Introduction

Tularemia is caused by the bacterium Francisella tularensis (F. tularensis). It occurs from bug bites, contaminated water or food, and bacteria in the air, which should be treated as soon as possible. Fewer than 300 cases are reported per year in the USA.¹ In this article, we are going to explore the causes, symptoms, and severe complications that may arise due to tularemia. We are also going to have a look at treatment options and preventive measures. 

Epidemiology

Tularemia is an illness caused by Francisella tularensis (F. tularensis). In this situation, swelling of the lymph nodes occurs, and other symptoms in the lungs, throat, and intestines, depending on the location where the bacteria have infected.¹ 

It is also called " rabbit fever" or "deer fly fever " because it can spread from infected animals like rabbits, hares, or rodents. Tularemia is a zoonotic disease, which also means that it can be transmitted between animals and humans. There are four types of F.tularensis, among which type A causes the most severe disease. The mode of transmission of this infection occurs through insect bite or contact with contaminated animal products,  inhalation, ingestion, and contact with mucous membranes. Tularemia is commonly reported in children, with an increased rate of infection in adolescence and adulthood. 

Pathophysiology

The bacteria are capable of infecting a wide variety of immune and non-immune cells, leading to cell death. Even 10 or more organisms can lead to infection.² Granuloma formation is common in this situation and is often mistaken for Mycobacterium tuberculosis. The incubation period for this bacterium is 3-5 days (range 1-21 days).³ A few individuals do not show symptoms, and it can lead to an acute septic reaction, causing death.

Tularemia spreads in different ways: 

• Bites from ticks, mosquitoes, deer flies, etc
• Contact with infected animals from body fluids, which can penetrate your skin
• Drinking contaminated water or eating contaminated food
• Breathing in an aerosol that has the bacteria

Types of Tularemia 

Tularemia has various types based on where the bacteria have infected and the symptoms. 

Ulceroglandular Tularemia

It is a common form of tularemia resulting from bites by infected animals or ticks, and it is characterised by a skin ulcer at the site of infection and swollen lymph nodes.

GlandularTularemia

It is similar to ulceroglandular, but only results in swollen lymph nodes, not an ulcer.

Oculoglandular tularemia

When contaminated water or body fluids enter the eye, conjunctivitis results, along with swollen lymph nodes near the ear

Oropharyngeal tularemia

Results from eating contaminated food or water, or touching the mouth or nose without washing your hands, can cause sore throat, mouth ulcers, swollen lymph nodes, with digestive disorders.

Pneumonic tularemia

It is the most serious form of tularemia. It has symptoms similar to pneumonia, and you can get it in 2 ways   

1. Breathing in air contaminated by F.tularensis
2. F.tularensis spreading to your lungs 

Typhoidal tularemia

It causes high fever and affects many parts of the body. You can get typhoidal tularemia the same way as other forms of tularemia. 

Signs and symptoms 

Ulceroglandular and Glandular Tularemia 

• Fever and chills
• Swollen lymph nodes
• Skin ulcer  at the site of infection

Oculopharyngeal tularemia 

• Eye pain
• Tearing 
• Sensitivity to light
• Swollen lymph nodes
• Eye sore  

Oropharyngeal tularemia

• Fever
• Severe sore throat
• Swollen red throat 

Pneumonic tularemia 

• Fever
• Cough
• Dyspnea
• Chest pain
• Muscle aches
• Red bumps
• Coughing up blood 

Typhoidal tularemia

• High fever
• Chills
• Headache 
• Loss of appetite 
• Muscle aches
• Sore throat 
• Abdominal pain
• Diarrhoea
• Nausea or vomiting 
• Confusion 

Potential complications

Systemic complications

• Acute respiratory distress syndrome [ARDS] is a severe form of respiratory failure in which fluid builds up in small air sacs in your lungs. ARDS prevents your lungs from filling with air and causes low oxygen in the blood
• Organ failure - Tularemia has the potential to affect various organ systems of the body, including the central nervous system(CNS), heart, liver, and brain, causing organ failure requiring intensive care
• Blood infections (Septicemia)- If this bacterium enters the bloodstream, it can lead to organ damage, tissue damage, and even death. It can cause sepsis, which is the body's reaction to infection

Local complications

1. Bone infections 

Osteomyelitis ⁵ is a bone infection that happens when bacteria or fungi spread to your bone. It is a painful swelling in the bone marrow. It affects the bones, and kids are commonly affected. If not treated properly, it can cause permanent bone loss or necrosis.

2. Skin infections

 Tularemia might cause skin infections through a tick bite or handling of infectious matter. It might cause an ulcer or rash on the skin at the point of infection, or swelling and painful lymph nodes. These cases may be referred to as ulceroglandular tularemia.

Cardiovascular complications

1. Heart inflammation (Myocarditis)- F. Tularensis, which causes tularemia, can cause this infection and indirectly trigger heart inflammation by activating the immune system. Myocarditis is an inflammatory disease of the myocardium and usually gives rise to chest pain, dyspnea, palpitations, and fatigue³
2. Heart valve infections (Endocarditis)- often caused by bacterial infection in the lining and sometimes the heart chambers. Infection in the endocarditis causes growth on the valves, producing toxins and enzymes that kill and break down the tissue to cause holes in the valve⁴
3. Heart rhythm complications- Inflammation from tularemia may cause irregular heart rhythms, potentially linked to myocarditis

FAQs

Can tularemia cause pneumonia?

Yes, it can cause pneumonia if the infection spreads up to the lungs. It can cause chest pain, breathing difficulty, and breathlessness.

Can tularemia cause long-term health-related issues?

Sometimes, in cases with osteomyelitis and pneumonia symptoms, long-term treatment is needed. However, with proper treatment and care, people recover without the everlasting effects of the disease.

Does severe tularemia require hospitalisation?

Yes, severe tularemia often requires hospitalisation for antibiotics and supportive care, especially if the situation is like sepsis or meningitis.

How common are complications in severe tularemia cases?

Complications are more likely to occur in untreated or severe cases of tularemia. Prompt antibiotic treatment significantly reduces the risk. 

Real Life Case Scenario  

• A 57-year-old woman visited the doctor with a fever and a painful, swollen area near her right elbow for two weeks. She was treated for cellulitis, but returned after a few days because her symptoms weren't getting better. Tests showed swollen lymph nodes and a lesion under her skin, so she received stronger antibiotics. A week later, she came back with an ongoing fever and increased pain in her armpit. Doctors found more lesions and elevated white blood cell counts. She was initially treated with vancomycin and then doxycycline, which quickly improved her symptoms. Further tests showed signs of Ehrlichia, but other infections were ruled out. A biopsy revealed granulomas, and tests confirmed she had tularemia, a disease caused by Francisella tularensis. She had likely been exposed to this through wildlife in her yard. After being treated with doxycycline for 21 days, she recovered well⁶
• A 35-year-old man from rural Newfoundland and Labrador presented to the emergency department with fever, headache, sore throat, and a painful mass in his right armpit. Initially diagnosed with bacterial lymphadenitis, he was treated with clindamycin but returned two days later with worsening symptoms and nausea. He mentioned hunting moose and snowshoe hares a week earlier. After being prescribed amoxicillin-clavulanic acid, he returned the next day with chills and a high fever. Examination revealed a 6 cm tender mass and a small cut on his finger from cleaning a hare. Blood tests showed lymphopenia and elevated C-reactive protein. After transferring to a regional centre, he was treated with gentamicin for suspected tularemia. He improved rapidly and was discharged on doxycycline for three weeks. Follow-up serology confirmed tularemia, with antibodies rising in a month. His symptoms resolved, and the swelling disappeared⁷

Conclusion

Tularemia is a rare but potentially serious bacterial infection that can lead to severe complications if left untreated. Early diagnosis and prompt antibiotic treatment are crucial for preventing life-threatening conditions such as respiratory failure, sepsis, and organ damage. While tularemia can cause significant health issues, most individuals recover fully with appropriate care. 

Understanding the transmission methods, symptoms, and potential complications can aid in early intervention and reduce the risk of long-term consequences. Preventive measures, such as avoiding exposure to infected animals and using insect repellent, are key to minimising the risk of infection.