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The seasonal dynamics and biting behavior of potential Anopheles vectors of Plasmodium knowlesi in Palawan, Philippines

Malijan, Richard Paul B., Mechan, Frank, Braganza, Jessie C., Valle, Kristelle Mae R., Salazar, Ferdinand V., Torno, Majhalia M., Aure, Wilfredo E., Bacay, Brian A., Espino, Fe Esperanza, Torr, Steve ORCID:, Fornace, Kimberly M., Drakeley, Chris and Ferguson, Heather M. (2021) 'The seasonal dynamics and biting behavior of potential Anopheles vectors of Plasmodium knowlesi in Palawan, Philippines'. Parasites & Vectors, Vol 14, Issue 357.

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Background: A small number of human cases of the zoonotic malaria Plasmodium knowlesi have been reported in
Palawan Island, the Philippines. Identification of potential vector species and their bionomics is crucial for understanding
human exposure risk in this setting. Here, we combined longitudinal surveillance with a trap-evaluation study to
address knowledge gaps about the ecology and potential for zoonotic spillover of this macaque malaria in Palawan
Methods: The abundance, diversity and biting behavior of human-biting Anopheles mosquitoes were assessed
through monthly outdoor human landing catches (HLC) in three ecotypes representing different land use (forest
edge, forest and agricultural area) across 8 months. Additionally, the host preference and biting activity of potential
Anopheles vectors were assessed through comparison of their abundance and capture time in traps baited with
humans (HLC, human-baited electrocuting net—HEN) or macaques (monkey-baited trap—MBT, monkey-baited electrocuting
net—MEN). All female Anopheles mosquitoes were tested for the presence of Plasmodium parasites by PCR.
Results: Previously incriminated vectors Anopheles balabacensis and An. flavirostris accounted for > 95% of anophelines
caught in longitudinal surveillance. However, human biting densities were relatively low (An. balabacensis:
0.34–1.20 per night, An. flavirostris: 0–2 bites per night). Biting densities of An. balabacensis were highest in the forest
edge, while An. flavirostris was most abundant in the agricultural area. The abundance of An. balabacensis and An. flavirostris
was significantly higher in HLC than in MBT. None of the 357 female Anopheles mosquitoes tested for Plasmodium
infection were positive.
Conclusions: The relatively low density and lack of malaria infection in Anopheles mosquitoes sampled here indicates
that exposure to P. knowlesi in this setting is considerably lower than in neighboring countries (i.e. Malaysia), where it
is now the primary cause of malaria in humans. Although anophelines had lower abundance in MBTs than in HLCs, An.
balabacensis and An. flavirostris were caught by both methods, suggesting they could act as bridge vectors between
humans and macaques. These species bite primarily outdoors during the early evening, confirming that insecticidetreated
nets are unlikely to provide protection against P. knowlesi vectors

Item Type: Article
Subjects: QX Parasitology > Insects. Other Parasites > QX 510 Mosquitoes
QX Parasitology > Insects. Other Parasites > QX 515 Anopheles
WA Public Health > Preventive Medicine > WA 110 Prevention and control of communicable diseases. Transmission of infectious diseases
WA Public Health > Health Problems of Special Population Groups > WA 395 Health in developing countries
Faculty: Department: Biological Sciences > Vector Biology Department
Digital Object Identifer (DOI):
Depositing User: Samantha Sheldrake
Date Deposited: 14 Sep 2021 09:10
Last Modified: 14 Sep 2021 09:10


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