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.
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.
Lymphadenopathy-associated virus: from molecular biology to pathogenicity. Recent data indicate that the lymphadenopathy-associated virus (LAV) is morphologically similar to animal lentiviruses, such as equine infectious anemia and visna viruses. This finding, together with the cross-reactivity of the core proteins of LAV with those of the equine infectious anemia virus and a similarity in genome structure and biological properties, allows LAV to be placed in the retroviral subfamily of Lentivirinae. Molecular data indicate a high degree of genetic variation of the virus, especially in the envelope gene, which have important implications for the origin of the virus (...
Identification and characteristics of staphylococci isolated from lesions and normal skin of horses. One hundred and twenty eight strains of Staphylococcus from lesions, mostly of the skin, in horses were identified and compared with 29 strains isolated from the healthy skin. The pathogenic species Staphylococcus aureus, S. intermedius and S. hyicus were found almost exclusively in lesions. Other species such as S. xylosus and S. sciuri were more frequently found on the healthy skin than in lesions. The S. aureus strains formed a very heterogeneous collection. Many of these strains were staphylokinase positive and rapidly coagulated bovine plasma. Such strains are rarely found in other animal...
Production and biological properties of M-protein of Streptococcus equi. The production of M-protein antigen of Streptococcus equi was studied during in vitro growth in equine blood and in various media. Of 11 S equi strains studied, seven which had initially possessed 0.04 mg or less M-protein per 10 mg of streptococcal cell extract showed an increase in M-protein content after successive culture in heparinised horse blood. Maximum proliferation occurred in Todd-Hewitt (TH) medium with added 0.2 per cent w/v glucose when compared with TH medium alone or TH medium with 2 per cent w/v sucrose, starch, neopeptone or normal horse serum. The M-protein of these strains ...
Isolation, experimental transmission, and characterization of causative agent of Potomac horse fever. Potomac horse fever, a disease characterized by fever, anorexia, leukopenia, and occasional diarrhea, is fatal in approximately 30 percent of affected animals. The seasonal occurrence of the disease (June to October) and evidence of antibodies to the rickettsia Ehrlichia sennetsu in the serum of convalescing horses suggested that a related rickettsia might be the causative agent. Such an agent was isolated in cultured blood monocytes from an experimentally infected pony. This intracytoplasmic organism was adapted to growth in primary cultures of canine blood monocytes. A healthy pony inoculate...
Pathogenicity of equine herpesvirus 1 subtype 2 for foals and adult pony mares. Three pony mares and 4 pony foals were inoculated with a subtype 2 strain of equine herpesvirus 1. Foals had periods of fever 12 h and 2.5 days after inoculation and leukopenia, involving both neutrophils and lymphocytes, followed by leukocytosis. Mares had transient fever and leukopenia 24 hours after inoculation that were less severe than in foals. An increase in circulating virus-neutralizing antibody was seen in 2 of 3 inoculated mares, but not in foals. Attempts to isolate virus from blood were unsuccessful. These studies show that equine herpesvirus 1 subtype 2 is a mild pathogen for pon...
Streptococcus durans: an unexpected enteropathogen of foals. Streptococcus durans was isolated from a foal with profuse watery diarrhea and caused a similar syndrome when inoculated into foals via the orogastric route. The most consistent and striking histological feature was the extensive colonization of the mucosal surface of the small intestine by S. durans. Associated mucosal changes were mild to modeate, and brush border lactase and alkaline phosphatase production were depressed. S. durans also induced acute diarrhea in young gnotobiotic piglets. Mucosal changes were mild and, as with foals, the mucosal surface of the small intestine was colonized ...
Staphylococcus hyicus in skin lesions of horses. Staphylococcus hyicus (subspecies hyicus) was isolated as the only pathogenic organism from two independent cases of dermatitis of the lower parts of the limbs (grease heel) in horses. The organism was recovered together with other pathogenic staphylococci from similar conditions in two other horses of different origins. These conditions were characterised by epidermolysis, alopecia and crust formation. They responded quickly to antibiotic treatment. The organism was also isolated from a long standing case of "summer eczema" which healed without antibiotic treatment, and from a horse with derm...
The pathogenicity in mice of respiratory, abortion and paresis isolates of equine herpesvirus-1. Eleven isolates of equine herpesvirus-1 (subtype 1) all infected the brain following intracerebral inoculation of 2 d.o. mice. Most isolates were from cases of paresis, abortion or respiratory disease in the U.K., but established strains were also included. They divided into two subgroups. The 5 less pathogenic isolates were characterized by being restricted predominantly to the olfactory lobes. The 6 pathogenic isolates included the three known to cause equine paresis and were detected in neurones throughout the brain as well as giving rise to viraemia and infecting bronchial and renal epithe...
Experimental infections of horses with Legionella pneumophila. Attempts to infect horses with Legionella pneumophila were undertaken to determine pathogenicity and to evaluate the possibility that horses serve as a reservoir for the organism. A previous study showed that the prevalence of antibodies to L pneumophila in the equine population exceeded 30% of over 600 sera examined. Horses were infected experimentally with the Philadelphia 1 or Bloomington 2 strain of L pneumophila IV or by aerosolization. Signs of clinical illness were restricted to a transient febrile response. A transient decrease in circulating lymphocytes occurred 2 days after inoculati...
Characterization of the major antigens of Haemophilus equigenitalis (contagious equine metritis organism). Immunoelectrophoresis of ultrasonically disrupted Haemophilus equigenitalis (contagious equine metritis organism) cells against rabbit and equine antisera disclosed at least 11 precipitating antigens. Two of these, a polysaccharide and a lipopolysaccharide-protein complex, were of high molecular weight and located on the cell surface. The remaining antigens were intracellular and were small- to medium-sized proteins. The surface antigens were the most significant in relation to the serological response in infected horses. They also reacted with sera from apparently healthy cattle, but the reas...
Types of Pseudomonas aeruginosa isolated from horses. Pseudomonas aeruginosa isolates from equine clinical material were categorised according to their serotype and phage type. Epidemiological evidence showed that serotypes 02a, 03, 04, 06, 09 and 010 were the cause of genital and non-genital infections; somatic type 03 accounted for 50 per cent of isolates. The laboratory tests used were of no value in predicting whether or not a particular isolate was likely to be a venereal pathogen, but all the serotypes encountered had the potential to be pathogenic, given a favourable environment in which to multiply.
Phagocytosis and intracellular killing of the contagious equine metritis organism by equine neutrophils in serum. Equine neutrophils were combined with Haemophilus equigenitalis (contagious equine metritis organism; CEMO) or Escherichia coli in low- and high-antibody-titer serum to evaluate the neutrophils ability to phagocytize and kill these bacteria. More E. coli than CEMO were phagocytized at each time period. After 120 min in low-antibody-titer serum, 56.3% of the E. coli and 34.3% of the CEMO were phagocytized. A total of 45% of CEMO and 74.9% of E. coli were phagocytized by 120 min when neutrophils were in high-antibody-titer serum. More than 75% of the ingested E. coli and 90% of the ingested CEMO...
Virulence and in vitro growth of a cell-adapted strain of equine infectious anemia virus after serial passage in ponies. Five serial passages of a cell-adapted strain of equine infectious anemia (EIA) virus were conducted in Shetland ponies. The 13 recipient ponies became agar-gel immunodiffusion test-positive by 25 days after they were inoculated. The virulence of the cell-adapted strain of EIA virus markedly increased through 3 serial passages, although individual variation within passages was high. The 1st serial-passage recipient remained afebrile through 200 days, whereas a febrile episode occurred about every 185, 44, 35, and 33 days in the 2nd, 3rd, 4th, and 5th serial-passage recipients, respectively. Se...
Experimental Salmonella anatum infection in horses. Salmonella anatum was given orally to 8 horses on 11 occasions in doses ranging from 9.5 X 10(6) to 8.8 X 10(11) organisms. Four distinct syndromes were induced based upon clinical, laboratory and pathological findings: (1) asymptomatic; (2) moderate clinical signs with or without changes in faecal consistency; (3) fever, depression, anorexia with unstructured or diarrhoeic faeces; and (4) septicaemia with or without diarrhoea, and peripheral circulatory failure. All animals excreted the organism. The peak temperature preceded the onset of diarrhoea by 1 or 2 days. Changes in faecal consistenc...
[Effect of low pH values on the infectivity and neuraminidase activity of human and animal strains of influenza virus type A]. The influence of acidic pH on the infectivity and neuraminidase activity of human, equine and avian type A influenza virus strains has been studied. Following exposure to pH 3 human and equine strains lost their infectivity completely, whereas all investigated strains of the subtypes Hav6N2 and Hav7Neq2 retained a certain amount of infectivity. In contrast to human and equine strains the avian strains retained also 38% of their original neuraminidase activity after acidic treatment. Partial retention of infectivity and the relative stability of the neuraminidase following exposure to acidic pH...
Venezuelan equine encephalitis virus: horse virulence of P-676 and MF-8 small and minute plaques. The P-676 and MF-8 epizootic strains of Venezuelan equine encephalitis (VEE) virus were found to contain a minute plaque (MP), different from the predominant small plaque (SP) present in these virus strains. The MP and SP were stable after passages in Vero cells, mice, or horses. Equines were inoculated with the SP or MP of the P-676 and MF-8 strains. Inoculation of either P-676 SP or MP into horses induced high fever and viremia but no signs of encephalitis or death. Four horses infected with MF-8 SP became very ill, with high fever and viremia; three of the inoculated animals died. Four hors...