Zoonotic Dis., Volume 5, Issue 4 (December 2025) – 7 articles

Viral zoonoses or viral pathogens transmitted from animals to humans—constitute a rapidly intensifying global health and economic challenge. They are responsible for an estimated 2.5 billion illnesses and 2.7 million deaths annually, representing nearly 60% of all infectious diseases and 75% of newly emerging infections. Recent outbreaks, including Coronavirus disease 2019 (COVID-19), Ebola, Nipah, and avian influenza, underscore their capacity to overwhelm health systems, with COVID-19 alone projected to reduce global Gross Domestic Product by USD 22 trillion by 2025 and impose annual healthcare costs of USD 2–3 trillion. Beyond mortality and morbidity, zoonotic events disrupt trade, depress rural livelihoods, and inflict agricultural losses exceeding USD 100 billion per outbreak, with impacts disproportionately borne by low- and middle-income countries. Hotspot regions across tropical North and South America, Asia, and Central Africa remain especially vulnerable due to accelerating land use change, climate variability, and intensified wildlife–human interfaces. While the Global One Health Index highlights high regional heterogeneity, with sub-Saharan Africa scoring lowest, a critical gap persists between the conceptual strength of One Health and its operationalization in resource-limited settings. This review synthesizes evidence on drivers, clinical manifestations, and socioeconomic burdens of viral zoonoses, while highlighting novel perspectives on equity gaps, co-infection dynamics, and limitations of global preparedness initiatives. We argue that current strategies remain over-reliant on donor-driven agendas and insufficiently integrated across sectors. Addressing future zoonotic threats requires prioritizing surveillance in high-risk geographies, integrating epidemiological and economic data for preparedness planning, and supporting context sensitive One Health approaches that confront political, financial, and structural barriers to implementation. Full article

Influenza A viruses (IAVs) primarily cause respiratory illness but can also induce extrapulmonary effects, which may be aggravated by obesity. This study evaluated the impact of obesity on virus replication, histopathological changes, and cytokine/chemokine profiles in extrapulmonary sites during the acute phase, following a high-dose IAV infection. Diet-induced non-obese mice or mice with obesity were inoculated intranasally with either vehicle (medium) or 10³ TCID₅₀ of the 2009 pandemic H1N1 IAV. At 3 days post-infection (dpi), the lungs, blood, and various extrapulmonary tissues were collected for virus titration, histopathological analysis, and cytokine/chemokine quantification. IAV infection resulted in comparable virus titers (6–7 log₁₀ TCID₅₀/mL) and histopathological scores (p > 0.05 in each case) in the lungs of mice with or without obesity. Replicating viruses were not detected in the extrapulmonary sites, and histopathological scores did not differ significantly between the two groups. However, analysis of fold changes in five cytokines/chemokines (i.e., IL-6, IL-1β, TNFα, MCP-1, and IFNγ) revealed site-specific differences. IL-6 was significantly higher (p < 0.05) in the lungs and perirenal adipose tissue, and showed a higher trend in the kidney (0.05 ≤ p ≤ 0.1); IL-1β had a higher trend in the lungs; TNFα was significantly lower in the kidney but showed a higher trend in the lungs; while MCP-1 was significantly lower in the lungs, plasma, and inguinal adipose tissue of mice with obesity compared to non-obese mice. Future studies should consider a broader range of IAV strains/subtypes, doses, time points, and inflammatory markers to better understand how obesity affects extrapulmonary outcomes. Full article

The Marburg virus (MARV) is a zoonotic pathogen that causes a high case fatality rate of up to 100% in humans. In response to Marburg virus disease (MVD) outbreaks in the Kagera region, an ecological investigation was initiated to map the population and ecological threat to the reservoir host of MARV: Egyptian fruit bats. The investigation conducted from October 2023 to December 2024 included interviews with local authorities to locate all known autochthonous bat colonies in the region. Bat species confirmation was performed using high-resolution melting analysis (HRMA) and DNA barcoding, targeting two mitochondrial genes: cytochrome oxidase 1 (COI) and 16S rRNA. We found five considerably large cave-dwelling Egyptian fruit bat colonies (with approximately 100,000 individuals) at the geolocations between 1°06′04.2″ and 2°26′35.8″ S latitude and 30°40′49.7″ and 31°51′19.8″ E longitude. The study also provides the first confirmed identification of Egyptian fruit bats (Rousettus aegyptiacus) (accession numbers: PV700530-PV700534) in major bat colonies in the Kagera River Basin ecosystem. Cave-dwelling Egyptian fruit bats in mines face higher risks, and thus, attention is needed to prevent this species from becoming more vulnerable to extinction. The loss of bat roosting sites and subsequent population declines are primarily driven by the destructive practice of burning car tyres and logs, a method used to eliminate colonies through toxic smoke and heat. The collection of guano and partially eaten fruits in mining caves, as well as daily contact with Egyptian fruit bats in mines, homes, and churches, have become major potential risk factors for MARV transmission to humans. Increased threats to bats in the Kagera region warrant the implementation of conservation strategies that ensure the survival of the bat populations and inform policies on MVD risk reduction in Tanzania and the broader East African region. Full article

Background: Zoonotic fascioliasis and schistosomiasis, caused by trematode parasites transmitted by freshwater snails, are neglected tropical diseases of both medical and veterinary importance. There are critical knowledge gaps regarding the transmission dynamics of these infections in humans and animals, particularly in endemic African communities. Therefore, the current study aimed to determine the burden of human zoonotic schistosomiasis and fascioliasis among different age groups, focusing on the Lake Victoria zone and the Southern Highlands of Tanzania. Methods: A cross-sectional study was conducted among preschool-aged children, school-aged children, and adults. A total of 1557 stool and urine samples were collected, 400 from preschool children, 804 from school-aged children, and 353 from adults. Stool samples were processed using the Kato–Katz technique and the formol-ether concentration method to detect Schistosoma mansoni and Fasciola spp., respectively. Urine samples were examined for Schistosoma haematobium infection using the urine filtration method. Data were analyzed using Stata version 17. The t-tests or one-way ANOVA were used to assess statistical differences in the mean egg counts of S. mansoni and S. haematobium between exposure groups. Results: The overall prevalence of S. haematobium was 4.9%, S. mansoni was 1.2% with no significant differences across age groups, but with a statistically significant difference between sexes 1.8%. Males had a higher prevalence of both S. haematobium and S. mansoni infections compared to females. The prevalence of Fasciola infection was 0.9%, with the highest prevalence found in adults (≥18 years). Conclusions: Zoonotic schistosomiasis and fascioliasis are prevalent in the study area, affecting individuals across all age groups. This is the first study to report the presence of Fasciola infection in both the Lake Victoria zone and the Southern Highlands of Tanzania. These findings call for the Ministry of Health, through the Tanzania NTD Control Program, to recognize fascioliasis as a high-priority disease and include it in the national master plan. Full article

Brazil is the first of the 12 priority countries in Latin America with the highest number of cases of American cutaneous leishmaniasis (ACL). This study estimated the prevalence of ACL in Brazil and classified the states according to the different levels of endemicity in the period from 2014 to 2024. This is a retrospective and cross-sectional study of ACL cases registered in Brazil by the Information System for Notifiable Diseases of the Ministry of Health. The predominant cases were male (73.2%), brown (65.0%), aged between 20 and 39 (41.5%), with a low level of education (44.4%), 0.5% in pregnant women, 80% of cases were confirmed by laboratory criteria, and 90% were classified as cutaneous. A total of 182,072 autochthonous cases were recorded, with a prevalence of 89.6 cases per 100,000 population. Two states were classified as having high intense endemicity; three were classified as having medium intense endemicity; four were classified as having low intense endemicity; five states were classified as having moderate endemicity; and 13 were classified as having low endemicity. The municipality of Presidente Figueiredo, Amazonas, had the highest prevalence of ACL (5503.1%), while Belo Horizonte had the lowest prevalence (72.2%). The month with the highest average number of cases was January with 1731 (with a standard deviation of 364; upper limit of 1933; lower limit of 1572). The heterogeneity of endemicity among States suggests that social and environmental determinants influence the dynamics of ACL transmission. All sociodemographic, clinical, and epidemiological categories, when compared with the different levels of endemicity, showed significant effects (p < 0.05), except for the variable gestational status in high disease endemicity. The inclusion of these variables significantly improved the model’s ability to predict the dependent variable. Full article

Mpox has re-emerged as a global public health threat, particularly in endemic regions such as Nigeria, where human, animal, and environmental health sectors intersect. To inform surveillance and control strategies, this study assessed the knowledge, attitudes, and practices (KAP) toward Mpox among One Health stakeholders in Nigeria. A cross-sectional survey was conducted among 492 participants from human, veterinary, and environmental health sectors using a structured questionnaire. Descriptive statistics, ordinal logistic regression, and margins analysis were used to evaluate levels and predictors of KAP. Results showed that 33.7% of respondents had low knowledge, 43.5% moderate, and 22.8% high. While 62.6% demonstrated high attitude scores, only 48.2% reported moderate preventive practices. Gender was significantly associated with attitudes, with females having lower odds of expressing higher attitudes than males (OR = 0.70, 95% CI: 0.49–1.00, p = 0.052), and margins analysis revealed a predicted probability of high attitude at 56% for females and 64% for males. Multivariable modeling for practice was not pursued because model fit did not improve compared to univariable results, and sparse data led to unstable estimates, thus offering no added explanatory power. These findings underscore persistent knowledge gaps and gender-related disparities that may hinder effective Mpox response. Targeted risk communication and capacity building are recommended to strengthen One Health preparedness in Nigeria. Full article

Brucella canis is a neglected zoonotic pathogen associated with canine reproductive disorders and emerging public health concerns. This study presents the first nationwide systematic review and meta-analysis of Brucella spp. in Portugal, integrated with a 13-year retrospective seroepidemiological investigation (2013–2025) of B. canis in dogs across mainland Portugal and Insular Autonomous Regions. Among 132 canine serum samples, a seropositivity of 23.48% was observed using an immunochromatographic assay confirmed by indirect immunofluorescence (IFAT). Significant associations were identified with seasonality (p < 0.001) and breed (p = 0.001), while sex and age were not statistically significant. Municipal-level analysis revealed marked heterogeneity, with Trofa showing the highest seropositivity (58.82%) and a pooled odds ratio of 11.28 (95% CI: 2.90–43.94; p < 0.001). In parallel, meta-analyses of published data estimated a pooled seroprevalence of 2.42% in animals (95% CI: 1.79–3.13) and 10.57% in humans (95% CI: 8.80–12.47), underscoring the broader burden of Brucella spp. exposure in Portugal. These findings suggest underdiagnosis of canine brucellosis and highlight the need for enhanced surveillance in high-risk breeds and regions. The study reinforces the importance of integrated One Health strategies to improve early detection, control, and prevention of B. canis infection in both veterinary and public health contexts. Full article