There's a new tick in town, or at least on your doorstep, if you live in Oklahoma, Louisiana or Texas, and entomologists are warning livestock producers and pet owners to be on the lookout for what may pose a serious health threat to humans and their animals.
Numerous types of ectoparasites, more commonly known as ticks who feed on mammals, birds and sometimes reptiles, have long posed a problem, especially to their human and animal hosts. In all, there are over 800 known species of ticks worldwide, about 90 of those can be found in North America, the most common being dog ticks, wood ticks and blacklegged, or deer ticks, the later of which are known to spread Lyme disease.
While external parasites are capable of carrying and spreading Lyme disease, there are a host of other pathogens they can spread, including anaplasmosis, babesiois, Powassan disease, Ehrlichia chaffeensis and Ehrlichia ewingii (which cause human ehrlichiosis), tularemia, and Rocky Mountain Spotted Fever, just to name a few. A pair of ticks that frequently migrate from Mexico and Central and South America are known carriers of Texas Cattle Fever.
But Dr. Denise Bonilla, an entomologist at the USDA-APHIS Veterinary Services Cattle Health Center in Fort Collins, Colorado, says a new tick species making its way across the United States could prove problematic because very little is known about the extent of the threat it poses. The tick has been tagged as a "longhorned" tick, the Haemaphysalis longicornis, and is believed to have originated in East Asia.
"We have confirmed this tick in eight states so far, beginning in 2010, with the first detection in New Jersey and followed quickly by another detection in Virginia, [but] it's possible it has been here longer than that. What makes it special is, it is a type of tick that is parthenogenetic, meaning reproduction does not require a male tick, so just one female tick can produce thousands of ticks. So if you don't pay attention to your animals the way you should, it is possible that a massive infestation can develop from a single tick," Bonilla warns.
She says even before one considers the vector of possible diseases the tick may carry, such large infestations alone can result in animals becoming anemic and develop problems associated with the condition. She says while the longhorned tick will attach to a human host, the greater concern is for livestock or even dogs and cats because eggs can drop off and hatch in bedding and tick populations can grow rapidly.
Bonilla says in addition to domestic animals, livestock and human hosts, researchers are seeing the tick in wildlife and even birds, another indication of the risk it poses in terms of spreading quickly to new locations. Though no confirmed cases of the tick in bird populations has been noted in North America yet, Bonilla says entomologists are aware the tick is capable of attaching itself to fowl.
"When you talk about disease transmissions by this tick, we really don't know what diseases it will vector in the United States. We are certainly interested. The Center for Disease Control (CDC) is doing a lot of viral and bacterial testing. We know that throughout the world it is capable of vectoring bacteria, viruses and protozoa. So you get a little bit of everything," she added.
The longhorned tick currently is not a known carrier of Lyme disease, but entomologists say it is an aggressive variety of tick and infestations can develop quickly. Similar to deer ticks, the nymph of the longhorn tick is very small, making it harder to spot and allowing it to go unnoticed on animals and people.
In July, the Arkansas Department of Agriculture confirmed that a longhorn tick was discovered and sent to the National Veterinary Services Laboratory for positive identification. That tick was discovered on a dog in Arkansas and was first transported to Oklahoma State University where it was examined and forwarded to the National Lab.
Bonilla says it is impossible to know where the tick may next be found but says it is reasonable to assume, based upon its aggressive behavior and ability to spread, it could move into neighboring states like Louisiana, Oklahoma and Texas.
The tick is considered an invasive species that congregates in large numbers. It is known to carry several diseases that infect hogs and cattle in Asia, but so far, ticks examined in the U.S. do not carry any infectious pathogens that were detected. Researchers warn that could quickly change.
"Early detection is important, which is true with any tick species. If you have livestock or domestic animals, or kids for that matter, it is advised to stay alert for possible infestations. We don't advise on human health, but for livestock, domestic animals and wildlife, it is wise to be alert and to report any problematic incidents to your county agent or extension specialists who can help identify the tick species and work with you in developing a treatment plan," Bonilla said.
Researchers say even experts have difficulty distinguishing among tick species, so it is important to take precautions to protect pets, livestock and family members from becoming a host for ticks of any kind, especially on the farm or ranch where ticks can multiply and spread rapidly.
The longhorned tick can transmit an animal disease called theileriosis to livestock. The disease can reduce milk production in dairy cows and cause blood loss in and the occasional death of calves. The parasite is highly adaptable to a broad range of climates, from tropical areas to colder northern states, where the tick has successfully overwintered.
Texas Animal Health Commission officials warn that unlike some other ticks, the longhorned tick requires three hosts to complete its life cycle. Potential hosts could include cattle, white-tailed deer, horses, goats, sheep, dogs, cats, opossum, birds and raccoons.
For more information on ticks and identification tools, visit http://tickapp.tamu.edu.