New insights into malaria vector bionomics in Lao PDR: a nationwide entomology survey

Abstract

Background . In Laos, the malaria burden remains high despite a significant reduction of cases during the last decade. In the context of the disease elimination by 2030, a nationwide entomological survey was conducted to better understand the distribution, abundance and behavior of major malaria vectors ( Anopheles spp.) in the country. Methods . Mosquito collections were implemented in ten villages from ten provinces during the rainy and dry seasons of 2014 and 2015 by using human landing catch (HLC) and cow bait collection (CBC) methods. After morphological identification in the field, molecular identification of the sibling species of Anopheles mosquitoes from the Funestus, Leucosphyrus, and Maculatus groups were determined using PCR specific alleles. A screening of Plasmodium falciparum and P. vivax infections in the vectors was carried out by quantitative PCR assays. Results. A total of 14,146 adult mosquitoes representing 25 different Anopheles species were collected and morphologically identified. Molecular identification revealed the presence of 12 sibling species within the main primary vector groups including An. maculatus s.s., An. rampae , An. sawadwongporni , An. pseudowillmori , An. dravidicus , An. minimus s.s., An. aconitus , An. pampanai , An. harrisoni , An. dirus s.s., An. baimaii , An. nemophilous . Anopheles maculatus and An. minimus were predominant during both the dry and rainy seasons, but showed highly zoophilic preferences (Zoophilic index of 98% and 95%, respectively). Overall, 22% of the total malaria vectors were collected between 10:00 PM and 5:00 AM indoors when people are sleeping. Twenty-seven percent of primary and secondary vectors were collected outdoors before 10:00 PM or after 5:00 AM, times when people are usually awake and outdoors. Only two specimens were positive for P. falciparum , one An. aconitus from Phongsaly and one An. minimus from Vientiane Province Conclusions. The results indicate that people living in rural areas in Laos are constantly exposed to malaria vectors throughout the year and specifically outdoors. The use of LLINs/IRS remains important but innovative tools and new strategies are needed to address locally, the early and outdoor malaria transmission. Lack of expertise in general entomological methods may further exacerbate the situation.

Vector Bionomics, Potential Vectors, Susceptibility and Bio-efficacy of LLINs Nets on Anopheles Mosquitoes in Nanyin Village Bunmouk Township Sagaing Region in Myanmar

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PfLDH Detected in Etawa Crossbred Goats Using Polymerase Chain Reaction Methods

“…The previous vector survey examined three species including Anopheles maculatus, Anopheles subpictus, and Anopheles aconitus in Jatirejo village (36). These species are zoo-anthropophilic -in other words, they like animal blood as well as human blood (13,37,38). The bite prevention strategies to ensure human health included the execution of IRS program (31) and distribution of LLINs (32); however, no similar strategies were developed to protect animals against Anopheles bites.…”

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