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.
Wood JL, Chirnside ED, Mumford JA, Higgins AJ.Equine viral arteritis was diagnosed for the first time in the United Kingdom in 1993. The outbreak began on a non-thoroughbred stud in south Nottinghamshire and spread to five other premises through chilled semen used for artificial insemination and from acutely and subclinically infected mares returning home. The outbreak was contained on these six premises by means of voluntary movement restrictions. The most commonly observed clinical signs were typical: pyrexia with depression, and conjunctivitis with periorbital oedema; nasal discharge, and oedema of the distal limbs, prepuce and mammary...
Stiller D, Coan ME.This brief review focuses first on several epidemiologically relevant aspects of anaplasmosis, including: (1) the role of male ticks as intrastadial, biological vectors of Anaplasma through interhost transfer; (2) the application of molecular diagnostic assays in assessing tick vector competence and evaluating the role of chronically infected carrier cattle as sources of Anaplasma marginale infection in vector ticks; (3) opportunities provided by a recently developed in vitro tick feeding system in quantitating studies of tick-hemoparasite-host interactions. Lastly, current knowledge of the st...
Walker RL, de Peralta TL, Villanueva MR, Snipes KP, Madigan JE, Hird DW, Kasten RW.Isolates of Salmonella choleraesuis serotype ohio (S. ohio) recovered during an outbreak of equine neonatal salmonellosis on a Thoroughbred farm were compared with isolates of the same serotype from various animal, feed and environmental sources. Biochemical profiles, antimicrobial susceptibility patterns, phage susceptibility, plasmid profiles, restriction endonuclease analysis and ribotyping were used to compare relatedness of the strains. A total of 46 outbreak and non-outbreak associated isolates of S. ohio were studied. Differences in antimicrobial susceptibility patterns, phage susceptib...
Mellor PS, Boorman J.African horse sickness virus (AHSV) and bluetongue virus (BTV) are dsRNA viruses within the genus Orbivirus. Both are able to cause non-contagious, infectious arthropod-borne diseases in their respective vertebrate hosts. AHSV infects equines and occasionally dogs, whereas BTV replicates in ruminants. The disease caused by AHSV is usually at its most severe in horses, whereas certain breeds of sheep are particularly sensitive to BTV infection. AHSV is endemic in sub-Saharan Africa but periodically makes brief excursions beyond this area. BTV occurs much more widely and can be found in a band a...
Van der Poel WH, Langedijk JP, Kramps JA, Middel WG, Brand A, Van Oirschot JT.To study the role of non-bovine species in the epidemiology of bovine respiratory syncytial virus (RSV) infections, sera obtained from 9 non-bovine animal species and from humans were examined for bovine RSV specific antibodies. Sera were mainly from animals and humans which had been in contact with cattle. Forty sera of each species were tested in an RSV specific whole virus ELISA as well as in a peptide based ELISA, that was developed to measure antibodies specific for bovine RSV. Antibodies directed against RSV were detected in over 50% of sera obtained from sheep, goat, cattle and human be...
Komar N, Spielman A.The 20th century emergence in Massachusetts of zoonotic eastern encephalitis was interpreted in terms of recorded environmental change. The main mosquito vector of the infection, Cs. melanura, appears to have been scarce in eastern North America before the 1930s. Its relative scarcity resulted from destruction of the swamps that had been lumbered or drained for farming in the 18th and 19th centuries. When swamps matured once again early in the 1900s, the formation of subsurface pools of water beneath mature trees would have increased the availability of breeding sites for this mosquito. Transm...
Barnard BJ, Bengis R, Keet D, Dekker EH.The viraemic period of African horsesickness is significantly longer in experimentally infected zebra than in horses. The virus could be isolated 40 d post-infection from blood and 48 d post-infection from spleen. The introduction of zebra into African horsesickness-free countries should therefore be considered carefully, and preferably be restricted to serologically negative zebra.
Khoury C, Manilla G, Maroli M.The following 13 species of ticks, belonging to Ixodidae family, were recorded in Italy on horse (Equus caballus) since 1931: Ixodes ricinus, I. gibbosus, Haemaphysalis inermis, H. parva, H. punctata, H. sulcata, Dermacentor marginatus, Rhipicephalus sanguineus, Rh. bursa, Rh. turanicus, Hyalomma marginatum, Hy. detritum, Boophilus annulatus. The regional distribution and the role of the species in the transmission of pathogens are reported.
Braverman Y.The biology, veterinary importance and control of certain Nematocera are described and discussed. Culicoides spp. (family Ceratopogonidae) transmit the arboviruses of bluetongue (BT), African horse sickness (AHS), bovine ephemeral fever (BEF) and Akabane. Some other arboviruses have been isolated from these species, while fowl pox has been transmitted experimentally by Culicoides. These insects are vectors of the parasitic protozoans Leucocytozoon caulleryi and Haemoproteus nettionis, and the parasitic nematodes Onchocerca gutturosa, O. gibsoni and O. cervicalis. They also cause recurrent summ...
Franke CR, Greiner M, Mehlitz D.The prevalence of Mal de Cadeiras--Portuguese for Trypanosoma (T.) evansi infections in horses--as well as the prevalence of T.evansi infections in cattle, dogs and free-ranging capybaras (Hydrochaeris hydrochaeris) was investigated in Pantanal de Poconé (Mato Grosso, Brazil). In 0.3, 8.6 and 8.0% of the horses, dogs and capybaras, respectively, infection was detected using standard parasitological methods. A seroprevalence of 4.1, 2.3, 7.1 and 22.0% was found in horses, cattle, dogs and capybaras, respectively, using an enzyme-linked immunosorbent assay for the detection of T.evansi antigen ...
Comer JA, Irby WS, Kavanaugh DM.Hosts of Lutzomyia shannoni Dyar, a suspected biological vector of the New Jersey serotype of vesicular stomatitis (VSNJ) virus, were determined using an indirect enzyme-linked immunosorbent assay (ELISA) of 333 blood-fed female sandflies collected from their diurnal resting shelters on Ossabaw Island, Georgia, U.S.A. Sandflies had fed primarily on white-tailed deer (Odocoileus virginianus) (81%) and to a lesser extent on feral swine (Sus scrofa) (16%), two species of host infected annually with VSNJ. Other hosts were raccoons (Procyon lotor) and horses (Equus caballus) or donkeys (E. asinus),...
Ciarlet M, Reggeti F, Piña CI, Liprandi F.Two group A rotavirus strains isolated from diarrheic foals in Venezuela were classified as belonging to G14 serotype by cross-neutralization tests and on the basis of the homology of the sequenced VP7 gene. This report confirms that rotavirus strains of G14 serotype specificity circulate among equine populations.
Zientara S.After a brief historical account of the outbreak of infectious arteritis of horses which occurred in 1984 in Kentucky (United States of America), the author reports on the present state of knowledge concerning the organisation of the genome of the virus. Clinical signs of the disease are described, as well as modes and routes of transmission. Finally, currently-available vaccination procedures are discussed and their value is assessed.
Rawlings P, Mellor PS.The presence at different latitudes and the seasonal distribution of two known or potential vectors of African horse sickness (AHS) virus--Culicoides imicola and C. obsoletus--were investigated in the Iberian peninsula using light trap collections. Culicoides imicola was present as far north as 41 degrees N but not at 43 degrees N (Asturias, Spain), whereas C. obsoletus was found at all latitudes. In the northern part of the distribution of C. imicola, adults of this species were present for only a few months of the year, but adults were continually present further south. Culicoides obsoletus ...
Crans WJ, Caccamise DF, McNelly JR.Eastern equine encephalomyelitis virus (EEEV) is perpetuated in eastern North America in a mosquito-wild bird maintenance cycle that involves Culiseta melanura (Coquillett) as the principal enzootic vector and passerine birds as the primary amplifying hosts. We examined the role of birds in the EEEV cycle at a site in southern New Jersey where EEEV cycles annually at high levels. Birds and mosquitoes were sampled during three epiornitics and one season of limited virus activity. We examined antibody prevalence in birds in relation to eight physical and natural history characteristics. Our goal...
Mellor PS.African horse sickness (AHS) virus causes a non-contagious, infectious, arthropod-borne disease of equines and is enzootic in sub-Saharan Africa. The major vectors are species of Culicoides but mosquitoes and ticks may be involved. Periodically the virus makes excursions beyond its enzootic zones but until recently has not been able to maintain itself outside these areas for more than 2-3 consecutive years. This is probably due to a number of factors including the absence of a long term vertebrate reservoir, the prevalence and seasonal incidence of the vectors and the efficiency of control mea...
Monzon CM, Jara GA, Hoyos CB.The usefulness of the direct agglutination test (DA) to diagnose Mal de Caderas disease was evaluated. Forty four sera samples from two lots of horses with natural T. evansi infection (Lot 1 and Lot 2) were used. Thirteen (81.2%) of sixteen horses in which parasites were isolated gave positive agglutination titres (> or = 1:512) in the DA test. Treatment of these positive sera with 2-mercaptoethanol drops three to eight dilutions the agglutination titres in twelve samples (92%), showing the IgM nature of these antibodies. The DA test was also positive in seventeen of twenty eight horses in ...
Lyons ET, Tolliver SC, Stamper S, Drudge JH, Granstrom DE, Collins SS.Studies were conducted on transmission of natural infections of several species of internal parasites in horses born and kept on the same pasture on a farm in central Kentucky. Data for the first year (1989) of a 4 year study on this farm have been published recently. The present research represents the second (1990), third (1991), and fourth (1992) years of the investigation. The number of animals (n = 28) examined varied from eight born in 1990 to ten each born in 1991 and 1992. For each year, examination was made of one horse per month, beginning in June of the year of birth and extending t...
Palmer JE, Benson CE.Eight normal ponies placed in direct contact with ponies experimentally infected with Ehrlichia risticii for 30 to 90 days did not develop signs of Potomac horse fever. They also did not seroconvert, and they remained susceptible to IV infection. One of 8 ponies that were force fed fresh feces from infected ponies while in direct contact with ponies experimentally infected with E. risticii developed Potomac horse fever and seroconverted. The other 7 remained asymptomatic, did not seroconvert, and were susceptible to IV infection. Six of 9 ponies inoculated with E. risticii via nasogastric intu...
Turell MJ, Beaman JR, Neely GW.The vector competence of Aedes taeniorhynchus (Wiedemann) and four strains of Aedes albopictus (Skuse) was assessed for eastern equine encephalitis (EEE) virus isolated from Ae. albopictus collected in Polk County, Florida. Both species became infected with and transmitted EEE virus by bite after feeding on 1-d-old chicks that had been inoculated with EEE virus (viremia = 10(10.1) plaque-forming units [PFU] per ml of blood). However, when fed on an older chick with a lower viremia (viremia = 10(6.1) PFU per ml of blood), Ae. albopictus was significantly more susceptible to infection (90%, n = ...
Reid SW, Gettinby G, Fowler JN, Ikin P.An epidemiological study of equine sarcoid in a population of 4126 donkeys showed that the peak incidence of the disease was 15.2 cases per 100 animal-years and occurred in animals in their fourth year of life. The crude incidence of the disease was 0.6 cases per 100 animal-years. The disease occurred most frequently in younger, male animals during their first five years in the population. The lesions were observed most commonly in the paragenital region. Pre-entry quarantine procedures did not appear to play a significant role in the spread of the disease but there was an indication that clos...
Cabrera G, Cabezas C, Estay-Olea D, Stoore C, Baquedano MS, Paredes R, Hidalgo C.Liver fluke infection, caused by the trematode Fasciola hepatica, is a parasitic zoonotic disease affecting various mammals, including humans, and has significant implications for public, animal, and ecosystem health. This study provides the first genetic characterization of F. hepatica in Chile, focusing on the complete mitochondrial gene cox1. Samples were collected from two different host species: cattle and horses. Our findings revealed that 70 % of detected haplotypes were found in either cattle or horses, which coincides with their geographical origin. Interestingly, the use of full-len...
Morris RE, Doherty S, Oltmanns MH, Sapp MR, Wells K, Patel HR.To present a rarely reported systemic infection with (), transmitted from a horse, and to describe successful treatment when complicated by endogenous endophthalmitis. Unassigned: We diagnosed suspected septicemia presenting as loss of vision in the right eye of an otherwise healthy polo player/horse trainer. He received immediate intravenous antibiotics and three vitrectomies with two intravitreal antibiotic injections during the first week, to cure infection and subsequent retinal detachment. Blood and initial vitreous cultures rapidly grew The septicemia was quickly controlled by systemi...
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...
da Gama BC, Martins TF, Labruna MB, Vieira RFDC, de Almeida JC.Studies on ticks of public health concern in equine husbandry are scarce in the Northeastern region of Brazil. This study aimed to investigate the presence of ticks on horses in the State of Alagoas, which is classified as a silent area for human rickettsiosis. Unassigned: Ticks infesting horses were collected using anatomical tweezers or a commercial hook and kept in ethanol-labeled tubes for taxonomic identification. Unassigned: A total of 2,238 ticks were found. Ticks were identified as 2,215 (98.89%, 95% CI: 98.41-99.28) , 19 (0.98%, 95% CI: 0.05-1.38) , and 4 (0.18%; 95% CI: 0.007-0.46) ....
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;...
Hedberg Alm Y, Tydén E, Martin F, Lernå J, Halvarsson P.Selective anthelmintic treatment, advocated due to evolving anthelmintic resistance, has been associated with an increase in Strongylus vulgaris prevalence. Reverting to routine interval anthelmintic treatments is not viable and therefore, identifying other management factors correlated with S. vulgaris infection is vital. Objective: To investigate possible risk factors associated with the presence of S. vulgaris infection in resident horses on Swedish horse establishments. Methods: Internet-based questionnaire survey. Methods: A questionnaire, created using the internet-based survey platform ...
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...
Grabatin M, Fux R, Zablotski Y, Goehring LS, Witte TS.Contagious equine metritis (CEM) is caused by Taylorella equigenitalis. It is a venereal disease that is detected in some breeds more than others and can cause temporary infertility with substantial costs for regular testing, sanitation and retesting. There was a perceived increase in T. equigenitalis-positive cases in Icelandic intact males where natural cover is common. Objective: We aimed to investigate the prevalence of T. equigenitalis in Icelandic intact males and compare to draught horse and Haflinger intact males. We hypothesised that prevalence of T. equigenitalis is higher in Iceland...
Carey KJ, Smith I, Barr J, Caruso S, Au GG, Hartley CA, Bailey KE, Perriam W, Broder CC, Gilkerson JR.Hendra virus (HeV) is lethal to horses and a zoonotic threat to humans in Australia, causing severe neurological and/or respiratory disease with high mortality. An equine vaccine has been available since 2012. Foals acquire antibodies from their dams by ingesting colostrum after parturition, therefore it is assumed that foals of mares vaccinated against HeV will have passive HeV antibodies circulating during the first several months of life until they are actively vaccinated. However, no studies have yet examined passive or active immunity against HeV in foals. Here, we investigated anti-HeV a...
Gonzalez-Obando J, Zuluaga-Cabrera A, Moreno I, Úsuga J, Ciuderis K, Forero JE, Diaz A, Rojas-Arbeláez C, Hernández-Ortiz JP, Ruiz-Saenz J.Equine influenza is a viral disease caused by the equine influenza virus (EIV), and according to the WOAH, it is mandatory to report these infections. In Latin America and Colombia, EIV risk factors have not been analyzed. The objective of this research is to perform an epidemiological and molecular analysis of the EIV in horses with respiratory symptoms from 2020 to 2023 in Colombia. Molecular EIV detection was performed using RT-qPCR and nanopore sequencing. A risk analysis was also performed via the GEE method. A total of 188 equines with EIV respiratory symptoms were recruited. The positiv...
Chagoya-Fuentes JL, Gaona-López J, Hernández-Carbajal GR, Torres-Guerrero H, Lammoglia-Villagómez MA, Huerta-Peña J, Pérez-Brígido CD....A clinical case of an adult horse with invasive, ulcerative, proliferative, pyogranulomatous disease of the skin (tumor) in the shoulder region is presented. The mass had a granulomatous and crater-shaped appearance, with serosanguinous discharge and the presence of fistulas with caseous material. The tumor was removed by surgery and sent to the laboratory for diagnosis. Histopathology was performed using Grocott-Gomori methenamine silver stain. The presence of necrotic material, fibrosis, infiltrated cells, and brown-colored hyphae, characteristic of members of the genus Pythium, were observe...
Higgins C, Cohen ND, Slovis N, Boersma M, Gaonkar PP, Golden DR, Huber L.Antimicrobial residues excreted in the environment following antimicrobial treatment enhance resistant microbial communities in the environment and have long-term effects on the selection and maintenance of antimicrobial resistance genes (AMRGs). In this study, we focused on understanding the impact of antimicrobial use on antimicrobial residue pollution and antimicrobial resistance (AMR) in the environment of horse-breeding farms. is an ideal microbe to study these associations because it lives naturally in the soil, exchanges AMRGs with other bacteria in the environment, and can cause disea...
Elliott S, Olufemi OT, Daly JM.Vaccines against equine influenza have been available since the late 1960s, but outbreaks continue to occur periodically, affecting both vaccinated and unvaccinated animals. The aim of this study was to systematically evaluate the efficacy of vaccines against influenza A virus in horses (equine IAV). For this, PubMed, CAB abstracts, and Web of Science were searched for controlled trials of equine IAV vaccines published up to December 2020. Forty-three articles reporting equine IAV vaccination and challenge studies in previously naïve equids using an appropriate comparison group were included ...
Nakase M, Thapa J, Batbaatar V, Khurtsbaatar O, Enkhtuul B, Unenbat J, Lkham B, Fujita S, Koshikawa A, Tuanyok A, Saechan V, Higashi H, Hayashida K....Glanders and melioidosis are contagious zoonotic diseases caused by Burkholderia mallei and B. pseudomallei, respectively. Bacterial isolation and polymerase chain reaction (PCR) have been used to detect these bacteria in animals suspected of infection; however, both methods require skilled experimental techniques and expensive equipment. These obstacles make it difficult to diagnose B. mallei and B. pseudomallei infections in areas where reagents and equipment are difficult to procure. To solve this problem, we developed an easy and ready-to-use dried-format diagnostic tool based on loop-medi...
Yuen NKY, Harrison JJ, Wang ASW, McMahon IE, Habarugira G, Coyle MP, Bielefeldt-Ohmann H.An incursion and outbreak of Japanese encephalitis virus (JEV) was reported in Australia in 2021 and 2022, respectively. There was speculation that JEV may have been circulating in Australia unknowingly prior to the detection. In this study, we determined sero-prevalence and transmission of West Nile virus (WNV), Murray Valley encephalitis virus (MVEV) and JEV, prior to and post JEV incursion in a sentinel equine population in south-east Queensland (SEQ), Australia, using blocking ELISAs (screening test) and virus neutralisation test (confirmatory). Serum samples collected between 2018 and 202...
Cutarelli A, De Falco F, Serpe F, Izzo S, Fusco G, Catoi C, Roperto S.BPV1, BPV2, BPV13, and BPV14 are all genotypes of bovine delta papillomaviruses (δPV), of which the first three cause infections in horses and are associated with equine sarcoids. However, BPV14 infection has never been reported in equine species. In this study, we examined 58 fresh and thawed commercial semen samples from healthy stallions. In 34 (58.6%), bovine δPV DNA was detected and quantified using droplet digital polymerase chain reaction (ddPCR). Real time quantitative PCR (qPCR) was able to identify bovine δPV DNA in 5 samples (8.6%). Of the BPV-infected semen samples, 15 were posi...
Hrala M, Andrla P, Bosák J, Fedrová P, Mugutdinov A, Karpíšková R, Nedbalcová K, Raichová J, Faldyna M, Hořín P, Šmajs D.Taylorella equigenitalis is the causative agent of sexually transmitted contagious equine metritis. Infections manifest as cervicitis, vaginitis and endometritis and cause temporary infertility and miscarriages of mares. While previous studies have analyzed this organism for various parameters, the evolutionary dynamics of this pathogen, including the emergence of antibiotic resistance, remains unresolved. The aim of this study was to isolate contemporary strains, determine their genome sequences, evaluate their antibiotic resistance and compare them with other strains. We determined nine comp...
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...
Hoff GL, Bigler WJ, Buff EE, Beck E.Research and surveillance programs relating to the occurrence and distribution of western equine encephalomyelitis virus in Florida, conducted between 1955 and 1976, suggest that the virus is (1) an endemic arbordae, (2) transmitted in a continuous cycle throughout the year by Culiseta melanura mosquitoes, and (3) restricted to fresh water swamps and waterways in central, north, and northwest Florida.
