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Onchocerciasis caused by the filarial parasite Onchocerca volvulus and transmitted by Simulium damnosum s.l. remains a public health concern in Nigeria. Infestation of S. damnosum s.l. along rivers Gurara and Kaduna; and heavy intensity of O. volvulus infection in Kaduna were documented in 1956. Control of onchocerciasis in Kaduna started 1954 with larviciding using dichlorodiphenyltrichloroethane reduced S. damnosum s.l. population by 94% in 1966. Diethylcarbamazine used for human treatment was discontinued due to toxicity. Kaduna State Ministry of Health and its partners built on this achievement; used annual mass administration of ivermectin consistently between 1989 and 2017 which led to interruption of onchocerciasis transmission in 2018. This study investigated possibility of recrudescence of onchocerciasis with the hypothesis that insecurity-induced migration could cause recrudescence of onchocerciasis. Six out of the 23 Local Government Areas (LGAs) in Kaduna State were selected for evaluation. Adult S. damnosum s.l. were captured across seven breeding sites using human landing collectors from July to October 2023. Pooled screen assays of 72 pools heads of black flies were conducted using quantitative polymerase chain reaction (qPCR) for O. volvulus detection. Dried blood samples from 3107 children aged 5-9 years were collected; with 1502 samples analysed using alkaline phosphatase enzyme-linked immunosorbent assay due to financial constraints. Twenty pools of the 72 pools of heads (27.8%) of S. damnosum s.l. analysed were positive for O. volvulus in Kagarko and Kachia LGAs (> 1/2000 infective flies; 95% upper confidence limit 0.49) with qPCR prevalence of 0.32%. Two children from security compromised communities tested seropositive (prevalence 0.31%; 95% upper confidence limit 0.317). The findings demonstrated ongoing onchocerciasis transmission in Kaduna despite the interruption in 2018. This calls for evaluation of the extent of recrudescence and identification of key drivers such as human migration, fly movement and insecurity.

Background Interest in biobanking for collection of specimens for non-communicable diseases research has grown in recent times. This paper explores the perspectives of Nigerians on donation of specimen for the biobanking research. Methods We conducted 16 Focus Group Discussions (FGD) with individuals from different ethnic, age and socio-economic groups in Kano (North), Enugu (Southeast), Oyo States (Southwest) and Abuja, the Federal Capital Territory (Central) of Nigeria. We used topic guides and prompt statements to explore the knowledge and understanding of interviewees to general issues about biobanking of biospecimens, their use and specifically about role of biobanking in non-communicable diseases research. Results A total of 123 individuals participated in 16 focus group discussions in 2011. Our participants had limited knowledge of the concept of biobanking but accepted it once they were educated about it and saw it as a worthwhile venture. Half of our study participants supported use of broad consent, a quarter supported restricted consent while the remaining quarter were in favour of tiered consent. Most discussants support shipment of their samples to other countries for further research, but they prefer those collaborations to be done only with competent, ethical researchers and they would like to receive feedback about such projects. The majority preferred health care as a benefit from participation, particularly for any unexpected condition that may be discovered during the course of the research instead of financial compensation. Participants emphasized the need to ensure that donated samples were not used for research that contradicts their religious beliefs. Conclusions Our study demonstrates that our participants accepted biobanking once they understand it but there were different attitudes to elements of biobanking such as type of consent. Our study highlights the need to carefully document population attitudes to elements of modern scientific research and the consenting process.

Background Entomological data for onchocerciasis surveillance relies on sampling black flies through human landing collectors in the field and laboratory testing of the flies for infection using pooled screening O-150 PCR-ELISA assay. Both techniques require improvements. This study aimed to optimize the Esperanza Window Trap (EWT) for black fly collection. We tested alternative carbon dioxide (CO 2 ) mimics to attract black flies to the traps. Additionally, we evaluated new quantitative PCR (qPCR) methods that target mitochondrial DNA markers and have been proposed to enhance the sensitivity and specificity for detecting Onchocerca volvulus infections in blackflies. Methods Traps baited with low, medium and high release rates of either 2-butanone or cyclopentanone as CO 2 mimics were field tested against traps baited with organically generated CO 2 in four ecological zones in Nigeria: Guinea savannah, derived savannah, rainforest and montane forest. The performance of EWTs baited with CO 2 or in combination with 2-butanone (low release) were subsequently evaluated against the human landing collection (HLC). Trap scaling was also pilot tested by comparing two EWTs to a single HLC team. Collected black flies were used to test detection of O. volvulus in black flies using Ov ND5 real-time PCR (qPCR) compared to the conventional pool screening O-150 PCR. Results EWTs baited with 2-butanone caught similar numbers of black flies ( Simulium damnosum s.l.) to those baited with CO 2 , while cyclopentanone collected significantly fewer flies in all locations. The low release of 2-butanone was the most effective overall, although HLCs collected higher numbers of black flies than EWT baited with CO 2 either singly or in combination with low-release 2-butanone. The combination of two EWTs baited with CO 2 and deployed 100 m apart from each other collected similar numbers of flies as one HLC. More black fly pools were positive for O. volvulus by Ov ND5 qPCR compared with O-150 PCR in derived savannah (31.15 vs. 15.57%), montane forest (11.54 vs. 0%) and rainforest (23.08 vs. 2.56%), with only one positive pool in Guinea savannah detected by both methods. Conclusions The 2-butanone has potential to be used in xenomonitoring as a standardized replacement for organically generated CO 2 . Ov ND5 qPCR detected more positive pools than O-150 PCR. The positive pools found in foci hitherto considered to have interrupted/eliminated onchocerciasis highlight the need for more sensitive and specific methods that support programmatic assessments to identify and combat recrudescence. Graphical Abstract

BackgroundOnchocerciasis caused by the filarial parasite Onchocerca volvulus and transmitted by Simulium damnosum s.l. remains a public health concern in Nigeria. Infestation of S. damnosum s.l. along rivers Gurara and Kaduna; and heavy intensity of O. volvulus infection in Kaduna were documented in 1956. Control of onchocerciasis in Kaduna started 1954 with larviciding using dichlorodiphenyltrichloroethane reduced S. damnosum s.l. population by 94% in 1966. Diethylcarbamazine used for human treatment was discontinued due to toxicity. Kaduna State Ministry of Health and its partners built on this achievement; used annual mass administration of ivermectin consistently between 1989 and 2017 which led to interruption of onchocerciasis transmission in 2018. This study investigated possibility of recrudescence of onchocerciasis with the hypothesis that insecurity-induced migration could cause recrudescence of onchocerciasis.Methodology/principal findingsSix out of the 23 Local Government Areas (LGAs) in Kaduna State were selected for evaluation. Adult S. damnosum s.l. were captured across seven breeding sites using human landing collectors from July to October 2023. Pooled screen assays of 72 pools heads of black flies were conducted using quantitative polymerase chain reaction (qPCR) for O. volvulus detection. Dried blood samples from 3107 children aged 5-9 years were collected; with 1502 samples analysed using alkaline phosphatase enzyme-linked immunosorbent assay due to financial constraints. Twenty pools of the 72 pools of heads (27.8%) of S. damnosum s.l. analysed were positive for O. volvulus in Kagarko and Kachia LGAs (> 1/2000 infective flies; 95% upper confidence limit 0.49) with qPCR prevalence of 0.32%. Two children from security compromised communities tested seropositive (prevalence 0.31%; 95% upper confidence limit 0.317).Conclusion/significanceThe findings demonstrated ongoing onchocerciasis transmission in Kaduna despite the interruption in 2018. This calls for evaluation of the extent of recrudescence and identification of key drivers such as human migration, fly movement and insecurity.