Department of Biological Sciences
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Item Parasitologic survey of Onchocerca volvulus infection in the Nimiyama Chiefdom, Kono District, Sierra Leone.(National Institutes of Health, 1989-07-01) Gbakima, A AInfection due to Onchocerca volvulus was investigated in the Nimiyama Chiefdom, Kono District, Sierra Leone, where Simulium damnosum s.l. is known to breed but no data on the prevalence and intensity of O. volvulus infection exists. Of the 735 individuals sampled by the skin snip method in five villages, 471 (64%) were infected. The infection rate for males was significantly (p less than 0.05) higher than that of the females. Two hundred and ninety-one (70.0%) of the 416 males skin snipped and 180 (56.0%) of the 323 of their female cohorts were infected. The intensity of infection increased with age, with the younger cohorts presenting lower microfilarial density (MFD). Palpable nodules were observed in 230 (48.4%) of individuals found positive for skin microfilariae and in 37 (5.0%) individuals found negative for skin microfilariae. It is concluded that O. volvulus infection is mesoendemic in the Nimiyama Chiefdom, with the intensity of infection increasing with age.Item Onchocerca Volvulus infection in Sierra Leone: relation between prevalence, intensity of infection, and ocular problems in a 'forest' region.(National Institutes of Health, 1992) Gbakima, A AA two-year longitudinal study carried out in five villages in a forest region of Gorama Chiefdom, Kono District, Sierra Leone, revealed that infection with Onchocerca volvulus was hyperendemic, the overall rate of infection being 61.6%. Prevalence rose from 28.6% in the 1-5-year age group, peaking among the 21-30-year age group (82.5%) and then levelling off. The intensity of infection though low, peaked in the 31-40-year-old males and in the 41-50-year-old female cohorts. The iliac crest was more sensitive for microfilarial (mf) recovery than the shoulder and the outer canthus. The majority of the nodules were located in the pelvic region. Microfilariae invasion of the eye was low, with low anterior chamber lesions but high posterior chamber lesions comprising mainly optic atrophy and choroidoretinitis. The rate of blindness was 1.6%, ocular onchocerciasis being the leading cause of blindness followed by cornea opacities.Item Anti‐Onchocerca volvulus Immunoglobulin Subclass Response in Children from Sierra Leone(Wiley, 1992-12-01) Gbakima, A AThe humoral immune responses of a paediatric population of 224 children, 2-15 years of age, residing in an onchocerciasis endemic area of Sierra Leone, were studied to gain information that may be useful in the serodiagnosis of prepatent and low-level infections with Onchocerca volvulus. The antigen-specific levels of IgG and IgG4 were determined and evaluated in the context of the parasitological status of the child. Over 87% of the microfilaria-negative children had significant levels of antigen-specific antibodies against O. volvulus, suggesting that a large percentage of this paediatric population were harbouring prepatent or low-level infections. Over 60% of the children in the group that had detectable numbers of microfilariae in skin snips had elevated levels of O. volvulus-specific IgG4. In contrast, only 23% of the microfilaria-negative children had detectable IgG4 responses. The results presented here indicate that measures of O. volvulus-specific IgG4 may be a useful indicator of the parasitological status of children during the very early stages of onchocerciasis.Item Intestinal parasitic infections among rural farming communities in eastern Sierra Leone.(National Institutes of Health, 1995-06-01) Gbakima, A AA study carried out in four rural, mainly farming villages in the Gorama Chiefdom, Kono District, Eastern Sierra Leone revealed that intestinal helminth infections are prevalent in this area of Sierra Leone. Out of the 1164 persons of all ages who were examined, 853 (73.5%) proved positive for at least one intestinal helminth infection. Ascaris lumbricoides was the most common helminth encountered (37.5%), followed by hookworms, 12.9%; Trichuris trichiura, 12.6%; Schistosoma mansoni, 5.6%; Strongyloides stercoralis, 3.8%; tapeworms 1.0%, and multiple infections were common. Adults used poorly built pit latrines, while children defecated indiscriminately and unsupervised around houses and in the nearby bush. In addition, in most of the villages, domestic water was obtained from polluted streams and rivers. Only one village had protected pipe borne water supply. The high prevalence of intestinal helminth infections in this area results from constant infection and reinfection caused by poor sewage disposal, poor environmental health, and the low socioeconomic status prevailing in these communities.Item Saulea vitrea and low prevalence of schistosomiasis.(National Institutes of Health, 1996-03-01) Gbakima, A AThirty-six sties, including pools, small streams, large rivers, and rice fields swamps were examined for the intermediate snail hosts of schistosomiasis and other mollusca in 19 villages spanning 4 chiefdoms in Sierra Leone. Half of the Saulea vitrea collected were examined for possible infection and none was found to be infected. In addition, we examined 785 stool and 913 urine samples from children living in the villages and found low prevalence and intensity of S. haemotobium (1.8%; 1.9XG) and S. mansoni (1.9%; 2.1XG) respectively. The low prevalence and intensity of infection with schistosomiasis where S. vitrea is in abundance suggest some effect of S. vitrea on schistosome snail intermediate host, but the mechanism remains unknown.Item Parasitological and clinical studies on Wuchereria bamcrofti infectionin Moyamba District, Sierra Leone.(National Institutes of Health, 1996-05-01) Gbakima, A AA total of 302 people were examined in 3 villages in the Moyamba District, Sierra Leone of microfilaria (mf) and clinical signs of Wuchereria bancrofti infection. Mf rates were 34.5% and 31.8% for Bonganema, Old Mosongo and Pelewahun respectively. The average mf rate of those examined was 34.8%. Analysed by age and sex, the highest mf rates were observed in males of age >/=21 years (46 - 56%). The relative risk of infection was significantly lower (P /=11 years showed that recurrent fever was the commonest clinical sign observed and the rate was 5.9%. For the ages >/=41 years, the recurrent fever was 10%. The average hydrocele and elephantiasis rates were 2.5% and 1.1% respectively. For the ages >/=41 years, the hydrocele and elephantiasis rates were 4% and 3% respectively, indicating that Filariasis is an important public health problem in the area. Annual mass treatment of the study area residents with ivermectin for onchocerciasis has begun. Ivermectin has been reported to be effective for control of lymphatic Filariasis. The displacement of the population due to the undeclared war in the area will certainly negate the effects of the mass treatment programme.Item Integrated control of Onchocerca volvulus infection in a hyperendemic zone in Sierra Leone.(National Institutes of Health, 1996-03-01) Gbakima, A AA simplified integrated method of onchocerciasis control involving mass chemotherapy with ivermectin, nodulectomy and health education was carried out in south central Sierra Leone. The prevalence of Onchocerca volvulus in the village community ranged from a low of 7.4% among the International School children to a high of 97.0% in Gbessebu. There was a significant (3-4%) overall reduction in the rate of infection after one year of ivermectin treatment (G = 2565.97, df = 11, P < 0.001). In addition, ivermectin treatment had a significant effect on the college community (G = 1168.21, df = 5, P < 0.001) and from year to year (G = 187.29, df = 1, P < 0.001), though the effect indicates the reduction varied between communities. Mass ivermectin treatment significantly (G = 1 3.79, df = 1, P < 0.005) reduced the rate of infection among school children, while the prevalence and intensity of infection was reduced by nodulectomy. Health education involving the community gave us an entry point and allowed us to gain the maximum cooperation and participation from the communities.Item Immunoglobulin G subclass responses of children during infection with Onchocerca volvulus(American Society for Microbiology, 1996) Gbakima, A ATo characterize the patterns of immunoglobulin G (IgG) subclass and IgE reactivity during the early stages of onchocerciasis, sera were collected from 224 children (age groups, 2 to 5, 6 to 10, and 11 to 15 years) residing in a region of Sierra Leone where Onchocerca volvulus is endemic, and these samples were tested by enzyme-linked immunosorbent assay for their reactivity to adult antigens (OvAg) and against four recombinant proteins (OV11, OV27, OV29, and OV16). Over 88% of the samples contained detectable levels of anti-OvAg IgG. In samples from microfilaria (MF)-positive children, IgG4 responses were significantly elevated and constituted on average 39, 35 and 28% of the total IgG responses for the age groups of 2 to 5, 6 to 10, and 11 to 15 years, respectively. For MF-negative individuals, the mean contributions of IgG4 to the total IgG response were 11% (2 to 5 years), 27% (6 to 10 years), and 56% (11 to 15 years). OvAg-specific IgE was detectable in the sera from both MF-negative and MF-positive individuals. To increase the specificity of the response, recombinant antigens OV11, OV27, and OV29 were tested individually or as a cocktail. Nearly 50% of the MF-negative children and 85% of the MF-positive children had detectable levels of IgG against at least one of the recombinant antigens. Only a small portion of the IgG against the recombinant peptides was IgG4. The prevalence of IgG against OV16 in samples from MF-negative children was 51%, and that for MF-positive children was 75%. The general profile of the humoral immune responses mounted by both MF-positive and a large percentage of the MF-negative children during the initial phases of infection with O. volvulus is similar to the profile reported for adults harboring chronic O. volvulus infections. These results suggest that very quickly after infection, the interactions between parasite and host result in an immunological environment that may contribute to the maintenance of a long-term, chronic infection.Item Filariasis in the Kaiyamba Chiefdom, Moyamba District Sierra Leone: an ep demiological and clinical study(Elsevier BV, 1996-05-01) Gbakima, A AIn a cross-sectional epidemiological and clinical study of human filariasis, 630 individuals were examined for Onchocerca volvulus, Wuchereria bancrofti and Mansonella perstans infections in five communities in the Kaiyamba Chiefdom, Moyamba District, Sierra Leone. The overall prevalence of O. volvulus infection in males 144(39.1%) and females 94(35.9%) was not significantly different and the sex prevalence rate between communities was also not significant (G = 3, d.f. = 4, P > 0.05). Prevalence of O. volvulus was significantly lower (G = 42.331, d.f. = 5, P < 0.001) in the 5-9 age group (13.3%) compared to the 40-49 age group (61.9%). Sixty-four (10.2%) and 38(6.0%) of individuals examined were positive for W. bancrofti and M. perstans infections respectively and prevalence of both infections in the five communities was not significant. Mixed infections with the all three filaria parasites were recorded in 10(3.2%) of the individuals. One hundred and sixty-four (71.3%) clinical cases due to W. bancrofti were inflammatory in nature; 36.5% were chronic, of which, 26.6% were hydroceles and 9.4% involved elephantiasis of both the scrotum and the lower legs. All 19(3.0%) of M. perstans-related clinical cases were inflammatory. Ninety-three(63.3%) of O. volvulus positive individuals that presented symptoms were inflammatory in nature, 14(9.5%) had ocular symptoms and 57(38.8%) had subcutaneous nodules. These data indicate that infections due to O. volvulus, W. bancrofti and M. perstans may be of public health importance in Sierra Leone.