NCCID Disease Debriefs provide Canadian public health practitioners and clinicians with up-to-date reviews of essential information on prominent infectious diseases for Canadian public health practice. While not a formal literature review, information is gathered from key sources including the Public Health Agency of Canada (PHAC), the USA Centers for Disease Control and Prevention (CDC), the World Health Organization (WHO) and peer-reviewed literature.
This disease debrief was prepared by Banneet Brar. Questions, comments, and suggestions regarding this debrief are most welcome and can be sent to nccid@manitoba.ca.
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Questions Addressed in this debrief:
- What are important characteristics of Francisella tularensis?
- What is happening with current outbreaks of Francisella tularensis?
- What is the current risk for Canadians from Francisella tularensis?
- What measures should be taken for a suspected Francisella tularensis case or contact?
What are important characteristics of Francisella tularensis?
Characteristics
Francisella tularensis are gram negative non-motile coccobacillus that are non-sporing, aerobic, and require cystine for growth. There are two biovars of tularemia; Type A (highly virulent) mostly located in the U.S. , and Type B (milder) located in the northern hemisphere.
Cause
Tularemia is a bacterial disease that can infect animals and people. In North America, this disease is found in wild animals which include rodents, rabbits, muskrats and beavers. Humans can become infected by tick and deer fly bites, through skin contact with infected animals, drinking contaminated water, and inhaling contaminated aerosols or agricultural and landscaping dust. Rabbits, hares, and rodents are also susceptible which can result in numerous deaths during outbreaks. There has been no record of human-to-human transmission.
Signs and Symptoms
Symptoms of Tularemia vary depending on how the individual was infected resulting in a range of illness from mild to life-threatening. All forms of the disease (listed below) are accompanied by fever that can go up to 104 °F.
There are six main forms of Tularemia disease listed below with the main cause and common symptoms. Ulceroglandular and Glandular most commonly occur. Symptoms generally include fever, chills, headache, fatigue, chest discomfort, cough, sore throat, vomiting, diarrhea, and abdominal pain.
| Form of Disease | Cause | Signs and Symptoms |
|---|---|---|
| Ulceroglandular Most common form | occurs after a tick or deer fly bite or after handing of an infected animal | Skin ulcer appears where the bacteria entered the body. Swelling of regional lymph glands, usually in the armpit or groin usually present with formation of the ulcer |
| Glandular Common form | Generally acquired through the bite of an infected tick or deer fly or from handling sick or dead animals | Similar symptoms to ulceroglandular but without an ulcer |
| Oculoglandular | Occurs when the bacteria enter through the eye. This can occur when a person is butchering an infected animal and then touches their eyes | irritation and inflammation of the eye and swelling of lymph glands in front of the ear |
| Oropharyngeal | results from eating or drinking contaminated food or water | may include a sore throat, mouth ulcers, tonsillitis, and swelling of lymph glands in the neck, pharyngitis or tonsillitis |
| Pneumonic Most serious form | from breathing dusts or aerosols containing the organism. It can also occur when other forms of tularemia (e.g., ulceroglandular) are left untreated, allowing the bacteria to spread through the bloodstream to the lungs | cough, chest pain, and difficulty breathing |
| Typhoidal | Characterized by any combination of the general symptoms (without the localizing symptoms of the other syndromes) |
- Ulceroglandular
- Most common form.
- Usually occurs after a tick or deer fly bite or after handing of an infected animal.
- Skin ulcer appears where the bacteria entered the body. Swelling of regional lymph glands, usually in the armpit or groin usually present with formation of the ulcer.
- Glandular
- Common form
- Generally acquired through the bite of an infected tick or deer fly or from handling sick or dead animals.
- Similar symptoms to ulceroglandular but without an ulcer.
- Oculoglandular
- Occurs when the bacteria enter through the eye. This can occur when a person is butchering an infected animal and then touches their eyes.
- Symptoms include irritation and inflammation of the eye and swelling of lymph glands in front of the ear.
- Oropharyngeal
- This form results from eating or drinking contaminated food or water.
- Symptoms may include a sore throat, mouth ulcers, tonsillitis, and swelling of lymph glands in the neck.
- Pneumonic
- Most serious form.
- Results from breathing dusts or aerosols containing the organism. It can also occur when other forms of tularemia (e.g., ulceroglandular) are left untreated, allowing the bacteria to spread through the bloodstream to the lungs.
- Symptoms include cough, chest pain, and difficulty breathing.
- Typhoidal
- Characterized by any combination of the general symptoms (without the localizing symptoms of the other syndromes).
Severity and Complications
Tularemia can be difficult to diagnose as it is a rare disease so the symptoms can be mistaken for other illnesses. Hence, it is important to point out potential exposure to tick and deer fly or contact with sick or dead animals to one’s healthcare provider. Most patients completely recover. For Uroglandular Tularemia, fever lasts 3 – 6 weeks without treatment. Fatality rates for Type A strains are about 35%, and 5-15% for Type B. Individuals at higher risk of developing severe illnesses include the elderly, individuals with respiratory illness or individuals with compromised immune systems.
Epidemiology
General
Type B Tularemia is found throughout North America and continental Europe, Russia, China and Japan. This disease is present during all months of the year. However, there is higher prevalence in early winter (during rabbit hunting season) and the summer (when ticks and deerflies are abundant). Yearly, the number of cases show variation which may be due to temperature and precipitation. Climate change can affect rodent populations whereby an increase in infected rodents can lead to an increased number of cases. This disease can infect individuals of all ages however, males at all ages have a higher incidence rate. This can be attributed to their outdoor professional and leisure activities.
Incubation Period
Tularemia incubation period is dependent on the virulence of the infecting strain, size of inoculum (dose) and how it came into contact with the individual. Incubation can vary between 1-21 days, however, is usually between 3- 5 days. About 5 – 10 organisms are known to cause the disease through the respiratory route, and 106 – 108 organisms are known to cause the disease through ingestion.
Reservoir and Transmission
The reservoirs include over a hundred species of wild animals. These include rabbits, hares, muskrats, beavers, various hard ticks, deerfly, mosquito, and birds. A range of arthropods has been identified for transmission between mammalian hosts. Ticks are considered an important vector east of the Rocky Mountains in the U.S.
Transmission can occur from infected blood or tissue of infected animals, fluids of infected flies, ticks, bites of arthropods (deerfly, mosquito) and ticks coming into contact with the skin, or oropharyngeal mucosa. Transmission can also occur through ingestion of contaminated food/drinking water, and inhalation of contaminated dust. Transmission through animal bites is rare. Tularemia is not directly transmitted from person-to-person.
If an individual has not been treated, the infectious agent may be found in blood during the first 2 weeks of the disease and in lesions for a month. Flies are infective for 14 days, and ticks are infective throughout their lifetime (2 years).
Laboratory Diagnosis
Blood tests and cultures can confirm the diagnosis. Appropriate clinical specimens include swabs or scrapings of skin lesions, lymph node aspirates or biopsies, pharyngeal swabs, sputum specimens, or gastric aspirates. Laboratory confirmation of infection is also noted if there is a fourfold or greater increase in serum antibody titre to F. tularensis antigen, or F. tularensis nucleic acid can be detected through polymerase chain reaction (PCR) or a sequence-based analysis.
Prevention and Control
Prevention mostly includes taking personal protective measures.
When hiking, camping, or working outdoors, it is recommended to wear long pants, long sleeves, and long socks to keep ticks and deer flies off your skin, not drinking untreated surface water, and removing ticks promptly with fine-tipped tweezers. When landscaping, it is recommended to not mow over sick or dead animals. When hunting, trapping or skinning animals, it is recommended to use gloves when handling animals (especially rabbits, muskrats, prairie dogs, and other rodents), and to cook game meat thoroughly before eating.
Effective disinfectants include 1% sodium hypochlorite, 70% ethanol, and glutaraldehyde, formaldehyde.
Vaccination
A vaccine for tularemia is under review by the Food and Drug Administration however is not currently available.
Treatment
Successful treatment has been noted with the use of antibiotics. Streptomycin is the drug of choice based on experience and efficacy. Gentamicin is considered as an alternative because it has a lower success rate. Treatment with aminoglycosides is recommended for 10 days. Tetracyclines may be a suitable alternative to aminoglycosides for patients who are less severely ill.
What is happening with current outbreaks of Francisella tularensis?
Tularemia is a rare disease in Canada as there have only been a few reported cases. As per the Public Health Agency of Canada, 9 cases of tularemia were reported in 2013 and 10 cases in 2014.
Manitoba
4 cases were reported to Manitoba Health, Seniors and Active Living in 2013 and two cases were reported for each of 2014 and 2015. No human outbreaks were reported.
Ontario
There have been 0 cases reported in 2019, and a total of 6 conformed cases from 2005 to 2018.
British Columbia
There have been 16 cases of tularemia from 1991 to 2007.
The link below is a map of the U.S. of reported cases in 2018.
www.cdc.gov/tularemia/statistics/index.html
What is the current risk for Canadians from Francisella tularensis?
Tularemia is rare in Canada, however there is increased risk in the summer as there are increased numbers of ticks and deerflies. Individuals that hunt in the winter are also at greater risk. Hence, Canadians that have careers or spend a lot of time outdoors are at increased risk of infection so precautions must be taken during outdoor activities.
Travel Recommendations
It is safe to travel as individuals can take numerous precautions for prevention. This includes using insect repellent containing DEET on skin and clothing. Handling sick or dead animals with gloves. Cooking food thoroughly, and ensuring your water is from a safe source are all recommendations. It should be noted that if traveling to the United States, Tularemia is most prevalent in Arkansas, Kansas, Missouri, and Oklahoma (more than 15 cases per state in 2018).
What measures should be taken for a suspected Francisella tularensis case or contact?
Case and Contact Management
The PHAC and CDC have developed brief guidelines to help healthcare providers in the management of the person infected with Tularemia. This includes diagnosis and reporting, clinical signs and symptoms, control, prevention, testing vaccination and reporting. If an individual is experiencing the listed symptoms, they should contact a health care provider. Public health should be aware of the symptoms of Tularemia and Primary Care practitioners should be asking about sources of contact to ensure accurate testing.
Public Health Ontario has a General Requisition Test posted on their website.
Identifying and Reporting
Tularemia is a nationally notifiable disease and therefore all Tularemia cases should be reported to local public health authorities in a timely manner.
If an individual is experiencing symptoms and has been in contact with potential vectors, it is recommended by the PHAC to contact your physician and indicate potential exposure.
As per Public Health Ontario, test results are reported to the health care provider ordering the test. Positive results are reported to the Medical Officer of Health as required by the Health Protection and Promotion Act.
Infection Control and Prevention
There is no vaccination to treat Tularemia, so prevention and control heavily depends on personal protective measures to decrease exposure to infected rodents, ticks, and mosquitos. Prevention of direct contact with infected vectors is the best precaution.