What Is Q Fever?
Q fever is caused by the rickettsial-like bacillus Coxiella burnetii and presents as an acute or chronic disease. Coxiella burnetii is a small, pleomorphic, intracellular bacillus and is no longer classified as Rickettsia. It has been classified as belonging to the Proteobacteria group of Legionella species by molecular studies. These bacteria primarily infect farm animals which in turn act as reservoirs that pass on the infection to humans. The bacteria are seen in these animals' stools, milk, urine, and tissues.
The febrile illness affects the respiratory system mainly. In the acute presentation, there are symptoms of fever, malaise, headache, and interstitial pneumonitis. Pregnant women with acute Q fever have an increased chance of preterm delivery and abortion. The disease's manifestations in the chronic form reflect the organ system affected. Though it affects <5 % of patients, it presents as hepatitis or endocarditis and rarely osteomyelitis. Diagnosis is made using serologic techniques, isolating the organism, or polymerase chain reaction (PCR). The infection is usually treated with Doxycycline.
How Is Q Fever Transmitted?
Q fever is often transmitted to people who work on farms and those who work in close contact with the farm animals or their products. Infection can occur by inhaling the aerosol from the infected animals or by consuming their products. C. burnetii is used as a biological warfare agent as it is a highly virulent bacteria that resist inactivation and remains potent in dust and stool for months. Human-to-human transmission is extremely rare.
What Are the Symptoms of Q Fever?
The presentation of Q fever varies from person to person. The acute form is often asymptomatic, and the chronic condition may show serious complications. The bacteria show an incubation period of 18 to 21 days.
Acute Q Fever:
After the incubation period of two to three weeks, the onset of acute Q fever begins. It is usually asymptomatic but sometimes presents with influenza-like symptoms (fever, malaise, anorexia, headaches, and myalgia). Additional symptoms like cough, sore throat, and chest pain may persist. No skin rashes are associated with this. Pneumonia (fluid-filled lungs) and hepatitis (inflammation of the liver) are commonly associated with the acute form of Q fever. Pneumonia might progress to acute respiratory distress syndrome (ARDS), and hepatitis may cause jaundice (yellowing of the skin and the eyes). Other complications may include myocarditis, pericarditis, and petechiae. In a rare presentation, Q fever can also show inflammation of the brain tissues, thyroids, kidneys, or genitals.
Chronic Q Fever:
Chronic Q fever may occur with or without a previous history of acute Q fever and may last for months to years. It mostly occurs in individuals with a prosthetic heart valve, abnormalities in blood vessels, or those with weak immune systems. It causes damage to the heart valves and tissues by causing inflammation of the endocardium of the heart. It can also show alveolar changes such as osteomyelitis or osteoarthritis, chronic hepatitis, and chronic pulmonary disease. They might present with chronic fatigue, prolonged fever, and arthralgia and pose a risk of developing an illness related to the heart and blood vessels.
How Is Q Fever Diagnosed?
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Immunofluorescence Assay (IFA): This is the diagnostic method of choice. Enzyme-linked immunosorbent assay (ELISA) may be an alternative to this test.
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Polymerase Chain Reaction (PCR): Organisms can be identified in the biopsy specimens by a PCR test. However, negative results do not signify the absence of the organism.
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Isolation of Clinical Specimens: C. burnetti can be isolated only by advanced research laboratories. Sputum cultures and routine blood tests are negative.
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Chest X-Ray: Maybe be required to analyze the respiratory symptoms and signs and can present with pleural effusion, opacities, and consolidation.
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Complete Blood Count: The complete blood count may show normal values, but only 30 % of infected individuals show an elevated white blood cell count.
How Is Q Fever Treated?
The treatment of choice for Q fever is administering antibiotics. Mild cases often resolve without treatment. However, healthcare providers recommend antibiotic therapy even for subclinical cases of Q fever as it reduces the duration of infection. Doxycycline is the antibiotic of choice for Q fever and works best if started within three days of infection. The dosage for the acute Q fever is 200 mg of Doxycycline once orally followed by 100 mg twice a day orally, in adults until the patient shows improvement.
Chronic form Q fever is more complex to treat. The manifestation of endocarditis may require long-term antibiotic treatment, which usually involves treatment with a combination of Doxycycline and Hydroxychloroquine. This combination drastically reduces the possibility of death. The optimal duration of therapy is not certain (as a few patients continue on treatment lifelong) and varies from person to person.
The dosage for chronic Q fever is Doxycycline 100 mg twice a day orally in adults along with Hydroxychloroquine 200 mg every 8 hours orally recommended currently. Hydroxychloroquine should be taken with caution as it causes prolongation of QT interval in patients. Other than antibiotic treatment, replacement of damaged nerves and surgical management must be undertaken if necessary. An infectious specialist may aid in managing the complications of the disease. Currently, only Australia has a licensed vaccine against Q fever. However, the U.S. Food and Drug Administration (FDA) has not approved any vaccine for Q fever to date.
Conclusion:
Q fever, the disease transmitted from farm animals, can be prevented by avoiding contact with farm animals (especially when the animals are giving birth) and consuming only pasteurized milk. It can be managed to a great extent by early treatment intervention and care. People at high risk- older men, farmworkers, people with heart valve defects, heart valve implants, or endocarditis must follow preventive measures to avoid developing the complex form of the disease. Therefore, patients should understand and note their symptoms and report to their physicians for timely treatment.
