More Ticked Off!
Spring and summer is tick season in the U.S. Numerous tick species and tickborne infections are already prevalent (for example, Ixodes scapularis, the vector of the bacteria that cause Lyme disease, anaplasmosis, and babesiosis). Americans didn’t need another tick to worry about. Nonetheless, the Asian longhorned tick (Haemaphysalis longicornis) is here. It is the first new invasive tick to be found in the U.S. in past 50 years. This tick was discovered in sheep at a farm in New Jersey in November 2017. (Retrospective studies suggest, however, that it has been in the U.S. since 2010.)
This tick parasitizes birds and mammals, spreading quickly in farm animals (cattle, sheep, pigs, and chickens) and wildlife (bear, deer, foxes, hares, ferrets, and rats). It has also been found on cats, dogs, and humans. In cattle, the longhorned tick can transmit an animal disease called theileriosis, which can cause substantial blood loss. But it is also a problem for dairy farmers because of decreased milk production and sheep farmers due to decreased wool quantity and quality.
The longhorned tick is native to temperate areas of East and Central Asia where it has been wreaking havoc in livestock for years. It has also spread to New Zealand where it has been especially devastating. Birds are thought to play a key role in carrying it to new areas. But, exactly where the longhorned tick (also called, cattle tick, bush tick, and Asian tick) immigrated from and how it got to the U.S. are unknown.
Attempts have been made to eradicate the tick in New Jersey; they’ve been unsuccessful. The tick has since been found in Virginia, West Virginia, North Carolina, Pennsylvania, Connecticut, Kentucky, Tennessee, New York, Arkansas, and Maryland. It will probably not remain confined to these areas, however. Entomological studies indicate that a wide range of North America has favorable conditions for this arachnid to thrive
Haemaphysalis longicornis belongs to the Ixodidae family of ticks. Ixodes scapularis (the blacklegged or deer tick) is a major vector of Borrelia burgdorferi (the cause of Lyme disease), Anaplasma phagocytophilum (the cause of anaplasmosis), Babesia microti (the cause of babesiosis), Powassan virus, and other pathogens. In comparison to this other family member, the longhorned tick for now is a minor player in terms of causing human suffering.
The first human recognized to have been bitten by a Haemaphysalis longicornis tick was reported in May 2019. The victim, who lives in Westchester County, New York didn’t become ill. Nonetheless, this tick is known to carry pathogens that can be lethal to humans and animals, such as, SFTS virus, which causes a potentially fatal hemorrhagic fever. Many other human pathogens also have been detected in the longhorned tick, including the bacteria that cause Lyme disease and ehrlichiosis, as well as viruses (Powassan virus, tick-borne encephalitis virus). So far, none of these has been described in the U.S. But, surveillance here is just gearing up. And it appears that it won’t be long before the Asian longhorned tick will be competing with Ixodes scapularis for America’s “Most Unwanted Tick” species.
Ticks, along with mosquitoes, the other main vector of human pathogens, are now having “a field day.” Why are ticks faring so well in recent years? The answer, in part, is climate change. Warming and increased rainfall extend the geographic area and breeding season of ticks and mosquitoes.
Until vaccines are developed, what can you do to prevent infections caused by the Asian longhorned tick? The Center for Disease Control and Prevention urges people to take tick precautions: first and foremost, use a repellent containing DEET, picardin, or Oil of Lemon Eucalyptus; wear long-sleeved shirts and long pants when in the woods; treat clothing and gear with products containing 0.5% permethrin; and check your body and clothing for ticks after coming indoors. (See https://www.cdc.gov – ticks, for more details.)