Infectious diseases in horses encompass a range of illnesses caused by bacteria, viruses, fungi, or parasites. These diseases can affect various systems within the equine body, leading to symptoms that range from mild discomfort to severe systemic illness. Common infectious diseases in horses include equine influenza, strangles, equine herpesvirus, and West Nile virus. These diseases can be transmitted through direct contact with infected animals, contaminated surfaces, or vectors such as insects. Understanding the mechanisms of transmission, pathogenesis, and immune response is essential for effective prevention and control. This page compiles peer-reviewed research studies and scholarly articles that explore the epidemiology, diagnosis, treatment, and management of infectious diseases in horses.
Monath TP.The arthropod-borne encephalitides are an important cause of equine and human morbidity in the Americas. Between 1975 and 1978, 6970 human cases of arboviral encephalitis were reported in the United States of America; however, this represents only a fraction of the true incidence. St Louis encephalitis (4824 cases), California encephalitis (1035 cases), and western equine encephalitis (WEE, 947 cases) accounted for 98.5% of all reported infections. Approximately 1000-4000 cases of equine encephalitis occur annually in the United States, the majority due to WEE. In tropical America, important o...
Hazard GH, Hughes KL, Penson PJ.Contagious equine metritis (CEM) was first diagnosed in Australia in August 1977 and it has since been found on 6 farms in 3 states, having been isolated from about 24 mares and 2 stallions. Details are given of the epidemiology and control procedures used to combat CEM on one farm. Difficulty was experience in successfully treating one infected stallion; this was thought to be associated with inadequate cleaning and treating of the diverticulum of the urethral fossa. Introduction of the disease has had far-reaching consequences and may well result in the adoption of routine bacteriological te...
Powell DG, Whitwell K.Following an outbreak of CEM in England during 1977 a Code of Practice was introduced to control the disease in 1978. The Code recommended a bacteriological screening programme for Thoroughbred mares and stallions and improved standards of hygiene on the stud farm. As a result of the implementation of the Code a number of asymptomatic carrier mares was detected. Stallions which had transmitted CEM in 2977 and were treated did not transmit the disease during 1978. Two small outbreaks of CEM were reported during the 1978 breeding season.
Day FT, Crowhurst RC, Simpson DJ, Greenwood RE, Ellis DR, Eaton-Evans W.An outbreak of contagious equine metritis occurred in Newmarket in 1977. This survey records the effect on fertility of 20 of the stallions which were infected. Swabbing of mares since then has detected 37 carrier mares harbouring the organism, most frequently in the clitoral area. This swabbing programme reduced the incidence of new cases in 1978 to 3 mares and 1 stallion.
Klevjer-Anderson P, Cheevers WP, Crawford TB.Equine dermal fibroblasts persistently infected with equine infectious anemia virus (EIAV) show no alterations in cell morphology or growth kinetics when compared to uninfected cells. The percentage of cells immunofluorescent positive for viral proteins fluctuated, depending upon the stage of the cell cycle, while production of extracellular virus was uniform throughout the cell cycle, increasing only as the cell number increased. This was shown in log versus stationary phase cultures as well as in cultures synchronized by sterum starvation. The establishment of productive infection did not re...
Timoney PJ, O'Reilly PJ, McArdle JF, Ward J, Harrington AM, McCormack R.Reproduction of contagious equine metritis 1977 in Pony mares was achieved with cultures of an unclassified Gram-negative coccobacillus. Infected mares developed a vaginal discharge and associated inflammatory changes of the cervix and vagina. There was evidence of variation in pathogenicity between different strains of the organism. Although all infected mares made spontaneous clinical recoveries, the Gram-negative coccobacillus persisted in the genital tracts of a considerable proportion for a variable period after challenge. Recovery of the organism was not associated solely with the occurr...
Ricketts SW, Rossdale PD.Endometrial biopsy samples before and after treatment were obtained from 10 mares naturally infected and one Pony mare experimentally infected with Contagious Equine Metritis in 1977. The histopathological features were a short-lived polymorphonuclear cell infiltration of the luminal epithelium and stroma followed by a very early and marked mononuclear cell infiltration of the stroma, including many plasma cells. The luminal epithelium responded with cellular proliferation which may have reflected a regenerative response. Following the initial acute response, intercellular basal vacuoles conta...
Kendrick JW, Stevenson W.A band of 23 pregnant mares on a Thoroughbred breeding farm all had serum virus-neutralizing antibody titres to equine herpesvirus 1 (EHV-1). Antibody was not transferred to their foals in utero. All foals received antibody from colostrum and developed antibody titres similar to their dams. The serum virus-neutralizing antibody titres were observed in 10 of these foals for 1 year. Decay of passive immunity occurred at the rate of 3.25 two-fold dilutions in 100 days and reached zero at the mean time of 180 days. The foals were exposed to EHV-1 twice. Foals with a geometric mean titre of 1 : 25 ...
Bryans JT, Hendricks JB.Contagious equine metritis, introduced by importation of 2 comtaminated stallions from France, affected 54 Thoroughbred brood mares during the 1978 breeding season in Kentucky. The infection was diagnosed bacteriologically and by the use of a complement fixation test. Although lateral spread to stallions, and probably to a few mares, occurred through human agency in the breeding sheds of 2 stud farms, control measures instituted early in the epidemic confined the disease to brood mares bred by stallion on only these farms.
Tatarov G, Martinov S, Panova M.It was established that the complement binding reaction (CBR) is a suitable and very fast method for horse rhino-pneumonitis diagnostics. Cell cultural virus produced in cell cultures of pig kidneys was used as antigen. The antigen lots tested have no anticomplementary properties. Highest complement binding activity was evident in the non-diluted antigen, which discovered specific antibodies in immune serums. The CBR specificity was tested by the aid of homologous and heterologous serums and antigens. The titers of complement binding antibodies in the serums of 255 horses recovered from the di...
Timoney PJ, O'Reilly PJ, Harrington AM, McCormack R, McArdle JF.The ability of Haemophilus equigenitalis, the causal agent of contagious equine metritis 1977, to survive in various antibiotic-containing semen extenders was studied at different environmental temperatures. Gentamicin sulphate was found to be markedly superior to ampicillin or a combination of sodium benzyl penicillin and polymyxin B sulphate, Semen treated with the former antibiotic was either sterile at cultural examination or else yielded appreciably fewer colonies of H. equigenitalis than the untreated semen control. Ampicillin had no observable effect on the survival of this organism. Ge...
Nazer AH.The antibiotic resistance patterns and the distribution of R-factors among Escherichia coli isolated from apparently healthy dogs, cattle, sheep and horses were studied. It was found that 102 strains (16.48 per cent) of a total of 619 isolates were resistant to one or more drugs. Twenty-six per cent (27 strains) of the resistant strains were capable of transferring either a part or the entire resistance patterns to the sensitive recipient strain. These results indicates that antibiotic resistance and R-factors are not particularly widespread among animals whose diet does not cotain antimicrobi...
Artsob H, Wright R, Shipp L, Spence L, Th'ng C.A study was undertaken in 1975 to determine California encephalitis virus activity in southern Ontario. Three thousand and sixty-one mosquitoes, primarily Aedes species, were divided into 104 pools and inoculated into suckling mice. Isolates of snowshoe hare virus were obtained from one pool each of Aedes fitchii and A. triseriatus mosquitoes collected in the Guelph area. Serological testing of horse sera revealed extensive virus activity in southern Ontario and indicated that horses may serve as excellent monitors for California encephalitis virus.
Pampiglione S, Baldelli R, Corsini C, Mari S, Mantovani A.The occurrence of a trichinellosis epidemic in the province of Reggio Emilia in 1975, the source of which was attributed to horse meat, led the authors to use this animal for experimental infections. By using the trichina strain isolated from the above outbreak, 4 horses were infected orally. All 4 animals became infected. The most affected muscles were the lingual, masticatory and neck ones. Meat from the 4 horses was subsequently fed to laboratory animals (rats, mice, guineapigs) and other domestic species (cats, dogs, pigs) and further infections were obtained. An attempt to infect also a s...
Lloyd S, Soulsby EJ.This survey was performed to study the prevalence of infection with Onchocerca cervicalis in horses in the eastern United States. In the course of the survey, 121 horses, 1 mule and 1 donkey were examined. Microfilariae were recovered from 74 (61%) of the horses examined. All infected horses showed microfilariae of O cervicalis in the umbilical sample, 62 (84%) were infected in the eyelid and, in 36 (49%), microfilariae had invaded the eye. The mule was unifected and the donkey was infected with O cervicalis.
Srihongse S, Grayson MA, Morris CD, Deibel R, Duncan CS.An extensive outbreak of eastern equine encephalomyelitis (EEE) occurred in upstate New York during the summer of 1976, with 37 cases confirmed in horses by isolation of virus and/or by serologic examination. Other specimens collected in the affected area yielded 16 further isolates: 9 from 818 pools of 33,365 mosquitoes, 5 from tissues of 64 birds and 2 from 4 sentinel pheasants with serologic conversions. EEE antibodies were also detected in 81 of 499 wild birds tested. Our data implicate sparrows, cowbirds, and catbirds in the amplification of EEE virus and Culiseta melanura mosquitoes as v...
Smith AW, Vedros NA, Akers TG, Gilmartin WG.In a 5-year study (1972-1977) of microbial agents isolated from both clinically normal and diseased marine mammals, it was shown that certain disease agents are widespread in a diversity of ocean populations and that some are also transmissible to a number of terrestrial mammal species. Leptospira interrogans serovar pomona has been isolated repeatedly from 2 species of pinnipeds (Zalophus californianus califonianus and Callorhinus ursinus). Some of the more important bacterial pathogens for land mammals that were isolated from wild marine mammals are Pseudomonas mallei, Clostridium chauvoei, ...
McAllister RA, Sack WO.A median clitoral sinus, as a space canalized from epithelial cells, was distinguishable developmentally in equine fetuses from 33-mm crown-rump length (CRL) to 500-mm CRL (including a mule of 21-mm CRL). In saggital sections of the clitoris of a 480-mm CRL fetus, indentations under the transverse frenular fold were identified as lateral sinuses of the clitoris. Unlike the median sinus, they were shallow; it therefore could not be anatomically substantiated that the lateral sinuses were of sufficient depth to support the growth of the partial anaerobe Taylorella equigenitalis, the organism of ...
Warren A.A 5-year-old Hanoverian horse was presented for a palpable and visible mass over the frontal and maxillary sinuses. Following endoscopy and radiography surgical excision was attempted. The horse was euthanized during surgery and samples of the mass were identified as malignant anaplastic sarcoma, a seldom reported sinonasal tumor in equids. Sarcome anaplasique naso-sinusien équin infecté par Escherichia coli multirésistant aux antibiotiques. Un cheval Hanovrien âgé de 5 ans a été présenté pour une masse palpable et visible sur les sinus frontal et maxillaire. Après une endoscopie et ...
Abigail McGlennon of the Animal Health Trust and Andrea Vilela of the Redwings Horse Sanctuary describe the creation and impact of a new initiative to tackle strangles in UK horses.