IN ANIMALS
• In Australia, studies have demonstrated bacteraemia in 16-35% of cats based on blood culture or PCR. 4,5 In line with other research globally, infection is highest in young animals and those with fleas. Higher prevalence has been reported in feral compared to owned animals, likely associated with greater risk of ectoparasitism. Seroprevalence is higher in older cats, with bacteraemia greater in younger cats. • Seroprevalence is typically reported at twice the rate of bacteraemia in the same population, however, as there is a poor association with bacteraemia, serology is not recommended for diagnosis.
CLINICAL DISEASE Infected cats are typically asymptomatic. A number of disease associations have been proposed for B.
The cat flea (Ctenocephalides felis) is the primary vector for Bartonella henselae
henselae in cats, including sporadic reports of myocardial, endocardial and ocular disease, however data are inconclusive. 6 Other Bartonella spp. ( B. clarridgeiae, B. quintana, B. koehlerae and B. bovis ) are less commonly isolated from cats than B. henselae , however challenges relating to isolation and identification make interpretation of the importance of these species challenging. • Given that Bartonell a spp. can cause chronic intra-erythrocytic and endotheliotropic infections (a bacterial strategy for persistence of infection) in cats, dogs and other animal species, infections can potentially span weeks, months or years in duration. • Chronic waxing-waning bacteraemia that persists for months or even years has been documented in young cats. 6 In a natural setting prolonged bacteraemia may be due to reinfection. • Less commonly, B. henselae may infect dogs. Unlike cats, infection in dogs may result in disease, with endocarditis being the most commonly reported condition.
AETIOLOGY AND EPIDEMIOLOGY • Bartonella henselae is a vector-borne pathogen, with the cat flea ( Ctenocephalides felis ) the primary vector.
Cats are the primary reservoir species for B. henselae, however dogs may also be infected. • The organism is transmitted between cats via flea faeces. After a blood meal from a B. henselae -infected cat, bacterial numbers rise within the flea’s intestinal tract. Viable organisms are shed in flea faeces, with the bacteria remaining viable in flea faeces for at least 9 days. 1 • Transmission occurs primarily through intradermal inoculation of Bartonella -containing flea faeces into skin wounds or bites. Such wounds may be self-inflicted in response to irritation caused by the vector. Less commonly, transmission may occur through direct inoculation onto the conjunctiva. • It has been demonstrated that transmission does not occur between cohabitating cats in the absence of flea infestation. • Bartonella henselae has been identified in ticks, but the contribution of this possible vector to the epidemiology of disease in cats is currently unknown. 2 • Iatrogenic transmission through blood transfusion may occur. 3 PREVALENCE AND RISK FACTORS • Prevalence ranges widely dependent on the global location and study population. Prevalence is highest in warmer regions, owing to the more favourable conditions for the primary vector.
DIAGNOSIS • Accurate diagnosis is challenging, as all of the available diagnostic tests have a low sensitivity,
meaning a negative result cannot be trusted to rule-out infection. Culture or PCR of blood or tissues, and detection of antibodies in serum can all be used to aid diagnosis, however routine screening is generally not recommended. As Bartonella is relatively non-pathogenic in cats there are limited indications for feline testing.
CONTENTS
Companion Animal Zoonoses Guidelines 29
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