Transmissibility of the contagious equine metritis organism for the cat

A group of SPF cats were moderately susceptible to the causal organism of contagious equine metritis (CEM) following intra-uterine or intrapreputial challenge with an Irish streptomycin resistant strain isolated from a clinically infected mare. Subclinical infections were established in only 50% of the cats, none of which became long-term carriers of the organism. Cytological examination of vaginal smears was of no diagnostic value in confirming infection in inapparently infected cats. Bacteriological responses after primary or secondary challenge with the CEM organism were essentially similar, with one exception, a female cat in which there was possible evidence of local immunity persisting after the primary infection. Efforts to reactivate shedding subsequent to the immediate post-challenge period were unsuccessful. Throughout the experimental period, the cats remained sero-negative to the complement-fixation test, and they failed to develop any significant increase in the levels of antibody activity as measured by the kinetics-based ELISA or KELA system. On day 89 after primary challenge, the cats were euthanized and various sites in the genitourinary tract and the internal iliac lymphatic glands subjected to bacteriological and pathological examination for evidence of CEM infection with negative results. The findings of this study, although establishing the transmissibility of the CEM organism for the cat, demonstrate the limited value of this species as an experimental model system for the disease in the horse.     

Responses of equine neutrophils to contagious equine metritis organism and its lipopolysaccharides

Morphology and function of equine neutrophils were evaluated after combination with contagious equine metritis organism (CEMO) or 1 of 2 CEMO lipopolysaccharides (LPS). The 2 LPS (LPS-a; LPS-p) isolated from the CEMO contained 14- and 16-carbon fatty acids, ketodeoxyoctanate, hexose, and heptose, but were morphologically distinct. Neutrophils exposed to LPS had fewer granules, whereas those exposed to CEMO had more granules than did the controls (phosphate-buffered saline solution). Neutrophil iodination was significantly increased with 10 and 25 micrograms of LPS-a, but not significantly altered by LPS-p or CEMO. Staphylococcus aureus ingestion was not influenced by CEMO and was mildly decreased by LPS-a. These results indicate that CEMO may have at least 2 functionally and morphologically distinct, but chemically similar, LPS and that 1 of these LPS (LPS-a) may enhance neutrophil killing by stimulating neutrophil iodinating mechanisms.     

A passive haemagglutination test for the detection of antibodies to the contagious equine metritis organism.

A passive haemagglutination test (PHT) which has been developed for the detection of antibodies to the contagious equine metritis organism (CEMO) in serum is described. Samples from each of 30 mares with metritis were positive with titres in the range 256 to 4096. Samples from each of 239 clinically normal mares and 30 colts and fillies believed not to have been exposed to CEMO were negative with titres of less than 256, the majority of samples (97 per cent) showing a titre of 32 or less.     

The experimental infection of ponies with contagious equine metritis

Four pony mares were readily infected with the organism of contagious equine metritis by intracervical inoculation and one by coitus with an infected stallion. Infected mares developed an acute endometritis with local destruction of the endometrial epithelium. In 2 experimentally infected mares, infection appeared to have been spontaneously eliminated from the genital tract within 3 to 4 weeks. A third mare however remained persistently infected in the clitoral fossa over a long period and was a symptomless carrier. Four pony stallions were readily infected in the urethral fossa and the organism survived for varying periods without giving rise to any signs of infection. From 2 of these animals it appeared eventually to have been eliminated spontaneously. An experimentally infected stallion transmitted infection to a healthy mare by coitus. Bacteriological examination of infected pony stallions may occassionally give false negative results and fail to reveal the organism in the external genitalia. Repeated bacteriological examinations need to be undertaken before it can be concluded that a stallion is free of infection.     

Development of a PCR test for rapid diagnosis of contagious equine metritis

In order to establish a rapid diagnostic method for contagious equine metritis (CEM), we developed and evaluated a polymerase chain reaction (PCR) test. Species-specific PCR primer sets were derived from the DNA sequence of a cloned DNA fragment of Taylorella equigenitalis that did not hybridize with the genome of a taxomonically related species, Oligella urethralis. Single step PCR with primer set P1-N2 and two-step semi-nested PCR with primer sets P1-N2 and P2-N2 detected as low as 100 and 10 CFU of the bacteria, respectively. Single-step PCR detected T. equigenitalis from genital swabs of experimentally infected mares with sensitivity comparable to that of bacterial isolation. Furthermore, two-step PCR was more sensitive than the culture method. Upon examination of field samples, 12 out of 3,123 samples were positive by single-step PCR while only 2 were positive by bacterial culture. The 12 PCR-positive samples originated from 5 mares, of which 3 animals were considered to be carriers based on previous bacteriologic and serologic diagnoses for CEM. The PCR test described in this study would provide a specific and highly sensitive tool for the rapid diagnosis of CEM.     

Survival of contagious equine metritis bacteria in transport media

Survival of bacteria that cause contagious equine metritis (CEM) was evaluated in Amies modified transport (AMT) medium, in AMT medium with charcoal, and in Stuart transport medium at 37, 22, 4, and -70 C. The CEM bacteria suspended in transport media survived at 22, 4, and -70 C for longer periods in AMT medium with charcoal than they did in AMT and Stuart transport media. In 1 day, the number of bacteria in exudate stored in the absence of any transport medium decreased 15-fold at 22 C and twofold at 4 C. The CEM bacteria were isolated from exudate on cotton-tipped swabs from all three transport media at 4 and -70 C on day 10, the termination of the experiment. However at 4 C, the survival of CEM bacteria was greater in AMT medium with charcoal than it was in AMT and Stuart transport media.     

Specific antibody in the equine genital tract following local immunisation and challenge infection with contagious equine metritis organism (Taylorella equigenitalis)

Antibody in serum, uterine and vaginal secretions was measured following local immunisation and experimental infection with the organism of contagious equine metritis (Taylorella equigenitalis). Intrauterine immunisation with killed T equigenitalis stimulated a systemic IgG titre and a uterine IgA and IgM response. Subsequent challenge with the organism, however, resulted in a characteristic metritis in both control and vaccinated mares. Antibody in serum and secretions was increased following challenge infection, dwarfing the response to immunisation. The local response was restricted to the IgA and IgM classes in both uterine and vaginal secretions. There was no elevation in local IgG antibody, although there was an increase in serum IgG in response to challenge infection. A second experimental challenge, following natural resolution of the initial infection and a period of reimmunisation, resulted in reduced clinical signs and bacterial isolation rates from both control and vaccinated mares, but no absolute protection from infection.     

The causative organism of contagious equine metritis 1977: proposal for a new species to be known as Haemophilus equigenitalis.

The aetiological agent of contagious equine metritis (CEM) has been investigated bacteriologically in a wide range of cultural and conventional biochemical tests, in the eletron microscope, for DNA base composition (36.1 per cent GC), for susceptibility to various antimicrobial agents and antigenically by means of tube and slide agglutination tests. The organism is a fastidious, Gramnegative, non acid-fast coccobacillus which in biochemical tests is very unreactive. In conventional tests, only the oxidase, catalase and phosphatase tests were positive. Dependance on neither X nor V factors could be demonstrated, but some stimulation of growth by X factor was observed. The organism could not be identified with any known species and even allocation to an appropriate characters, we propose the organism as a new species of the genus Haemophilus: H. equigenitalis, type strain NCTC 11184 (61717/77).     

Transmission studies with the contagious equine metritis bacterium in albino Swiss mice

Aspects of experimental transmission of the causal bacterium of contagious equine metritis (CEM) to albino Swiss mice were investigated. Whereas infection was established in the majority of female mice, the organism was recovered from only a limited number of male mice after challenge. No clinical evidence of infection was observed in the experimental mice. There was only one instance of presumptive venereal transmission of the CEM bacterium. One third of infected females conceived and had normal litters.     

Possibilities of clinico-cytological diagnosis in contagious equine metritis (CEM)

Clinical, bacteriological and serological examinations on a 6 years old pony mare were performed. Cytological alterations in the genital tract were also recorded. A cellular reaction was seen after infection with T. equigenitalis. This reaction is an evidence for infection but it is not specific for this organism. Cytological studies should be performed on mares especially in cases of latent infections to complete bacteriological examination and to prevent false positive or negative results.     

Serological and bacteriological survey of three horse studs for contagious equine metritis

A bacteriological and serological survey for evidence of contagious equine metritis (CEM) was made during the 1980 breeding season on 3 horse studs in South Australia with a history of previous infection. Swabs from the clitoral sinus and the cervix were cultured for Haemophilus equigenitalis and serum was screened for antibody using the complement fixation test (CFT) and the enzyme-linked immunosorbent assay (ELISA). The specificity of both tests was greater than 0.99 but the ELISA was more sensitive in detecting antibody in infected mares. On the evidence presented it was concluded that H. equigenitalis is no longer present in the horse studs investigated.     

Contribution to the knowledge of contagious equine metritis in the Federal Republic of Germany

Haemophilus equigenitalis could be isolated repeatedly from seven mares and two stallions (all trotters) of a stud farm in Northern Germany, which had encountered reproductive problems. Morphological, cultural and biochemical identification of H. equigenitalis was confirmed serologically, particularly by positive slide agglutination reactions with specific antibodies adsorbed to protein A-positive staphylococci.     

A rapid microtitration serum agglutination test for the detection of contagious equine metritis antibodies

A microtitration serum agglutination test, based on that used for brucellosis, has been developed to detect antibodies in the sera of horses exposed to the contagious equine metritis (CEM) organism. Two known positive sera were tested 100 times in 15 separate tests. The results were reproducible to within a twofold range. The test is capable of being carried out within 100 min.