Q fever

Medical quality assurance by Dr. Albrecht Nonnenmacher, MD at March 15, 2016
StartDiseasesQ fever

Q fever is the result of a bacterial infection caused by the bacterium Coxiella burnetti. The bacteria are resilient in most environmental conditions. Humans are particularly vulnerable to the bacteria, so only a small number of the organisms are needed to cause infection. As a result, the Coxiella burnetti bacterium is considered a possible bacteriological weapon.

Contents

Definition & Facts

Q fever was recognized as a human disease in the United States in the 1940s. The “Q” in the name originally stood for “query” since the cause of the infection was unknown at the time. According to the CDC, there were approximately 131 cases of Q fever reported in the U.S. in 2010. Since Q fever can be mistaken for other illnesses and many people never develop symptoms, the number of cases may be vastly under-recognized.

Roughly 10 to 20 percent of those in high-risk occupations have Coxiella burnetti antibodies, which suggests they have been infected at some point. On average, between 50 and 70 percent of individuals infected with Q fever require hospitalization.

The majority of Q fever cases in the United States occur in western and plains states where ranching is the most prevalent. The number of cases of Q fever tends to peak around April and May as outdoor activity increases and animals start to give birth.

Symptoms & Complaints

Many individuals with Q fever never develop symptoms. Those that do develop symptoms typically notice them three to 30 days following exposure. The most common symptoms of acute Q fever include:

Chronic Q fever can result in heart and liver inflammation and complications of the central nervous system. Pregnant women, people with heart valve problems, and those with weakened immune systems are most at risk for chronic infection. Q fever can result in miscarriage and pre-term delivery in pregnant women. Approximately 10 to 25 percent of patients report experiencing post-Q fever fatigue syndrome characterized by chronic fatigue, muscles aches, mood swings, and difficulty sleeping.

Causes

The organism responsible for Q fever is primarily found in sheep, goats, and cattle. The bacteria are present in the urine, feces, breastmilk, placenta, and amniotic fluid of infected animals. When this excreta dries, the bacteria become airborne in the barnyard dust. Humans become infected when they breathe in the contaminated dust.

In rare cases, the bacteria have been transmitted through tick bites, contaminated food, and unpasteurized dairy products. According to the Centers for Disease Control, human to human transmission is very rare. Those most at risk for Q fever include veterinarians, farmers, and those who live near farms. Sporadic outbreaks have occurred among workers at meat processing plants and laboratories that handle the bacteria.

Diagnosis & Tests

The symptoms of Q fever are similar to other conditions, so it can be difficult to make a diagnosis based on symptoms alone. Patient history plays a significant role in reaching a preliminary diagnosis of Q fever, especially if the individual works in a high-risk occupation or lives or has traveled to an area where farm animals are prevalent.

A diagnosis of Q fever can be confirmed with a blood antibody test; however, these tests often come back negative during the first week to 10 days of the illness. For this reason, the CDC urges doctors to use their best judgment in treating Q fever based on clinical suspicion alone, since treatment is most effective when started within the first three days of illness.

Doctors are urged not to delay or withhold treatment while waiting for lab confirmation or on the basis of an initial negative result. In cases of possible chronic infection, the doctor may also order liver function tests to check for inflammation, chest X-rays to rule out pneumonia, and an echocardiogram to ensure there is no damage to the heart valves.

Treatment & Therapy

Q fever is rarely fatal, and asymptomatic cases often resolve without treatment. Antibiotic therapy is very effective in treating symptomatic cases of Q fever. Doxycycline is the recommended antibiotic for treating Q fever and preventing potential complications. In cases of acute Q fever, treatment typically lasts two to three weeks and is most effective when started within 72 hours of developing a fever.

Individuals with chronic Q fever require a much longer course of treatment. This typically involves a combination of doxycycline and hydroxychloroquine for at least 18 months. Even after treatment, individuals with chronic Q fever should continue to get regular follow-up tests since the infection can recur. Chronic Q fever can cause endocarditis, which means that surgery may be required to replace damaged heart valves.

Prevention & Prophylaxis

A Q fever vaccine available in Australia has proven to be effective for those who work in high-risk occupations and environments. The vaccine has not been approved for use in the United States at this time. Prevention efforts are primarily aimed at high-risk individuals and reducing environmental contamination and exposure.

Individuals working with sheep, goats, and cattle should ensure that they properly dispose of any placenta and other birth products. All exposed holding and birthing areas should be disinfected and decontaminated. Animal holding facilities should be located well away from populated areas. Imported animals should be quarantined and observed for signs of infection. Barns or laboratories housing potentially infected livestock should have restricted access.

Lab workers coming in contact with the C. burnetti bacteria should follow proper procedures for bagging, washing, and autoclaving all lab equipment and clothing. It is also important to only use pasteurized dairy products to avoid possible exposure to C burnetti and other bacteria. Practicing good hand hygiene after working with animals is an essential part of reducing the risk of Q fever as well as a host of other diseases.

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