Disease outbreaks in horses refer to the occurrence and spread of infectious diseases within equine populations. These outbreaks can be caused by various pathogens, including bacteria, viruses, and parasites, and can lead to significant health issues in affected horses. Common diseases that may result in outbreaks include equine influenza, equine herpesvirus, strangles, and equine infectious anemia. The transmission of these diseases can occur through direct contact, environmental exposure, or vectors such as insects. Disease outbreaks can have substantial impacts on horse health, welfare, and the equine industry as a whole. This page compiles peer-reviewed research studies and scholarly articles that explore the epidemiology, transmission dynamics, and management strategies associated with disease outbreaks in equine populations.
Berrocal A, van den Ingh TS.The pathological findings in three cases of equine phycomycosis in Costa Rica are described. Two cutaneous (Pythium sp) and one nasal lesion (Conidiobolus) were observed.
Petzoldt K, Merkt H, Müller E, Kirpal G.Over the last years the percentage of foals lost by EHV at term or close to term seems to be higher than in former years. Furthermore, the pathological findings seem to shift from liver to lung. So far there has been no explanation for this phenomenon.
Webb PA, Monath TP, Reif JS, Smith GC, Kemp GE, Lazuick JS, Walton TE.Epidemiologic evaluations were made of farm personnel on vesicular stomatitis-affected premises along the front range of the Rocky Mountains in Colorado during the 1982 epizootic. A similar antibody prevalence was noted to that of veterinarians and research and regulatory personnel who were involved with the same epizootic. Risk of infection resulted from intimate physical contact with infected horses or cows. Incidence and infection rates in horses were 45%; rates in cows were much lower, only 5%. Some epidemiologic clues were gained by a detailed study of an equine ranch. The pasture was inc...
Sprouse RF, Garner HE, Green EM.Thirteen (65 per cent) of 20 horses subjected to carbohydrate overload developed Obel Grade 3 lameness within 56 h. Increases in plasma endotoxin from control levels of less than 0.1 ng/litre to values ranging from 2.4 to 81.53 ng/litre were measured in 11 (85 per cent) of 13 horses during the onset of Obel Grade 3 lameness. Obel Grade 3 lameness was associated with rises in plasma Gram-negative endotoxin levels in 11 (92 per cent) of 12 horses. Two peak increases separated by 16 h were verified in five (45 per cent) of 11 horses that exhibited both endotoxaemia and Obel Grade 3 lameness. The ...
Calisher CH, Monath TP, Sabattini MS, Mitchell CJ, Lazuick JS, Tesh RB, Cropp CB.In 1983, 17 virus strains were isolated from mosquitoes collected during an outbreak of western equine encephalitis in Santa Fe Province, Argentina. Strains of western equine encephalitis, Venezuelan equine encephalitis, St. Louis encephalitis, and Antequera viruses were isolated, as were several bunyaviruses of the California and Bunyamwera serogroups and a new vesiculovirus. Complement fixation and neutralization tests were used to identify the California serogroup virus as a subtype of Melao virus, the Bunyamwera serogroup virus as a subtype of both Maguari and Playas viruses, and the vesic...
Mumford JA, Rossdale PD, Jessett DM, Gann SJ, Ousey J, Cook RF.An extensive outbreak of EHV-1 abortions occurred on a stud farm in England in 1985. Of the 67 pregnant mares present on the stud farm, 31 were challenged with EHV-1, resulting in the loss of 22 fetuses or foals. Laboratory investigations revealed that the spread of the virus closely followed movement of apparently healthy mares (during the incubation period of the infection). During the outbreak mares were challenged 1-4 months before the expected foaling date. There was no relationship between the gestational age at the time of challenge and the subsequent outcome of infection in terms of ab...
Browning GF, Studdert MJ.The epidemiology of equine herpesvirus 2 was examined by using restriction endonuclease DNA fingerprints to distinguish viruses isolated from two groups of horses. The first group consisted of three yearlings isolated from other horses but in contact with each other for 418 days, whereas the second comprised seven mares and their foals, which were sampled at monthly intervals from parturition until the foals were about 180 days old. There was a complex pattern of transmission, with 15 different viruses isolated from both groups. Four distinguishable viruses were isolated from the three yearlin...
Mitchell CJ, Monath TP, Sabattini MS, Daffner JF, Cropp CB, Calisher CH, Darsie RF, Jakob WL.Mosquitoes were collected in Santa Fe and Rio Negro provinces, Argentina, in 1982-1983 during a western equine encephalitis (WEE) epizootic. Totals of 153,084 mosquitoes from Santa Fe Province and 484 from Rio Negro Province were tested for virus in 2,351 pools. Seventeen virus strains were isolated, all from Santa Fe collections, as follows: 4 WEE, 6 Venezuelan equine encephalitis, 1 St. Louis encephalitis, 2 Antequera, 1 Maguari, 1 Melao, 1 new vesiculovirus (Calchaqui), and 1 Gamboa. The WEE virus isolates were from Aedes albifasciatus, Anopheles albitarsis, Mansonia species, and Psorophora...
Eichhorn W.Infections and clinical diseases caused by equine 2 influenza A viruses are observed worldwide. The frequency of these outbreaks supports the hypothesis that antigenic variation of the surface proteins may play an important role. For the demonstration of these variations, monoclonal antibodies (Mabs) were prepared. They are directed against the hemagglutinin or the neuraminidase of the prototype strain a/eq/Miami/1/63. In hemagglutination-inhibition assays with Mabs two reaction patterns were observed: four Mabs inhibited 14 out of 17 strains tested. Another Mab recognized the hemagglutinin of...
Reif JS, Webb PA, Monath TP, Emerson JK, Poland JD, Kemp GE, Cholas G.In 1982-1983, an epizootic of vesicular stomatitis occurred in the western United States. Veterinarians, research workers, and regulatory personnel who were exposed to vesicular stomatitis virus were examined for patterns of human infection and prevalence of vesicular stomatitis New Jersey serotype neutralizing antibody. Insight into the mechanism of transmission was sought by comparing activities of antibody-positive and antibody-negative persons. A statistically significant risk factor was a history of infected animals sneezing in the face of serosurvey participants. Elevated odds ratios wer...
Clark GG, Crabbs CL, Bailey CL, Calisher CH, Craig GB.An arbovirus survey was conducted during August 1985 at White Sands Missile Range in southcentral New Mexico following a suspected arboviral disease epizootic among feral horses. A total of 20,566 mosquitoes (18,505 females and 2,061 males) and 8,900 biting gnats were collected and assayed for virus. Female mosquitoes were principally Aedes campestris (54.8%), Aedes dorsalis (30.4%) and Culex tarsalis (13.2%). Arboviruses were not isolated from biting gnats, but mosquitoes yielded a total of 37 viral isolates, including western equine encephalitis (WEE) (18), California serogroup (15), Cache V...
Herd RP.Seasonal rises in mean faecal egg output were observed in grazing ponies in spring (578 eggs per gram) and in summer (930 epg) on 30 April and 2 September, respectively, in untreated ponies. Pasture infectivity reached a peak of 18,486 third stage larvae (L3)/kg on 17 September, two weeks after peak egg counts, coincidental with abundant September rainfall (103.0 mm). Differentiation of infective larvae from pasture showed the cyathostomes (small strongyles) to be predominant, but Trichostrongylus axei assumed major importance from late August to October. The large strongyles were rarely detec...
Furmanski M, Murcia PR.The ecological factors that led to the 1918 influenza pandemic remain unknown. We hypothesize that horses acted as intermediate hosts spreading a prepandemic avian-origin virus before 1918. This is supported by reports describing a large epizootic of unusually severe equine influenza beginning in 1915. Furthermore, the high horse demand during World War I resulted in one of the biggest equine mobilizations in North America between 1914 and 1918. This extensive movement of horses provided abundant opportunities for virus reassortment between prepandemic avian and human influenza viruses. Archiv...
Kim K, Xu T, Kannan Villalan A, Chi T, Yu X, Jin M, Wu R, Ni G, Sui S, Wang Z, Wang X.African horse sickness (AHS) is a viral disease transmitted by arthropods that impacts Equidae, specifically horses and related species. Recognized as a notifiable disease by the World Organisation for Animal Health (WOAH), AHS is associated with a high mortality rate of 80%-90% in susceptible hosts and exhibits rapid transmission dynamics. Historical records document numerous instances of mass horse deaths attributed to AHS, with recent occurrences in Thailand and Malaysia in 2020 causing heightened concerns within the local horse industry. The lack of a comprehensive global perspective on th...
de la Cuesta-Torrado M, Velloso Alvarez A, Santiago-Llorente I, Armengou L, Nieto F, Ríos J, Cruz-López F, Jose-Cunilleras E.Equine herpesvirus myeloencephalopathy (EHM) is a persistent threat to horses, with unclear risk factors and disease severity. Objective: To evaluate risk factors, effective reproduction rate (Rt), and long-term athletic outcomes of an EHM outbreak. Methods: Retrospective study of the 2021 EHM outbreak in Valencia, Spain, examining associations between risk factors (sex, age, breed, country of origin, and vaccination status) and case fatality rate, EHM development, and odds of returning to competition using odds ratios [95% CI] and Rt via the Robert Kochs Institute method. Results: Among 191 h...
de la Cuesta-Torrado M, Velloso Alvarez A, Cárdenas-Rebollo JM, Neira-Egea P, Vitale V, Cuervo-Arango J.Understanding of equine herpesvirus-1 (EHV-1) myeloencephalopathy (EHM) is complicated by disparities among studies. Objective: Compare clinical findings and outcome in horses involved in 2 recent EHM outbreaks. Methods: Twenty-five and 10 horses affected during 2 natural EHM outbreaks were admitted to a veterinary teaching hospital (VTH) in 2021 and 2023, respectively. Methods: Data collected from the VTH and surveys completed by riders and horse owners were analyzed retrospectively. Results: No risk factors associated with EHM development showed significant differences between the outbreaks;...
Knox A, Beddoe T. subspecies , commonly referred to as "strangles", poses a significant biosecurity challenge across equine farms worldwide. The continuous prevalence and highly transmissibility of strangles necessitates a rapid and accurate diagnostic procedure. However, current "gold-standard" techniques, such as cultures and quantitative polymerase chain reaction (qPCR), are unreliable or inaccessible, and require lengthy periods between sample collection and results. Moreover, the lack of a standardized detection protocol can lead to variations in results. This study aimed to develop a reproducible and fie...
Pusterla N, Lawton K, Barnum S.In populations of healthy show horses, the subclinical transmission and circulation of respiratory pathogens can lead to disease outbreaks. Due to recent outbreaks of equine herpesvirus-1 myeloencephalopathy (EHM) in the USA and Europe, many show organizers have instituted various biosecurity protocols such as individual horse testing, monitoring for early clinical disease and increasing hygiene and cleanliness protocols. The aim of this study was to determine the accuracy of detecting EHV-1 in the various environmental samples collected from the stalls of subclinical shedders. Four healthy ad...
Tong P, Yang E, Liu B, Tian S, Suo Y, Pan J, Dang Y, Palidan N, Jia C, Kuang L, Xie J.Varicellovirus equidalpha1 (formerly Equid alphaherpesvirus 1, EqAHV-1) is among the most important viruses responsible for respiratory disease outbreaks among horses throughout the world. No reports to date have detailed the association between EqAHV-1 and respiratory disease among horses in China. This study described one such outbreak among a population of horses in north Xinjiang that occurred from April 2021 - May 2023. Results: qPCR revealed that EqAHV-1 was detectable in all samples and this virus was identified as a possible source of respiratory disease, although a limited subset of t...
Ma X, Zhang Y, Na L, Qi T, Ma W, Guo X, Wang XF, Wang X.African horse sickness (AHS) is an acute, fatal, contagious disease of animals of the family Equidae and is caused by infection with the African horse sickness virus (AHSV). Based on the outer capsid protein VP2, AHSV is classified into nine serotypes (AHSV-1 to -9) with little or no serological cross-reactivity between them. In 2020, AHS outbreaks caused by AHSV-1 were reported in Thailand and Malaysia, marking the first occurrences of AHS in Southeast Asia. However, little is known about the antigenic profile of AHSV-1 VP2. In this study, a recombinant VP2 protein was expressed in and used ...
de Martinis C, Cardillo L, Pesce F, Viscardi M, Cozzolino L, Paradiso R, Cavallo S, De Ascentis M, Goffredo M, Monaco F, Savini G, D'Orilia F....West Nile virus (WNV) is the most widespread arbovirus worldwide, responsible for severe neurological symptoms in humans as well as in horses and birds. The main reservoir and amplifier of the virus are birds, and migratory birds seem to have a key role in the introduction and spread of WNV during their migratory routes. WNV lineage 1 (L1) has been missing in Italy for almost 10 years, only to reappear in 2020 in two dead raptor birds in southern Italy. The present study reports the first equine outbreak in the Campania region. A 7-year-old horse died because of worsening neurological signs ...
The Western equine encephalitis virus is transmitted between mosquitoes and wild birds. Mosquitoes spread the virus to horses and human populations, causing severe encephalitis and death. The most recent large outbreak occurred in South America from November 2023 to April 2024. We identified and genetically characterized Uruguayan strains during this outbreak to understand their evolutionary trends and rapid expansion. We obtained genomes from 15 strains using a novel multiplex PCR assay combined with next-generation Illumina sequencing. The phylogenetic analysis revealed that viruses from Uru...
Ordonez JV, Scherer WF, Dickerman RW.During the wet seasons of 1972 and possibly 1971, sentinel horses became infected by Venezuelan encephalitis (VE) virus in a temporally and geographically progressive manner inland from an enzootic marsh focus of virus on the Pacific couast of southeastern Guatemala. During the wet seasons of 1972 and 1973, VE virus was detected by sentinel horses (and a sentinel hamster in 1972) in a small woods 10 km north of the marsh, but virus was undetectable there during the dry seasons of 1973 and 1974 and the wet season of 1974. Culex (Melanoconion) mosquitoes were found in this woods and at the marsh...
Heinrich B.This research article corrects a common misconception about the energy metabolism in horses during short sprinting and long-distance running events, emphasizing that short sprints are primarily powered by anaerobic activity, […]
This research article provides an update on equine disease surveillance in the UK, collated from various diagnostic laboratories and veterinary practices, and highlights potential biases in the data due to […]
