IN HUMANS
PREVALENCE AND RISK FACTORS • Human infection with R. felis, known as flea-borne spotted fever (FBSF), is considered an emerging arthropod-borne zoonosis, however there is limited data on its epidemiology globally. • Many cases are likely undiagnosed due to the non-specific nature of clinical signs (e.g. fever, lethargy). Severe disease is considered rare. • Exposure to rickettsial species is significant in veterinary practice. A 2017 serological screening study of veterinarians in Australia demonstrated 16% of participants were seropositive to R. felis and 4.6% seropositive to R. typhi . A further 35.1% of tested veterinarians were seropositive for rickettsial exposure but unable to be differentiated to a particular species. 11 • The first reported cases of human R. felis infection in Australia were documented in Victoria in 2009. Two adults and three children contracted a rickettsial disease, with all patients having extensive close contact with recently acquired R. felis -positive, flea-infested kittens. 12 • A recent study has retrospectively identified fourteen probable Australian cases of R. felis infection in patients between August
2010 and December 2013, with the authors noting rickettsial disease is likely to have been misdiagnosed as murine typhus due to the previous unavailability of specific R. felis serological assays. 13
CLINICAL DISEASE • Clinical disease associated with R. felis infection is similar to other rickettsial infections. Symptoms
may include pyrexia, myalgia and headaches. Cutaneous manifestations may include a maculopapular rash, and rarely a localised eschar at the flea bite site. Most human infection is self-limiting with mild to moderate illness observed. 3,14 • Respiratory and gastrointestinal symptoms including cough, pulmonary oedema, pneumonia, nausea, vomiting and diarrhoea have been reported. Severe clinical manifestations such as neurological signs have also been documented. 14 • Human infection can be diagnosed by PCR or serology. The presence of circulating IgG antibodies most likely indicates previous infection with R. felis, while rising paired acute and convalescent titres may indicate recent infection. Seroconversion may appear a month or more after rickettsial infection. 14
KEY CONSIDERATIONS 1. Rickettsia felis is an emerging flea-borne bacterial pathogen, with data indicating it is more prevalent in cooler, temperate climates. 2. Infection of companion animals is common in Australia, however infection is not associated with disease in these species. 3. Veterinary professionals and animal care workers may be at increased risk of infection with R. felis due to more frequent opportunities for exposure to infected fleas.
Year-round flea control is
recommended for all dogs and cats to minimise exposure
to potentially infected fleas.
References: 1. Brown, L.D., et al (2016) Rickettsia felis, an emerging flea-borne rickettsiosis. Cur Trop Med Rep, 3(2), 27-39. 2. Ng-Nguyen, D., et al (2020) Domestic dogs are mammalian reservoirs for the emerging zoonosis flea-borne spotted fever, caused by Rickettsia felis. Sci Rep, 10(1), 1-10. 3. Yazid Abdad, M., et al (2011) Rickettsia felis, an emerging flea-transmitted human pathogen Emerg Health Threats J, 4(1), 7168. 4. Šlapeta, J., et al (2011) The cat flea (Ctenocephalides f. felis) is the dominant flea on domestic dogs and cats in Australian veterinary practices. Vet Parasitol, 180(3-4), 383-388. 5. Teoh, Y.T., et al (2018) The epidemiology of Rickettsia felis infecting fleas of companion animals in eastern Australia. Parasit Vectors, 11(1), 1-8. 6. Barrs, V., et al (2010) Prevalence of Bartonella species, Rickettsia felis, haemoplasmas and the Ehrlichia group in the blood of cats and fleas in eastern Australia. Aust Vet J, 88(5), 160-165. 7. Schloderer, D., et al (2006) Rickettsia felis in fleas, Western Australia. Emerg Infect Dis, 12(5), 841.
8. Hii, S.-F., et al (2011) Molecular evidence of Rickettsia felis infection in dogs from Northern Territory, Australia. Parasit Vectors, 4(1), 198. 9. Hii, S.F., et al (2011) Molecular evidence supports the role of dogs as potential reservoirs for Rickettsia felis. Vector Borne Zoonotic Dis, 11(8), 1007-1012. 10. Legendre, K.P., et al (2017) Rickettsia felis: a review of transmission mechanisms of an emerging pathogen. Trop Med Infect Dis, 2(4), 64. 11. Teoh, Y.T., et al (2017) Serological evidence of exposure to Rickettsia felis and Rickettsia typhi in Australian veterinarians. Parasit Vectors, 10(1), 129. 12. Williams, M., et al (2011) First probable Australian cases of human infection with Rickettsia felis (cat-flea typhus). Med J Aust, 194(1), 41-43. 13. Teoh, Y.T., et al (2016) Evidence of exposure to Rickettsia felis in Australian patients. One Health, 2, 95-98. 14. Hun, L., et al (2012) An update on the detection and treatment of Rickettsia felis. Res Rep Trop Med, 3, 47.
CONTENTS
43 Companion Animal Zoonoses Guidelines
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