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.
Hartnack AK, Van Metre DC, Morley PS.To evaluate the potential association between Salmonella enterica shedding in hospitalized horses and the risk of diarrhea among stablemates, and to characterize gastrointestinal-related illness and death following discharge among horses that shed S. enterica while hospitalized. Methods: Retrospective cohort study [corrected]. Methods: 221 horses (59 that shed S. enterica during hospitalization and 162 that tested negative for S. enterica shedding ≥ 3 times during hospitalization). Methods: Information from medical records (signalment, results of microbial culture of fecal samples, clinical ...
D'Alessandro WB, Humber RA, Luz C.Two isolates of Beauveria bassiana and one of Purpureocillium lilacinum (=Paecilomyces lilacinus) were found infecting Amblyomma cajennense engorged females collected on horses (0.15% infection rate from a total of 1982 specimens) and another two isolates of P. lilacinum and one Metarhizium anisopliae detected in soils (2.1% from 144 samples) collected in typical pasture habitats of this tick in Central Brazil from October 2009 to March 2011. Fungi were isolated from soils with Rhipicephalus sanguineus as surrogate baits. No fungi were found in ticks or soils during the driest months (May to A...
Firestone SM, Christley RM, Ward MP, Dhand NK.Equine influenza is a highly contagious and widespread viral respiratory disease of horses and other equid species, characterised by fever and a harsh dry cough. In 2007, in the first reported outbreak in Australia, the virus spread through the horse populations of two states within 4 months. Most of the geographic spread occurred within the first 10 days and was associated with the movement of infected horses prior to the implementation of movement controls. This study applies social network analysis to describe spread of equine influenza between horse premises infected in the early outbreak ...
Balkaya I, Simsek S.Cystic echinococcosis (CE), caused by hydatid cysts, is a widespread and hazardous disease in humans and animals worldwide. The disease is very common in Turkey, causing serious economic losses and public health problem. In this study, the seroprevalence of equine CE was determined by enzyme-linked immunosorbent assay (ELISA). Methods: Partially purified cyst fluid antigen from sheep hydatid cyst fluid was used as antigen in ELISA. A total of 250 equids consisting of 206 donkeys and 44 horses from various regions of Erzurum province of Eastern Turkey. Results: Anti- Echinococcus granulosus ant...
Antonello AM, Pivoto FL, Camillo G, Braunig P, Sangioni LA, Pompermayer E, Vogel FS.Neospora spp. is a intracellular protozoan phylogenetically closely related to Toxoplasma gondii and Sarcocystis neurona, and it can infect horses leading to the development of reproductive or neurological diseases. We determined the presence of antibodies to Neospora sp. in mares at their parturition time and determine the frequency of vertical transmission in healthy foals to verify the importance of transplacental transmission. The samples were analyzed by indirect immunofluorescence antibody test, showing that seroprevalence in mares is higher than in foals and seropositive mares are likel...
Short MA, Clark CK, Harvey JW, Wenzlow N, Hawkins IK, Allred DR, Knowles DP, Corn JL, Grause JF, Hennager SG, Kitchen DL, Traub-Dargatz JL.A 7-year-old Quarter Horse gelding was hospitalized in Ocala, Fla, because of lethargy, fever, anorexia, and swelling of distal aspects of the limbs. A tentative diagnosis of equine piroplasmosis (EP) was made on the basis of examination of a blood smear. The case was reported to the Florida State Veterinarian, and infection with Babesia equi was confirmed. The subsequent investigation included quarantine and testing of potentially exposed horses for B equi and Babesia caballi infections, tick surveillance, and owner-agent interviews. Results: 210 horses on 25 premises were tested for infectio...
de Vos CJ, Hoek CA, Nodelijk G.African horse sickness (AHS) is a vector-borne viral disease of equines that is transmitted by Culicoides spp. and can have severe consequences for the horse industry in affected territories. A study was performed to assess the risk of introducing AHS virus (AHSV) into the Netherlands (P_AHS) by international equine movements. The goal of this study was to provide more insight into (a) the regions and equine species that contribute most to this risk, (b) the seasonal variation in this risk, and (c) the effectiveness of measures to prevent introduction of AHSV. Countries worldwide were grouped ...
Holý O, Matousková I, Holý V, Koukalová D, Chmelar D.Cronobacter spp. belongs to the family Enterobacteriaceae. It is a motile (peritricha) Gram-negative non-spore forming bacterium. At present, Enterobacter sakazakii is reported as a Cronobacter spp. species with 16 biogroups. It is a ubiquitous organism whose isolation used to be associated with a contaminated powdered infant formula and feed for neonates and infants. Information about the Cronobacter spp. species incidence in the environment, its potential dissemination and its vectors, is very limited. The authors have documented incidence of Cronobacter spp. in the nostril mucous membrane o...
Schemann K, Firestone SM, Taylor MR, Toribio JA, Ward MP, Dhand NK.Following the first ever equine influenza outbreak in Australia in 2007, a study was conducted involving 200 horse owners and managers to determine their perceptions about effectiveness of biosecurity measures and the factors associated with these perceptions. Face-to-face interviews were conducted with horse owners/managers to obtain information about their perceptions of the effectiveness of biosecurity practices, their sources of information about infection control during the outbreak and their horse industry involvement. Two outcome variables were created from horse owners' responses to a ...
Bergström K, Aspan A, Landén A, Johnston C, Grönlund-Andersson U.Methicillin-resistant Staphylococcus aureus (MRSA) in animals is a rare finding in Sweden. In horses, MRSA was first detected in a screening survey in 2007. In 2008, six clinical cases occurred in an equine hospital, indicating an outbreak. Methods: All MRSA isolates detected, 11 spa-type t011 and one t064 (n = 12), in infected horses (n = 10) and screening of horses (n = 2) in Sweden from December 2007 to March 2010 were retrospectively analysed with pulsed-field gel electrophoresis (PFGE) using Cfr9I and ApaI restriction enzymes, to study relationship between the isolates. Medical records of...
Foord AJ, Middleton D, Heine HG.Hendra virus (HeV) is a zoonotic paramyxovirus endemic in Australian Pteropus bats (fruit bats or flying foxes). Although bats appear to be unaffected by the virus, HeV can spread from fruit bats to horses, causing severe disease. Human infection results from close contact with the blood, body fluids and tissues of infected horses. HeV is a biosecurity level 4 (BSL-4) pathogen, with a high case-fatality rate in humans and horses. Current assays for HeV detection require complex instrumentation and are generally time consuming. The aim of this study was to develop a Loop-Mediated Isothermal Amp...
Butler CM, Sloet van Oldruitenborgh-Oosterbaan MM, Stout TA, van der Kolk JH, Wollenberg Lv, Nielen M, Jongejan F, Werners AH, Houwers DJ.Equine piroplasmosis (EP) has not been considered indigenous in The Netherlands. However, following the detection of an apparently indigenous subclinical Babesia caballi infection in a horse on Schouwen-Duiveland (an island in the Zeeland Province), a survey was undertaken between May and September 2010 to assess the prevalence of the causative agents of EP in the South-West of The Netherlands. Blood samples from 300 randomly selected horses were tested for specific antibodies against Theileria equi and B. caballi using an indirect fluorescence antibody test (IFAT), and for parasite DNA using ...
Van den Eede A, Hermans K, Van den Abeele A, Floré K, Dewulf J, Vanderhaeghen W, Crombé F, Butaye P, Gasthuys F, Haesebrouck F, Martens A.Given the significance of methicillin-resistant Staphylococcus aureus (MRSA) infections for both horses and staff in equine veterinary hospitals, protocols are required to minimise the risk of nosocomial transmission, including the screening of the skin and nasal chambers of equine patients for evidence of infection. The objective of this study was to clarify the potential existence and extent of MRSA on the skin of horses requiring long-term hospitalisation (≥ 6 months). Thirty such horses were sampled at eight different locations on their skin and from their nasal chambers. MRSA was isolat...
Barbić L, Lojkić I, Stevanović V, Bedeković T, Starešina V, Lemo N, Lojkić M, Madić J.Equine herpesvirus type 1 (EHV-1) is a worldwide spread pathogen of horses. It can cause abortion, respiratory and neurological disease and consequentially significant economic losses in equine industries. During 2009, two outbreaks of EHV-1 were confirmed in two stud farms in Eastern Croatia. The first outbreak occurred in February following the import of 12 horses from USA, serologically negative to EHV-1 before transport. Four mares aborted in the late stage of pregnancy and one perinatal death was recorded. Other six mares showed clinical signs of myeloencephalopathy with fatal end in four...
Ahmed MO, Williams NJ, Clegg PD, van Velkinburgh JC, Baptiste KE, Bennett M.Antimicrobial-resistant bacteria represent a major threat to human and animal health. We compared equine fecal samples (n=264) from 138 horses from hospital and nonhospital (livery stable and riding school) premises in North West England to determine the prevalence of Escherichia coli, Salmonella, and Campylobacter and rates of antimicrobial-resistant E. coli strains. Campylobacter jejuni was detected only in hospitalized horses (1.1%), and no Salmonella was identified. Data analysis of the horses' management and veterinary treatments (Tx) identified risk factors associated with shedding of an...
Roellig DM, Fang QQ.Anaplasma phagocytophilum is a vector-borne, obligate intracellular bacterium that invades the neutrophils and eosinophils of infected individuals, causing granulocytic anaplasmosis. Equine cases have previously been reported in the United States from California, Florida, and Connecticut, but limited surveillance studies in the Southeast have been conducted. The objective of this study was to determine A. phagocytophilum prevalence in Ixodes scapularis ticks at southeastern U.S. horse-inhabited sites to evaluate the potential risk for equine exposure to A. phagocytophilum-infected ticks in the...
Miszczak F, Legrand L, Balasuriya UB, Ferry-Abitbol B, Zhang J, Hans A, Fortier G, Pronost S, Vabret A.During the summer of 2007, an outbreak of equine viral arteritis (EVA) occurred in Normandy (France). After investigation, a link was suggested between an EAV carrier stallion (A) and the index premise of the outbreak. The full-length nucleotide sequence analysis of a study reference strain (F27) isolated from the lung of a foal revealed a 12,710 nucleotides EAV genome with unique molecular hallmarks in the 5'UTR leader sequence and the ORF1a sequence encoding the non-structural protein 2. The evolution of the viral population in the persistently infected Stallion A was then studied by cloning...
García-Bocanegra I, Jaén-Téllez JA, Napp S, Arenas-Montes A, Fernández-Morente M, Fernández-Molera V, Arenas A.TO THE EDITOR: West Nile virus (WNV) is a member of the genus Flavivirus within the Japanese encephalitis antigenic complex. The enzootic virus cycle involves transmission between avian hosts and ornithophilic mosquitoes, whereas humans and horses are considered dead-end hosts. Given the recent increase of WNV infection in humans and horses in Europe, concern has been raised regarding public and animal health.
Marsh GA, Haining J, Hancock TJ, Robinson R, Foord AJ, Barr JA, Riddell S, Heine HG, White JR, Crameri G, Field HE, Wang LF, Middleton D.Hendra virus (HeV) is a highly pathogenic zoonotic paramyxovirus harbored by Australian flying foxes with sporadic spillovers directly to horses. Although the mode and critical control points of HeV spillover to horses from flying foxes, and the risk for transmission from infected horses to other horses and humans, are poorly understood, we successfully established systemic HeV disease in 3 horses exposed to Hendra virus/Australia/Horse/2008/Redlands by the oronasal route, a plausible route for natural infection. In 2 of the 3 animals, HeV RNA was detected continually in nasal swabs from as ea...
Oura CA, Batten CA, Ivens PA, Balcha M, Alhassan A, Gizaw D, Elharrak M, Jallow DB, Sahle M, Maan N, Mertens PC, Maan S.Prior to the recent outbreak of equine encephalosis in Israel in 2009, equine encephalosis virus (EEV) had only been isolated from equids in South Africa. In this study we show the first evidence for the circulation of EEV beyond South Africa in Ethiopia, Ghana and The Gambia, indicating that EEV is likely to be freely circulating and endemic in East and West Africa. Sequence analysis revealed that the EEV isolate circulating in The Gambia was closely related to an EEV isolate that was isolated from a horse from Israel during the EEV outbreak in 2009, indicating that the two viruses have a com...
Field H, de Jong C, Melville D, Smith C, Smith I, Broos A, Kung YH, McLaughlin A, Zeddeman A.Hendra virus is a recently emerged zoonotic agent in Australia. Since first described in 1994, the virus has spilled from its wildlife reservoir (pteropid fruit bats, or 'flying foxes') on multiple occasions causing equine and human fatalities. We undertook a three-year longitudinal study to detect virus in the urine of free-living flying foxes (a putative route of excretion) to investigate Hendra virus infection dynamics. Pooled urine samples collected off plastic sheets placed beneath roosting flying foxes were screened for Hendra virus genome by quantitative RT-PCR, using a set of primers a...
Bisanzio D, Giacobini M, Bertolotti L, Mosca A, Balbo L, Kitron U, Vazquez-Prokopec GM.West Nile Virus (WNV) transmission in Italy was first reported in 1998 as an equine outbreak near the swamps of Padule di Fucecchio, Tuscany. No other cases were identified during the following decade until 2008, when horse and human outbreaks were reported in Emilia Romagna, North Italy. Since then, WNV outbreaks have occurred annually, spreading from their initial northern foci throughout the country. Following the outbreak in 1998 the Italian public health authority defined a surveillance plan to detect WNV circulation in birds, horses and mosquitoes. By applying spatial statistical analysi...
Leary AJ, Kuenzi AJ, Douglass RJ.We examined the effects of grazing on deer mouse () movements into buildings using passive integrated transponder (PIT) technology and small simulated buildings located on 0.6-ha treatment (grazing) and control (no grazing) plots. Twelve experimental 9-day trials were conducted over the course of the study. During these trials, mouse movements into buildings were monitored during three time periods (each 3 days in length). In the treatment plots these time periods corresponded to pre-grazing, grazing, and post grazing by horses. The number of individual deer mice entering buildings over time d...
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...
Traub-Dargatz J, Kopral C, Wagner B.This study is the first report estimating, on a national basis, the use of various biosecurity practices, singly and in combination, on U.S. equine operations. Use of biosecurity practices is described for operations by risk level, based on reported exposure of resident horses to outside horses during the previous 12 months. In addition, the association between use of various biosecurity practices and use of antibiotics to treat infectious disease in both adult equids and foals is reported. The comparison of these study findings with previously reported data in the literature is limited by the...
Muscatello G.Various challenges face clinicians and farm managers in diagnosing, treating and preventing Rhodococcus equi pneumonia. The use of ultrasound imaging has aided in the early diagnosis of the disease, reducing treatment duration and improving therapeutic outcomes. Antimicrobial resistance in R. equi is an emerging issue that necessitates prudent antimicrobial therapy of diseased foals. Alternative methods of disease transmission, such as contagious foal-to-foal aerosol transmission, may need to be addressed to complement dust reduction environmental strategies and to minimise the overall risk of...
Tennent-Brown B.Although a range of plasma-based products (e.g., cryoprecipitate, albumin, platelet-rich plasma, individual coagulation factors) are available to human physicians, equine veterinarians are largely restricted to using whole blood, frozen plasma, and fresh frozen plasma for transfusions. The indications for frozen or fresh frozen plasma in human medicine are relatively limited, and there is little evidence supporting the efficacy of these products in many cases. Furthermore, many human physicians have concerns regarding disease transmission and anaphylactic reactions after administration of any ...
Muscatello G.Rhodococcus equi pneumonia is a worldwide infectious disease of major concern to the equine breeding industry. The disease typically manifests in foals as pyogranulomatous bronchopneumonia, resulting in significant morbidity and mortality. Inhalation of aerosolised virulent R. equi from the environment and intracellular replication within alveolar macrophages are essential components of the pathogenesis of R. equi pneumonia in the foal. Recently documented evidence of airborne transmission between foals indicates the potential for an alternative contagious route of disease transmission. In the...
Hurni JI, Kaiser-Thom S, Gerber V, Keller JE, Collaud A, Fernandez J, Schwendener S, Perreten V.A total of 100 nasal swabs were collected from healthy horses in Switzerland between January 2020 and August 2020. The samples were taken from horses at 40 different stables in 12 different cantons and screened for both methicillin-resistant (MRSA) and methicillin-susceptible S. aureus (MSSA) using selective agar plates. S. aureus were tested for antibiotic susceptibility by measurement of the minimal inhibitory concentration (MIC) and for virulence factors, antibiotic resistance genes and phylogenetic characteristics using whole genome sequence analysis. Ten horses were found to be positiv...
Miley KM, Downs J, Beeman SP, Unnasch TR.Eastern equine encephalitis virus (EEEV), an Alphavirus from family Togaviridae, is a highly pathogenic arbovirus affecting the eastern United States, especially Florida. Effects of the Southern Oscillation Index (SOI), precipitation, and cooling degree days on EEEV horse case data in Florida from 2004 to 2018 were modeled using distributed lag nonlinear models (DLNMs). The analysis was conducted at statewide and regional scales. DLNMs were used to model potential delayed effects of the covariates on monthly counts of horse cases. Both models confirmed a seasonal trend in EEEV transmission and...
Zimmerli U, Thür B.Equine infectious anaemia (EIA) is a sporadic viral disease in many countries. Every single case has, however, a dramatic impact: infected animals have to be put down, and quarantine restrictions on horse movements lasting three months lead to substantial economic losses. In Switzerland, the mandatory notification was introduced in 1994 in order to facilitate international traffic. A year later, the "new" Ordinance on epizootics of 1995 classified EIA as a "disease to be eradicated". An infected polo horse in the canton of Argovia in summer 2017 thus represented Switzerland's first official ca...
Gardner RB, Hart KA, Stokol T, Divers TJ, Flaminio MJ.A 5-week-old Fell Pony colt was examined for fever, lethargy, and anemia. The colt had been lethargic for 1 week before examination, had continued to nurse, had a temperature of 104°F (40°C), and was treated with ceftiofur (5 mg/kg IM q12h). Approximately 36 hours before examination, the colt developed watery diarrhea. Blood work performed by the referring veterinarian on the day of admission revealed a PCV of 10%.
Zimmerli U, Herholz C, Schwermer H, Hofmann M, Griot C.African horse sickness (AHS) of equines is partly transmitted by the same culicoides species as Bluetongue (BT) disease in even-toed ungulates. Horses normally get seriously sick, with a high case fatality rate. Equine Encephalosis is another, but less-known viral disease of equines, caused by viruses of the same genus as BT and AHS. Like BT of serotype 8 in 2006, both diseases could theoretically be introduced to Europe anytime and spread rapidly then. After the lessons learnt from the most recent bluetongue outbreaks in Europe, the regulations and AHS-contingency plans in force must be updat...
Broaddus CC, Balasuriya UB, Timoney PJ, White JL, Makloski C, Torrisi K, Payton M, Holyoak GR.The objective was to evaluate the potential risks associated with embryo transfer from mares bred with equine arteritis virus (EAV) infective semen. Twenty-six mares were embryo donors, whereas 18 unvaccinated and EAV antibody seronegative mares were embryo recipients. Of the 26 donor mares, 15 were unvaccinated and seronegative for antibodies to EAV and 11 were vaccinated for the first time with a commercially available modified live virus vaccine against EVA before breeding and subsequent embryo transfer. All donor mares were bred with EAV-infective semen from a stallion persistently infecte...
Carroll JF, Schmidtmann ET.The American dog tick, Dermacentor variabilis (Say), was the only ixodid tick found feeding on horses in Montgomery County, Md., from May to August. Average tick burdens were low (less than one tick per horse per week), but >80% of 33 horses examined weekly were exposed to tick feeding during the summer. Of the 98 ticks collected, 78% were attached to the tail and 12% were present in the mane. Host-seeking adult D. variabilis were active on vegetation in pastures from May to early August, with most specimens along hedgerows, woods margins, and horse paths.
Boles CL, Raker CW, Wheat JF.An abnormality of the epiglottis and arytenoepiglottic folds that caused epiglottic entrapment was diagnosed in 21 horses. Until recently, this entrapment was poorly understood. Definitive diagnosis of epiglottic entrapment can be made only by endoscopic examination of the epiglottis, arytenoepiglottic folds, and soft palate to differentiate the abnormality from dorsal displacement of the soft palate. Dorsal displacement of the soft palate is often associated with entrapped epiglottis. Epiglottic deformity, especially hypoplasia, is often associated with the entrapment. The abnormality was det...
Nixon J.Equine consultant, Jane Nixon, attended the first equine biosecurity course at the British Racing School in November last year, organised by Whorl Publishing. Here, she reports on some of the issues covered.
Ndebé MMF, Mouiche MMM, Moffo F, Poueme RNS, Awah-Ndukum J.African horse sickness (AHS), a highly fatal arbovirosis of equines is endemic in sub-Saharan Africa. However, its epidemiology is poorly known in Cameroon. This study aimed to investigate the prevalence profile and risk factors of African horse sickness in Cameroon. Horse sera were subjected to the ELISA blocking test for the determination of antibodies against African horse sickness virus, and positive samples were submitted to capture ELISA to determine the presence of antigens. Potential risk factors associated with AHS were assessed based on the information collected in the field. The chi...
McCluskey BJ, Pelzel-McCluskey AM, Creekmore L, Schiltz J.Vesicular stomatitis is a viral disease primarily affecting horses and cattle when it occurs in the United States. Outbreaks in the southwestern United States occur sporadically, with initial cases typically occurring in Texas, New Mexico, or Arizona and subsequent cases occurring in a northward progression. The viruses causing vesicular stomatitis can be transmitted by direct contact of lesioned animals with other susceptible animals, but transmission is primarily through arthropod vectors. In 2012, an outbreak of vesicular stomatitis in the United States occurred that was caused by Vesicular...
Carr EA.The purpose of this article is to provide a quick reference for field triage of the sick neonatal foal. Therefore, information is focused toward diagnostics and treatments that can be performed in the field. When evaluating a weak, recumbent, or lethargic foal on a farm, it is often difficult to make a definitive diagnosis. Therefore, the approach should be to treat what is treatable and prevent what is preventable. In many cases, the goal will be to stabilize a foal before referral to a tertiary care facility where more intensive and continuous treatment can be performed.