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.
Adams AP, Navarro-Lopez R, Ramirez-Aguilar FJ, Lopez-Gonzalez I, Leal G, Flores-Mayorga JM, Travassos da Rosa AP, Saxton-Shaw KD, Singh AJ....Venezuelan equine encephalitis virus (VEEV) has been the causative agent for sporadic epidemics and equine epizootics throughout the Americas since the 1930s. In 1969, an outbreak of Venezuelan equine encephalitis (VEE) spread rapidly from Guatemala and through the Gulf Coast region of Mexico, reaching Texas in 1971. Since this outbreak, there have been very few studies to determine the northward extent of endemic VEEV in this region. This study reports the findings of serologic surveillance in the Gulf Coast region of Mexico from 2003-2010. Phylogenetic analysis was also performed on viral is...
Aklilu N, Batten C, Gelaye E, Jenberie S, Ayelet G, Wilson A, Belay A, Asfaw Y, Oura C, Maan S, Bachanek-Bankowska K, Mertens PP.African horse sickness (AHS) is associated with high morbidity and mortality in equids, especially horses. A retrospective analysis was carried out concerning 737 AHS outbreaks that occurred during 2007-2010 in Ethiopia. A total of ten outbreaks were investigated in the study period. All four forms of the disease (pulmonary, cardiac, horse sickness fever and the combined form) were observed, with the cardiac form being the most prevalent. Multiple African horse sickness virus serotypes (AHSV-2, AHSV-4, AHSV-6, AHSV-8 and AHSV-9) were detected by molecular methods (type-specific real-time RT-PC...
Pusterla N, Mapes S, Wademan C, White A, Ball R, Sapp K, Burns P, Ormond C, Butterworth K, Bartol J, Magdesian KG.The purpose of this study was to describe clinical, hematological and fecal PCR results from 161 horses involved in outbreaks associated with ECoV. The outbreaks happened at four separate boarding facilities between November 2011 and April 2012 in the States of CA, TX, WI and MA. Following the molecular detection of ECoV in the feces from the initial index cases, the remaining herdmates were closely observed for the development of clinical signs. Fecal samples were collected from sick and healthy horses for the PCR detection of ECoV. All four outbreaks involved primarily adult horses. Fifty-ni...
Bisgaard M, Bojesen AM, Petersen MR, Christensen H.Infections of poultry due to Streptococcus equi subsp. zooepidemicus have been rare during the past decades and dissimilarities have been reported as to symptoms and lesions; likewise, the source of serious outbreaks has remained speculative. An outbreak affecting 11,000 free-range chickens at the age of 47 wk is reported. The outbreak manifested itself as acute at the onset and was followed by a chronic stage, resulting in some 80% mortality within 21 wk. Small-colony variants (SCVs) of S. equi subsp. zooepidemicus associated with the chronic phase are reported for the first time, and it is d...
Fassil H, El Harrak M, Marié JL.Morocco has undergone three outbreaks of West Nile fever. The first, in 1996, began with a case in a horse herd in Benslimane (central region) and spread to neighboring cities (in the central and northwestern regions). The next two outbreaks appeared after identical 7-year epidemiological latency periods (in 2003 and 2010) in the same area and season. The only human case, which was fatal, occurred during the 1996 outbreak. The West Nile virus strains circulating in Morocco are closely related to other western Mediterranean strains and are characterized by high virulence in horses.
Botha CJ, Lewis A, du Plessis EC, Clift SJ, Williams MC.Twenty-eight horses in southern Mozambique died after exhibiting severe respiratory distress. At necropsy, the overinflated lungs did not collapse, had prominent rib impressions, and were fibrotic and emphysematous. Microscopically, prominent proliferation of nonciliated epithelial (Clara) cells in the terminal bronchioles and pulmonary fibrosis were observed, indicative of chronic pneumotoxicity. Transmission electron microscopy demonstrated hyperplasia, desquamation, and apical bulging of Clara cells into the bronchiolar lumen. The outbreak was attributed to ingestion of Crotalaria dura J.M....
Libardoni F, Vielmo A, Farias L, Matter LB, Pötter L, Spilki FR, de Vargas AC.Strangles is the main upper respiratory tract disease of horses. There are currently no studies on the changes in alleles of the M protein gene (seM) in Brazilian isolates of Streptococcus equi ssp. equi (S. equi). This study aimed to analyze and differentiate molecularly S. equi isolates from equine clinical specimens from southern Brazil, between 1994 and 2010. seM alleles were analyzed in 47 isolates of S. equi obtained from clinical cases of strangles (15 Thoroughbred horses, 29 Crioulo breed horses and three Brasileiro de Hipismo--BH). seM alleles characterization was performed by compari...
Lafave MR, Butterwick DJ, Murray RP, Freeman T, Lau BH.The purpose of this study was to establish the content validity of the Rodeo SCAT for the sport of rodeo and bull riding. The study design was comprised of expert consensus and content validation. A modified Ebel procedure was employed to content validate the rodeo SCAT. Content validation using this method includes experts agreeing on the importance of each item that comprises the rodeo SCAT. This 3-stage process involved: 1) face validation by a local committee: 2) initial expert consensus measurement via distance; and 3) a face-to-face discussion for items that did not originally achieve 80...
El-Hage CM, Savage CJ, Minke JM, Ficorilli NP, Watson J, Gilkerson JR.During the 2007 Australian equine influenza (EI) outbreak, an accelerated primary course 14 day intervaccination schedule was proposed, but not widely implemented. Expert opinion was divided as to the efficacy of such a schedule given the lack of published data. This study determined the level and duration of humoral immunity following administration of a recombinant canarypox-vectored vaccine (ALVAC-EIV) with a primary intervaccination interval of 14 days and booster at 105 days. Objective: To examine whether protective levels of immunity of adequate duration were achieved following a primary...
Sas AM, van der Kolk JH, Dank M, Westermann CM.This article reviews the literature on equine atypical myopathy (AM), an acute, severe rhabdomyolysis that occurs in horses at pasture. The prevalence, mortality, clinical signs, pathology, potential aetiology, typical aspects, diagnosis, treatment, and prognosis are described. Horse management, characteristic weather conditions, and possible preventive measures are also discussed. In addition, the characteristics of 54 highly probable or confirmed cases of equine AM occurring between autumn 2009 (27 cases) and spring 2010 (27 cases) in the Netherlands are described. Of the 54 affected horses,...
Mahalingam S, Herrero LJ, Playford EG, Spann K, Herring B, Rolph MS, Middleton D, McCall B, Field H, Wang LF.Hendra virus, first identified in 1994 in Queensland, is an emerging zoonotic pathogen gaining importance in Australia because a growing number of infections are reported in horses and people. The virus, a member of the family Paramyxoviridae (genus Henipavirus), is transmitted to horses by pteropid bats (fruit bats or flying foxes), with human infection a result of direct contact with infected horses. Case-fatality rate is high in both horses and people, and so far, more than 60 horses and four people have died from Hendra virus infection in Australia. Human infection is characterised by an a...
Sudan V, Sharma RL, Gupta SR, Borah MK.The occurrence of Eimeria leukarti infection in equine is being sporadically documented despite its cosmopolitan prevalence. A Marwari mare, aged 3 years and 6 months and owned by a socio-economically weaker class of labourer of royal families, was suffering from non specific enteric disorders. Detailed systemic clinical examination of mare confirmed subclinical enteric infection with E. leukarti and piroplasms of Babesia (Theileria) equi in the circulating erythrocytes. She was therapeutically managed with synchronous administration of specific and supportive therapy with success. Non speci...
Wagner B, Erb HN.Reported cases of Lyme disease (a chronic disease caused by infection with Borrelia burgdorferi) in humans increased more than two-fold between 1992 and 2006 in the United States. Recently, the annual number of reported human Lyme disease cases stabilized (according to the Center for Disease Control and Prevention) but the geographic distribution seemed to increase. In New York (NY) State, USA, a spread from the original Lyme disease focus in southeastern parts of the state has occurred. We determined incidence risks of new companion animal infection in 2011 with B. burgdorferi by county in 45...
Hartig W, Houe H, Andersen PH.At present Denmark has no central database holding records of equine health and disease. Nor have attitudes to the establishment of a national database, and the concerns it raises, been investigated in a systematic way. The objective of the present study was to assess the attitudes and concerns of potential database stakeholders. Attitudes to participation, and the location, financing and management of the proposed database, together with any concerns it raises, were investigated in a questionnaire study of 13 potential stakeholder groups in Denmark (in total, 1581 questionnaire recipients and...
Arthropodborne viruses (arboviruses) are transmitted to humans primarily through the bites of infected mosquitoes and ticks. Symptomatic infections most often manifest as a systemic febrile illness and, less commonly, as neuroinvasive disease (e.g., meningitis, encephalitis, or acute flaccid paralysis). West Nile virus (WNV) is the leading cause of domestically acquired arboviral disease in the United States. However, several other arboviruses also cause seasonal outbreaks and sporadic cases. In 2011, CDC received reports of 871 cases of nationally notifiable arboviral diseases (excluding deng...
Oliveira-Filho JP, Cagnini DQ, Badial PR, Pessoa MA, Del Piero F, Borges AS.Cassia occidentalis is a bush from the Leguminosae family, subfamily Caesalpinoideae, and is a toxic plant of veterinary interest due to the occasional contamination of animal rations. This report describes the clinical and histopathological findings of an outbreak of C. occidentalis poisoning in horses. Twenty mares were poisoned after consuming ground corn contaminated with 8% of C. occidentalis seeds. Of the 20 animals affected, 12 died: 8 mares were found dead, 2 died 6 h after the onset of clinical signs compatible with hepatic encephalopathy and the 2 other animals were subjected to euth...
Thompson GM, Jess S, Murchie AK.African horse sickness is an economically highly important non-contagious but infectious Orbivirus disease that is transmitted by various species of Culicoides midges. The equids most severely affected by the virus are horses, ponies, and European donkeys; mules are somewhat less susceptible, and African donkeys and zebra are refractory to the devastating consequences of infection. In recent years, Bluetongue virus, an Orbivirus similar to African horse sickness, which also utilises Culicoides spp. as its vector, has drastically increased its range into previously unaffected regions in norther...
Rosanowski SM, Cogger N, Rogers CW, Benschop J, Stevenson MA.We conducted a cross-sectional survey to determine the demographic characteristics of non-commercial horses in New Zealand. A sampling frame of properties with non-commercial horses was derived from the national farms database, AgriBase™. Horse properties were stratified by property size and a generalised random-tessellated stratified (GRTS) sampling strategy was used to select properties (n=2912) to take part in the survey. The GRTS sampling design allowed for the selection of properties that were spatially balanced relative to the distribution of horse properties throughout the country. Th...
Potter ME, Currier RW, Pearson JE, Harris JC, Parker RL.In mid-July, 1975, western equine encephalomyelitis (WEE) virus was isolated from mosquitoes collected in flooded areas of eastern North Dakota and western Minnesota. Inasmuch as clinical manifestations of WEE are usually observed in horses before human cases of encephalitis are recognized, surveillance of equine disease was initiated. Sixty-one practicing veterinarians from the are under surveillance reported 281 cases of WEE in horses from June through September, with peak incidence in late July. The high percentage of sero-positive, clinically normal, unvaccinated horses in one region sugge...
Sugiura T, Matsumura T, Fukunaga Y, Hirasawa K.A sero-epizootiological study was conducted on horses which showed clinical pyrexia at two training centers, each of which maintained 1, 200 to 2, 100 racehorses for training, of the Japan Racing Association. It continued from 1980 to 1985 to clarify the cause of pyrexia, so that measures might be considered for the prevention of infectious disease. A total of 3, 849 horses were found to be affected with pyrexia for the 6 years. Of them, 2, 852 horses were tested to equine herpesvirus type 1 (EHV-1), equine rhinovirus type 1 (ERhV-1), rotavirus and equine adenovirus (EAdV) by collecting paired...
Erol E, Sells SF, Williams NM, Kennedy L, Locke SJ, Labeda DP, Donahue JM, Carter CN.Nocardioform placentitis associated with gram positive branching actinomycetes caused a record number of abortions in mares diagnosed by the University of Kentucky Veterinary Diagnostic Laboratory (UKVDL) affecting the 2011 foal crop (2011 foal crop: the cohort of foals conceived during the 2010 breeding season). The goal of the present study is to make a comprehensive analysis of this outbreak in terms of frequencies of the bacteria causing nocardioform placentitis mediated abortions and to investigate the ages of fetuses, abortion months and breeding times. In the present study, characterist...
Kirkland PD, Delbridge G.An important consideration in the selection of a vaccine during the Australian equine influenza (EI) outbreak in 2007 was the ability to differentiate between infected and vaccinated animals (DIVA). A blocking enzyme-linked immunosorbent assay (bELISA) targeted for the nucleoprotein of influenza A viruses was developed to differentiate between naturally infected horses and horses vaccinated with the ProteqFlu® vaccine, which only induces a response to viral haemagglutinin. This bELISA assay met the DIVA requirements and was used extensively during the EI control and eradication programs and '...
de la Rua-Domenech R, Reid SW, González-Zariquiey AE, Wood JL, Gettinby G.A Monte Carlo model that simulates the management life cycle of a horse population in training on a Thoroughbred flat racing yard (i.e. stable) was developed for computer implementation. Each horse was characterised by several state variables. Discrete events at the horse level were triggered stochastically to reflect uncertainty about some input assumptions and heterogeneity of the horse population in a particular yard. This mathematical model was subsequently used to mimic the spread of equine influenza (EI) within a typical yard following the introduction of one or several infectious horses...
Pusterla N, Conrad PA, Packham AE, Mapes SM, Finno CJ, Gardner IA, Barr BC, Ferraro GL, Wilson WD.Over a 2-yr study period, we investigated possible endogenous transplacental transmission of Neospora hughesi in 74 mare and foal pairs following the diagnosis of neuronal neosporosis in a weanling foal. Presuckle and postsuckle serum of each foal, serum and colostrum of each periparturient mare, and serum of each mare and foal pair, collected at 3-mo intervals thereafter, were tested for N. hughesi using an indirect fluorescent antibody test (IFAT). Furthermore, whole blood and colostrum samples and placentae were tested for the presence of N. hughesi by real-time PCR. The mares' seroprevalen...
Herholz C, Füssel AE, Timoney P, Schwermer H, Bruckner L, Leadon D.The past 10-20 years have seen exponential growth in the volume of trade in horses and equine germplasm; and the extent of global horse movements has increased significantly in the last 4 years. In preparing for the transport of elite Olympic horses to Hong Kong in 2008, it will be very important to be as fully informed as possible of the disease situation in both the exporting and importing country, import and re-entry requirements, as well as having a vaccination strategy to protect against particular diseases. In this context the review describes the equine vector-borne disease situation in...
Kannegieter NJ, Frogley A, Crispe E, Kirkland PD.As part of the control measures of the equine influenza (EI) outbreak, in addition to the strategic use of vaccination to provide buffer zones around infected populations, approval was obtained to vaccinate Thoroughbred racing horses. We review the clinical expression of the disease and virus excretion in a population of racehorses that were exposed to EI approximately 7 days after administration of a single dose of the canarypox-vectored recombinant compared with a similar unvaccinated population of horses at a nearby racetrack. Although this study was undertaken opportunistically and under t...
Whitwell KE.An autopsy study of one dead and two sick hares from an East Anglian estate on which two mares had died of grass sickness revealed that two of the hares were suffering from a polyganglionopathy and alimentary tract changes, remarkably similar to those seen in grass sickness in horses. No such abnormalities were found in two healthy hares from the same locality.
Capomaccio S, Cappelli K, Cook RF, Nardi F, Gifford R, Marenzoni ML, Passamonti F.Equine infectious anaemia virus (EIAV) is classified within the Retroviridae and, like other lentivirus, has the propensity for considerable antigenic variation. An extensive phylogenetic analysis in Bayesian fashion, with significant amounts of new EIAV gag sequence information, revealed a strong geographic compartmentalization clearly related to the phylogeographic history of modern horses, pointing out that New World EIAV strains form a distinct group with a potentially common origin. This evidence suggests that a single founder event may have occurred during the reintroduction of horses to...
Burashev Y, Strochkov V, Sultankulova K, Orynbayev M, Sansyzbay A, Sandybayev N, Nurabayev S, Savitskaya I, Rock DL, Tulman ER.Here, we report the complete genome sequencing of strains A/equine/Kostanay/9/2012(H3N8) and A/equine/LKZ/9/2012(H3N8) of the equine influenza virus belonging to Florida sublineage, clade 2. The strains were isolated in 2012 in the northern and southern regions of Kazakhstan, respectively.
Englund L, Pringle J.Dogs and horses are transported within the European Union for a number of reasons. The transport per se may cause physical problems, exemplified by hyperthermia in dogs and pleuropneumonia in horses, and the stress may reactivate latent infections such as canine herpesvirus-1 and equine herpesvirus-1. Preventive treatments are vital to protect dogs from ticks and mosquitoes transmitting their potentially lethal infectious agents, such as Leishmania donovani infantum, Babesia canis, Ehrlichia canis, and Dirofilaria immitis. However, records show that the travelling dogs are not fully protected ...
An outbreak of Venezuelan equine encephalitis (VEE) that began in northwestern Venezuela in April 1995 has spread westward to the Guajira peninsula and to Colombia (Figure 1), resulting in an estimated minimum of 13,000 cases in humans and an undetermined number of equine deaths. Governments of both countries have initiated efforts to control the spread of this outbreak by quarantining and vaccinating equines and applying insecticides. This report summarizes the ongoing investigation of the outbreak in Colombia.
Gomez DE, Arroyo LG, Lillie B, Weese JS.The objective of this study was to investigate the nasal bacterial microbiota of healthy horses and horses infected with equine herpesvirus 1 (EHV-1). The nasal bacterial microbiota of 10 horses infected with EHV-1 and 11 control horses from a farm experiencing an outbreak was characterized using the Illumina MiSeq platform targeting the V4 region of the 16S ribosomal RNA gene. The nasal bacterial microbiota of healthy horses and EHV-1 horses was significantly different in community membership and structure. Horses shedding EHV-1 had lower bacterial richness ( = 0.002), evenness ( = 0.008), an...
Macdonald SL, Abbas G, Ghafar A, Gauci CG, Bauquier J, El-Hage C, Tennent-Brown B, Wilkes EJA, Beasley A, Jacobson C, Cudmore L, Carrigan P, Hurley J....Cyathostomins are the most common and highly prevalent parasites of horses worldwide. Historically, the control of cyathostomins has mainly relied on the routine use of anthelmintic products. Increasing reports on anthelmintic resistance (AR) in cyathostomins are concerning. A potential method proposed for detecting emerging AR in cyathostomins has been estimating the egg reappearance period (ERP). This paper reviews the data available for the ERP of cyathostomins against the three major classes of anthelmintics, macrocyclic lactones, tetrahydropyrimidines, and benzimidazoles. Published peer-r...
Vesicular stomatitis is an infrequent yet important vesicular disease of cattle, horses, and swine. Periodic outbreaks of this disease in the United States have caused economic losses in cattle herds because of decreased production, movement restrictions, and trade embargoes. Vesicular stomatitis causes clinical signs indistinguishable from those of foot-and-mouth disease. It is of utmost importance that appropriate samples are collected from clinical cases of vesicular disease in cattle and swine so a rapid laboratory diagnosis can be made.
Berlin D, Nasereddin A, Azmi K, Ereqat S, Abdeen Z, Eyal O, Baneth G.Trypanosoma evansi is the cause of surra in horses, camels and other domestic animals. Following the first outbreak of surra in horses and camels in Israel in 2006, a survey of the prevalence of the parasite in the Israeli horse population was conducted using serology, PCR followed by the reverse dot blot (RDB) technique and blood smear microscopy. In total, 614 horses from 7 regions were sampled. The CATT/T. evansi kit was used for serology for all the horses. Horses from the Arava and Dead Sea region, where the first outbreak occurred, were sampled again one year later and both samples were ...
Timoney P.More than 800 premises in eight states in the USA have recently reported cases of vesicular stomatitis in their horses. Here, Peter Timoney, of the Gluck Equine Research Center in Kentucky, discusses this zoonotic disease in more detail.
