June 05, 2010

Q Fever Infections in Humans

Q fever, also called rickettsial pneumonia or Balkan grippe, is an acute, self-limited, systemic disease caused by the rickettsia Coxiella burnetii. Q fever causes illness and sometimes abortion in animals, and it can lead to a pneumonia-like illness in humans. It spreads rapidly in cows, sheep, and goats, and in humans it tends to occur in localized outbreaks.

This article is for Medical Students & Professionals
This is a Question & Answer revision article designed for medical students and professionals preparing for the PLAB, MRCP or USMLE examinations. They are based on actual questions from these examinations. You may find the Pneumonia article more useful, or one of our many articles on Diseases & Conditions, Medical Syndromes, Health & Wellness or Home Remedies.
In this article:
What is Q fever
MCQ exam: clinical scenerio
MCQ exam: answer
MCQ exam: explanation

What is Q fever

Q fever is an infection with the bacteria Coxiella burnetii. It is usually, but not always, caught by direct contact with farm animals, especially sheep, cattle and goats. Most cases are sporadic. Outbreaks are unpredictable and are more likely to affect urban (ie non-immune) populations.

The clinical symptoms are those of fever, chills, severe headache, and pneumonia. The disease is usually mild, and complications are rare. Treatment with tetracycline or chloramphenicol shortens the duration of illness.

Q fever is mainly an occupational disease linked to rural employment. Prevention and control measures are most effective for occupational groups and environments. Restricting access to potentially infected animals and disposing animal birth products safely, for example, prevents infection spread. Those who should avoid contact with cattle, sheep, goats and cats while the animals are pregnant include:
  • pregnant women
  • people with suppressed immune systems
  • people with congenital or acquired heart valve disease, or vascular grafts

MCQ exam: clinical scenario

A 38 year old farmer is seen with severe headache and fever. He has a history of a ten day cough with bloody sputum and consolidation on a chest xray for which he was given erythromycin by his physician. Physical examination was unremarkable except for bilateral inspiratory crackles and a lumbar puncture was performed. This demonstrated a highly pleomorphic coccobacillii with gram-negative cell wall.

These features are characteristic of:
a) Streptococcus pneumoniae
b) Bacteroides fragilis
c) Coxiella burnetii
d) Escherichia coli
e) Haemophilus influenzae

MCQ questions & answers on medicalnotes.info

MCQ exam: answer

The correct answer is C.
The presented features are more characteristic of Coxiella burnetii infection than of the other options.

MCQ exam: explanation

Coxiella burnetii, the etiologic agent of Q fever, is a highly pleomorphic coccobacillus with a gram-negative cell wall. There are three presentations of Q fever:
  • atypical pneumonia,
  • rapidly progressive pneumonia, and
  • pneumonia as an incidental finding in a patient with a febrile illness.
This last presentation is probably the most common form of Q fever pneumonia.

In Q fever due to Coxiella burnetii the physical examination of the chest is often unremarkable. The most common physical finding is inspiratory crackles. Patients with rapidly progressive pneumonia usually have the physical signs of pulmonary consolidation. About 5% of patients have splenomegaly. Fever and severe headache suggest central nervous system infection, and lumbar puncture is often performed.

The rapidly progressive form of Q fever pneumonia mimics legionnaires' disease and the pneumonic form of tularemia, and indeed, all the causes of rapidly progressive pneumonia enter the differential diagnosis.

No comments:

Post a comment

Got something to say? We appreciate your comments: