How to deal with ticks on horses, and what health issues to watch for
TICK CONTROL AND REMOVAL
To remove a tick, make sure you get the head and mouthparts, if the tick’s head is already embedded in the skin. “Dispose of ticks by crushing, or put them in a jar with alcohol in it (and a lid), like we do here at our vet clinic,” says Boos. “You can throw that away as it becomes full. You can also burn ticks you collect off the horse. If you simply throw them into a garbage can they will just climb out and go looking for another host.” Ticks that are not yet engorged with blood are very mobile and tough; you can’t squash them by stepping on them. It takes sharp pressure to crush a tick.
For tick control, Nelson recommends grooming on a regular basis, ideally every day, but at least several times a week. “If you need to kill ticks on horses, ivermectin will kill the ones that are latched on, ingesting blood. Deworming with ivermectin or moxydectin kills embedded ticks as well as worms. You can also use a good flea and tick spray. Active ingredients in these are usually pyrethrins. Just follow directions on the products. You can get these from your farm and feed store over the counter,” she says.
The only labeled tick product, with FDA approval for use on horses, is Ultra Boss, according to Boos. “This works well for ticks, lice and flies. It comes in a thick liquid and you apply about 30 cc along the mane and croup area for a mature horse, and a smaller dose for young horses. I have seen horses occasionally have a skin reaction to this product; you would not want that along their back if you are riding them.” This is why it’s best to put it just along the mane and croup rather than down the midline of the back. It moves over the skin via oil secreted by the oil glands.
“One application lasts up to a month for tick control. People who use it for fly or lice control can apply it every two weeks for those parasites but it is labeled for 30 days for ticks. Off-label, people use the tick spray for dogs, and it’s fairly effective. EquiSpot is another product that sometimes works for ticks. The winter ticks in our area don’t seem to be affected by this one, however. We see this particular type of tick in the region around Devil’s Tower,” Boos says.
Spring is tick season, when newly-emerged nymphs and adults seek a host. Dr. Tia Nelson, a veterinarian in Helena, Montana, says some ticks are a problem year round, however. “Some of the worst infestations I’ve seen have been in January.”
Some species spend their entire life on the host, whereas others pass different stages on successive hosts, says Russ Daly, extension veterinarian and associate professor, South Dakota State University. Eggs are laid in the soil, and young ticks crawl onto bushes and attach themselves to a passing host. Adult females suck blood or lymph from the host and then drop to the ground to lay eggs. Complete eradication of ticks is difficult because many species live on several hosts, including wild animals, and adult ticks can live for weeks or months apart from a host.
Daly says ticks are often found on horses, especially those pastured or ridden in brushy areas. “Most horse owners find it unpleasant to discover ticks crawling on their horses, especially if ticks are attached and engorged with blood. Ticks can cause skin irritation and introduce bacterial skin infections–and small abscesses. Discomfort and itchiness may cause the horse to rub those areas where ticks are attached,” he says.
“Ticks feed on blood and may cause anemia in severe infestations, with the horse becoming weak from loss of blood. Anemia from heavy tick infestation doesn’t happen very often in adult horses but it can certainly happen in young foals,” says Daly.
Ticks are the main carriers and spreaders of many protozoal diseases; the protozoa survive from one generation to another in ticks by infecting their eggs. One example is piroplasmosis, which is endemic to much of the world, but that appears only sporadically in the United States. Symptoms of piroplasmosis include lethargy, reduced performance, pale mucous membranes, fever, jaundice, anorexia, and digestive problems including colic, constipation, or diarrhea. Since many of those symptoms are common in other diseases, a blood test is required to positively identify it.
Ticks can also spread diseases caused by bacteria and viruses. Lyme disease is caused by bacteria carried by tiny deer ticks that use mice (and packrats in some western regions) as one host in a multiple-host life cycle.
Dr. Liz Boos, Belle Fourche Veterinary Clinic, Belle Fourche, South Dakota, says a parasite, Anaplasma phagocytophila, carried by deer ticks and black-legged ticks, causes anaplasmosis. The presence of the parasite makes itself known by fever, typically accompanied by limb swelling, and the appearance of small hemorrhages on the mucous membranes of the nose, mouth, eyes and/or vulva. Much less commonly, signs of incoordination, muscle inflammation or digestive tract pain may be observed.
“These [types of ticks] are not common in my area, but when you get into Wisconsin, Minnesota and regions farther south and east you might see problems. Luckily we don’t have much trouble here with Lyme disease either. Occasionally I’ll see horses with an intermittent fever and we’ve tested a few times for Lyme disease but have not been able to find it,” says Boos.
“We are fortunate that Lyme disease is currently not prevalent in our area,” says Daly. “The disease we’d be more concerned about is tularemia–a bacterial infection found in rabbits and rodents. The ticks that live on them fall off, reproduce and may bite other animals or humans. With tularemia, young foals seem most susceptible because of their immature immune systems. Signs in a foal would be general infection throughout the body; the foal is very dull. If a foal has ticks and seems sick, a veterinarian should be consulted for diagnosis and treatment. If a horse gets tularemia this is a tip-off that we also need to be concerned about ourselves, if we get bitten by ticks,” he says.
“Once in a while we’ll see something called tick paralysis. The horse (or dog, or cow) bitten by a tick (or with a tick embedded) has generalized weakness, unable to move. Some ticks produce a toxin that affects the nervous system. Luckily, if affected animals are not too debilitated when found in this condition, removing the ticks may enable those animals to recover,” says Daly.
Dr. Angela Pelzel-McCluskey, USDA-APHIS Veterinary Services, Fort Collins, Colorado, has seen tick paralysis in Texas, caused by many species of ticks. “There seems to be something in tick saliva that causes some cattle and horses to become paralyzed. When I was in practice in Texas, we found ticks in the ear canals, or under the armpits in affected horses. The horse would show neurologic signs, droopy ear, fever, etc. I’ve seen this occur with a single tick bite, though often the horse has multiple ticks. If you find ticks on a horse with these signs, I’d suspect tick paralysis. We don’t know why some horses develop this problem and others do not. It may be related to the horse’s immune system reacting to what’s in the tick saliva,” she says.
Nelson has seen horses loaded with ticks, and one that was horribly tick-infested. “He had a hock laceration and had to be hospitalized for a month for medical treatment, bandage changes, etc. I was stroking his neck and felt many little lumps. Looking closely, I saw he was covered with ticks. I marked out a spot on his shoulder (near the withers) about the size of my hand, and counted over 200 ticks in that area. They were still small, but I had never seen anything like this,” she says.
“We treated that horse with ivermectin, which killed the ticks that were attached and sucking blood, then sprayed him thoroughly with a pet spray for fleas and ticks. After that, part of his treatment was daily grooming and tick picking, since more ticks kept appearing. Also, because he was so infested, we gave him an immune stimulus. I suspect he had very little resistance to ticks. I’ve seen herds of horses in which only one horse had lots of ticks—many more than the others,” says Nelson. Some horses may be more susceptible, for some reason, just as some cattle are more susceptible to lice.
Several kinds of ticks parasitize horses. Small deer ticks can be hard to see. Most common are the larger “dog ticks” or “wood ticks” that are usually red-brown and flat, until they start to swell with blood after attaching to the horse. By the time they fill with blood, ready to drop off and deposit eggs, they are the size of pie cherries or small marbles and look purple. Daly advises horse owners to check for ticks daily when horses travel through brush, tall grass or weeds.
All ticks grab onto any parts of the body that brush against foliage, then crawl to a protected area to attach and suck blood. “They often attach at the throatlatch, under the mane, around ears, neck and belly–the undersides of the horse. Places to check include behind the elbow, around the sheath or udder, between the hind legs in the groin area, alongside or under the tail, etc.” says Daly. If you miss one during grooming checks, it will suck blood and become larger.
“April is a big month for ticks. By late summer ticks are not as prevalent (if it’s been hot), but in spring they are eager to find a host. Even if horses are just out grazing and not ridden, they need to be checked periodically for ticks,” Daly says.