Loiasis is a parasitic disease caused by the filarial nematode Loa loa. This report describes loiasis in a 6-year-old child presented to a public hospital in Yaoundé, Cameroon, with an immobile worm located beneath the conjunctiva of the left eye. The calibrated thick blood smear for microfilariae was negative and there are no other typical signs of the disease, although the patient has not taken any antifilarial medication. This case highlights the importance of continued vigilance for loiasis, raising awareness of the disease, and promoting early diagnosis and appropriate treatment, especially in vulnerable populations.

Despite two decades of annual Community-Directed Treatment with Ivermectin (CDTI) in the Eséka health district, onchocerciasis transmission persists in frontline villages along the Kéllé River. This study assessed the current epidemiological and entomological status to guide elimination strategies. We conducted cross-sectional clinical and parasitological surveys in two first-line villages (Pouth-Kéllé and Mapan) during June and July 2021. Skin snips were examined for Onchocerca volvulus microfilariae, and clinical manifestations were assessed. Monthly blackfly collections by human landing catches (HLC) were performed at four river sites over one year. Flies were dissected to detect O. volvulus larvae. Microfilarial prevalence was 18.7% (14/75) in Pouth-Kéllé and 15.6% (5/32) in Mapan. Palpable nodules were found in 10% and 6.3% of adults, respectively, reflecting chronic lesions despite recent ivermectin distribution. Reduced visual acuity was frequent (46.7% in Pouth-Kéllé, 47% in Mapan) and was significantly associated with microfilarial positivity in Pouth-Kéllé (p = 0.04). Entomological surveys yielded a total of 9,163 blackflies collected across the four capture sites, of which 6,036 were dissected to detect O. volvulus larvae. Analysis of biting rates showed that collected point I (P1) exhibited the highest annual biting rate (40,500 bites/person/year), with marked seasonality peaking in April. Transmission risk persisted at collected point II (P2 –annual transmission potential: 14.3 infective larvae/person/year) and collected point IV (P4 − 10.0 infective larvae/person/year). Onchocerciasis transmission remains active in the Kéllé River basin despite two decades of ivermectin treatment. These findings support the urgent need for complementary and/or alternative strategies to achieve elimination of onchocerciasis.

Preventive chemotherapy (PC), involving the periodic administration of anthelmintic drugs such as albendazole or mebendazole to at-risk populations, is the main strategy for controlling soil-transmitted helminth (STH) infections in endemic countries. This study assessed the efficacy of a single dose of albendazole against STH infections in the Akonolinga Health District, Centre Region, Cameroon, where STH prevalence remains high despite more than a decade of PC implementation. A community-based screening survey identified 131 individuals infected with at least one of the target species, Ascaris lumbricoides or Trichuris trichiura. All infected participants received a single dose of Albendazole. Three weeks after treatment, stool samples were collected and examined using the Kato–Katz technique to evaluate treatment efficacy. Cure rate (CR), defined as the proportion of participants who became egg-free, and egg reduction rate (ERR), reflecting the decrease in egg counts, were computed. For A. lumbricoides, the CR was 94.9% (95% CI: 87.7 - 98.0) and the ERR was 97.5%, while for T. trichiura, the CR and ERR were 26.0% (95% CI: 17.5 - 36.7) and 29.8%, respectively. Compared with WHO efficacy thresholds, Albendazole showed satisfactory effectiveness against A. lumbricoides but poor efficacy against T. trichiura. Species-specific treatment strategies are urgently needed to improve STH control and support elimination efforts.

Background Bipindi is a historic focus of human African trypanosomiasis (HAT). With the number of cases declining to near-elimination levels, understanding the current entomological risk is crucial to guiding elimination strategies. Methods Two entomological surveys in four historical sentinel villages used pyramidal traps to capture tsetse flies. Dissected midguts were analyzed by polymerase chain reaction (PCR) for trypanosome infection. Blood meal origins were identified using cytochrome B gene heteroduplex analysis. Results Glossina palpalis palpalis was accounted for 99.0% of 708 captured tsetse flies. Apparent density was significantly higher in the dry season (2.11) than in the rainy season (0.89) (P < .0001). Blood meal analysis revealed that these flies fed on pigs (25.0%), humans (16.7%), dogs (12.5%) and goats (8.3%). PCR-based analysis of 371 flies detected Trypanosoma congolense (16.4%), Trypanozoon spp. (8.1%) and Trypanosoma vivax (2.7%). No Trypanosoma brucei gambiense was found, suggesting no transmission risk, despite high vector competence. Conclusions Although no evidence of T. b. gambiense transmission was found in this study, the presence of competent tsetse flies represents a potential danger that could jeopardize current control efforts, underscoring the need for sustained integrated surveillance and vector control to achieve elimination.

INTRODUCTION:Significant progress has been made in onchocerciasis control through mass distribution of ivermectin among affected human populations, fostering optimism for disease elimination. However, despite these considerable advances, the elimination of the disease remains a major challenge in many African foci. This paper describes the current situation of onchocerciasis in Adamaoua Region of Cameroon after 20 consecutive years of ivermectin mass treatment. MATERIALS AND METHODS:The study was conducted between August and September 2020 in Adamaoua Region of Cameroon. Onchocerciasis endemicity was assessed through parasitological and clinical diagnosis. Microfilarodermia and nodule prevalences assessed in 2020 were compared to those of 1998-2002 and 2010-2013 surveys using the Chi-square (X 2) statistic test. RESULTS:A total of 4,814 participants aged between 5 and 108 years, including 50.4% men and 49.6% women were enrolled in the study. The nodule and microfilaria prevalences reported from this sub-sample were 0.87 [0.64 - 1.19] % and 0.77 [0.54 - 1.07] %, respectively. At the community level, the mf prevalences ranged from 0.5% to 4.5%. Globally, the community microfilarial loads (CMFL) were < 0.5 mf/ss. The survey therapeutic coverage rates were between 40% and 78%, lower than those reported (79% - 83%) by the NOCP. The coverage rates in ivermectin treatment in all age groups of the population were below 65%, except for the 40-50 age group where it was ≈70%. CONCLUSION:The results of this study show a drastic decline in onchocerciasis prevalences after 20 consecutive years of CDTI, indicating a significant progress towards stopping O. volvulus transmission in Adamaoua Region. However, additional efforts are needed to increase the population coverage in ivermectin treatment in order to stop the parasite transmission in this region.

BackgroundThe control of onchocerciasis currently relies on yearly distribution of ivermectin to at-risk populations. To tackle onchocerciasis in areas of high transmission (so-called hotspots) and achieve elimination of transmission, several complementary/alternative strategies (biannual ivermectin, doxycycline-based test-and-treat and vector control) were implemented in Massangam Health District (HD) in Cameroon, following World Health Organization (WHO) guidelines. A short-term impact evaluation revealed significant reductions in the endemicity levels in three focal hotspot communities (Makouopsap, Mankakoun, and Njinja-Njingouet). This study aimed to assess the situation of onchocerciasis in the focal hotspot communities five years after the cessation of the short pilot implementation of Alternative Treatment Strategies (ATS).MethodologyA quantitative cross-sectional survey was conducted in December 2023 in three focal hotspot communities of the Massangam Health District. Participants underwent a comprehensive assessment including parasitological examination (skin snipping) to establish Onchocerca volvulus microfilaridermia.Principal findingsThe overall prevalence of O. volvulus infection in the three focal communities was 18.7% (95% confidence interval CI: 14.1-24.3), significantly higher in the Mankakoun (30.8%) and Makouopsap (24.0%) communities compared to the Njinja-Njingouet community (7.0%) (p = 0.001). The intensity of infection was 3.136 (standard deviation, SD: 19.3099) mf/ss, ranging from 5.218 mf/ss (Mankakoun community) to 2.840 mf/ss (Njinja-Njingouet community). Parasitological indicators significantly increased five years after the cessation of ATS in all three focal communities (p = 0.0409).Conclusion/significanceThese findings indicate a rebound in onchocerciasis transmission and underscore the need for coordinated and sustained efforts, implemented at the scale of a transmission zone per WHO recommendations, to achieve elimination goals.

Background:In 2018, the US Food and Drug Administration approved the macrocylic lactone moxidectin (MOX) at 8 mg dosage for onchocerciasis treatment in individuals aged ≥12 years. Severe adverse reactions have occurred after ivermectin (IVM), also a macrocyclic lactone, in individuals with high Loa microfilarial density (MFD). This study compared the safety and efficacy of a 2 mg MOX dose and the standard 150 µg/kg IVM dose in individuals with low L loa MFD. Methods:A double-blind, randomized, ivermectin-controlled trial of a 2 mg moxidectin dose was conducted in Cameroon between May and July 2022. It enrolled 72 adult men with L loa MFD between 5 and 1000 microfilariae/mL. Outcomes were occurrence of adverse events (AEs) and L loa MFD reduction rate during the first month off treatment. Results:No serious or severe AEs occurred among the 36 MOX- or the 36 IVM-treated individuals. Forty-nine AEs occurred in the MOX arm versus 59 AEs in the IVM arm. Grade 2 AE incidence was higher among IVM- than MOX-treated participants (38.5% and 14.3%, respectively, P = .043). Median MFD reduction rates were significantly higher after IVM than MOX at day 3 (70.2% vs 48.5%), day 7 (76.4% vs 50.0%), and day 30 (79.8% vs 48.1%). Conclusions:A single 2 mg MOX dose is as safe as 150 µg/kg IVM in patients with low L loa MFD. Further studies with higher MOX doses and in patients with higher MFD are warranted. Clinical Trials Registration:NCT04049851.

Arthropod microbiota plays an important role in host physiology, and there is growing interest in using vector symbionts to modify vector competence and control parasite transmission. This study aims to characterise the blackfly Simulium damnosum s.l. gut microbiota and to explore possible associations with various bio-ecological determinants of the Onchocerca volvulus establishment and the transmission in blackfly. Adult female blackflies were caught in three Cameroonian health districts belonging to different bioecological zones endemic for onchocerciasis. Flies were dissected and qPCR screened for Onchocerca volvulus infection. The diversity of the blackflies gut microbiota was assessed by high-throughput sequencing of the V3-V4 hypervariable region of the bacterial 16S ribosomal RNA. Subsequent metataxo-genomic, multivariate, and association analysis were used to investigate the variables that influence the microbiota diversity. Transmission index rates ranging from 20.7 to 6.0 % and 6.2to 2.0 % for infection and infectivity rates, respectively, indicate ongoing transmission of onchocerciasis across all surveyed health districts. The identified bacterial taxa were clustered into four phyla, five classes, and 23 genera. The S. damnosum s.l. gut microbiota was dominated by Wolbachia and by Rosenbergiella in Wolbachia-free Simulium. Significant differences were observed in the diversity of S. damnosum s.l. microbiota concerning parity status (P = 0.007), health district of origin (P = 0.001), and the presence of the Onchocerca volvulus. Simulium from the Bafia health district also showed increased bacterial diversity between two consecutive years (P = 0.001). Four bacterial taxa, including Serratia, were associated with the absence of the O. volvulus infection. These results indicate that S. damnosum s.l. from different onchocerciasis foci in Cameroon, exhibit distinguishable gut microbial compositions which are dynamic over time. Some bacterial species are associated with the O. volvulus infection and could be further investigated as biological target/tool for vector modified-based onchocerciasis control.

The effectiveness of the “Slash and Clear” method in reducing blackfly populations in low transmission areas is established, but its impact in high transmission settings with large rivers and dense vectors is yet to be proven. A community-based intervention study was conducted in the Mbam Valley, Centre Cameroon, involving two sites: Bayomen (control) and Biatsota (intervention). In each arm, baseline blackfly densities were collected over one year using the human landing method. The intervention consisted of destroying the trailing vegetation where blackflies breed. Blackfly densities were collected post-intervention to assess the impact of the intervention. Post-intervention data showed a 50.8% reduction in blackfly density in Biatsota (mean number of collected blackflies from 1936 to 953), while a reduction of 26.7% was observed in Bayomen (mean number of collected blackflies from 2418 to 1774). The reduction rate attributable to the intervention was 32.9%. Statistical analysis confirmed that the reduction in blackfly density was significantly greater in the intervention site. This study demonstrates the feasibility and significant impact of the “Slash and Clear” method in high transmission areas. However, further research is required to assess its long-term effects and determine how this strategy can be scaled up and sustained until onchocerciasis elimination is achieved.

Population Medicine considers the following types of articles:• Research Papers -reports of data from original research or secondary dataset analyses.• Review Papers -comprehensive, authoritative, reviews within the journal's scope.These include both systematic reviews and narrative reviews.• Short Reports -brief reports of data from original research.• Policy Case Studies -brief articles on policy development at a regional or national level.• Study Protocols -articles describing a research protocol of a study.• Methodology Papers -papers that present different methodological approaches that can be used to investigate problems in a relevant scientific field and to encourage innovation.• Methodology Papers -papers that present different methodological approaches that can be used to investigate problems in a relevant scientific field and to encourage innovation.

Background Although “Slash and Clear” has proven effective in reducing blackfly densities in low transmission foci, the impact of this strategy in high transmission settings with large rivers and important vector densities remains to be demonstrated. Methods/Principal findings A controlled before-and-after community-based intervention comprising two arms (Bayomen as control site and Biatsota as intervention site) was carried out in the Mbam Valley (Centre Region, Cameroon). In each arm, baseline blackfly densities were collected over one year using the human landing method. The intervention consisted of destroying the trailing vegetation where blackflies breed. Blackfly densities were collected post-intervention to assess the impact of the intervention. Before the intervention, a total of 36,273 and 29,041 blackflies were collected in Bayomen and Biatsota, respectively. After the intervention period, the total blackfly density in the intervention site decreased from 29,041 to 20,011 (31.1% reduction), while an increase of 2·7% was observed in the control site (from 36,273 to 37,248). The Poisson mixed regression model shows that the reduction was significantly greater in the intervention site than in the control site (p<0.0005). Conclusions/Significance This study showed that “Slash and Clear” approach is feasible and has a significant impact on vector densities in a high transmission setting. Further studies are needed to investigate the long-term impact of this vector control approach, and how this promising strategy can be scaled-up and sustained until elimination of onchocerciasis. Author summary River blindness persists in some foci in Cameroon despite more than two decades of ivermectin-based preventive chemotherapy. Mass drug administration (MDA) appears insufficient to interrupt onchocerciasis transmission in these hotspots, and should be complemented by vector control, the most promising alternative strategy to date. In 2018, the effectiveness of a new community-based vector control approach, known as slash and clear, was demonstrated. This strategy involves the removal of trailing vegetation at breeding sites, a primary attachment points for blackfly larvae. In this study, we show that this environment-friendly intervention is feasible and has a significant impact on blackfly densities in high transmission settings. This promising intervention can be combined with regular annual ivermectin-based preventive chemotherapy to accelerate onchocerciasis elimination.

BACKGROUND:Reducing contact between humans and black flies can lead to interruption of onchocerciasis transmission. The Esperanza Window Trap (EWT) has been shown to be an effective tool for reducing black fly densities. Several shape-based improvements to this trapping system have been made to optimise its effectiveness, but optimisation of this trapping system has been based most often on the shape of the trap, collection in areas of high black fly density and the addition of attractants, without considering transmission potentials and parity rates. This study aims to investigate the differences in biting rates and transmission potential between three catch points along a transect to guide the choice of EWT placement.METHODS:Monthly black fly collection was carried out over a 1-year study period using the human landing method at three catch points along a transect from the riverside toward the centre of two first-line villages (Biatsota and Bayomen), in the Mbam valley in Cameroon. All female black flies caught were counted and dissected, and entomological indicators were computed and compared between the catch points and villages.RESULTS:A total of 80,732 black flies were caught, of which 57,517 were dissected; of the latter, 2743 (4.8%) were parous and 44 (1.6%) were infective. Regarding the distance to the river, a vector density gradient was observed, with the highest annual biting rates being recorded at the riverside. The highest annual transmission potentials were also recorded at the riverside (165 vs 255 infective larvae/man/year in Bayomen and Biatsota, respectively). Overall, the highest parity rates were recorded at the riverside in Biatsota (5.1%) where various human activities are frequent and at the centre of Bayomen village (6.3%).CONCLUSION:The results of this study reveal that entomological parameters were the highest at the riverside catch sites and indicate that riverside locations should be prioritised for EWTs or other trapping systems to achieve optimal performance in onchocerciasis control.

Background Onchocerciasis (river blindness) is still endemic in parts of Africa, causing skin, eye, and brain disease. The cornerstone intervention for onchocerciasis control is community-directed treatment with ivermectin (CDTI), but therapeutic coverage remains sub-optimal in several endemic communities. The “Slash and Clear” (S&C) vector control technique has been proposed as an environmentally-friendly alternative tool to supplement CDTI. Methods We conducted repeated cross-sectional entomological studies in Nachtigal, an onchocerciasis-endemic village located beside a fast-flowing segment of the Sanaga River in Cameroon. Blackfly breeding sites were mapped and monthly blackfly biting rates (BR) assessment, initiated at the Nachtigal riverbanks using the human landing-catch approach. Blackfly catching for BR measurements were done for three consecutive days (7:00 to 18:00 daily) every month, by the same two catchers, switching every hour. On March 1st 2023 (a timepoint marking the transition from dry to rainy season), we implemented the S&C intervention at the Nachtigal rapids. Physically-fit village volunteers were trained and supervised in the destruction of the breeding sites using machetes and the removal of potential substrates for blackfly breeding from the river. Post-intervention BR were assessed two weeks after the S&C, and changes in BR were calculated. Results Following S&C, monthly BR went from 28,000 in February 2023 to 13,888 bites per person in March 2023 (50.4% reduction). In contrast, in the absence of S&C, BR were 31,108 in February 2022; rising to 36,053 in March 2022 (15.9% increase) with the returning rains. Therefore, compared to the natural evolution of blackfly abundance and nuisance, the S&C intervention engendered 50.4+15.9=66.3% decrease in the BR at the Nachtigal riverbanks. Conclusion Our study demonstrates the significant impact of a community-based S&C vector control approach on blackfly biting rates. Coupled with good CDTI coverage, reducing the blackfly population would break the onchocerciasis transmission cycle and accelerate its elimination.

Entomological indicators of onchocerciasis transmission and the effect of climatic variables on the vector population dynamics were investigated in two first-line villages after more than two decades of mass drug administration with ivermectin. Female blackflies were collected in two villages (Bayomen and Biatsota) using human landing method for a period of 12 months. Blackflies were dissected and entomological indices were computed. Monthly temperature, precipitation, and humidity were collected and the Spearman correlation rank test was used to assess the relationship between biting rates and climatic variables. The highest biting rates (62,280 bites/human/month in Bayomen and 42,090 bites/human/month in Biatsota) were recorded during the long rainy season (November). The Onchocerca volvulus transmission was greater during the long dry season in both villages, with a peak at the beginning of the long dry season in Biatsota (100 infective larvae/human/month), and at the middle of the long dry season in Bayomen (92 infective larvae/human/month). No correlation was found between biting rates and selected climatic variables in the two villages. This study revealed that onchocerciasis transmission is ongoing in the study area despite almost 25 years of Community-Directed Treatment with Ivermectin. In accordance with WHO recommendations, vector control should be used in combination with mass drug administration to accelerate transmission interruption of onchocerciasis. To be optimal, this vector control should be implemented during the long dry season (November to March) when water volumes are low and transmission potentials are high.

ABSTRACT. The SD Bioline ® IgG4 rapid diagnostic test (RDT) detects IgG4 antibodies induced by the Onchocerca volvulus- specific antigen Ov16. We evaluated the stability of the RDT results over 1 month, at different time points after completion of each assay, using eluted dried blood spots collected in central Cameroon. Agreement coefficients regarding positivity between 30 minutes and 24 hours, 1, 2, 3, and 4 weeks were, 96.4%, 93.4%, 93.3%, 93.2%, and 93.2%, respectively. Between 30 minutes and 24 hours, 3.6% of the 15,444 tests showed inconsistent results with 81.2% of these tests changing from negative to positive, increasing O. volvulus antibody prevalence from 23.9% to 26.2% ( P < 0.0001). This change from negative to positive outcome was confirmed at the subsequent timepoints. Depending on the desired accuracy of prevalence estimates, reading time may have to be redefined more strictly.

Abstract Background The current mainstay for control/elimination of onchocerciasis and soil-transmitted helminthiasis (STH) relies on ivermectin- and mebendazole/albendazole-based preventive chemotherapies. However, children under five years of age have been excluded in both research activities and control programs, because they were believed to have insignificant infection rates. There is therefore a need for up-to-date knowledge on the prevalence and intensity of STH and onchocerciasis infections in this age group. This study aimed at assessing the rates and intensities of onchocerciasis and STH infections in children under five years of age who are excluded from ivermectin- or mebendazole/albendazole-based preventive chemotherapies. Methods A series of cross-sectional surveys was conducted in four Health Districts in the Centre and Littoral Regions of Cameroon between 2018 and 2019. All subjects aged 2 to 4 years, were screened for prevalence (or infection rate) and intensity [number of eggs per gram of stool (epg) or number of microfilariae per skin snip (mf/ss)] of STH and onchocerciasis infections respectively using the Kato-Katz and skin snip methodologies. Chi-square and the non-parametric tests (Mann Whitney and Kruskal Wallis) were used to compare infection rates and intensities of infections between Health Districts and genders, respectively. Results A total of 421 children were enrolled in this study. The overall prevalence of onchocerciasis was 6.6% [95% confidence interval (CI): 4.3‒9.9], ranging from 3.6% (in the Ntui Health District) to 12.2% (in the Bafia Health District). The intensity of infection ranged from 0.5 to 46 microfilariae per skin snip [median: 5; interquartile range (IQR): 2.25‒8.5]. The overall prevalence of STH was 9.6% (95% CI: 6.5‒13.9), with a high infection rate (29.6%) in the Akonolinga Health District. Two STH species (Ascaris lumbricoides and Trichuris trichiura) were found among infected individuals. The median intensities of STH infections were 1,992 epg (IQR: 210‒28,704) and 96 epg (IQR: 48‒168) for A. lumbricoides and T. trichiura, respectively. Conclusions This study reveals that children < 5 years of age are highly infected with STH and onchocerciasis, and could contribute to the spread of these diseases, perpetuating a vicious circle of transmission and hampering elimination efforts. These findings reveal the urgent need to provide (or scale) treatments (likely pediatric formulations) to these preschool-aged children, especially in areas of high transmission, to accelerate efforts to reach WHO 2030 target. Graphical Abstract