Red squirrel with tularemia (rabbit fever)

For the first time in the Netherlands, tularemia has been confirmed in a wild red squirrel (Sciurus vulgaris). The squirrel was found sick in early October 2023 in the municipality of Bunnik, province of Utrecht, and died shortly thereafter. The squirrel was collected by the DWHC for post-mortem investigation.

The squirrel was an adult male. He was thin and had inflammation in several organs. The suspicion that the inflammation was caused by the Francisella tularensis bacterium was confirmed by the VMDC (Veterinary Microbiological Diagnostic Centre) of Utrecht University and the WBVR (Wageningen Bioveterinary Research) in Lelystad. The disease caused by this bacterium is called tularemia.

Tularemia has been frequently found in hares (Lepus europaeus) close to this red squirrel’s location (see map 1, wild animals with tularemia in the central Netherlands). In the Netherlands, tularemia has also been confirmed in two beavers (Castor fiber), in addition to hares. The first positive beaver was in North Limburg in 2020. This disease had never previously been detected in a red squirrel in the Netherlands.

Tularemia is relatively common worldwide, and rodents and lagomorphs are particularly susceptible. This explains why the disease is also commonly called “rabbit fever.” Much has been written about tularemia in hares and small rodents in Europe, but very little about red squirrels. In 2021, the first case of tularemia acquired naturally by a red squirrel in Europe was described in Switzerland. This squirrel was an adult female that was trembling and lethargic and ultimately euthanized (Pisano et al. 2021). In 2022, a woman in Germany contracted tularemia after being bitten by a squirrel (Borgschulte et al. 2022). These are the only two known English-language scientific publications on naturally acquired tularemia infections in red squirrels in Europe.

Map 2 shows where tularemia was detected in wildlife in the Netherlands between 2011 and 2023.

Tularemia is a zoonosis, meaning that humans can contract the disease through contact with an infected animal. Humans can also become infected with rabbit fever through an insect or tick bite, by ingesting contaminated (surface) water or food, or by inhaling contaminated dust or air particles. Information about the symptoms in humans can be found on the RIVM website (Dutch).

Click here for more information and reports on tularemia.

Sources
Borgschulte, H. S., Jacob, D., Zeeh, J., Scholz, H. C., & Heuner, K. (2022). Ulceroglandular form of tularemia after squirrel bite: a case report. Journal of medical case reports, 16(1), 309. https://doi.org/10.1186/s13256-022-03510-8

Pisano, S. R. R., Kittl, S., Eulenberger, U., Jores, J., & Origgi, F. C. (2021). Natural Infection of a European Red Squirrel (Sciurus vulgaris) with Francisella tularensis subsp. Holarctica. Journal of wildlife diseases, 57(4), 970–973. https://doi.org/10.7589/JWD-D-20-00182