and also for the detection of schistosome infections in the snail intermediate hosts. The common method of detecting PCR amplicons is gel electrophoresis in the presence of ethidium bromide, a carcinogen, which is followed by UV transillumination. Other methods, which are available for detecting PCR products, are real-time PCR, PCR-enzyme-linked immunosorbent assay (PCR-ELIZA) and mass spectrometry but they are cumbersome while they are sometimes complex and expensive. Therefore, a simple method of PCR product detection would be a welcome idea and a most valuable tool particularly in disease endemic countries with limited research facilities and resources. In this study, we applied a simple and rapid method for the detection of Schistosoma haematobium and Schistosoma mansoni PCR amplified DNA products using oligochromatographic (OC) dipstick. The amplicons are visualized by hybridization with a gold conjugated probe, while a control for the chromatographic migration is incorporated in the assay. The lower detection limit observed was 10fg of genomic DNA from each of the two species, while the dipstick was also specific for each of the species used in this study.

Distribution of the molecular forms of Anopheles gambiae and pyrethroid knock down resistance gene in Nigeria.

We investigated the distribution of the molecular M and S forms of Anopheles gambiae and the knock down resistance (kdr) gene associated with pyrethroid and DDT resistance in A. gambiae s.s. at 13 localities across Nigeria. Two-three days old adult female mosquito reared from larval collections were tested using standard WHO procedures, diagnostic test kits and impregnated papers to assess their pyrethroid resistance status. Specimens were identified by PCR assays and characterized for the kdr gene. DNA from adult A. gambiae s.s. collected from human dwellings were also tested for the presence of the kdr gene. The overall collection was a mix of the molecular M and S forms across the mangrove (63:37%), forest (56:44%), and transitional (36:64%) ecotypes, but almost a pure collection of the S form in the Guinea and Sudan-savanna. Results of insecticide susceptibility tests showed that mosquitoes sampled at seven localities were susceptible to permethrin, deltamethrin, and DDT, but populations of A. gambiae resistant to these insecticides were recorded at six other localities mainly in the transitional and Guinea-savanna ecotypes. The kdr gene was found only in the molecular S forms, including areas where both forms were sympatric. The overall kdr frequency was low: <47% in forest, 37-48% in the transitional, and 45-53% in Guinea-savanna. The data suggest that pyrethroid resistance in A. gambiae in Nigeria is not as widespread when compared to neighbouring West African countries.