Mumps epididymo-orchitis with prolonged detection of virus in semen and the development of anti-sperm antibodies.

Epididymo-orchitis is the most common complication of mumps in post-pubertal men. A case of MMR vaccine failure, in whom mumps and mumps-associated unilateral epididymo-orchitis developed, is presented in this article. Mumps virus was isolated from the semen 14 days after onset and mumps RNA was detected in semen for up to 40 days using RT-PCR. Epididymo-orchitis was associated with transient but significant reduction in sperm count and severe abnormalities in sperm morphology. It also led to the appearance of anti-sperm antibodies, which may have potential long-term adverse effects on the patient's fertility. Sequencing of the SH gene of the virus showed this to be a new mumps genotype distinct from the virus circulating currently in the UK.