Rapid Fire Presentation 8th International Conference on Plasmodium vivax Research 2022

Infectivity of clinical and asymptomatic malaria cases to Anopheles farauti s. s.mosquitoes in Papua New Guinea (#400)

Lincoln Timinao 1 2 , Rebecca Vinit 1 , Esther W Jamea 1 , Elma Nate 1 , Henson Dima 1 , Clemencia Ibam 1 , Thomas R Burkot 2 , Daniel Schofield 2 , Moses Laman 1 , Ivo Mueller 1 , Leanne J Robinson 3 4 5 , Stephan Karl 2
  1. Vector Borne Disease Unit, PNG Institute of Medical Research, Madang, Papua New Guinea
  2. Australian Institute of Tropical Health and Medicine, James Cook University, Smithfield, QLD, Australia
  3. Burnet Institute, Melbourne, VIC, Australia
  4. Walter and Elisa Hall Institute of Medical Research, Melbourne, VIC, Australia
  5. Department of Medical Biology, The Unisversity of Melbourne, Melbourne, VIC, Australia

Transmission of malaria parasites arises from both asymptomatic parasite carriers and symptomatic clinical malaria cases. Understanding the infectiousness of these different sub-populations is important for targeting malaria control interventions towards interrupting transmission. Using an Anopheles farauti colony, we performed direct skin feeding assays on 11 asymptomatic parasite carriers identified in a population of 103 individuals from a highly endemic village in Madang Province, Papua New Guinea using a rapid diagnostic tests (RDT) and qPCR techniques. We also conducted membrane feeding assays with samples from 182 clinical patients from two local health facilities enrolled on the basis of positive RDTs. All samples were further characterized retrospectively using expert light microscopy (LM) and qPCR. In the asymptomatic parasite carriers, 2/11 were diagnosed by qPCR as Plasmodium vivax carriers while 3/11 were diagnosed with P. falciparum. Only two P. vivax positive individuals successfully infected An. farauti colony mosquitoes. Retrospective microscopy diagnosis confirmed that the two participants were P. vivax positive with one having detectable gametocyte stages. The remaining 6/11 were qPCR negative but RDT positive. Of the 182 samples from clinical malaria cases, 38 (21%) resulted in successful mosquito infections. 10% (8/80) of qPCR diagnosed P. falciparum cases gave rise to mosquito infections and 44% (24/55) of P. vivax cases were infectious to mosquitoes. Similarly 11% (10/88) of LM-diagnosed P. falciparum and 44% (23/52) of P. vivax were infectious, with an increase in mosquito infection rate to 58% (14/24) for P. vivax gametocyte carriers. Interestingly, 7.4% (2/27) of samples from patients who were negative by qPCR resulted in successful mosquito infection. Overall, P. vivax appeared to be more infectious in both, clinical and asymptomatic populations. In further studies, we plan to test more asymptomatic parasite carriers in order to understand the differences in infectiousness of clinical versus asymptomatic malaria parasite carriers in PNG.