American Journal of Tropical Medicine and Hygiene最新文献

The authors of studies in high-malaria transmission areas have associated the opsonic phagocytosis (OP) of merozoites with protection from clinical malaria; however, OP studies have not been conducted in low transmission areas. In the current study, blood samples were collected from 5,753 individuals in a Kenyan highland area of low, unstable transmission in 2007 and monitored for clinical malaria through 2017. In a nested case-control design, individuals who developed clinical malaria (cases, N = 317) were matched 1:1 by age and village with those who did not (controls, N = 317). A novel OP assay was developed, and the association of OP with the risk of clinical malaria and IgG responses to Plasmodium falciparum antigens in individuals <5 years old, 5-14 years old, and ≥15 years old was examined. Opsonic phagocytosis levels increased with age; however, the proportion of individuals who tested positive for an OP response was <50% until individuals were ≥15 years old. After adjustment for potential confounding factors, OP levels were associated with an increased risk of clinical malaria in individuals 5-14 years old (adjusted odds ratio: 3.32 [CI: 1.13-9.77]) and ≥15 years old (adjusted odds ratio: 4.85 [CI: 1.02-23.00]), but not in children <5 years old (adjusted odds ratio: 0.57 [CI: 0.20-1.64]). In this low-malaria transmission area, OP responses did not develop in most individuals until they were ≥15 years old, and OP levels in individuals ≥5 years old were associated with an increased risk of clinical malaria, potentially reflecting that OP levels are markers of malaria exposure, providing additional information beyond standard geographic and intervention-based risk markers.

Climate change is anticipated to significantly affect malaria transmission. Previous research has shown lagged, nonlinear associations between climate variables and malaria risk, with highly context-specific exposure-lag-response relationship. Using weekly malaria case data collected between July 2018 and February 2023 from a health facility within the Iganga-Mayuge Health and Demographic Surveillance System site in Uganda and remotely sensed temperature and rainfall data, we quantified the associations between temperature and rainfall and risk of developing symptomatic malaria using a distributed lag nonlinear model. Furthermore, we investigated whether these associations varied by age group. Our analysis revealed a lag of 2 to 8 weeks between exposure to rainfall exceeding 200 mm/week and a significant increase in the risk of developing symptomatic malaria; no statistically significant lagged association was found with temperature. Additionally, the risk in school-aged children was less sensitive to climate variables compared with the other age groups. Rainfall was found to be associated with an increased risk at a lag of 2 months at the study site. This finding provides valuable guidance for local health authorities in determining the optimal timing for preventive interventions and in preparing for the anticipated rise in demand for malaria case management. The observed variations in the risk of developing symptomatic malaria across different age groups highlight the need for targeted interventions tailored to specific populations. Overall, the significant associations between climate variables and malaria risk underscore the importance of context-specific, adaptive malaria control strategies, complemented by broader efforts to mitigate climate change.

Sickle cell trait carriers are generally considered asymptomatic; nevertheless, there are potential complications. The spleen is vulnerable to infarction because of its role in trapping and removing sickle cells and its hypoxic environment. In this report, a case of a 31-year-old physically active man who experienced severe abdominal pain near the peak of the Acatenango Volcano in Guatemala is described. At the hospital, he was diagnosed with splenic infarction, requiring splenectomy. Pathological analysis of the spleen revealed interstitial hemorrhage and marked congestion of capillaries by sickle-shaped erythrocytes. Laboratory studies revealed no evidence of anemia or any alteration in the red blood cell formula; however, leukocytosis was observed at the time of the event, which rapidly decreased on subsequent days. In contrast, platelets increased after the spleen removal. Capillary electrophoresis revealed the sickle cell carrier state. Genetic alterations associated with thrombophilia, alpha thalassemia, and other beta globin hemoglobinopathies were absent. This case reinforces evidence that high-altitude hypoxia can trigger sickle cell formation in heterozygous carriers and lead to splenic damage.

Dengue is the most prevalent arboviral disease worldwide. This study aimed to describe the epidemiological and economic burden of dengue in Mexico by identifying comorbidities and conditions associated with clinical outcomes. A retrospective analysis of dengue epidemiological data in Mexico from 2010 to 2020 was conducted using surveillance system databases (Sistema Nacional de Vigilancia Epidemiológica and Sistema Único de Información para la Vigilancia Epidemiológica). Data on probable, laboratory-confirmed, outpatient, and hospitalized cases as well as deaths were collected along with comorbidities and pregnancy status; a survey was conducted to gather information on health care resources utilization. Sistema Nacional de Vigilancia Epidemiológica recorded 1,620,872 cases, among which there were 336,991 laboratory-confirmed cases, 110,437 hospitalizations, and 1,385 deaths. The hospitalization fatality rate increased from 0.72% to 2.6%. Age distribution of severe dengue shifted from predominantly affecting individuals 10-24 years old (2010-2016) to those 0-19 years old (2017-2020). These findings highlight the need for age-specific health care interventions. Comorbidities, such as diabetes, liver cirrhosis, hypertension, kidney disease, and hematological disorders, and pregnancy were significantly associated with an increased risk of hospitalization and mortality. Additionally, peptic ulcer was associated with a higher risk of hospitalization. The estimated annual medical cost during outbreak was U.S. $111,851,376 (2019, 211.0 [case] incidence) in contrast to pre-/postoutbreak, with total costs of U.S. $23,713,589 (2018, 62.4 [case] incidence) and U.S. $39,780,809 (2020, 94.1 [case] incidence), respectively. The robustness of collected data contributes to more comprehensive understanding of the public health implications of dengue, particularly during outbreaks.

Chromobacterium violaceum is a Gram-negative bacillus found in soil and water in tropical and subtropical areas. Although usually nonpathogenic, it can cause severe infections in humans. Case series and literature reviews remain rare. In this study, we identified 26 cases that have occurred in French overseas territories (FOTs) since 1999 and reviewed 57 cases published over the past 20 years. The portal of entry was cutaneous for 53% of our patients and 38% of published cases, followed by pulmonary, digestive, mucosal, and urinary. None of our patients were immunocompromised. Nine of our patients were hospitalized in intensive care, including five deaths (19%). In the case review, 26 patients died (46%), four of whom were immunocompromised. Most of the strains were sensitive to ciprofloxacin (FOT 100%, review 98%), cotrimoxazole (FOT 95%, review 94%), and imipenem (FOT 84%, review 92%).

Dengue fever is a common arboviral illness that can result in severe hemorrhagic complications, although spontaneous intraperitoneal bleeding remains rare. We report the case of a 26-year-old previously healthy female who presented with a 4-day history of high-grade fever and myalgia that was later diagnosed as dengue fever. During hospitalization, she developed vaginal bleeding followed by generalized abdominal pain and shock. Contrast-enhanced computed tomography revealed significant hemoperitoneum, despite a normal coagulation profile and no identifiable bleeding source. She was managed conservatively with supportive care and made a full recovery. A 1-year follow-up was unremarkable. This case underscores the importance of early recognition, prompt imaging, and consideration of differential diagnoses. In the absence of established guidelines for managing spontaneous intraperitoneal hemorrhage in dengue, individualized conservative treatment may be effective. Clinicians should remain vigilant for atypical presentations to ensure timely diagnosis and appropriate management.

This systematic review examines the multifaceted roles of γδ T cells in malaria and tuberculosis (TB) with an emphasis on subset-specific dynamics and functional plasticity. In malaria, γδ T cells, particularly Vγ9Vδ2+ cells, are rapidly activated upon infection with Plasmodium falciparum, exerting antiparasitic effects through the production of proinflammatory cytokines, cytotoxicity, and immune modulation. However, chronic or repeated exposure to malaria leads to the functional exhaustion of Vδ2+ cells, which is characterized by reduced cytokine responsiveness and a shift toward regulatory phenotypes. In TB, γδ T cells contribute to pathogen containment through the secretion of interferon-γ and interleukin-17, the activation of macrophages, and the formation of granulomas. Yet, active TB is often associated with reduced peripheral γδ T-cell frequencies, possibly because of tissue migration or exhaustion. Emerging evidence also highlights distinct roles for CD8+ γδ T cells and Vδ1+ subsets in latent infection and local tissue immunity. Understanding the pathogen-specific and context-dependent functions of γδ T-cell subsets is critical for informing the development of targeted immunotherapies and vaccine strategies against malaria and TB.

Echinococcosis is a zoonotic disease with global public health implications. However, its prevalence in Southeast Asia, including Myanmar, remains poorly documented. In this article, a case of human cystic echinococcosis caused by Echinococcus ortleppi (E. ortleppi) is reported in a 21-year-old man from Myanmar, who had traveled to Japan for vocational training. He presented to the study hospital in Tokyo after a chest radiograph revealed the presence of a giant cyst shadow in the right middle and lower lung fields. The cysts were excised, and echinococcosis was diagnosed on the basis of the pathological findings. Sequencing of a 150 base pair fragment of the mitochondrial cytochrome c oxidase subunit 1 gene in a section of cyst tissue was consistent with E. ortleppi. To the best of the authors' knowledge, this is the first documented case of human echinococcosis in Myanmar.

Accurate Leishmania species identification is crucial for epidemiological aspects and disease management. This study aimed to detect and identify the main causative species of human cutaneous and visceral leishmaniasis in Iran using nested polymerase chain reaction (PCR) based on size polymorphism of the ribosomal DNA (rDNA) intergenic region. In total, 180 clinical samples, including 156 confirmed positive cases, 24 confirmed negative cases, and 33 suspected cases that tested negative by microscopy, were collected from skin lesions, bone marrow, and lymph nodes across five provinces in Iran. DNA was extracted from the samples, and the nested PCR-amplified fragments were differentiated with agarose gel electrophoresis. The nested PCR assay successfully identified Leishmania major, Leishmania tropica, and Leishmania infantum with high accuracy. Among 156 microscopy-positive samples, L. major was detected in 84 cases, L. tropica was detected in 64 cases, and L. infantum was detected in 8 cases. The results obtained were fully consistent with those from a commercial real-time PCR diagnostic kit. Phylogenetic analysis supported the differentiation of Leishmania species. However, among 33 suspected cases, 14 samples were negative by all three methods (microscopy, commercial PCR kit, and nested PCR), 7 samples tested positive by both molecular methods, 8 samples were positive only with the commercial PCR kit, and 4 samples were positive exclusively by nested PCR. The findings indicate that the nested PCR assay targeting size polymorphisms in the rDNA region is a cost-effective method for detection and identification of Leishmania species in clinical specimens, particularly when microscopy results are inconclusive.

The anatomical and immunological similarities between humans and nonhuman primates (NHPs) make NHPs a viable model for examining Plasmodium spp. infection outcomes. Plasmodium fragile was previously used to model human severe malaria in NHPs using rhesus macaques (RMs), but a thorough investigation of the clinical and pathological effects of RM P. fragile infection has not yet been conducted. In this study, we observed that experimental infection of a male RM with P. fragile-infected erythrocytes resulted in clinical signs of malaria, including anemia; changes in red and white blood cell distribution; changes in red blood cell morphology; and gross and histopathological alterations to vital organs, such as the liver, lungs, heart, and brain. Plasmodium fragile-infected red blood cells were also observed in the vasculature of major organs, including the spleen, liver, lung, and brain. These results suggest that experimental P. fragile infection of RMs is a translatable model of human malaria.