Q fever is caused by the Coxiella burnetii organism, and is widespread globally among livestock and domestic ruminants. Sheep, cattle and goats are the most frequent source of human infection, although pets such as dogs and cats may also be a source.
Effect on human pregnancy
Q fever acquired during pregnancy is usually asymptomatic in the mother, although chronic infections may subsequently become apparent. Occasionally, acute Q fever in pregnancy, regardless of whether this is symptomatic or not, may result in an adverse effect on the foetus and may result in a premature birth, a low birth weight, or miscarriage.
Subsequent pregnancies may also be at risk due to the possibility of a chronic infection in the woman.
Symptoms in humans
Most people who are infected have no or very mild symptoms, but very rarely serious illness occurs. Symptoms appear 2 to 3 weeks after exposure and include a flu-like illness with prolonged fever, tiredness, headache, muscle pains and occasionally pneumonia or other complications. Some people develop chronic illness, with symptoms persisting for more than six months. Rarely, endocarditis (heart valve infection) may occur. This generally occurs in people who already have damaged heart valves or who have had heart by-pass surgery.
How the infection is acquired
Inhalation is the main route of transmission to people, either from direct exposure to infected tissues (e.g. birth products) or indirectly through contaminated materials. Humans are at greatest risk of exposure when animals are handled while giving birth. The birth fluids associated with both aborted and normally born young can contain large numbers of Coxiella burnetii organisms if the animal is infected. They may also be present in faeces, urine or raw (untreated) milk. Coxiella burnetii may gain entry to the body by transmission through cuts in the skin, and can sometimes be spread via tick bites. Only small numbers of organisms are required to establish an infection. Person-to-person spread does not generally occur.
How common is the infection
The true incidence of Q fever is probably underestimated because many cases are mild or show no symptoms. The peak incidence of infection in people in the UK is associated with the spring/early summer lambing season.
Tests and treament
Q fever is confirmed by blood testing to detect the presence of antibodies to Coxiella burnetii antigens.
Women who develop Q fever in pregnancy may be treated with co-trimoxazole but professional medical advice should always be sought.
A vaccine is currently licensed for use in cattle and goats. However at present there is no licensed vaccine against Q fever available in the UK for people.
Detecting the disease in animals
In mammals infection can result in late-stage abortion, stillbirths or delivery of weak offspring. Most animals that are infected have no clinical signs, but such individuals can still represent a risk for people.
Precautions on farms (and at other sites where animals are present and may give birth) relate to hygienic practices rather than specific action to minimise or eradicate this disease.
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