Nigeria has the heaviest burden of lymphatic filariasis (LF) in sub-Saharan Africa, which is caused by the parasite Wuchereria bancrofti and transmitted by Anopheles mosquitoes. LF is targeted for elimination and the national programme is scaling up mass drug administration (MDA) across the country to interrupt transmission. However, in some regions the co-endemicity of the filarial parasite Loa loa (loiasis) is an impediment due to the risk of severe adverse events (SAEs) associated with the drug ivermectin. To better understand factors influencing LF elimination in loiasis areas, this study conducted a cross-sectional survey on the prevalence and co-distribution of the two infections, and the potential demographic, landscape, human movement, and intervention-related risk factors at a micro-level in the South West zone of Nigeria. In total, 870 participants from 10 communities on the fringe of a meso-endemic loiasis area of Osun State were selected. LF prevalence was measured by clinical assessment and using the rapid immunochromatographic test (ICT) to detect W. bancrofti antigen. Overall LF prevalence was low with ICT positivity ranging from 0 to 4.7%, with only 1 hydrocoele case identified. Males had significantly higher ICT positivity than females (3.2% vs 0.8%). Participants who did not sleep under a bed net had higher ICT positivity (4.0%) than those who did (1.3%). ICT positivity was also higher in communities with less tree coverage/canopy height (2.5–2.8%) than more forested areas with greater tree coverage/canopy height (0.9–1.0%). In comparison, loiasis was determined using the rapid assessment procedure for loiasis (RAPLOA), and found in all 10 communities with prevalence ranging from 1.4% to 11.2%. No significant difference was found by participants' age or sex. However, communities with predominately shrub land (10.4%) or forested land cover (6.2%) had higher prevalence than those with mosaic vegetation/croplands (2.5%). Satellite imagery showed denser forested areas in higher loiasis prevalence communities, and where low or no ICT positivity was found. Only one individual was found to be co-infected. GPS tracking of loiasis positive cases and controls also highlighted denser forested areas within higher loiasis risk communities and the sparser land cover in lower-risk communities. Mapping LF-loiasis distributions against landscape characteristics helped to highlight the micro-heterogeneity, identify potential SAE hotspots, and determine the safest and most appropriate treatment strategy.

The milestone in polio eradication program is to protect effectively children aged 0-5 years against the three serotypes of poliovirus. It became necessary to measure the level of neutralizing antibodies to the three poliovirus types in an endemic State in Nigeria. Neutralizing antibodies to the poliovirus types among children aged 0-5 years was estimated using micro neutralization assay. Of 129 children, 99 (76.8%), 95 (73.6%), and 95 (73.6%) had neutralizing antibodies with the geometric mean titer of 42.7, 31.3, and 33.2 for the poliovirus type 1, 2, and 3, respectively. Fifty-three percent of the children were protected against the three types of poliovirus. Combination of poliovirus types 1 and 2, 1 and 3, and 2 and 3 were neutralized by 62.8, 58.9, and 61.2% of the children studied, respectively. Only poliovirus type 1 induced antibody titres ≥1:1,024. The number of children with neutralizing antibodies after receiving three doses was significantly higher than those who received one or two doses of oral polio vaccine (P ≤ 0.05). However, those who received more than three doses of oral polio vaccine showed no significant difference in their antibody response. The existence of immunity gap poses a risk of re-emergence of the paralytic poliovirus. The existence of unimmunized and unprotected children along with high birth rate could impede the success of polio vaccination in Nigeria. Elimination of non-compliance to polio vaccine, promotion of health education and documented evidence of vaccination of each child with the parents may facilitate the success of polio eradication program in Nigeria.

IntroductionIn preparation for Mass Drug Administration by National Lymphatic Filariasis Elimination Programme, a baseline epidemiological investigation on lymphatic filariasis (LF) was conducted in two sentinel sites of Ogun State, Nigeria. The study was carried out in Ado-Odo Ota and Abeokuta South Local Government Areas (LGAs) to determine LF prevalence, microfilarial density and the abundance of Wucheraria bancrofti in the mosquito vectors.MethodsMicroscopic examination of thick blood smears of 299 and 288 participants from Ado-Odo Ota and Abeokuta South LGAs was conducted. Visual observations of clinical manifestations of chronic infection and questionnaire administration were also conducted. Indoor resting mosquitoes were collected using the pyrethrum spray technique and CDC light traps and mosquitoes were dissected for filarial larvae.ResultsMicrofilaria prevalences were 4.0% and 2.4% in Ado-odo Ota and Abeokuta South LGAs. The microflarial density (mfd) was 30.6mf/ml and 23.9 mf/ml in the same areas. No clinical manifestations of the infection were found at both sites. Knowledge of LF by inhabitants was very low in the two areas. Anopheles gambiae s.l and Culex species mosquitoes were collected but none was found positive for stage L3 infective larvae.ConclusionMass awareness campaigns on the goal of mass drug administration, cause of LF, mode of transmission, the relationship between infection and clinical signs/symptoms is advocated so as to increase acceptance and support of the control programme by the community.