Vigilance is Key Regarding Asian Longhorn Tick

Teresa L. Steckler

In the recent past I wrote on the five main routes of transmission: direct contact; inhalation of aerosols; ingestion; indirect transfer by fomites (such as equipment, footwear or vehicles); or vector transmission. Vector transmission refers to living organisms spreading disease from an infected animal to another. Mosquitoes, ticks, biting midges and flies are common disease carrying vectors, but sometimes rodents or birds can serve as disease vectors.

As of late a new vector is gaining attention in the US – Asian longhorned tick (Haemaphysalis longicornis Neumann) also known as the longhorned tick, bush tick (Australia), and cattle tick (New Zealand).

The Asian longhorned tick (ALT) is native to Southeast Asia, including: China, Japan, Korea, Vietnam, Thailand. This species has established invasive populations in eastern Australia (southwestern Queensland, coastal New South Wales, and Victoria), New Zealand, and several Pacific Islands (New Caledonia, Fiji, Western Samoa, Tonga, and Vanutu)1. It can be a serious pest of livestock in these areas.

Although ALT is just now garnering attention, an Icelandic sheep died due to an infestation of this tick in Hunterdon County, New Jersey in August, 2017. Shortly thereafter, in early October, a large number of ALTs were found both on sheep and in paddocks in Hunterdon County, New Jersey2. Following this report, a search of archived tick specimens at the National Veterinary Services Laboratory found that Haemaphysalis longicornis was collected as early as 2010 in West Virginia. Unfortunately, the earlier specimens were misidentified. Another early specimen was confirmed from a 2013 collection in New Jersey.

ALT is relatively small in size as compared to native ticks, thus they are difficult to detect, especially given their small size and quick movement. ALTs are light brown in color and smaller than a sesame seed. In fact, the adult female is only about the size of a pea when it is full of blood. Males are rare.

Females can reproduce either sexually by mating with a male, or by producing offspring without mating (parthenogenetically). Only the asexual (parthenogenic) form has been identified in the United States. Regardless of the sexual form, adult female ticks may produce from about 900 to 3,300 eggs in a one-time event. Developmental time from egg to adult averages 89 days3. The feeding stages are active for 57 days. As a result of these biological adaptations, the parthenogenic form of this tick has the potential to reach exceptionally high densities in a few months with all offspring being female. It only takes a single tick to create a population in a new location.

This three-host tick has a wide host range, capable of feeding on different animals for each of the three life stages (larva, nymph and adult). Full engorgement may take from 3 to 6 days for each life stage depending on the host. Typically, the larva acquires a host (usually a small mammal), feeds fully and drops off the host to molt to the next life stage. This is also true for the nymph. Adults acquire a new host and, after feeding fully, it drops off the host to lay its eggs. Female ticks die after laying their eggs. If no other hosts are available, each life stage may feed on the same host, pastured cattle for example2. All three life stages may be found on host animals or in the environment.

In the United States, the tick has been found in or near counties with large horse, cattle, and sheep populations; see Figure 1. They have been found infesting a number of hosts including sheep, goats, dogs, cats, horses, cattle, white-tailed deer, Virginia opossums, raccoons, coyotes, red-tailed hawks, red foxes, grey foxes, striped skunks, eastern cottontail rabbits, elk, groundhogs, Canadian geese and humans. The four most common animals ALT has been found on within the US are dogs, white-tailed deer, raccoons and cattle.

Severe infestations of ALT in cattle can lead to death from the stress of excessive blood loss; as reported in Ohio and South Carolina. Production losses including decreased milk production and growth are substantial. ALT has also been recognized as a vector for multiple diseases of both humans and animals including viral, bacterial and protozoan agents.

ALT has been demonstrated to be the vector of several pathogens that cause disease in livestock, companion

animals, and humans in Asia, such as: • Babesia gibsoni - one of the pathogens that causes canine babesiosis, • Ehrlichia chaffeensis - a pathogen that causes human ehrlichiosis, with the white-tailed deer (Odocoileus virginianus Zimmermann) as the principal wildlife reservoir, and the lone star tick, Amblyomma americanum, as the primary vector in the southern, southcentral, and mid-Atlantic regions of the US4 and • Powassan virus – a pathogen that can infect human and other animals such as woodchucks and snowshoe hares in the US and Canada⁵.

In other countries, ALT is the primary vector of Theileria orientalis Ikeda genotype in cattle. The protozoan causes clinical signs similar to anaplasmosis — anemia, fever, lethargy, jaundice and death. The mortality rate for cattle infected with Theileria orientalis Ikeda genotype varies from 3 to 90 percent. Theileria oreintalis Ikeda genotype has been identified in Virginia and West Virginia. Research is continuing into the connection between the ALT and Theileria orientalis Ikeda genotype in the US.

Treatment and preventative measures for ALT are similar to those used currently for other ticks in the United States. Most modern tick-control products are effective against this tick. Producers should select products as directed by their veterinarian. Pasture management programs may be effective control measures. Controlled burning and mowing pasture boundaries adjacent to wooded areas may also be useful.

Preventative measures. Farmers should check their livestock for ticks regularly. If you spot any unusual looking ticks or large infestations, report to me or Dr. Holly Tuten (contact information is below). Figure 1 also shows the current knowledge of ALT’s presence in the US. If purchasing livestock in or near those areas, closely inspect the livestock, treat them for external parasites as recommended by your herd veterinarian, and quarantine the animals to ensure that you do not inadvertently introduce ALT.

Keeping grass and weeds trimmed and clearing away brush on feedlots and pastures are important tick prevention practices.

Removing a tick safely. Remove ticks immediately from people or animals (pets or livestock). Use fine-tipped tweezers if possible. If tweezers are not an option, shield your fingers with tissue paper, a foil-covered gum wrapper, or plastic sandwich bag. Grasp the tick as close to the skin as possible, pulling upward with steady, even pressure. Do not twist the tick as you remove it – this may cause the mouthparts to remain in the skin increasing the risk of infection. Do not use hot match heads, petroleum jelly or try to suffocate the tick during removal. After removing the tick, wash the affected area with soap and water. Then disinfect the bite with a topical antiseptic. Put the tick in a zip-top bag and seal it closed. Give the bagged tick to your veterinarian or doctor for examination.

Given the importance of this new invasive species, if suspected Asian longhorned ticks are found in Illinois, a sample should be sent to Dr. Holly C. Tuten, Vector Ecologist at the UI Medical Entomology Lab - Illinois Natural History Survey (contact htuten@illinois.edu for sample submission information) for accurate identification, and to allow proper tracking of this important tick.

States with confirmed local Asian longhorned tick populations with number of counties in each state. (# of confirmed counties / total # of counties)6

1. Heath AC, Occi JL, Robbins RG, Egizi A. 2011. Checklist of New Zealand ticks (Acari: Ixodidae, Argasidae). Zootaxa 2995: 55-63. 2. Rainey T, Occi JL, Robbins RG, Andrea E. 2018. Discovery of Haemaphysalis longicornis (Ixodida: Ixodidae) parasitizing a sheep in New Jersey, United States. Journal of Medical Entomology 55: 757-759. 3. Hoogstraal, H., Roberts, F.H., Kohls, G.M. and Tipton, V.J., 1968. Review of Haemaphysalis (Kaiseriana) longicornis Neumann (resurrected) of Australia, New Zealand, New Caledonia, Fiji, Japan, Korea, and northeastern China and USSR, and its parthenogenetic and bisexual populations (Ixodoidea, Ixodidae). The Journal of parasitology, pp.1197-1213. 4. Kocan AA, Levesque GC, Whitworth LC, Murphy GL, Ewing SA, Barker RW. 2000. Naturally occurring Ehrlichia chaffeensis infection in coyotes from Oklahoma. Emerging Infectious Diseases 6: 477-480. 5. Calisher CH. 1994. Medically important arboviruses of the United States and Canada. Clinical Microbiology Review 7: 89-116. 6. USDA: https://www.aphis.usda.gov/animal_health/animal_diseases/tick/downloads/longhorned-tick-sitrep.pdf