Abstract
BackgroundMost hematophagous insects use host odours as chemical cues. The odour components, some physiological parameters and host attractiveness are affected by several conditions, including infection by parasites, e.g., plasmodia and, therefore, change the epidemiological scenario. This study evaluated the attractiveness of individuals with vivax malaria before, during (7 days) and after treatment (14 days) with specific antimalarial drugs.FindingsMosquito attractiveness to vivax-infected patients was assessed using a vertical olfactometer using the foot as a source of body odour. The ratio of Anopheles darlingi mosquitoes in the lower chamber of the olfactometer was used to calculate the attractiveness, and patient temperature was measured using a digital thermometer. An increased attractiveness was found only in patients bearing vivax gametocytes during the first experiment (early infection) (P < 0.001). Patients in the first experiment tended to have a higher body temperature, but grouping patients into fever and non-fever resulted in a higher attractiveness only in the fever group of gametocyte carriers, suggesting a synergistic effect of temperature and gametocytes in the host attractiveness to A. darlingi.ConclusionsGametocyte presence and fever in vivax malaria patients increased short distance host attractiveness to An. darlingi.
Highlights
Most hematophagous insects use host odours as chemical cues
After 7 and 14 days of treatment, no significant differences in mosquito attractiveness to patients previously infected with different forms of P. vivax was detected, but mosquito number tended to be lower in patients previously bearing gametocytes (Figure 1)
In a semi-field condition study conducted in Kenya, Lacroix and colleagues [4] found that children carrying gametocytes attracted twice as many An. gambiae in relation to uninfected children and children infected with asexual forms of Plasmodium, corroborating the results obtained in the present work for short distance attractiveness
Summary
This study was approved by the local Ethics Committee (CEP) of the Research Centre of Tropical Medicine of Rondônia (Cepem - RO), protocol number 091/2009.The behavioral experiments on Anopheles darlingi were performed at the Laboratory of Entomology of the Fundação Oswaldo Cruz (FIOCRUZ-RO) in Porto Velho, Rondonia state, Brazil. Six people completed all the experimental phases and 11 people participated in the first phase. Patients from both sexes, with an age range from 20 to 50 years, diagnosed with vivax malaria with or without gametocytes by blood smear, performed the experiments in a vertical olfactometer [5]. Each experiment was replicated three times using 10 F1 An. darlingi females, which were 5 days old and deprived of a sugar meal for 12 hours. A total of 10 minutes for each experiment included five minutes prior to stimulation with no odour or heat sources and five minutes with odour and heat sources, i.e., patient foot under the lower chamber. Mosquitoes were introduced into the upper chamber of the olfactometer and the result was defined by the sum of mosquitoes present in the lower chamber at the end of all replicates
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