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Tularemia



Excerpts have been reprinted with permission from the APHA’s Control of Communicable Diseases Manual (CCDM). Please refer to the CCDM for more complete information.

TULAREMIA ICD-9 021; ICD-10 A21
(Rabbit fever, Deer-fly fever, Ohara disease, Francis disease)


1. Identification – A zoonotic bacterial disease with diverse clinical manifestations related to route of introduction and virulence of the disease agent. The onset of disease is typically sudden and influenza-like, with high fever, chills, fatigue, general body aches, headache, and nausea. Most often it presents as an indolent skin ulcer at the site of introduction of the organism, together with swelling of the regional lymph nodes (ulceroglan­dular type). There may be no apparent primary ulcer, but one or more enlarged and painful lymph nodes that may suppurate (glandular type). Ingestion of organisms in contaminated food or water may produce a painful pharyngitis (with or without ulceration), abdominal pain, diarrhea and vomiting (oropharyngeal type). Inhalation of infectious material may be followed by respiratory involvement or a primary septicemic syndrome; bloodborne organisms may localize in the lung and pleural spaces. The conjunctival sac is a rare route of introduction that results in a clinical disease of painful purulent conjunctivitis with regional lymphadenitis (oculoglandular type). Pneumonia may complicate all clinical types and requires prompt identification and specific treatment to prevent develop­ment of serious symptoms.
 
Two subspecies with differing pathogenicity cause human disease. Isolates of Francisella tularensis subsp. tularensis (Jellison type A) are highly virulent, with a case-fatality rate of 5%-15% primarily due to untreated respiratory forms. With appropriate antibiotherapy, the case­fatality rate is low. Isolates of F. tularensis subsp. holarctica (Jellison type B) are less virulent and, even without treatment, produce few fatalities … 

Diagnosis is most commonly clinical and confirmed by a titer rise in specific serum antibodies that usually appear during the second week of the disease … Examination of ulcer exudate, lymph node aspirates and other clinical specimens by FA test or identification of bacterial DNA by polymerase chain reaction may provide rapid diagnosis. Diagnostic biopsy of acutely infected lymph nodes should be done only under the cover of specific antibiotherapy since it will often induce bacteraemia. The causative bacteria can be cultured on special media such as cysteine-glucose blood agar supplemented with iron or through inocu­lation of laboratory animals with material from lesions, blood or sputum … Extreme care must be exercised to avoid laboratory transmission of highly infec­tious aerosolized organisms; culture identification is performed only in reference laboratories and most cases are diagnosed serologically.

2. Infectious agent – Francisella tularensis (formerly Pasteurella tularensis), a small, Gram-negative nonmotile coccobacillus. All isolates are serologically homogeneous but are differentiated epidemiologically and biochemically into F. tularensis subsp. tularensis (Jellison type A) … or F. tularensts subsp. holarctica (Jellison type B) …

3. Occurrence – Tularemia occurs throughout North America and in many parts of continental Europe, the former Soviet Union, China and Japan. In North America, most cases occur from May through August but cases are reported throughout the year. F. tularensis subsp. tularensis organisms, restricted to North America, are common in rabbits and are frequently transmitted by tick bite. F. tularensis subsp. holarctica strains commonly occur in mammals other than rabbits in North America; strains are found in voles, muskrats and water rats in Eurasia, and in rabbits in Japan.

4. Reservoir – Wild animals, especially rabbits, hares, voles, muskrats, beavers and some domestic animals; also various hard ticks …

5. Mode of transmission – Arthropod bites … inoculation of skin, conjunctival sac or oropharyngeal mucosa with contaminated water, blood or tissue while handling infected carcases … by handling or ingest­ing insufficiently cooked meat of infected animals; by drinking contaminated water; by inhalation of dust from contaminated soil, grain or hay; and from contaminated animal pelts and paws. Laboratory infections frequently present as respiratory tularaemia.

6. Incubation period – Related to size of inoculum; usually 3-5 days (range 1-14 days).

7. Period of communicability – No direct person-to-person transmis­sion. The infectious agent may be found in the blood of untreated patients during the first 2 weeks of disease and in lesions for a month or more. Flies can be infective for 14 days and ticks throughout their lifetime (about 2 years). Rabbit meat frozen at -15°C (5°F) has remained infective for over 3 years.

8. Susceptibility – All ages are susceptible, and long-term immunity follows recovery; reinfection is extremely rare and has been reported only in laboratory staff.

9. Methods of control­
A. Preventive measures:
1) Educate the public to avoid bites of ticks, flies and mosqui­toes and to avoid contact with untreated water where infection prevails among wild animals.
2) Use impervious gloves when skinning or handling animals … Cook the meat of wild rabbits and rodents thoroughly.
3) Prohibit interzonal shipment of infected animals or their carcases.
4) Live attenuated vaccines … used extensively in the former Soviet Union, and to a limited extent for occupational risk groups in some indus­trialized countries.
5) Wear facemasks, gowns and impervious gloves and use negative pressure microbiological cabinets when working with cultures of F. tularensis.

B. Control of patients, contacts and the immediate environment
1) Report to local health authority: In selected endemic areas …
2) Isolation: Drainage and secretion precautions for open le­sions.
3) Concurrent disinfection: Of discharges from ulcers, lymph nodes or conjunctival sacs.
4) Quarantine: Not applicable.
5) Immunization of contacts: Not indicated.
6) Investigation of contacts and source of infection
7) Specific treatment: Aminoglycosides (gentamicin or strepto­mycin) are the drugs of choice. Recent experience of treat­ment with ciprofloxacin has shown excellent efficacy. Tetra­cyclines, also effective, are associated with higher relapse rates …

C. Epidemic measures: Search for sources of infection related to arthropods, animal hosts, water, soil and crops …

D. Disaster implications: None.

E. International measures: None.

F. Measures in the case of deliberate use. Tularemia is consid­ered to be a potential agent for deliberate use, particularly if used as an aerosol threat. As is true of plague, cases acquired by inhalation present as primary pneumonia. Such cases require prompt identification and specific treatment to prevent a fatal outcome. All diagnosed cases and especially clusters of pneumo­nia due to F. tularensis must be reported immediately to the local security and health department for appropriate investiga­tion.