Veterinary Epidemiology and Zoonosis

Q-FEVER

Synonyms

• Q or Querry fever, Balkan influenza, Balkan grippe, Pneumorickettsiosis, Abattoir fever, Burnet’s Rickettsiosis, Australian Q fever, Nine mile fever, Coxiellosis, Queensland fever

Type of zoonosis

• Metarickettsial zoonosis

Definition

• Q fever is an infectious disease caused by the rickettsial pathogen, Coxiella burnetii, characterised by sudden onset of fever, malaise, headache, anorexia, weakness and interstitial pneumonia.

Brief history

• The febrile illness among the abattoir workers in Brisbane, Queensland in Australia was first noted by Edward Holbrook Derrick.
• In 1937, Q-fever was discovered by Frank Macfarlane Burnet and Mavis Freeman, and isolated the bacterium from one of the Derricks patients.
• Gorden Davis and Herald Rea Cox found the etiological agent of Q-fever.
• In 1938, Davis and Cox suggested that ticks, Ixodes ricinus involved in transmission of disease and named as Coxiella burnetii.
• An isolate from Dermacenter andersoni ticks collected from Nine Mile Creek, Montana, and named the strain "Nine Mile" and the disease, "Nine Mile fever"

Etiology

• Coxiella burnetii (Genus: Coxiella, Family: Rickettsiaceae, Order: Rickettsiaceae). It is a Gram negative, non-motile, rod shaped and obligate intracellular organism.
• Stains red with Macchiavello's stains and purple with Giemsa's stain.
• Antigenically, it is biphasic and does not produce agglutinin to react in Weil Felix test.
• It multiplies only in living cells and completes its life cycle within the phagosomes of infected cells.
• It is very resistant to the environment and drying. 
• It can be destroyed at 60°C and with phenolic disinfectants.
• Sodium hypochlorite, 1:100 lysol solution and formalin fumigation kill the pathogen.

Reservoir and incidence

• The two self perpetuating cycles involve: (1). Wild animals, with numerous tick hosts and (2). Domestic animals - sheep, goats and cattle.
• Dogs, cats and chickens are also susceptible.
• Domestic animals are the main reservoir of infection for humans.
• Coxiella burnetii can maintain itself in nature without involving invertebrate vectors.
• Q fever has been reported outbreak in Dehra Dun in 1940, involving Gurkha troops, and it was reported from Jammu and Kashmir, Punjab, Haryana, Delhi, Uttar Pradesh, Bihar, West Bengal, Orissa, Maharashtra, Madhya Pradesh, Karnataka and Tamil Nadu.

Transmission

• Sheep and goats are symptomless carriers.
• Organisms shed in urine, faeces, milk and especially birth products of carrier animals.
• Aerosol transmission is the major mode of transmission.
• Contact with infected tissues such as placenta of the infected ewe (contains 10⁹ organisms per gram of tissue), amniotic and foetal tissues.
• Ingestion of contaminated raw milk.
• Spread through bite of a tick, Ixodes ricinus.
• Human to human transmission is rare.
• One organism is considered to be enough to cause infection in humans.

Diseases in animals

• It is usually a subclinical infection in animals.
• Organisms multiply in genital tract, mammary gland of cow, sheep and goat, and produce abortion, bronchopneumonia, hepatitis and meningitis.

Disease in man

• Acute form
  • Incubation period is 2 to 4 weeks.
  • Symptoms include, prolonged fever (39-40°C), severe frontal headache with retro-orbital pain, profuse sweating, myalgia, fatigue, weight loss and nausea, and clay-coloured stools.
  • Chest pain upon breathing.
  • Subacute endocarditis.
  • No skin eruption or rash, which distinguishes it from other Rickettsial species infections.
  • Pulmonary involvement is asymptomatic in many cases.
  • Most cases resolve in two weeks but may be protracted or relapsing in the elderly people.
  • Mortality rate is usually low (1%), except with endocarditis.
• Chronic form
  • Chronic endocarditis, particularly in persons with preexisting valvular diseases, cancer and chronic kidney failure.
  • Case fatality rate may be as high as 60%.

Diagnosis

• Paired sera is useful in the diagnosis.
• Smear stained with Gemsa's stain or Gimenez's stain or Macchiavello stain gives purple or pink or red rickettsia, respectively. 
• Negative result in the Weil-Felix test (a test specific for typhus and other rickettsial diseases).
• Abnormal liver function tests.
• A titer of 1:200 or more by CF or IFA with phase 1 antigen in Q-fever endocarditis.
• Isolation of the organism from febrile blood, sputum, urine, milk, placenta, amniotic fluid is rarely attempted due to zoonotic concerns.
• Molecular techniques like PCR

Treatment

• Most acute cases heal spontaneously.
• Tetracycline can be given. It suppresses the symptoms and reduces the period of clinical course, but does not always eradicate the infection.
• Doxycycline for 2 to 3 weeks can be given.
• Combination of tetracycline + trimethoprim sulfamethoxazole can be given.
• Prolonged treatment (for years) with antibiotic is required for Q-fever endocarditis, even valves replacement may also be needed.

Prevention and control

• Isolation of infected animals from humans.
• Restrictions on movement of animals.
• Quarantine of imported animals.
• Protective clothing, masks, gloves and shoe covers.
• Intensive medical surveillance and health education programmes for public.
• Use only pasteurized milk and milk products.
• Appropriate disposal of placenta, birth products foetal membranes and aborted foetuses.
• Vector control.
• Disinfection of contaminated materials.