Tularemia.docx

Lecture: Tularemia Introduction   

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Is an uncommon potentially severe, bacterial zoonosis caused by Francisella tularensis Natural cycle of causative organism = maintaining of infection in wide diversity of animal host and in certain ticks Transmission to human occur by sev modes  Bites by infected ticks or other arthropods  Direct inoculation thru skin, mucous membrane  Handling contaminated or infected materials  Ingestion of contaminated food or water  Inhalation of contaminated aerosol or dust Agent of tularemia is widely distributed in temperate and subarctic region of North America and Eurasia

Etiology    

F. tularensis Small, facultative, intracellular, Gram negative coccobacillus The organism = lipid envelope and able to survive under favorable conditions for sev weeks in water, moist soils, and decaying animal carcasses F. tularensis strain is divided accord. to virulence testing, biochemical reaction and epidemiological features

Type A:  Restricted to north America  >virulent type  Same strain was found in Central Asia Type B  Found thru out Europe and N. America  Considered to be potential agent of bioterrism because it can be ? as an aerosol and could result in large number of ?? and because it requires special actions on medical and public health prepareness

Life cycle     

Widespread in nature Have been recovered from 100 sp of wild animals, 9 spp of domestic animals, numerous spp of birds and fish and >50 spp of arthropods Principle natural cycle of agent involve the maintenance of infection inside wild mammalian hosts  rodents, voles, mice, aquatic rodents (water rat) Certain spp of hard tick = are able to maintain infection fr 1 developmental stage to another Transmission among animal = accomplished:

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 By the bites of blood-feeding arthropod or  by direct exposure to contaminated materials in environment Human become infected:  when they introduce into arthropod-borne cycle and r bitten by ticks or by blood-feeding fleas or mosquitoes that had contaminated mouth part  By handling or ingesting infected animals tissue or fluids  By ingestion of contaminated water or food  By inhalation of infected aerosols and dust The agent is ly infectious Require only 10 to 15 organisms to cause infection in human

Geographical distribution  North America  Russia  Central Asia  Mongolia  Areas of near east and middle east Population affected  Tularemia= rural disease  Affect person of all ages and both sexes  Groups of highest risk:  Hunters and travelers  Butchers and animals skinners  Farmers  Person exposed with enzootic area, to bites of certain hard tick, mosquitoes Seasonality  Mosquito-borne transmission in rural, peaks in summer months  The principle of pathologic changes in localized disease occur in  Cutaneous site of inoculation  Regional LN draining the site  When dis = disseminated – liver, lung, skin, spleen, and LN  r most often involved  The primary skin lesion begins as papule sev days following inoculation  The papule rapidly progresses  vesicles that erodes and dev into ulcer which typically 2 to 3 cm  Base of the lesion = necrotic and frequently covers w thick dark scab  Affected LN show haem. necrosis and may suppurate  F. tularensis response to infection – have prominent component of cell-mediated immunopatho  The fundamental lesion – devlpmnt of granuloma

Life cycle of Francisella tularensis Deer flies

Mosquito

Lagomorphs (Rabbit)

Ticks

Voles

Ticks

Water / soil

Lagomorphs (Rabbit)  

Water / soil

Voles

Outbreak of tularemia – near Moscow (300cases) which occurs 3 y and 5y ago vector was mosquitoes during summer

Clinical forms of tularemia Primary forms of tularemia includes: 1. 2. 3. 4. 5. 6. 7.   

Ulcer-glandular tularemia (45-85%) Glandular tularemia (10-25%) Ocular-glandular (<5%) Typhoidal/septic tularemia (<5%) Oropharyngeal tularemia (<5%) Pneumonic tularemia (<5%) Abdominal form

incubation period 2 – 5days onset – sudden patient has  fever (38-40°C)  chills  headache  nausea

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myalgia weakness cough chest pain

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Types of fever in tularemia  permanent  remittent  intermittent  undular  atypical without treatment = non-specific symptoms persists for sev weeks sweat, chill, progress weakness  characterized the continous illness other forms(2° form)maybe complicated by bact spread lead to secondary sepsis, tularemic pneumonia, meningitis and other metastatic infection

Ulcer-glandular tularemia (Bubonic tularemia)  A local papule appears at the site of inoculation the time or shortly after the appearance of fever  can see several enlarges LN – near the site of bites  Enlarges LN – moderately painful (
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Cough w minimal sputum production Chest discomfort Dyspnea Tachypnea

Abdominal form  Mesenteric lymphadenitis  Pain in right epigastric  Nausea and vomiting  √ all symptoms of mesenteric lymphadenitis which includes : o Padalka’s symp o Scheternberg sympt o Mark-federick sympt  Other syndromes: o Hepatolienal o Intoxication

Diagnosis      

Clinical diagnosis – confirmed by cultural idolation of F. tularensis and diagnostic rises in serologic titer 1:160 or > = diagnostic for F. tularensis infection During tularemia = √ of enlarged LN (involved several groups) and lymphatic elements near the site of inoculation In normal condition, we can’t palpate this LN Allergic skin testusing Tularin = diagnostic if lesion is >5mm in diameter(positive result) In brucellosis using Brucolin = diagnostic if lesion is >5cm in diameter (positive result) =Bjurne test

Treatment 1.     2.    3. 4.     

Streptomycin – DOC Given to adults IM 0.5-1.0g q12h For 10 days Gentomycin Parenteral 3-5mg/kg 10 days Tetracycline /doxycycline Ciprofloxacin In standard dose For 10 days Combination therapy – genta +doxycycline Also need to use detox treatment Of LN is suppurative, pt needs to be refered to surgical dept for drainage