Of Rabbits and Men


Tularemia is known as a rabbit disease which is spread to those who handle them including hunters and cooks; however, at the recent Lyme Disease Association 17th Annual Conference on Lyme and Tick-Borne Diseases, Timothy Lepore, MD, FACS, surgeon at Nantucket Cottage Hospital, explained that it is also a disease of those who work with the land such as landscapers and farmers, as well as those who get bit by a tick. There are cases reported in every state but Hawaii, and many other wild and domestic animals can be infected. The highest rates of infection are in Arkansas.

Tularemia first appeared in the United States in Massachusetts in 1937 after importing 30,000 to 40,000 rabbits per year from Europe. Importing came to an end in 1947.

Francisella tularensis, a gram negative, aerobic, pleomorphic, highly persistent intracellular pathogen, spread via the lymphatic system can cause fever, chills, headache, myalgia, extreme fatigue, glandular (swollen glands), oropharyngeal (sore throat, nausea, vomiting and diarrhea, abdominal pain and intestinal ulcerations), conjunctivitis, pneumonic (dry cough, respiratory difficulty and chest pain), ulceroglandular (skin ulcer at infection site) and can be septic and lethal. Symptoms typically develop within three or four days of inoculation but can take up to 10 days.

Tests: Tests for Tularemia are not widely available but direct examination of biopsy specimens or secretions by fluorescent antibody or Gram or histochemical stains are often helpful. F. tularensis can also be demonstrated microscopically with fluorescent-labeled antibodies. Antibodies are not typically present in the first ten days after exposure. Patient samples should come from sputum or pharyngeal washings, as the organism is not present in large numbers in blood. Polymerase chain reaction (PCR) tests can also be utilized. It is imperative that lab personnel take strong precautions as it is quite easy to become infected.

Treatment: Antibiotic therapy with Gentamicin (5mg/kg/day, IM or IV) or streptomycin (1 gm twice daily, IM). The recommended treatment period is 10 days. In vitro susceptibility studies indicate that quinolones and fluoroquinolones are also effective against F. tularensis, thus providing an additional option for physicians. Tetracyclines and chloramphenicol can also be used, but a higher rate of relapse is associated with these agents, as they are bacteriostatic rather than bactericidal. Thus, it is recommended that treatment with these medications be extended to 2-3 weeks. If treatment is initiated quickly the mortality rate for tularemia is around 1-2%; however, one-third of untreated patients will die, usually from pneumonia, meningitis or peritonitis.

Transmission: Transmission can occur through the skin or mucous membranes when handling infected animals as well as through tick bite, contact with fluids from infected deer flies, mosquitoes or ticks, handling or eating undercooked rabbit, drinking contaminated water, inhaling dust from contaminated soil, and handling contaminated pelts or paws of animals. It can also be inhaled from infected hay, grain, or soil. Dr. Lepore had patients who contracted it from their pet dog who shook rain water on them after chewing on a dead rabbit, as well as from folks eating road kill, a person who held sick animals, and a gentleman who slept with his pet bunny.
Tularemia, in aerosol form, is considered a possible bioterrorist agent that if inhaled would cause severe respiratory illness. It was studied in Japan through 1945, the USA through the 60’s, and Russia is believed to have strains resistant to antibiotics and vaccines. An aerosol release in a high population would result in febrile illness in 3-5 days followed by pleuropneumonitis and systemic infection with illness persisting for weeks with relapses. The WHO estimates that an aerosol dispersal of 50 kg of F. tularensis over an area with 5 million people would result in 25,000 incapacitating casualties including 19,000 deaths.

In a mass casualty situation – treat with oral agents for 14 days using Doxycycline (adults 100mg by mouth twice a day, children under 45kg 2.2 mg/kg by mouth twice daily) or Ciprofloxacin (adults 500mg, by mouth twice a day, children 15mg/kg by mouth twice a day).

Those performing autopsies should avoid bone sawing or any procedure likely to cause aerosolization and exposed people should wash with soap and water. In environmental contaminations use a 10% bleach solution for spraying and cleaning using alcohol 10 minutes after using bleach. There have been no reports of human to human transmission.

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