An Asian Tick Arrives: Haemaphysalis longicornis in Nine U.S. States, 2017–2018

Haemaphysalis longicornis is a tick native to eastern Asia — eastern China, Japan, the Russian Far East and Korea — and has become established in Australia, New Zealand and several western Pacific island nations. Where it lives, it spreads disease:

• in China and Japan it carries the severe fever with thrombocytopenia syndrome virus (SFTSV), which causes a hemorrhagic fever in people, and Rickettsia japonica, the cause of Japanese spotted fever;
• ticks in Asia have carried species of Anaplasma, Babesia, Borrelia, Ehrlichia and Rickettsia — all groups that also circulate in animals in the United States;
• in parts of New Zealand and Australia it can cut dairy production by 25%.

It has a worrying trick: parthenogenesis. A single female can produce offspring without mating, so one introduced tick can lead to massive infestations. Before 2017 it had been intercepted at U.S. ports at least 15 times on imported animals and goods.

Found in the United States

In August 2017, H. longicornis was found on a sheep in New Jersey — the first detection in the U.S. outside quarantine. In spring 2018 it reappeared there, then in other New Jersey counties, seven more eastern states and Arkansas. The U.S. Department of Agriculture's Animal and Plant Health Inspection Service coordinated the response with agricultural and public health agencies at every level, and ticks were confirmed by morphology or DNA barcoding.

53 reports, August 2017–September 2018:

Ticks turned up in 45 counties — 8% of the 546 counties in those nine states. Archived specimens showed the tick had arrived years earlier: ticks from a deer in West Virginia in 2010 and a dog in New Jersey in 2013 were identified as H. longicornis in hindsight.

Counties reporting H. longicornis, August 2017–September 2018. Image from CDC's report

A new threat

So far there's no evidence it has passed any pathogen to people or animals in the U.S., and ticks weren't tested for pathogens in this survey. But it is a potential carrier of important agents here, including Rickettsia, Borrelia, Ehrlichia, Anaplasma, Theileria and viruses such as Heartland and Powassan. Heartland virus is similar to SFTSV, so the tick's possible role in spreading it deserves study.

What's needed

• Expanded surveillance of pets, livestock, wildlife and vegetation, using standard methods.
• Testing ticks for native and exotic viral, bacterial and protozoan pathogens.
• Research on its vector competence and vectorial capacity — feeding habits, host preferences, climate sensitivity and population density.
• Evaluating control methods, including insecticide and acaricide testing.

Many agencies are setting up hotlines, and some states are identifying ticks sent in by the public.

Limits: surveillance methods varied, so the findings show where the tick has been found, not its full extent — absence in a county may simply mean no one looked.

Sources

Based on C. Ben Beard, James Occi, Denise L. Bonilla and others, "Multistate Infestation with the Exotic Disease–Vector Tick Haemaphysalis longicornis — United States, August 2017–September 2018," MMWR, volume 67, Centers for Disease Control and Prevention; a work of the United States government in the public domain.