Molecular detection of Rickettsia felis in dogs, rodents and cat fleas in Zambia

Abstract

Background Flea-borne spotted fever is a zoonosis caused by Rickettsia felis , a Gram-negative obligate intracellular bacterium. The disease has a worldwide distribution including western and eastern sub-Saharan Africa where it is associated with febrile illness in humans. However, epidemiology and the public health risks it poses remain neglected especially in developing countries including Zambia. While Ctenocephalides felis (cat fleas) has been suggested to be the main vector, other arthropods including mosquitoes have been implicated in transmission and maintenance of the pathogen; however, their role in the epidemiological cycle remains to be elucidated. Thus, the aim of this study was to detect and characterize R. felis from animal hosts and blood-sucking arthropod vectors in Zambia. Methods Dog blood and rodent tissue samples as well as cat fleas and mosquitoes were collected from various areas in Zambia. DNA was extracted and screened by polymerase chain reaction (PCR) targeting genus Rickettsia and amplicons subjected to sequence analysis. Positive samples were further subjected to R. felis -specific real-time quantitative polymerase chain reactions. Results Rickettsia felis was detected in 4.7% (7/150) of dog blood samples and in 11.3% (12/106) of rodent tissue samples tested by PCR; this species was also detected in 3.7% (2/53) of cat fleas infesting dogs, co-infected with Rickettsia asembonensis . Furthermore, 37.7% (20/53) of cat flea samples tested positive for R. asembonensis , a member of spotted fever group rickettsiae of unknown pathogenicity. All the mosquitoes tested ( n = 190 pools) were negative for Rickettsia spp. Conclusions These observations suggest that R. felis is circulating among domestic dogs and cat fleas as well as rodents in Zambia, posing a potential public health risk to humans. This is because R. felis , a known human pathogen is present in hosts and vectors sharing habitat with humans. Electronic supplementary material The online version of this article (10.1186/s13071-019-3435-6) contains supplementary material, which is available to authorized users.

First report of Rickettsia felis in mosquitoes, USA

“…Opossums are the probable main mammalian reservoirs of R. felis in endemic areas in the USA [4] while dogs have been implicated elsewhere in the world [6].…”

Investigation of Ctenocephalides felis on domestic dogs and Rickettsia felis infection in the Democratic Republic of Sao Tome and Principe

“…It is reasonable as the islands were uninhabited until they became a commercial centre for the slave trade in 16th century. Given that Brazil and the DRSTP were both claimed for (Hii et al, 2015;Kernif et al, 2012 (Figure 1, Supporting Information) (Berrelha et al, 2009;Bessas et al, 2016;Bitam et al, 2006;Boudebouch et al, 2011;Kolo et al, 2016;Mediannikov et al, 2012;Moonga et al, 2019;Palomar et al, 2017;Pérez-Tanoira et al, 2020;Rakotonanahary et al, 2017;Rolain et al, 2005;Sackal et al, 2008;Znazen et al, 2006), and the prevalence was varied among studies. While only 3.7% (2/53) of the cat fleas collected in Mazabuka, Zambia were positive for R. felis infection, the other survey in Ethiopia gave a positive rate of 44%…”

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

“…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].…”

“…A number of mammals have been found to be PCRpositive for R. felis DNA, mainly dogs [5], opossums [3,16], raccoons [17], and rodents [5,16]. Although cats were originally thought to be the mammalian reservoir hosts, experimental infections only revealed brief asymptomatic rickettsemia 2 months post infection, and then only in five of the 16 cats in the study [18].…”