Evidence of exposure to Rickettsia felis in Australian patients

Abstract

Rickettsia felis is an emerging zoonosis, causing flea-borne spotted fever (FBSF). Serological diagnosis is typically confounded by cross-reactivity with typhus group rickettsiae and prior to the development of specific serological methods, cases of FBSF in Australia were misdiagnosed.Patient sera tested between August 2010 and December 2013 and known to be seropositive to R. typhi by immunofluorescence antibody testing (IFAT) were subsequently retested against R. felis using an R. felis-specific IFAT. Sera of 49 patients were of a sufficient quality to be included in re-analysis. A classification of FBSF and murine typhus (MT) was attributed to fourteen and seven patients respectively, based on a minimum four-fold higher antibody titre to R. felis than to R. typhi and vice versa. Twenty-eight patients were classified as indeterminate for either R. felis or R. typhi (antibody titres within two-fold of one another).Historically, it is likely that Australian patients clinically ill with FBSF were misdiagnosed. It is important that medical practitioners consider FBSF as part of their differential diagnoses, and obtain relevant history with regard to patient's exposure to domestic pets and their fleas. Australian microbiology diagnostic laboratories should include serological testing for R. felis as part of the diagnostic panel for febrile diseases. Veterinarians are encouraged to increase their awareness of this emerging zoonosis and advocate flea control in pets.

More bark than bite: Comparative studies are needed to determine the importance of canine zoonoses in Aboriginal communities. A critical review of published research

“…R. felis , the agent of fleaborne spotted fever in humans, is typically transmitted through the bite of an infected cat flea ( Ctenocephalides felis ). Clinical infection ranges from fever, headaches, chills, muscle aches, joint pain and possible eschar at the bite site to a more severe, multisystemic disease as a result of a widespread vasculitis (Maina et al., ; Teoh et al., ). Molecular techniques have been used to identify R. felis infection in cat fleas from multiple sites in Western Australia (Schloderer, Owen, Clark, Stenos, & Fenwick, ).…”

“…Williams, Izzard, Graves, Stenos, and Kelly () reported R. felis infection in two adults and three children from Victoria. Previously, many infections in Australia may have been misdiagnosed as murine typhus as serological diagnosis was not specific and was typically confounded by cross‐reactivity with typhus group rickettsiae (Teoh et al., ). Dogs are often infested with cat fleas, and infected dogs can appear physically healthy, which may be characteristic of reservoir hosts of R. felis (Hii et al., ).…”

Serological evidence of exposure to Rickettsia felis and Rickettsia typhi in Australian veterinarians

“…This ensured rigor of the classification of the R. felis - and R. typhi -exposed patients as high compared to previous serosurveys which utilized protocols that used lower cut-off titers [31] whilst being able to confidently classify the etiological agent [4]. Consequently, the number of participants testing positive for an indeterminate rickettsial infection was produced.…”

“…Since then, multiple other clinical cases of human infection in patients in New South Wales, Queensland, South Australia, Tasmania and Western Australia have been confirmed [4]. Risk factors for exposure to R. felis however were not described.…”

Bacterial canine vector-borne zoonotic diseases in “One Health” concept

“…It seems that clinical findings depend on the region of infection and include fever in patients from the tropics or fever associated with cutaneous manifestations in patients from Europe or America. Recently, FBSF infection was attributed in nine patients' sera found reactive to R. felis, in Australia [64].…”