Topic:Pathogenicity
Pathogenicity in horses refers to the ability of infectious agents, such as bacteria, viruses, fungi, and parasites, to cause disease in equine hosts. This concept encompasses the mechanisms by which these pathogens invade, survive, and multiply within the horse, as well as the resulting clinical manifestations. Understanding pathogenicity involves studying the interaction between the pathogen and the horse's immune system, including the evasion strategies employed by the pathogen and the host's defensive responses. This page compiles peer-reviewed research studies and scholarly articles that investigate the factors influencing pathogenicity, the host-pathogen interactions, and the implications for disease management and prevention in equine populations.
Characteristics of Escherichia coli isolated from septic foals. Fifteen Escherichia coli isolates from the blood and tissue of foals with septicemia were compared with 15 from the feces of clinically normal horses. Comparisons were made with respect to survival in normal equine serum, production of aerobactin, and production of hemolysin. Isolates from the blood and tissues of septic foals were more likely to be resistant to equine serum than were isolates from feces of clinically normal horses. There were minimal differences between the isolates with respect to aerobactin and hemolysin production, almost all being nonhemolytic and aerobactin negative. Ser...
[The occurrence and significance of enterotoxin-producing Clostridium perfringens strains in the intestinal tract of horses]. 100 faecal samples from clinically healthy horses of different age groups and feeding habits, 50 samples of faeces from horses suffering from enteropathy accompanied by diarrhoea and small and/or large intestine from 25 horses that had died after an intestinal disease were examined for the presence of Clostridium (Cl.) perfringens. The frequency with which Cl. perfringens was detected was 22% in clinically healthy horses, 32% in horses with diarrhoea and 52% in the dead horses. In two faecal samples from the horses with diarrhoea the microbial count of Cl. perfringens was ca. 10(6) cfu/g faece...
[Hemolytic properties of bacteria belonging to the Acinetobacter genus]. Direct and intermediate hemolytic activity of 526 strains of Acinetobacter was investigated. Their ability to produce lipase and lecithinase was also studied. Measurements were performed parallely on human, horse, sheep and bovine erythrocytes. Direct hemolytic activity was exhibited by 16% of tested strains (17 out of 24 strains of A. haemolyticus). Human, sheep and bovine erythrocytes were useful for testing the hemolytic activity of Acinetobacter. The hemolysis was occurring faster and was visible more frequently during incubation at 37 degrees C. Indirect hemolytic activity was observed in...
Biology and neurobiology of Borna disease viruses (BDV), defined by antibodies, neutralizability and their pathogenic potential. Borna disease viruses (BDV) isolated from more than 20 naturally infected horses, 2 sheep and a possible feline isolate were included in these studies. Most of these wild-type viruses were grown in rabbit cells. Specifically rabbit-adapted viruses establish persistent infection in immortalized cell lines of various animal species. Brain-, tissue culture-, and cell-free released viruses could all be neutralized with antibodies from naturally and experimentally infected animals (horse; hamster, rat, rabbit, mouse, and chicken), with highest titres in birds. Splenectomized rabbits, which were sub...
Pathogenic studies and antigenic and sequence comparisons of A/equine/Alaska/1/91 (H3N8) influenza virus. An influenza virus, A/equine/Alaska/1/91 (H3N8), was isolated from horses from Alaska with an acute respiratory infection. Pathogenic and serologic studies revealed that this virus is similar to previously isolated equine H3N8 influenza viruses. Antigenic analyses utilizing hemagglutination inhibition and neuraminidase inhibition assays indicated an antigenic drift from the prototype equine H3N8 influenza virus, A/equine/Miami/1/63. Partial sequence analysis of the A/equine/Alaska influenza virus indicated that each of 8 gene sequences are of equine origin.
The pathogenicity of Ab4p, the sequenced strain of equine herpesvirus-1, in specific pathogen-free foals. The sequencing of the genome of equine herpesvirus-1 (EHV-1) is reported in Elizabeth A. R. Telford, Moira S. Watson, Kathryn McBride, and Andrew J. Davison, 1992, Virology, 189, 304-316. The sequence was derived using a plaque-purified clone of EHV-1 strain Ab4 (designated Ab4p). To ensure that Ab4p shares the pathogenic characteristics of parental Ab4 (hereafter Ab4), both were inoculated intranasally into foals, specifically free from EHV-1 and EHV-4. Clinical signs, including rectal temperature, were similar for both viruses. In addition, nasal shedding of virus was observed over a 1- to 2...
[Epidemiology of encephalitis caused by arbovirus in the Brazilian Amazonia]. An overview of ecological, epidemiological and clinical findings of potential arthropod-borne encephalitis viruses circulating in the Amazon Region of Brazil are discussed. These viruses are the Eastern Equine Encephalitis (EEE), Western Equine Encephalitis (WEE), St. Louis Encephalitis (SLE), Mucambo (MUC) and Pixuna (PIX). These last two are subtypes (III and IV) of Venezuelan Equine Encephalitis virus. The areas of study were the highways and projects of development, as well as places where outbreaks of human diseases caused by arboviruses had been detected. These viruses are widespread in ...
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 ...
Evidence for non-siderophore-mediated acquisition of transferrin-bound iron by Pasteurella multocida. Two clinical isolates of Pasteurella multocida associated with bovine pneumonia were examined for iron acquisition. Both isolates were capable of obtaining iron for growth from bovine but not from human, avian, equine or porcine transferrin. This correlated with specific binding of bovine transferrin by iron-limited cells or isolated membranes. No siderophore was detected in the strains by a general screening assay. In response to iron-limited conditions, a number of high molecular mass iron-regulated outer membrane proteins were produced including an 82 kDa receptor protein which was affinity...
Isolation of equine herpesvirus-1 mutants in the presence of (S)-9-(3-hydroxy-2-phosphonylmethoxypropyl)adenine: demonstration of resistance in vitro and in vivo. The compound (S)-9-(3-hydroxy-2-phosphonylmethoxypropyl)adenine (HPMPA) had been previously shown to be highly effective in treatment of EHV-1 in a murine model for the equine disease. This paper describes the isolation of a series of mutants resistant to the drug. Resistance was demonstrated in cell culture and one mutant was tested in a murine model. The resistant mutant was pathogenic for mice; infectious virus was recovered from respiratory tissues and blood at levels similar to the parental virus. However, the mutant showed a significant degree of resistance in vivo, thus proving the viru...
The microflora of the lower respiratory tract of the horse: an autopsy study. A series of 31 thoroughbreds and 18 non-thoroughbreds was examined post mortem to assess what bacteria might be present in the lower respiratory tract, and to assess their significance by correlating the bacteriological findings with histological changes in the lung. The distal trachea and seven representative lung sites were swabbed in each case. Sixty-six per cent of the sites were sterile with remaining sites producing scanty growths of mainly coagulase negative Staphylococcus spp., E. coli, Bacillus spp. and Pseudomonas spp. Anaerobes, mainly Clostridium perfringens, Bacteroides fragilis a...
Identification of 15- to 17-kilodalton antigens associated with virulent Rhodococcus equi. Antigens of Rhodococcus equi were analyzed by immunoblotting with naturally infected foal sera. Immunoblots of whole-cell antigen preparations of clinical isolates of R. equi revealed that major protein bands with molecular masses of 15 to 17 kDa were present in all clinical isolates tested and all isolates virulent for mice. In contrast, the 15- to 17-kDa antigens were not identified by immunoblotting in ATCC 6939, a type strain of R. equi that was avirulent for mice. Whole-cell antigens of 102 environmental isolates were investigated by immunoblotting and the mouse pathogenicity test. Twenty...
Equine infectious anemia virus derived from a molecular clone persistently infects horses. A full-length molecular clone of equine infectious anemia virus (EIAV) was isolated from a persistently infected canine fetal thymus cell line (Cf2Th). Upon transfection of equine dermis cells, the clone, designated CL22, yielded infectious EIAV particles (CL22-V) that replicated in vitro in both Cf2Th cells and an equine dermis cell strain. Horses infected with CL22-V developed an antibody response to viral proteins and possessed viral DNA in peripheral blood mononuclear cells, as determined by polymerase chain reaction assays. In addition, horses infected with CL22-V became persistently infe...
Nutritionally variant streptococci associated with corneal ulcers in horses: 35 cases (1982-1988). Nutritionally variant streptococci (NVS) are nutritionally deficient viridans streptococci that require pyridoxal for growth. Although NVS are pathogenic in human beings, they have not been considered to be pathogenic in domestic animals. In 1982 and 1983, 24 isolates of NVS were recovered from horses with ulcerative keratitis. A retrospective study was done to determine the incidence of NVS in horses with corneal disease. The medical records of 249 horses (259 eyes) examined for clinical signs of corneal disease were reviewed. Nutritionally variant streptococci were isolated from approximatel...
[Concomitant activity of 2 bunyaviruses in horses in Argentina]. A serologic survey of horses for Kairi (KRI) and Cache Valley (CV), two related Bunyaviruses, was conducted simultaneously in Cordoba and Santa Fe provinces, Argentina, during late 1983 and 1984. The prevalence of neutralizing antibodies only for KRI was 13.3% and only for CV was 40.0%; but if the total positive sera for KRI and CV were taken into account, the prevalence reached 48.3 and 75.0%, respectively. The prevalence for CV was higher than for KRI in Cordoba (p less than 0.01), but both were similar in Santa Fe province. The demonstration of seroconversion in horses of the two zones for ...
The transovarial transmission of Babesia caballi by Hyalomma truncatum. Babesia caballi, isolated from a horse that originated from South West Africa/Namibia, was transmitted transovarially by adult Hyalomma truncatum. B. caballi proved to be highly infective for adult H. truncatum. Forty-five per cent of ticks feeding on a reacting animal with an extremely low parasitaemia became infected. In spite of a low parasitaemia, the ticks were severely affected by the parasite. Seventy per cent of the infected ticks either died during oviposition or after laying only a few eggs. The features of the infection in horses were: a prepatent period of 10 days, very low parasit...
Isolation of Clostridium perfringens from foals. Clostridium perfingens was isolated from four of 29 healthy foals and from all twelve foals with gastrointestinal diseases. The range of viable counts of C. perfringens in the faeces was 10(1)-10(5)/g and in the intestinal specimens 10(1)-10(7)/g. Of 41 isolates of C. perfringens, 37 were considered to be type A. Enterotoxin of the organism was demonstrated in the intestinal contents of five of eight foals with enteric diseases. These findings suggested that C. perfringens is a likely pathogen of foal intestinal diseases.
Further investigations into the potentiation of infection by intra-articular injection of polysulfated glycosaminoglycan and the effect of filtration and intra-articular injection of amikacin. Polysulfated glycosaminoglycan (PSGAG) recently have been reported to potentiate the infectivity of Staphylococcus aureus in horses with experimentally induced septic arthritis. Four groups of 8 horses each had 1 midcarpal joint injected with approximately 33 viable colony-forming units (CFU) of S aureus plus either 1 ml of saline solution (group 1), 250 mg of PSGAG (group 2), 250 mg of PSGAG passed through a 0.6-microns filter (group 3), or 250 mg of PSGAG plus 125 mg of amikacin (group 4). Horses that developed clinical signs consistent with sepsis were euthanatized, and samples were collect...
Isolation of enterotoxigenic Escherichia coli from a foal with diarrhea. Enterotoxigenic Escherichia coli was isolated from a 3-day-old foal with diarrhea. The isolate was distinguished from nonpathogenic E coli by determining the presence of pili and enterotoxin production. A standard slide agglutination test was performed, using pooled antisera that contained antibodies against K99 and F41 pilus antigens, K87 capsular antigen, and 0101 somatic antigen. Agglutination of the antisera occurred in the presence of the isolate. Piliation was verified by use of negative-contrast electron microscopy. Further, the isolate produced a heat-labile enterotoxin-like antigen th...
Pathogenicity for horses of original Sagiyama virus, a member of the Getah virus group. Sagiyama virus is a member of the Getah virus group. Its pathogenicity for horses was examined. All the horses infected with the original 4 strains of Sagiyama virus (M6/Mag 33, Mag 121, Mag 132 and Mag 258) developed pyrexia ranging from 39.0 to 40.0 degrees C. Other clinical signs, characterized by eruptions, edema in the hind legs, enlargement of the submandibular lymph node and mild leukopenia, were also manifested. Viremia occurred 1-4 days post-inoculation (p.i.). Virus was recovered from spleen, liver, lung and various lymph nodes of a horse autopsied on Day 4 p.i. The maximum titer of ...
[Epidemiological study of leptospirosis in New Caledonia]. This epidemiological survey includes the study of human and animal leptospirosis in New Caledonia from clinical cases as well as a systematic serological study about exposed human and animal populations. The results show that this disease is endemic on the whole territory with a few important focuses in agricultural area, especially on the Western coast. Leptospira icterohemorrhagiae is the main serotype and is responsible for serious human leptospirosis. The male farmers constitute the most exposed population, especially from March to May, end of the host season. In order to reduce the import...
Vesicular exanthema of swine virus: isolation and serotyping of field samples. Virus isolation was attempted from 262 field samples of vesicular material collected during the outbreaks of vesicular exanthema of swine in the U.S.A. from 1952-54. Using primary swine kidney culture, viral cytopathogenic agents were isolated from 76.3% of the samples. However, an overall recovery rate of 82.1% was obtained after samples negative in tissue culture were inoculated intradermally in susceptible swine. All vesicular exanthema of swine virus isolates were identified as serotype B51 using complement fixation and serum neutralization tests. Two isolates did not react with antisera t...
Toxigenic characteristics of Clostridium perfringens type C in enterotoxemia of domestic animals. Eleven Clostridium perfringens type C strains isolated from fatal cases of hemorrhagic enterotoxemia of Canadian calves, a piglet, and a foal were studied for the production of soluble antigens. All the isolates from calves and a foal failed to produce delta toxin, but were capable of producing large amounts of lethal beta toxin. A strain isolated from a piglet produced delta, but very little beta toxin. Other differences were relatively minor. The results indicated that young domestic animals may be susceptible to all subtypes of C. perfringens type C. A simple method of using blood agar plat...
The experimental infection of horses with Murray Valley encephalitis and Ross River viruses. Eleven weanling horses were inoculated with Murray Valley encephalitis and Ross River viruses either by intravenous injection or by the bite of Culex annulirostris or Aedes vigilax mosquitoes infected orally. Five of the 11 horses circulated trace amounts of MVE virus for 1 to 5d and they infected 7/408 Cx annulirostris which subsequently fed on them. Haemagglutination-inhibiting antibody persisted at detectable levels for the 24-week observation period. With Ross River virus, only one of 11 horses inoculated developed a viraemia detectable by inoculation of suckling mice but 5 horses containe...
Transmissibility and abortogenic effect of equine viral arteritis in mares. A group of 14 pregnant mares was exposed via contact to 4 mares bred to stallions infected with equine viral arteritis virus. There was a demonstrable febrile response in each donor mare and in 12 of the pregnant mares. All 18 mares became seropositive after exposure. Equine viral arteritis virus was isolated from the nasopharynx of 5 pregnant mares, but not from the donor mares. Ten of the pregnant mares aborted, and virus was isolated from fetal specimens or placenta of 8.
Preliminary characterisation of torovirus-like particles of humans: comparison with Berne virus of horses and Breda virus of calves. Pleomorphic virus-like particles have been observed by electron microscopy in the faeces of children and adults with diarrhoea. Some of these particles were approximately 100 nm in diameter and had a "fringe" of closely applied peplomers approximately 10 nm long; they closely resembled Berne virus of horses and Breda virus of calves, the two representatives of a newly proposed family called the Toroviridae. In one sample a toroidal nucleoprotein-like structure was observed within the particles. For two samples a buoyant density of 1.14 g/ml was determined by centrifugation through a sucrose de...
Bacterial isolates from tracheobronchial aspirates of healthy horses. Of tracheobronchial aspirates from 50 clinically healthy Thoroughbred racehorses, 4 (8%) had aerobic bacteria with recognized pathogenicity, 12 (24%) contained transient bacterial isolates, and 37 (74%) had no bacterial growth. Of tracheobronchial aspirates from 36 pastured, nonracing racehorses, 3 (8%) had bacteria with recognized pathogenicity, 23 (64%) contained transient bacteria, and 10 (28%) had no bacterial growth. Anaerobes were not isolated from 12 of 12 pastured horses. Transient bacteria were isolated more often in the pastured horses.