Characterization of human exposure to Anopheles and Aedes bites using antibody-based biomarkers in rural zone of Cameroon

Abstract

Malaria and Aedes-borne diseases remain major causes of mortality, morbidity, and disability in most developing countries. Surveillance of transmission patterns associated with vector control remains strategic for combating these diseases. Due to the limitions of current surveillance tools used to assess human exposure to mosquito bites, human antibody (Ab) responses to salivary peptides from Anopheles (gSG6-P1) and Aedes (Nterm-34kDa) are increasingly being used to measure direct human-Anopheles or Aedes contact. This study reports on the assessment of Human IgG Ab responses to gSG6-P1 and Nterm-34-kDa salivary peptides as biomarkers to track exposure to Anopheles and Aedes bites, in rural localities of Cameroon. Blood samples were collected between October and November 2022 from 173 individuals residing in four villages: Njombe, Kekem, Belabo, and Ouami. Sociodemographic characteristics and information regarding Long Lasting Insecticide Net (LLIN) ownership, use, and net characteristics were recorded using a questionnaire. The measurement of human IgG levels to gSG6-P1 and Nterm-34kDa peptides was conducted in blood samples using ELISA. The levels of IgG responses to Anopheles gSG6-P1 and Aedes Nterm-34kDa salivary peptides varied significantly across villages (all p<0.05). IgG responses to Anopheles gSG6-P1 were higher in Njombe compared to Belabo and Ouami (all p<0.01), while IgG responses to Aedes Nterm-34kDa were higher in Kekem compared to the other villages (all p<0.0001). Aweak correlation was observed between IgG responses to Anopheles and Aedes salivary peptides (Spearman r = 0.2689, p = 0.0003). However, the median level of IgG to Anopheles gSG6-P1 was higher than IgG to Aedes Nterm-34kDa in Njombé, Belabo, and Ouami. Individuals not using their LLIN, those using damaged bed nets, and those who reported vegetation around their houses developed higher IgG responses to gSG6-P1 and Nterm-34 kDa compared to those who did not (all p<0.05). The immune-epidemiological biomarkers have shown promising potential as indicators for monitoring human exposure to various mosquito bites and their heterogeneity in the same site. However, additional research is needed to validate the efficacy of this technique for surveillance purposes and to assess the effectiveness of vector control interventions.

Fig 1. Map of Cameroon showing the study sites (Published by Ngangue-Siewe et al., 2022) [25].

Fig 2. Comparison between gSG6-P1 IgG levels and Nterm-34kDa IgG levels by village.

Triangular and round dots indicate individual IgG responses to gSG6-P1 and Nterm-34kDa salivary peptides, respectively, while red bars represent median values in each village. Statistically significant differences between all paired antibody levels (Wilcoxon paired test) are indicated. An. = Anopheles; Ae. = Aedes.

Fig 3. Comparison of exposure to Anopheles (antibody responses to gSG6-P1) and Aedes (antibody responses to Nterm-34) mosquitoes in the same individual.