The Asian Longhorned Tick: Facts and Potential Problems

Ticks are small animals that survive by drinking blood. They are classified as ectoparasites because they live on animal or human skin. The Asian longhorned tick, or Haemaphysalis longicornis, is native to East Asia but has arrived in the U.S. It has been found in nine states in the eastern part of the country (at the time when this post was written). Ticks are of concern not only for the fact that they bite us and remove some of our blood. They can also transmit disease.

Ventral (lower surface) view of a female Asian longhorned tick
Photo credit: James Gathany and the CDC, public domain license

Facts About Haemaphysalis longicornis

Ticks aren’t insects. They belong to the class Arachnida, like spiders. The Asian longhorned tick is a member of the family Ixodidae within the class Arachnida. The animal is only three to four millimetres long when it hasn’t drunk blood lately. When it has fed recently, its body expands and is more noticeable. According to the University of Virginia, an adult filled with blood is about the size of a pea. The engorged animal has a very different appearance from the hungry one, as shown in the photo below. Before feeding on blood, the animal is red-brown in colour.

Like other ticks, H. longicornis often lives in areas with tall grass and a humid environment close to the ground. It can also be found in bushy or wooded areas. Some people have ticks in their backyard. The animals climb a blade of grass or a woody stem and perform a behaviour called questing to detect a passing host. A tick holds on to its support with its head facing downwards while questing. It then extends its front pair of legs outwards so that it can grab hold of an animal or a human that passes by. Various clues indicate that a potential host is present. Chemicals emitted by the animal, the body heat that's released, or vibrations caused by movement may tell a tick that a suitable host is near by.

Life Cycle

The tick has four stages in its life cycle. The larva, nymph, and adult all feed on blood. The timing of each stage's appearance and the animal's lifespan may vary depending on locality and environmental conditions.

• The egg hatches to produce a larva. Unlike the adult, the larva has only six legs. It’s also very small and will likely be unnoticed by many people. It may become inactive during winter.
• When the weather warms, the larva becomes active. It feeds on blood and then molts, forming a nymph. The nymph has eight legs, like the adult. Like the larva, however, it may become inactive in winter.
• When the environmental conditions are suitable, the larva feeds on blood and then molts to become an adult. The adult female must drink blood in order to produce her eggs, which number in the hundreds. Once she’s done this, she dies.

Interestingly, the tick is believed to be parthenogenic in the U.S. Parthenogenesis is a process in which a female produces young without being fertilized by a male. In Asia, the tick reproduces as we would expect, with both males and females in the population. In the United States, all of the ticks are thought to be females.

An engorged female
Photo credit: Commonsource, CC BY 3.0 License

Possible Problems Caused by a Tick Bite

The Asian longhorned tick was introduced into the United States in 2017 (or perhaps earlier) and is spreading. At the moment, it hasn’t been linked to health problems in the country. Some researchers think that this is only a matter of time, however. In some countries, the species has made people very sick.

Other ticks in the U.S. can cause some unpleasant and in some cases even life-threatening diseases, including Lyme disease, Rocky Mountain spotted fever, ehrlichiosis, anaplasmosis, Powassan virus disease, and other illnesses. In humans, the Asian longhorned tick has been associated with all of the diseases in this list. It has also been associated with a potentially very nasty condition called severe fever with thrombocytopenia syndrome. The tick seems to be more commonly known as a problem for cows, however. 

Ticks ingest bacteria or viruses as they suck blood from an infected animal. When they bite a new host, some of the pathogens may enter the host’s blood, multiply, and make them sick.

How to Reduce the Chance of Disease Caused by a Tick Bite

A common recommendation is to avoid areas where ticks may live or to stay in the centre of trail in these areas so that the body doesn’t brush against grass or branches. Health agencies often recommend that we cover our body with clothing. They say we should wear long-sleeved shirts, tuck shirts in, tuck the bottom of pant legs into shoes, and put tick repellent on our clothing and skin. The use of repellent needs to be investigated carefully. The benefits, risks, and precautions associated with the various types need to be explored. These considerations are important for our pets, too, since they can be infected by ticks.

People who have been travelling in tick country also need to inspect their skin and clothing carefully when they return from a walk. Taking a shower is said to be a good idea as well. The CDC reference given at the end of this post has an illustration showing the prime areas on the body where ticks may be found. The animals tend to home in on hidden areas, such as under the arms, behind the knees, and inside the navel.

Removing Ticks From the Skin

Removing ticks is important even though they may have attached to the skin early in a trip and weren’t discovered until much later. The CDC says that it may take as long as twenty-four hours after attachment for Lyme disease bacteria to transfer from the tick to the victim (This may not be true for all of the pathogens in ticks, however, including those in Asian longhorned ticks.) The sooner the ticks are removed, the lower the chance of contracting Lyme disease and perhaps some other diseases.

If a tick is discovered, it needs to be removed carefully so that the mouth parts don’t stay in the skin. The CDC and the Mayo Clinic recommend the use of fine-tipped tweezers. The tick should be grasped with the tweezers and then pulled steadily away from the skin in a straight line without jerking or twisting. Suitable tweezers should be part of a first aid kit taken on a journey through wild areas.

Should We Be Worried?

The spread of the longhorned tick is predicted to continue in the United States. The animal may enter southern Canada as well. Investigators are reminding the public that no pathogens have been found in the ticks that have been examined in the U.S. so far, however. They also say that even in countries where H. cornalis is relatively common, not all of the ticks carry pathogens. Still, they are monitoring the situation carefully. 

Longhorned ticks can infest cows in large numbers, causing serious blood loss. Their potential for carrying pathogens that can seriously harm humans is certainly a concern. Since North America already contains species of ticks that are known to do this, however, it’s a good idea to take precautions when necessary and to do some research about tick location if we decide to visit a new area.

References

The longhorned tick from Virginia State University

A new tick in the United States from the CDC (Centers for Disease Control and Prevention)

An Asian tick that can clone itself from CNN