Human and entomological determinants of malaria transmission in the Lihir Islands of Papua New Guinea: a cross-sectional study.

Background: The Lihir Islands of Papua New Guinea, located in an area with high burden of malaria and hosting a large mining operation, offer a unique opportunity to study transmission. There, we investigated human and vector factors influencing malaria transmission. Methods: In 2019, a cross-sectional study was conducted on 2,914 individuals assessing malaria prevalence through rapid diagnostic tests (RDT), microscopy, and quantitative PCR (qPCR). A logistic regression analysis identified infection-associated factors. Anopheles species distribution, biting behaviours, and sporozoite carriage were assessed through human landing catches and larval surveys. Results: Overall malaria prevalence (any species) was 3.6% by RDT, 4.5% by microscopy, and 15.0% by qPCR. P. vivax accounted for 37.1% of infections, P. falciparum for 34.6%, P. malariae for 3.0%, P. ovale 0.2%, and mixed infections for 24.5%. Prevalence (qPCR) varied across geographic areas, from 8.5% in the mine-impacted zone (MIZ) to 27.0% in the non-MIZ. Other factors independently associated with infection risk included cohabiting with an infected individual (aOR=1.94, 95%CI: 1.56-2.42), and residing in traditional housing (aOR=1.65, 95%CI: 1.21-2.25). Children had double the infection risk compared to adults, and the use of long-lasting insecticidal-treated nets did not decrease risk of infection. An. punctulatus was the major vector in one of the four geographical areas; while An. farauti was predominant in the rest of them, both with an early biting behaviour but with different biting intensities by geographical area. Entomological inoculation rates ranged from 26.9 (95%CI: 12.3-45.2) infective bites per person-year in the MIZ to 441.3 (95%CI: 315.7-572.1) in the non-MIZ. Conclusions: Malaria transmission and infection was lower in the MIZ compared to other areas, underscoring the potential of the mine company to enhance malaria control in Lihir. Measures focusing on at-risk groups, including vector-control and transmission interruption methods, could be used to reduce malaria burden, especially outside the MIZ. ### Competing Interest Statement The authors have declared no competing interest. ### Funding Statement Yes ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: The Institutional Review Board of the Papua New Guinea Institute of Medical Research (PNG-IMR) and the Papua New Guinea National Medical Research Advisory Committee (PNG-MRAC) gave ethical approval for this work, with MRAC number 18.07. I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable. Yes A dataset have been uploaded into the Supporting information files. This dataset have been modified to delete all information that could potentially identify or locate the study participants.