Tularemia – ways of infection, symptoms, diagnosis, treatment. How to protect yourself from it?

Tularemia is a zoonosis, i.e. a disease that can be contracted as a result of contact with sick animals and m.in. their flesh and feces. In the case of tularemia, there are several ways of infection and several forms of the disease. The disease is most common in the northern hemisphere. in hunters and their families and people who are at risk of developing zoonoses due to, for example, their professional work (veterinarians, laboratory workers, foresters).

Rabbits and hares, as well as rodents, are particularly susceptible to infection with the Gram-negative bacillus Francisella tularensis. Sometimes tularemia is also diagnosed in cats. Gram-negative bacillus Francisella tularensis is one of the most pathogenic bacteria – only 10 bacilli are enough to cause disease. It is worth learning more about the course of tularemia and the risks associated with the infection.

Tularemia – the way bacteria enter the body

Gram-negative bacillus Francisella tularensis can enter the human body as a result of:

• direct contact with an infected animal,

• drinking contaminated water from natural water reservoirs,

• contact with contaminated soil

• consumption of raw or undercooked/undercooked meat from a sick animal.

Tularemia is also spread by ticks, red deer (so-called flying ticks) and other external parasites, e.g. mosquitoes and flies. The disease is also spread by inhalation, by inhalation of contaminated dust or aerosol containing pathogenic microorganisms. Most often, the Gram-negative bacillus Francisella tularensis enters the body through mucous membranes and damaged skin, e.g. as a result of an insect bite, a bite of a sick animal or contact of damaged epidermis with contaminated water or soil.

Tularemia is not often diagnosed in Poland. The disease is endemic in the north of the country. in the Pomeranian and Warmińsko-Mazurskie Voivodships. A greater risk of infection applies to people who are often in forests, hunt or have contact with biological material. About 10 cases of tularemia are diagnosed annually in Poland.

Symptoms of different forms of tularemia

There are several forms of the disease. Depending on the type of contact with the etiological agent. The clinical forms of tularemia are:

• Angina form – the development of the disease leads to the consumption of contaminated food or water. The first symptoms of this form of tularemia resemble the symptoms of tonsillitis – there are typical symptoms of pharyngitis and flu-like symptoms, e.g. high fever, muscle pain, joint pain, chills, general malaise. Inflammation can affect not only the mucous membrane of the throat, but also the entire oral cavity. Mouth ulcers are a characteristic symptom of angina tularemia.
• Nodal form – the most frequently diagnosed form of the disease. Infection occurs with as a result of being bitten by an infected insect. This form is dominated by symptoms that relate to the place of entry of pathogenic microorganisms into the body – an erythematous papule appears at the bite site, which over time transforms into an ulceration and then a festering wound. The sick person also has flu-like symptoms.
• Oculo-nodal form – infection occurs when harmful microorganisms come into contact with the conjunctiva. The symptom of the oculo-nodal form is conjunctivitis, accompanied by ulcerations and erythematous papules typical of tularemia.
• Visceral form – causes flu-like symptoms, as well as abdominal pain, nausea, vomiting and diarrhoea. A complication of this form of tularemia may be the development of pneumonia. In this case, we are dealing with a high risk of death due to infection – mortality in the case of visceral tularemia is about 50%.
• Gastrointestinal form Its course resembles food poisoning. Infection occurs by ingesting contaminated food or water. In addition to abdominal pain, vomiting and diarrhea, intestinal ulceration may occur;
• Pulmonary form – the development of this form of tularemia leads to the inhalation of dust in which there are disease-causing bacteria; their source is animal feces. In this form, the symptoms of pneumonia and dry cough predominate.

All clinical forms of tularemia are sudden-onset illnesses with high fever.

Diagnosis and treatment of tularemia

The diagnosis of tularemia is difficult. In order to diagnose the disease, it is necessary to perform blood tests and microbiological cultures. The patient is provided with swabs from skin lesions or sputum samples. Tularemia is treated with antibiotics.

How to protect yourself from tularemia?

To protect against tularemia, it is recommended to use repellents that protect against tick bites and other bloodsuckers, as well as wearing appropriate clothing. Clothing worn in the forest should have long legs and long sleeves. It is also worth remembering about the headgear.

You should not eat meat from an unknown source, and drink water from lakes, rivers and streams. Also, do not help injured animals without appropriate training and preparation, e.g. protect your hands with thick gloves – if you encounter an injured or sick looking wild animal, it is best not to touch it and notify the appropriate services.

Sources:

• Z. Dziubek, Infectious and parasitic diseases, Wydawnictwo Lekarskie PZWL, Warsaw, 2012

• Davidson, Internal Diseases, Volume 1, Edra Urban & Partner Publishing, 2021

• M. Tokarska-Rodak, Tularemia – infection caused by Francisella tularensis, Medycyna General i Nauki o Zdrowiu, 2015, Volume 21, No. 1, pp. 56–61