Human and Environmental Reservoirs of Intestinal Parasites in the City of Yaoundé, Cameroon: An Update in the Context of COVID-19 Pandemic

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.

Epidemiological Importance of the Anopheles Nili Group of Malaria Vectors in Equatorial Villages of Cameroon; Central Africa

From March 1999 to March 2007; entomological surveys were conducted in eight riverside locations of the equatorial domain in Cameroon; to assess the contribution of Anopheles nili group to malaria transmission. Results showed that the anthropophilic Anopheles nili; Anopheles carnevalei and Anopheles ovengensis were involved in 5-68of the Plasmodium falciparum entomological inoculation rates (EIRs) in all the study sites. Alongside; vectors such as Anopheles Gambiae; Anopheles moucheti; Anopheles funestus; Anopheles marshallii and Anopheles hancocki also took a substantial part to these transmission rates in sympatric conditions. Anopheles nili s.s. was the major vector in villages situated near the Sanaga river; with more than 100 infective bites/person/year. Its true Plasmodium falciparum infections rates ranged from 1.4to 6.1. Anopheles carnevalei and Anopheles ovengensis were mainly distributed in the equatorial cross-bordering areas; where they contributed for less than 30of the Plasmodium falciparum EIRs in villages located along the Nten river and Congo river networks. These findings confirm Anopheles nili s.s. as a major malaria vector mosquito; and also provided more data regarding the epidemiological role of Anopheles carnevalei and Anopheles ovengensis througout the central African region

Field Evaluation of Three Commercial Repellents Formulations against Afrotropical Vectors Mosquitoes in Camerooun

Three synthetic commercial insert repellents; Buzz-Off TM (30DEET); Cinq-sur-CinqTM (25IR3535 + essential oils) and prebutix TM(25IR3535) were tested in field conditions for their efficacy and persistence against mosquitoes in the forest area of Cameroon. During 48-days; 7; 569 mosquitoes belonging to four genera were collected: Mansonia spp (67.3); Anopheles spp (27.4); Aedes spp(3.8); and Culex spp (1.5). At the end of the 8-hours exposure period; the DEET-based repellent; Buzz Off TM produced the highest protection against Aedes spp; Culex spp and Mansonia spp. For Anophelines; results were more variable : PrebutixTM showed better protection against An. mouchetti; Cinq-sur-CinqTM was more efficacious against An. Funestus and An.ziemani; whereas Buzz-OffTM appeared more effective against An. Gambiae s.s. and An. nili. Efficacy and persistence parameters were estimated only for An. moucheti and Mansonia spp. The effective dosages (ED50 and ED95) as well as the effective half-life obtained with the DEET-based repellent were highly variable among replicates in the case of An. moucheti. For mansonia spp; the estimated EDO value for the DEET -based repellent was = 0.06mg/cm2. For the two IR3535-based repellents; the ED50 values varied from 0.06 to 0.10 mg/cm2; and 0.15 to 0.20 mg/cm2 for An. moucheti and Mansonia spp; respectively. Globally; the ED95 values values of the three repellents were around 1mg/cm2 except that of Cinq-sur-CinqTM which was ? 0.3mg/cm2 in the case of An. moucheti. The estimated effective half-lifes of the three repellents were approximately between 3 and 5h. Our results highlight the heterogeneity in the response of different mosquito species when exposed to the tested insect repellents; showing the relevance of evaluating efficacy and persistence profiles of different formulations in specific environmental contexts