Biodefense

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Biodefense Epidemiology of Q fever Shahid
Beheshti University of medical sciences April
2005 By Hatami H. MD. MPH
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• An acute (on occasion chronic) febrile illness
  that occurs worldwide.
• One of the important zoonoses

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Morbidity and Mortality

• Prevalence unknown
• Endemic areas
• 18-55 of sheep with antibodies
• 82 of dairy cattle
• Morbidity in sheep 5-50

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Q Fever as a Biological Weapon

• Accessibility
• Low infectious dose
• Stable in the environment
• Aerosol transmission
• WHO estimate
• 5 kg agent released on 5 million persons
• 125,000 ill - 150 deaths
• Could travel downwind for over 20 km

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History

• 1935
• 1st described in Queensland, Australia
• Found in ticks in Montana
• Outbreaks
• Among military troops
• When present in areas
  with infected animals
• Cities and towns
• Downwind from farms
• By roads traveled by animals

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2 Etiologic agent

• Coxiella burnetii
• Rickettsial agent
• Obligate intracellular parasite
• Stable and resistant
• Killed by pasteurization
• Two antigenic phases
• Phase 1 virulent
• Phase 2 less pathogenic

• One organism may cause disease

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?????(Predisposing factors) 7 ?????? ?
??????(Susceptibility Resistance) 8 ?????
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period of communicability)
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1 - Incubation Period

• Incubation 2-5 weeks
• Depends on the size of the infecting dose

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2 - Natural course

• Asymptomatic (50)
• Acute
• Chronic

In contrast to other rickettsial infections, rash
rarely occurs in acute Q fever (ref mandell)
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Acute Infection

• Flu-like, self limiting
• Atypical pneumonia (30-50)
• Non-productive cough, chest pain
• Acute respiratory distress possible
• Hepatitis
• Skin rash (rarely)
• Myocarditis, pericarditis, meningoencephalitis
• Death 1-2

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Differences between Q fever and other
rickettsiosis

• Rash rarely occurs in acute Q fever
• The rash in chronic Q fever (endocarditis) is
  that of palpable purpura due to an immune complex
  vasculitis.
• The aerosol route of infection
• The lack of cross-reacting antibodies to Proteus
  X strain (the Weil-Felix reaction).
• Ref mandell

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Chronic Disease

• 1-5 of those infected
• Prior heart disease, pregnant women,
  immunocompromised
• Endocarditis
• Other
• Osteomyelitis
• Granulomatous hepatitis
• Cirrhosis
• 50 relapse rate after antibiotic therapy

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Risk to Pregnant Women

• Undergo reactivation during pregnancy in animals
  other than humans ??
• Most asymptomatic
• Transplacental transmission
• Reported complications
• In-utero death
• Premature birth
• Low birth weight
• Placentitis
• Thrombocytopenia

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Immunity

• Immunity following recovery from clinical illness
  is probably lifelong
• Cell mediated immunity lasting longer than
  humoral one

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Prognosis

• Overall case-fatality rate lt1 - 2.4
• 50 cases self-limiting
• Only 2 develop severe disease
• Active chronic disease
• Usually fatal if left untreated
• Fatality for endocarditis 35-55
• 50-60 need valve replacement

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3 - Geographical distribution

• Reported from all continents (at least 51
  countries)
• The incidence is greater than that reported
• Is endemic in areas where reservoir animals are
  present
• Ref control of communicable d.

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4 - Timeline trend

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• ????? ???? ?(Seasonality)

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Epidemics

• Epidemics have occurred among
• Workers in stockyards,
• Meat packing
• Rendering plants
• Laboratories
• Medical and veterinary centers that use sheep in
  research
• Ref control of communicable d.

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5 impact of age, gender, occupation And social
situation

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Occupation

• An occupational disease affecting those with
  direct contact with infected animals, such as
• Farmers, producers
• Veterinarians and technicians
• Meat processors, abattoir
• Laboratory workers

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6 predisposing factors

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7 Susceptibility and resistance

• Susceptibility is general
• Immunity following recovery
• Ref control of communicable d.

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8 Secondary attack rate

• Humans are dead-end hosts

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Reservoir

• Domestic animals
• Sheep, cattle, goats
• Dogs, cats
• Birds
• Ticks
• Reptiles
• Wildlife
• The most common animal reservoirs for this
  zoonosis are cattle, sheep, and goats

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Reservoir

• Ticks are natural reservoirs
• Transovarial transstadial are common in ticks
• Infected animals are usually asymptomatic but
  shed massive numbers of organisms in placental
  tissues at parturition
• shed in urine, feces, milk, and especially in
  birth products of reservoirs

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Transmission

• Aerosol
• Parturient fluids
• 109 bacteria per gram of placenta
• Urine, feces, milk
• Wind-borne
• Direct contact
• Fomites
• Ingestion
• Arthropods (ticks)

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Transmission

• Person-to-person (rare)
• Transplacental (congenital)
• Blood transfusions
• Bone marrow transplants
• Intradermal inoculation
• Possibly sexually transmitted

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Transmission

• Laboratory exposure
• Transport of infected sheep through hospitals to
  research laboratories
• Via blood transfusion.31
• Autopsy
• One report of apparent human-to-human transmission

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Period of communicability

• Direct transmission occurs rarely
• Contaminated clothing may be a source

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• Primary Prevention
• Prevention of disease in well individuals
• Secondary Prevention
• Identification and intervention in early stages
  of disease
• Tertiary Prevention
• Prevention of further deterioration, reduction in
  complications

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Prevention and Control

• Pasteurization
• Vaccination
• Human and animal
• Not available in U.S.
• Eradication not practical
• Too many reservoirs
• Constant exposure
• Stability of agent in environment

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Prevention and Control

• Education
• Sources of infection
• Good husbandry
• Disposal of birth products (incinerate)
• Lamb indoors in separate facilities
• Disinfection
• 0.05 chlorine
• 1100 Lysol
• Isolate new animals

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Diagnosis

• Serology (A fourfold rise in titer)
• IFA, CF, ELISA, microagglutination
• DNA detection methods PCR
• No cross-reactions have been reported between
  antibodies to other microorganisms and antibodies
  to C. burnetii
• Isolation of organism
• Risk to laboratory personnel
• Rarely done

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• WBC usually normal, but LFTs common
• Low mortality, but malaise may last months

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Treatment

• The treatment of choice for C. burnetii pneumonia
  is tetracycline
• Chloramphenicol has been used to treat Q fever
• The most effective agents are quinolones
  (difloxacin, ciprofloxacin, oxolinic acid) and
  rifampin.
• Chronic disease long course
• 2-3 years of medication

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Sources
1 Q fever, The center for food security and
public health Iowa state University, Internet
site. 2 -control of communicable diseases . . .