Tropical Medicine and Health最新文献

Background: Rotavirus is the leading cause of acute gastroenteritis among children under five years of age globally. In Kenya, rotavirus vaccination was introduced in 2014 using Rotarix® (G1P[8]), with a subsequent national transition to Rotavac® (G9P[11]) vaccine, in 2023. Evidence on post-introduction rotavirus disease burden, strain diversity, and Rotavac® vaccine effectiveness in Kenya remains limited. This study assessed the burden of rotavirus gastroenteritis and vaccine effectiveness of the rotavirus vaccine among children under five years of age in Nairobi's urban slums, after the rollout of the Rotavac® vaccine.

Methods: In this cross-sectional surveillance study, 353 stool samples were collected from children under five years of age presenting with acute gastroenteritis at selected health facilities in Mukuru informal settlement, Nairobi, between October 2023 and November 2024. The samples were analyzed using TaqMan array card PCR and multiplexed semi-nested RT-PCR. Vaccine effectiveness for overall rotavirus vaccination and Rotavac® specifically was estimated using a post-hoc test-negative case-control analysis.

Results: Rotavirus was detected in 19.5% (69/353; 95% CI 15.5-24.1%) of the samples. The highest detection occurred among children aged 12-23 months at 24.4% (30/123; 95% CI 17.1-33.0%), with significant differences across age groups (p = 0.023). Rotavirus prevalence was significantly lower among vaccinated children 18.4% (60/327; 95% CI 14.3-23.0%), compared with unvaccinated children 34.6% (9/26; 95% CI 17.2-55.7%) (p = 0.044). The predominant strain was G2P[4] (29.0%; 20/69), which also dominated among the vaccinated children (31.7%; 19/60), while G12P[6] was most frequent among unvaccinated children (33.3%; 3/9). Newly detected strains included G2P[8] and G12P[8], and two equine-like strains (G3P[8]eG3 and G2G3P[4]P[8]eG3). Short electropherotypes predominated. First-dose vaccine coverage was 92.6% (327/353) while the last-dose coverage was 76.2% (269/353). Estimated Rotavac® vaccine effectiveness was 74.1% (95% CI 16.3-92.0%), and overall rotavirus vaccine effectiveness was 57.6% (95% CI 18.1-99.8%).

Conclusion: Rotavirus remains a significant cause of gastroenteritis among children in Nairobi's urban informal settlements. The circulation of diverse and emerging strains underscores the need for continued molecular surveillance to monitor vaccine performance and guide future immunization strategies.

Background: We developed a Suitable Conditions Index (SCI) to predict dengue transmission in our prior work. However, the initial SCI was not refined with other important abiotic parameters. Therefore, in this study we refined the index by calculating three variants: temperature-based baseline daily average SCI (BDA-SCI), precipitation-weighted daily average SCI (PWDA-SCI), and waterbody-weighted daily average SCI (WWDA-SCI).

Methods: We used the district-wise data for two South Asian dengue-endemic countries: Bangladesh and Sri Lanka. Temperature-suitable days specific to Aedes aegypti (17.05-34.61 ℃) and Aedes albopictus (15.84-31.51 ℃) were averaged (BDA-SCI) and weighted by district-level precipitation (PWDA-SCI) and waterbody data (WWDA-SCI). We assessed the association between dengue incidence and each SCI, along with other covariates using negative binomial regression models. Furthermore, a binomial logistic regression model (BLR) was used to measure the predictive accuracy of each SCI.

Results: The BDA-SCI for Ae. aegypti was highest in Sri Lanka at 0.96 (Standard deviation [SD] 0.04, range 0.85-1.00), compared to Bangladesh 0.68 (SD 0.06, range 0.61-0.87). For Ae. aegypti, WWDA-SCI (Relative risk [RR]_aegypti = 1.06, p = 0.056, Akaike Information Criteria [AIC] 1218.6) and BDA-SCI (RR_aegypti = 1.05, p = 0.008, AIC 1214.2) had a stronger association with dengue incidence in Bangladesh than PWDA-SCI (RR_aegypti = 1.06, p = 0.056, AIC 1232.2), whereas in Sri Lanka, PWDA-SCI (RR_aegypti = 1.06, p = 0.056, AIC 472.63) performed better (AIC_BDA-SCI: 481.36, AIC_WWDA-SCI: 475.89) in the multivariable model, similar to the findings for Ae. albopictus. The BLR model predicted districts with above-median dengue incidence, and model performance indicated that BDA-SCI achieved highest accuracy for Bangladesh, while WWDA-SCI performed best for Sri Lanka, based on higher sensitivity and the Area Under the Curve value.

Conclusions: Overall, the SCI method demonstrated a practical approach for identifying dengue vector suitability and transmission risk. Refining this index with location-specific climatic and environmental variables may enhance the model accuracy and may be used for future predictions under climate change scenarios. Thus, our refined SCI will assist in creating a reliable early warning system and inform the policymakers to initiate vector control strategies, including monitoring and eliminating dengue breeding sites and implementing biocontrol strategies within hotspots.

Background: Rift Valley fever (RVF) virus and Coxiella burnetii are high-priority zoonotic pathogens posing health and economic threats in Africa. Data from Ethiopia are limited. This study estimated the prevalence and associated factors of RVF virus and C. burnetii among humans and livestock in Eastern Ethiopia using a One Health approach.

Methods: A multi-site cross-sectional study was conducted from May 1 to November 30, 2023, in the Shinile district, Somali Region, and Dire Dawa Administration. Data and blood samples were collected from 512 humans, and blood samples were collected from 1130 livestock. Sera and nucleic acids were tested using enzyme-linked immunosorbent assays (ELISA) and polymerase chain reaction (PCR), respectively. Logistic regression models were used to identify factors associated with RVF virus and C. burnetii IgG seropositivity.

Results: Apparent RVF virus IgG seroprevalence was 5.1% (26/512) in humans and 7.8% (88/1130) in livestock, while C. burnetii Phase I and II IgG seroprevalence was 30.3% (155/512) and 32.9% (372/1130), respectively. Camels showed the highest seropositivity to RVF virus IgG (17.7%; 52/294) and C. burnetii Phase I and II IgG (39.5%; 116/294). Co-seropositivity was 1.8% (9/512) in humans and 3.7% (42/1,130) in livestock. All PCR tests were negative. Rift Valley fever virus IgG seropositivity was associated with handling aborted materials (OR = 3.7; 95% CI 1.4-9.6; p = 0.007) and high mosquito abundance (OR = 4.5; 95% CI 2.0-10.1; p < 0.001). Camels had the highest odds of RVF virus IgG seropositivity (OR = 8.0, 95% CI 3.5-18.2; p < 0.001). Human C. burnetii Phase I and II IgG seropositivity was associated with female sex (OR = 2.4; 95% CI 1.6-3.6; p < 0.001), raw milk consumption (OR = 2.2; 95% CI 1.4-3.5; p < 0.001), cohabitation with animals (OR = 1.7; 95% CI 1.1-2.5; p = 0.01), and handling animal carcasses (OR = 2.3; 95% CI 1.4-3.5; p < 0.001).

Conclusions: The seroprevalence of RVF virus was low, whereas the seroprevalence of C. burnetii was high. High camel seropositivity underscores their role in pathogen transmission. One Health surveillance and targeted interventions are recommended to control the risk of future outbreaks.

Background: Giardiasis and cryptosporidiosis are often misdiagnosed by stool ova and parasite test (classical O&P). Multiplex PCR and rapid antigen immunochromatography (rapid-IC) could offer high diagnostic accuracy; however, their cost and restricted coverage, especially for parasites, limit routine use. This study evaluated the efficacy of adapted fluorescent antibody microscopy using ARK Checker® C/G-DyLight® 488 (FAM-TEST). The reagent is a liquid-form conjugated antibodies which directly detect Giardia cysts and Cryptosporidium oocysts under fluorescence microscopy.

Methods: A total of 694 stool samples submitted for microbiological examination were screened by FAM-TEST, in which specimens were mixed with DyLight-488-labeled antibodies and examined microscopically. Samples with discordant results among these methods were additionally tested by conventional PCR with Sanger sequencing to verify infection status.

Results: Diagnostic accuracy was assessed by reference to multiplex PCR results and compared with that of rapid-IC. FAM-TEST identified Giardia and/or Cryptosporidium in 35 samples. In addition, 49 FAM-TEST-negative samples from a randomly selected month were included as negative controls. For Giardia, all FAM-TEST results were identical to those of rapid-IC, including three false negatives [88.0% sensitivity, 100% specificity, 100% positive predictive value (PPV), and 95.2% negative predictive value (NPV)]. For Cryptosporidium, FAM-TEST showed 93.8% sensitivity, 100% specificity, 100% PPV, and 98.6% NPV, which were comparable with those of rapid-IC. Notably, conventional PCR for Giardia sequences produced negative results for three samples considered to yield FAM-TEST false negatives, raising another possibility of multiplex PCR false positives or extremely low pathogen burden.

Conclusion: Concurrent use of FAM-TEST with classical O&P offers a cost-effective, practical diagnostic approach for enteric parasites, which especially strengthens diagnostic accuracy for giardiasis/cryptosporidiosis.

Background: Schistosoma mansoni infection is highly prevalent in sub-Saharan Africa and is associated with significant intestinal morbidity in children. Current monitoring tools primarily assess infection status and intensity, which may underestimate the disease burden. Fecal occult blood (FOB) is a reliable indicator of bowel morbidity; however, its utility in intestinal schistosomiasis remains inadequately characterized. This study aimed to evaluate FOB as a surrogate marker of S. mansoni-induced intestinal morbidity among children in endemic areas of Kenya.

Methods: A pre-post intervention study was conducted among preschool-aged (3-5 years) and school-aged (9-14 years) children in the Mbita Health Demographic Surveillance System along the shores and islands of Lake Victoria, Suba North sub-county, western Kenya. A total of 611 children from 10 primary schools were screened for S. mansoni infection before praziquantel treatment, and 584 were re-evaluated 6 weeks post-treatment. In addition to parasitological examination for S. mansoni, FOB testing, malaria diagnosis, point-of-care hemoglobin measurement, and soil-transmitted helminth assessments were performed both before and after treatment. Associations between S. mansoni infection and FOB positivity were analyzed using Pearson's Chi-square test and logistic regression.

Results: S. mansoni infection prevalence was high before treatment, affecting 66.5% of preschool-aged and 77.4% of school-aged children. Among S. mansoni-infected children, more than three-quarters tested positive for FOB. Six weeks after praziquantel treatment, the prevalence of both S. mansoni infection and FOB positivity declined significantly (infection: 19-21%; FOB: 25-29%; P < 0.01). Before treatment, preschool-aged children residing on islands had twice the odds of FOB positivity compared to those on the mainland (AOR = 2.0; 95% CI 1.2-3.4; P = 0.01), although this association was no longer evident post-treatment.

Conclusions: Our findings demonstrate a significant association between S. mansoni infection and FOB positivity. These results suggest that FOB testing could be a useful indicator for monitoring treatment-associated reductions in intestinal morbidity due to S. mansoni in endemic settings.

This correspondence critically reflects on the recent article by Medina et al. (2025), "Pre- and post-COVID-19 pandemic identification of dengue hotspots and exploration of determinants in Quezon City." While acknowledging the study's timely contribution to understanding dengue dynamics in an urban context, the commentary identifies several key limitations. These include the absence of a clear theoretical framework, insufficient adjustment for confounding variables, reliance on a single data type without triangulation, weak translation of findings into actionable policy, and notable omissions in the literature review. Addressing these gaps in future research-through stronger theoretical grounding, rigorous methodological control, integration of multiple data sources, and closer alignment with policy and recent evidence-will enhance the scientific depth and practical relevance of dengue epidemiology.

Background: Exposure to animal and human feces in the household environment is associated with diarrheal diseases in young children. The objective of this study was to identify exposure pathways to fecal pathogens for young children that are significant contributors to diarrheal disease to allow for targeted water, sanitation, and hygiene (WASH) interventions on these pathways.

Methods: The WASHmobile Preventative Intervention for Cholera for 7 Days prospective cohort study was conducted in urban Bukavu, South Kivu province, Democratic Republic of the Congo. The cohort study of 794 children under 5 years of age included monthly diarrhea surveillance and unannounced spot checks to assess WASH behaviors and conditions over a 12-month period. Caregiver report of child mouthing of fomites was also obtained during monthly visits.

Results: The presence of animals in the child's sleeping space (odds ratio (OR): 1.87; 95% confidence interval (CI): 1.14, 3.08), unimproved sanitation (OR: 2.27; 95% CI 1.19, 4.33), and consumption of food outside the household (OR: 1.88; 95% CI 1.16, 3.06) were significantly associated with diarrhea during the subsequent month.Chickens [OR: 3.38; 95% CI: 2.05, 5.59) and cats [OR 3.9; 95% CI: 1.46, 10.46] in the child's sleeping space was also associated with significantly higher odds of diarrhea in the subsequent month.

Conclusions: These results demonstrate the need for WASH interventions targeted at reducing child contact with animal feces in the indoor household environment and improved sanitation, to reduce exposure to fecal pathogens for susceptible pediatric populations.

Background: Diagnosing COVID-19, caused by the coronavirus SARS-CoV-2, mainly involves detecting specific viral gene sequences. To effectively control highly contagious diseases, such as COVID-19, it is essential to develop quick, accurate, sensitive, and easy-to-use diagnostic methods for medical settings. The current gold standard, reverse transcription-quantitative polymerase chain reaction (RT-qPCR), requires specialized equipment and trained personnel and is typically conducted in dedicated laboratories. Loop-mediated isothermal amplification (LAMP) provides a rapid and simple alternative under isothermal conditions. In this study, we developed a colorimetric reverse transcription-loop-mediated isothermal amplification (RT-LAMP) assay for SARS-CoV-2 detection and integrated it into a microfluidic device.

Methods: RT-LAMP primers targeting conserved regions of the SARS-CoV-2 envelope (E) and RNA-dependent RNA polymerase (RdRp) genes were designed. Hydroxy naphthol blue (HNB) was used as a color indicator for visual detection. The microfluidic device, fabricated from polydimethylsiloxane (PDMS), contained five reaction chambers. RNA samples extracted from nasopharyngeal swabs of COVID-19 patients were tested using the RT-LAMP microfluidic device. Detection performance of the device was assessed using RT-qPCR as the reference standard.

Results: Among 86 RNA samples, 66 were RT-qPCR positive and 20 were negative. The RT-LAMP microfluidic device achieved 100% specificity (95% CI 83.2-100%) and an overall sensitivity of 75.8% (95% CI 63.6-85.5%) for samples with Ct ≤ 35. Sensitivity correlated with viral load, showing 100% for samples with Ct ≤ 25, 88.6% for Ct ≤ 30, and 50% for 30 < Ct ≤ 35.

Conclusions: The colorimetric RT-LAMP-based microfluidic device enables simple, rapid, and reliable detection of SARS-CoV-2 RNA with high specificity and sensitivity. The device enables visual detection of results and requires only simple equipment, making it suitable as a practical molecular detection tool for point-of-care and resource-limited settings. In terms of detection performance, our findings, when considered alongside previously published data, indicate that the sensitivity and specificity of the device are comparable to or exceed those of lateral flow tests commonly used for point-of-care COVID-19 diagnostics.

Background: Acute respiratory infection (ARI) remains the leading cause of morbidity and mortality among children under five years worldwide. However, in Ethiopia, evidence on the distribution and determinants of ARI is limited. This study aimed to assess the geographical distribution and determinants of ARI among Ethiopian children under five years.

Methods: A nationwide community-based cross-sectional study was conducted from September to December 2022. Mothers with at least one child under five years were selected using a two-stage stratified cluster sampling approach. Data were collected through face-to-face interviews using structured questionnaires. A total of 8747 mothers were included in the analysis. Multilevel logistic regression was employed to identify determinants of ARI. Four models were fitted, and the model with the lowest Deviance Information Criterion (DIC) and Akaike Information Criterion (AIC) values was selected as the best-fitting model.

Results: The 2-week prevalence of ARI among children under five was 21.3% (95% CI 20.5-22.2). The highest prevalence was observed in the Tigray region (36.1%), while the lowest was reported in Oromia (9.1%). Higher odds of ARI were observed among children aged 6-12 months (AOR = 1.6; 95% CI 1.1-2.3) and those older than 12 months (AOR = 1.5; 95% CI 1.1-2.1), children not vaccinated with PCV3 (AOR = 1.5; 95% CI 1.2-1.8), and children with diarrhea (AOR = 2.9; 95% CI 2.4-3.4) or malaria (AOR = 6.8; 95% CI 5.5-8.5). Children from households in the second (AOR = 1.3; 95% CI 1.1-1.6) and fourth (AOR = 1.3; 95% CI 1.1-1.6) wealth quintiles also had increased odds of ARI. Conversely, children living at very high altitudes had lower odds of ARI (AOR = 0.6; 95% CI 0.4-0.9). Vaccination coverage was suboptimal, with only 81.1%, 71.3%, and 64.5% of eligible children receiving PCV3, measles vaccine, and vitamin A supplementation, respectively.

Conclusion: ARI remains a major public health problem among Ethiopian children under five years, with marked regional variation in prevalence. Both individual- and household/community-level factors significantly influence ARI risk. Strengthening targeted interventions, particularly improving vaccination coverage and addressing socio-economic disparities, is essential for reducing the burden of ARI.