Tularemia

Tularemia (rabbit fever, deer fly fever) is an acute natural focal infectious disease of rodents transmitted by ticks or flies. Main features are fever, lymphadenopathy, skin ulcers, conjunctivitis/ulcers, respiratory/digestive inflammation, and toxemia. F. tularensis can be used as a bioweapon; patients have high fever, generalized pain, swollen glands, and dysphagia. Antibiotics treat it easily.

Common Symptoms

Dull pain; diarrhea; septicemia; irritability; abdominal pain; fatigue; stupor; toxemia; local lymphadenopathy

Causes and Pathogenesis

Reservoirs are wild/ domestic rabbits (type A) and rodents (type B). Type A spreads mainly by ticks/blood-sucking insects; type B comes from surface water contaminated by rodents. Sheep, cats, and other animals may be infected. Humans are infected by contact with wild/sick animals; seasonal peaks relate to insect activity, though waterborne infections occur in autumn/winter. (1) Etiology: The pathogen is a Gram-negative coccobacillus 0.2-0.7 × 0.2 µm, non-motile, non-spore-forming, aerobic, growing well on glucose-cysteine-blood agar. It survives 3 months in tap/well water at 13-17°C, >5 months at 4°C, tolerates -30°C, survives 3 months in frozen meat and 1 month in cured meat; direct sunlight 30 min, 56°C/30 min, or 60°C/10-20 min sterilize. It is sensitive to disinfectants (0.1% mercuric chloride or 1% cresol in 30 s). Three geographical subtypes by glycerol fermentation and virulence: American (nearctica, glycerol-fermenting, most virulent), Palaearctic (palaearctica, usually non-fermenting, milder), and Central Asian (mediaasiatica, glycerol-fermenting but mild); Chinese strains (including northern Xinjiang) are Palaearctic. (2) Pathogenesis: After skin/mucosal entry, most patients develop a local ulcer; bacteria travel lymphatically to nodes causing inflammation and enlargement; some are phagocytosed, others enter blood causing bacteremia and dissemination to heart, liver, lungs, spleen, kidneys. Local ulcers extend deep with caseation, surrounded by polymorphonuclear leukocytes and epithelioid cells; bacteria are found within macrophages. Deep/superficial connected nodes show focal necrosis/suppuration without periadentitis. Pulmonary lesions show parenchymal consolidation with subpleural necrosis and abscesses; liver, spleen, adrenals may enlarge; granulomas occur in many organs, occasionally with central necrosis or suppuration.

Treatment

Drug therapy, symptomatic treatment, supportive therapy

Preventive Measures

1. Attenuated live vaccination gives up to 5 years' protection; oral or aerosol routes are possible. 2. Strengthen hunting quarantine and sanitation of contaminated environments. 3. Health education for occupationally exposed workers; manage water, food, meat, and pelts. 4. Prevent tick/insect bites and rodent infection. 5. In endemic areas, wear protective clothing, use repellents, and check for ticks; wear gloves/masks when handling rabbits/rodents; remove ticks immediately; cook wild birds/game thoroughly; disinfect possibly contaminated water.

Department to Visit

It is recommended to visit the Infectious Diseases department; an appointment can be booked on this platform before the visit.

Warm reminder: The above information is for health science reference only and cannot replace professional medical diagnosis. If you have related symptoms, please seek medical attention at a regular hospital promptly.