Equine Infectious Anemia Virus (EIAV), the causative agent of Equine Infectious Anemia (EIA), presents a significant threat to equine populations worldwide. While local EIAV prevalence has been estimated in several studies, no global prevalence has been determined. Thus, this study aimed to review the literature on EIAV prevalence in the 21st century. A comprehensive electronic search was conducted in PubMed, Web of Science, Scopus, Google Scholar, SciELO.org, African Journals Online, and NZresearch.org, yielding 105 articles published between January 1st, 2000, and December 31st, 2024 (spanning 24 years). EIAV prevalence was estimated in 42 countries and is particularly high in Mexico (North America; 27.14 % [95 % CI, 25.11 - 29.17]) and Guatemala (Central America; 15.9 % [95 % CI, 9.66 - 22.14]). While EIAV prevalence in the United States of America (USA) remains low and stable over time, the relatively elevated prevalence in the Southern states, along with their extensive border with Mexico, places these areas at a higher risk. EIAV prevalence estimated per province/state in the USA, Argentina, and Brazil, indicated higher rates in humid and warmer regions. EIAV has a low presence in the Middle East, while the scarcity of epidemiological studies in Africa and Oceania complicates the estimation of EIAV prevalence in these regions. These findings highlight the need for continued intensive surveillance in both high-risk regions and areas lacking data. Given that insect vectors are the primary natural transmission route, global warming may lead to increased vector movement into temperate areas, potentially contributing to a surge in EIAV infections.

Western equine encephalitis virus (WEEV) is a mosquito-borne arbovirus (genus Alphavirus, family Togaviridae) that has re-emerged in South America in late 2023, causing severe disease in both horses and humans after a nearly 40-year intermission period. We here describe the virological, serological, pathological, and molecular features of WEEV infection in horses during the 2023–2024 outbreak in Argentina. WEEV-infected horses developed neurological signs with mild to severe encephalitis associated with minimal to abundant WEEV-infected cells, as demonstrated by WEEV-specific in situ hybridization. The distribution of viral RNA was multifocal, with predominance within neuronal bodies, neuronal processes, and glial cells in the medulla oblongata and thalamic regions. Phylogenetic analysis of partial nsP4 sequences from three viral isolates obtained from three different provinces of Argentina support grouping with other temporally current WEEV strains from Uruguay and Brazil under a recently proposed novel lineage.

Group A rotavirus (RVA) infections are a leading cause of neonatal diarrhoea in foals. Neonatal mice could serve as a useful tool to study the pathogenesis of equine RVA (ERVA) as well as a preclinical model for assessment of vaccine efficacy. This study aimed to comparatively evaluate the clinical, virological and pathological features of ERVA G3P[12] and G14P[12] infection in neonatal mice and compare them with porcine OSU G5P[7] and bovine UK G6P[5] RVA reference strains. Neonatal mice orally inoculated with equine, bovine and porcine RVA developed short-lived diarrhoea at variable rates, G14P[12] (61%) and G3P[12] (88%). Viral replication kinetics for all strains were characterized by a gradual decline in viral load to levels below the limit of detection by 72–96 h post-infection (hpi), in line with the reduction in the number of infected enterocytes demonstrated via RNAscope^® in situ hybridization. Importantly, the clinical and viral replication kinetics correlated with significant microscopic intestinal alterations characterized by enterocyte vacuolation, scalloping and hyperplasia with a peak occurring at 48 hpi and persisting until at least 96 hpi. Overall, neonatal mice develop a disease phenotype of short duration following infection with equine, porcine and bovine RVA strains characterized by diarrhoea and pronounced histological alterations in the intestinal villi. The limited intestinal viral replication is likely associated with host restriction. The clinical and pathological phenotypes developed by neonatal mice following experimental infection could serve as a preclinical tool to assess vaccine efficacy and for pathogenesis studies involving RVA of equine, porcine and bovine origin.

Bovine viral diarrhea virus (BVDV) is a pathogen of worldwide economic importance. In Uruguay, BVDV is endemic, with seroprevalence >80% at the farm level. This study analyzed 912 samples collected from January 2018 to October 2024 by reverse transcription PCR and sequencing, from calves with diarrhea, aborted fetuses, heifers with a history of abortions, and animals exhibiting symptoms of Mucosal Disease. This work summarizes ten years (2014–2024) of molecular epidemiology and evolution of BVDV. Analysis of the BVDV 5′UTR/N^pro genomic region revealed that the BVDV-1a, 1e, 1i, and 2b subtypes circulate in Uruguay. BVDV-1a remains the most prevalent subtype, followed by BVDV-2b, whose prevalence has been increasing. Our previous studies revealed that BVDV-1a showed geographical diversification in Uruguay. In this work, evolutionary studies conducted with N^pro genomic region showed that BVDV-2b is evolving at a substitution rate of 6.09 × 10⁻⁴ substitutions/site/year and has been introduced from Brazil in six separate events between 1870 and 1928, showing no geographical diversification. This work demonstrates that BVDV-1a and BVDV-2b are evolving differently in Uruguay. This evolutionary divergence is notable when comparing patterns observed in other countries where these subtypes circulate. Our findings provide crucial knowledge that should be considered for developing effective BVDV control measures in Uruguay.