Preliminary study on temporal variations in biting activity of Simulium damnosum s.l. in Abeokuta North LGA, Ogun State Nigeria

<p>Abstract</p> <p>Background</p> <p><it>Simulum damnosum </it>Theobald <it>sensu lato </it>(<it>s.l</it>.) is the vector of the parasitic filarial worm <it>Onchocerca volvulus </it>Leuckart which causes onchocerciasis. In order to understand the vector population dynamics, a preliminary 12 months entomological evaluation was carried out at Abeokuta, the Southwest Zone of Nigeria, an onchocerciasis endemic area, where vector control has not been previously initiated. <it>S.damnosum s.l</it>. flies were caught on human attractants between 700 to1800 hours each day, for 4 days each month, from August 2007 to July 2008. The flies caught were classified as either forest-dwelling or savanna-dwelling groups based on the colour of certain morphological characters. Climatic data such as rainfall, humidity and temperature were also collected monthly during the period of survey.</p> <p>Results</p> <p>A total of 1,139 flies were caught, 596 (52.33%) were forest-dwelling group while 543 (47.67%) were savanna-dwelling group of <it>S. damnosum s.l</it>. The highest percentage of forest-dwelling group was caught in the month of August 2007 (78.06%) and the least percentage of forest-dwelling groups was caught in November 2007 (8.14%). The highest percentage of savannah-dwelling group was caught in the month of November 2007 (91.86%) and the least percentage of savannah-dwelling group was caught in August 2007 (21.94%). There was no significant difference between the population of forest and savannah-dwelling groups of the fly when the means of the fly population were compared (<it>P </it>= 0.830). Spearman correlation analysis showed a significant relationship between monthly fly population with monthly average rainfall (<it>r </it>= 0.550, n = 12, <it>P </it>= 0.033), but no significant relationship with monthly average temperature (<it>r </it>= 0.291, <it>n </it>= 12, <it>P </it>= 0.179). There was also a significant relationship between monthly fly population and monthly average relative humidity (<it>r </it>= 0.783, <it>n </it>= 12 <it>P </it>= 0.001). There was no significant correlation between the population of forest-dwelling group of <it>S. damnosum s.l</it>. and monthly average rainfall (<it>r </it>= 0.466, <it>n </it>= 12, <it>P </it>= 0.064) and monthly average temperature (<it>r </it>= 0.375, n = 12, <it>P </it>= 0.115) but there was significant correlation with monthly average relative humidity (<it>r </it>= 0.69, <it>n </it>= 12, <it>P </it>= 0.006). There was significant correlation between savannah-dwelling group and monthly average rainfall (<it>r </it>= 0.547, <it>n </it>= 12, <it>P </it>= 0.033), and monthly average relative humidity (<it>r </it>= 0.504, <it>n </it>= 12, <it>P </it>= 0.047) but there was no significant correlation with monthly average temperature (<it>r </it>= 0.142, <it>n </it>= 12, <it>P </it>= 0.329)</p> <p>Conclusion</p> <p>The results from this study showed that both the forest and the savannah dwelling groups of <it>S. damnosum s.l</it>. were caught biting in the study area. This could have implications on the transmission and epidemiology of human onchocerciasis if not monitored.</p

Urinary schistosomiasis among preschool children in a rural community near Abeokuta, Nigeria

<p>Abstract</p> <p>Background</p> <p>The control of schistosomiasis in Nigeria is mainly by mass treatment with praziquantel through the school system, with an absence of any provision for pre-school children. We therefore determined the prevalence and intensity of urinary schistosomiasis in pre-school children between the ages of 1-6 years in Ilewo-Orile a rural and endemic community, near Abeokuta, Nigeria as part of providing information on the neglected tropical diseases among this age group. Two urine samples were collected from each pre-school child. The samples were tested for microhaematuria using reagent strips and then processed and examined with a microscope for <it>Schistosoma haematobium </it>ova.</p> <p>Results</p> <p>Of the 167 children examined 97 (58.1%) had infection, with no significant difference (P = 0.809) in infection rates between boys (57.1%) and girls (59.2%). Both prevalence and intensity of infection did not increase significantly with age (P = 0.732). The overall geometric mean egg count was 1.17 eggs/10 ml urine. There was no significant association (<it>P </it>= 0.387) between intensity in boys (1.16 eggs/10 ml urine) and girls (1.19 eggs/10 ml urine). 47.4% of the children had microhaematuria which did not increase significantly with age (P = 0.526). Focus group discussions with guardians and caregivers revealed that infection of pre-school children early in life was due to exposures through bathing in the stream by their mothers, while the older children would visit the stream for washing, fetching of water, bathing and swimming.</p> <p>Conclusion</p> <p>Community participatory health education is needed in this community as a first step in reducing infection and transmission of the disease, while the rehabilitation and repair of the existing water borehole system in the community should be effected. The results of this study have shown that pre-school children also harbour infection and are a source of transmission of schistosomiasis in endemic communities. Planning and provision for their treatment should be considered in control programmes.</p

Biting behaviour of Simulium damnosum complex and Onchocerca volvulus infection along the Osun River, Southwest Nigeria

<p>Abstract</p> <p>Background</p> <p>Studies on biting behaviours and infectivity status of insect vectors are pre-requisites in understanding the epidemiology of the vector- borne diseases and planning effective control measures. A longitudinal study was carried out to investigate the transmission index of <it>Simulium damnosum </it>complex species along Osun River, South Western Nigeria. Adult flies were collected on human attractants from 07:00 to 18:00 hours for two consecutive days from February 2008 to June 2009 at three communities: Osun Eleja, Osun Ogbere and Osun Budepo. The infectivity rate was determined by dissection and Polymerase Chain Reaction amplification (PCR) of 0-150 genes of <it>Onchocerca </it>parasite using the pool screening technique.</p> <p>Results</p> <p>The results indicated that the majority of the flies collected at the three sampling points were nulliparous as they accounted for 53.90%, 57.86% and 59.58% of the flies dissected at Osun Budepo, Osun Ogbere and Osun Eleja, respectively. The parous rate was higher during the dry season than the wet season but the difference was not statistically significant (<it>p </it>< 0.05). The biting activity of the parous flies showed two peaks at Osun Budepo and three peaks at Osun Eleja and Osun Ogbere. Of the 1,472 flies dissected and 1,235 flies screened by molecular method, none was infected with <it>Onchocerca </it>parasite at the three sampling points however the annual biting rates at the three communities were higher than 1,000 considered as tolerable value for a person living in an onchocerciasis zone by Word Health Organization.</p> <p>Conclusion</p> <p>The study has provided the baseline data for further study on onchocerciasis transmission dynamics and the need to intercept man- simuliid vector contact at the study area.</p

Geographical information system and predictive risk maps of urinary schistosomiasis in Ogun State, Nigeria

<p>Abstract</p> <p>Background</p> <p>The control of urinary schistosomiasis in Ogun State, Nigeria remains inert due to lack of reliable data on the geographical distribution of the disease and the population at risk. To help in developing a control programme, delineating areas of risk, geographical information system and remotely sensed environmental images were used to developed predictive risk maps of the probability of occurrence of the disease and quantify the risk for infection in Ogun State, Nigeria.</p> <p>Methods</p> <p>Infection data used were derived from carefully validated morbidity questionnaires among primary school children in 2001–2002, in which school children were asked among other questions if they have experienced "blood in urine" or urinary schistosomiasis. The infection data from 1,092 schools together with remotely sensed environmental data such as rainfall, vegetation, temperature, soil-types, altitude and land cover were analysis using binary logistic regression models to identify environmental features that influence the spatial distribution of the disease. The final regression equations were then used in Arc View 3.2a GIS software to generate predictive risk maps of the distribution of the disease and population at risk in the state.</p> <p>Results</p> <p>Logistic regression analysis shows that the only significant environmental variable in predicting the presence and absence of urinary schistosomiasis in any area of the State was Land Surface Temperature (LST) (B = 0.308, p = 0.013). While LST (B = -0.478, p = 0.035), rainfall (B = -0.006, p = 0.0005), ferric luvisols (B = 0.539, p = 0.274), dystric nitosols (B = 0.133, p = 0.769) and pellic vertisols (B = 1.386, p = 0.008) soils types were the final variables in the model for predicting the probability of an area having an infection prevalence equivalent to or more than 50%. The two predictive risk maps suggest that urinary schistosomiasis is widely distributed and occurring in all the Local Government Areas (LGAs) in State. The high-risk areas (≥ 50% prevalence) however, are confined to scatter foci in the north western part of the State. The model also estimated that 98.99% of schools aged children (5–14 years) are living in areas suitable for urinary schistosomiasis transmission and are at risk of infection.</p> <p>Conclusion</p> <p>The risk maps developed will hopefully be useful to the state health officials, by providing them with detailed distribution of urinary schistosomiasis, help to delineate areas for intervention, assesses population at risk thereby helping in optimizing scarce resources.</p

Risk model map of presence of high-risk schools for urinary schistosomiasis in Ogun State as observed and predicted through logistic regression

<p><b>Copyright information:</b></p><p>Taken from "Geographical information system and predictive risk maps of urinary schistosomiasis in Ogun State, Nigeria"</p><p>http://www.biomedcentral.com/1471-2334/8/74</p><p>BMC Infectious Diseases 2008;8():74-74.</p><p>Published online 31 May 2008</p><p>PMCID:PMC2438363.</p><p></p

Risk map of suitable areas for urinary schistosomiasis transmission in Ogun State based on predicted probability of 0

75.<p><b>Copyright information:</b></p><p>Taken from "Geographical information system and predictive risk maps of urinary schistosomiasis in Ogun State, Nigeria"</p><p>http://www.biomedcentral.com/1471-2334/8/74</p><p>BMC Infectious Diseases 2008;8():74-74.</p><p>Published online 31 May 2008</p><p>PMCID:PMC2438363.</p><p></p

Mapping and prediction of schistosomiasis in Nigeria using compiled survey data and Bayesian geospatial modelling

Schistosomiasis prevalence data for Nigeria were extracted from peer-reviewed journals and reports, geo-referenced and collated in a nationwide geographical information system database for the generation of point prevalence maps. This exercise revealed that the disease is endemic in 35 of the country's 36 states, including the federal capital territory of Abuja, and found in 462 unique locations out of 833 different survey locations. Schistosoma haematobium, the predominant species in Nigeria, was found in 368 locations (79.8%) covering 31 states, S. mansoni in 78 (16.7%) locations in 22 states and S. intercalatum in 17 (3.7%) locations in two states. S. haematobium and S. mansoni were found to be co-endemic in 22 states, while co-occurrence of all three species was only seen in one state (Rivers). The average prevalence for each species at each survey location varied between 0.5% and 100% for S. haematobium, 0.2% to 87% for S. mansoni and 1% to 10% for S. intercalatum. The estimated prevalence of S. haematobium, based on Bayesian geospatial predictive modelling with a set of bioclimatic variables, ranged from 0.2% to 75% with a mean prevalence of 23% for the country as a whole (95% confidence interval (CI): 22.8-23.1%). The model suggests that the mean temperature, annual precipitation and soil acidity significantly influence the spatial distribution. Prevalence estimates, adjusted for school-aged children in 2010, showed that the prevalence is >10% in most states with a few reaching as high as 50%. It was estimated that 11.3 million children require praziquantel annually (95% CI: 10.3-12.2 million)

Risk model map of presence of urinary schistosomiasis in Ogun State as observed and predicted through logistic regression

<p><b>Copyright information:</b></p><p>Taken from "Geographical information system and predictive risk maps of urinary schistosomiasis in Ogun State, Nigeria"</p><p>http://www.biomedcentral.com/1471-2334/8/74</p><p>BMC Infectious Diseases 2008;8():74-74.</p><p>Published online 31 May 2008</p><p>PMCID:PMC2438363.</p><p></p