Contagious equine metritis: experimental infection in the donkey.

Contagious equine metritis (CEM) was reproduced in 3 of 4 donkey mares with an Irish streptomycin-resistant strain of Haemophilus equigenitalis isolated from an experimental case of the disease in a pony mare. Although some variability in clinical response occurred, there was no evidence that semen enhanced the clinical severity of the infection. Variable amounts of vaginal discharge and associated inflammatory changes of the vagina and/or cervix, similar to those seen in the horse, were observed. All the affected donkeys made spontaneous clinical recoveries and so far as could be detected, subsequent persistence of H. equigenitalis in the genital tract was of limited duration. Recovery of the bacterium was not associated with oestrus and there was no evidence that it persisted in the clitoral area after it could no longer be cultured from the anterior genital tract. Cytological examination of smears of intra-uterine or cervical swabs was of diagnostic value only during the clinical phase of the infection. Serological responses demonstrated in 3 of the 4 donkey mares by the agglutination, complement-fixation and passive haemagglutination tests, were of low magnitude and short duration. The diagnostic value of the agglutination and complement-fixation tests was limited by the presence of low levels of non-specific reactivity and pronounced anti-complementary reactivity, respectively, in many of the donkey sera. The passive haemagglutination test proved superior for demonstrating elevation in antibody and for confirming infection. The overall results indicate that the donkey has the potential to act as a source of CEM infection and under certain circumstances, could have a role to play in the epidemiology of this disease.

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.

Responses of pony mares to the agent of contagious equine metritis 1977.

Reproduction of contagious equine metritis 1977 in Pony mares was achieved with cultures of an unclassified Gram-negative coccobacillus. Infected mares developed a vaginal discharge and associated inflammatory changes of the cervix and vagina. There was evidence of variation in pathogenicity between different strains of the organism. Although all infected mares made spontaneous clinical recoveries, the Gram-negative coccobacillus persisted in the genital tracts of a considerable proportion for a variable period after challenge. Recovery of the organism was not associated solely with the occurrence of oestrus. None of the mares has carried over infection into the following breeding season. There was no evidence of localization of the organism in the urinary tract. Cytological examination of smears of cervical and urethral swabs was of diagnostic value only during the clinical phase of the infection. A serological response was demonstrable in all mares that became infected after exposure to the Gram-negative coccobacillus. The complement-fixation test gave more specific and clear-cut results than either the agglutination or the antiglobulin test, with which there was a problem with non-specific reactions. The experimental findings indicate the value of the complement-fixation test for confirming recent cases of contagious equine metritis in the mare.

Survival of Haemophilus equigenitalis in different antibiotic-containing semen extenders.

The ability of Haemophilus equigenitalis, the causal agent of contagious equine metritis 1977, to survive in various antibiotic-containing semen extenders was studied at different environmental temperatures. Gentamicin sulphate was found to be markedly superior to ampicillin or a combination of sodium benzyl penicillin and polymyxin B sulphate, Semen treated with the former antibiotic was either sterile at cultural examination or else yielded appreciably fewer colonies of H. equigenitalis than the untreated semen control. Ampicillin had no observable effect on the survival of this organism. Gentamicin was most effective when semen-extender mixtures were held at room temperature rather than at 37 or 4 degrees C. No detrimental effects on sperm motility were observed following the use of the different antibiotic-containing semen extenders in the presence or absence of H. equigenitalis.

Infection patterns in pony mares challenged with the agent of contagious equine metritis 1977.

Contagious equine metritis 1977 was reproduced in pony mares using cultures of the Gram-negative coccobacillus aetiologically associated with the disease. Variability in clinical response was observed in the first of 2 experiments, with the presence of semen, either alone or in an extender, appearing to potentiate the pathogenicity of the challenge strain of the organism. The experimental disease was characterised by a variable degree of vaginal discharge and concomitant inflammatory changes involving the vervix and vagina. Although all of the affected mares recovered spontaneously, a high percentage continued to harbour the Gram-negative coccobacillus in their genital tracts for variable periods after challenge. Shedding of the organism was either relatively constant or intermittent and was not solely related to the oestrous period. Cytological examination of smears of cervical and urethral swabs was of diagnostic value only during the clinical phase of the infection. There was evidence that reinfection of mares could occur after an interval of 2 weeks.