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.
Powell DG, Watkins KL, Li PH, Shortridge KF.Equine-2 influenza virus A (H3N8) infection occurred among vaccinated thoroughbred horses in Hong Kong during November and December 1992. The outbreak was unique in that it occurred among a large population stabled under intensive conditions. It resulted in the postponement of seven race meetings over a period of 32 days. The outbreak originated after the importation of horses 25 to 32 days before any clinical signs were reported. Vaccination did not prevent 75 per cent of the population from becoming infected, and half the infected horses developed clinical signs. Vaccination did, however, co...
Pfeifer Barbosa I, Böse R, Peymann B, Friedhoff KT.Epidemiological studies of Babesia equi and B. caballi were undertaken in a herd of 120 pastured horses in Rio de Janeiro, Brazil. The area where the horses were held was shown to be highly endemic for both Babesia spp., i.e. the prevalence of B. equi antibodies in horses aged 6 months or older ranged from 90.6% to 100% as determined by the immunofluorescence antibody (IFA) test, and the prevalence of B. caballi antibodies as determined by Western blot ranged from 59.4% to 65.5%. From the herd, 20 foals and their dams were selected to estimate the degree of tick infestation and the foals were ...
Davis EO, Curran GE, Hetherington WT, Norris DA, Wise GA, Roth IJ, SeaWright AA, Bryden WL.Flood plain staggers, a corynetoxicosis of grazing livestock, occurred on flood plains of the Darling river in northern New South Wales between spring 1990 and autumn 1991, associated with the grazing of Agrostis avenacea with diseased inflorescences. Over this period 1722 cattle, 2466 sheep and 11 horses died on 31 farms. Clinical signs were similar in sheep and cattle, being characterised by intermittent episodes of cerebral convulsion superimposed on varying degrees of cerebellar dysfunction. Pathological changes were variable and non-specific, principally reflecting trauma and the generali...
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 ...
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...
Borges ALdSB, Aymée L, Lilenbaum W, Di Azevedo MIN.Leptospirosis, caused by spp. infection, is a globally significant zoonotic disease that affects a wide range of animals. Although renal colonization is well-documented, genital infection by leptospires remained less explored for decades, despite its impact on reproduction. Evidence suggests that genital infection occurs as a primary condition rather than secondary to renal colonization, particularly in cattle suffering from bovine genital leptospirosis (BGL), linked to chronic infections by strains of the Sejroe serogroup. In horses, a similar condition is suggested to be associated with str...
Nayel M, Kasem S, Fukushi N, El-Habashi N, Elsify A, Salama A, Hassan H, Yanai T, Ohya K, Fukushi H.Equine herpesvirus type 1 (EHV-1) causes rhinopneumonitis, abortion, and neurological outbreaks (equine herpesvirus myeloencephalopathy, EHM) in horses. EHV-1 also causes lethal encephalitis in small laboratory animals such as mice and hamsters experimentally. EHV-1 ORF76 is a homolog of HSV-1 US9, which is a herpesvirus kinase. Starting with an EHV-1 bacterial artificial chromosome clone of neuropathogenic strain Ab4p (pAb4p BAC), we constructed an ORF76 deletion mutant (Ab4p∆ORF76) by replacing ORF76 with the rpsLneo gene. Deletion of ORF76 had no influence on replication, cell-to-cell spr...
Kälin D, Becsek A, Stürmer H, Bachofen C, Siegrist D, Jonsdottir HR, Schoster A.(1) Background: Horses infected by a tick-borne encephalitis virus (TBEV) can develop clinically apparent infections. In humans, vaccination is the most effective preventive measure, while a vaccine is not available for horses. The objective of this study was to describe the immune response in horses after a TBEV vaccination with a human vaccine. (2) Materials and Methods: Seven healthy horses were randomised to a treatment or a control group in a stratified fashion based on TBEV-IgG concentrations on day -4. The treatment group ( = 4) was intramuscularly vaccinated using an inactivated human ...
Costa MVD, Rodrigues GD, Lima HIL, Krolow TK, Krüger RF.Tabanidae (Diptera), popularly known as horse flies, is an important vector group. This is the first study to ascertain the abundance and diversity of horse flies in horses at the cerrado biome of the state of Tocantins, Brazil. Collecting took place in typical Cerrado, and sampling occurred in the dry and rainy seasons. The horseflies were collected from horses using an entomological net. A total of 249 individuals were collected and spread over 25 species. The prevalent species were Stypommisa aripuana (25.8%) and Catachlorops rufescens (6.4%), in the dry period, and Fidena lissorhina (22.5%...
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 ...
Ichikawa Y, Borjigin L, Enkhtuul B, Khurtsbaatar O, Aoshima K, Kobayashi A, Batbaatar V, Kimura T.Glanders, a highly contagious and often fatal disease affecting equids, is caused by Burkholderia mallei. Although sporadic cases of equine glanders have recently been documented in Mongolia, genome sequencing and molecular studies of the bacteria within this region are lacking. This study provided the first molecular characterization of B. mallei isolated from four native Mongolian horses from two different provinces in 2019 and 2022 by applying whole-genome sequencing with two SNP types (previously developed genotyping with 15 SNP markers that provide global coverage of the B. mallei populat...
Muroni G, Serra E, Biggio GP, Sanna D, Cherchi R, Taras A, Appino S, Foxi C, Masala G, Loi F, Chisu V.The members of the family are important pathogens that infect a wide range of vertebrate hosts, including humans. Among them, , historically considered as an avian agent, has recently been identified in livestock, primarily sheep and cattle, but also in horses, with the infection being linked to reproductive disorders, such as abortion, absorption of embryos, stillbirth, and the birth of weak foals. Much less is known about chlamydial infections in the Sardinian equine population. This study aimed to identify the chlamydial diversity in genital samples from asymptomatic Sardinian horses. Howe...
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 ...
Onasanya AE, El-Hage C, Diaz-Méndez A, Vaz PK, Legione AR, Devlin JM, Hartley CA.Equid gammaherpesvirus 5 (EHV5) is closely related to equid gammaherpesvirus 2 (EHV2). Detection of EHV5 is frequent in horse populations worldwide, but it is often without a clear and significant clinical impact. Infection in horses can often present as subclinical disease; however, it has been associated with respiratory disease, including equine multinodular pulmonary fibrosis (EMPF). Genetic heterogeneity within small regions of the EHV5 glycoprotein B (gB) sequences have been reported and multiple genotypes of this virus have been identified within individual horses, but full genome seque...
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...
The emergence of new strains in the Mediterranean region poses a challenge for both veterinary medicine and public health, as it can lead to more complex diagnostic and treatment strategies. Species related to and , two important tick-borne pathogens, have been reported in several Mediterranean countries. However, the data on their presence in Sardinia remain limited. This study aimed to such as or , in Using various molecular approaches targeting the and genes, the results confirm the presence of () and reveal the emergence of () and an -like strain, designated as -like 2, in Sardi...
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.
Zahradnik E, Sander I, Lotz A, Liebers V, Thullner I, Tacke S, Raulf M.The study aimed to determine the allergen, endotoxin and β-(1,3)-glucan concentrations at various areas on a university campus of veterinary medicine. Methods: Dust samples were collected four times a year for three years using electrostatic dust collectors (EDC) at 25 different locations on a campus of veterinary medicine and in laboratories of inorganic chemistry as a control area representing animal-free environment. Major animal allergens from dog, cat, horse, cattle and mouse, domestic mite (DM) allergens, and β-(1,3)-glucan were measured using enzyme immunoassays and endotoxin using th...
Shen DT, Gorham JR, Jones RH, Crawford TB.Laboratory-colonized mosquitoes, Culex tarsalis, aedes aegypti, Culiseta inornata, and Anopheles free-borni, and the biting gnat, Culicoides variipennis, were exposed to equine infectious anemia virus. Exposure to the virus was by intrathoracic inoculation for mosquitoes and by oral ingestion of an infective blood meal through a membrane for C variipennis. After various intervals, groups of 15 to 20 insects were homogenized and inoculated into susceptible ponies. Positive immunodiffusion test results were used as criterion for equine infectious anemia infection in ponies. Virus was not detecte...
