The cat flea

The cat flea, Ctenocephalides felis, is the most common flea species. Its primary host is the domestic cat, but the it is also the primary flea infesting dogs. Humans can be bitten but this flea species was never able to build a stable long-term population that subsequently infested other people. Cat fleas can transmit other parasites and infections but pet owners are spending millions of dollars annually on flea control products because fleas cause up to 50% of all dermatological cases of cats and dogs .

Within Ctenocephalides felis many scientists have distinguished four subspecies based on morphology, however a recent revision suggested that two of those likely represent species. Differentiation of the subspecies based on minute morphological differences (e.g. chetotaxy, phallosome morphology and cephalic curvature) coupled with the encroachment of Ctenocephalides felis felis into other subspecies-specific geographical regions has led to assumptions of interbreeding between subspecies, making differentiation even more complex if not impossible. 

In a new study a group of Australian researchers investigated the genetic identity of Ctenocephalides felis and determined the diversity of cat fleas from Australia, Fiji, Thailand and the Seychelles using DNA Barcoding and another mtDNA marker (COII). They now recognized two putative species within Ctenocephalides felis (Ctenocephalides felis and Ctenocephalides orientis). As I have stated before I am not a strong believer in subspecies and I am somewhat puzzled that four subspecies have been maintained for a very long time despite very weak evidence. However, it does seem that the consequent inclusion of molecular data will help to sort out this rather old problem. Interestingly one of the main conclusions of this study is that it is intriguing to realize that we know essentially nothing about the population structure of Ctenocephalides feli elsewhere (but Australia) in spite of its global importance.