Introduction

Tularaemia is an infectious disease caused by the highly virulent bacterium Francisella tularensis. It can be transmitted through insect bites, direct contact with infected animals, or the ingestion or inhalation of bacteria-laden dust or aerosols. Tularaemia can present in various forms, and symptoms can vary from fever and swollen lymph nodes to respiratory distress. Currently, no approved vaccine is available, so prevention focuses on limiting exposure to potential sources of infection.¹ This article discusses various preventive measures to reduce the risk of tularaemia infection.

Overview of tularaemia infection

Tularaemia, also known as “rabbit fever” or “deer fly fever,” is a zoonotic disease - meaning that it can affect both humans and animals. Its causative agent is Francisella tularensis, a gram-negative bacterium which is known for its high virulence (ability to spread). As few as 10 to 50 bacteria can cause disease in humans, making it one of the most infectious bacterial pathogens.²

Tularaemia is most prevalent in the Northern Hemisphere, with most cases being seen in North America, Europe, and Central Asia. Incidence is particularly high among children and men.²

Transmission

Tularaemia can be transmitted through various routes, including:²

• Insect bites: ticks and deer flies are common vectors; when infected, they can transmit the bacteria to humans or other animals in their bites
• Direct animal contact: handling infected animals (particularly rabbits, hares, and rodents) or other wildlife can lead to infection
• Ingestion: consuming contaminated animal products or game meat or drinking untreated water sources can transmit the bacteria
• Inhalation: breathing in aerosolised bacteria or contaminated dust can lead to a more pneumonic form of tularaemia

High-risk populations

At-risk populations includes:¹

• Veterinarians 
• Laboratory workers
• Farmers and agricultural workers
• Hunters and game processors
• Butchers and other people who handle meat

Symptoms and forms of tularaemia 

The incubation period for tularaemia in humans typically ranges from 3 to 5 days post-exposure. However, it can span anywhere between 1 and 14 days. The symptoms of tularaemia can vary depending on the transmission route and form of infection.² Known clinical presentations includes:¹

• Ulceroglandular disease: this is the most common form of tularaemia; it is associated with skin ulcers and swollen lymph nodes
• Glandular disease: similar to ulceroglandular disease, but without ulcers
• Oculoglandular disease: characterised by conjunctivitis and swollen lymph nodes in the ear region
• Oropharyngeal disease: associated with sore throat, mouth ulcers, and swollen cervical lymph nodes
• Respiratory disease: this is the most severe form of tularaemia. It causes pneumonia and difficulty breathing
• Typhoid tularaemia: this involves systemic symptoms, such as with fever and fatigue, without localised symptoms
• Gastrointestinal tract disease: this form presents with vomiting, abdominal pain, and diarrhoea

Diagnosis and treatment

Diagnosis

Diagnosis is based on patient history, bacterial cultures, serology, and molecular testing methods. These methods help detect the presence of the bacterium in blood, lymph nodes, or other samples. Various diagnostic approaches include:²

• Clinical evaluation: your doctors will take a thorough medical history. This may involve asking about any potential exposure to infected animals or recent travel to regions where tularaemia is endemic
• Serological testing: various serological methods are available for detecting antibodies against F. tularensis in your blood. The most commonly used test is the enzyme-linked immunosorbent assay (ELISA)
• Culture and isolation: this method includes culturing (growing) the causative organism (F. tularensis) from patient blood samples
• Molecular techniques: Polymerase chain reaction (PCR) assays provide rapid identification and diagnostic confirmation

Treatment

At the moment, treatment for tularaemia typically involves antibiotic therapy (with ciprofloxacin, gentamicin, streptomycin, or doxycycline) and supportive care, which includes symptom management.¹

Preventing tularaemia 

Currently, there is no approved vaccine for tularaemia, so prevention focuses on limiting exposure to Francisella tularensis. Preventive methods include:^1,2

Avoiding exposure to infected animals

Handling infected animals, particularly wildlife like rabbits, hares, and rodents, is one of the primary routes of tularaemia transmission. It is important to take precautions. These include:

• Avoiding direct contact with wild animals, as they can be carriers of tularaemia. If handling wildlife or animal carcasses is unavoidable, wear protective gloves
• Wear gloves while handling game meat, and ensure it is thoroughly cooked before consumption
• Veterinarians, farmers, and wildlife workers should follow proper safety protocols and infection control measures

Preventing insect bites

Ticks and deer flies are common vectors for F. tularensis. Preventive measures include:

• Wear long-sleeved clothing and pants. These help by providing a physical barrier against bites
• Use insect repellents containing DEET, picaridin, or permethrin. These are effective at repelling both ticks and deer flies
• DEET-based products can be applied to the skin, while permethrin is used on clothing
• Avoid going to the tick-infected areas; if you do, conduct regular tick checks

Reducing risks of inhalation

The inhalation route causes severe pneumonic tularaemia. As such, respiratory protection is particularly important in areas where tularaemia cases have been reported among farmers. Preventive measures include:

• Wearing a mask when working in dry, dusty environments
• Moistening soil before handling it to reduce dust
• Laboratories working with F. tularensis must follow strict biosafety protocols

Safe food and water consumption

Since F. tularensis can survive in water and soil for weeks to months, contaminated food or water sources can lead to infection. You should:

• Refrain from drinking directly from natural water sources, such as ponds, streams, or rivers, particularly in areas where tularaemia is endemic
• Wash fruits and vegetables thoroughly before consumption, particularly those grown in areas known to harbour tularaemia
• Ensure meat, especially game meat, is cooked to an internal temperature of 74 degrees Celsius

Awareness and public health education

Educating communities about tularaemia is an important method of preventing the infection. Educating about how the disease spreads, recognising early symptoms, and knowing when to seek medical care can help prevent further spread. Education methods include:

• Public health campaigns should educate communities about tularaemia transmission, symptoms, and preventive measures
• Utilising social media platforms to spread awareness and engage the community
• Enforcing the following of biosafety level 3 (BSL-3) precautions in laboratories handling F. tularensis

Maintaining personal hygiene 

​By adhering to the following personal hygiene practices for infection control, individuals can significantly reduce their risk of tularaemia infection:

• Wash hands frequently: use soap and water to wash hands thoroughly after outdoor activities
• Use hand sanitiser: use alcohol-based hand sanitisers if soap and water are unavailable
• Avoid touching your face: avoid touching your face with unwashed hands to prevent the transmission of pathogens
• Sanitise equipment: clean and disinfect all tools and equipment after each use
• Use clean drinking water: always opt for treated or bottled water when travelling or in areas where water contamination is a concern
• Shower and change clothes after outdoor activities: after spending time outdoors, shower and change into clean clothing to remove any potential ticks or contaminants

Summary

Tularaemia presents a significant challenge due to its virulence and ability to utilise different routes of transmission. The symptoms of tularaemia can vary depending on the route of transmission and form of infection. Known symptoms include lymphadenopathy, fever, ulcers, pneumonia, and in severe cases, respiratory distress. While ongoing research is focused on developing safe and effective vaccines, the best defence remains awareness and proactive prevention. Preventive measures include maintaining good personal hygiene, properly handling animals, and preventing insect bites. Also, it is important to collaborate with local health authorities to educate people about the disease and develop strategies to reduce its impact on the community, especially in endemic areas. Ongoing research continues to enhance the understanding of tularaemia and is also dedicated to developing a safe and effective vaccine against Francisella tularensis.