Molecular epidemiology of malaria vector mosquitoes in coastal areas of Southern Vietnam

BACKGROUND: This study presents the results of morphological genus-level identification of mosquitoes and molecular-genetic species-level identification of female Anopheles mosquitoes — the primary malaria vectors — collected in the Can Gio Biosphere Reserve, Ho Chi Minh Province. In addition, five species of human malaria parasites of the genus Plasmodium (P. falciparum, P. vivax, P. ovale, P. malariae, and P. knowlesi) were screened in the collected material.

AIM: To assess the species composition of vectors responsible for the most relevant and socially significant vector-borne infections in southern Vietnam during the dry and rainy seasons, and to identify active malaria foci.

METHODS: Arthropod collection was carried out in October 2024 and May 2025 in the Can Gio Biosphere Reserve (Ho Chi Minh Province). Adult hematophagous dipterans were collected using aspirators from hosts, entomological nets from vegetation, as well as from external surfaces of residential and utility buildings. Immature stages were collected by filtering water samples from natural and artificial water bodies suitable for mosquito breeding. Species identification of arthropods was performed based on morphological characteristics using dichotomous keys. Mosquito species identification and Plasmodium detection were conducted using polymerase chain reaction (PCR). Confirmation of Plasmodium ovale was performed by Sanger sequencing.

RESULTS: A total of 414 Anopheles mosquitoes were identified, of which 356 specimens (86%) belonged to An. epiroticus. DNA of Plasmodium parasites was detected in 32 mosquito samples: 17 (53.1%) positive for P. falciparum and 15 (46.9%) for P. ovale.

CONCLUSION: Despite a general decline in malaria incidence in Vietnam, foci of “forest malaria” remain active. In coastal areas of southern Vietnam, An. epiroticus plays an important role in maintaining active malaria transmission. In addition to spreading the causative agent of tropical malaria (P. falciparum), these vectors may also contribute to the transmission of P. ovale, thus sustaining foci of tertian malaria and potentially leading to cases of mixed infections.