Tropical Medicine and Health最新文献

Background: Aedes mosquitoes are primary vectors of arboviral diseases, such as dengue, chikungunya, and Zika, posing major threats to tropical public health. Understanding their spatial distribution and resistance status is vital for sustainable control. This study investigated the mapping of breeding habitats, species composition, and insecticide susceptibility in Aedes populations from Osun State, Nigeria.

Methods: Larval surveys across a rural community identified 36 potential habitats, of which 27.8% were positive for Aedes breeding. A total of 3500 larvae were collected, reared to adult stage, morphologically identified and subjected to WHO-standard insecticide bioassays.

Results: Two species were identified: Aedes aegypti (99.3%) and Aedes albopictus (0.7%), with Ae. aegypti strongly predominant (p < 0.05). Mortality rates following insecticide exposure ranged from 94 to 100%. Complete susceptibility was observed for permethrin, deltamethrin, and pirimiphos-methyl, while reduced mortality (94%) against alpha-cypermethrin indicated possible emerging resistance. The mapping of larval habitats revealed clustered breeding in rural communities, portending localized risk of arboviral transmission.

Conclusions: These findings highlight that while Aedes populations in the study area remain largely susceptible to conventional insecticides, early signals of resistance require proactive management by the state. Incorporating synergists into integrated vector control, alongside habitat surveillance and mapping, will be critical to sustaining insecticide effectiveness and reducing the burden of Aedes-borne diseases in Osun State and Nigeria at large.

Background: Global vaccine coverage improved substantially. In Afghanistan, routine immunization has been expanding since 1978 but remains inadequate, contributing to consistently high under-five mortality rates. This time-trend analysis focused on national routine childhood immunization coverage and the number of Expanded Programme on Immunization (EPI) centers in Afghanistan from 1999 to 2023.

Methods: Data were drawn from World Health Organization/United Nations Children's Fund (WHO/UNICEF) estimates and the "Gavi, the Vaccine Alliance" administrative reports (1999-2018). Seven vaccines were assessed: third dose of polio vaccine (Pol3), first and second doses of measles-containing vaccine (MCV1, MCV2), first and third doses of diphtheria-tetanus-pertussis vaccine (DTP1, DTP3), Bacillus Calmette-Guérin (BCG), and third dose of hepatitis B vaccine (HepB3). Linear spline regression, with knots in 2006 and 2018, was validated.

Results: Between 1999 and 2023, coverage of all seven vaccines increased. WHO/UNICEF data showed Pol3 rising from 27% to 68%, MCV1 from 31% to 55%, DTP1 from 15.2% to 67%, DTP3 from 27% to 60%, and BCG from 38% to 68%, with MCV2 growing from 2% to 42% and HepB3 peaking at 67%. Spline regression revealed rapid growth from 1999 to 2006, slower increases from 2007 to 2018, and declines from 2019 to 2023. Gavi data mirrored these patterns, with DTP3 rising by 7.96% annually from 1999 to 2006 and DTP1 falling by 0.30% from 2007 to 2018. EPI centers expanded by 159.78 per year (2001-2006) and 74.12 (2007-2018).

Conclusions: Afghanistan's immunization coverage increased substantially until 2006, grew more slowly from 2007 to 2018, and declined after 2019. These patterns highlight the vulnerability of routine immunization programs to contextual challenges and suggest that sustaining coverage will require continued strengthening of routine services, monitoring subnational disparities, and implementing conflict-sensitive strategies.

Background: To help with planning malaria vector control in Benin, the National Malaria Control Program launched a study to update the distribution of major malaria vectors and their role in Plasmodium falciparum transmission. The study aimed to go beyond the standard entomological inoculation rate (EIR) by incorporating the average sporozoite load of the mosquitoes. This is because the parasite load is a key factor in a successful infection. The research proposed combining the average P. falciparum sporozoite load with EIR to better determine the vectors' true contribution to malaria transmission.

Methods: The study was conducted across 18 communes in Benin. Within each commune, two villages were chosen for mosquito collection using human landing catches (HLC) and pyrethrum spray catches (PSC). Heads and thoraxes from female Anopheles gambiae s.l. and Anopheles funestus mosquitoes were analyzed for the Plasmodium falciparum circumsporozoite antigen using the ELISA/CSP method. The corresponding carcasses were used for species identification via PCR. The P. falciparum sporozoite load was quantified in CSP ELISA-positive mosquitoes using the NZYTech real-time PCR kit. The contribution of vectors to P. falciparum transmission was first estimated by considering both their infection and bite rates. Subsequently, the relative contribution to transmission was further assessed by correlating the P. falciparum sporozoite load of the primary vectors with EIR.

Results: Anopheles coluzzii is responsible for 63.01% of malaria transmission, with an EIR of 87.7 infecting bites per person per year. This is followed by Anopheles gambiae, which accounts for 36.7% of transmission and has an EIR of 51.1 infecting bites per person per year. The contribution of Anopheles funestus is 0.24%. The study found that An. gambiae carries a higher load of Plasmodium falciparum sporozoites than An. coluzzii. Specifically, approximately 30% of An. gambiae individuals carried more than 10,000 sporozoites in their salivary glands, while less than 10% of An. coluzzii individuals had a comparable load.

Conclusion: This study clarifies the true contribution of malaria vectors to Plasmodium falciparum transmission by linking sporozoite load to the EIR. The findings will allow for a more accurate assessment of the vectors' role in P. falciparum transmission in Benin.

Background: Primary liver cancer (PLC) ranks as the third leading cause of cancer-related mortality worldwide, posing a serious global public health burden. Hepatocellular carcinoma (HCC) is the most common subtype, accounting for approximately 75%-85% of all PLC cases. In recent years, environmental pollution has emerged as a potential risk factor for PLC. However, a systematic bibliometric analysis of global research trends in this field remains lacking. This study aims to perform a comprehensive bibliometric analysis to explore global trends in the field of environmental pollution and PLC research from 2000 to 2025.

Methods: We conducted a bibliometric analysis using the Web of Science Core Collection database, covering studies published from January 2000 to March 2025. CiteSpace was used to analyze publication trends, global collaborations, and key research areas through network visualizations and co-occurrence analyses.

Results: A total of 562 publications were included in this study, with China and the United States identified as the leading contributors. Prominent institutions in this field include the National Institutes of Health (USA), National Cancer Institute (USA), and the Chinese Academy of Sciences. Among journals, Environmental Health Perspectives, Hepatology, and Cancer Research were the most frequently cited, indicating a close connection between environmental science and oncology. Keyword analysis revealed that research focuses not only on traditional pollutants such as air pollution and heavy metals, but also on emerging exposures including volatile organic compounds and drinking water contaminants. Mechanistic studies remain at the core of this field, with frequently occurring terms such as "oxidative stress", "gene expression", and "inflammation". Meanwhile, clinical research-related keywords like "epidemiology" and "follow-up" have become increasingly prominent in recent years, indicating a growing emphasis on population-based risk assessment.

Conclusions: This study highlights the growing research interest in the link between environmental pollution and PLC. Cross-disciplinary collaborations between environmental science, medicine, and public health are increasingly influencing the development of this field. Future research should focus on elucidating the carcinogenic mechanisms of pollutants and enhancing translational applications in public health.

Background: Disease burden attributable to extreme high temperature requires more attention amid dramatic climate change, especially in South Asia and Southeast Asia.

Methods: We analyzed comprehensive estimates from the GBD 2021 Study, examining mortality and disability-adjusted life years (DALYs) across 369 diseases and 88 risk factors. This study employed joinpoint regression analysis and Age-Period-Cohort modeling to examine time trends from 1990 to 2021 and projected disease burden up to 2045 by incorporating demographic forecasts and a Bayesian Age-Period-Cohort model.

Results: South Asia and Southeast Asia contributed more than half of the global death number attributed to high temperature. In 2021, South Asia recorded 209,537 deaths and Southeast Asia recorded 32,230 deaths attributed to high temperatures. In South Asia and Southeast Asia, Pakistan bore the highest number and rate of deaths attributed to high temperature. The population above 55 and below 5 years in South Asia and Southeast Asia experienced higher disease burden attributed to high temperature. The leading cause of ASMR attributed to high temperature in South Asia and Southeast Asia was non-communicable diseases. Population growth and aging were the main drivers of ASMR increases in South Asia and Southeast Asia, while epidemiological changes contributed to a reduction in ASMR. Deaths attributed to high temperatures in South and Southeast Asia are projected to rise until 2045, with South Asia exceeding 400,000 and Southeast Asia approaching 100,000 deaths in 2045.

Conclusions: This study highlights the urgent need for region-specific, gender-specific and age-specific interventions to reduce high temperature-related disease burden in South Asia and Southeast Asia.

The study by Nikièma et al. demonstrates the absence of Wuchereria bancrofti infection in Anopheles mosquitoes a decade after cessation of mass drug administration (MDA) in Burkina Faso. This rare longitudinal evidence underscores the utility of molecular xenomonitoring (MX) as a sensitive early-warning tool that complements traditional transmission assessment surveys (TAS). MX enables detection of recrudescence earlier than human-based diagnostics, particularly in low-prevalence settings, and offers opportunities for integration with malaria vector surveillance. Ethical and operational challenges associated with human landing catches highlight the need for alternative trapping methods to maintain MX sensitivity safely. Sustaining lymphatic filariasis elimination globally will depend on institutionalizing MX alongside TAS, ensuring robust surveillance, and safeguarding long-term programmatic gains.

Background: Scrub typhus is an important zoonotic disease with rising incidence globally. Meteorological factors may influence its transmission dynamics. However, inconsistencies across studies and limited quantitative evidence highlight the need for further investigation.

Objective: To systematically evaluate the linear and nonlinear associations between various meteorological factors and scrub typhus incidence, explore lagged effects and potential sources of heterogeneity, and analyze inconsistencies in existing findings.

Method: We searched PubMed, Scopus, Web of Science, and Embase for studies published up to February 2025. Relevant articles were identified based on predefined inclusion and exclusion criteria. We conducted linear meta-analyses to assess the effects of unit changes in meteorological factors and dose-response meta-analyses to evaluate cumulative lagged risks across different exposure levels. Subgroup and sensitivity analyses were conducted to explore sources of heterogeneity and assess result robustness.

Results: Seventeen studies were included, covering China, Korea, Laos, and India. Eleven studies contributed to linear meta-analyses, and six to dose-response analyses. Ambient temperature (RR 1.08, 95% CI 1.02-1.16), land surface temperature (RR 1.06, 95% CI 1.02-1.09), precipitation (RR 1.01, 95% CI 1.01-1.02), relative humidity (RR 1.07, 95% CI 1.04-1.11), and atmospheric pressure (RR 1.06, 95% CI 0.91-1.23) were positively associated with the risk of scrub typhus. Wind speed (RR 0.59, 95% CI 0.49-0.71) and sunshine duration (RR 0.92, 95% CI 0.77-1.10) exhibited negative associations. Dose-response meta-analysis revealed inverted U-shaped relationships for ambient temperature and relative humidity, and a unimodal pattern for precipitation, with risk increasing continuously at high levels. Significant lag effects were observed: precipitation had the most immediate effect (lag0: RR 1.05), while ambient temperature (lag1: RR 1.18) and relative humidity (lag2: RR 1.28) peaked with a 1- to 2-month delay. Geographic variation was identified as a major source of between-study heterogeneity.

Conclusion: Although this study has certain limitations, including the small number of included studies, their concentration mainly in China, and the presence of substantial heterogeneity, the results provide evidence of linear and nonlinear associations between meteorological factors and scrub typhus incidence, and highlight the roles of geographical variation and lag effects. These findings offer quantitative evidence and scientific support for disease prevention and control in the context of climate change.

We commend Oh et al.'s recent analysis of TB preventive treatment (TPT) in the Western Pacific Region, but note important gaps and ways forward. We first caution that reliance on routine program data may overestimate gains. For example, China's passive surveillance misses ≈20% of cases [1]. Prospective cohorts or integrated surveillance including clinical databases could validate coverage estimates. We also urge attention to overlooked risk groups beyond children and PLHIV (as highlighted by Oh et al. [2]), groups like healthcare workers, prisoners, and people with diabetes warrant targeted TPT pilots (e.g., occupational health or prison-based programs). In the Philippines, ~ 36% of TB patients first seek private care [3], so partnering with private clinics and pharmacies is essential to reach all contacts. Likewise, MDR-TB contacts were underemphasized; WHO now strongly recommends a 6-month levofloxacin regimen for MDR contacts [4]. We encourage pilot studies of this regimen (as in Mongolia [5]) and operational research on MDR-TPT. Finally, policy does not guarantee practice as Cambodia and Lao PDR have guidelines, yet stockouts and training gaps persist [6, 7]. Embedding TPT in universal health insurance and conducting cost effectiveness studies will support sustainable scale-up. In sum, by suggesting concrete examples and research strategies for each country, we aim to refine Oh et al.'s insights into actionable steps for TPT acceleration.

Introduction: Somalia, the 44th largest country in the world by land area, struggles with a heavy burden of infectious diseases. Since 1991, populations have lacked essential health services, exacerbated by recurring infectious-disease outbreaks. Recurrent outbreaks of measles, cholera, and polio have devastated public health, generating significant morbidity and mortality. Despite improvements through new graduates, these issues remain unresolved. This study examines the impact of climate change on infectious-disease outbreaks in Somalia focusing on cholera, measles, and polio-to fill a gap in the literature by linking climate variability with outbreak dynamics and identifying weaknesses in Somalia's health system. The findings will inform targeted public-health strategies.

Method: Following PRISMA guidelines, we undertook a narrative review of English-language literature (1990 - March 2025). Searches in PubMed, Scopus, Web of Science and Google Scholar combined terms for infectious-disease outbreaks, climate change and Somalia/Horn of Africa. Of 202 records identified, 74 met inclusion criteria. Two reviewers independently screened, extracted data and applied six-step inductive coding in NVivo 12, synthesizing findings into thematic domains.

Results: Four interlinked themes emerged. (1) Fragile health system: < 0.4 doctors, nurses and midwives per 10 000 population, poorly equipped facilities and patchy surveillance. (2) Control measures: routine immunization completeness ≈20%; limited oral-cholera-vaccine and WASH coverage sustain transmission. (3) Political instability and conflict: insecurity, decentralized coordination and ≥ 2.6 million IDPs hamper rapid response. (4) Impact of climate change: drought-induced water scarcity and flood-related latrine breaches create year-round face-oral exposure, while climate shocks divert resources and swell susceptibility pools.

Conclusion: Outbreak control in Somalia now hinges on integrating climate adaptation with health-system strengthening. Climate-proofed WASH infrastructure, mobile vaccination and surveillance linked to hydro-meteorological alerts, a National Outbreak Operations Centre, and ring-fenced financing are urgent priorities. Without such measures each extreme-weather event will erase hard-won gains; with them, Somalia can break the climate-outbreak feedback loop.

Background: Community health workers (CHWs) are vital for improving maternal and child health (MCH) in underserved settings; however, gender norms often influence their functioning. In the Lao PDR, Village Health Volunteers (VHVs) serve as frontline CHWs in rural areas. Xepon District is a remote border area with Vietnam, characterized by underserved conditions, limited health access, and predominantly ethnic minority populations. The VHV workforce in this district is largely male, which restricts culturally acceptable outreach to women and underscores the need to test a paired male-female model. To address this gender-related limitation, a provincial pilot program introduced male-female VHV/VHW pairs to strengthen MCH outreach.

Objectives: This study aims to explore how the male-female paired VHV model functions in remote ethnic minority communities and its contributions to maternal health promotion.

Methods: A qualitative descriptive study was conducted in 19 pilot villages in Xepon District, Savannakhet Province, from June to October 2024. Semi-structured interviews were held with 42 participants, including mothers, their partners, VHVs, village leaders, health center staff, and district/provincial health officials. Interviews were transcribed, translated, and analyzed using inductive thematic analysis based on Braun and Clarke's six-phase framework.

Results: Four key themes emerged: (1) building trust and comfort through gender-matched interactions; (2) gender-specific responsibilities and task sharing between paired VHVs; (3) strengthening family support and health system linkages through female VHV/VHWs engagement; and (4) challenges and support needs for strengthening the VHV Program. Female VHV/VHWs played a crucial role in culturally sensitive maternal outreach, whereas male VHVs facilitated engagement with male household members and community leaders. Paired implementation enhanced service utilization and helped shift household norms. However, challenges persisted, including gender selection barriers, literacy gaps, and limited institutional support for paired training and supervision.

Conclusion: The male-female VHV/VHWs model may enhance access to MCH services by engaging men and women in complementary roles tailored to local contexts. To maximize its potential, institutional commitment is needed to formalize pair-based training, address gender barriers in recruitment, and strengthen community- and policy-level support systems for CHWs. Given the 2023 PHC policy, embedding gender-sensitive and context-specific approaches into guidelines and training manuals may be critical for aligning service delivery with sociocultural realities and ensuring responsiveness to the unique needs of remote communities.