IN-DEPTH: INFECTIOUS DISEASE OUTBREAK MANAGEMENT


ate on-farm disease control measures. In states where the EHM is not reportable, the SAHO does not have any role in disease control, thus all control efforts are the sole responsibility of the private practitioner. During the last 5 years, regulatory officials across


the U.S. have investigated numerous EHM cases and continue to learn how to most effectively assess risk and manage these incidents while making sci- ence-based decisions. In 2014, the United States Animals Health Association (USAHA) hosted a meeting to discuss the changes in EHM and science- based response options for state animal health offi- cials.2 Subsequently, great efforts have been made to have regulatory responses be science based. However, there are still variations among the regu- latory responses by SAHOs. Ultimately, the pri- vate practitioner invariably plays a critical role in onsite regulatory disease control. In summary, the California EHM regulatory management experience demonstrates that prompt isolation of EHM cases and implementation of baseline premises-level bios- ecurity practices, which are then enhanced upon disease detection, can ensure business continuity and shorter quarantine periods.


Contagious Equine Metritis


In January 2013, a private practitioner evaluating a 17-year-old Lusitano mare with a history of infertil- ity submitted reproductive-tract samples to the Cal- ifornia Animal Health and Food Safety Laboratory for bacterial culture. The culture results confirmed presence of Taylorella equigenitalis, the organism responsible for the foreign animal disease, CEM. During the 2012 breeding season, the index mare was bred by live cover and artificial insemination to a 20-year-old Brazilian-origin Lusitano stallion im- ported in 2003. Testing of the Lusitano stallion confirmed infection with T. equigenitalis. The epidemiologic investigation required tracing


of any mares or stallions potentially exposed to the infected stallion. An exposed stallion is defined as any stallion collected at the stallion station during the 7 days before the infected stallion and the 7 days after the infected stallion. During the 2012 breed- ing season, the infected Lusitano stallion was col- lected at a California stallion station. An exposed mare is defined as any mare bred by live cover or artificial insemination to the infected stallion. The initial epidemiologic investigation identified 11 ex- posed stallions and one exposed mare. The burden- some testing protocols, at the owner’s expense, included collection intervals of three sets of cultures from exposed mares and stallions and live cover of exposed stallions to two certified CEM-negative test mares. During the testing protocols, the exposed horses were under quarantine and unable to be used for breeding. The stallion station that involved this incident had six exposed stallions onsite; according to the stallion station owner, the estimated loss in


338 2016  Vol. 62  AAEP PROCEEDINGS


revenue during the CEM investigation and quaran- tine period was $75,000. One exposed stallion and one exposed mare were subsequently confirmed to be infected with T. equi- genitalis and underwent required treatment and ad- ditional testing protocols. The second infected stallion was a domestic 25-year-old Lipizzaner stal- lion that had semen collected in 2012 at the same facility as the initially identified infected Lusitano stallion. The second infected mare was a domestic, 13-year-old, Andalusian-cross breed that had been artificially inseminated with semen from the in- fected Lusitano stallion in 2012. This mare was found to be pregnant. All test positive animals un- derwent the required additional treatment and test- ing protocols. The National Veterinary Services Laboratory determined that the strain of the T. equi- genitalis from all four infected horses were identical but failed to match to any previously identified strains of T. equigenitalis from the U.S., indicating these cases were not related to any previous U.S. T. equigenitalis cases. Frozen semen collected in 2009 from the index Lusitano stallion was also confirmed to contain T. equigenitalis. The epidemiologic investigation could not determine the time of exposure or source of the infection of this index stallion, given that the private practitioner, who managed the pre-2009 breeding of this stallion in the U.S., had retired and burned his medical records. Fortunately, this inci- dent had limited scope compared with the large mul- tistate outbreak of contagious equine metritis in 2008–2010, which resulted in the detection of 22 T. equigenitalis–infected stallions and five T. equigeni- talis–infected mares at a cost to the industry of $11–16 million.3,4 In summary, an astute private practitioner and laboratory diagnostician detected a foreign animal disease agent and eliminated a potential disease risk to the equine industry. Unfortunately in this incident, the source of infection could not be deter- mined, so continued vigilance is necessary to detect any potentially unidentified carrier animals.


Dual Infection of Racing Quarter Horses With Equine Infectious Anemia and Equine Piroplasmosis Agent


In 2012, the Animal Health Branch of the California Department of Food and Agriculture began investi- gating infections of EIA and EP in the California racing Quarter Horse population. Since 2012, 39 racing Quarter Horses have been confirmed positive for EIA and 21 racing Quarter Horses have been confirmed positive to Theileria equi, the causative agent of EP. Ten of the positive horses had dual EIA and EP infections. One of the dual-infected horses was examined by a private practitioner who had worked with state animal health officials on treating a previously identified T. equi infected horse. The private practitioner contacted the SAHO to report that she had examined a racing Quarter Horse that had severe anemia. The


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