Merging morphology, molecules and modelling: A unifying approach for understanding the common cat flea (Ctenocephalides felis) and related species worldwide

Abstract

The genus Ctenocephalides Stiles and Collins, 1930 contains the most ubiquitous and significant flea ectoparasites worldwide. The common cat flea Ctenocephalides felis (Bouché, 1835) is the most cosmopolitan species within the genus and invades human environments by infesting cats and dogs globally. This species causes significant dermatological pathology to pets and is a vector of zoonotic pathogens including Rickettsia felis, Bartonella spp. and the plague (Yersinia pestis) in endemic regions. Additionally, the costs to pet owners for annual flea control amounts to USD$15 billion worldwide. Despite the global medical, veterinary and economic significance of the cat flea, prior to this work little was known about its origins and how it came to be the most pervasive flea species on earth. The primary objective of this thesis was to amass a global collection of Ctenocephalides fleas from cats and dogs to fill the gaps in our knowledge relating to the taxonomy, phylogenetics and vector role of these important parasites. In this body of work, I demonstrate the importance of an integrated morphological and molecular approach for research on parasite and vector species. By marrying morphological taxonomy with molecular systematics and phylogeographic analyses, I resolve the taxonomy of C. felis and demonstrate cryptic diversity within the species that may have implications for zoonotic pathogen transmission. I show that from out-of-Africa origins, human movement and bioclimatic affinities define and conserve globally discrete lineages of C. felis. This work is the most comprehensive survey of global Ctenocephalides fleas thus far and the first to combine morphology with molecules for the analysis of the genus. The research provides a framework for the investigation of any unresolved taxa, particularly for globally distributed groups that impact upon human health, animal health, agriculture and global economics. The outcomes of this research make a significant contribution to the field of medical and veterinary entomology by providing taxonomic resolution of C. felis and by detailing the most effective and exhaustive technique for taxonomic inquiry of other medically or veterinary relevant arthropods. Using C. felis as a model, the work sheds light on the underlying mechanisms of evolutionary dispersal and population establishment of cosmopolitan insect species.