Whether you're a dog, a cat, or a grad student who hasn't been home to shower for a few days, fleas are a major problem. They make skin itch. And NOTHING is worse than itchy skin.
Do you know WHERE the fleas are? Where they like to hang out and guard their little flea eggs? Where's the best place for a flea to get a decent night's sleep, or a delicious snack? These are important questions. Lucky for us, Hsu, Hsu, and Wu of the Department of Entomology at National Taiwan University have the answers. And this paper, dear readers, is pure blogging GOLD.
Now, if you wanted to find out what areas of the cat body fleas prefer to call home, you might think that you could just drive around and look for dead cats (as long as they haven't been dead for too long), and assess the infestation. But you'd be wrong, because although cat fleas almost NEVER leave their host cats - even when the flea population on one cat exceeds 300 individuals - as soon as it becomes clear that the cat is beginning to die, they pack their bags and take off, and begin the nomadic search for a new cat. You might also think that you could try to get cat owners to bring their pet cats in to your lab, but there's a problem there too: most cat owners (at least, the responsible ones) give their cats anti-flea treatments and keep them groomed and bathed, which means that pet cats wouldn't have that many fleas. By now, you might expect that you know the answer: trap living stray cats, bring them to the lab, assess the infestation, and then return the stray cat to the location where it was caught in the first place.
Stray cats were live trapped in cat traps that had a single door and that were baited with fried chicken.
Each night of animal trapping, from January through December of 1991, some poor grad student went out into the streets of Taipei, and set up a handful of the fried-chicken-containing cat traps near "garbage-gathering sites." In the morning, the dutiful grad student would return to retrieve the trapped cats and cat traps (presumably minus the chicken), and return to the lab. Back at the lab, the cat would be anesthetized to allow for flea removal.
Fleas were removed (with bare hands) from six randomly chosen minor areas (belonging to three major areas) of the animal surface pelage by quickly parting the cat's fur.
(In case you were wondering, a "pelage" is a "growth of hair or wool or fur covering the body of an animal.")
So the researchers, with their bare hands (really? REALLY? not even latex gloves?) removed a total of 3,382 fleas from each of the 164 cats (of 200 caught) that had fleas. Each flea was preserved in vials of an alcohol solution and labeled for further analysis. All 3,382 fleas were the same species (Ctenocephalides felis). The cat with the most fleas was host to 161 critters.
Among the major areas, the highest percentage (45.89%) of fleas was located on the head and neck (region A), which was the smallest region in terms of surface area. The lowest percentage (22.80%) of fleas was located on the cat's underside (region C). The highest density of fleas was found in the neck area (region A2). The lowest percentage, among minor areas, were the legs and tail (region B2), at only 6.72%.
Why would it be that the fleas were so particularly fond of cat necks? Well, the cat grooms most of its body with its tongue and its teeth. Simply stated, the cat can't use its tongue and teeth to groom its head and neck. While cats do groom the head and neck by scratching with claws, this is not nearly as effective for flea removal, compared with licking and biting. Further, for every fifty minutes that a cat spends grooming by licking and biting, it spends only one minute grooming by scratching. (And, if you were wondering, cats spend about 10% of their waking hours engaged in grooming behaviors.) So, simply based on the grooming behaviors of the cat, you would expect the most fleas to be found around the hardest-to-groom places, which are the head and neck. To add a layer of complexity, the grooming behavior of the host animal is probably the most intensive selection pressure for parasites. It may be that the cat flea is so well-adapted to life on cats that it has an evolved preference for the hardest-to-groom areas. It is also possible, however, that other factors are involved, such as the differences in the skin temperature of the cat in different regions, for example.
Regardless of the reason that fleas like to party on the necks of cats, this research has important implications for the control of fleas on pet cats. While cats appear to be able to control the flea infestation for most of the surface of their bodies, they can probably use some help when it comes to the head and neck. Extra manual grooming and cleaning of those areas by the owners is probably useful, as are special anti-flea collars.
If you remember only one thing from this blog post, remember this: you catch more flies with honey than with vinegar, but to catch a cat, you need to fry a chicken.
Hsu MH, Hsu TC, & Wu WJ (2002). Distribution of cat fleas (Siphonaptera: Pulicidae) on the cat. Journal of medical entomology, 39 (4), 685-8 PMID: 12144305