Equine Health Update Issue 1 Volume 16 - Page 15

Lessons learned from the current CEM-outbreak in South Africa Schulman, ML1 and May, CE1, 1 Section of Reproduction, Faculty of Veterinary Science, University of Pretoria Background • The first outbreak of contagious equine metritis (CEM) due to the bacterium Taylorella equigenitalis in South Africa was recognised in April 2011 and reported to the OIE. As a consequence, South Africa lost its CEM-free status. This outbreak report was linked to the importation of the index case (a Warmblood stallion) from Germany. An outbreak was initially suspected following an unofficial test breeding on the index property in Midrand (Gauteng Province) of a Thoroughbred mare using semen collected from the index stallion. Samples from both index animals were confirmed positive for T. equigenitalis after the State was notified and submitted swabs for testing to a reference laboratory in the UK. The index property was quarantined and a traceback was instituted to identify and screen all in-contact animals. This exercise was extended country-wide as it became apparent that indirect venereal transmission via movement of both carrier stallions and chilled semen as well as horizontal transmission via fomites was important in the dispersal of T. equigenitalis from the index property. The Department of Agriculture, Forestry and Fisheries (DAFF) introduced a mandatory nationwide Stallion Screening Programme in June 2011 to identify carrier stallions which was central to assessing the prevalence of T. equigenitalis and the extent of the outbreak. Currently as of December 2013, a total of 39 horses (36 stallions and 3 mares) have been identified and after confirmation of their carrier status were successfully treated under quarantine conditions. All, with the exception of three horses (North West = 2; Western Cape = 1) were identified in Gauteng. Most positive animals have been linked either directly or indirectly to the index premise. The role of horizontal transmission via fomites (e.g. personnel, housing, breeding equipment) has been central and few animals appear to have been directly infected by the venereal route. No evidence of classic transmission at natural cover was recognised, and the cases of venereal transmission were apparently associated with AI using contaminated semen. • • • • 2. Bacteriology and pathogenesis • • • • • CEM control was supported by the current post-entry quarantine protocol 4. Diagnostic methods • • • • • qPCR enabled accurate practical, highthroughput, rapid and economical identification of T. equigenitalis In-treatment qPCR improved therapeutic protocols for T. equigenitalis elimination Stallion screening was a practical and rapid method to ascertain the prevalence of T. equigenitalis Repeat sampling increased the sensitivity of T. equigenitalis detection T. equigenitalis had the greatest predilection for the urethral fossa and sinus in stallions 5. Treatment and management of carrier animals • • 1. Epidemiology • CEM transmission had a strong riskassociation with biosecurity CEM was not exclusively a venereal disease CEM was apparently readily contagious CEM may have persisted for an undefined interval outside the genital tract environment CEM was transmissible via AI using semen diluted with antibiotic-containing extender 3. Disease prevention Lessons learned: • CEM transmission had a strong riskassociation with artificial breeding centres CEM transmission and geographic dispersal were facilitated by artificial breeding CEM transmission was facilitated by housing stallions in close proximity CEM was absent in Thoroughbreds in SA despite exclusive use of natural covering CEM was absent in Arabian and American Saddlehorses in SA • The efficacy and duration of previouslyadvocated treatment protocols was undefined A treatment protocol to eliminate T. equigenitalis was objectively evaluated The treatment process may itself enhance dispersal of T. equigenitalis Topical treatment for T. equigenitalis predisposed to genital colonisation by • Volume 16 no 1 • March 2014 • 15