Disease transmission in horses refers to the spread of infectious agents such as bacteria, viruses, fungi, and parasites among equine populations. These pathogens can be transmitted through various routes, including direct contact, vector-borne transmission, or environmental exposure. Factors influencing disease transmission include horse density, management practices, and biosecurity measures. Understanding the mechanisms and conditions that facilitate the spread of diseases is essential for developing effective prevention and control strategies. This page compiles peer-reviewed research studies and scholarly articles that investigate the modes of transmission, risk factors, and management practices related to infectious diseases in horses.
HOLLISTER AC, LONGSHORE WA, DEAN BH, STEVENS IM.For the most part, epidemiologic phenomena observed in the outbreak of encephalitis in 1952 accorded with patterns that had been apparent in previous years. Ninety-seven per cent of the 414 laboratory-confirmed cases of western equine and St. Louis encephalitis in humans occurred in the 20 Central Valley counties. The cases of western equine encephalomyelitis in horses were generally scattered over the state. In the Central Valley most of the cases in horses were in animals less than two years of age; elsewhere the incidence was higher in older horses.There were no laboratory-confirmed cases o...
Klass LG, Krücken J, Mbedi S, Sparmann S, Schenk T, Andreotti S, von Samson-Himmelstjerna G.Mixed strongyle infections represent the most prevalent equine parasitosis and can result in life-threatening disease, especially in young horses. Species involvement and pathogenesis of this parasitosis are poorly understood, and data on foals and broodmares are notably lacking. Methods: In a longitudinal study undertaken in 2022 in Germany, individual faecal samples (n = 497) and metadata were collected for naturally infected foals and broodmares (n = 48) kept under conventional husbandry conditions. Nematode infections were detected coproscopically via the Mini-FLOTAC method. In a s...
Souza LL, Lima AS, Martins AS, Silva TA, Borsanelli AC, Dutra IS, Pupin RC, Gomes DC, Lemos RA.An outbreak of botulism occurred in March 2024 among horses at a Quarter Horse stud farm in Central-West Brazil. After ingesting baleage, 22 of 26 (85%) horses housed in stables and fed baleage became ill. The affected horses had dysphagia, muscular weakness, fasciculations, and progressive recumbency; 13 of 22 (59%) died within a few days. The diagnosis of type C botulism was established based on clinical and epidemiologic findings and confirmed by mouse bioassays, which indicated botulinum toxin type C in liver samples and intestinal contents. Furthermore, PCR testing identified toxigenic i...
Veit M, Matczuk AK.Equine arteritis virus (EAV) is a positive-stranded RNA virus of the Arteriviridae family. Its GP5/M dimer, the principal component of the viral envelope, mediates virus budding and serves as a key target for neutralizing antibodies. Using AlphaFold3, we predicted the 3D structure of the EAV GP5/M dimer and compared it to its homolog in porcine reproductive and respiratory syndrome virus (PRRSV). Both complexes share a conserved architecture comprising a short ectodomain, three helical transmembrane regions, and a β-sheet-rich endodomain. EAV GP5 features a longer ectodomain with four α-heli...
Turcotte GK, O'Sullivan TL, Spence KL, Winder CB, Greer AL.Biosecurity plays an important role in the prevention and control of infectious disease outbreaks in the equine population. With competition organizers responsible for implementing and upholding biosecurity requirements at competitions, it is important to understand the biosecurity landscape at these locations where Ontario horses commonly travel and interact in large group settings. Unassigned: The objective of this study was to describe the perspectives, challenges and experiences of competition organizers of both sanctioned and unsanctioned events in Ontario, Canada regarding implementing e...
Uprety T, Shaffer CL, Loynachan A, Janes J, Cassone L, Kennedy L, Bryant U, Ruby R, Swan M, Sponseller BT, Adam E, Lubbers B, Erol E.Salmonellosis is a highly contagious, zoonotic disease affecting both animal and human health. Early characterization of emerging Salmonella serotypes and associated antimicrobial resistance patterns are essential for outbreak controls in animals and humans. Between 2018 and 2025, 245 Salmonella enterica subsp. enterica were isolated from both ante-mortem and post-mortem equine cases. The predominant Salmonella serotypes were Typhimurium (83), Newport (28), 1,4,[5],12:i:- (26), Saintpaul (25), Hartford (15), and Mbandaka (12). S. Saintpaul, previously rare in horses, was detected in 21 cases i...
Penzhorn L, Crafford JE, Guthrie AJ.African horse sickness (AHS) is the only equine disease for which the World Organisation for Animal Health (WOAH) gives official disease-free status, given that it poses a major threat to the equine industry. The disease is caused by AHS virus (AHSV; family , taxon species ), which is endemic in sub-Saharan Africa. Reverse-transcription quantitative real-time PCR (RT-qPCR) is a rapid, sensitive detection method used in the diagnosis of AHS and the certification of animals as negative for AHSV for the purpose of movement. Genetic variability of AHSV may influence the accuracy of RT-qPCR detecti...
Mkpuma N, Meseko C, Shittu I, Chukwu C, Afiukwa FN, Iroha IR, Muhammad M, Ogbu O.Equine influenza virus (EIV) H3N8 is a highly contagious respiratory pathogen that poses significant health and economic risks to equids globally. In southeastern Nigeria where equids are sold and slaughtered, limited data exist on EIV epidemiology and circulating lineages. Methods: To address this gap, an active surveillance was conducted between January 2022 and October 2023. A total of 400 nasal swabs were collected from horses and donkeys at slaughterhouses and animal markets. The swabs were screened for equine influenza virus (EIV) using quantitative Reverse-Transcription Polymerase Chain...
Thieulent CJ, Sarkar S, Carossino M, Bhowmik M, Zhu H, Balasuriya UBR.Our laboratory identified the susceptible allelic variant of equine CXCL16 protein (EqCXCL16S) as an entry receptor for equine arteritis virus (EAV). However, EAV has a broad host cell tropism and infects cells that lack EqCXCL16S. Thus, we hypothesized that EAV interacts with other host cell protein(s) that facilitate EAV infection. A virus overlay protein-binding assay in combination with a Far-Western blot from EAV-susceptible equine pulmonary artery endothelial cells (EECs) and equine dermal fibroblasts (E. Derm) identified a 57 kDa protein, present in the membrane fraction of the protein ...
Beniwal N, Lal B, Mithina S, Verma CK, Kumar S, Phagna V, Jakhar K, Sonar S, Gupta V, Singh R, Kumar N, Tan CW, Thachamvally R, Singha H, Murzello K....Rabies is a neglected tropical zoonotic disease caused by rabies-virus (RV) infection and is responsible for almost 60,000 annual deaths globally, largely affecting the socio-economically disadvantaged population. Although fatality is preventable by immunization either before or after exposure with therapeutic antibodies, the high cost of prophylaxis or treatment limits their accessibility for the affected population. However, due to the almost 100% fatality rate in symptomatic individuals, almost 29 million annual vaccinations are performed, imposing high financial burden. Human transmission ...
Garzaro D, Rodríguez N, Medina G, Alcazar W, Gualdron M, Siem JA, Sulbaran Y, Barrios M, Liprandi F, Jaspe RC, Pujol FH.Madariaga virus (MADV), formerly known as the South American variant of Eastern Equine Encephalitis virus (EEEV), is an alphavirus that belongs to the family and has been periodically infecting equids in Venezuela since its first identification in 1975. This study reports the isolation and molecular characterization of MADV isolated from a horse in December 2024 in the context of MADV cases reported in Venezuela. Methods: Antibodies to the rabies virus were detected by indirect immunofluorescence, and to the Equine Infectious Anemia virus (EIAV) by passive immunodiffusion. MADV RNA was detect...
Qin S, Kulabieke T, Mizhamuhan D, Zhang M, Jin M, Abula G, Pi M, Wang H, Zhang Y, Guo Q.Equine theileriosis, caused by the protozoan parasite , represents a significant economic threat to the equine industry. In Xinjiang, China, an endemic area for this disease, systematic research on the genetic diversity of has been notably lacking. The aim of this study was to obtain molecular epidemiological data pertaining to the parasite in selected regions of Xinjiang, China, and analyze the genetic characteristics (including rRNA, , and genes) and genotype distribution patterns of isolates from these regions, providing a scientific basis for developing targeted prevention and control s...
Dorrego A, Olvera-Maneu S, Jose-Cunilleras E, Gago P, Raez A, Rivera B, Oporto A, Gonzalez S, Cruz-Lopez F.The forest fly ) is an obligate haematophagous dipteran insect (order Diptera) that primarily infests horses and may contribute to the circulation of vector-borne pathogens. This study aimed to investigate the presence of , s.l., , and , important vector-borne pathogens of equids, in forest flies collected from horses in endemic areas of Spain. A total of 170 forest flies were collected from 39 equids across four geographical regions in Spain (Segovia, Madrid, Toledo, and Menorca) and blood samples were collected from 27 of these horses. All flies were morphologically and molecularly identifi...
Aucoin AA, Zhidkov V, Legere RM, Borba KER, Landrock KK, Parker LE, Bray JM, Bordin AI, Cohen ND.To characterize age-related trajectories of the relative concentrations of anti-virulence-associated protein A (VapA) immunoglobulin (Ig)-G1, IgG3/5, IgG4/7, and IgA in serum and bronchoalveolar lavage fluid (BALF) as indicators of systemic and intrapulmonary immune responses in foals naturally exposed to Rhodococcus equi. Unassigned: Blood and BALF samples were collected at ages 4, 14, 28, and 56 days from healthy Quarter Horse foals (n = 19) naturally exposed to R equi. Samples were tested via ELISA for relative concentration of IgG1, IgG3/5, IgG4/7, and IgA recognizing the VapA of R equi. D...
Petry S, Tapprest J, Maillard K, Barbut F, Duquesne F, Kozak S, Foucher N, Bernez-Romand M, Bridoux L, Poquet I. an anaerobic, spore-forming enteropathogen, is less studied in animals than in humans despite its importance in One Health. We evaluated occurrence, diversity, circulation, and virulence in French Equidae ( = 100) after their necropsy in northwestern France, from 2019 to 2021. We systematically recovered all cecal contents and any watery intestinal contents. We isolated strains, determined their toxin gene profile by PCR, and established their PCR-ribotype according to the WEBRIBO database. We also performed free toxin detection. Twenty-seven Equidae were positive for and 20 had a toxigeni...
Barber C, McGlennon A, Whitlock F, Grewar J, Spalding S, Newton R, Dewé T.Charlotte Barber, Abigail McGlennon, Fleur Whitlock, John Grewar, Sophie Spalding, Richard Newton and Tamsin Dewé introduce a new government-funded initiative to strengthen the surveillance of antimicrobial resistance in the equine sector.
Gamage C, Graves A, Li G, Thieulent CJ, Balasuriya UBR, Morrow J, Vissani A, Parreño V, Matthijnssens J, Carossino M.Equine rotavirus B (ERVB) has caused foal diarrhea in central Kentucky since 2021. Coding-complete genome sequences from 14 strains circulating in 2024 revealed >99% nucleotide identity to the 2021 prototype ERVB strain RVB/Horse-wt/USA/KY1518/2021, with a conserved genomic constellation (G3-P[3]-I3-R3-C3-M3-A4-N3-T3-E3-H3).
Wasiński B, Złotnicka J, Kubajka M, Olejarczyk M, Szulowski K.Contagious equine metritis (CEM) is a cosmopolitan infectious, venereal disease of equids caused by the bacterium . Its frequently asymptomatic course leads to its prevalence sometimes being underestimated, and knowledge of the spread of infections with its causative agent is insufficient. The aim of this study is to summarise and present data on the incidence of infections in horses in Poland. Unassigned: In the years 2018-2023, routine laboratory tests of horses for CEM were carried out. Between 52 and 99 horses were examined annually. Swabs from the external parts of the urogenital system ...
Pipitpornsirikul P, Thangthamniyom N, Laikul A, Songkasupa T, Pathomsakulwong W, Apichaimongkonkun T, Kasemsuwan S, E-Kobon T, Lekcharoensuk P.African horse sickness (AHS), a life-threatening disease caused by African horse sickness virus serotype 1 (AHSV-1), emerged in Thailand in February 2020 with 607 cases and a 93% fatality rate. The outbreak was mitigated by vector control and a live attenuated virus (LAV) vaccine. Information regarding viremia and immunity after infection and vaccination during outbreaks are essential for controlling disease transmission. This study evaluated these parameters in 15 infected naïve horses and 11 vaccinated horses during the 2020 outbreak. Whole blood was collected and subjected to RT real-time ...
van Rijn PA, Wernery U, Feddema AJ, Maris-Veldhuis MA, Joseph S, van Gennip RGP.African Horse Sickness (AHS) is a devastating vector-borne viral disease of equids with a mortality up to 95 % in naïve domestic horses. The causative African horse sickness virus (AHSV) is a distinct species of the genus Orbivirus of the family Sedoreoviridae, consisting of nine serotypes showing limited cross protection. AHSV is transmitted by Culicoides biting midges. Outbreaks cause huge economic losses in developing African countries. AHS has become a serious threat for countries outside Africa, since endemic Culicoides species in moderate climates appear competent vectors of the closel...
White SC, Thomas J, Shores C, Zimmerman K.Feral horses () have established large populations in west-central British Columbia (BC), Canada, where they overlap with native ungulates, including a declining woodland caribou () herd. In addition, feral horses co-occur with large carnivore species including wolf () and cougar (). Feral horses may act as a resource subsidy for predators, potentially altering predator-prey dynamics, yet empirical observations of predator interactions with feral horses are scarce in Canada. Between 2019 and 2025, we documented 21 instances of wolf predation or scavenging of feral horses, including one direct ...
Roy CN, Wiechmann CE, Dev A, Walther BK, Musser JM, Olsen RJ, Beres SB, Axell-House DB. subsp. (SESZ) are zoonotic group C streptococci primarily acquired from contact with horses and other animals, such as llamas. They are unusual causes of infection in humans and rarely cause infective endocarditis. Unassigned: A 58-year-old woman presented with fever, malaise, and polyarthritis. Clinical evaluation diagnosed native tricuspid valve SESZ endocarditis. The SESZ isolate was genetically closely related to a clone causing an outbreak of post-streptococcal glomerulonephritis linked to the consumption of unpasteurized cheese in Brazil. The patient had no exposure to unpasteurized ch...
Stasiak K, Dunowska M, Rola J.Equid herpesvirus 5 (EHV-5) comprises a group of heterogeneous viruses with a worldwide distribution. Primary infection typically occurs early in life, which is followed by latency and periodic recrudescence of the virus. The aim of this study was to determine the genetic variation of EHV-5 in individual animals over time and to determine the dynamics of EHV-5 spread among selected mare-foal pairs at three horse studs. The partial glycoprotein B () gene was amplified from archival nasal swab samples. Sequences from 3-5 clones from each PCR product were compared using identity matrix, phylogeny...
Silva VVD, Leite DPSBM, Gonçalves LMT, Pinto GOA, Oliveira PRF, Mota RA.Rabies is a lethal zoonosis caused by the rabies virus (RABV), primarily transmitted by the common vampire bat (Desmodus rotundus). Brazil, home to the largest equine population in South America, faces ongoing challenges with equine rabies, which impacts both the economy and public health. This study aimed to identify spatial and temporal patterns of rabies in equines in Brazil between 2006 and 2023. Data from the Zoosanitary Information System (SIZ) of the Brazilian Ministry of Agriculture, Livestock, and Food Supply (MAPA) were used. The incidence risk (IR) was calculated for each region and...
Fonseca-Rodríguez O, Pailler-García L, Urban A, Cáceres G, Napp S, Busquets N.West Nile virus (WNV) is an arthropod-borne virus primarily transmitted by Culex mosquitoes, among birds, but occasionally infecting humans and equids. Understanding environmental factors on the disease occurrence is crucial for planning effective prevention and control strategies. Our study estimates the short-term effects of ambient temperature, relative humidity and precipitation on weekly cases of WNV in equids in Spain, using a space-time stratified case-crossover design. Because WNV transmission occurs sometime after the weather conditions become favorable for the vector, we aimed to est...
Arai N, Niwa H, Uchida-Fujii E, Sawa Y, Tamamura-Andoh Y, Kinoshita Y, Momoki A, Watanabe-Yanai A, Iwata T, Kubo M, Kusumoto M.Sequence type 34 (ST34) Salmonella enterica serovar Typhimurium and its monophasic variant (Salmonella 4,[5],12:i:-) are the most prevalent clones among humans and animals worldwide, including in Japan. Although cross-species transmission may have occurred in the background of global spread, the matter remains unresolved. Here, we conducted high-resolution phylogenetic analysis using whole-genome sequencing data of Salmonella Typhimurium and 4,[5],12:i:- obtained from a horse and cattle breeding district in Japan and identified cases of cross-species transmission of ST34 Salmonella 4,[5],12:i:...
Gräf T, Rodriguez MC, de Oliveira Brandão Y, Royer CA, do Nascimento Ferreira C, Confortin C, Zanluca C, Strottmann DM, Duarte Dos Santos CN....Rocio virus (ROCV), a neurotropic arbovirus of the genus, caused Brazil’s largest encephalitis outbreak in the 1970s but has since been rarely detected. We report the first ROCV encephalitis clinical case after nearly 40 years and isolated and sequenced the virus from CNS tissue of a horse. Metatranscriptomics enabled full-genome sequencing, revealing divergence from the reference sequence at an evolutionary rate of 5.8–7.0 × 10⁻⁴, consistent with . Thirty-one non-synonymous substitutions were identified, with the envelope protein most affected. Findings indicate ROCV cryptic circula...
Liu J, Huang X, Wang Y, Wang Y, Luo R, Lu X, Cao K, Xing J, Tu Y, Zheng W.Antibiotic resistance genes (ARGs) are emerging contaminants threatening public health, yet their transmission risk via mare milk products remains understudied. Using metagenomics, we analyzed lactic acid bacteria (LAB)-inoculated fermented, naturally fermented, raw, and pasteurized mare milk to investigate the effect of LAB inoculation on the distribution and transmission pathways of ARGs in mare milk. The results showed that naturally fermented, raw, and pasteurized mare milk had the highest number of pathogens, relative abundance of ARGs, and relative abundance of mobile genetic elements (M...
Kwak ML, Echigo H, Hoketsu T, Taya Y, Numata H, Shiraki Y, Kelava S, Markowsky G, McInnes D, Hayashi N, Nonaka N, Kawai M, Nakao R.The control of ticks is challenging owing to their ubiquity, complex ecologies, and difficulties relating to costs and non-target impacts of chemical control programs. Nature-based solutions centre around co-opting natural processes and biodiversity to address socio-environmental problems; and in some cases, rewilded species can provide nature-based solutions. In northern Japan, the winter ecology of ticks is poorly studied, though some species are believed to overwinter under the snow. Winter grazing activity of rewilded horses may disturb overwintering ticks, exposing them to sub-zero temper...
Narouei M, Rahimi H, Kafshdouzan K.Infections caused by and , as zoonotic diseases, pose a serious threat to the health of humans and animals. To date, there is limited information regarding these diseases in horses. This study aimed to evaluate the prevalence of and in the serum of racehorses in Iran (Golestan province). 350 blood samples were collected from racehorses in four regions of Golestan province, and demographic data (sex, age, and sampling location) were recorded. The collected serum samples were examined by PCR to identify the genomes of and . The results showed that 3.4 % (P < 0.05, 95 % CI: 1.97 % - 5.9 %) of...
Harel B, Sévin C, Le Hello S, Moreau P, Giard JC, Petry S, Gravey F.Enterobacteriaceae are opportunistic pathogens responsible for local or systemic infections in both human and veterinary medicine. To monitor circulating strains in stud farms in Normandy (France), we investigated a collection of Enterobacteriaceae isolated from necropsied equids performed in the region between 1997 and 2020. These strains were initially identified using MALDI-TOF; however, as this method failed to identify some isolates, whole genome sequencing followed by rMLST analysis was subsequently performed. Different genera were identified: Enterobacter spp., Huaxiibacter spp., Lellio...
