Background Culex species are widespread across Cameroon and responsible for high burden of nuisance in most urban settings. However, despite their high nuisance, they remain less studied compared to anophelines. The present study aimed to assess Culex species distribution, susceptibility to insecticide, bionomics and role in Lymphatic Filariasis (LF) transmission in the city of Yaoundé. Methods Mosquito collections were conducted from March to December 2017 using Centre for Disease Control light traps (CDC-LT), human landing catches (HLC) and larval collections. Mosquitoes were identified using morphological identification keys. Mosquitoes from the Culex pipiens complex were further identified using Polymerase Chain Reaction (PCR) to assess the presence of sibling species. Bioassays were conducted with 2–5 day-old unfed females to assess mosquito susceptibility to DDT, permethrin, deltamethrin and bendiocarb following WHO guidelines. Dead, control and surviving mosquitoes from bioassays were screened by PCR to detect the presence of knockdown resistance ( kdr ) alleles. Pools of mosquitoes were examined by PCR to detect the presence of Wuchereria bancrofti . Results A total of 197,956 mosquitoes belonging to thirteen species were collected. The density of mosquito collected varied according to the collection methods, districts and seasons. Culex quinquefasciatus emerged as the most abundant and the only species of the Culex pipiens complex in Yaoundé. Culex species were found breeding in different types of breeding sites including polluted and unpolluted sites. All Culex species including Cx antennatus , Cx duttoni , Cx perfuscus and Cx tigripes were found to be highly resistant to permethrin, deltamethrin and DDT. Culex quinquefasciatus was also found to be resistant to bendiocarb. A high frequency of the West Africa kdr allele was recorded in resistant Cx . quinquefasciatus . Out of the 247 pooled samples of 25 Culex spp. examined for the presence of Wuchereria bancrofti , none was found infected. Conclusion The study confirms the high adaptation of Culex species particularly Culex quinquefasciatus to the urban environment and no implication of this species in the transmission of LF in Yaoundé Cameroon. Culex species predominance in urban settings highlight potential transmission risk of West Nile and rift valley fever in Yaoundé.

Background Malaria prevention in Cameroon mainly relies on the use of ITNs. Although several free distribution campaigns of treated nets have been conducted across the country, bed net usage remains very low. A household survey was conducted to assess knowledge of the population and practices affecting treated net usage in the city of Yaoundé. Methods A community-based descriptive cross-sectional survey was conducted in January 2017 in 32 districts of the city of Yaoundé. Parents (household head, spouse or an elder representative) who consented to the study, were interviewed using a structured pre-tested questionnaire. Interviews were conducted in French or English. A questionnaire consisting of 22 questions was administered to know (i) people’s knowledge and attitude on preventive measures; and, (ii) attitudes concerning the treatment of malaria and estimated amount spent for malaria prevention and treatment. Results A total of 1643 household heads were interviewed. Over 94% of people interviewed associated malaria transmission to mosquito bites. The main methods used against mosquito bites were: treated bed nets (94%; n = 1526) and insecticide spray or coils (32.2%; n = 523). The majority of people interviewed reported using bed nets mainly to prevent from mosquito bites (84.4%, n = 1257), rather than for malaria prevention (47.3%). Knowledge and attitude analysis revealed that people with university or secondary level of education have better knowledge of malaria, prevention and treatment measures compared to those with the primary level (OR = 7.03; P < 0.001). Also, wealthy households were more aware of good practices concerning malaria prevention and treatment compared to poor ones. In the majority of districts of Yaoundé, over 50% of people interviewed per district, had good knowledge of malaria and prevention measures but less than 50% applied good practices concerning malaria treatment and prevention. The amount spent annually by a household for vector control was CFAF 11,589 ± 1133 (US$21.87 ± 2.14) and CFAF 66,403 ± 4012 (US$125.29 ± 7.57) for malaria treatment. Conclusion The study indicated that, despite good knowledge of malaria and prevention measures, few people apply good practices. More sensitization needs to be done to improve adherence to good practices concerning malaria prevention and treatment. Electronic supplementary material The online version of this article (10.1186/s12936-019-2799-6) contains supplementary material, which is available to authorized users.

African pangolins are exceptionally difficult to monitor in the wild, which means that assessing threats and impacts to these species also remains a challenge. Local ecological knowledge (LEK) surveys have been recommended as an important tool to collect data for small elusive species. We carried out community-based interviews in 20 villages surrounding Mpem et Djim and Deng-Deng National Parks to gather information on local ecological and traditional medicine knowledge, perceived population status, and the level of conservation awareness amongst local people concerning giant pangolin (Smutsia gigantea), white-bellied pangolin (Phataginus tricuspis), and black-bellied pangolin (Phataginus tetradactyla). The arboreal black-bellied pangolin was least known by local people, and along with the giant pangolin was the least recently observed species. The white-bellied pangolin was reported to be the most recently observed species by most people. Local people reported seeing giant pangolins most around forest and savannah burrows and white-bellied pangolins in forests, commonly crossing dead fallen trees. Limited traditional or cultural uses of pangolins were reported, and most respondents were aware of threats to pangolins. Respondents showed great interest in pangolin conservation, suggesting various strategies for conservation activities, such as trade controls and provisioning of alternative sources of food. We show that working with local communities can provide useful information for pangolin conservation and management efforts within protected areas.

Background In Cameroon, since the first epidemiological week held in 2015, snakebites have been registered among Potential Epidemic Diseases (PED). In the Centre Region, the most densely populated of the country, weekly reports of snakebites are generated at health districts level for monthly data updates. Methods To contribute to the better management of snakebite cases, an observational study was conducted to assess the snakebite reporting rate in the Centre Region of Cameroon. The results of this retro-prospective survey were confronted to those of the weekly epidemiological surveillance system, recorded in the PED regional data base. Results The incidence of bites was relatively high (36.6 bites per 100,000 inhabitants), as well as the general attack rate (about 49 envenomations per 100 victims). The lethality recorded was 2.5% and the mortality was about 1 death per 100,000 inhabitants a year. The sex ratio was largely female biased (61.6%). The bites occurred mostly during the rainy season (73.0%). Bitten victims were mainly farmers (47.4%), and agriculture was the main risk factor. The comparative analysis of the data suggested a high non-reporting rate of snakebite cases (67.8%). Conclusion Snakebite is an endemic condition in the Centre Region of Cameroon. Because of the high rate of non-reporting of cases, the collection of information from the registers of the health facilities only appears not enough to assess the real importance of envenomation in this Region.

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Background: Pyrethroid resistance is rapidly expanding in An. gambiae s.l. populations across Sub-Saharan Africa. Yet there is still not enough information on the fitness cost of insecticide resistance . In the present study, the fitness cost of insecticide resistance on Anopheles coluzzii population from the city of Yaoundé was investigated.  Methods: A resistant An. coluzzii colony was established from field collected mosquitoes resistant to both DDT and pyrethroid and selected for 12 generations with deltamethrin 0.05%. The Ngousso laboratory susceptible strain was used as control. A total of 100 females of each strain were blood fed and allowed for individual eggs laying, and then different life traits parameters such as fecundity, fertility, larval development time, emergence rate and longevity were measured. The TaqMan assay was used to screen for the presence of the L1014F and L1014S kdr mutations. Results:  Field collected mosquitoes from the F0 generation had a mortality rate of 2.05% for DDT, 34.16% for permethrin and 50.23% for deltamethrin. The mortality rate of the F12 generation was 30.48% for deltamethrin, 1.25% for permethrin  and 0% for DDT. The number of eggs laid per female was lower in the resistant colony compared to the susceptible (p <0.0001). Insecticide resistant larvae were found with a significantly long larval development time (10.61±0.33 days) compare to susceptible (7.57±0.35 days). The number of emerging females was significantly high in the susceptible group compared to the resistant . The adults lifespan was also significantly high for susceptible (21.73±1.19 days) compared to resistant (14.63±0.68 days). Only the L1014F-kdr allele was detected in resistant population.. Conclusion: The study suggests that pyrethroid resistance is likely associated with a high fitness cost on An.coluzzii populations. The addition of new tools targeting specifically larval stages could improve malaria vectors control and insecticide resistance management.

BackgroundAgriculture is a major contributor to the Gross Domestic Product (GDP) of Cameroon, The South West region of Cameroon is known for its potential in the production of major agricultural commodities, but farmers’ yields from various speculations are low, dwindling over time due to some major constraints. Maize production is hampered by adverse socio-economic factors, several pests and diseases as well as high rainfall with low solar radiation. Lepidopterous maize stem borers are a major threat to increase maize production. Therefore we hypothesized that the farmers of the South West region: (1) also perceived stem borers as an important pest of maize; (2) they have their own indigenous methods of control; (3) they use chemical pesticides because they have no alternative, but would prefer plant materials if these were standardized.MethodsA semi-structured questionnaire survey was administered in four villages: Maumu, Lower Bokova, Ekona and Bonduma. A total of 151 (male and female) farmers were randomly interviewed to document farmers’ perception on stem borers, and their use of indigenous knowledge to manage key pests of maize.ResultsStem borers were present throughout the maize growing areas in the Fako division and ranked as one of the most important pests of the crop. Most farmers (82.1 %) perceived that stem borers caused significant damage on maize and were responsible for yield reductions in the crop. The increased impact of these pests was due to improper/untimely use of expensive conventional insecticides given the lack of a cheaper alternative method of control. About 50 % of respondent admitted not having any indigenous knowledge of stem borer control, while only 20 % had tried plant products. The most relevant indigenous stem borer control was the use of wood ash. Most (90 %) of the respondent would prefer plant-based insecticides in future because they are safer, cheaper and readily available.ConclusionsFarmers’ knowledge would contribute in understanding the activities of stem borers and use of plant insecticides. Research is therefore needed to standardize the methods of using plant-based products and also identify the active ingredients of these plants to ensure their effectiveness against maize stem borers and other pests.

The cabbage aphid, Brevicoryne brassicae, is a pest of many plants of the Brassicaceae family including cabbage, Brassica oleracea Linnaeus, 1753. We investigated the effect of temperature on the biological parameters of B. brassicae using different temperature‐based models incorporated in the Insect Life Cycle Modelling (ILCYM) software. Nymphs of first stage were individually placed in the incubators successively set at 10°C, 15°C, 20°C, 25°C, 30°C, and 35°C; 75 ± 5% RH; and L12: D12‐hr photoperiods. We found that first nymph reached the adult stage after 18.45 ± 0.04 days (10°C), 10.37 ± 0.26 days (15°C), 6.42 ± 0.07 days (20°C), 5.076 ± 0.09 days (25°C), and 5.05 ± 0.10 days (30°C), and failed at 35°C. The lower lethal temperatures for B. brassicae were 1.64°C, 1.57°C, 1.56°C, and 1.62°C with a thermal constant for development of 0.88, 0.87, and 0.08, 0.79 degree/day for nymphs I, II, III, and IV, respectively. The temperatures 10, 30, and 35°C were more lethal than 15, 20, and 25°C. Longevity was highest at 10°C (35.07 ± 1.38 days). Fertility was nil at 30°C and highest at 20°C (46.36 ± 1.73 nymphs/female). The stochastic simulation of the models obtained from the precedent biological parameters revealed that the life table parameters of B. brassicae were affected by the temperature. The net reproduction rate was highest at 20°C and lowest at 30°C. The average generation time decreased from 36.85 ± 1.5 days (15°C) to 6.86 ± 0.1 days (30°C); the intrinsic rate of increase and the finite rate of increase were highest at 25°C. In general, the life cycle data and mathematical functions obtained in this study clearly illustrate the effect of temperature on the biology of B. brassicae. This knowledge will contribute to predicting the changes that may occur in a population of B. Brassiace in response to temperature variation.