Powassan is a genus of viruses from the family Flaviviridae. It has RNA (ribonucleic acid) as its genetic material. The West Nile virus, dengue virus, tick-borne encephalitis virus, yellow fever virus, and Zika virus, among others, are viruses in the same class as Powassan virus. The Powassan virus was initially discovered in Powassan, Ontario, Canada in 1958. It is not curable.
In North America, there exist two types of Powassan: lineage 1 and lineage 2. Lineage 2 is known also as the deer tick virus, and is carried by deer ticks. It may be possible to predict when the number of cases of the Powassan virus will increase, based on when ticks are active, noticeably during the summer months.
During the last few years, northeastern and upper Mid-West states have seen significant growth in the occurrence rate of tick-borne illness. How a tick-borne disease evolves and transitions geographically may not be a straightforward process. Complications arise with residential construction and development around old or regrown forest and brush. Ticks can potentially re-inhabit these areas.
Routes of Prevention
Over the years, a variety of methods have been used to control ticks, with different success rates. Prevention programs usually incorporate several components, including continuing education on prevention protocols for both the public and medical providers. There is a large focus on the adoption of prevention measures, including checking for ticks on the skin, how to remove them properly, bathing or showering, the application of tick repellents, the use of protective garments, and tumble-drying clothing in high heat after exposure to ticks.
Essentially, the best way to prevent Powassan involves lessening the extent to which one allows oneself to be exposed to ticks. Besides avoiding wooded areas, people should apply to exposed skin repellents that have at least 20% N,N-Diethyl-meta-toluamide (DEET); picaridin, which can be found in some sprays, liquids, or aerosols; or IR3535, a synthetic amino acid. For clothing, apply products that contain the insecticide permethrin – on garments, shoes, boots, and socks, as well as tenting and netting.
Because dogs and cats can carry ticks, it is important to check pets for ticks and remove them . Using an acaricide, a pesticide, may be an option. Pets may be sensitive to chemicals, so a discussion with a veterinarian is warranted before applying any chemicals . In addition, regarding grassy areas and yards around houses, it is recommended to discard old leaves, clear tall grass, remove brush, construct barriers between woods and lawns, and remove unused lawn furniture and rubbish from the yard so that they do not becoming tick breeding areas.
Although there is not a cure, some fundamental research on the Powassan virus has improved the scientific community’s understanding of the disease. For example, investigators have found that key to successful transmission is a series of multiple interactions that involve the immune response of a host and early tick-influenced changes in the immune system.
In addition, at the University of Texas, Galveston, Texas, researchers have focused on the saliva of ticks as an important factor in determining how the virus is transmitted. Certain pharmacologically active compounds in the saliva help transmit the virus through a bite in the skin. Essentially, saliva initiates the disease transmission process, with some molecules making the victim, or host, more receptive to the pathogen. This also may speed the progression of the disease.
Other scientists have found that the Powassan virus also may exist in patients infected with Lyme disease. Moreover, an extensive co-infection rate involving both illnesses could be an indicator of how Powassan may be more pervasive than previously thought. The potential for co-infection should be considered when examining a patient’s symptoms and their health outcomes.
Models in Peromyscus leucopus mice have determined that mice infected with a quantity of virus lethal to other strains of mice only experienced a limited infection and were able to initiate an antibody response to the condition. The mice did not develop any symptoms and were able to control the infection. The investigators think that anti-viral proteins, produced in the host, counteracted the infection, and warrant further study.
Reviewed by Catherine Shaffer, M.Sc.
- CDC, Powassan virus prevention, https://www.cdc.gov/powassan/prevention.html
- CDC, Ticks, https://www.cdc.gov/ticks/avoid/on_people.html
- CDC, Preventing ticks on your pets, https://www.cdc.gov/ticks/avoid/on_pets.html
- CDC, Preventing ticks in the yard, https://www.cdc.gov/ticks/avoid/in_the_yard.html
- CDC, Powassan virus, Frequently asked questions, https://www.cdc.gov/powassan/faqs.html
- Ohio.gov, Powassan virus disease, http://www.odh.ohio.gov/pdf/idcm/powa.pdf
- New Hampshire DHS, Powassan Virus Fact Sheet, www.townofboscawen.org/.../powassan_virus_-_fact_sheet.pdf
- Powassan virus (POWV) Infection in Animals and Humans: A Review, www.researchgate.net/.../260598186_Powassan_virus_POWV_Infection_in_Animals_and_Humans_A_Review
- Tick Saliva Enhances Powassan Virus Transmission to the Host, Influencing Its Dissemination and the Course of Disease, http://jvi.asm.org/content/89/15/7852.full
- Evidence of High Rate of Powassan Virus Co-infection in Lyme Disease Patients, academic.oup.com/.../Evidence-of-High-Rate-of-Powassan-Virus-Co
- Modeling Powassan virus infection in Peromyscus leucopus, a natural host, journals.plos.org/plosntds/article?id=10.1371/journal.pntd.0005346
- Immune Cell Targets of Infection at the Tick-Skin Interface during Powassan Virus Transmission, journals.plos.org/plosone/article?id=10.1371/journal.pone.0155889
- Modeling Powassan virus infection in Peromyscus leucopus, a natural host, www.semanticscholar.org/.../52627abdcb2623c075cac8f1763c364e23c22a9c