TRANSMISSION
• Human exposure to infectious flea faeces is the typical route of infection, with the organism introduced subdermally through existing breaks of the skin or breaks created by scratches or bites from infected animals. • Bartonella spp. may be present in the oral cavity and on the skin and claws of cats with active flea infestations. • Most humans with B. henselae -associated clinical disease are believed to have been scratched. • Conjunctival exposure is possible, and a single case of a veterinarian infected through needle stick puncture has been reported. 7
IN HUMANS
Patient with Parinaud’s oculoglandular syndrome (conjunctivitis and localised lymphadenopathy) caused by B. henselae
Small papule at the site of a cat-scratch in patient with cat-scratch disease (Public Health Image Library, CDC)
AETIOLOGY AND EPIDEMIOLOGY • Most human cases of Bartonella infection caused by B. henselae have a history of previous contact with cats, particularly kittens, and report being bitten, scratched and/or licked. • Bartonella henselae infection is more commonly diagnosed in young children and teenagers in contact with young kittens and more frequently in children under ten years of age. 8,9 Veterinarians and veterinary practice staff are at increased risk of infection with Bartonella spp. by virtue of increased exposure over time to cats and fleas during physical examinations and procedures. CLINICAL DISEASE • Bartonella henselae can cause multiple clinical syndromes in humans, depending on the virulence of the strain, co-infection with other pathogens and an individual’s immune status and co-morbidities. 10 • Asymptomatic infections are common in humans.
• More severe disease and complications are seen in the immunocompromised (particularly associated with T-cell deficiency). 9 • Classical cat-scratch disease is typically a self-limiting illness. The initial findings are a papule at the site of inoculation (3-10 days post infection), followed by solitary or regional lymphadenopathy 1 to 3 weeks later. The lymphadenopathy may persist for months. Fever, malaise, myalgia, arthralgia, and headache may be seen. • Atypical presentations include: - Endocarditis (particularly in those with pre-existing valvular disease). Bartonella endocarditis and Q fever are the most common causes of culture-negative bacterial endocarditis in humans. As the diagnosis relies on serology, the diagnosis may be missed if serological testing is not requested. - Parinaud’s oculoglandular syndrome – conjunctivitis and local lymphadenitis.
CONTENTS
30 Companion Animal Zoonoses Guidelines
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