Some people suffer more from flea bites, these can cause intense itching often resulting in secondary infection. The usual flea bite has a small red spot where the flea has inserted its mouthparts. Around the spot there is a red halo with very little swelling. Many people do not react to flea bites at all while others are sensitive and suffer severe allergic reactions.
Two species of fleas, the stickbight flea and the sand flea [Tunga penetrans] penetrate the skin of the host and embed prior to egg deposition. The sand flea burrows into the soft skin of the feet of man. Intense itching accompanies the growth of the pregnant flea to pea-size. Itching and irritation may lead to secondary infections, and a number of deaths have occurred from gas gangrene and tetanus. The stickbight flea is similar to the sand flea, but attacks the heads of poultry, cats, and dogs. Certain fleas that primarily feed on rodents and birds will, if need be, attack man, as when hungry oriental rat fleas [Xenopsylla cheopis] abandon their hosts dying of bubonic plague, thereby transmitting the plague bacillus to man. Other species of fleas, such as [Xenopsylla brasiliensis] and [Nosopsyllus fasciatus], also transmit plague, and are widespread among rodents and small mammals. Natural infection among animals with the plague cacillus has been demonstrated in more than 90 species of fleas, representing 45 genera and 9 families. Fleas are believed to be the principal vectors of murine typhus to man from rats and mice; of various enzootic infections among animals, including tularaemia and Russian spring-summer encephalitis; of myxomatosis, a virus disease of rabbits; of a filorial worm of dogs; and of a common tapeworm [Diplyidium caninum] of dog, cats and, occasionally, children.