Journal Article

Epidemiological and entomological studies of malaria transmission in Tibati, Adamawa region of Cameroon 6 years following the introduction of long-lasting insecticide nets

Maffo Ngou, Christelle, Ayong, Lawrence, Toto, Jean-Claude, Morlais, Isabelle, Nsango, Sandrine Eveline, Feufack-Donfack, Lionel Brice, Bouopda Tuedom, Aline Gaelle, Eboumbou Moukoko, Carole Else, Sarah-Matio, Elangwe Milo, Sandeu, Maurice Marcel, Abate, Luc Marcel, Ngano Bayibéki, Albert, Awono-Ambene, Parfait

2021

Overview

Background Malaria remains a serious public health problem in Cameroon. Implementation of control interventions requires prior knowledge of the local epidemiological situation. Here we report the results of epidemiological and entomological surveys carried out in Tibati, Adamawa Region, Cameroon, an area where malaria transmission is seasonal, 6 years after the introduction of long-lasting insecticidal bed nets. Methods Cross-sectional studies were carried out in July 2015 and 2017 in Tibati. Thick blood smears and dried blood spots were collected from asymptomatic and symptomatic individuals in the community and at health centers, respectively, and used for the molecular diagnosis of Plasmodium species. Adult mosquitoes were collected by indoor residual spraying and identified morphologically and molecularly. The infection status of Plasmodium spp. was determined by quantitative PCR, and positivity of PCR-positive samples was confirmed by Sanger sequencing. Results Overall malaria prevalence in our study population was 55.0% (752/1367) and Plasmodium falciparum was the most prevalent parasite species (94.3%), followed by P. malariae (17.7%) and P. ovale (0.8%); 92 (12.7%) infections were mixed infections. Infection parameters varied according to clinical status (symptomatic/asymptomatic) and age of the sampled population and the collection sites. Infection prevalence was higher in asymptomatic carriers (60.8%), but asexual and sexual parasite densities were lower. Prevalence and intensity of infection decreased with age in both the symptomatic and asymptomatic groups. Heterogeneity in infections was observed at the neighborhood level, revealing hotspots of transmission. Among the 592 Anopheles mosquitoes collected, 212 (35.8%) were An. gambiae , 172 (29.1%) were An. coluzzii and 208 (35.1%) were An. funestus ( s.s. ). A total of 26 (4.39%) mosquito specimens were infected by Plasmodium sp. and the three Anopheles mosquitoes transmitted Plasmodium at equal efficiency. Surprisingly, we found an An. coluzzii specimen infected by Plasmodium vivax , which confirms circulation of this species in Cameroon. The positivity of all 26 PCR-positive Plasmodium -infected mosquitoes was successively confirmed by sequencing analysis. Conclusion Our study presents the baseline malaria parasite burden in Tibati, Adamawa Region, Cameroon. Our results highlight the high malaria endemicity in the area, and hotspots of disease transmission are identified. Parasitological indices suggest low bednet usage and that implementation of control interventions in the area is needed to reduce malaria burden. We also report for the first time a mosquito vector with naturally acquired P. vivax infection in Cameroon. Graphical Abstract

• Publisher: BioMed Central,BioMed Central Ltd,Springer Nature B.V,BMC
• Subject: Adolescent / Adult / adults / Aged / Animals / Anopheles / Anopheles - classification / Anopheles - drug effects / Anopheles - parasitology / Anopheles - physiology / Anopheles coluzzii / Aquatic insects / Asymptomatic / bed nets / Biomedical and Life Sciences / Biomedicine / Blood / Cameroon / Cameroon - epidemiology / Child / Child, Preschool / Control / Cross-Sectional Studies / Culicidae / Disease control / Disease hot spots / Disease transmission / DNA / Endemism / Entomology / Epidemiology / Female / Heterogeneity / Hot spots / Human diseases / Human health and pathology / Humans / Identification / indigenous species / Infant / Infant, Newborn / Infections / Infectious Diseases / Insecticide-Treated Bednets - statistics & numerical data / Insecticides / Insecticides - pharmacology / Life Sciences / Malaria / Malaria - epidemiology / Malaria - parasitology / Malaria - transmission / Male / Microbiology and Parasitology / Middle Aged / Mosquito Control / mosquito vectors / Mosquito Vectors - classification / Mosquito Vectors - drug effects / Mosquito Vectors - parasitology / Mosquito Vectors - physiology / Mosquitoes / Neighborhoods / Nets / Nucleotide sequence / Parasites / Parasitology / PCR / Plasmodium / Plasmodium - classification / Plasmodium - genetics / Plasmodium - isolation & purification / Plasmodium - physiology / Plasmodium falciparum / Plasmodium vivax / Population studies / Public health / quantitative polymerase chain reaction / Santé publique et épidémiologie / Seasons / Sequence analysis / Sequencing / Species / Spraying / Statistics / Surveys / Tropical Medicine / Vector-borne diseases / Veterinary Medicine/Veterinary Science / Virology / Young Adult