Tularemia is also called Rabbit Fever because lagomorphs are a natural reservoir for Francisella tularemia. It is often a cause of outbreaks in Central US, especially in people who hike or people who work with wildlife.
This bacterium is spread to humans through the bite of a tick, or direct contact with infected animals. Often, a patient will come across a rabbit that looks ill or is dead, and the patient tries to help the animal, coming in contact with the wounds or acquiring ticks from the animal. It is extremely virulent and only 10 organisms are needed to cause infection.
Patients with tularemia will have a fever, headache, and painful ulcerations at the site of infection.
Diagnosing tularemia is most often clinical, because this organism is fastidious and difficult to culture. Serologic testing is not often helpful because it takes weeks for antibodies against Francisella tularensis to form. Once the diagnosis has been made, aminoglycosides are effective against the organism.
Pasteurella multocida is a normal oral flora agent of dogs and cats. Therefore, it’s most likely transmitted to humans through a bite or scratch from an animal. Pasteruella multocida is more often associated with cats than dogs. It can also be transmitted if an animal licks a small cut on the hand or face. Definitely avoid those sweet keke kisses.
Animal bites are most often polymicrobial. When a patient presents with an animal bite, copious irrigation of the wound is critical. Surgical consultation should be considered especially for wounds to the face or hands. The key here is that you should not close the wounds, because you might cause the formation of an intense abscess.
Since we’re talking about it, you should also ask if there’s a chance the animal had rabies, and if so start the rabies post-exposure prophalaxis treatment. You should also ask if their tetanus shot is up-to-date. Follow-up should be considered to verify that dissemination hasn’t occured.
If this infection spreads it can cause cellulitis, osteomyelitis, septic arthritis, or sepsis.
A 74-year-old male presented to the hospital with confusion for the last 5 hours. Vital signs reveal a temperature of 100.1F, a heart rate of 110 bpm, and a blood pressure of 80/50 mmHg. His partner was asked about any recent medical history and he mentioned about six days ago, he received a small bite from their new kitten. Physical examination revealed an erythematous, warm, area of skin with clear demarcation. His neck was supple and no ulcerations or lacerations were seen. What is the most likely organism?
A. Staphylococcus aureus
B. Clostridium perfrengens
C. Pasteurella multocida
D. Streptococcus pyogenes
First, diagnose the patient.
This patient is presenting with fever, hypotension, confusion, and tachycardia. Which might suggest meningoencephalitis, but the neck is supple, so that points away from that diagnosis. The finding of an inflammed reddened area is suggestive of cellulitis and the systemic symptoms suggest that this infection has disseminated and is causing: septic shock.
A. Staphylococcus aureus is the most common cause of cellulitis, but the history gives you a clue to the causative agent that points away from this choice.
B. Clostridium perfrengens is often associated with myonecrosis but not cellulitis, because it needs deeper tissues since it’s an obligate anaerobe.
C. Pasteurella multocida can cause cellulitis and is especially associated with bite and scratches from animals.
D. Streptococcus pyogenes is the second most common cause of cellulitis, but the history gives you a clue to the causative agent that points away from this choice.
Therefore,
A 58-year-old male presented to the emergency room with left groin pain, malaise, and shivering for the past 8 hours. Vital signs reveal a temperature of 102.2F, a blood pressure of 106/46 mmHg, a heart rate of 116 bpm, and an oxygen saturation of 99% on room air. He works as a park ranger and recently found two dead rabbits on hike of the area and moved them off the path. Physical examination of the left leg revealed a 12x6mm erythematous, weeping ulceration on the shin. Laboratory studies reveal leukocytosis, a high level of C-reactive protein, and a negative VDLR test. What is the most likely causative agent?
A. Treponema pallidum
B. Pseudomonas aeruginosa
C. Francisella tularensis
D. Bacillus anthracis
First, diagnose the patient.
This patient is presenting with fever, tachycardia, and a skin ulceration. Skin ulcerations can be caused by: Pseudomonas aeruginosa, Treponema pallidum, Francisella tularensis, Bacillus anthracis.
A. Treponema pallidum could cause the formation of skin ulcerations in the tertiary stage when it creates gummas all over the body. However, this patient tested negative with the VDLR test which is a screening test for syphillis.
B. Pseudomonas aeruginosa can cause ecthyma gangrenosum which presents as a punched out skin ulceration with a black eschar. There is not any description of a black eschar or necrosis in this patient.
C. Francisella tularensis is called Rabbit’s Fever and typically forms a skin ulceration in patients who were recently bitten by a tick, or came in direct contact with ulcers.
D. Bacillus anthracis also forms skin ulcerations after contact with infected animals. This ulceration typically has a black eschar, which was not described in our patient.
Therefore,
References:
https://microbewiki.kenyon.edu/index.php/Francisella_tularensis
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4489087/pdf/13104_2015_Article_1232.pdf
https://www.bcmj.org/articles/tularemia-british-columbia-case-report-and-review
https://www.dovepress.com/a-case-of-ulceroglandular-tularemia-presenting-with-lymphadenopathy-an-peer-reviewed-fulltext-article-IMCRJ
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1479797/
https://wwwnc.cdc.gov/travel/yellowbook/2020/posttravel-evaluation/skin-and-soft-tissue-infections
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