Identification of Rickettsia felis DNA in the blood of domestic cats and dogs in the USA

Md Monirul Hoque,Chengming Wang,Bernhard Kaltenboeck,Subarna Barua,Kelly Chenoweth,Patrick John Kelly

doi:10.1186/s13071-020-04464-w

Md Monirul Hoque, Chengming Wang + Show 4 more

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https://doi.org/10.1186/s13071-020-04464-w

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Abstract

BackgroundThe main vector and reservoir host of Rickettsia felis, an emerging human pathogen causing flea-borne spotted fever, is the cat flea Ctenocephalides felis. While cats have not been found to be infected with the organism, significant percentages of dogs from Australia and Africa are infected, indicating that they may be important mammalian reservoirs. The objective of this study was to determine the presence of R. felis DNA in the blood of domestic dogs and cats in the USA.MethodsThree previously validated PCR assays for R. felis and DNA sequencing were performed on blood samples obtained from clinically ill domestic cats and dogs from 45 states (2008–2020) in the USA. The blood samples had been submitted for the diagnosis of various tick-borne diseases in dogs and feline infectious peritonitis virus, feline immunodeficiency virus, and Bartonella spp. in cats. Phylogenetic comparisons were performed on the gltA nucleotide sequences obtained in the study and those reported for R. felis and R. felis-like organisms.ResultsLow copy numbers of R. felis DNA (around 100 copies/ml whole blood) were found in four cats (4/752, 0.53%) and three dogs (3/777, 0.39%). The very low levels of infection in clinically ill animals is consistent with R. felis being an unlikely cause of disease in naturally infected dogs and cats. The low copy numbers we found emphasize the requirement for very sensitive PCRs in prevalence studies.ConclusionsThe low prevalence of naturally infected PCR-positive cats is further evidence that cats are unlikely to be important reservoirs of R. felis. Similarly, the low prevalence in dogs suggests they are not important reservoirs in the USA. Investigations should continue into the role other mammalian species may be playing in the epidemiology of R. felis infections. Graphical

Highlights

The intracellular bacterium Rickettsia felis is the agent of flea-borne spotted fever or cat-flea typhus [1, 2], an emerging zoonotic disease
We used whole blood samples in EDTA from domestic cats (n = 752) in 43 states submitted for the molecular diagnosis of Feline infectious peritonitis (FIP), Feline immunodeficiency virus (FIV), Feline leukemia virus (FeLV), and Bartonella infections between 2008 and 2020
The DNA was eluted in 40 μL elution buffer, and the 20-μL volume of each sample remaining after the tickborne diseases or FIP, FeLV, FIV, and Bartonella PCR assays had been performed was preserved at − 80 oC until the PCR assays to detect R. felis were performed in this study

Summary

Introduction

The intracellular bacterium Rickettsia felis is the agent of flea-borne spotted fever or cat-flea typhus [1, 2], an emerging zoonotic disease. Since the first report in 1994 of R. felis in a person in Texas [3], infections have been described from around the world, with R. felis implicated as the causative agent of an important febrile illness in sub-Saharan Africa [4, 5] and flea-borne spotted fever considered a global emerging threat to human health [6]. The main vector and reservoir host of Rickettsia felis, an emerging human pathogen causing flea-borne spotted fever, is the cat flea Ctenocephalides felis. Nov 2015 American domestic shorthair; 8-month; female; for FIPnegative Fritz Cat Spring, TX. 7-month; American domestic shorthair; male, castrated; for R. felis R. felis IRBE32218089 Cat Granada Hills, CA July 2014 5-year; male castrated; Siamese; for FIP-negative Clara Cat Brooklyn, NY

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