Cofeeding intra‐ and interspecific transmission of an emerging insect‐borne rickettsial pathogen

Abstract

Cat fleas (Ctenocephalides felis) are known as the primary vector and reservoir of Rickettsia felis, the causative agent of flea‐borne spotted fever; however, field surveys regularly report molecular detection of this infectious agent from other blood‐feeding arthropods. The presence of R. felis in additional arthropods may be the result of chance consumption of an infectious bloodmeal, but isolation of viable rickettsiae circulating in the blood of suspected vertebrate reservoirs has not been demonstrated. Successful transmission of pathogens between actively blood‐feeding arthropods in the absence of a disseminated vertebrate infection has been verified, referred to as cofeeding transmission. Therefore, the principal route from systemically infected vertebrates to uninfected arthropods may not be applicable to the R. felis transmission cycle. Here, we show both intra‐ and interspecific transmission of R. felis between cofeeding arthropods on a vertebrate host. Analyses revealed that infected cat fleas transmitted R. felis to naïve cat fleas and rat fleas (Xenopsylla cheopis) via fleabite on a nonrickettsemic vertebrate host. Also, cat fleas infected by cofeeding were infectious to newly emerged uninfected cat fleas in an artificial system. Furthermore, we utilized a stochastic model to demonstrate that cofeeding is sufficient to explain the enzootic spread of R. felis amongst populations of the biological vector. Our results implicate cat fleas in the spread of R. felis amongst different vectors, and the demonstration of cofeeding transmission of R. felis through a vertebrate host represents a novel transmission paradigm for insect‐borne Rickettsia and furthers our understanding of this emerging rickettsiosis.

Detection of rickettsiae in fleas and ticks from areas of Costa Rica with history of spotted fever group rickettsioses

“…At study sites, infection rate with this Rickettsia was much higher in pools of C. felis, but they were also detected in P. simulans, which commonly co-infest dogs in these areas (Troyo et al, 2012b). The lower infection rate in P. simulans, despite a large number of flea pools analyzed from the same vertebrate hosts, agrees with other studies that show absence of rickettsiae in Pulex fleas and may indicate alternative and less-frequent infection routes, such as co-feeding (Oteo et al, 2014;Brown et al, 2015). In this regard, there are few reports of DNA of R. felis or similar rickettsiae in blood of dogs, and this may be an infrequent finding in the region (Wei et al, 2014).…”

Extensive genetic diversity of Rickettsiales bacteria in multiple mosquito species

“…In nature, Rickettsia bacteria are spread by either transstadial and transovarial (i.e. vertical) transmission in their arthropod hosts, or by horizontal (co-feeding) transmission through an infected vertebrate15172122. To date, although Anaplasma and Ehrlichia bacteria are passed transstadially in ticks, definitive evidence for transovarial transmission is not yet available314, such that vertebrates (e.g.…”

Spotted fever rickettsiae in wild-living rodents from south-western Poland

“…Rickettsia felis is mainly transmitted by cat flea, but other vectors have been reported in different parts of the world; in Europe, the reservoir of this bacteria is unknown [ 21 ]. Recently, intra- and interspecific transmission of R. felis between co-feeding arthropods (cat fleas transmitted the bacterium to naïve cat fleas and Oriental rat fleas via flea bite) on a vertebrate host was revealed [ 41 ]. Thus, the spreading of rickettsiae among different vectors and the demonstration of co-feeding transmission through a vertebrate host represents a novel transmission paradigm for Rickettsia spp.…”