The brown ear tick

The main reason why cattle are dipped weekly in certain parts of South Africa is to prevent East Coast Fever (ECF), carried by the brown ear tick. The disease is a major problem for cattle farmers along the eastern coast of Africa, north of our borders, but was successfully eradicated by intensive cattle dipping more than 50 years ago.
Probably because ECF is no longer a problem in South Africa, the brown ear tick tends to be ignored, although it causes fly strike and abscesses in the ears of calves. It’s also known to parasitise horses, but little has been written about the problems it causes for horse owners.
This is a three-host tick, meaning each phase of its life is spent on a different host, including not only horses and cattle but also game, rodents, hares or even birds. The tick’s immature forms, the larvae and nymphs, stay on the host for only three to four days before dropping off. They can then remain alive in the veld for up to seven months – the mature ticks can last for 14 months or longer. In the old days cattle had to be kept off a farm for 18 months after an ECF outbreak and this was probably linked to the period it takes to eliminate the brown ear tick.
Early in the season, between about October and early December, the tiny larvae attach over horses’ faces, necks and shoulders, forming small hairless bumps causing severe itching. The second stage can feed on horses, cattle or game. In the third or adult stage these fast ticks hang at the top of grass tufts and climb up the legs or muzzle of grazing animals.
The favourite attachment site in horses is the face and neck and adult ticks usually cluster in the mane, forming large scabby masses and causing the horse to scratch itself against fence posts and stable doors.
Running your hand through the mane, you can feel these swellings and bumps and pick off the scabby masses between the hairs without always realising they’re caused by ticks. If you find a mature brown ear tick, you’ll see it’s smaller and more circular than the teardrop-shaped red-legged tick and a uniform glossy brown.
All three phases of the brown ear tick can be found in the ears. Symptoms vary from shaking the head while being ridden to rubbing the base of the ear against poles or fence posts, causing hairless patches or severe bleeding and scabbing of the ear, particularly in foals. Sometimes this can be followed by fly strike with maggots in the ears. Many horses with one drooping ear testify to neglected brown ear tick infestation.
Prevention isn’t easy in farm horses, especially on cattle farms, as regular dipping with registered horse dips doesn’t always work. The brown ear tick is often resistant to permethrin, the main ingredient of many dips registered for horses. Tiguvon Spot-On is very effective in cattle and it’s worth treating your herd with it if you also own horses, to reduce the level of brown ear ticks in the veld. It can be used off-label in horses at a dose of 0,5ml per ear, inserted into or behind the ear. As this dip isn’t registered for horses, it’s best not to treat pregnant mares or foals under the age of six months.
Tick grease around the base of the ear and in the mane is another way of treating veld horses but may be an irritant, causing even more rubbing, swelling of the skin and loss of hair in show horses.
Karbadust, which is registered for horses, can be rubbed into the mane and sprinkled in the ears, but it’s messy. The dense cloud of white dust produced when the horse shakes its head is potentially dangerous if inhaled, so masks and gloves are suggested for application.
Strategic deworming with horse dewormers containing Ivermectin, as soon as you notice the first symptoms of brown ear tick infestation in early summer and again just after Christmas, may also help to decrease the levels of this tick in your horses. – Dr Mac (Contact Dr Mac c/o [email protected]).     |fw