5 Preventable Infectious Diseases to Worry About This Fall
by Lisa Kivett, DVM, MS, DACVIM
Late Summer and early Fall are the peak of mosquito season here in North Carolina. For this reason, most horses receive “fall shots” in addition to the spring vaccines. While we vary our vaccine recommendations based on the individual horse and farm, there are a few diseases that warrant concern for each and every horse owner. Read on to learn about our “top 5” for Fall 2019!
#1: Eastern Equine Encephalitis:
Eastern Equine Encephalitis is an endemic disease in North Carolina- that means it is ALWAYS here. The disease is transmitted by mosquitoes (side note: did you know a mosquito can travel up to 3 miles?), and cases usually start in July or August and continue through September. Each year, many cases of this disease are reported in North Carolina. It’s worth noting that there are likely lots of cases that go un-reported, either because they died without veterinary attention or because their blood wasn’t collected for testing at the time of death. There are probably more un-reported cases than reported ones!
I have treated somewhere around 20 of these cases over the years. Most of them die, usually during long bouts of seizures, and after days of depressed or neurologic behavior. I’ve been fortunate to have a few EEE cases that survived with intensive care. These horses had been vaccinated, but were overdue for revaccination or hadn’t received their proper boosters as a young horse.
In NC, since we have mosquitoes year-round, keeping horses vaccinated on a 6-month schedule ensures that their immunity always stays high enough to prevent this disease .
Did you know humans can also get EEE from mosquito bites? Just one more reason to dislike mosquitoes!
#2: Rabies
We know rabies is also endemic in our area. There were 303 confirmed cases of animal rabies in North Carolina in 2018. One of these cases was a horse. Rabies is 100% fatal. The first signs of rabies in horses may be choke, mild colic, or problems eating or drinking. The biggest problem with rabies is that it can be spread between animals and from animals to people. If your horse hasn’t received a rabies vaccine within a year, and he appears to have choke or colic, we must be very careful to track everyone that touches the horse, so they can receive post-exposure rabies vaccines if necessary. If the horse dies, it must be tested for rabies to ensure that no humans have been exposed. The only test for rabies is conducted after an animal is dead.
23 humans in the US have died of rabies in the last decade. This is a small number because people exposed can receive post-exposure vaccines. Each year, 30,000 to 60,000 people receive these post-exposure shots!
Horses should receive a rabies vaccination every year. Some research has evaluated the possibility for 3-year rabies vaccines in horses, but the study found that 15% of the horses were “poor responders” to vaccination and a 3-year schedule wouldn’t be OK for them.
#3: West Nile Virus
West Nile cases are usually diagnosed from September through November. We tend to think of West Nile as a threat that has largely passed in this area, but that’s not true! Last year there were five reported cases in NC. Like EEE, the true number of horses with West Nile was likely higher than the number reported.
West Nile symptoms can be very similar to EEE symptoms, but may not be as severe. Odds of survival are slightly higher for West Nile than EEE.
#4: Tetanus
Horses are very sensitive to the bacteria that causes tetanus. This bacteria can enter their bodies through a tiny cut or even a hoof abscess! In most cases of tetanus, the owner didn’t even realize the horse ever had a wound! Horses with tetanus become stiff and painful. They have dramatic neurologic responses to loud noises. The disease is about 50% fatal, even with treatment. Horses who have been vaccinated are more likely to survive, and it is rare to see tetanus in a horse that has received a proper vaccine schedule. Horses should receive a tetanus vaccine every year, which is easy since it is almost always in vaccine combinations with EEE!
#5: Potomac Horse Fever
While we haven’t had Potomac Horse Fever (PHF) in Southern Pines yet, it seems that cases of this disease are reaching farther and farther South from it’s original hotbed in Maryland and Virginia. Earlier this year, cases were found in Eastern North Carolina, and there have been cases treated in Tryon.
PHF causes fever, diarrhea and other GI problems, and often ends in laminitis.
A vaccine for PHF is available and is recommended for horses that travel to Maryland, Virginia, Kentucky, Connecticut, Massachusetts, West Virigina, Washington state, Northwestern NC or near Greenville, NC. The vaccine isn’t always effective, since some horses don’t generate a good immune response to it, but side effects are uncommon and the vaccine is much less dangerous than the disease.