Effects of larvicidal and larval nutritional stresses on Anopheles gambiae development, survival and competence for Plasmodium falciparum.
BACKGROUND
Many studies have shown that the environment in which larvae develop can influence adult characteristics with consequences for the transmission of pathogens. We investigated how two environmental stresses (larviciding and nutritional stress) interact to affect Anopheles gambiae (previously An. gambiae S molecular form) life history traits and its susceptibility for field isolates of its natural malaria agent Plasmodium falciparum.


METHODS
Larvae were reared in the presence or not of a sub-lethal concentration of larvicide and under a high and low food regimen. Development time, individual size, adult survival and competence for P. falciparum were assessed.


RESULTS
Individuals under low food regimen took more time to develop, had a lower development success and were smaller while there was no main effect of larvicide exposure on these traits. However, larvicide exposure impacted individual size in interaction with nutritional stress. Female survival was affected by the interaction between gametocytemia, parasite exposure and larval diet, as well as the interaction between gametocytemia, parasite exposure and larvicidal stress, and the interaction between gametocytemia, larvicidal exposure and larval diet. Among the 951 females dissected 7 days post-infection, 559 (58.78%) harboured parasites. Parasite prevalence was significantly affected by the interaction between larvicidal stress and larval diet. Indeed, females under low food regimen had a higher prevalence than females under high food regimen and this difference was greater under larvicidal stress. The two stresses did not impact parasite intensity.


CONCLUSIONS
We found that larval nutritional and larvicidal stresses affect mosquito life history traits in complex ways, which could greatly affect P. falciparum transmission. Further studies combining field-based trials on larvicide use and mosquito experimental infections would give a more accurate understanding of the effects of this vector control tool on malaria transmission.
MIVEGEC (Maladies Infectieuses et Vecteurs: Ecologie, Génétique, Evolution et Contrôle), UMR IRD 224-CNRS 5290-Université de Montpellier, Montpellier, France. amelie.vantaux@gmail.com.|Institut de Recherche en Sciences de la Santé (IRSS), Bobo Dioulasso, Burkina Faso. amelie.vantaux@gmail.com.
Amélie
A
Vantaux
Institut de Recherche en Sciences de la Santé (IRSS), Bobo Dioulasso, Burkina Faso.
Issiaka
I
Ouattarra
MIVEGEC (Maladies Infectieuses et Vecteurs: Ecologie, Génétique, Evolution et Contrôle), UMR IRD 224-CNRS 5290-Université de Montpellier, Montpellier, France.|Institut de Recherche en Sciences de la Santé (IRSS), Bobo Dioulasso, Burkina Faso.
Thierry
T
Lefèvre
Institut de Recherche en Sciences de la Santé (IRSS), Bobo Dioulasso, Burkina Faso.|Centre Muraz, Bobo Dioulasso, Burkina Faso.
Kounbobr Roch
KR
Dabiré
D000821:Animal Feed; D000818:Animals; D000852:Anopheles / Q000469:parasitology / Q000502:physiology*; D000898:Antibiosis; D001413:Bacillus thuringiensis / Q000145:classification* / Q000502:physiology; D005260:Female; D007303:Insect Vectors; D007814:Larva / Q000254:growth & development; D010963:Plasmodium falciparum / Q000502:physiology*; D014921:Wings, Animal / Q000033:anatomy & histology / Q000254:growth & development
Bti; Larval diet; Larvicide; Malaria parasite; Mosquito competence; Plasmodium falciparum; Stress