Epidemiological evaluation of onchocerciasis along Ogun River System, southwest Nigeria.

Background & objective: Epidemiological studies were carried out to assess the prevalence and community microfilarial load (CMFL) of onchocerciasis after repeated annual treatment with ivermectin along Ogun river System, southwest Nigeria. Method: Skin snips were taken from consented participants in 11 selected communities along the River system. The microfilarial load of the community was estimated. Results: The prevalence and CMFL varied significantly in the communities (p <0.05). The prevalence of onchocerciasis ranged from 19.1 to 45.6%, while the CMFL ranged from 0.11 to 1.03 microfilariae per skin snip. The CMFL recorded was <5 microfilariae per skin snip, i.e. recognized by WHO as threshold value in certifying the communities to be free of onchocerciasis as public health problem, thus, signifying the possibility of onchocerciasis elimination in the study area. Conclusion: Efforts should therefore be intensified to achieve improved ivermectin coverage and compliance in annual ivermectin treatment in order to completely eliminate onchocerciasis as a public health problem in the studied communities.

Population dynamics of indoor sampled mosquitoes and their implication in disease transmission in Abeokuta, south-western Nigeria.

Background & objectives: A longitudinal study was carried out to investigate the species composition, seasonal abundance, parity and feeding preference of indoor sampled mosquitoes in Abeokuta, south-western Nigeria. Methods: The mosquitoes were sampled weekly from five stratified locations using Center for Disease Control (CDC) light-traps between August 2005 and July 2006. The mosquitoes were examined for abdominal condition and dissected for age composition. Microscopic and precipitin techniques were also employed for the determination of host blood source. Results: A total of 2969 mosquitoes which belong to 10 species of mosquitoes were collected during the study period. Mansonia africana (35.65%) constituted the most abundant species followed by Culex quinquefasciatus (32.23%) and Anopheles gambiae complex (13.52%). Other species in decreasing order of abundance were Coquilletidia maculipennis (8.2%), Aedes albopictus (5.9%), Ae. aegypti (1.93%), M. uniformis (1.81%), Cx. duttoni (0.25%), Cx. tigripes (0.25%) and An. funestus (0.25%). Seasonal abundance revealed a significant difference (p <0.05) in the population of mosquito vectors collected during the wet season as compared to the dry season and their abundance was positively correlated with rainfall. The results showed that the majority of the vector species collected were unfed and nulliparous. Moreover, the blood meal test was positive for human blood. Conclusion: The preponderance of mosquitoes observed in the study is of public health concern since they serve as vectors of most tropical diseases including malaria.

Mosquito larval habitats and public health implications in Abeokuta, Ogun State, Nigeria

Abstract: The larval habitats of mosquitoes were investigated in Abeokuta, Nigeria in order to determine the breeding sites of the existing mosquito fauna and its possible public health implications on the residents of the City. The habitats were sampled between August 2005 and July 2006 using plastic dippers and a pipette. The habitats were grouped as ground pools/ponds, gutters/open drains, tyres, domestic containers and treeholes/ leaf axils. Ten species of mosquitoes were encountered in the fi ve habitats namely Mansonia africana, M. uniformis, Culex quinquefasciatus, Aedes aegypti, Ae. albopictus, Ae. vittatus, Cx tigripes, Anopheles gambiae s.l., An. funestus and Eretmapodite clnysogaster. Ae. aegypti bred in all the habitats sampled while Cx quinquefasciatus bred in four habitats except tree holes/leaf axils. An. gambiae s.l and Ae. albopictus occurred in three habitats while other species bred only in one or two habitats. Ground pools and domestic containers recorded the highest number of species followed by gutters/open drains. Tree holes/leaf axils was the least preferred habitat with the lowest number of species occurrence. However, statistical analysis revealed non-signifi-cant difference in species occurrence in the fi ve habitats. The availability of the habitats to support the breeding of Aedes, Culex and Anopheles, which are known vectors of urban yellow fever, lymphatic fi lariasis and malaria suggest that the residents of Abeokuta City are at risk of mosquito-borne diseases. It is important that residents of the City are enlighten on the environmental factors that contribute to mosquito breeding and that the Government should institute proper sanitation measures to reduce mosquito breeding sites

MONRATE: A descriptive tool for calculation and prediction of re-infection of Ascaris lumbricoides (Ascaridida: Ascarididae)

The study presents an interactive descriptive tool (MONRATE) for calculating and predicting reinfection rates and time of Ascaris lumbricoides following mass chemotherapy. The implementation was based on the theoretical equation published by Hayashi in 1977, for time-prevalence: Y=G [1-(1-X)N-R] as modified by Jong-Yil in 1983. Using the Psuedo-Code of the MONRATE tool, the calculated monthly reinfection rates (X) for the LGAs are (names are locations in Nigeria in a region predominately populated by the Yoruba speaking tribes of Nigeria whose traditional occupations are agriculture and commerce): Ewekoro (1.6 %), Odeda (2.3 %), Ado-odo/Otta (2.3 %), Ogun Waterside (3.8 %) and Obafemi/Owode (4.2 %). The mathematical mean of ‘X’ values in the study areas for Ogun State was 2.84. The calculated reinfection time (N months) for the LGAs are varied such as Ado-odo/Otta (12.7), Ogun Waterside (21.8), Obafemi/Owode (22.92), Odeda (25.45), and Ewekoro (25.9). The mean value for N in Ogun State was 21.75. The results obtained from MONRATE were compared with those obtained using the mathematical equation and found to be the same. Rev. Biol. Trop. 55 (3-4): 755-760. Epub 2007 December, 28.

Se presenta una herramienta descriptiva e interactiva (MONRATE) para calcular y predecir las tasas y tiempo de reinfección con Ascaris lumbricoides tras un tratamiento de quimioterapia. Nos basamos en la ecuación propuesta por Hayashi en 1977 para el tiempo de prevalencia: Y=G [1- (1-X)N-R], según la modificó Jong-Yil en 1983. Utilizando el código Psuedo de la herramienta de MONRATE, las tasas de reinfección mensuales (X) para varios sitios de Nigeria, África, son: Ewekoro (1.6 %), Odeda (2.3 %), Ado-odo/Otta (2.3 %), Ogun Waterside (3.8 %) y Obafemi/ Owode (4.2 %). El promedio matemático de los valores de "X" en el área de estudio del Estado de Ogun fue 2.84. El tiempo de reinfección calculado (N meses) para LGAs es variado: Ado-odo/Otta (12.7), Ogun Waterside (21.8), Obafemi/Owode (22.92), Odeda (25.45) y Ewekoro (25.9). El valor promedio para N en el Estado de Ogun fue 21.75. Los resultados del programa MONRATE son iguales a los producidos por la ecuación.

MONRATE; a descriptive tool for calculation and prediction of re-infection of Ascaris lumbricoides

The objective of the study was to develop an interactive and systematic descriptive tool; MONRATE for calculating and predicting reinfection rates and time of Ascaris lumbricoides following mass chemotherapy using levamisole. Each pupil previously treated was retreated 6 or 7 months after the initial treatment in Ogun State; Nigeria. The implementation was based on the theoretical equation for time-prevalence: Y = G [1 -(1-X)N-R]. Using the Psuedo- Code of the MONRATE tool; the calculated monthly reinfection rates (X) for the LGAs were 1.6in Ewekoro; 2.3in Odeda; 2.3in Ado-odo/Otta; 3.8in Ogun Waterside and 4.2in Obafemi/Owode. The mathematical mean of 'X' values in the study areas for Ogun State was 2.84. The calculated reinfection time (N months) for the LGAs varied such as Ado-odo/Otta (12.7); Ogun Waterside (21.8); Obafemi/Owode (22.92); Odeda (25.45); and Ewekoro (25.9). The mean value for N in Ogun State was 21.75. The results obtained from MONRATE were compared with those obtained using the mathematical equation and were found to be the same but MONRATE was faster in computation and more accurate. It is concluded that MONRATE is a veritable tool that can be used in the execution of control programme involving mass treatment against A. lumbricoides