The severe fires throughout California and the west coast over the past three months have exposed humans and animals to unhealthy air containing wildfire smoke and particulates. These particulates can build up in the respiratory system, causing a number of health problems including burning eyes, runny noses and illnesses such as bronchitis. They can also aggravate heart and lung diseases such as congestive heart failure, chronic obstructive pulmonary disease, emphysema and asthma.
Because little information is available to horse owners and even equine veterinarians on the effects on horses of breathing air laden with particulates, UC Davis equine specialists are offering these suggestions to serve as a general guide.
What Is In Smoke?
Smoke is made up of carbon dioxide, carbon monoxide, particulate matter, soot, hydrocarbons and other organic substances including nitrogen oxides and trace minerals. The composition of smoke depends on what is burned; different types of wood, vegetation, plastics, house materials, and other combustibles all produce different compounds when burned. Carbon monoxide, a colorless, odorless gas that is produced in the greatest quantity during the smoldering stages of the fire, can be fatal in high doses.
In general, particulate matter is the major pollutant of concern in wildfire smoke. Particulate is a general term used for a mixture of solid particles and liquid droplets found in the air. Particulates from smoke tend to be very small (less than one micron in diameter), which allows them to reach the deepest airways within the lung. Consequently, particulates in smoke are more of a health concern than the coarser particles that typically make up road dust.
How Smoke Affects Horses
The effects of smoke on horses are similar to effects on humans: irritation of the eyes and respiratory tract, aggravation of conditions like heaves (recurrent airway obstruction), and reduced lung function. High concentrations of particulates can cause persistent cough, increased nasal discharge, wheezing and increased physical effort in breathing. Particulates can also alter the immune system and reduce the ability of the lungs to remove foreign materials, such as pollen and bacteria, to which horses are normally exposed.
Assessing and Treating Smoke Inhalation in Horses
During the recent Napa area fires, UC Davis equine specialists Drs. Joie Watson and Gary Magdesian created a quick reference guide for horse owners to determine potential smoke inhalation damage and a quick reference guide for veterinarians on treatment of smoke inhalation in horses.
In the height of the Napa fires, the UC Davis School of Veterinary Medicine hosted Dr. Elizabeth Woolsey Herbert of the Adelaide (Australia) Plains Equine Clinic. She performed a wet lab on equine burn bandaging for dozens of students, and lectured to more than 100 faculty and students, presenting “Findings and Strategies for Treating Horses Injured in Open Range Fires.” Thank you to the Wiley Online Library for making the publication free online for owners and veterinarians currently dealing with horses with thermal injuries.
Protecting Horses from Air Pollution
• Limit exercise when smoke is visible. Don’t have your horse do activities that increase the airflow in and out of the lungs. This can trigger bronchoconstriction (narrowing of the small airways in the lungs).
• Provide plenty of fresh water close to where your horse eats. Horses drink most of their water within 2 hours of eating hay, so having water close to the feeder increases water consumption. Water keeps the airways moist and facilitates clearance of inhaled particulate matter. This means the windpipe (trachea), large airways (bronchi), and small airways (bronchioles) can move the particulate material breathed in with the smoke. Dry airways make particulate matter stay in the lung and air passages.
• Limit dust exposure by feeding dust-free hay or soak hay before feeding. This reduces the particles in the dust such as mold, fungi, pollens and bacteria that may have difficulty being cleared from the lungs.
• If your horse is coughing or having difficulty breathing, have your horse examined by a veterinarian. A veterinarian can help determine the difference between a reactive airway from smoke and dust versus a bacterial infection and bronchitis or pneumonia. If your horse has a history of having heaves or recurrent airway problems, there is a greater risk of secondary problems such as bacterial pneumonia.
• If your horse has primary or secondary problems with smoke-induced respiratory injury, you should contact your veterinarian who can prescribe specific treatments such as intravenous fluids, bronchodilator drugs, nebulization, or other measures to facilitate hydration of the airway passages. Your veterinarian may also recommend blood tests or other tests to determine whether a secondary bacterial infection has arisen and is contributing to the current respiratory problem.
• Give your horse ample time to recover from smoke-induced airway insult. Airway damage resulting from wildfire smoke takes 4-6 weeks to heal. Ideally, plan on giving your horse that amount of time off from the time when the air quality returns to normal. Attempting exercise may aggravate the condition, delay the healing process, and compromise your horse’s performance for many weeks or months. While we recognize that owners and trainers of sport horses may want to return to work sooner than 4-6 weeks, Dr. Kent Pinkerton* recommends that horses return to exercise no sooner than 2 weeks post smoke-inhalation, following the clearance of the atmosphere of all smoke. Horses, like all other mammals, tend to have an irritation to particles, but will recover from the effects within a few days. With the devastation at San Luis Rey Downs (where 46 horses died, mostly from fire or smoke inhalation), it would be wise to give the horses a break from exercise and then to gradually re-introduce them back to their routine exercise. On December 10, 2017, Dr. Rick Arthur, equine medical director at the UC Davis Kenneth L. Maddy Equine Analytical Chemistry Laboratory and at the California Horse Racing Board, issued an advisory on behalf of the CHRB regarding horses at the Del Mar racetrack.
• Air quality index (AQI) is used to gauge exercise/athlete event recommendations for human athletes. It may be reasonable to use those for equine athletes as well. For example, the National Collegiate Athletic Association lists the following recommendations on their website: “Specifically, schools should consider removing sensitive athletes from outdoor practice or competition venues at an AQI over 100. At AQIs of over 150, all athletes should be closely monitored. All athletes should be removed from outdoor practice or competition venues at AQIs of 200 or above.” During the Napa area fires, the Napa Valley Unified School District used the AQI to determine when students should return to school. They recommended 2 weeks off based on the AQI which was over 400 and took more than 10 days to resume normalcy.
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*Dr. Kent Pinkerton is a professor in both the medical and veterinary medical schools at UC Davis. His research focuses are on the health effects of inhaled environmental air pollutants to alter respiratory, cardiovascular and neurological structure and function. Special areas of interest include the interaction of gases and airborne particles to produce cellular and structural changes within site-specific regions and cells of the respiratory tract in both acute and chronic time frames of exposure.
What Horse Owners Can Do To Monitor Horses Evacuated from Fire Areas
Horses exposed to fire smoke can suffer respiratory injury of varying degrees, ranging from mild irritation to severe smoke inhalation-induced airway or lung damage.
Knowing what is normal versus concerning can help to know whether your horse should be evaluated by a veterinarian.
Respiratory rate at rest should be 12-24 breaths/minute.
Horses should be examined by a veterinarian if any of the following are noted:
Respiratory rate is consistently greater than 30 breaths/minute at rest
Nostrils have obvious flaring
There is obvious increased effort of breathing when watching the horse’s abdomen and rib cage
There is repetitive or deep coughing, OR
Abnormal nasal discharge
Horses should also be monitored for skin and tissue injury, especially for the first few days after exposure.
Vesicular Stomatitis 2020 Updates
By: Emily Nietrzeba, DVM, MPH
Vesicular stomatitis (VS) is a viral infection that can affect horses, cattle, and pigs, and can also but rarely be seen in goats, sheep, and llamas. Disease manifestation of vesicular stomatitis is blister-like lesions commonly around the tongue, mouth, nose, and lips, but can also present around the coronary bands, udder, or sheath. Vesicular stomatitis is a reportable disease in most states, including California, not only because of rapid transmission but because clinical signs of this disease are identical to those caused by foot and mouth disease in cattle and swine, swine vesicular disease, and vesicular exanthema of swine.
VS transmission occurs via direct contact with sores of infected animals or vector-borne blood transmission. Known vectors for VS transmission include black flies, sand flies, and biting midges (Culicoides spp.), which have been implicated as the likely source of infection in most recent positive premises. Infected animals must be promptly isolated to reduce intra-herd transmission, and positive premises are quarantined for 14 days following the onset of lesions of the last affected animal. Biosecurity measures and vector mitigation efforts are frequently implemented on infected premises to reduce within-herd spread of the virus. No specific treatment for VS is indicated aside from supportive care, usually consisting of pain management and soft feeds in the presence of perioral lesions.
The 2020 VS outbreak began on April 13, 2020, when the National Veterinary Services Laboratories (NVSL) in Ames, Iowa confirmed the first VS-positive premises in Dona Ana County, New Mexico. Arizona, Texas, Kansas, Nebraska, and Oklahoma subsequently broke with VS cases which were confirmed by NVSL on April 22, 2020 (Cochise County, Arizona, April 23, 2020 (Starr County, Texas), June 16, 2020 (Butler County, Kansas), June 24, 2020 (Buffalo County, Nebraska), and July 7, 2020 (Washington County, Oklahoma).
As of July 7, 2020, 122 VS-affected premises have been identified (92 confirmed positive, 30 suspect). One hundred fifteen (115) of these premises had only equine species clinically affected and four premises had clinically affected cattle (McMullen, Starr, and Zapata Counties, Texas). Arizona has identified 19 affected premises (18 confirmed positive, one suspect) in seven counties (Apache, Cochise, Gila, Maricopa, Pima, Pinal, and Santa Cruz Counties). Kansas has identified 74 affected premises (48 confirmed positive, 26 suspect) in seven counties (Butler, Cowley, Greenwood, Marion, Montgomery, Sedgwick, Sumner Counties). Nebraska has identified one affected premises in one county (Buffalo County). New Mexico has identified 16 affected premises (13 confirmed positive, three suspect) in six counties (Bernalillo, De Baca, Dona Ana, Eddy, Grant and Sierra Counties). Oklahoma has identified one affected premises (one confirmed positive) in one county (Washington County). Texas has identified 10 affected premises (10 confirmed positive, 0 suspect) in six counties (El Paso, Hudspeth, Kerr, McMullen, Starr, and Zapata Counties).
There have been a total of 68 previously VS-infected or suspect premises that have completed the quarantine period and been released. The last VS-quarantined premises was released in New Mexico on June 4, 2020 and in Texas on June 8, 2020. Fifty-four (54) premises remain under VS quarantine in Arizona, Kansas, Nebraska, and Oklahoma.
Both VS-Indiana (VS-IN) and VS-New Jersey (VS-NJ) serotypes have been identified during the 2020 outbreak. VS-IN occurred in the U.S. in 2019, while VS-NJ was last isolated in the U.S. in the 2014-2015 outbreak. Both serotypes are known to circulate in endemic cycles in southern Mexico. The last U.S. outbreak involving both serotypes occurred in 1997-1998.
For import into California, all horses, cattle, sheep, goat and swine originating from any state where vesicular stomatitis has been diagnosed (except cattle and swine transported directly to slaughter) must be accompanied by a health certificate (Certificate of Veterinary Inspection) signed by an accredited veterinarian that includes the following statement:
“I have examined all the animals identified on this certificate within 7 days of shipment date and found them to be free from signs of Vesicular Stomatitis (VS). During the last fourteen (14) days, these animals have not been exposed to VS nor located on a VS confirmed or a VS suspected premises.”
West Nile Virus 2020 Updates
By: Emily Nietrzeba, DVM, MPH
The first 2020 case of equine West Nile Virus (WNV) in California has been confirmed in Amador County. A 20-year-old Quarter Horse gelding displaying acute severe neurological signs with unknown vaccination history was confirmed positive for WNV on June 26, 2020. The gelding is currently alive.
West Nile Virus is the leading cause of arthropod-borne encephalitis (brain inflammation) in horses and humans in the United States, with horses representing 96.9% of all non-human mammalian cases. The virus is present in all 48 continental states, Mexico, and Canada, and is transmitted from avian reservoir hosts to mammals by a variety of mosquito species.
It is important to remember that both humans and horses are considered dead-end hosts for WNV and the virus is not directly contagious from horse to horse or horse to human. WNV vaccination is considered a core vaccination by the American Association of Equine Practitioners and an essential standard of care for all horses in North America.
This is an excellent opportunity to remind friends and colleagues of the importance of developing and adhering to a protective vaccination program with their veterinarian, and to discuss vector control measures at home and on farm. In addition to minimizing equine (and human) exposure to mosquitos during peak feeding periods of dawn and dusk and appropriate application of mosquito repellant, effective mosquito abatement recommendations include:
Draining unnecessary standing water found in wheelbarrows, tires, etc.
Cleaning water containers at least weekly (i.e., bird baths, plant saucers)
Scheduling pasture irrigation to minimize standing water
Keeping swimming pools optimally chlorinated and draining water from pool covers
Stocking of water tanks with fish that consume mosquito larvae (Contact local mosquito control for assistance) or use mosquito “dunk” available at hardware stores
First 2020 Case of Equine West Nile Virus in California
The first 2020 case of equine West Nile Virus in California has been confirmed in Amador County. A 20-year-old Quarter Horse gelding displaying acute severe neurological signs with unknown vaccination history was confirmed positive for WNV on June 26, 2020. The gelding is currently alive.
Please contact your veterinarian to set up a protective vaccination program, and to discuss vector control measures on your ranch/farm.
