Tropical Medicine and Infectious Disease

Background: The microscopic examination of stool samples remains the reference method for the diagnosis of intestinal protozoal infections; however, this technique is time consuming and requires experienced and well-trained operators. Therefore, there is a growing interest in molecular diagnostic techniques, including commercial PCR assays. The aim of this multicentric study was to evaluate a commercial real-time PCR for the detection of intestinal protozoa in fecal samples. Methods: The samples were routinely examined using conventional techniques, such as macro- and microscopic examination after concentration, Giemsa or Trichromic stain, Giardia duodenalis, Entamoeba histolytica/dispar or Cryptosporidium spp. antigens research, and amoebae culture. The samples were frozen by the participating laboratories, retrospectively extracted and examined with one-step real-time PCR multiplex using the Allplex™ GI-Parasite Assay (Seegene Inc., Seoul, Korea). Results: A total of 368 samples were analyzed from 12 Italian laboratories. Compared to traditional techniques, the sensibility and specificity of the real-time PCR kit were as follows: 100% and 100% for Entamoeba histolytica, 100% and 99.2% for Giardia duodenalis, 97.2% and 100% for Dientamoeba fragilis, and 100% and 99.7% for Cryptosporidium spp., respectively. Conclusions: The Allplex™ GI-Parasite Assay exhibited excellent performance in the detection of the most common enteric protozoa. Full article

Background: Dengue infection is a spreading vector borne disease with most severe infection-related fatalities occurring in adults. This study was conducted to explore prognostic indicators of dengue infection severity. Methods: This study included patients aged over 15 years who were diagnosed with dengue viral infection. Data were collected from nine hospitals across all regions of Thailand between January 2019 and December 2022. Diagnosis of dengue infection was confirmed by a positive result for the NS-1 antigen via RT–PCR, IgM antibody, or IgG antibody tests. Data including gender, age, BMI, underlying disease, clinical characteristics and laboratory findings were collected. Multivariable logistic regression with backward elimination was used to identify a set of prognostic factors. Results: The prognostic indicators of severe dengue were age < 55 years (OR = 6.13, p = 0.054), severe bleeding (bleeding from the gastrointestinal tract, hematemesis, melena, menorrhagia, or hematuria) (OR = 20.75, p < 0.001), pleural effusion (OR = 10.23, p < 0.001), and platelet ≤ 100,000 (/µL) (OR = 3.62, p = 0.035). These predictors were able to accurately estimate the severity of dengue infection with an area under the receiver operating curve (AuROC) of 0.836. Conclusions: The proposed four prognostic factors can be applied to predict severe dengue infections. These findings may inform the development of a risk scoring system to forecast severe dengue infection, early detection, and appropriate treatment during sickness. Full article

Cutaneous Leishmaniasis (CL) is a tropical disease endemic in many regions of Latin America. Its clinical diagnosis is often supported by histopathological analysis of skin biopsies; however, parasite detection by microscopy can be challenging, particularly in chronic or pauciparasitic lesions, leading to inconclusive results. Objective: This study aimed to evaluate the utility of polymerase chain reaction (PCR) as a confirmatory diagnostic tool for CL in formalin-fixed, paraffin-embedded (FFPE) biopsies with inconclusive histopathology. Methods: We analyzed 16 FFPE skin biopsy samples from patients with clinical suspicion of CL. All cases underwent routine histopathological evaluation using hematoxylin and eosin staining and were classified as inconclusive. DNA was extracted and PCR was performed, targeting the ITS1 and miniexon regions of Leishmania spp. Results: PCR successfully amplified Leishmania DNA in 8 (50%) out of 16 samples when both targets were utilized, confirming infection. These findings highlight the additional benefits of molecular tools in cases with inconclusive histopathology, thereby enhancing diagnostic accuracy and enabling species-level identification in certain instances. Conclusions: PCR proved to be a valuable diagnostic complement to histopathology in clinically and histologically suspected cases of CL without visible parasites. Its implementation may improve diagnostic accuracy and timely treatment in endemic areas. Full article

We analysed the socioeconomic, behavioural, and protection factors (PFs) influences on the HIV combined prevention (CP) strategy among Brazilian Amazonian men who have sex with men (MSMs). PFs are resources that reduce the effect of adversity and help people maintain their well-being. Methods: Cross-sectional study employing a convenient sample of MSMs living in the metropolitan region of Belém. A questionnaire containing socioeconomic, behavioural, PFs, and behaviour/knowledge concerning CP questions was used. “Behaviour/knowledge concerning CP” was defined as a dependent variable and received a maximum score of 16 points. The Mann–Whitney and Kruskal–Wallis tests and multiple linear regression were employed. Results: Our sample comprised 384 MSMs scoring an average of 7.83 points (±1.9). Contributing to lower scores were “not talking about sex life with confidants”, “not talking with work colleagues about personal life and sexually transmissible infections”, and “not participating in non-governmental organisations.” On the other hand, “not being happy in the neighbourhood of residency” contributed to higher scores. Conclusion: Peer support and social inclusion are essential for increasing MSMs’ access to CP. Full article

The accurate identification of mosquito species is critical for effective mosquito surveillance and control, especially when presented with morphologically similar species like Aedes aegypti and Aedes sierrensis. Damaged specimens and morphologically similar life stages such as eggs and larvae make it difficult to distinguish Aedes aegypti from Aedes sierrensis using microscopy and taxonomic keys. To address this, the AegySierr.ID-qPCR assay, a multiplex quantitative PCR assay that utilizes single-nucleotide polymorphisms within the mitochondrial cytochrome oxidase subunit I gene, was developed to distinguish between these two species. The assay was tested on DNA extracted from the eggs, larvae, and adults of both species, as well as from environmental DNA (eDNA) collected from natural mosquito reproduction sites. It demonstrated a high diagnostic accuracy across multiple life stages, with a sensitivity exceeding 95% for most groups and specificity exceeding 90%, except for field-collected adult Ae. sierrensis (75%). For eDNA samples, the assay achieved 100% sensitivity and 94% specificity for samples classified as Ae. sierrensis and 91% sensitivity and 86% specificity for Ae. aegypti. A two-graph receiver operating characteristic analysis was also used as an alternate method with which to establish Ct thresholds for interpreting results from unknown samples. The AegySierr.ID-qPCR assay enables the rapid and sensitive identification of Ae. aegypti and Ae. sierrensis from specimens and eDNA, and may be of use in mosquito surveillance programs. Full article

The genus Orthoflavivirus includes several mosquito-borne pathogenic viruses, notably West Nile virus (WNV), which is endemic to the Mediterranean region. In Portugal, WNV circulation has been documented in equines, birds and mosquitoes, however human cases remain rare and no recent human seroprevalence studies have been conducted. This study aimed to estimate the national and regional seroprevalence of WNV among blood donors in mainland Portugal and explore associations with sociodemographic factors. A cross-sectional study conducted in 2022 included 3593 blood donors from across mainland Portugal. Serum samples were tested for WNV immunoglobulin G (IgG) by enzyme-linked immunosorbent assay (ELISA) and positive and borderline samples were confirmed using a virus neutralization test. Sociodemographic data were collected through a structured paper questionnaire. Statistical analyses, including multivariate logistic regression, identified factors associated with seropositivity. A total of 55 samples (1.5%) tested positive, and 21 samples (0.6%) were classified as borderline for WNV antibodies by ELISA. Of these, 47 were confirmed by viral neutralization, giving an estimated national seroprevalence of 1.4%. Significant regional variation was noted, with higher seroprevalence observed in the Beira Baixa, Grande Lisboa and Médio Tejo regions. Some seropositive individuals were identified in northern coastal regions such as Ave, Cávado and Área Metropolitana do Porto. In multivariate analysis, geographical area of residence was the only factor associated with seropositivity. This study highlights regions at potential higher risk for human WNV exposure, primarily in the southern half of Portugal. Continued and integrated surveillance is crucial to inform public health strategies to mitigate WNV transmission risks in these regions, as well as in other regions where WNV may be emerging as a relevant One Health concern. Implementing preventive measures for both animals and humans is critical to minimizing exposure and infection, and further confirmatory studies using virus neutralization tests will be important for refining these estimates. Full article

The World Health Organization (WHO) declared snakebite envenoming (SBE) as a neglected tropical disease in 2017. Antivenom is the gold standard of treatment, but many healthcare barriers exist, and hence, affected populations are often unable to access it. The challenge is further perpetuated by the lack of attention from national health authorities, poor regulatory systems and policies, and mismanagement of antivenom. This study aims to map the evidence regarding snake antivenom regulations globally and identify gaps in the literature to inform future research and policy. This review was conducted using the original Arksey and O’Malley framework by three independent reviewers, and the results were reported using the Preferred Reporting Items for Systematic reviews and Meta-Analysis Extension for Scoping Reviews (PRISMA-ScR). A search strategy was developed with assistance from a librarian, and six databases were searched: PubMed, SCOPUS, ProQuest Central, Africa Wide Web, Academic Search Output, and Web of Science. Screening was conducted independently by the reviewers, using Rayyan, and conflicts were resolved with discussions. A total of 84 articles were included for data extraction. The major themes that emerged from the included studies were regarding antivenom availability, accessibility, manufacturing, and regulations. The study revealed massive gaps in terms of policies governing antivenom management, especially in Asia and Africa. The literature does not offer sufficient evidence on management guidelines for antivenom in the endemic regions, despite identifying the challenges in supply. However, significant information from Latin America revealed self-sufficient production, involvement of national health bodies in establishing efficient regulations, effective distribution nationally and regionally, and technology sharing to reduce SBE-related mortality. Full article

Human brucellosis is a zoonotic, bacterial infection caused by the intracellular, Gram-negative Brucella spp., which is common globally but rare in the United Kingdom, with approximately 20 imported cases per annum following travel to countries with high endemicity. Transmission typically occurs via the ingestion of infected animal products, including unpasteurised dairy products. Human-to-human transmission is rare, and routes include postpartum vertical transmission through breastfeeding. We report here on a familial cluster of three cases within a single UK-based Kurdish household of four, including a 11-month-old infant infected through the consumption of breast milk. Four months prior to presentation, the family had travelled together to northern Iraq for a 5-week holiday and all consumed local dairy products except for the children, including the 11-month-old, who was exclusively breastfed at the time. All three patients, including one adult male with complicated brucellosis, had a favourable outcome with medical therapy.: Brucellosis is an important differential diagnosis in returning travellers and specialist advice should be obtained early to prevent sequelae. It is also important for active case-finding, especially in family units with shared exposure. Paediatricians and adult physicians who may manage brucellosis should consider the possibility of vertical transmission in breastfeeding mothers. Full article

Adherence to the 6-month tuberculosis (TB) treatment regimen is challenging due to its duration and side effects, with various factors influencing patient compliance. A retrospective cross-sectional study was conducted among newly diagnosed pulmonary TB (pTB) patients in Selangor, Malaysia, undergoing treatment in government primary care clinics and hospitals. Patients who were lost to follow-up (LTFU) within the first six months were determined by reviewing patient records and the national TB registry. Logistic regression analysis identified sociodemographic and clinical factors associated with LTFU. Of the 699 pTB patients, 55 (7.9%) were lost to follow-up. Factors significantly associated with LTFU included age (higher in 25–44-year-olds, adjusted odds ratio (aOR): 2.83), unmarried status (aOR: 2.17), lower education level (aOR: 6.13), being a smoker (aOR: 2.65), and unawareness of TB diagnosis (aOR: 38.14). A significant interaction was found between education level and awareness of diagnosis, with unawareness having a stronger association with LTFU among higher-educated patients. Young adults, those with a lower education level, unmarried individuals, smokers, and those unaware of their TB diagnosis are at higher risk of LTFU. These factors can be used for rapid risk assessment. Intensive counselling and health education at treatment initiation, particularly for at-risk patients, are crucial for preventing LTFU. Full article

A review was conducted on snakebites in Central America. Information was extracted using the databases of PubMed, SciELO, and LILACS. Information included retrospective studies, case reports, and case series; in this way, valuable information was retrieved from limited sources. The identified studies comprised those discussing envenoming snakebites. Several species were identified, but three of them had major epidemiological features impacting envenoming by snakebites: Bothrops asper, Crotalus simus, and Micrurus sp. Adolescents and young adult males living in rural areas and engaged in agricultural activities were identified as the main victims of snakebites by clinical records. Symptoms of local damage in the bite sites included edema and skin and muscle necrosis. In addition, the cardiovascular system was affected, with symptoms like hypotension, bleeding, and coagulation disorders. Neurotoxicity causing sensitivity and motricity problems was also reported. For El Salvador, accidents caused by Crotalus simus and Micrurus spp. were given more attention due to their greater relevance. The role of Bothrops species was more relevant in the envenoming reported by other countries. Treatment was found to be provided based on antivenoms produced in Costa Rica, and the recovery of the patients depended on the time elapsed between the accident and the initial treatment in the healthcare system. Full article

Research is required to determine whether the coinfections by Fasciola spp. and other parasite species result from poor rural hygiene or reflect underlying epidemiological patterns and causes. Therefore, the role of fascioliasis is analyzed concerning coinfection complexity, risk of multiparasitism, parasite associations, pathogenic implications and their multifactorial causes. Helminth and protozoan coinfections are studied in 2575 previously untreated individuals from four rural hyperendemic areas (Northern Bolivian Altiplano, Peruvian Altiplano and Cajamarca valley, and the Egyptian Nile Delta). This cross-sectional study was conducted from January 2011 to December 2023. Coinfections were coprologically assessed by the merthiolate–iodine–formalin and formol–ether concentration techniques. Infection intensity was measured as eggs/gram of feces (epg) with the Kato–Katz technique. Parasite and coinfection prevalences were stratified by age, sex and geographical location. High mixed infections, fascioliasis prevalences and very low non-coinfected Fasciola-infected subjects were associated with the following regions: Bolivian Altiplano, 96.5%, 16.8% and 3.5%; Peruvian Altiplano, 100%, 24.6% and 0%; Cajamarca valley, 98.7%, 21.4% and 1.8%; Nile Delta, 84.1%, 13.0% and 15.9%. Transmission routes and human infection sources underlie fascioliasis associations with protozoan and other helminth infections. Prevalence pattern of protozoan–helminth coinfections differed between Fasciola-infected individuals and individuals not infected with Fasciola, presenting higher prevalences in individuals with fascioliasis. Multiparasitism diagnosed in Fasciola-infected subjects included coinfections by up to nine parasite species, eight protozoan species, and five helminth species. The most prevalent pathogenic protozoan was Giardia intestinalis. The most prevalent helminth species differ according to environmental conditions. Several parasites indicate fecal environmental contamination. When the fascioliasis burden increases, the total number of parasite species also increases. The fascioliasis risk increases when the total helminth species number/host increases. Fasciola-infected subjects may present a modification in the clinical phenotypes of coinfecting parasitic diseases. Fascioliasis coinfection factors include transmission ways and immunological, environmental and social aspects. Coinfections must be considered when assessing the health impact of fascioliasis, including the analysis of the fascioliasis effects on malnutrition and physical/intellectual child development. Fascioliasis-control schemes should, therefore, integrate control measures mainly against other helminthiases. Full article

Respiratory syncytial virus (RSV) is a major cause of morbidity and mortality from lower respiratory infections (LRIs) worldwide. This study analyzes trends in age-standardized death rates (ASDRs) and disability-adjusted life years (DALYs) due to RSV-induced LRIs from 1990 to 2019, using data from the Global Burden of Disease Study 2021 (GBD 2021). The findings show a gradual decline in deaths, ASDR, and DALYs throughout this period. However, these indicators were higher in men than in women, as well as more pronounced in sub-Saharan West Africa. Developed countries exhibited higher ASDR and DALY values than developing countries, with the highest burden observed among children and the elderly in low Socio-demographic Index (SDI) regions. Globally, RSV-induced LRIs have shown a significant reduction in burden, but interventions are still urgently needed—particularly in low SDI areas—to reduce the impact on vulnerable populations. Public health policies focusing on these high-risk groups are essential for addressing the remaining disparities in RSV-related morbidity and mortality. Full article

Rabies remains a significant global public health concern, causing an estimated 59,000–69,000 human fatalities annually. Despite being entirely preventable through vaccination, rabies continues to impose substantial economic burdens worldwide. This study presents a scoping review of the economic research on rabies to determine overlaps and gaps in knowledge and inform future research strategies. We selected 150 studies (1973–2024) to analyze. The review categorizes the literature based on geographic distribution, species focus, and type of study. Findings indicate that economic studies are disproportionately concentrated in developed countries, such as the United States and parts of Europe, where rabies risk is low, while high-risk regions, particularly in Africa and Asia, remain underrepresented. Most studies focus on dog-mediated rabies, reflecting its dominant role in human transmission, while fewer studies assess the economic impacts of wildlife and livestock-mediated rabies. Case studies and modeling approaches dominate the literature, whereas cost–benefit and cost–effectiveness analyses—critical for informing resource allocation—are limited. The review highlights the need for more economic evaluations in rabies-endemic regions, expanded research on non-dog reservoirs, and broader use of economic methods. Addressing these gaps will be crucial for optimizing rabies control and supporting global initiatives to eliminate dog-mediated rabies by 2030. Full article

Triclabendazole (TCBZ) is the gold standard treatment for fascioliasis. However, reports on resistance are increasing, emphasizing the need for alternative therapy. Combining TCBZ with ivermectin (IVM) was found to be effective for treating animal fascioliasis. Building on this, we aimed to evaluate the efficacy of the TCBZ/IVM combination therapy for human fascioliasis. This study enrolled 136 patients with Fasciola from Upper Egypt, and they were divided into the first group (n = 65), who received TCBZ monotherapy, and the second group (n = 71), who received the TCBZ/IVM combination. Assessments were to evaluate treatment response based on clinical, eosinophilic, and radiological parameters. Chronic fasciolosis was diagnosed in 17 patients (12.5%). No differences were observed in age and sex. Significant improvements were noted in all parameters in both groups, with more pronounced effects observed in the second group. A significantly higher complete response, including clinical, eosinophilic, and radiological improvements, was reported in the combined therapy group, with 53.3% compared to 26.2% in the monotherapy group (p < 0.001). A high baseline eosinophilic count was significantly associated with response. The efficacy of the TCBZ/IVM combination for treating human fascioliasis suggested a possible boosting effect, which can benefit regions of TCBZ failure. Further large-scale randomized studies are warranted to confirm these findings. Full article

Via a One Health approach, this study concomitantly assessed the susceptibility of humans and dogs to Trypanosoma cruzi infections on three islands and in two mainland seashore areas of southern Brazil. Human serum samples were tested using an enzyme-linked immunosorbent assay (ELISA) to detect anti-T. cruzi antibodies, while dog serum samples were tested using indirect fluorescent antibodies in an immunofluorescence assay (IFA). Seropositive human and dog individuals were also tested using quantitative polymerase chain reaction (qPCR) in corresponding blood samples. Overall, 2/304 (0.6%) human and 1/292 dog samples tested seropositive for T. cruzi by ELISA and IFA, respectively, and these cases were also molecularly positive for T. cruzi by qPCR. Although a relatively low positivity rate was observed herein, these cases were likely autochthonous, and the individuals may have been infected as a consequence of isolated events of disturbance in the natural peridomicile areas nearby. Such a disturbance could come in the form of a fire or deforestation event, which can cause stress and parasitemia in wild reservoirs and, consequently, lead to positive triatomines. In conclusion, T. cruzi monitoring should always be conducted in suspicious areas to ensure a Chagas disease-free status over time. Further studies should also consider entomological and wildlife surveillance to fully capture the transmission and spread of T. cruzi on islands and in seashore mainland areas of Brazil and other endemic countries. Full article

Insecticide resistance monitoring is essential for effective mosquito control. This study compared CDC Bottle Bioassays (BBAs) using technical and formulated insecticides (deltamethrin/Deltagard and malathion/Fyfanon EW) against the Culex pipiens complex (Fogg Rd) and Culex tarsalis Coquillett (Vic Fazio). BBAs indicated resistance to deltamethrin and emerging resistance to malathion in Fogg Rd, as well as resistance to both in Vic Fazio. Field trials, however, showed high efficacy: Deltagard caused 97.7% mortality in Fogg Rd and 99.4% in Vic Fazio. Fyfanon EW produced 100% mortality in Fogg Rd but only 47% in Vic Fazio. Extended BBA endpoints at 120 and 180 min aligned better with field outcomes. Deltagard achieved 100% mortality at 120 min in both populations; technical deltamethrin reached 85.7% (Fogg Rd) and 83.5% (Vic Fazio) at 180 min. Fyfanon EW and malathion showed similar performance: 100% mortality was achieved in Fogg Rd by 120 min but was lower in Vic Fazio; malathion reached 55%; and Fyfanon EW reached 58.6% by 180 min. Statistical analysis confirmed that BBAs using formulated products better reflected field performance, particularly when proprietary ingredients were involved. These findings support the use of formulated products and extended observation times in BBAs to improve operational relevance and resistance interpretation in addition to detecting levels of insecticide resistance. Full article

Background: Polyparasitic infections remain widespread in endemic regions, yet its contributing factors and health impact are not well understood. This study aims to estimate the prevalence and associated factors and examines the effect of polyparasitic infection on haemoglobin levels among children. Methods: A cross-sectional study was conducted in Lambaréné, Gabon, among children aged 2–17 years from November 2019 to December 2020. Haemoglobin levels, environmental conditions, and sociodemographic data were collected. Stool, urine, and blood samples were analysed using light microscopy for parasite detection. Factors associated with polyparasitism were explored. Results: Out of 656 participants, 65.4% had at least one infection, with intestinal protozoa species (21.3%), Trichuris trichiura (33%), Ascaris lumbricoides (22%), Schistosoma haematobium (20%), and Plasmodium falciparum (10%) being the most common. Polyparasitic infection was identified in 26% of children, mostly as bi-infections (69.2%), and was negatively associated with haemoglobin levels (β = −0.06). Conclusions: These findings emphasise the burden of polyparasitic infections and adverse health effects in Lambaréné, Gabon. Full article

Background: Dyslipidemia and schistosomiasis are major public health challenges, particularly in endemic regions where their coexistence may influence host metabolism and immune responses. This study aimed to evaluate visceral adipose tissue (AT) remodeling in a murine model of acute Schistosoma mansoni infection combined with diet-induced dyslipidemia. Methodology: Female Swiss Webster mice were fed either a standard or high-fat diet (HFD) for 29 weeks and infected with S. mansoni at week 20. Nine weeks after infection, biochemical, morphometric, histopathological, and immunological analyses were performed. Results: The HFD promoted weight gain and dyslipidemia, while S. mansoni infection alone did not alter lipid profiles but partially mitigated the metabolic effects of the HFD. Morphometric analysis revealed adipocyte hypertrophy and reduced cell number in HFD-fed animals. In HFD-fed infected mice, infection partially reversed hypertrophy, suggesting a modulatory effect on AT remodeling. Histopathological examinations showed that while a HFD induced mild inflammation, infection led to intense leukocyte infiltration, hyperemia, and plasma cell degeneration. Peritoneal lavage confirmed a proinflammatory immune profile. Conclusions: These findings indicate that the interaction between a HFD and S. mansoni infection exacerbates adipose tissue inflammation and metabolic alterations, highlighting the complex interplay between parasitic infection, diet, and immune-metabolic regulation. Full article

Objective: To characterize the profiles of resistance mutations to HIV reverse transcriptase inhibitors in Gabon. Design: Cross-sectional study conducted over 37 months, from October 2019 to October 2022, at the IST/HIV/AIDS Reference Laboratory, a reference center for the biological monitoring of people living with the human immunodeficiency virus (PWHIV) in Gabon. Methods: Plasma from 666 PWHIV receiving antiretroviral treatment was collected, followed by RNA extraction, amplification, and reverse transcriptase gene sequencing. Statistical analyses were performed using Stata^® 14.0 software (USA). Results: Six hundred and sixty-six (666) PWHIV plasma collected from 252 male and 414 female patients were analyzed and 1654 mutations were detected in 388 patients, including 849 (51.3%) associated with nucleoside reverse transcriptase inhibitors (NRTIs) and 805 (48.7%) with non-nucleoside reverse transcriptase inhibitors (NNRTIs). Three of the most prescribed treatment regimens were associated to the appearance of both NRTIs and NNRTIs resistance mutations: TDF + 3TC + EFV (24.02%; 160/666); TDF + FTC + EFV) (17.2%; 114/666) and AZT + 3TC + EFV (14.6%; 97/666). Additionally, stage 3 of CD4 T-lymphocyte deficiency, the higher viral load, and treatment duration are risk factors influencing the appearance of virus mutations. Also, treatment containing TDF-3TC + DTG is more protective against mutations. Conclusions: Drug resistance mutations are common in Gabon and compromise the efficacy of ART. Further study must search for other causes of therapeutic failure in Gabon in PWHIV. Full article