Definition of Q-Fever
Q-Fever is a disease characterized by high fever, chills, muscular pains, headache, and sometimes pneumonia that is caused by a bacterium (Coxiella burnetii of the family Coxiellaceae) of which domestic animals serve as reservoirs and that is transmitted to humans especially by inhalation of infective airborne bacteria
Background – Q-Fever
Q Fever was first described in abattoir workers, people who butchered animals, in the 1920s by Edward Holbrook Derrick. Since the cause of the symptoms was unknown at the time, it was given the name Q Fever, where the “Q” stands from the query. This name was chosen over the alternatives “abattoir fever” and
“Queensland rickettsial fever” in order to avoid slandering the cattle industry or the area where it was discovered. Frank MacFarlane Burnet and Mavis Freeman discovered the actual pathogen in 1937 by isolating it from one of Derrick’s patients, and one year later H.R. Cox and Gordon Davis isolated it from ticks.
It was originally thought to be part of the Rickettsia genus, which contains many tick and flea-borne pathogens; two names were proposed by the different teams that isolated it. Cox and Davis favored Rickettsia daporica, which comes from the Greek word meaning able to pass through pores, the characteristic that made the organism so difficult to isolate. Burnet and Freeman proposed Rickettsia burnetii in reference to Burnet’s role in identifying the organism as part of the Rickettsia genus. Once it was determined that the species differed significantly from other organisms in Rickettsia, it was given its own genus named after Cox and became Coxiella burnetii, its current name
Epidemiology about Q-Fever
Although Q fever affects people worldwide, certain countries have higher incidences of disease. The rates in France (500 cases per million persons) and Australia (38 cases per million persons) are greater than those in the United States (0.28 cases per million persons), most likely reflecting the difference in importance of animal hosts between countries.5 Since Q fever became a reportable disease in the United States in 1999, the number of cases has increased dramatically.
According to a recent study, the cases of Q fever in the United States have increased from 21 cases per year (1978-1999) to 51 cases per year (2000-2004). The states with the highest incidence are in the Midwest; however, California reported the largest total number of cases. These data indicate that Q fever should no longer be considered a disease of occupational hazard (farmers, slaughterhouse workers, or veterinarians) in the United States but rather an endemic environmental disease.
Types of Q-Fever
- Acute Q-Fever
- Chronic Q-Fever
Causes of Q-Fever
Q fever is caused by a bacterial infection with a bacterium called Coxiella burnetii. The bacteria are typically found in cattle, sheep, and goats. The animals transmit the bacteria in:
- Urine
- Feces
- Milk
- Fluids from giving birth
These substances can dry inside a barnyard where contaminated dust can float in the air. Humans get Q fever when they breathe in the contaminated air. In rare cases, drinking unpasteurized milk can cause infection. The bacteria cannot be spread directly from one human to another. The exact frequency of Q fever isn’t known because most cases aren’t reported.
Risk factors of Q-Fever
- Certain occupations place you at higher risk because you’re exposed to animals and animal products as part of your job. At-risk occupations include veterinary medicine, meat processing, livestock farming, and animal research.
- Simply being near a farm or farming facility may put you at higher risk of Q fever, because the bacteria can travel long distances, accompanying dust particles in the air.
- Men are more likely to develop symptomatic acute Q fever.
- Time of year. Q fever can occur at any time of the year, but the number of infections usually peaks in April and May in the U.S.
Signs and Symptoms
About half the people infected with Q fever will get sick. Signs and symptoms of Q fever may include:
- Fever
- Chills or sweats
- Fatigue
- Headache
- Muscle aches
- Nausea, vomiting, or diarrhea
- Chest pain
- Stomach pain
- Weight loss
- Non-productive cough
Complications of Q-Fever
A Q fever recurrence can affect your heart, liver, lungs, and brain, giving rise to serious complications, such as:
- Inflammation of the membrane inside your heart, endocarditis can severely damage your heart valves. Endocarditis is the most deadly of Q fever’s complications.
- Lung issues. Some people who have Q fever develop pneumonia. This can lead to acute respiratory distress, a medical emergency in which you’re not getting enough oxygen.
- Pregnancy problems. Chronic Q fever increases the risk of miscarriage, low birth weight, premature birth and stillbirth.
- Liver damage. Some people who have Q fever develop hepatitis, an inflammation of the liver that interferes with its function.
- Q fever also can cause meningitis, an inflammation of the membrane surrounding your brain and spinal cord.
Diagnosis and Test
To diagnose Q fever, your doctor will perform one or more blood tests, along with additional tests if chronic Q fever is suspected.
Lab tests
Your doctor may want to check your blood for antibodies to the Coxiella burnetii antigen and for evidence of liver damage.
Imaging tests
- Chest X-ray. Q fever can cause pneumonia in some people. A chest X-ray can be used to see if your lungs look healthy.
- If chronic Q fever is suspected, your doctor may do an echocardiogram to check for problems with your heart valves.
Treatment and medications
- Doxycycline and quinolone antibiotics are effective for treatment of Q fever. Treatment usually lasts for two weeks. Rifampin and doxycycline together are given for chronic Q fever. Chronic Q fever requires treatment for at least three years.
- Minocycline has been found to be useful in treating post-Q fever fatigue. The dosage is 100 mg per day for three months.
Prevention
- Q fever can be prevented by the appropriate handling of potentially infective substances. For example, milk should always be pasteurized, and people who work with animals giving birth should carefully dispose of the tissues and fluids associated with birth.
- Industries which process animal materials (meat, wool) should take care to prevent the contamination of dust within the plant. Vaccines are available for workers at risk for Q fever.