Malaria remains a public health problem in Thailand, especially along its borders where highly mobile populations can contribute to persistent transmission. This study aimed to determine resistant genotypes and phenotypes of 112 Plasmodium falciparum isolates from patients along the Thai-Cambodia border during 2013–2015. The majority of parasites harbored a pfmdr1-Y184F mutation. A single pfmdr1 copy number had CVIET haplotype of amino acids 72–76 of pfcrt and no pfcytb mutations. All isolates had a single pfk13 point mutation (R539T, R539I, or C580Y), and increased % survival in the ring-stage survival assay (except for R539I). Multiple copies of pfpm2 and pfcrt-F145I were detected in 2014 (12.8%) and increased to 30.4% in 2015. Parasites containing either multiple pfpm2 copies with and without pfcrt-F145I or a single pfpm2 copy with pfcrt-F145I exhibited elevated IC(90) values of piperaquine. Collectively, the emergence of these resistance patterns in Thailand near Cambodia border mirrored the reports of dihydroartemisinin-piperaquine treatment failures in the adjacent province of Cambodia, Oddar Meanchey, suggesting a migration of parasites across the border. As malaria elimination efforts ramp up in Southeast Asia, host nations militaries and other groups in border regions need to coordinate the proposed interventions.
Abstract Vector-borne infections (VBI) are defined as infectious diseases transmitted by the bite or mechanical transfer of arthropod vectors. They constitute a significant proportion of the global infectious disease burden. United States (U.S.) Department of Defense (DoD) personnel are especially vulnerable to VBIs due to occupational contact with arthropod vectors, immunological naiveté to previously unencountered pathogens, and limited diagnostic and treatment options available in the austere and unstable environments sometimes associated with military operations. In addition to the risk uniquely encountered by military populations, other factors have driven the worldwide emergence of VBIs. Unprecedented levels of global travel, tourism and trade, and blurred lines of demarcation between zoonotic VBI reservoirs and human populations increase vector exposure. Urban growth in previously undeveloped regions and perturbations in global weather patterns also contribute to the rise of VBIs. The Armed Forces Health Surveillance Center-Global Emerging Infections Surveillance and Response System (AFHSC-GEIS) and its partners at DoD overseas laboratories form a network to better characterize the nature, emergence and growth of VBIs globally. In 2009 the network tested 19,730 specimens from 25 sites for Plasmodium species and malaria drug resistance phenotypes and nearly another 10,000 samples to determine the etiologies of non- Plasmodium species VBIs from regions spanning from Oceania to Africa, South America, and northeast, south and Southeast Asia. This review describes recent VBI-related epidemiological studies conducted by AFHSC-GEIS partner laboratories within the OCONUS DoD laboratory network emphasizing their impact on human populations.
Background: The Australian Government's Pacific Malaria Initiative (PacMI) is supporting the National Malaria Program in both Solomon Islands and Vanuatu, complementing assistance from the Global Fund for AIDS, Tuberculosis and Malaria (GFATM). Two remote island groups - Tafea Province, Vanuatu and Temotu Province, Solomon Islands have been selected by the governments of both countries as possible malaria elimination areas. To provide information on the prevalence and distribution of the disease within these island groups, malariometric surveys were conducted during the wet seasons of 2008. Methods: In Tafea Province, a school-based survey was conducted which included the 2-12 y age group, while in Temotu a village based all-ages survey was conducted. An effort was made to sample villages or schools from a wide an area as possible on all islands. Diagnosis was initially based on Giemsa stained blood slides followed by molecular analysis using polymerase chain reaction (PCR). Results: In Tafea Province, 73% (5238/7150) of children (2-12 y) were surveyed and in Temotu Province, in the all-ages survey, 50.2% (8742/17410) of the provincial population participated in the survey. In both Vanuatu and Solomon Islands malariometric surveys of their southern-most islands in 2008 showed relatively low over-all malaria parasite prevalence (2 to 3%). Other features of malaria in these island groups were low parasitaemia, low gametocyte carriage rates, low spleen rates, low malaria associated morbidity, a high incidence of asymptomatic infections, and a predominance of Plasmodium vivax over Plasmodium falciparum. Conclusion: For various reasons malaria rates are declining in these provinces providing a favourable situation for local malaria elimination. This will be advanced using mass distribution of bed nets and selective indoor residual spraying, the introduction of rapid diagnostic tests and artemisinin combination therapy, and intensive case detection and surveillance. It is as yet uncertain whether malaria parasites can themselves be sustainably eliminated from entire Melanesian islands, where they have previously been endemic. Key issues on the road to malaria elimination will be continued community involvement, improved field diagnostic methods and elimination of residual P. vivax parasites from the liver of asymptomatic persons.
