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Aims: A survey on Human African Trypanosomiasis (HAT) is essential for prevention and preparedness for epidemics. The objective of this study is to assess the circulation of human trypanosomes and their vectors across quiescent HAT foci of the Littoral Region of Cameroon. Methodology: A descriptive study on the presence of Trypanosoma brucei gambiense and its potential vectors was carried out in Youpwe, Yabassi, Sodiko, Manoka island and Cape-Cameroon Island from February to April 2022.Tsetse flies collected from the five selected locations using pyramidal traps, were first classified by species according to their morphology, then by sub-species with Polymerase Chain Reaction Diagnostic (PCR-Diag). Trypanosoma species and sub-species were subsequently identified and genotyped using a Nested PCR. Results: Glossina palpalis palpalis was the unique tsetse subspecies recorded across the five locations. The tsetse infection rate by Trypanosoma ssp. varied between 5.35% in Cape-island and 35.71% in Manoka island. Three Trypanosoma species were detected: T. brucei s.l. 32/500 (6.4%), T. congolense 15/500 (3.0%), and T. vivax 8/500 (1.6%). The sub-species T. b. gambiense responsible for HAT was detected in tsetse flies from Manoka (2/150: 1.33%), whereas T. congolense consisted of T. congolense “forest” and T. congolense “savannah” types. Conclusion: The presence of T. b. gambiense and T. congolense sub-species in Manoka and nearby suggests residual circulation of human and animal trypanosomes in quiescent HAT foci of the littoral region of Cameroon.

Aims: Intestinal parasitic infections are persistent in Africa, and we questioned here whether prevention measures imposed by the occurrence of the COVID-19 pandemic in 2020 could alleviate this threat in lowlands of the city of Yaoundé, Cameroon. Study Design: We monitored the trend of intestinal parasites in human and environmental samples from the seven subdivisions of the city of Yaounde, before (November-December 2019) and during (July-August 2020, November-December 2020) the COVID-19 pandemic. Methodology: Parasitological analysis were performed to check for the presence of helminths and protozoans in stools from inhabitants as well as in water, soil and fresh vegetables, using standard Kato Katz and Formol Ether methods.The minimum effective sample size considered for the estimation of parasite richness, parasite infection and contamination indexeswas 30 for human and 30 for environmental samples (i.e. soils, water and vegetables) per location. Results: Of the 19 parasite species identified in human and the environments, twelve were helminths and seven protozoans. The overall parasite species richness reached 16 in 2019 (12 helminths and 4 protozoans) and 19 in 2020 (12 helminths and 7 protozoans), with about 62.5-68.4% of species shared by human and environments. The parasite frequencies in human (21.03%) and water/soils (32.3%) in 2019 did not differ statistically with those of 2020 (14.6-20.3% and 10.8-35.4%, respectively). The contamination rate of vegetables (i.e. carrots, lettuce, basil, celery, etc.) has increased from 2019 (6.1-9.1%) to 2020 (9.1-24.2%), and was frequently due to roundworms, hookworms, Entamoeba and Cryptosporidium cysts. The findings suggest persistent risk associated with intestinal parasite irrespective to measures imposed by COVID-19 in study locations. Conclusion: The current control approaches may therefore integrateecological epidemiology of the intestinal parasite infections as complementary strategy in African cities.

Introduction: Human African Trypanosomiasis (HAT) is a neglected tropical disease still endemic in the Republic of Congo. Despite continuous detection of HAT cases in the country, there is still not enough data on trypanosome infections in tsetse flies, trypanosome species and tsetse flies species distribution in endemic foci. The present study is intended to fill this gap and improve understanding on trypanosome circulation in three active foci in the centre and south of Congo.Methods: Pyramid traps were set in various places in villages to collect tsetse flies both during rainy and dry season. Once collected, tsetse flies were identified using morphological keys. DNA extracted from flies was processed by PCR for species identification and for detection of trypanosome. A second PCR was ran for different trypanosome species identification.Results: A total of 1291 tsetse flies were collected. The average apparent density of fly per day was 0.043 in Mpouya, 0.73 in Ngabé and 2.79 in Loudima. Glossina fuscipes quazensis was the predominant tsetse fly found in Ngabé and Mpouya, while Glossina palpalis palpalis was the only tsetse fly found in Loudima. A total of 224 (17.7%) flies were detected infected by trypanosomes; 100 (7.91%) by Trypanosoma congolense savannah, 22 (1.74%) by Trypanosoma congolense forest, 15 (1.19%) by Trypanosoma vivax, 83 (6.56%) by Trypanosoma brucei (s.l.) and 2 (0.16%) undetermined species. A total of 57 co-infections between T. brucei (s.l.) and T. congolense savannah or T. brucei (s.l.) and T. congolense forest were found only in G. p. palpalis. Loudima recorded the highest number of infected tsetse flies.Conclusion: The study provided updated information on the dynamics of tsetse fly populations as well as on the transmission of trypanosome species in the different active HAT foci in Congo. The data suggest high transmission of animal trypanosomes and possibly human trypanosomes in these foci. The study stress the need for active surveillance in these endemic foci.

Understanding how multiple insecticide resistance mechanisms occur in malaria vectors is essential for efficient vector control. This study aimed at assessing the evolution of metabolic mechanisms and

Intestinal parasite infections are still prevalent in developing countries and in Cameroon where over 90% of the population is at high risk. To assess the distribution of intestinal parasitic infections and risk factors of the city of Yaoundé, both household and parasitological surveys were conducted from October to December 2019 among inhabitants of lowlands aged from 15 years and over. Stools samples were collected and screened for intestinal parasites presence using Kato Katz and Formol-Ether methods. Sociodemographic status, prevention measures against intestinal parasitic diseases and practices with increase exposition to risky environments were then recorded. A total of 229 participants (142 females: 62.0%; 87 males: 38.0%) were enrolled for the study, and 24.02% (55/229) were found infected by helminthes (ten species) and/or protozoans (one species). Participant infection rates and risk varied by parasite species and socio-demographic factors. Global risk analysis showed that age (OR ranges: 3.78-15.96), anti-parasitic drug consumption (OR: 2.53), eating behavior,,hygiene (OR: 22.4), occupation (OR ranges: 1.92-3.53) and type of toilets (OR: 3.4) were strongly associated with risk of infection by intestinal parasites. The risk increased in 15-30 years age group for A. lumbricoïdes, T. trichiura and Schistosoma mansoni, unpredictably in those washing their hands before meals for A. lumbricoïdes and H. nana, in respondents using antiparasitic drugs as auto-medication for H. nana and in those using traditional toilets for A. lumbricoïdes. However, other variables with high OR values (> 5.0) might be potential risk factor for the occurrence of specific parasite infections. The study suggests the need for household sensitization and community actions including integrated environmental management as complement strategy to reduce intestinal parasite transmission in the city of Yaoundé.

Sub-Saharan Africa is registering one of the highest urban population growth across the world. It is estimated that over 75% of the population in this region will be living in urban settings by 2050. However, it is not known how this rapid urbanization will affect vector populations and disease transmission. The present study summarizes findings from studies conducted in urban settings between the 1970s and 2020 to assess the effects of urbanization on the entomological inoculation rate pattern and anopheline species distribution. Different online databases such as PubMed, ResearchGate, Google Scholar, Google were screened. A total of 90 publications were selected out of 1527. Besides, over 200 additional publications were consulted to collate information on anopheline breeding habitats and species distribution in urban settings. The study confirms high malaria transmission in rural compared to urban settings. The study also suggests that there had been an increase in malaria transmission in most cities after 2003, which could also be associated with an increase in sampling, resources and reporting. Species of the Anopheles gambiae complex were the predominant vectors in most urban settings. Anopheline larvae were reported to have adapted to different aquatic habitats. The study provides updated information on the distribution of the vector population and the dynamic of malaria transmission in urban settings. The study also highlights the need for implementing integrated control strategies in urban settings. Supplementary Information The online version contains supplementary material available at 10.1186/s12936-021-03891-z.

Background: In Cameroon, the practice of market gardening exposes both the farmers and consumers to a certain number of health-related hazards. Environmental health risks associated to this activity showed that it was responsible for the increased of transmission risk of the human and animal intestinal worms. Methods: The epidemiology of soil borne diseases associated with urban agriculture was furthermore considered in three market garden sites of the city of Yaounde (Tsinga, Nkolondom, Nkolbisson). From October to December 2016, water and soils from rivers, wells and furrows were analysed for physicochemical characteristics and parasite identification using Kato-Katz and Formol-Ether methods. Results: Means of water parameters and parasite composition varied per locations and environments in the 82 samples analyzed. Ranges of mean temperature, pH, electrical conductivity, turbidity and color of water samples were 25.2-25.5°C (), 6.53-7.01 UC, 308-502 µS.cm-1, 637-1,300 FTU and 2,451-6,422 Co-Pt, respectively. Soil parasites consisted of 3 protozoans (Entamoeba histolytica, Sarcocystis sp. and Giardia intestinalis) and 11 helminths (Fasciola hepatica, Diphyllibotrium latum, Ascaris lumbricoides, Trichuirus trichiura, Ancylostoma sp., Trichostrongylus sp., Schistosoma mansoni, Schistosoma sp., Paragonimus westermanii, Strongyloides stercoralis and Hymenolepis nana). Conclusion: The presence of viable helminths suggests that harmful soil pathogens such as protozoans and helminths can spread through market gardening. This reminds on the need to find better ways to alleviate the control of intestinal parasitic infections which, nevertheless, are classified as neglected tropical diseases.

Summary Background Scale-up of insecticide-based interventions has averted more than 500 million malaria cases since 2000. Increasing insecticide resistance could herald a rebound in disease and mortality. We aimed to investigate whether insecticide resistance was associated with loss of effectiveness of long-lasting insecticidal nets and increased malaria disease burden. Methods This WHO-coordinated, prospective, observational cohort study was done at 279 clusters (villages or groups of villages in which phenotypic resistance was measurable) in Benin, Cameroon, India, Kenya, and Sudan. Pyrethroid long-lasting insecticidal nets were the principal form of malaria vector control in all study areas; in Sudan this approach was supplemented by indoor residual spraying. Cohorts of children from randomly selected households in each cluster were recruited and followed up by community health workers to measure incidence of clinical malaria and prevalence of infection. Mosquitoes were assessed for susceptibility to pyrethroids using the standard WHO bioassay test. Country-specific results were combined using meta-analysis. Findings Between June 2, 2012, and Nov 4, 2016, 40 000 children were enrolled and assessed for clinical incidence during 1·4 million follow-up visits. 80 000 mosquitoes were assessed for insecticide resistance. Long-lasting insecticidal net users had lower infection prevalence (adjusted odds ratio [OR] 0·63, 95% CI 0·51–0·78) and disease incidence (adjusted rate ratio [RR] 0·62, 0·41–0·94) than did non-users across a range of resistance levels. We found no evidence of an association between insecticide resistance and infection prevalence (adjusted OR 0·86, 0·70–1·06) or incidence (adjusted RR 0·89, 0·72–1·10). Users of nets, although significantly better protected than non-users, were nevertheless subject to high malaria infection risk (ranging from an average incidence in net users of 0·023, [95% CI 0·016–0·033] per person-year in India, to 0·80 [0·65–0·97] per person year in Kenya; and an average infection prevalence in net users of 0·8% [0·5–1·3] in India to an average infection prevalence of 50·8% [43·4–58·2] in Benin). Interpretation Irrespective of resistance, populations in malaria endemic areas should continue to use long-lasting insecticidal nets to reduce their risk of infection. As nets provide only partial protection, the development of additional vector control tools should be prioritised to reduce the unacceptably high malaria burden. Funding Bill & Melinda Gates Foundation, UK Medical Research Council, and UK Department for International Development.

Background Malaria is still a global health problem and vector control is the cornerstone of disease control strategies using indoor residual insecticide spraying (IRS) and insecticide-treated nets. The situation is becoming acute with widespread resistance to the limited arsenal of available insecticide classes. Therefore, new and innovative tools to reduce Plasmodium transmission are in need and this situation raised considerable interest in using sterile insect technique (SIT) against human pest insects, particularly Anopheles malaria vectors. When considering a mosquito release programme, one of the first issues to be addressed is how to eliminate/separate the hematophagous vector females. In this paper, we report the development and evaluation of an Anopheles arabiensis temperature-sensitive lethal (tsl) strain towards its potential use for the development of a genetic sexing strain (GSS). Anopheles arabiensis male mosquitoes originated from North Cameroon were treated with 0.05% ethyl methanesulfonate (EMS). The mutagen was added to 10% sucrose solution and mosquitoes fed ad-libitum for 24h and 48h on a cotton wool soaked with sucrose-mutagen solution placed at the top of the cup. Treated males were then allowed to mate with wild virgin females and their progenies were screened for heat sensitivity from F3 to F8, until the isolation and establishment of a tsl strain which was further characterized by assessing its productivity (fecundity and fertility), larval development, adult longevity as well as nature and inheritance pattern of the tsl. Results Observations showed that the number of eggs laid and their hatch rate were similar between females that mated with mutagenized males and those from the control suggesting that mutagenesis didn't affect An. arabiensis male fecundity and fertility. At F3, fourteen isofemale families out of 88 tested, which showed mortalities ranged between 50 and 80 %, were selected as lines potentially containing a tsl mutation. From F4 to F8, a tsl strain was isolated and established by screening L1 larvae at 41°C for 3 hours. This strain showed similar life history traits compared to the wild type strain in terms of fertility, larval development time and adult's emergence. Crossing experiments to further assess the nature and inheritance pattern of the tsl phenotype showed that it is due to a recessive allele located on an autosome. Conclusion The successful establishment of the An. arabiensis tsl strain is a valuable tool towards the development of a GSS for SIT applications against this species. This will be done by induction of a Y-autosome translocation to link the wild-type allele to the Y chromosome in such manner that males are wild-type (temperature resistant) and females are mutant (temperature sensitive).

Background Pyrethroid insecticides are widely used for insect pest control in Cameroon. In certain insect species, particularly the malaria vector Anopheles gambiae, resistance to this class of insecticides is a source of great concern and needs to be monitored in order to sustain the efficacy of vector control operations in the fields. This study highlights trends in DDT and pyrethroid resistance in wild An. gambiae populations from South Cameroon. Methods Mosquitoes were collected between 2001 and 2007 in four sites in South Cameroon, where insecticides are used for agricultural or personal protection purposes. Insecticide use was documented in each site by interviewing residents. Batches of 2-4 days old adult female mosquitoes reared from larval collections were tested for susceptibility to DDT, permethrin and deltamethrin using standard WHO procedures. Control, dead and survivors mosquitoes from bioassays were identified by PCR-RFLP and characterized for the kdr mutations using either the AS-PCR or the HOLA method. Results Four chemical insecticide groups were cited in the study sites: organochlorines, organophosphates, carbamates and pyrethroids. These chemicals were used for personal, crop or wood protection. In the four An. gambiae populations tested, significant variation in resistance levels, molecular forms composition and kdr frequencies were recorded in the time span of the study. Increases in DDT and pyrethroid resistance, as observed in most areas, were generally associated with an increase in the relative frequency of the S molecular form carrying the kdr mutations at higher frequencies. In Mangoum, however, where only the S form was present, a significant increase in the frequency of kdr alleles between 2003 to 2007 diverged with a decrease of the level of resistance to DDT and pyrethroids. Analyses of the kdr frequencies in dead and surviving mosquitoes showed partial correlation between the kdr genotypes and resistance phenotypes, suggesting that the kdr mechanism may act with certain co-factors to be identified. Conclusion These results demonstrate the ongoing spread of kdr alleles in An. gambiae in Central Africa. The rapid evolution of insecticide resistance in this highly dynamic and genetically polymorphic species remains a challenge for its control.

Two standard methods are available to infect mosquitoes with malaria parasites : direct feeding through the skin of the gametocyte carrier, and membrane feeding. #Anopheles arabiensis$ collected at larval stages and reared in an insectary were fed in parallel by feeding on #Plasmodium falciparum$ gametocyte carriers and by membrane feeding on venous blood of the same gametocyte carriers. Infection of mosquitoes was assessed at Day 7 post bloodmeal by oocyst count of the mosquito midguts. The following parameters were not significantly different between the two methods : the percentage of gametocyte carriers infective for at least one mosquito (52.4% through the skin versus 57.1% through the membrane), the mean infection rate of mosquitoes (10.0% versus 11.3%), the geometric mean oocyst number per mosquito (2.51 versus 3.83). In conclusion, infection of mosquitoes by membrane feeding was similar to infection by direct feeding. Most of the volunteers preferred venipuncture to mosquito bites. (Résumé d'auteur)

Multilocus enzyme analysis of the genetic variability and population structure was conducted among three malaria vector species of the Anopheles nili group in Cameroon: An. nili, An. carnevalei, and the recently described An. ovengensis. We detected species-specific alleles and large differences in shared allele frequencies at six of nine loci (e.g., PGM, GOT1, IDH1, IDH2, PGI, and -GPD). This non-random distribution of alleles leads to high and significant values of differentiation indexes (0.569 < Fst < 0.874, P