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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.
Pathogenesis of equine herpesvirus-1 in specific pathogen-free foals: primary and secondary infections and reactivation. Six specific pathogen-free foals shown to be free of equine herpesvirus-1 and 4 (EHV-1 and -4) and lacking in maternally-derived antibodies were used to investigate the pathogenesis of EHV-1 in horses. Following primary intranasal inoculation with EHV-1 all foals showed signs of a mild, self-limiting upper respiratory tract infection. A leucopenia was observed, comprising both a lymphopenia and neutropenia. Virus was isolated from nasal mucus and buffy coat cells over several days during the clinical episode and after the animals became clinically normal. Notwithstanding the mildness of the cl...
Pathological findings in horses dying during an outbreak of the paralytic form of Equid herpesvirus type 1 (EHV-1) infection. In 1988 an outbreak of the paralytic form of Equid herpesvirus type 1 (EHV-1) infection occurred on a stud farm and several animals died. This provided an opportunity to perform detailed pathological investigations to gain insights into the pathogenesis of this spontaneous disease. Two paretic mares, three foals, an aborted foetus and its non-paretic dam were examined. The endotheliotropism of the virus was clearly demonstrated by the use of an indirect immunoperoxidase (IP) stain. At autopsy, evidence of viral infection was widespread in the foetus and foals, but limited or absent in the mare...
Evolutionary pattern of the H 3 haemagglutinin of equine influenza viruses: multiple evolutionary lineages and frozen replication. The nucleotide and deduced amino acid sequences of the haemagglutinin genes coding for the HA 1 domain of H3N8 equine influenza viruses isolated over wide regions of the world were analyzed in detail to determine their evolutionary relationships. We have constructed a phylogenetic model tree by the neighbour-joining method using nucleotide sequences of 15 haemagglutinin genes, including those of five viruses determined in the present study. This gene tree revealed the existence of two major evolutionary pathways during a twenty five-year period between 1963 to 1988, and each pathway appeared t...
Prevalence of complement-fixing antibody to the African horse sickness virus in domestic animals in Nigeria. The occurrence of antibodies against the African horse sickness virus was investigated in 246 domestic animals (horses, donkeys, camels, dogs) in various regions of Nigeria by means of the complement-fixing rate. 34% of the sera tested were positive: 75% in donkeys, 68% in horses, 19% in camels, and 9% in dogs. Among the horses, those of 6 to 15 years of age had higher than average prevalence rates than the other age groups. Stallions from the northern regions had higher prevalence rates than mares generally and stallions from other regions. These findings are important for the epidemiology of...
[Teratogenic effect of the Venezuelan equine encephalitis virus: a review of the problem]. Clinical findings on Venezuelan Equine Encephalitis virus infection and the teratogenic effects of several Togaviruses are described. Similarities between the intrauterine alterations induced by Venezuelan Equine Encephalitis virus and rubella virus are pointed out. Findings described by Wenger in 1967 were those of massive cerebral necrosis in fetuses of women presumably suffering of encephalitis and they are commented along with the development of an animal experimental model at the end of 1970-1980. Pathogenesis of the intrauterine infection seemed to be related to changes in the placental ...
The electron microscopic and immunohistochemical demonstration of a papillomavirus in equine aural plaques. This research study investigates the cause of aural plaques in horses and provides strong evidence that papillomaviruses are to blame. The study used various tools including electron microscopic examination, immunohistochemical […]
Epidemiology of equine rotavirus infection among foals in the breeding region. Rotavirus is one of causative agents for acute diarrhea in infants of several animal species including humans [1]. Detection or isolation of rotavirus from the feces of foals with diarrhea has been reported in England [2], the U.S.A. [3, 5, 6], Australia [14] and Japan [10, 12]. It has been shown through serological surveys in Japan [4, 8, 9] and the U.S.A. [3, 13] that rotavirus is widespread among horses and foals. However, there have been few detailed reports on the occurrence of foal diarrhea caused by rotavirus. This report focuses on the occurrence of foal diarrhea and the isolation of r...
Septic tenosynovitis in horses: 25 cases (1983-1989). The medical records of 25 horses with septic tenosynovitis treated over 7 years (1983 to 1989) were reviewed to determine clinical features of the disease and response to treatment. The median age of horses with septic tenosynovitis was 5 years (range, 1 month to 21 years). Fourteen fore limbs and 11 hind limbs were affected. Sepsis was located in the sheath of the digital flexor tendons of 22 horses. Sepsis was located in the sheath of the extensor carpi radialis tendon (1 horse), sheath of the long digital extensor tendon (1 horse), or sheath of the common digital extensor tendon (1 horse) i...
A minimal lentivirus Tat. Transcriptional regulatory mechanisms found in lentiviruses employ RNA enhancer elements called trans-activation responsive (TAR) elements. These nascent RNA stem-loops are cis-acting targets of virally encoded Tat effectors. Interactions between Tat and TAR increase the processivity of transcription complexes and lead to efficient copying of viral genomes. To study essential elements of this trans activation, peptide motifs from Tats of two distantly related lentiviruses, equine infectious anemia virus (EIAV) and human immunodeficiency virus type 1 (HIV-1), were fused to the coat protein of b...
Immune-mediated thrombocytopenia in horses infected with equine infectious anemia virus. An adult horse infected with a virulent, cell culture-adapted strain of equine infectious anemia virus (EIAV) developed cyclical thrombocytopenia in which the nadir of platelet counts coincided with peak febrile responses. In order to investigate the mechanism of thrombocytopenia during acute febrile episodes, four adult horses were experimentally infected with the wild-type Wyoming strain of EIAV. Platelet counts decreased from baseline as rectal temperature increased. Serum reverse transcriptase activity increased above background levels in all horses, coincident with increase in rectal temp...
Equine monocytic ehrlichiosis (Potomac horse fever): a review. In the late 1970s, a new infectious disease in horses, involving acute enteritis, was recognised in the Potomac River area of Maryland, U.S.A. The causative agent was identified subsequently as a new species of rickettsial organism, later named Ehrlichia risticii. Since then, the disease has been reported in many other states, and in enzootic areas vaccination is common. Signs associated with the clinical disease included depression, fever, anorexia, decreased or absent intestinal sounds, profuse watery diarrhoea and laminitis. However, considerable variation in clinical manifestations has bee...
Actinobacillus spp. and related bacteria in infected wounds of humans bitten by horses and sheep. We describe the isolation of Actinobacillus lignieresii and an A. equuli-like bacterium from an infected horse-bite wound in a 22-year-old stable foreman and A. suis from a bite injury in a 35-year-old man who had been attacked by a horse. A. lignieresii was also isolated in pure culture from an infected sheep-bite wound in a rural worker. These species of the genus Actinobacillus are primarily associated with animals and animal diseases and are rarely isolated from humans. The purpose of this report is to raise awareness of the possible occurrence of Actinobacillus spp. in bite wounds inflict...
Measurements of the accuracy of clinical diagnoses of equine neurologic disease. Parameters for the accuracy of clinical diagnosis of neurologic diseases in the horse were determined from 210 horses in which a definitive pathologic diagnosis was confirmed. The overall efficiency of diagnosis for all diseases was 0.95 although the validity varied from 0.79 to 1.00, the sensitivity varied from 0.73 to 0.95, and the specificity varied from 0.88 to 1.00 for individual disease categories. Equine protozoal myeloencephalitis was overdiagnosed, whereas Eastern equine encephalomyelitis, equine degenerative myeloencephalopathy, and traumatic neurologic disease were underdiagnosed. T...
Common horse sense. This research article corrects a common misconception about the energy metabolism in horses during short sprinting and long-distance running events, emphasizing that short sprints are primarily powered by anaerobic activity, […]
Intranasal infection of Getah virus in experimental horses. Aerosol transmission in equine Getah virus (GV) infection was examined by intranasal inoculation with 10(3.0) to 10(7.0) TCID50 of the MI-110 strain in 7 experimental horses. The establishment of intranasal infection of GV was confirmed in all these horses by detecting serum neutralizing antibody against the MI-110 strain. Horses inoculated with more than 10(4.0) TCID50 of the virus manifested mild pyrexia, eruptions, serous nasal discharge, lymphopenia or monocytosis. Viremia ranging from 10(1.0) to 10(3.5) TCID50/0.2 ml occurred in horses inoculated with 10(5.0) TCID50, or more. Virus recove...
Persistent cryptosporidiosis in horses with severe combined immunodeficiency. Cryptosporidial infections were established in five young foals with severe combined immunodeficiency following oral administration of 10(8) Cryptosporidium parvum oocysts. All foals shed oocysts (average of 8 x 10(6) to 2 x 10(8)/g of feces) until death. Inflammation and C. parvum organisms were observed in the common bile duct, duodenum, jejunum, and ileum. Since foals with severe combined immunodeficiency lack functional T and B lymphocytes and are incapable of antigen-specific immune responses, they are well suited for evaluating the pathogenesis and treatment of persistent cryptosporidios...
Hepatic disease in Alberta horses: A retrospective study of ‘alsike clover poisoning’ (1973-1988). Over sixteen years, 49 horses were diagnosed by Alberta Agriculture Animal Health laboratories as having "alsike clover poisoning". There was a distinct northwestern distribution of cases, the majority coming from the Peace River district. This distribution is opposite to that of the Alberta horse population, but coincides with areas of alsike clover cultivation. Cases could be divided into chronic or nervous clinical presentations, as described by Schofield. Tissues from 45 animals were retrieved and examined microscopically. Significant histological lesions were confined to the liver and con...
Diagnostic application of polymerase chain reaction for detection of Ehrlichia risticii in equine monocytic ehrlichiosis (Potomac horse fever). Genomic amplification by the polymerase chain reaction (PCR) was used to identify a unique genomic sequence of Ehrlichia risticii directly in DNA isolated from peripheral-blood buffy coat cells of E. risticii-infected horses (Potomac horse fever) and from infected cell cultures. A specific primer pair, selected from a cloned, species-specific, 1-kb DNA fragment of the E. risticii genome as a template, was used for the amplification of the target DNA of 247 bp. The optimal number of 40 PCR cycles, determined by analyzing an amplification profile obtained with a constant Taq polymerase concentra...
Identification and comparative sequence analysis of a gene in equine herpesvirus 1 with homology to the herpes simplex virus glycoprotein D gene. A homologue of the herpes simplex virus (HSV) glycoprotein D gene has been identified in the genome of equine herpesvirus-1 (EHV-1, equine abortion virus). An open reading frame in the middle of the short unique (US) region is capable of encoding a polypeptide of 402 amino acids that has 26% and 20% of its residues matching pseudorabies virus (PRV) gp50 and HSV-1 gD, respectively. Despite this low level of similarity, the positional identity of six cysteine residues and certain motifs, and the location of the EHV-1 gene, clearly define the EHV-1 polypeptide as one of a family of "gD-like" prot...
Comparative growth of different rotavirus strains in differentiated cells (MA104, HepG2, and CaCo-2). The production of viral antigen after infection of MA104, HepG2 (derived from human liver), and CaCo-2 (derived from human colon) cells with various cultivatable human and animal rotavirus strains was compared using immunofluorescence tests. All rotavirus strains examined expressed antigen in CaCo-2 cells and MA104 cells, but only some virus strains, namely, SA11-Cl3 (simian), RRV (simian), CU-1 (canine), and Ty1 (turkey), produced antigen in numbers of infected HepG2 cells comparable to infections in MA104 and CaCo-2 cells. Fl-14 (equine), OSU (porcine), NCDV (bovine), and Ch2 (chicken) strai...
The Tat protein of equine infectious anemia virus is encoded by at least three types of transcripts. Nucleotide sequence analysis of a cDNA library of EIAV-infected canine cells established a complex pattern of gene expression, characterized by alternatively spliced polycistronic transcripts. The EIAV tat gene product was shown to be encoded by at least three species of mRNA which differed in their ability to trans-activate the EIAV LTR upon expression in canine cells. The most active cDNA was monocistronic, consisting of three exons. The most abundant cDNA in the library contained four exons and was identical to a polycistronic transcript previously described (Noiman et al., 1990b) which con...
Effect of viral inoculum size on appearance of clinical signs in equine Getah virus infection. A study was performed to examine the effect of viral inoculum size on the appearance of clinical signs in equine Getah virus (GV) infection by intramuscular inoculation with 10(1.3) to 10(6.3) TCID50 of the MI-110 strain in 6 experimental horses. When inoculated with more than 10(3.3) TCID50 of the virus, every horse developed pyrexia, edema in the hind legs, serous nasal discharge, lymphopenia and viremia in the relatively early stage of disease. On the other hand, enlargement of the submandibular lymph node was observed only in horses inoculated with 10(5.3) and 10(6.3) TCID50 of the virus, ...
Persistent thrombocytopenia in a case of equine infectious anemia. Persistent thrombocytopenia was detected in a horse with equine infectious anemia (EIA). The thrombocytopenia was considered to be immune-mediated, developing secondary to infection with EIA virus. Epistaxis, petechial hemorrhages, subcutaneous hematomas, and edema resolved after treatment with corticosteroids; however, the owners requested that the mare by euthanatized because of infection with EIA virus. Although clinical signs attributable to immune-mediated thrombocytopenia may resolve with appropriate treatment, horses with immune-mediated thrombocytopenia secondary to EIA have a guarded ...
Encephalitozoon infection in a still-born foal. A stud Clydesdale foal was still-born near full term. Macroscopic examination revealed a normal placenta, pulmonary atelectasis and faint white mottling of the kidneys. Microscopically there was severe lymphoplasmacytic interstitial nephritis. Numerous organisms resembling Encephalitozoon cuniculi were present in the affected kidneys. The organisms occurred in the areas of inflammation as well as in the renal glomeruli and intracellular cysts in the renal tubular epithelial cells and exhibited Gram positive staining. Ultrastructurally the organisms possessed a polar vacuole and a spiral filame...
Pulmonary aspergillosis associated with acute enteritis in a horse. Invasive pulmonary aspergillosis was detected at postmortem examination of an 8-year-old Quarter Horse mare that had a history of diarrhea, laminitis, and bilateral nasal discharge. A diagnosis of Ehrlichia risticii infection was made on the basis of clinical signs of diarrhea and pyrexia, high serum antibody titer to E risticii (1:2,560), and multiple Salmonella-negative cultures obtained from fecal and colonic specimens. Possible pathogenic mechanisms contributing to the development of pulmonary aspergillosis secondary to enteric disease include mycotic invasion of the intestinal tract or im...
A novel group A rotavirus G serotype: serological and genomic characterization of equine isolate FI23. Equine rotavirus FI23 was shown to be prototypic of a novel G serotype, provisionally G14, by cross-neutralization and VP7 sequence determination. Although distinct, there are as few as six differing amino acid residues (92, 94, 96, 146, 147, and 221) in the VP7 antigenic regions of FI23 and G3 rotaviruses.
Transient suppression of equine immune responses by equine infectious anemia virus (EIAV). Suppression of the immune system is a common aspect of the disease pathogenesis associated with retroviral infections in both man and animals. We have measured transient suppression of the equine immune system as a loss or decrease in antigen-specific and polyclonal lymphocyte proliferation following experimental infection of ponies with three variants of equine infectious anemia virus (EIAV) with difference virulence characteristics. The transient suppression of proliferative responses was temporally associated with recurrent febrile episodes, which are the hallmark symptom of EIAV-induced di...
Streptokinases produced by pathogenic group C streptococci demonstrate species-specific plasminogen activation. The species specificities of plasminogen activation and binding of plasmin by pathogenic group C streptococci isolated from humans, horses, and pigs were examined. Of 56 streptococcal isolates, 52 elaborated plasminogen activator activity and 49 of these had specificity for plasminogen of the homologous host. Analysis of supernatants from 13 isolates indicated that the plasminogen activator activity resulted from secreted streptokinases. These 13 streptokinases were antigenically related and bound all three plasminogens, indicating that the binding recognition sites were conserved despite the ...
