Serological signatures of declining exposure following intensification of integrated malaria control in two rural Senegalese communities

PLoS One. 2017 Jun 13;12(6):e0179146. doi: 10.1371/journal.pone.0179146. eCollection 2017.

Abstract

Recent control scale-up has reduced malaria in many areas but new tools are needed to monitor further progress, including indicators of decreasing exposure to parasite infection. Although serology is considered a promising approach in this regard, the serological impact of control interventions has been so far studied using indirect quantification of exposure. Cohort surveys concomitantly recording entomological and malariometric indices have been conducted in two Senegalese settings where supervised control intensification implemented in 2006 shifted malaria from historically holoendemic in Dielmo and mesoendemic in Ndiop to hypoendemic in both settings by 2013. We analyse here serological signatures of declining transmission using archived blood samples. Responses against ten pre-erythrocytic and erythrocytic antigens from Plasmodium falciparum and P. malariae alongside an Anopheles gambiae salivary gland antigen were analysed. Cross-sectional surveys conducted before (2002) and after (2013) control intensification showed a major impact of control intensification in both settings. The age-associated prevalence, magnitude and breadth of the IgG responses to all antigens were village-specific in 2002. In 2013, remarkably similar patterns were observed in both villages, with marginal responses against all parasite antigens in the 0-5y children and reduced responses in all previously seropositive age groups. Waning of humoral responses of individuals who were immune at the time of control intensification was studied from 2006 to 2013 using yearly samplings. Longitudinal data were analysed using the Cochran-Armittage trend test and an age-related reversible catalytic conversion model. This showed that the antigen-specific antibody declines were more rapid in older children than adults. There was a strong association of antibody decline with the declining entomological inoculation rate. We thus identified serological markers of declining exposure to malaria parasites that should help future monitoring of progress towards malaria elimination.

Publication types

  • Multicenter Study

MeSH terms

  • Adolescent
  • Adult
  • Animals
  • Anopheles / immunology
  • Anopheles / parasitology
  • Antibodies, Protozoan / blood
  • Antibodies, Protozoan / immunology
  • Antigens, Protozoan / blood
  • Antigens, Protozoan / immunology
  • Child
  • Cohort Studies
  • Cross-Sectional Studies
  • Enzyme-Linked Immunosorbent Assay
  • Female
  • Health Surveys / methods
  • Health Surveys / statistics & numerical data
  • Host-Parasite Interactions / immunology
  • Humans
  • Immunoglobulin G / blood
  • Immunoglobulin G / immunology
  • Malaria, Falciparum / epidemiology
  • Malaria, Falciparum / immunology*
  • Malaria, Falciparum / parasitology
  • Male
  • Plasmodium falciparum / immunology*
  • Plasmodium falciparum / physiology
  • Prevalence
  • Rural Health / statistics & numerical data*
  • Rural Population / statistics & numerical data*
  • Salivary Glands / immunology
  • Senegal / epidemiology
  • Young Adult

Substances

  • Antibodies, Protozoan
  • Antigens, Protozoan
  • Immunoglobulin G

Grants and funding

The work was supported by grants from the Institut Pasteur Foundation, the prix Jacques Piraud of the Fondation pour la Recherche Médicale and grants from Institut Pasteur ACIP 25_2012 and from the Rotary International associated with the Rotary Paris Alliance and Rotary Dakar Almadies.