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Topic:Infectious Disease
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.
Equine viral arteritis. Equine viral arteritis (EVA) can cause prominent economic losses for the equine industry. The purpose of this review is to provide the pathologist some familiarity with the clinical history, lesions, pathogenesis, and diagnosis of EVA. EVA is caused by an arterivirus (equine arteritis virus, EAV), and the vascular system is the principal but not unique viral target. EVA has variable presentations, including interstitial pneumonia, panvasculitis with edema, thrombosis and hemorrhage, lymphoid necrosis, renal tubular necrosis, abortion, and inflammation of male accessory genital glands. EAV anti...
Parasite control methods used by horse owners: factors predisposing to the development of anthelmintic resistance in nematodes. One hundred and fifty horse owners, primarily private owners and riding schools, replied to a questionnaire concerning the practices they used to control parasites. Twenty-seven had experienced a parasite problem. Faecal samples from 188 horses selected at random showed that worm control practices were generally successful; however, many owners were not following recommendations for slowing the development of resistant parasites. In 1996, 86 per cent of the owners were using either three or two classes of anthelmintic a year, and they used a median of six doses with a range from one to 11. App...
Recent developments in the epidemiology of virus diseases and BSE. There is a continuous change in viral epidemics with respect to clinical symptoms, their duration or disappearance and the emergence of new diseases. This can be observed both in human and animal diseases. This evolution of virus diseases is mainly related to three factors: etiological agent, host and environment. As far as genetic alterations of the virus are concerned, two major mechanisms are involved: 1) mutations such as recombination and reassortment; 2) selection for resistance or susceptibility. The epidemiology of newly emerged virus diseases in man and animals, such as AIDS and hemor...
Detection of Leptospira spp. in the aqueous humor of horses with naturally acquired recurrent uveitis. Leptospiral organisms have long been presumed to be associated with the presence of equine recurrent uveitis. This project was undertaken to determine the presence of Leptospira spp. in the aqueous humor of horses with uveitis to determine if there was an association with inflammation. Thirty horses were determined to have recurrent uveitis based on clinical evaluation or history. Sixteen horses were judged clinically and historically to be free of uveitis and were used as controls. Aqueous humor samples were cultured and evaluated by PCR for the presence of Leptospira DNA. Serum was collected...
Risk factors for equine influenza serum antibody titres in young thoroughbred racehorses given an inactivated vaccine. Young Thoroughbred racehorses (222 yearlings entering training and 246 2-year-old horses already in training) from eight flat-training yards in Newmarket, UK were used to monitor serological responses to vaccination with an inactivated influenza virus vaccine. Blood samples taken prior to and after vaccination were tested by single radial haemolysis (SRH) to determine antibody titres (expressed as area of haemolysis in mm(2)). Prior to vaccination, yearlings had mean antibody titres (64+/-4 mm(2)) that were approximately half of those of 2-year-olds (115+/-3 mm(2)) and 89% of yearlings and 73%...
Induction of apoptosis by equine arteritis virus infection. Equine arteritis virus (EAV) is the etiological agent of equine viral arteritis, a contagious viral disease of equids. EAV is the prototype virus of the arteriviruses, a group of small enveloped viruses with positive single-stranded RNA genomes. Because apoptosis or programmed cell death is believed to play an important role in the biogenesis of several cytopathogenic viruses, we examined whether EAV was able to induce cell apoptosis in vitro. To do this, Vero cells were infected with EAV at a multiplicity of infection of 0.1 tissue culture infectious dose (TCID50) per cell, and analyzed at va...
Clinical, bacteriologic, serologic, and pathologic features of infections with atypical Taylorella equigenitalis in mares. To characterize clinical, serologic, bacteriologic, cytologic, and pathologic endometrial responses of mares to 2 donkey-origin atypical bacterial isolates resembling Taylorella equigenitalis. Methods: Prospective in vivo study. Methods: 10 healthy mares. Methods: Mares in estrus (2/group) were inoculated by intrauterine infusion with 2 isolates of classic T equigenitalis or 2 isolates of atypical Taylorella sp or were sham-inoculated. Bacteriologic, serologic, clinical, uterine, cytologic, and pathologic endometrial responses were assessed 4, 11, 21, 35, and 63 days after inoculation and on d...
Foaling-management practices associated with the occurrence of enterocolitis attributed to Clostridium perfringens infection in the equine neonate. Enterocolitis associated with Clostridium perfringens (C. perfringens) infection in neonatal foals is often severe and has been associated with a high case-mortality risk. We designed a premises-based survey to evaluate the associations of regional foaling practices, premises environmental management, periparturient foal and brood-mare management, and periparturient brood-mare ration with the occurrence of neonatal enterocolitis attributed to C. perfringens infection. Potential risk factors individually associated with enterocolitis were breed type, housing type at foaling and in the first thr...
Bluetongue and equine viral arteritis viruses as models of virus-induced fetal injury and abortion. A number of viruses have the capacity to cross the placenta and infect the fetus to cause, among other potential outcomes, developmental defects (teratogenesis), fetal death and abortion. Bluetongue virus (BTV) infection of fetal ruminants provides an excellent model for the study of virus-induced teratogenesis. This model has shown that only viruses modified by passage in cell culture, such as modified live virus vaccine strains, readily cross the ruminant placenta, and that the timing of fetal infection determines the outcome. Thus, cerebral malformations only occur after fetal infection at ...
Use of repetitive sequence-based polymerase chain reaction for molecular epidemiologic analysis of Streptococcus equi subspecies equi. To determine whether repetitive sequence-based polymerase chain reaction (rep-PCR) could be used to differentiate Streptococcus equi isolates, to examine S equi isolates from throughout the world, and to determine whether a horse had > 1 subtype of S equi during an outbreak of disease. Methods: An initial group of 32 S equi isolates, 63 S equi isolates from various geographic areas, and 17 S equi isolates obtained during outbreaks of disease. Methods: An aliquot of S equi genomic DNA was amplified, using enterobacterial repetitive intergenic consensus primers. Gel electrophoresis was perfor...
Streptococcus equi with truncated M-proteins isolated from outwardly healthy horses. The M-protein genes of Streptococcus equi isolated from 17 outwardly healthy horses after 4 strangles outbreaks had ended, including a quarantined animal, were compared with those of S. equi isolates from 167 active cases of strangles across 4 countries. The healthy horses included 16 persistent S. equi carriers, at least one from each of the four outbreaks. These carriers, despite being outwardly healthy, had empyema of the guttural pouch(es), an enlargement of the equine Eustachian tube. A persistent carrier from two of these outbreaks, the quarantined animal and a healthy animal with normal...
Cross-sectional study of faecal shedding of Giardia duodenalis and Cryptosporidium parvum among packstock in the Sierra Nevada Range. Faecal specimens from 305 horses and mules used as packstock at one of 17 commercial or governmental (National Park Service, US Forest Service) operations were examined for Giardia duodenalis and Cryptosporidium parvum using immunofluorescent microscopy. Fourteen packstock (4.6%) were shedding G. duodenalis cysts, with herd-level prevalences ranging 0-22%. Number of packstock in the corral, size of corral and density of packstock in the corral were associated with the odds of shedding G. duodenalis cysts. None of the horses had detectable C. parvum oocysts. Assuming a sensitivity of at least 4...
Detection and quantitation of Ehrlichia risticii genomic DNA in infected horses and snails by real-time PCR. A real-time quantitative PCR using the TaqMan fluorogenic detection system (TaqMan PCR) was established for identification of Ehrlichia risticii, the agent of Potomac horse fever (PHF). The TaqMan PCR identified an 85 base pair section of the 16S rRNA gene by use of a specific fluorogenic probe and two primers. This technique was specific for eight tested E. risticii strains. The TaqMan system identified 10 copies of a cloned section of the 16S rRNA gene of E. risticii. The sensitivity and specificity of the TaqMan PCR were similar to those of conventional nested PCR. The TaqMan PCR was evalua...
Ehrlichia equi infection of horses from Minnesota and Wisconsin: detection of seroconversion and acute disease investigation. Equine granulocytic ehrlichiosis (EGE) is caused by infection with Ehrlichia equi. EGE has been reported primarily in northern California, where E equi is transmitted by the tick Ixodes pacificus. Reports of EGE and the emergence of human granulocytic ehrlichia in Minnesota prompted a seroprevalence study of E equi in horses of Minnesota and Wisconsin. Tick (Ixodes scapularis) endemic areas of Minnesota and Wisconsin were compared to nonendemic regions of Minnesota. Indirect fluorescent antibody was used to detect the presence of serum antibodies to E equi. Serum samples from healthy horses, 3...
Toxigenic Corynebacterium diphtheriae associated with an equine wound infection. No abstract available
Equine influenza vaccine efficacy: the significance of antigenic variation. To investigate the level of cross-protection induced by equine influenza H3N8 vaccines derived from different lineages, two studies have been carried out with ponies vaccinated with 'American-like' and 'European-like' vaccines and experimentally challenged with a European-like strain. The results demonstrated that equine influenza vaccines clearly protect against challenge with homologous virus if serum antibody titres are sufficiently high. On the other hand, protection is incomplete even when animals vaccinated with heterologous strains have comparative antibody levels. Nevertheless, the pro...
DNA vaccination against influenza viruses: a review with emphasis on equine and swine influenza. The influenza virus vaccines that are commercially-available for humans, horses and pigs in the United States are inactivated, whole-virus or subunit vaccines. While these vaccines may decrease the incidence and severity of clinical disease, they do not consistently provide complete protection from virus infection. DNA vaccines are a novel alternative to conventional vaccination strategies, and offer many of the potential benefits of live virus vaccines without their risks. In particular, because immunogens are synthesized de novo within DNA transfected cells, antigen can be presented by MHC c...
Identification and phylogenetic comparison of Salem virus, a novel paramyxovirus of horses. A virus that could not be identified as a previously known equine virus was isolated from the mononuclear cells of a horse. Electron microscopy revealed enveloped virions with nucleocapsid structures characteristic of viruses in the Paramyxoviridae family. The virus failed to hemabsorb chicken or guinea pig red blood cells and lacked neuraminidase activity. Two viral genes were isolated from a cDNA expression library. Multiple sequence alignments of one gene indicated an average identity of 45% as compared to Morbillivirus N protein sequences. A weaker relationship was found with Tupaia paramy...
An equine herpesvirus 1 (EHV1) abortion storm at a riding school. An outbreak of EHV1 abortions occurred at a riding school in The Netherlands in 1991. Seven of twelve pregnant mares aborted, and another foal died at 8 days of age. Six abortions occurred within 12 days in March after an initial abortion on 8 February. Four mares delivered live foals. Virological examination of four aborted foals revealed an EHV1 infection. Serological results for paired sera from 17 horses suggested, that the initial abortion on 8 February was the index case, and probably caused the other six abortions. The index case could well have been caused by reactivation of latent vir...
Development of a fluorescence polarization-based diagnostic assay for equine infectious anemia virus. The control of equine infectious anemia virus (EIAV) infections of horses has been over the past 20 years based primarily on the identification and elimination of seropositive horses, predominantly by a standardized agar gel immunodiffusion (AGID) assay in centralized reference laboratories. This screening for EIAV-seropositive horses has been to date hindered by the lack of a rapid diagnostic format that can be easily employed in the field. We describe here the development of a rapid solution-phase assay for the presence of serum antibodies to EIAV based on fluorescence polarization (FP) (pat...
Differentiation and genomic and antigenic variation among fetal, respiratory, and neurological isolates from EHV1 and EHV4 infections in The Netherlands. Ten monoclonal antibodies (MAbs) were produced against equine herpes virus type 1 (EHV1). Two appeared type-specific, while the other eight were directed against epitopes common to both EHV1 and EHV4. Two MAbs directed against the glycoprotein gp2 recognized linear epitopes, as demonstrated by Western blotting. With pools of type-specific MAbs, 282 field isolates were typed in an immunoperoxidase monolayer assay (IPMA). From a total of 254 fetal or neonatal isolates, 244 (96%) were typed as EHV1, whereas 14 out of 15 (93%) respiratory tract isolates were typed as EHV4. Surprisingly, 3 out of 1...
Binding of equine infectious anemia virus rev to an exon splicing enhancer mediates alternative splicing and nuclear export of viral mRNAs. In addition to facilitating the nuclear export of incompletely spliced viral mRNAs, equine infectious anemia virus (EIAV) Rev regulates alternative splicing of the third exon of the tat/rev mRNA. In the presence of Rev, this exon of the bicistronic RNA is skipped in a fraction of the spliced mRNAs. In this report, the cis-acting requirements for exon 3 usage were correlated with sequences necessary for Rev binding and transport of incompletely spliced RNA. The presence of a purine-rich exon splicing enhancer (ESE) was required for exon 3 recognition, and the addition of Rev inhibited exon 3 sp...
Genetic manipulation of equine arteritis virus using full-length cDNA clones: separation of overlapping genes and expression of a foreign epitope. Equine arteritis virus (EAV) is an enveloped, positive-stranded RNA virus belonging to the family Arteriviridae of the order Nidovirales. The unsegmented, infectious genome of EAV is 12,704 nt in length [exclusive of the poly(A) tail] and contains eight overlapping genes that are expressed from a 3'-coterminal nested set of seven leader-containing mRNAs. To investigate the importance of the overlapping gene arrangement in the viral life-cycle and to facilitate the genetic manipulation of the viral genome, a series of mutant full-length cDNA clones was constructed in which either EAV open readi...
