close encounters with the environment

What’s Eating You? irritans COL Dirk M. Elston, MC, USA

Identifying Features nae, the head has only a single pair of All are characterized by laterally setae (hairs). It has no pleural rod, a compressed bodies and large hind legs. feature that differentiates it from Pulex irritans (Figure 1) lacks the cteni- Xenopsylla cheopis (oriental rat ). dia (combs) that lend the appearance Fleas show little host specificity. of a mustache (genal comb) and mane Although known as the human flea, of “hair” (pronotal comb) to and P irritans is a common flea on and fleas. It has a rounded frons (fore- . It is also found on wild head), which allows differentiation with no human contact.1 It can serve from the anteriorly flattened head of as the intermediate host of the dog the sticktight flea. Behind the anten- tapeworm (). P ir- ritans may serve as a vector for The opinions expressed are those of the author bubonic plague2,3 and erysipeloid. It and should not be construed as official or as may have played a major role in the representing those of the Army Medical Department, the United States Air Force, or the spread of plague during Europe’s great Department of Defense. epidemics. From Wilford Hall Air Force Medical Center, San P irritans is implicated in the spread Antonio, Texas. of diseases historically associated with REPRINT REQUESTS to the 59th Medical Wing, X cheopis. Like X cheopis, P irritans in- Dermatology Service/MMID, 2200 Bergquist Drive, Suite 1, Lackland Air Force Base, TX fests that harbor plague bacil- 4 78236-5300; or e-mail to [email protected]. lus. Although P irritans infests deer in

FIGURE 1. Human fleas carry disease and are common on dogs in parts of the southeastern United States.

VOLUME 66, SEPTEMBER 2000 175 PULEX IRRITANS

Lyme-endemic areas, fleas collected Treatment from infested deer do not contain spiro- Topical antipruritics containing cam- chetes. Therefore, it appears that fleas phor and menthol or pramoxine offer are not likely to transmit Lyme disease.5 some relief. Topical propylene glycol has Refugee populations are commonly been used as a counter-irritant. Ultrapo- infested with ectoparasites, including P tent topical steroids under occlusion may irritans.6 Ectoparasites create the poten- be needed for short-term treatment of se- tial for rapid spread of disease in these vere cases, although many cases will re- populations. P irritans persists as a “house spond to milder topical steroids. flea” in many parts of the world. Its im- portance as a plague vector is magnified REFERENCES by its resistance to pesticides.7 1. Patrick MJ, Harrison RL. Fleas on gray Fleas are prolific. A female human foxes in New Mexico. J Med Entomol. flea can lay more than 400 eggs in her 1995;32:201-204. lifetime. The ability of pupae and “co- 2. von Knorre G, Paasch S. Plague in central cooned” adults to lie dormant for a year Germany in the 17th century. Z Ges Inn or more can confound efforts at flea Med Grenzgeb. 1981;36:528-533. control. Lufenuron, an orally adminis- 3. Karimi Y, Farhang-Azad A. Pulex irritans, a tered growth regulator, has revolution- human flea in the plague infection focus in ized flea control. It does not kill adult General Mobutu Lake region (formerly fleas, but it does prevent reproduction. Lake Albert): epidemiologic significance. New topically applied agents, such as Bull WHO. 1974;50:564-565. fipronil, are also highly effective. These 4. Bakr ME, Morsy TA, Nassef NE, et al. Flea can be applied to the nape of the pet’s ectoparasites of commensal rodents in She- neck every 1 to 3 months. bin El Kom, Menoufia Governorate, Egypt. J Egypt Soc Parasitol. 1996;26(1):39-52. Adverse Reactions 5. Lane RS, Berger DM, Casher CE, et al. Ex- Flea bites appear as tense, pruritic, ur- perimental infection of Columbian black- ticarial papules on exposed areas includ- tailed deer with the Lyme disease spiro- ing the hands, forearms, and lower legs. chete. J Wildlife Dis. 1994;30:20-28. Excoriation with secondary impetiginiza- 6. Mumcuoglu KY, Miller J, Manor O, et al. tion is common. Vesicular and bullous The prevalence of ectoparasites in flea-bite reactions occur and can be quite Ethiopian immigrants. Israel J Med Sci. dramatic. Histologic examination reveals 1993;29:371-373. a wedge-shaped dermal infiltrate that sur- 7. Kilonzo BS, MaKundi RH, Mbise TJ. A rounds both venules and arterioles. decade of plague epidemiology and control Eosinophils are common. Epidermal in the western Usambera mountains, necrosis, spongiosis, and intraepidermal north-east Tanzania. Acta Tropica. or subepidermal bullae may be seen. 1992;50:323-329.

176 CUTIS®