IN ANIMALS continued
• A large seroprevalence study in dogs reported C. burnetii exposure in 1.9-6.5% of dogs, with prevalence dependent on the study population. Prevalence in shelter dogs, breeding dogs, and pet owned dogs (1.9%, 2.3% and 3.0% respectively) were not significantly different, while free-roaming dogs in remote Aboriginal communities were 2.8 times more likely to be seropositive than dogs from other populations (prevalence 6.5%). 6 A study of pig hunting dogs in tropical north Queensland reported a seroprevalence of 23%. 7 • A subsequent study in north-western NSW, in an area with a relatively high incidence of human Q fever, reported a seroprevalence in healthy dogs and cats of 26.1% and 13.1% respectively, suggesting that exposure of pets and people occurs through a shared common source. 2 In this study, C. burnetii DNA was not detected in blood or tissues (post desexing) from any dogs or cats, suggesting bacterial shedding is uncommon. 2
for Coxiella -seropositivity in cats. 2 Feeding of raw meat is a common husbandry practice among Australian cat breeders, practiced by 89% in a published study. 3 • Coxiella burnetii has been identified in a range of different arthropod vectors of which ticks are the most common, however the importance of vector-borne transmission is not clear. 4 PREVALENCE AND RISK FACTORS • In a large study of cats in eastern Australia, Coxiella seroprevalence ranged from 0-9.3%, depending on the lifestyle of the cats. 5 In this study no feral or shelter cats were seropositive. Owned pet cats had a seroprevalence of 1% while cattery-confined breeding cats had a prevalence of 9.3%. Exposure to periparturient animals poses the greatest risk for zoonotic infection as high numbers of organisms can be found in placentae and reproductive fluids, including those from cats with normal parturition
CLINICAL DISEASE • There is a lack of data supporting a role for naturally acquired C. burnetii in causing clinical disease in dogs
and cats. • There is no direct evidence of reproductive disorders in dogs or cats due to coxiellosis, 8 however outbreaks of Q fever in humans have been reported associated with exposure to parturient dogs and cats who have given birth to young which have died during the immediate perinatal period. 9,10 • In experimentally infected cats, non-specific clinical signs of fever, lethargy and anorexia have been reported. 11 DIAGNOSIS • Laboratory diagnosis of coxiellosis in dogs and cats is not commonly performed outside of a research setting. Confirmation of coxiellosis in dogs and cats likely requires serial PCR and serological testing, however a validated method for these species has not been determined as it has for humans.
TRANSMISSION
• High numbers of organisms are found in placentae and reproductive fluids, therefore exposure to periparturient animals poses the greatest risk. • Infection is primarily through inhalation of aerosolised bacteria or dust contaminated with birth products. Very low infectious dose is reported in humans via inhalation. 12
CONTENTS
Companion Animal Zoonoses Guidelines 64
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