Since last November, eight states in the United States of America have become infected with the longhorned tick, a species that is native to Eastern Asia and has been established as an invasive species in Australia and New Zealand.
In Which States Have the Ticks Appeared?
The appearance of the longhorned ticks began in New Jersey last year when extreme numbers of ticks were discovered on a sheep on a farm in Hunterdon County. The species of tick was identified as Haemaphysalis longicornis by health investigators from the Monmouth County Tick-borne Diseases Lab, the Center for Vector Biology at Rutgers University, Walter Reed Biosystematics Unit at the Smithsonian Institution in Maryland, and the Hunterdon County Division of Health. The source of the ticks in New Jersey is still unknown, although there is some evidence to suggest that the longhorned ticks have been present in New Jersey since 2003. At the time, it was uncertain whether the large group of longhorned ticks was merely an isolated case, or whether the population had established itself in New Jersey. The infected field was treated with insecticide. When it was discovered that the population of the ticks had survived the winter by burrowing into the ground before the ground had frozen, the ticks were considered to have become established.
The longhorned ticks quickly spread from sheep to deer in New Jersey and have been identified on cattle in Virginia and West Virginia, on a dog in Arkansas, on animals in New York, on an opossum in North Carolina, on deer in Pennsylvania, and most recently, on deer in Maryland. Eight American states have now reported cases of the presence of the longhorned tick. As ticks have been known to host diseases that affect both humans and livestock, Americans have been warned to take necessary precautions.
What is The Longhorned Tick?
Ticks are a type of arachnid, like spiders. The longhorned tick (Haemaphysalis longicornis), also known as the bush tick or cattle tick, is a parasitic arachnid that is originally from Eastern Asia.
Longhorned Tick Appearance
As arachnids, ticks have eight legs with hooked ends. The body of a tick is oval in shape, and is a hard tick, meaning that it is difficult to crush due to a protective bit of armor found on the back of the tick. The longhorned tick is a solid red-brown color.
When empty of blood, the adult longhorned tick is three to four millimeters in length. However, when the adult longhorned tick has fed, it swells up and is the size of a pea, as can be seen in the picture below.
Longhorned Tick Lifecycle
The longhorned tick is able to reproduce both sexually, where a male tick fertilizes the eggs produced by a female tick, and asexually, in a process called parthenogenesis. In parthenogenesis, eggs develop into embryos without having been fertilized and are essentially clones of the mother tick.
Once the female tick has laid her eggs, she dies. The eggs hatch and the larvae emerge. The larvae are very small (approximately the size of a poppy seed) and have only six legs. The larvae transform into the next stage, called a nymph, which is larger and has eight legs like an adult. The stage after the nymph stage is the adult stage. At each stage of life, longhorned ticks consume blood. The sheep that had been infested with longhorned ticks in New Jersey was found covered in ticks ranging from larvae to adults.
Within two or three weeks, an adult female longhorned tick can lay up to two thousand eggs, all created asexually. While the longhorned ticks found in Eastern Asia tend to have both male and female ticks, the longhorned ticks found in North America so far seem to all be female. Therefore, it is likely that all of the longhorned ticks that have thus been discovered in the United States have been rapidly reproducing via parthenogenesis.
Habitat and Hosts of the Longhorned Tick
The longhorned tick is native to Eastern Asia, including China, Japan, and Korea. The tick is also found in Australia and New Zealand, and now has also invaded the United States of America.
Before becoming attached to a host, either human or animal, for feeding, a tick waits on a long blade of grass and “quests” by holding out its front legs and waiting for a host to brush past the tick’s legs. Once the tick attaches itself to its host, it begins to feed. The mouth region of the longhorned tick is shorter and wider than other tick species native to North America and houses the parts needed to allow the tick to attach to a host and feed on the host’s blood. The jaws, or chelicerae, of the tick, is the part that bites into the host like teeth, piercing the skin and giving access to the bloodstream. To attach to a host, the tick uses a structure called the hypostome, which is a hard barbed protrusion from the mouth that is inserted into the pierced skin of the host.
Longhorned ticks have been known to feed on mammals such as deer, and livestock including cattle. The ticks will also parasitize humans and pets like dogs and cats have also been hosts to longhorned ticks. Even birds have been found to have attached ticks.
What Are the Health-Risks Associated With the Ticks?
In infected animals, a first concern is the high number of ticks that can attach to and feed on the host. Having large numbers of ticks attached to the skin of an animal can cause stress to the animal or cripple it, and enough blood can be so rapidly removed and consumed as to cause anemia or even death via exsanguination. The next concern is the potential for ticks to carry and transmit diseases to host animals. Longhorned ticks have transmitted a bacterial disease called theileriosis to cattle which attacks red blood cells and causes anemia and death.
Ticks can also transmit diseases to human hosts. In China, longhorned ticks have been found to carry Severe Fever with Thrombocytopenia Syndrome Virus. The longhorned tick can transmit other viruses such as the Powassan virus, as well as bacterial infections such as anaplasmosis and ehrlichiosis. As of yet, the longhorned ticks found in the United States have not been found to be carrying any diseases.
Can the Ticks Be Avoided or Treated?
The best way to avoid being bitten by a tick is to avoid areas where ticks may be found, such as in long grasses. Protective clothing such as pants and long-sleeved shirts can be worn to reduce the chances of a tick bite, as can using insect repellents containing DEET. Check your clothing and skin for ticks, and check your pets too.
To remove a tick, use tweezers and grasp the tick as close to your skin as possible and pull the tick out without twisting. Wash the area of the tick bite well with soap and water and then apply an antiseptic. Keep the removed tick in rubbing alcohol for several months in case the tick must be identified.
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