01/11/2019

BSAVA provides Q&A advice on tick-borne encephalitis

With tick-borne encephalitis confirmed for the first time in ticks in the UK earlier this week, the BSAVA has put together a Q&A to give vets an easy reference point to answer any questions from concerned clients.

BSAVA President Sue Paterson said: “Tick-borne encephalitis has been detected in small numbers of ticks in Thetford Forest in Norfolk and on the Hampshire-Dorset border1.  Understandably this is causing some alarm, especially amongst pet owners, and has received national media attention. By providing our members with easy access answers to the main questions they are likely to be asked by their clients we hope to allay concerns and help owners take precautionary and preventative measures.”

What is tick-borne encephalitis?

Tick-borne encephalitis (TBE) is an infectious viral disease of humans and animals caused by the tick-borne encephalitis virus (TBEV)2.

How is the disease spread?

In both humans and animals, the virus is usually transmitted via a bite from an infected tick3,4. There are three sub-types of TBEV: 1) the European which is transmitted by the Ixodes ricinus tick, 2) Siberian, and 3) Far-Eastern, both of which are transmitted by Ixodes persulcatus. I. ricinus is found in most of Europe, including the UK3. In the UK, ticks are usually most active during spring and early summer and during the autumn.

In humans, TBEV may also be transmitted by the consumption of unpasteurised milk or milk products from infected animals, though this is rare2.

How common is the disease?

The risk from TBEV to human health in the UK is considered to be very low in the general population; to date, only one case of TBE acquired in the UK has been reported in an individual who developed signs of disease after being bitten by a tick in the New Forest area1.

What are the clinical signs of disease in humans?

The development of clinical signs of disease in human patients is rare; approximately 67% of human TBEV infections are asymptomatic. In clinical cases of disease, patients often present with non-specific, flu-like symptoms including fever, fatigue and headache. In 25% of clinical cases, patients go on to develop symptoms such as encephalitis and meningitis2.

Can TBEV affect animals? What are the clinical signs of disease?

Knowledge of TBEV in animals is limited5. Dogs can become infected with TBEV, but they seem to be much more resistant to the disease than humans. In the event that they do develop the disease, clinical signs are almost identical to those seen in human cases6.

Can dogs/cats transmit the disease to humans?

Dogs and cats cannot directly transmit the disease to humans, but they can pick up ticks that could carry TBEV.  Additionally, walking dogs in areas in which ticks persist can present an important risk factor for humans to acquire TBEV and other diseases transmitted by ticks such as Lyme’s disease7.

How can I protect against my pet contracting TBEV?

Given that pets can pick up ticks that could carry TBEV and other arthropod-borne diseases, acaracides should be applied in-line with the manufacturer’s instructions. It should be remembered that frequent water exposure may reduce the efficacy of the treatment product.

Owners should be “tick aware” and check their pets for ticks regularly – for dogs, it is advised to check them after a walk. In particular, owners who travel abroad with their pets should thoroughly check their pets just before returning to the UK and again on the point of return. Clients should also be aware of the risk of importing disease to the UK if they rescue strays of unknown health status from abroad.

Visible ticks should be removed as soon as possible to avoid transmission of disease using a tick-removal tool8. Once removed, ticks can be sent to PHE’s Tick Surveillance Scheme (TSS) which aims to inform the assessment of the public health impact of ticks in the UK.

Further information relating to preventing tick bites and arthropod-borne diseases in humans is available via Public Health England and the NHS websites.

Further information on important vector-borne diseases affecting small animals can be found in the BSAVA library

For information on how to become a BSAVA member visit https://www.bsava.com/Membership/Member-categories

References

1Public Health England (2019) Tick-borne encephalitis virus detected in ticks in the UK. https://www.gov.uk/government/news/tick-borne-encephalitis-virus-detected-in-ticks-in-the-uk

 2 Public Health England (2019) Tick-borne encephalitis: Epidemiology, diagnosis and prevention. Crown Copyright: London.

3European Centre for Disease Prevention and Control (ECDC) (2019) Factsheet about tick-borne encephalitis (TBE). https://www.ecdc.europa.eu/en/tick-borne-encephalitis/facts/factsheet

4Lindquist, L., Vapalahti, O. (2008) Tick-borne encephalitis. Lancet, 371. 1861-71.

5Klaus, C., Ziegler, U., Kalthoff, D., Hoffmann, B., Beer, M. (2014) Tick-borne encephalitis virus (TBEV) – findings on cross reactivity and longevity of TBEV antibodies in animal sera. BMC Veterinary research, 10 (78).

6Pfeffer, M., Dobler, G. (2011) Tick-borne encephalitis virus in dogs – is this an issue? Parasites and Vectors. 4 (59).

7Rizzoli, A., Silaghi, C., Obiegala, A., Rudolf, I., Hubalek, Z., Foldvari, G., Plandard, O., Vayssier-Taussat, M., Bonnet, S., Spitalska, E., Kazimirova, M. (2014) Ixodes ricinus and Its Transmitted Pathogens in Urban and Peri-Urban Areas in Europe: New Hazards and Relevance for Public Health. Frontiers in Public Health. 2, 251.

8European Scientific Counsel Companion Animal Parasites (2019) Ticks. https://www.esccapuk.org.uk/page/Ticks/36/

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