Bartonella could be responsible for a hidden epidemic of disease in animals and humans, according to a US veterinary infectious disease expert.
Edward Breitschwerdt, from the Centre for Comparative Medicine and Translational Research at North Carolina State University College of Veterinary Medicine, updated doctors and veterinarians at the Australasian Society for Infectious Diseases Zoonoses conference in Brisbane last month.
He warned that Bartonella species, a group of Gram negative rods, represented an occupational hazard for veterinarians in particular, with exposure possible via many routes including insect vectors, scratches and bites, needle-stick injury and potentially inhalation of flea faeces. Phylogenetically, the disease is closely related to Brucella species and can cause similar chronic, relapsing disease manifestations that are challenging to diagnose and often refractory to treatment.
Breitschwerdt said bartonellosis is difficult to diagnose in humans and animals because it is caused by an intracellular bacteria that is difficult to detect or isolate, may be acquired from a range of reservoirs and can be transmitted by multiple vectors and means.
Bartonella species are also associated with a range of disease presentations in both human and canine patients, including peliosis hepatis, bacillary angiomatosis, endocarditis, myocarditis, granulomatous lymphadenitis, encephalitis, immune mediated thrombocytopenia and immune mediated haemolytic anaemia.
One of the major challenges in Bartonella research has been cultivating the organism. Bartonella species prefer to grow in an insect growth medium, which isn’t surprising given transmission of these bacteria by a variety of insect vectors including fleas, ticks, lice, keds, mites, sand-flies and even spiders.
Five different Bartonella species have been isolated from the cat flea alone.
“Unfortunately we’re still teaching veterinary students that fleas are obnoxious critters that cause itch and induce allergies in pets,” Breitschwerdt said. “But fleas also transmit Bartonella. The message should be ‘kill fleas, kill fleas, kill fleas’”.
Potential natural reservoirs include rodents, companion animals, wildlife species, ruminants and even people. Many animals are asymptomatic. Needle stick transmission of Bartonella henselae and Bartonella vinsonii have been reported, in one case from a dog to a veterinarian during fine-needle aspiration of a cutaneous mass.
“Bartonellosis is the most important one health problem for the veterinary profession due to the large number of vectors and reservoirs, the diverse modes of transmission and challenges associated with both diagnosis and treatment ,” he said.
Breitschwerdt urged veterinarians to take precautions to reduce the risk of infectious disease transmission in the workplace. Further studies are underway to characterise Bartonella syndromes in humans and animals, and to understand further the incidence of bartonellosis in the veterinary profession.
Veterinarians with an interest in infectious diseases can join the Australasian Society for Infectious Diseases. For information visit www.asid.net.au