Q fever in cats: risk of infection when assisting deliveries
Q fever is prevalent throughout the globe, although there are endemic areas such as the Mediterranean, where there are sometimes sporadic cases or outbreaks among humans.
The clinical expression of Q fever in animals is very mild, generally involving fertility problems, but the situation can be quite different in humans. The acute phase includes nonspecific signs such as fever or general malaise. The chronic phase, by contrast, can lead to more serious problems such as the dreaded endocarditis. The main source of human infection is from livestock, either due to the postpartum inhalation of aerosols containing Coxiella burnetii or through contaminated materials such as manure or straw. However, we must not forget that transmission can occur through pets.
C. burnetii has adapted to live in ticks, which are the vector for transmission from wild animals to livestock. Yet transmission is not just through tick bites; dried tick faeces may lead to infection and consequently Q fever.
The risk of human infection is greatest during the delivery or abortion of infected animals. This is because the bacterium multiplies more rapidly during the last few weeks of gestation reaching very high concentrations in organs and tissues such as the uterus, placenta or foetal membranes and fluids. The placenta from a C. burnetii-infected animal can accommodate over a million microorganisms per gram.
The microorganisms disperse into the surroundings during the birth or abortion. The bacteria can even persist in the air for up to 2 weeks postpartum.
In 2007, a study was conducted on the prevalence of Coxiella burnetii DNA in uterine and vaginal samples from healthy cats. PCR assays did not identify C. burnetii DNA in any of the 47 cats, although a DNA sequence that was 99% homologous to C. burnetii was isolated from four subjects. This shows that cats with no clinical signs of disease may be hosts of C. burnetii, thus extra precaution must be exercised when assisting cats during birth and contact with any discharge during delivery must be avoided to the greatest extent possible.
