Routine pre-entry health tests have been used in this presentation to examine the incidence of potentially pathogenic organisms in ram semen.
Macquarie Artificial Breeders is a commercial semen processing centre based at Dubbo in central west New South Wales. As part of a routine pre-entry examination, semen samples were submitted to Orange RVL and, more recently, to EMAI, Menangle.
Aseptic techniques were employed in obtaining a semen sample and swab to submit to the lab. With the fact that semen itself is not a sterile article, timing of submissions was critical to obtaining a meaningful result. Any delay in the submission of samples ran the risk of overgrowth and subsequent inability to interpret the samples.
Actinabacillus seminis, along with other pathogenic organisms such as Histophilus somni has been recognized as being associated with ram infertility.
In England in 1991, PJ Heath et al, reported identifying A seminis in a number of clinically fertile rams as well as clinically infertile rams and concluded that A seminis infection may be widespread in the English flock and should be considered with any infertility investigation.
Again in England, JC Low et al conducted a survey in 1995 to establish the prevalence of Actinobacillus seminis in ovine semen and the possible importance of the organism as a cause of ram infertility. A seminis was isolated from three of 16 infertile rams and the infected animals had lesions of the genital tract and produced poor quality semen. A seminis was also isolated from two of 96 fertile rams used as donors of semen for artificial insemination programmes.
The results of semen samples submitted by Macquarie Artificial Breeders are listed below:
In these clinically normal rams, culture of the organisms from semen was not necessarily associated with a decline in the quality of the semen sample.
The number of cases where A seminis was cultured are in line with the survey results of JC Low.
A study by Al-Katib and Dennis in 2005 demonstrated that the intrapreputial and intraurethral routes were the most effective at disseminating infection.
The nasal and conjunctival routes were not associated with the transmission of the organism.
The results of this study were repeated by a similar experiment conducted by VF Saunders et al at EMAI.
This group has also demonstrated that the multiplex PCR was far more successful in the detection of H somni (45/295) than culture (23/295). A seminis was also detected in more semen samples by multiplex PCR (29/295) than culture (13/295) and B ovis was detected in three samples using both PCR and culture. Their conclusion was that this PCR could be used as a complementary test, or alternative to culture of ram semen and other biological samples for the detection B ovis, H somni and A seminis.
The experience at Macquarie Artificial Breeders to antimicrobial therapy with cases identified by semen culture has been equivocal, with about 50% of cases remaining positive to subsequent cultures post treatment.
Long term oral antibiotic therapy has been listed in references as having a higher success rate than short term parenteral treatment, but I have had no experience with this regime.
The conclusions to the observations at Macquarie Artificial Breeders is that the noted prevalence of potentially pathogenic organisms in ram semen is in line with reports from other sources and that response to therapy is also in line with observations by other authors.
The overall prevalence of these organisms in ram semen is low, but can cause infertility in some, but not all cases.
Occasionally, the incidence of infection can increase to significant levels due to poor management practices.