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.