Tularemia (Rabbit Fever, Rodent Plague)
Tularemia is a frequently fatal infectious disease that occurs in an epidemic manner in Germany. It is caused by the bacterium Francisella tularensis. Field hares, wild rabbits, and other wild rodents are common carriers of the disease. Tularemia is a zoonosis, meaning it can be transmitted to humans.
Symptoms:
Tularemia is known for its epidemic spread and high mortality rate. Alongside Rabbit Hemorrhagic Disease (RHD) and RHD2, it is one of the rabbit diseases that often present without noticeable symptoms.
- In animals with mild forms of the disease, the most common signs are swollen lymph nodes, liver, and spleen, although this is usually not noticed by most owners.
- More noticeable symptoms include withdrawn behavior, significant weight loss, and in severe cases, emaciation, rough fur, and sometimes even a wobbly gait or skin abscesses.
- Especially in more severe cases, the animals appear lethargic and their overall condition is deteriorated. Diarrhea or difficulty breathing may also occur.
- Fever is often measurable (normal rabbit body temperature is 38.5 – 39 °C, but it can rise to 40 °C during periods of stress).
- Wild rabbits and hares may display a noticeable change in behavior, such as no longer fleeing when approached, making them appear unusually tame.
In the final stages, the animal typically succumbs to sepsis after 2 to 13 days, and about one-third of untreated animals will die.
Diagnosis and Laboratory Confirmation
The suspicion of tularemia is primarily based on contact with wildlife or known cases in the area.
- Ultrasound examination can be helpful in diagnosing tularemia.
- Blood tests may show slightly elevated liver values, and sometimes pseudonucleated cells (Pseudolinksverschiebungen) and leukocytosis (increased white blood cell count).
A definitive diagnosis can only be made through the detection of the pathogen:
- The pathogen can be cultured from affected tissues of the animal or human and identified through modern diagnostic methods (e.g., PCR).
Methods for pathogen detection:
- PCR (from EDTA blood, swabs, lymph nodes)
- Culture cultivation from blood, tissue samples (liver, spleen), or swabs (not always successful).
Attention: Any illness, as well as the detection of the pathogen causing tularemia in field hares and rabbits, is reportable.
Can Tularemia be Treated in Rabbits?
Since tularemia is a zoonotic disease (transmissible to humans), it is crucial to always consider the risk of transmission, especially if there are young children or immunocompromised individuals in the household. Furthermore, most owners recognize the disease too late for effective treatment. In such cases, euthanasia is generally recommended.
For mild forms or when the disease is detected early (e.g., in partner animals of deceased ones), treatment with antibiotics and infusions can be attempted in consultation with a veterinarian. Hygiene and human protection should always be the top priorities during this process!
Treatment Options:
The choice of antibiotic is crucial:
- Streptomycin is the most effective but must be injected into the muscle.
- Doxycycline and fluoroquinolones (e.g., enrofloxacin) are also effective and can be administered orally.
- Other tetracyclines are also effective.
- Chloramphenicol and ciprofloxacin can be given orally and are suitable alternatives.
- The pathogen is resistant to penicillin and sulfonamides.
Rabbits suspected of having been in contact with tularemia should receive a preventive two-week course of antibiotics.
How to Protect Yourself and Your Rabbits from Tularemia
Transmission Routes:
Human-to-human transmission is not known. The incubation period (the time from infection to the onset of symptoms) is typically two to five days (up to 14 days in some cases). The following transmission routes are possible:
- Transmission by blood-sucking animals (parasites such as ticks, fleas, lice, bedbugs, as well as mosquitoes and flies).
- Direct and indirect contact with infected wild rabbits, domestic rabbits, and rodents (especially certain professions such as hunters and veterinarians, e.g., during hunting, slaughtering, etc.). Infected wild animals are often “tame.”
- Contaminated environment: through mud or water contaminated by carcasses, green feed, or materials from nature (e.g., tree stumps, etc.).
- Inhalation of pathogen-laden dust (contaminated hay, straw, soil, dust, etc.).
- Consumption of undercooked, pathogen-containing meat (common among hunters).
- Laboratory infections through contact with pathogen-laden material.
Precautions in Areas with Tularemia
Unfortunately, there is currently no vaccine against the pathogen in Germany. However, vaccines for humans are available abroad.
- Hay and straw from tularemia-affected areas should not be fed to rabbits.
- A fly screen in windows (for indoor housing) or over the aviary wire of the enclosure (for outdoor housing) prevents flies and mosquitoes from coming near the rabbits. Fly screens are also available as roll goods to staple over the aviary wire.
- Consider using a spot-on insect repellent (especially for ticks).
- If tularemia is known in your district, be sure that no wild rabbits or hares come into contact with your rabbits or the areas they use. A double fence around the outdoor enclosure can help prevent this.
- When walking in risk areas, be cautious of dead field hares, rabbits, and rodents. If you come into contact with them, consult with your doctor to take preventive antibiotics. Dogs can also be carriers, so they should be kept on a leash in affected areas.
- The pathogen can survive in the environment at temperatures between 0–10°C for weeks, and even months at subzero temperatures.
Picking Grass in Areas Affected by Tularemia
While wild plants are not the primary carriers of tularemia, they can still become contaminated. Therefore, it is recommended not to feed green forage from forests and fields in areas affected by tularemia. Additionally, regional field-grown vegetables should be avoided if possible.
How far away from an outbreak can I pick?
Tularemia occurs in highly localized outbreaks, typically in isolated cases. Extra caution should be taken in the same district or neighboring areas (approximately a 10 km radius). Sometimes, only the district is known rather than a specific location, so it is helpful to monitor media reports, which often provide further details, or consult with the public health office for more information.
How to Safely Pick Grass in Tularemia-Affected Areas
It is safe to use green forage from your own garden or from areas that are known to be free of wild rabbits and hares (e.g., private green spaces, construction gaps). Leaves from trees are also safe, as they do not come into contact with infected animals.
In our case, in 2019, there was an outbreak in the district with several cases. During that time, we fed our rabbits with grass, but we made sure it came from nearby meadows, construction gaps, or private properties, while paying close attention to areas with wild rabbits and hares. We avoided remote meadows and forest edges.
How long after a known case should I be cautious?
Tularemia typically occurs in short outbreaks, so it is safe to start picking grass again once the outbreak is far enough in the past. As a general guideline, it is advisable to wait two to four months (depending on the distance from the outbreak) before resuming normal foraging.
Sources, including:
Bayerisches Landesamt für Gesundheit und Lebensmittelsicherheit: Tularämie (auch Hasenpest oder Nagerpest), [Stand: 25.10.2019, https://www.lgl.bayern.de/tiergesundheit/tierkrankheiten/bakterielle_pilzinfektionen/tularaemie/index.htm#khtie]
Esther van Praag, Ph.D.: Tularemia in rabbits. [Stand: 27.10.2019, http://www.medirabbit.com/EN/Skin_diseases/Bacterial/Tularemia.htm
Friedrich-Löffler-Institut: Nationales Referenzlabor für Tularämie, [Stand: 25.10.2019 ]
Liebscher, J., & Hein, J. (2021): Alles neu?!–Typische und untypische Infektionserreger beim Kaninchen. kleintier konkret, 24(S 01), 10-17.
Robert-Koch-Instituit (2021): Tularämie (Hasenpest, Francisella tularensis). https://www.rki.de/DE/Content/InfAZ/T/Tularaemie/Tularaemie_node.html [zuletzt abgerufen am 16.05.2021]
Robert-Koch-Instituit (2021): SurvStat@RKI. Abfrage der Meldedaten nach Infektionsschutzgesetz (IfSG) über das Web
https://www.rki.de/DE/Content/Infekt/SurvStat/survstat_node.html;jsessionid=4667EF22A3392A53FF11293851C14700.internet071 [zuletzt abgerufen am 13.05.2021]
