By Stan Deresinski, MD, FACP, FIDSA

Clinical Professor of Medicine, Stanford University

Dr. Deresinski reports no financial relationships relevant to this field of study.

SYNOPSIS: A tick that can transmit several infections has been newly identified in the United States.

SOURCE: Beard CB, Occi J, Bonilla DL, et al. Multistate infestation with the exotic disease-vector tick Haemaphysalis longicornis — United States, August 2017–September 2018. MMWR Morb Mortal Wkly Rep 2018;67:1310-1313.

In August 2017, a sheep in New Jersey was found to be infected with Haemaphysalis longicornis (see Figure 1), the first time that tick had been found in the United States. This raised concern because the tick is known to be the vector of several infectious diseases.

Figure 1: Longhorned Tick

Longhorned tick

Source: Centers for Disease Control and Prevention. What you need to know about Asian longhorned ticks A new tick in the United States. Available at: https://www.cdc.gov/ticks/longhorned-tick/index.html. Accessed Dec. 7, 2018.

Through September 2018, CDC has accumulated 53 reports of identification of this tick, variously known as the longhorned tick, the Asian tick, and the cattle tick, recovered from domestic animals, wildlife, and vegetation, as well as from two humans. The tick was detected from eight eastern states and from Arkansas. (See Figure 2.)

Figure 2: Counties and County Equivalents* Where Haemaphysalis longicornis Has Been Reported (N = 45) — United States, August 2017 - September 2018

Map

Source: Beard CB, Occi J, Bonilla DL, et al. Multistate infestation with the exotic disease-vector tick Haemaphysalis longicornis — United States, August 2017–September 2018. MMWR Morb Mortal Wkly Rep 2018;67:1310-1313.

Neither the ticks nor their hosts were screened for the presence of pathogens, but no cases of illness in hosts were reported. Examination of historical archived samples demonstrated that the tick had been present in the United States for years prior to August 2017, with, e.g., its identification in samples collected from a deer in West Virginia in 2010 and a dog in New Jersey in 2013.

COMMENTARY

H. longicornis is native to eastern China, the far east of Russia, Japan, and Korea, and it is also found, as the result of later introductions, in New Zealand, Australia, and some western Pacific island nations. In each of these places, it is an important vector of human and animal disease. The tick is known to transmit the agent of severe fever with thrombocytopenia syndrome (SFTV virus) and Japanese spotted fever (Rickettsia japonica). Pathogens identified in the tick include ones causing infections in the United States: Anaplasma, Borrelia, and Ehrlichia. The tick also may be a vector of Powassan and Heartland viruses, as well as Theileria, a parasite that infects ruminants. H. longicornis infestation of dairy cattle in Australia and New Zealand is associated with a marked reduction in milk production.

It is unlikely that H. longicornis is restricted to the nine states in which it has been found to date. It is very likely that the tick will prove to be a vector of one or more infectious diseases in the United States.

The CDC is working to define its epidemiology further and its potential for pathogen transmission to humans, cattle, and other animals.