Q fever requires 18 months or more to treat, researchers find

At least 18 months of treatment are required to cure an infection of the heart lining or valves resulting from Q fever, and an additional six months will most likely be required if the patient has a prosthetic valve, researchers reported Wednesday. The findings have relevance because of the current — and unusual — outbreak of Q fever in the Netherlands, where 3,483 cases have been diagnosed since 2007 and six people have died.

Q fever is caused by infections of the bacterium Coxiella burnetti, one of the most infectious bacteria in the world Transmitted primarily by cattle, sheep and goats, one solitary C. burnetti bacterium is sufficient to trigger an infection. The disease was first found in slaughterhouses in Australia in the late 1930s; the Q stands for “query,” an appellation that was then applied to diseases for which no cause was known. The acute phase of the disease is characterized by fever, malaise, muscle pain, confusion and other symptoms. The most common treatment is with the antibiotic doxycycline, which is most effective if therapy is begun within three days of the beginning of symptoms. Unfortunately, the initial diagnosis is often missed, which makes treatment more difficult. Some patients may develop a chronic form of Q fever anywhere from one to 20 years after the initial infection has apparently been cured. The chronic form of the disease is more serious and must be treated with a combination of drugs, most often doxycycline and hydroxychloroquine.

About 1% to 5% of patients with acute Q fever and 60% to 80% of those with the chronic form develop endocarditis, a persistent and hard-to-treat infection of the inner lining of the heart or the heart’s valves. In the 1970s, the death rate from Q fever endocarditis was greater than 60%, but the rate has been reduced to about 5% today by combining hydroxychloroqune with doxycycline. But the duration of treatment has remained somewhat controversial.

Dr. Didier Raoult of the University of the Mediterranean in Marseille, France, has been studying Q fever endocarditis for 26 years. In a report in the journal Lancet Infectious Diseases, he and his colleagues presented findings on 104 patients diagnosed with the disease between 1983 and 2006. The patients were given clinical examinations, including analysis of blood for infections, every month for six months, every three months for another year, every six months for another two to three years, and then yearly for life. Biopsy specimens of heart valves were also performed frequently. He found that 18 months of treatment sterilized the valves of all but three of the patients, and another six months of therapy cured two of the remaining three. But six patients suffered relapses after 15 to 57 months.

In an editorial accompanying the report, Dr. Thomas Marrie of Dalhousie University in Halifax, Canada, noted that “the paper shows young investigators that the lifelong study of an illness — whether it is one’s main clinical or research endeavor or not — can be very rewarding.” Marrie noted that such long-term treatment can lead to the development of drug resistance and that researchers should be aware of that possibility because resistance would make treatment even more complicated. The ultimate solution to the problem, he said, would be the development of a vaccine against C. burnetti. Trials of an experimental vaccine in slaughterhouses in Australia led to only three cases of Q fever among 2,716 vaccinated workers, compared to 52 cases among 2,012 unvaccinated workers. “Yet outside of Australia, there has been little acceptance of a vaccine strategy for prevention of Q fever,” he concluded.