Molecular Evidence of a Broad Range of Pathogenic Bacteria in Ctenocephalides spp.: Should We Re-Examine the Role of Fleas in the Transmission of Pathogens?

Georgios Dougas,Eleni Patsoula,Athanassios Tsakris,Stavroula Beleri,Maria Linou,Charalambos Billinis,Joseph Papaparaskevas

doi:10.3390/tropicalmed6010037

Abstract

The internal microbiome of common cat and dog fleas was studied for DNA evidence of pathogenic bacteria. Fleas were grouped in pools by parasitized animal. DNA was extracted and investigated with 16S metagenomics for medically relevant (MR) bacteria, based on the definitions of the International Statistical Classification of Diseases and Related Health Problems (WHO). The MR bacterial species totaled 40, were found in 60% of flea-pools (N = 100), and included Acinetobacter baumannii, Bacteroides fragilis, Clostridium perfringens, Enterococcus faecalis, E. mundtii, Fusobacterium nucleatum, Haemophilus aegyptius, Kingella kingae, Klebsiella pneumoniae, Leptotrichia buccalis, L. hofstadii, Moraxella lacunata, Pasteurella multocida, Propionibacterium acnes, P. propionicum, Proteus mirabilis, Pseudomonas aeruginosa, Rickettsia australis, R. hoogstraalii, Salmonella enterica, and various Bartonella, Staphylococcus, and Streptococcus species. B. henselae (p = 0.004) and B. clarridgeiae (p = 0.006) occurred more frequently in fleas from cats, whereas Rickettsia hoogstraalii (p = 0.031) and Propionibacterium acnes (p = 0.029) had a preference in fleas from stray animals. Most of the discovered MR species can form biofilm, and human exposure may theoretically occur through the flea-host interface. The fitness of these pathogenic bacteria to cause infection and the potential role of fleas in the transmission of a broad range of diseases should be further investigated.

Highlights

Fleas are obligate blood-sucking ectoparasites, with world-wide distribution
InIn thethe present study, we investigated the microbiome of fleas of collected from pet anipresent study, we investigated the microbiome fleas collected from pet mals in Attica, Greece, using metagenomics, with a special focus on pathogenic bacanimals in Attica, Greece, using 16S metagenomics, with a special focus on pathogenic teria
We examined the flea-human interface for possible transmission ways and laid down a hypothesis of a potential role of fleas as vectors of a broad range of pathways and laid down a hypothesis of a potential role of fleas as vectors of a broad range infectious agents

Summary

Introduction

Fleas are obligate blood-sucking ectoparasites, with world-wide distribution. Ctenocephalides felis and C. canis commonly parasitize cats and dogs and represent the most abundant flea species [1]. These flea species may feed on other mammals, including humans [2]. The skin of the host is penetrated by labrum, a sclerite stylet, and the laciniae, a pair of serrated saw-like mandibles. With anticoagulant properties, is injected in the host dermis through two canals running across each of the laciniae. Blood of the host is drawn and passed to esophagus, proventriculus, and stomach, where digestion takes place (Figure 1). Fleas deposit feces on the host which may fall off and spill over to the environment [3]

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Conclusion