142. Tularaemia (Zoon.).

Question 1

Ethiology?

Answer 1

ETIOLOGY

• Mainly in rodents and wild rabbits (other species, human), but wide host range!
• 190 mammals, 23 birds, 3 amphibians, 88 invertebrates
• Vole, wild hamster, ground squirrel, European brown hare, squirrel, beaver, muskrat, deer
• Rabbit is not susceptible!
• Caused by Francisella tularensis, mainly in the northern hemisphere
• Subsp tularensis: north America, highly virulent
• Subsp. Holarctica: North America (beaver, muskrat), Eurasia (wild hare, small rodents)
• Subsp. Mediasiatica middle asia
• Subsp. Novicida: North America, Australia
• Morphology
• Gram negative coccoid rod (0.5 µm),
• Capsule: virulence factor, uniform (brucella, Yersinia)
• No flagella or spore, catalase positive (weak), oxidase negative
• Obl. aerobic, fastidious, 37°C, needs supplements: protein, cysteine/cystine, yeast extract
• Francis’s blood agar cysteine (0.1%), glucose (1%), rabbit serum (10%)/cysteine, glucose, eggyolk
• CO2 enhance the growth, incubation time 3-4 days
• Resistance is medium
• Carcass, wet soil, hide
• 3-4 weeks; drinking water 4-6°C
• 4 months; alive tick : 700 days
• 56°C: 10 minutes, sunshine (29°C): 3 hours
• Vectors: blood sucking arthropods , ticks (real vector), mosquitoes, biting flies

Question 2

Epidemiology?

Answer 2

EPIDEMIOLOGY

• Natural focal infections,
• size of the rodent population influence the number of human cases
• Shed with urine (Christmas tree workers, sugar beet washers ʹ risk of human infection)
• Acute septicemia or chronic disease ʹ inflammatory necrotic foci in the parenchymal organs

Question 3

Pathogenesis?

Answer 3

PATHOGENESIS

• Infection via P.O., skin lesion, blood sucking arthropods or inhalation
• Facultative intracellular bacterium : survive in macrophages and inhibit phagosome-lysosome fusion
• Site of infection, propagation in the regional lymph nodes
• gets into blood => septicemia parenchymal organs
• Long immunity after the disease

Question 4

Clinical signs?

Answer 4

CLINICAL SIGNS

• Virulence influences the clinical signs
• Ssp. Tularencis (acute disease ʹ clinical signs), ssp. Holarctica (asympt. or mild chronic infection)
• In endemic areas, infection of farm animals are frequent, but clinical cases are rare
• Clinical signs appear in sheep, horse and piglet; dog, cat, swine and cattle have seroconv. w/o clinical signs
• Fever anorexia in sheep and rodents, rodents also get general symptoms with fever and death
• Ruminants will have abortions, and the European brown hare weight loss and weakness

Question 5

Pathology?

Answer 5

PATHOLOGY

• Enlargement of spleen and lymph nodes,
• inflammatory and necrotic foci in parenchymal organs
• European brown hare: macroscopic lesions in lung (80%), pericardium (28%), kidney (20%)

Question 6

Diagnosis?

Answer 6

DIAGNOSIS

• Epidemiological situation, anamnesis, clinical signs and pathology
• Serology ʹ slide agglutination test, tube agglutination (over 1:40 titer: +), ELISA
• Bact. Examination: Isolation of the pathogen
• 37°C, 10% CO2 for 7 days
• Culture: animal trial, mouse inoculation, after 2-10 days it will die and isolate from heart blood
• Identification via serology, 16S rRNA gene, metabolic fingerprint
• IF, PCR
• Differential diagnosis:

1. Rodentiosis,
2. Brucellosis,
3. Toxoplasmosis

Question 7

Treatment and prevention?

Answer 7

TREATMENT AND PREVENTION

• Antibiotics : aminoglycosides (streptomycin, amikacin, gentamycin), tetracycline, chloramphenicol, imipenemcilastin, fluoroquinolones
• Serological examination of European brown hare before export,
• killing of seropositive hares,
• hunting of European brown hares
• Protection from ectoparasites (removal of ticks)
• Prevention of hunting of dogs and cats in endemic area
• No vaccine are available for animals

Question 8

Public health impact?

Answer 8

PUBLIC HEALTH IMPACT

• Zoonosis : 20-150 human cases in Hungary
• Occupational disease: hunters, trappers, vets, forest workers, sugar factory workers, laboratory workers
• Infection via rodents, European brown hare or arthropods
• Ulceroglandular form ʹ skin lesion or bite ʹ ulcer, enlargement of regional lymph node
• Oculoglandular form: conjunctivitis
• Oroglandular form : peroral ʹ vomiting, abdominal pain, diarrhea
• Septic, pulmonary form : aerogenic inhalation ʹ pneumonia
• Clinical signs: fever, headache and chills
• Prevention: inform compromised people, wear protective gloves, alive attenuated vaccine for humans