Factsheet on tularaemia (2024)

1. Name and nature of infecting organism

Francisella tularensis, a gram-negative intracellular bacterium (family Francisellaceae, order Thiotrichales, class Gammaproteobacteria), is the agent of tularaemia.

Francisella tularensis is largely distributed to the Northern hemisphere and is not normally found in the tropics or the southern hemisphere. There are currently four subspecies known: tularensis (Type A) (the most virulent and only occurring in North America), holarctica (Type B) (the most widespread), mediasiatica (present in central Asia), and novicida (the least virulent).

In Europe natural foci of tularaemia are situated in three large ecological areas: (a) boreal forest taiga; (b) temperate broadleaf and mixed forest; (c) temperate grassland and shrubland. For instance, a very typical habitat for F. tularensis is the floodplain forest-meadow ecosystem in central Europe where lagomorphs (hares, wild rabbits) and rodents are the principal vertebrate hosts, and the tick Dermacentor reticulatus is the principal enzootic vector and reservoir.

In Europe, the number of human cases is approximately 800 annually. Sweden and to a lesser extend Finland are the countries reporting the highest notification rate in the European Union/European Economic Area region. There are several European countries where tularaemia does not occur (Iceland, Ireland, United Kingdom).

2. Clinical features

The incubation period of tularaemia is usually 3–5 days but may range from 1-21 days depending on the mode of infection and the infective dose.

Tularemia is often a long and debilitating disease. Early signs of the disease are influenza-like (e.g. fever, fatigue, chills, headache). There are several clinical forms of the disease that are function of the entry route of the bacteria:

  1. oropharyngeal form with chronic pharyngitis, following ingestion of contaminated water or food;
  2. glandular and ulcero-glandular forms with local lymphadenopathy and for the latter skin inoculation ulcer; those forms follow the bacteria inoculation via arthropod vector with a primary ulcer at the infection site;
  3. oculo-glandular form with conjunctivitis and local lymphadenopathy, following conjunctival contamination;
  4. pneumonic form with lung infection following inhalation of the bacteria or systemic infection;
  5. typhoidal form with severe systemic symptoms; this form can be the result of any entry route of the bacteria.

3. Transmission

3.1 Reservoir

A range of wild and domestic animals such as hares or rodents may function as the reservoir for tularaemia, as well as ticks.

3.2 Transmission mode

There are fiveroutes of F. tularensis transmission to humans:

  1. ingestion of contaminated food or water;
  2. handling of infected wild or domestic animals;
  3. haematophagous arthropod bites (e.g. ticks, mosquitoes);
  4. aerosol from contaminated dust;
  5. accidental inoculation, ingestion or exposure to aerosol or infectious droplets in laboratory setting.

Francisella tularensis can survive for weeks in cold, moist environments including water, soil, hay, straw and decaying animal carcasses. Due to the ease of aerosolization and the very low infective dose of infection, F. tularensis has been classified as a potential biowarfare agent.

In Europe, ingestion of contaminated water from streams, ponds, lakes and rivers is the main mode of infection. Dermacentor reticulatus, Haemaphysalis concinna and Ixodes ricinus ticks are the tick species most commonly infected by F. tularensis in Europe and act as biological vectors. In Sweden and Finland, bites of infected mosquitoes, especially of the Aedes cinereus species, play a relevant role in the transmission of the bacteria. Some other blood‑sucking arthropods (e.g. deer flies) have occasionally been reported as possible mechanical carriers and vector of F. tularensis in certain wetland or floodplain habitats of northern and eastern Europe during intense epizootics. Human-to-human transmission by aerosol or via arthropods has not been documented.

3.3 Risk groups

People involved in hunting, wildlife management, hiking and camping should be aware of the different modes of transmission of the disease.

4. Prevention measures

Tularaemia is a typical zoonosis being non-transmissible from man to man.

Prevention measures consist in avoiding ingestion, breathing and inoculation of the bacteria. This includes: avoiding drinking untreated surface water; using insect repellent and clothes covering legs and arms to avoid tick and mosquito bites; avoiding contact with dead animals, using gloves when handling wild animals especially skinning of diseased hares, wild rabbits and rodents; not mowing over sick or dead animals, cooking thoroughly game meat before eating; handling biological samples potentially contaminated with F. tularensis in biosafety level-3 (BSL-3) laboratories.

There is currently no effective and safe vaccine available against F. tularensis.

5. Diagnosis

As the disease is relatively rare and the symptoms non-specific, tularemia can easily be misdiagnosed.

Laboratory confirmation of tularemia consists in detecting the bacteria in a biological sample or a specific antibody response. Cultivation of the bacterium is rarely used for the diagnosis as the bacteria are slow growing and require a BSL-3 laboratory. Molecular methods (i.e. PCR) are rapid and allow identification of the subspecies. Serological methods are routinely used for diagnosis and are considered highly specific despite cross-reactions with Brucella, Yersinia, Proteus, Legionella and Mycoplasma species may occur. They usually require two samples taken a minimum of two weeks apart. Early antibiotic treatment can sometimes suppress the production of antibodies and lead to a misdiagnosis.

6. Management and treatment

The antibiotics of choice are aminoglycosides, (i.e. streptomycin or gentamicin), fluoroquinolones (i.e. ciprofloxacin) and tetracyclines (i.e. doxycycline). Most patients under treatment will recover completely but some patients, particularly those infected with the subspecies holarctica, may require a long period of convalescence.

The case fatality rate for infection with the F. tularensis subspecies tularensis is 5–15% without antibiotic treatment, and decreases to 2% with appropriate antibiotic treatment. Fatal cases due to the other F. tularensis subspecies are rare.

7. Key areas of uncertainty

A better understanding of specific variables that affect the activity of natural foci of tularaemia in Europe is needed to improve the monitoring of this disease.

8. References

Desvars A, Furberg M, Hjertqvist M, Vidman L, Sjostedt A, Ryden P, et al. Epidemiology and ecology of tularemia in Sweden, 1984-2012. Emerg Infect Dis. 2015 Jan;21(1):32-9.

Dwibedi C, Birdsell D, Lärkeryd A, Myrtennäs K, Öhrman C, Nilsson E, et al. Long-range dispersal moved Francisella tularensis into Western Europe from the East. Microb Genom. 2016 Dec 12;2(12):e000100. doi: 10.1099/mgen.0.000100

Forminska K, Zasada AA, Rastawicki W, Smietanska K, Bander D, Wawrzynowicz-Syczewska M, et al. Increasing role of arthropod bites in tularaemia transmission in Poland - case reports and diagnostic methods. Ann Agric Environ Med. 2015;22(3):443-6.

Hestvik G, Warns-Petit E, Smith LA, Fox NJ, Uhlhorn H, Artois M, et al. The status of tularemia in Europe in a one-health context: a review. Epidemiol Infect. 2015 Jul;143(10):2137-60. doi: 10.1017/S0950268814002398

Hubalek Z, Rudolf I. Francisella tularensis prevalence and load in Dermacentor reticulatus ticks in an endemic area in Central Europe. Med Vet Entomol. 2017 Jun;31(2):234-9.

Maurin M, Gyuranecz M. Tularaemia: clinical aspects in Europe. Lancet Infect Dis. 2016 Jan;16(1):113-24.

Rossow H, Ollgren J, Klemets P, Pietarinen I, Saikku J, Pekkanen E, et al. Risk factors for pneumonic and ulceroglandular tularaemia in Finland: a population-based case-control study. Epidemiol Infect. 2014 Oct;142(10):2207-16.

WHO. World Health Organization Guidelines on Tularaemia. Geneva: WHO 2007.

Page last updated 15 Dec 2023

Factsheet on tularaemia (2024)

FAQs

Factsheet on tularaemia? ›

Tularemia is a disease of animals and humans caused by the bacterium Francisella tularensis. Rabbits, hares, and rodents are especially susceptible and often die in large numbers during outbreaks. lone star tick. Deer flies have been shown to transmit tularemia in the western United States.

What are the facts about tularemia? ›

Tularemia is a disease caused by the bacterium Francisella tularensis (F. tularensis) that can affect humans, domestic animals, and wildlife. Tularemia occurs naturally in the United States and is most often found in animals such as rabbits, hares, squirrels and other rodents.

How common is it to get tularemia? ›

Tularemia is a widespread disease in animals. About 200 human cases of tularemia are reported each year in the United States.

How long does a tick have to be on you to get tularemia? ›

Most ticks seldom attach quickly and rarely transmit tickborne disease until they have been attached for four or more hours. 5. If you let your pets outdoors, check them often for ticks. Infected ticks also can transmit some tickborne diseases to them.

Is tularemia contagious from person to person? ›

Tularemia is not known to be spread from person to person. People who have tularemia do not need to be isolated. People who have been exposed to the tularemia bacteria should be treated as soon as possible. The disease can be fatal if it is not treated with the right antibiotics.

What are the long term effects of tularemia? ›

Tularemia has the potential to affect various organ systems of the body including the central nervous system, heart, and liver resulting in inflammation of the membranes surrounding the brain and spinal cord (meningitis), inflammation of the lining of the heart (endocarditis), and inflammation of the liver (hepatitis).

What is the mortality rate for tularemia? ›

How likely is someone to die from tularemia? Untreated, tularemia has a mortality rate of 5 percent to 15 percent. Appropriate antibiotics can lower this rate to about 1 percent.

What are the first symptoms of tularemia? ›

Symptoms of typhoidal tularemia
  • High fever.
  • Chills.
  • Headache.
  • Loss of appetite.
  • Muscle aches.
  • Sore throat.
  • Abdominal (stomach) pain.
  • Diarrhea.

Can tularemia go away on its own? ›

There are no home remedies for tularemia. It is a relatively rare disease but can quickly become fatal (60% of individuals infected may die from it) if not treated with appropriate antimicrobials.

What states have tularemia? ›

Tularemia has been reported from all states except Hawaii but is most common in the south-central United States, the Pacific Northwest, and parts of Massachusetts, including Martha's Vineyard.

Can you tell how long a tick has been attached? ›

If the tick has a swollen or rounded body, and the color has changed from brick red to a gray or brown, is an indication that the tick has been feeding and may have been attached for more than 36 hours.

How do you treat tularemia first line? ›

Only aminoglycosides, tetracyclines and fluoroquinolones are considered in the first-line treatment of tularemia.

What is the most common clinical presentation of natural tularemia infection? ›

The following are common findings in the various clinical forms of tularemia:
  • Abrupt onset of fever and chills - These symptoms typically last for several days, remit for a brief interval, and then recur.
  • Pulse-temperature disassociation.
  • Headache.
  • Anorexia.
  • Malaise and fatigue or prostration.
  • Myalgias.
  • Cough.
  • Vomiting.
Jan 12, 2023

What are some interesting facts about tularemia? ›

What is tularemia? - Tularemia, also known as “rabbit fever,” is a disease caused by the bacterium Francisella tularensis. Tularemia is typically found in animals, especially rodents, rabbits, and hares. Tularemia is usually a rural disease and has been reported in all parts of the United States except Hawaii.

What is the best way to prevent tularemia? ›

Steps to prevent tularemia include preventing tick and deer fly bites and avoiding contact with sick or dead animals.

What is the drug of choice for tularemia? ›

Streptomycin is considered the antimicrobial of choice in tularemia therapy. While chloramphenicol and tetracycline also are clinically useful against tularemia, relapse rates of up to 50% have been reported with these agents.

How long does tularemia survive? ›

Francisella tularensis can survive for weeks in cold, moist environments including water, soil, hay, straw and decaying animal carcasses.

Is tularemia killed by cooking? ›

Can I eat the meat? Normal cooking temperatures kill bacteria in the meat. Therefore, it is safe to eat. However, human exposure typically occurs while gutting a hare.

What is tularemia named after? ›

They named the pathogen Bacterium tularense after Tulare County, California, location of their study. In 1928, Edward Francis, a US Public Health Service bacteriologist, linked B. tularense with deer fly fever―tularemia transmitted by deer flies from infected wild rabbits to humans.

What does tularemia do to animals? ›

Clinical Findings of Tularemia in Animals

Sheep and cats may be subclinically infected or develop bacteremia, fever, and respiratory infection. Cats may also develop ulceroglandular or oropharyngeal disease, presumably through exposure to infected prey items.

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