HORSE KEEPING

ALBERTA HORSE HEALTH UPDATE SPRING 2022

The latest on disease events specific to Alberta

BY MARY H. BELL, V.M.D.

Spring is the time for horses to shed the long hair and for their owners to provide preventative health care in anticipation of the fun to come. It may consist of riding with friends, taking clinics, competing, camping in the mountains or simply exploring a warmer world with a horse. Whatever it is, this is the time that we prepare our horse(s) for the months to come.

Now is a time to have our horses’ teeth checked, give them appropriate vaccinations, have Equine Infectious Anemia (EIA) test (usually referred to as a Coggins Test but now is an Elisa Test), and to have a fecal count done in order to identify and deworm shedders. These are things to discuss with your veterinarian and determine the best choices for your horse(s). In this article, we will update you on disease events for which we have confirmed reports specific to Alberta in the last year and to go into simple detail about transmission of these diseases. We will also share an exciting research initiative for Potomac Horse Fever, a disease that has certainly taken its toll on several Alberta horses and their owners.

When we look at the Alberta herd in 2021 and to January 6, 2022, we can check diseases that are federally reported on our Canadian Animal Health Surveillance System (CAHSS) website. Click on the Equine Network icon, scroll down, and select the Equine Diseases Dashboard. It includes diseases that are reportable and immediately notifiable in all of Canada. In Alberta, there were an alarming 110 cases of EIA and one reported case of West Nile Virus (WNV). Just as with the current situation with COVID-19, the actual numbers are higher than those confirmed by laboratory tests.

Although we are not yet at a breaking point, let me share why this is an alarming EIA number. The World Organization for Animal Health (OIE) has determined that countries where EIA becomes common are listed as such. Other countries determine the safest way to ensure those diseases never enter their country. If EIA is determined to be common in Canada, it will complicate the ease with which horses move back and forth across national borders. This would make selling Canadian horses, being able to travel across borders with horses and having horses from other countries enter Canada for competition, almost impossible.

EIA is a viral blood-borne disease in horses similar to AIDS in humans. There is no vaccination, and horses that survive remain life-time carriers. Therefore, horses that test positive must be euthanized to stop the spread. This disease spreads when contaminated blood from an infected horse enters the body of a healthy horse. This transfer can occur by biting flies, contaminated needles, syringes, IV tubing or any other piece of equipment containing the blood of an infected horse and goes into the body of another horse. Although transfer through human actions can be avoided, biting flies are more difficult to avoid. The best way to ensure your horse remains free of EIA is to test for it, test any potential new purchase and avoid facilities that do not test for this disease. It is imperative to avoid contact with horses that are not tested.

West Nile Virus is another bloodborne disease that affects horses, humans and birds. It is carried mainly by birds. The mosquito bites an infected bird and then bites the horse or the human. The horse does not have enough virus in its blood for a mosquito to pick up the virus from biting an infected horse. The horse is called a “dead end host” because no disease can be transferred from a sick horse to a bird, human or horse. The virus produces inflammation of the brain and spinal cord. Signs of WNV are fever, dullness, loss of appetite and incoordination. Luckily, regular vaccination for WNV provides good protection.

Other equine diseases do not have mandatory reporting in Alberta. They are reported to CAHSS following a test confirming the disease and at the discretion of the veterinarian. One outbreak of Equine Influenza (EI) was reported, as well as one case of Equine Herpes Myeloencephalopathy (EHM), the neurological form of Equine Herpes Virus 1 (EHV1).

Recently there was an outbreak of EI affecting a number of horses in the Edmonton, area, and it was reported in November. EI is a viral disease that is spread from horse to horse. Vaccination provides good protection from this disease.

A single case of EHM was reported in June. This disease can also spread from horse to horse. Although vaccination is an effective means of preventing the upper respiratory disease caused by Equine Herpes Virus 1 and 4 (EHV 1;4), there is no vaccine that prevents the neurological form of this disease. Good biosecurity is an important component in preventing spread directly or indirectly from horse to

Make a plan to protect your horse this year from several debilitating or life-threatening diseases.

horse. More information about these two viruses, their clinical signs, means of transmission, and prevention can be found on the CAHSS website.

The University of Calgary, Faculty of Veterinary Medicine, has initiated two studies, funded by the University of Calgary Faculty of Veterinary Medicine Clinical Research Fund, to determine the prevalence and geographic distribution of Potomac Horse Fever (PHF) in Alberta. Recently, there has been an increase in the number of cases in Alberta and an increase in locations where they are occurring. PHF is caused by a bacterium, Neorickettsia.

PHF has a variety of clinical signs and various levels of severity. Signs include fever, depression, decreased appetite, and may also include colic and/or diarrhea. In pastured horses, diarrhea may be the first indication that there is a problem. Some horses develop laminitis. There is a successful treatment that works best when these cases are caught early. PHF is spread from freshwater by snails and water insects including mayflies and dragonflies. Horses consume the dead infected insects in hay, grain, pasture, or drinking water.

There are some cases in Alberta with these clinical signs in which there is no diagnosis. A new species of Neorickettsia has recently been identified in eastern Ontario. It may be that some of the horses with typical clinical signs of PHF where no organism is found, may be suffering from a new species of Neorickettsia that has not been identified. A new study consists of collecting blood samples from horses throughout Alberta to determine if they have been exposed to PHF. This gives an idea of the geographical range of the disease. It includes collecting samples from horses with clinical signs similar to PHF in an attempt to determine if Alberta has a new species and evaluating the historical postmortem samples of horses with undiagnosed inflammation of the intestine for PHF.

This article has only covered diseases that have been confirmed by laboratory testing and reported to CAHSS. We hope you can form a plan, perhaps in collaboration with your veterinarian, that is appropriate for your horse or your farm for the 2022 year. We wish you a wonderful year with healthy horses and lots of equine enjoyment. AB