What is Q fever?

Q fever is a widespread zoonosis caused by the Gram-negative bacterium Coxiella burnetii. The name “Q fever” was derived from “Query fever” and was given in 1935 following an outbreak of febrile illness in an abattoir in Queensland, Australia. Q fever is a zoonosis with a worldwide distribution with the exception of New Zealand. The bacterium affects sheep, goats, cattle, dogs, cats, birds, rodents, and ticks. Infection in nature is maintained and transmitted by ticks as the principal vector and reservoir. Cattle, sheep, and goats are the most important source of human infections and they shed the bacterium in birth products, faeces, milk, and urine. Humans are vulnerable to Q-fever, and infection can result from even a few organisms. Transmission to human beings is mainly accomplished through inhalation of contaminated aerosols. In humans, Q fever can manifest as an acute disease (mainly as a self-limited flu-like illness, pneumonia, or hepatitis) or as a chronic disease (mainly endocarditis but also hepatitis and chronic fatigue syndrome). Coxiella burnetii infections in pregnant women may result in abortions, premature deliveries, and stillbirths. In contrast, in infected animals, Q fever (coxiellosis) is in most cases, persistent and strikingly asymptomatic. The exact frequency of Q fever is not known, since most cases are unreported.

What causes it?

Q fever is caused by coxiella burnetii- an obligate intracellular bacterium that causes a worldwide zoonosis and can be misused as a biological warfare agent. The genus coxiella is morphologically similar to rickettsia but with a variety of genetic and physiological differences. Coxiella burnetii is a small gram-negative bacterium that is highly resistant to environmental stresses such as high temperature, osmotic pressure, ultraviolet light and can survive standard disinfectants. The bacterium is typically found in cattle, sheep, and goats. The infected animals transmit the bacterium in their urine, faeces, milk, and fluids from giving birth. These fluids 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 unpasteurised milk can cause infection. The bacterium cannot be spread directly from human to human.

What are the symptoms?

The symptoms include high fevers; severe headache; chills and/or sweats; non-productive cough; nausea; vomitting; diarrhoea; abdominal pain; and chest pain.

How is Q fever transmitted?

Sheep, goats and cattle are the main source of Q fever. It is spread from contact with excretions such as milk, urine, faeces and the afterbirth of infected animals as well as contact with contaminated meat and wool. Often, the bacterium can exist for extended periods of time in soil and dust. The bacterium is found everywhere and is extremely sustainable and virulent: a single organism is able to cause an infection. The common way of infection is inhalation of contaminated dust (wind plays an important factor in spreading the infection), and particularly birthing products. Ticks can transfer the pathogenic agent to other animals and they are considered to maintain and transmit Q fever in nature as the principal vector and reservoir.

Some studies have shown more men to be affected than women, which may be attributed to different employment rates in typical professions.

What are the ways to treat it?

Tetracyclines are the antibiotics of choice for treatment of Q fever and should take place in consultation with an infectious diseases specialist. Commonly used antibiotics include doxycycline, tetracycline, chloramphenicol, ciprofloxacin, ofloxacin, and hydroxychloroquine. For instance, when individualised therapy is required, a 14-to 21-day course of doxycycline usually is used. In a mass casualty situation, a 5-to 7-day course of doxycycline is recommended, both for therapy and prophylaxis. For chronic infections such as endocarditis, 18 months of doxycycline supplemented with hydroxychloroquine is currently considered the best therapy. Q fever in pregnancy is especially difficult to treat because doxycycline and ciprofloxacin are contraindicated in pregnancy. The preferred treatment is five weeks of co-trimoxazole.

How can one prevent its infection?

A vaccine for Q fever has been developed and has successfully protected humans in occupational settings in Australia. However, this vaccine is not commercially available at the moment in other countries. Persons wishing to be vaccinated should first have a skin test to determine a history of previous exposure. Individuals who have previously been exposed to C. burnetii should not receive the vaccine because severe reactions, localised to the area of the injected vaccine, may occur. A vaccine for use in animals has also been developed. In addition to vaccination, the following measures should be used in the prevention and control of Q fever: Educate the public on sources of infection; appropriately dispose placenta, birth products, foetal membranes, and aborted foetuses at facilities housing sheep and goats; restrict access to barns and laboratories used in housing potentially infected animals; use only pasturised milk and milk products; use appropriate procedures for bagging, autoclaving, and washing of laboratory clothing; vaccinate (where possible) individuals engaged in research with pregnant sheep or live C. Burnetii; and quarantine imported animals.

Coxiella burnetii is a highly infectious agent that is rather resistant to heat and drying. It can become airborne and inhaled by humans. A single C. burnetii organism may cause disease in a susceptible person. This agent has a past history of being developed for use in biological warfare and is considered a potential terrorist threat.

How is it diagnosed?

Diagnosis is usually based on serology (looking for an antibody response) rather than looking for the organism itself. Serology is useful for detection chronic infection as high antibody levels are found against the virulent form of the bacterium. Molecular detection of bacterial DNA using polymerase chain reaction is increasingly used. Culture is technically difficult and not routinely available in most microbiology laboratories because of biosafety considerations. Q fever can cause endocarditis (infection of the heart valves) which may require transoesophageal echocardiography to diagnose. Q fever hepatitis manifests as an elevation of ALT and AST, but a definitive diagnosis is only possible on liver biopsy, which shows the characteristic fibrin ring granulomas.

If one thinks one has Q fever, what should be done?

If someone has been exposed to Q fever but does not have any symptoms, prophylactic treatment (treatment to prevent someone from getting the disease) is not recommended. If someone develops any of the symptoms of Q fever, he or she should be evaluated promptly by a medical professional.

Is this disease common in Nigeria?

There is very little information available about the prevalence of Coxiella burnetii in Africa. However, few and limited serological studies previously carried out in human and animal populations in Nigeria have revealed the occurrence of the disease in the country. There is need for a comprehensive nationwide epidemiological study to determine the actual occurrence of Q fever in Nigeria.

What is your advice to poultry farmers?

Birds can also be infected, and Coxiella burnetii has been isolated from pigeons, chickens, ducks, geese, and turkeys. Humans may acquire Q fever from infected domestic poultry by consumption of raw eggs or inhalation of fomites contaminated with droppings and fluids from infected poultry. Poultry farmers should take precautionary measures indicated for high risk workers and proper disposal of poultry waste products including handling and consumption of raw eggs.