Tularemia, a rare infectious disease caused by the Francisella tularensis bacteria, is often referred to as rabbit fever or deer fly fever. The illness bears Tulare County’s name, which was the location of its 1911 discovery in ground squirrels in California. 

A highly contagious bacterium called Francisella tularensis can infect people via several different channels. 

Inhaling germs in the air, especially if they get aerosolized because of handling diseased animal corpses or from accidents in laboratories. 

Tularemia can manifest in multiple ways according to the mode of transmission, such as glandular tularemia causing enlarged lymph nodes or ulceroglandular tularemia. Severe and possibly lethal are the pneumonic and typhoidal types. 

The Northern Hemisphere, which includes areas of Asia, Europe, and North America in this region tularemia is most common.  

During the warmer months, usually from late spring to early fall, when outdoor activities increase, individuals are more likely to meet infected animals or insects. 

Due to possible contact to contaminated settings or animals carrying the disease. People who work in outdoor occupations such as farmers, hunters, landscapers, and outdoor enthusiasts are more likely to get tularemia.

Tularemia usually strikes humans from bug bites, contaminated food or drink, aerosolized bacterial inhalation, or contact with diseased animals. 

Francisella tularensis enters the body through the skin, mucosal membranes, respiratory system, or gastrointestinal tract and then invades host cells, including dendritic and macrophage cells. By preventing phagosome-lysosome fusion, it evades the host’s immune system and multiplies inside the host cells. 

The immune system of the host responds to tularemia through both innate and adaptive mechanisms. Macrophages are essential for the immune response’s inception because they absorb germs and give T cells antigens.

A tiny, aerobic, Gram-negative bacteria, Francisella tularensis is a member of the Francisellaceae family. It is extremely contagious to humans as well as several mammals and birds.  

Numerous virulence characteristics that Francisella tularensis possesses enable it to avoid host immune responses and remain harmful. The bacterium creates a capsule to protect itself from host immune cells’ phagocytosis.  

There are ways for Francisella tularensis to live and proliferate inside host cells, especially macrophages. It prevents lysosomal enzymes from destroying the phagosome by preventing its fusion with lysosomes.

To improve tularemia outcomes, it is imperative to identify the disease early and start adequate antibiotic therapy. Prolonged illness progression and a higher chance of complications can result from delayed diagnosis and treatment.  

Individuals who have underlying medical issues are more susceptible to consequences from severe tularemia. On the other hand, those without major comorbidities might do better.

Age Group:  

Children can contract tularemia through outdoor activities such as playing in areas where infected animals or insects are present.  

Adults of all ages can be affected by tularemia. Elderly individuals may be more susceptible to severe forms of tularemia and complications due to age-related changes. 

Associated Comorbidity or Activity:   

Individuals with chronic illnesses such as diabetes, chronic obstructive pulmonary disease (COPD), or cardiovascular disease may be at increased risk of complications from tularemia due to underlying health issues that may compromise their ability to fight off infections. 

Advanced age itself can be considered a comorbidity as aging is associated with changes in immune function and increased susceptibility to infections. 

Pregnant women may be more susceptible to infections due to changes in immune function during pregnancy. Tularemia can pose risks to both the mother and the developing fetus, and severe cases may result in adverse pregnancy outcomes such as preterm birth or fetal death. 

Acuity of Presentation:  

Tularemia can be acquired through various routes, including direct contact with infected animals, insect bites, ingestion of contaminated food or water, or inhalation of aerosolized bacteria. The route of transmission can affect the speed at which symptoms develop and the severity of the disease. 

Tularemia can present in several clinical forms, including ulceroglandular, glandular, oculoglandular, oropharyngeal, pneumonic, and typhoidal. 

• Skin Examination: Presence of skin ulcers, typically at the site of inoculation. For e.g., from insect bites or direct contact with infected animals.  
• Respiratory Examination: Respiratory symptoms such as cough, dyspnea, and chest pain may be present. Auscultation of the lungs may reveal abnormal breath sounds such as crackles or decreased breath sounds over affected areas. 
• General Examination: Patients with tularemia often present with fever, which may be low-grade or high-grade, depending on the severity of the infection. 
• Neurological Examination: In rare cases, tularemia can cause meningitis or meningoencephalitis, leading to neurological symptoms such as headache, photophobia, neck stiffness, and altered mental status. Neurological examination may reveal signs of meningeal irritation. 

• Supportive Care: Supportive care measures may include hydration, pain management, and treatment of complications such as pneumonia or meningitis. 
• Adjunctive Therapies: In addition to antibiotic therapy, adjunctive therapies such as corticosteroids or intravenous immunoglobulin (IVIG) may be considered in severe cases with complications such as sepsis or severe inflammation. 
• Monitoring and Follow-Up: Patients with tularemia should be closely monitored for clinical improvement, resolution of symptoms, and potential complications during and after antibiotic therapy. 

Infectious Disease

• Animal Control: Reduce contact with potentially infected animals, such as rabbits, rodents, and hares, by avoiding areas where these animals are known to be present. 
• Environmental Hygiene: Educate the public about the importance of practicing good hygiene, such as washing hands thoroughly with soap and water after outdoor activities and avoiding touching the face or mouth with contaminated hands. 
• Occupational Safety: Provide training and personal protective equipment (PPE) to individuals at high risk of occupational exposure to tularemia, such as hunters, wildlife workers, and laboratory personnel. 
• Surveillance and Monitoring: Establish surveillance programs to monitor tularemia prevalence in wildlife populations and identify areas of high risk for human exposure. 

Family Medicine

Infectious Disease

• Streptomycin: Streptomycin is considered the drug of choice for severe tularemia and cases with central nervous system involvement. The duration of streptomycin therapy typically ranges from 7 to 14 days, depending on the severity of the infection and clinical response. 

• Gentamicin: Gentamicin is an alternative to streptomycin for the treatment of tularemia, particularly in less severe cases. 
• Doxycycline: Doxycycline is effective for the treatment of mild to moderate tularemia and is often used as an alternative to streptomycin or gentamicin. The duration of doxycycline therapy is typically 10 to 14 days, depending on the clinical response. 

• Ciprofloxacin: Ciprofloxacin is another alternative antibiotic for the treatment of tularemia, particularly in cases where streptomycin or gentamicin cannot be used. 

Emergency Medicine

Infectious Disease

• Debridement: Surgical debridement may be necessary in cases of extensive tissue necrosis or gangrene associated with severe forms of tularemia. Debridement involves the removal of necrotic tissue to prevent further bacterial growth, enhance wound healing, and reduce the risk of secondary infections. 

• Lymph Node Biopsy: In cases of persistent or enlarging lymphadenopathy with suspicion of tularemia, lymph node biopsy may be performed to obtain tissue samples for histopathological examination and culture. Lymph node biopsy aids in confirming the diagnosis of tularemia and guiding appropriate treatment strategies. 

Infectious Disease

Internal Medicine

• Recognition and Diagnosis: The initial phase involves recognizing the signs and symptoms of tularemia and considering it in the differential diagnosis, especially in individuals with relevant exposure history.  
• Supportive Care: Supportive care measures may be necessary, particularly in cases of severe tularemia or complications. Supportive care aims to alleviate symptoms, maintain hydration, and address specific organ system involvement. 
• Monitoring and Follow-Up: The monitoring phase involves regular assessment of the patient’s clinical status, response to treatment, and resolution of symptoms.