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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.
Emergence of rifampin-resistant Rhodococcus equi in an infected foal. To investigate the emergence of rifampin resistance in Rhodococcus equi strains isolated from foals and their environment in Japan, we compared the in vitro antimicrobial susceptibilities to rifampin of 640 isolates from 64 infected foals and 98 soil isolates from their horse-breeding farms. As a control, 39 human isolates from patients with and without AIDS were also tested for susceptibility to rifampin. All of the isolates showed rifampin sensitivity, except isolates from one infected foal and two patients with AIDS that showed rifampin resistance. To investigate the emergence of rifampin-r...
Higher prevalence of Borna disease virus infection in blood donors living near thoroughbred horse farms. It is believed that Borna disease virus (BDV), an etiological agent of progressive polioencephalomyelitis in horses and sheep, is closely associated with psychiatric disorders in humans since the prevalence of BDV is higher in psychiatric patients than in blood donors. We investigated whether or not BDVs in humans are derived from infected domestic animals, by characterizing the BDVs in blood donors and horses derived from the same region of Hokkaido island, Japan. The seroprevalences (2.6 to 14.8%) of BDV were significantly higher in the blood donors from four regions where most horse farms a...
Studies on the rod-coccus life cycle of Rhodococcus equi. In the present study all 19 Rhodococcus equi cultures isolated from horses and 19 of 22 R. equi cultures isolated from human patients displayed a rod-coccus life cycle after cultivation under defined growth conditions. A bacillary growth could be observed after cultivation of the bacteria in fluid media for 4 h at 37 degrees C, a coccoid morphology after cultivation of the bacteria for 24 h either on sheep blood agar plates or in fluid media. The different morphological features did not significantly influence the typability of the bacteria or the expression of surface proteins including 15-17...
Profiles of fragments after pulsed-field gel electrophoresis of cleaved genomic DNA from strains of Taylorella equigenitalis isolated from horses in Norway. The genomic DNA of eight strains of Taylorella equigenitalis, isolated from seven Norwegian Trotters and a Norwegian pony with contagious equine metritis in Norway, was examined by pulsed-field gel electrophoresis after separate digestions with two restriction enzymes, namely, ApaI and NotI. The respective electrophoretic profiles of the fragments were essentially identical but differed from those of T. equigenitalis NCTC11184T and Kentucky 188. They also exhibited slight differences from profiles obtained from Japanese isolates. These results may possibly suggest a common genotype and a commo...
Disruption of sphingolipid metabolism and induction of equine leukoencephalomalacia by Fusarium proliferatum culture material containing fumonisin B(2) or B(3). Fumonisin B(1), B(2), and B(3) are inhibitors of ceramide synthase, a key enzyme in the pathway for de novo sphingolipid biosynthesis. Corn, naturally contaminated with either predominantly fumonisin B(1) or pure fumonisin B(1), has been shown to cause equine leukoencephalomalacia (ELEM). It has been hypothesized that fumonisin-induced disruption of sphingolipid metabolism is an early event in the development of ELEM. Recently, it was shown that Fusarium proliferatum corn culture diets containing predominantly fumonisin B(2), but not diets which were predominantly fumonisin B(3), at 75 ppm (0....
Sequence analysis of equine adenovirus 2 hexon and 23K proteinase genes indicates a phylogenetic origin distinct from equine adenovirus 1. We report the first nucleotide sequence data on equine adenovirus 2 (EAdV2) which corroborate on the molecular level that EAdV2 is distinct from equine adenovirus 1 (EAdV1). Based on sequence homology with Eadv1 the hexon gene of Eadv2 was identified. HindIII restriction fragments containing the hexon and eight other viral genes were cloned into the plasmid pUC19 and the nucleotide sequence of the hexon and the 23K proteinase genes completely determined. Amino acid (aa) comparison of sequence fragments with published adenovirus (AdV) proteins identified the genes for the E1B/19K, IVa2, DNA pol...
Immunogenicity and efficacy of baculovirus-expressed and DNA-based equine influenza virus hemagglutinin vaccines in mice. Two fundamentally different approaches to vaccination of BALB/c mice with the hemagglutinin (HA) of A/Equine/Kentucky/1/81 (H3N8) (Eq/KY) were evaluated, that is, administration of HA protein vs administration of HA-encoding DNA. Each vaccine was tested for its immunogenicity and ability to provide protection from homologous virus challenge. HA protein was synthesized in vitro by infection of Sf21 insect cells with a recombinant baculovirus. Intranasal administration of this vaccine induced virus-specific antibodies, as measured by enzyme-linked immunosorbent assay (ELISA), but did not induce ...
The ICP0 protein of equine herpesvirus 1 is an early protein that independently transactivates expression of all classes of viral promoters. To assess the role of the equine herpesvirus type 1 (EHV-1) ICP0 protein (EICP0) in gene regulation, a variety of molecular studies on the EICP0 gene and gene products of both the attenuated cell culture-adapted Kentucky A (KyA) strain and the Ab4p strain were conducted. These investigations revealed that (i) the ICP0 open reading frame (ORF) of the KyA virus strain is 1,257 bp in size and would encode a protein of 419 amino acids, and in comparison to the ICP0 gene (ORF63) of the Ab4p strain of 1,596 bp (E. A. Telford, M. S. Watson, K. McBride, and A. J. Davison, Virology 189:304-316, 1992), ...
Clinical evaluation of the serodiagnostic value of enzyme-linked immunosorbent assay for Rhodococcus equi infection in foals. An enzyme-linked immunosorbent assay (ELISA) for detection of serum IgG antibodies against Tween 20-extracted antigen of strain ATCC 6939 was applied in Hidaka, Japan to a total of 752 sick foals showing a variety of signs of infectious disease. An optical density (OD) value of more than 0.3 was tentatively fixed to be positive on the basis of readings made of healthy horse sera in previous studies. During a 2 year study, 138 of the 752 sick foals showed an OD value of 0.3 or higher and were designated as 'suspected of R. equi infection'. Age distribution during the initial medical examination...
Localized sequence heterogeneity in the long terminal repeats of in vivo isolates of equine infectious anemia virus. The role of in vivo long terminal repeat (LTR) sequence variation of the lentivirus equine infectious anemia virus (EIAV) has not been explored. In this study, we investigated the heterogeneity found in the LTR sequences from seven EIAV-seropositive horses: three horses with clinical disease and four horses without any detectable signs of disease. LTR sequences were targeted in this study because the LTR U3 enhancer region of tissue culture-derived isolates has been identified as one of the few hypervariable regions of the EIAV genome. Furthermore, LTR variation may regulate EIAV expression in...
Pathogenesis and virulence of Rhodococcus equi. Inhalation of the soil-borne organism, Rhodococcus equi, can lead to a chronic and severe pyogranulomatous pneumonia in young horses and immunocompromised people. In addition, ulcerative colitis is a common sequela to infection in foals, and dissemination from the lung to other body sites is not uncommon in either the horse or man. Although the facultative intracellular bacterium is susceptible to neutrophil-mediated killing, it is able to resist innate macrophage defenses and establish residence within the intracellular environment of that phagocyte. Definitive virulence factors of R. equi ha...
Epidemiology of Rhodococcus equi infections: a review. An overview of epidemiology of R. equi infection in foals is presented, emphasizing the importance of the virulence-associated antigens and plasmids as epidemiological markers. The monoclonal antibody-based colony blot test has been developed to identify rapidly and accurately virulent R. equi. Epidemiological studies conducted during the recent 5 years have revealed that: (1) avirulent R. equi are widespread in the feces of horses and their environment on every farm; (2) the feces of horses and the environment of the horse farms having endemic R. equi infections demonstrated heavy contaminati...
Comparison of tracheal aspiration with other tests for diagnosis of Rhodococcus equi pneumonia in foals. The diagnostic value of tracheal aspiration was evaluated through comparison with other diagnostic methods using an experimental model of Rhodococcus equi (R. equi) pneumonia in foals. Pneumonia was induced by spraying of the virulent R. equi strain ATCC 33701 into the trachea of foals. All foals developed fever from 11 to 16 days after bacterial inoculation. One foal was euthanized on day 26 due to its poor prognosis, and other foals euthanized on day 43. During the experiment, some tests for diagnosis of Rhodococcus equi pneumonia such as tracheal aspiration, radiography, serodiagnosis and f...
Pathogenicity and virulence of Rhodococcus equi in foals following intratracheal challenge. Twelve foals, between 27 and 83 days old, were infected with 2 strains of Rhodococcus equi by intratracheal administration. Ten of the 12 foals were inoculated with 10(4)-10(10) colony forming units (cfu) of ATCC 33701 strain. The other 2 foals were inoculated with 10(9) cfu of a plasmid-cured derivative of the ATCC 33701 strain (ATCC 33701P-). All of the 10 foals challenged with the ATCC 33701 strain showed clinical signs of pulmonary disease within 5-13 days, such as gross lesions associated with acute bronchopneumonia and microscopic lesions associated with granulomatous pneumonia. The two ...
[Borna disease virus. An etiological agent in neuropsychiatric diseases?]. Borna disease virus has long been recognized as a cause of sporadic cases and epidemics of meningoencephalomyelitis in horses and sheep in southern parts of Germany. however, sero-epidemiological surveillances indicate that Borna disease virus has a global distribution in horses, without the recognition of clinical manifestations associated with the infection, in other parts of the world. During the past five years evidence has been presented suggesting that humans also can become infected with this virus or a closely related virus. A significantly increased sero-prevalence is seen in patient ...
Protective effect against Rhodococcus equi infection in mice of IgG purified from horses vaccinated with virulence associated protein (VapA)-enriched antigens. IgG was purified from horses immunized with repeated doses of virulence associated (VapA) enriched antigens extracted with Triton X-114 from the surface of a virulent strain of R. equi. This IgG were administered to mice immunosuppressed by prior treatment with indomethacin. Mice administered the higher dose were completely protected against intraperitoneal infection with R. equi; mice given the lower dose were partially protected. By contrast, mice administered concentrated nonimmune equine IgG were not protected. This study demonstrates that VapA may be an important antigen involved in humor...
Clinical manifestations, diagnosis, treatment, and prevention of Rhodococcus equi infections in foals. Since the 1986 Rhodococcus equi workshop, there have been major breakthroughs in understanding the epidemiology of, the virulence of, and the immune response to, this intriguing pathogen. However, with the exception of the use of hyperimmune plasma for the prevention of the disease (Martens et al., 1989; Madigan et al., 1991) the clinical aspects of R. equi infections have essentially remained unchanged. This article reviews the various clinical manifestations and summarizes recent advances in diagnosis, treatment and prevention of R. equi infections in foals.
Acute colitis in adult horses. A review with emphasis on aetiology and pathogenesis. This review article describes the different aetiological agents known or suspected to cause colitis in the adult horse, namely Salmonella spp., Clostridium spp., Ehrlichia risticii, Cyathostomes, fungi, various antibiotics, drugs, and toxins, with emphasis on their mechanism of action. For each of the infectious agents, diagnostic procedures are indicated. The effects of endotoxin can be important in all forms of equine colitis.
Survival of mycoplasmas inoculated in horse sera. Although it is known that commercialized bovine serum is sometimes contaminated with mycoplasmas, it is not clear whether mycoplasmas can survive in horse serum. In this study, as a preliminary examination of the survival of mycoplasmas inoculated in horse sera, the survivability of 8 strains of 7 mycoplasmas was tested. The results obtained reveal that two strains of M. bovis and M. gallisepticum were found to survive in non-heated and inactivated sera for 94 to 330 days at 30 or 37 degrees C. Three strains of M. bovirhinis, M. gateae and A. laidlawii lived for 7 to 330 days depending upon th...
Controlled dose confirmation study of a 2% moxidectin equine gel against equine internal parasites in The Netherlands. The efficacy of a 2% moxidectin equine gel at a dosage rate of 0.4 mg kg-1 was evaluated in a controlled trial at Utrecht University. Twelve yearling castrated male Shetland ponies grazed a pasture of 2 ha from May 1994 until housing in November. Six ponies were treated with moxidectin, whereas the others served as non-treated controls. Necropsy was carried out 35 days after treatment. Greater than 99% efficacy of moxidectin was observed on faecal egg output. No effect of moxidectin was observed on mucosal inhibited early cyathostome L3 (EL3) or on the total numbers of mucosal developing stage...
Prevalence of the virulence-associated gene of Rhodococcus equi in isolates from infected foals. The prevalence of the plasmid-encoded virulence-associated gene (vapA) of Rhodococcus equi, as determined by PCR, was found to be 98% in isolates from 154 foals with pneumonia, confirming the strong association of vapA with virulence. The vapA genes from 60 representative isolates were compared by digestion with the restriction endonuclease HinfI, and no evidence of sequence variation was detected.
Prevalence of equine piroplasmosis in Central Mongolia. Antigen for the indirect fluorescent antibody test (IFAT) was routinely prepared from infected erythrocytes from horses experimentally infected with Babesia equi and Babesia caballi. With the successful establishment of in vitro cultures of B. equi and B. caballi, it is now possible to employ culture-derived antigens in this test. In this study, in vitro-propagated B. equi- and B. caballi-infected erythrocytes were used as antigen in the IFAT. Various modifications to an established protocol had to be implemented to allow repeatable results. Cultures with 3-4% parasitized erythrocytes were fou...
Antibodies against some viruses of domestic animals in southern African wild animals. Twenty-four species of South African wild animals were tested for the presence of antibodies against the viruses of 16 common diseases of domestic animals. Positive results were obtained for African horsesickness, equine encephalosis, equid herpes virus-1, infectious bovine rhinotracheitis, Allerton disease (Herpes mammillitis), lumpy skin disease, parainfluenza, encephalomyocarditis, bluetongue, Wesselsbron disease, bovine ephemeral fever, and Akabane disease complex. No antibodies could be demonstrated against the viruses of equine influenza, equine infectious anaemia, equine viral arteritis...
Characterization and mutational studies of equine infectious anemia virus dUTPase. The macrophage tropic lentivirus, equine infectious anemia virus (EIAV), encodes a dUTPase in the pol gene that is required for efficient replication in macrophages. Two naturally occurring variants of the enzyme were expressed as recombinant proteins in Escherichia coli; metal chelate affinity chromatography was used to purify histidine-tagged recombinant enzymes to greater than 80% homogeneity in a single chromatographic step. Biochemical and enzymatic analyses of these preparations suggest that this method yields dUTPase that is suitable for detailed mutational analysis. Specific activities...
Detection of latency-associated transcripts of equid herpesvirus 1 in equine leukocytes but not in trigeminal ganglia. Results from Southern hybridization and PCR amplification experiments using a randomly synthesized reverse transcription-PCR product showed that peripheral blood leukocytes from horses showing no clinical signs of disease expressed a putative latency-associated transcript antisense to and overlapping the 3' end of the equid herpesvirus 1 (EHV-1) immediate-early gene (gene 64). A PCR product derived from this transcript has > or =96% identity with the published EHV-1 sequence. In situ hybridization studies of equine bronchial lymph nodes corroborated these findings and are consistent with re...
