Author: admin

Strangles In PEI

A horse farm in Prince Edward Island (Canada) has been quarantined by the owners in response to a strangles outbreak. Two horses at Giddy Up Acres in Owell Cove have been diagnosed, but likely many other horses on the farm have also been exposed.

In addition to quarantining the facility, the owners are taking the temperatures of all 18 horses on the farm twice a day. This is a simple and effective infection control measures as it allows for early identification of infected horses. Since horses that are infected spike a fever a day or two before they become infectious, this type of monitoring, along with proper and prompt isolation of any horse that does develop a fever, can greatly reduce the risk of any further transmission.

The owners are also using other enhanced infection control practices (e.g. using designated clothing in different parts of the barn, disinfecting) and testing all horses in the barn. Specific details about testing weren’t provided, but given their close attention to doing things right, I suspect they are going to aim to get 3 negative nasopharyngeal swabs or nasopharyngeal washes on each horse, which is the standard recommendation to call a horse strangles-free.

The source of this strangles outbreak isn’t know. Strangles is a highly contagious bacterial disease of horses caused by Streptococcus equi. It is an endemic disease in horses and circulates relatively commonly in the horse population. It could have been brought in by a new horse, or picked up from contact with a carrier somewhere off the farm (e.g. at a show) or even on the clothing, hands or equipment of someone like a visitor, farrier or veterinarian who had recent contact with an infected horse. It seems to be fairly uncommon in PEI but it’s certainly there.

The self-imposed quarantine and voluntary use of good infection control practices is great to see. It’s a major hassle for all involved, but it’s an appropriate response, and in stark contrast to some places that try to ignore or hide outbreaks. Addressing an outbreak head-on takes time and money, and often results in negative publicity, yet ultimately it’s what needs to be done to contain an outbreak. The owners of this farm should be given top credit for their approach.


Vaccination And Infection Control Are Non Synonymous

In general, the horse industry is over-reliant on vaccines. Don’t get me wrong, vaccines are useful and are an important aspect of an infectious disease control program. However, they are just one tool and they should not be the first line of defense. Rather, I think we need to change our mindset and consider vaccines as a last line of defense.

Why? Vaccination is not 100% effective. Some vaccines are very good, some are pretty bad, and none protect every horse in every situation. Some horses are not protected at all after vaccination. Sometimes exposure to a large dose of infectious agent can cause disease regardless of vaccination status. Sometimes vaccination can help reduce the severity of disease, but not the likelihood that a horse gets sick and becomes infectious.

When I think about disease control, I think about three main areas:

1) Decreasing exposure

  • If a horse doesn’t get exposed to equine influenza virus, it won’t get influenza. End of story.
  • Decreasing exposure can be fairly easy for some bugs, possible but requiring effort for others, and almost impossible for some. This is the most important overall preventive tool, however, and it should be the first line of defense. A good general infection control program goes a long way to reducing the risk of exposure.

2) Decreasing susceptibility

  • Certain things make horses more likely to get sick if they get exposed to an infectious agent. Some (e.g. young and old age, pregnancy) aren’t avoidable, but others are. We don’t have great data about what increases risk, but things like diet change, stress, pain, high grain diets, overall nutrition, antibiotics, and perhaps administration of other substances like anti-ulcer drugs can presumably play a role. Good general management is therefore a key.
  • Concurrent disease is also a risk. It’s not always avoidable, but measures to reduce the risk of other diseases (be they infectious or non-infectious) and to control certain conditions (e.g. proper management of Cushings) can help. 

3) Increasing resistance

  • This is where vaccination comes in. It’s there to help when efforts to decrease exposure and decrease susceptibility have been surpassed.

So, by no means am I suggesting that vaccination isn’t needed. What I’m saying is it needs to be put into context. Too often, when I ask a horse owner about their farm infection control program they say “I vaccinate against...” When I ask what else they do to prevent infectious diseases, I often get a blank stare in return.

A logical vaccination program combined with a well-designed and practical infection control program can have a major impact on horse health, and we need to do a better job implementing more comprehensive infection control programs on farms, rather than piecemeal, reactionary approaches focused on vaccination and often little else.


Canadian Reportable Equine Diseases, 2019

The Canadian Food Inspection Agency (CFIA) is in charge of federally reportable animal diseases in Canada. Reportable diseases are those that have specific reporting (and usually control) measures that are legislated. The list of reportable diseases is restricted to diseases with particular potential for severe impact on animals, both in terms of health and economic factors, as well as certain diseases transmissible from animals or food to people. The list of reportable diseases in horses is pretty small, and the number of cases identified each year is very low.

Some of the 2019 highlights:

  • Equine infectious anemia (EIA): 19 positive tests out of 52 056 animals tested. There were 13 positive horses in BC, 5 in Alberta and 1 in Quebec.
  • Rabies: One diagnosis: a horse in Manitoba.
  • African Horse Sickness:No cases. Not particularly surprising for an African-insect-borne disease that has never been identified in Canada.
  • Piroplasmosis: No cases, although the ongoing problems in the US are concerning, given the amount of movement of horses between Canada and the US.
  • Contagious equine metritis (CEM): No cases. The disease has not been identified in Canada, although the US outbreak highlights the potential for importation of the disease.  Click here for links to the current import restrictions on horses and horse semen from the US with regard to CEM.
  • Venezuelan equine encephalitis (VEE): No cases. The disease has never been identified in Canada, but the related viruses, eastern and western equine encephalitis (EEE and WEE), have.
  • Vesicular stomatitis (VS): No cases.
  • Anthrax (infection with Bacillus anthracis): No equine cases. (There was a bovine outbreak.)

So, another good year from a reportable disease perspective. It doesn’t mean there aren’t major infectious disease concerns in horses in Canada, but at least things are quiet from the standpoint of these major exotic diseases.