Our Guest Editor for this month's issue of Pediatric Annals, Thomas E. Frothingham, MD, Professor of Pediatrics at Duke Universky Medical Center, has provided us with information about parasitic diseases in children in the United States, including an overview and articles on febrile illnesses, eosinophilia, diarrhea, central nervous system infections, and skin infestations caused by parasites. Parasitoses in pediatric practice has become increasingly prevalent for the following reasons:
* the legal and illegal immigration of large numbers of persons from Southeast Asia, Mexico, Central and South America, and the Caribbean - included among these are legally adopted infants and children,
* travel by 10 to 15 million US citizens (including children) to foreign countries each year, more than half of which are endemic for parasitic diseases,1
* the marked increase in the number of children attending day-care centers where they are exposed to a variety of parasites, particularly pinworms and Giardia lamblia, and
* the rise in the number of immunocompromised patients, including those who have acquired immunodeficiency syndrome (AIDS), who are subject to infection by several opportunistic parasites, particularly Pneumocystis carinii.
While not affecting the actual prevalence of parasitic diseases, improved diagnostic methods have increased their recognized prevalence.
The parasitoses extract a heavy toll on the world's population of 5.7 billion people. It is estimated that the number of persons afflicted include 1 billion who have ascariasis, 800 million who have trichuriasis, 566 million who have amebiasis, 490 million who have malaria, and 200 million each who have giardiasis and schistosomiasis. The three leading killers among parasites are malaria (2.5 million annually), schistosomiasis (1 million), and amebiasis (110 000 ).2
When I was a medical student, our curriculum included two full- term parasitology courses. Parasitology was one of my favorite subjects because it seemed to be an exact science, one for which we knew the etiology of the diseases, the life cycles of the parasites and their means of transmission to humans, the signs and symptoms of the diseases they caused, and the specific treatment that was recommended at the time. It also presented an abundance of exotic names (invoking visions of faraway places) that, once mastered, rolled off the tongue with ease and pleasure. Examples of my favorite names are: Trypanosoma brucei gambiense, a hemoflagellate that causes African sleeping sickness and is transmitted to humans by the tsetse fly; Leishmania tropica, another hemoflagellate that causes cutaneous leishmaniasis, also known as oriental sore and Baghdad boil; Leishmania donovani donovard, which causes visceral leishmaniasis, widely known by its Indian name kala-azar, which means black fever in reference to its causing darkening of the skin and high fever; Fasciolopsis busld, a trematode (the giant intestinal fluke) found in Asia and acquired by humans who eat raw freshwater vegetation such as bamboo shoots, water chestnuts, and caltrops, one of which is called Chinese red*watei caltrop (what a name!); Paragonimi« westermani, another trematode (the lung fluke) acquired by humans who eat raw or insufficiently cooked crayfish or freshwater crabs; Diphyllobothrium iatum, a cestode (the fish tapeworm) acquired by humans who eat raw or insufficiently cooked fish that selectively absorbs vitamin B- 12 from its host's intestinal tract, causing anemia; Ascaris lumbricoides, an intestinal nematode of which individual human intestines may harbor hundreds or as many as a thousand at one time, a worldwide burden so enormous that if all of these worms were placed head to tail, they would encircle our planet 50 times3; Wuchereria bancrofti and Loa loa, the tissue-dwelling nematodes that cause elephantiasis and African eye worm disease, respectively; and finally, Capiliaria philippinensis, another intestinal nematode that does not have much to distinguish it among other parasitic exotica except for its name, which contains 6 "i"s, 4 Vs1 3 "a"s, 3 Ts1 2 Vs, and 2 Vs, plus a "c," an "e," an "h," and an V - tough to beat in any phylum.
Despite learning these names and the diseases they cause, along with many, many more, I encountered only a few parasitic infections in practice. Those . included the ubiquitous Enterobius vermicularis (pinworm), which infects just about everyone at some time if one wants to look for them, G lamblia (only recently present in the United States), Trichuris trichiura (whip worm), A lumbricoides, Entamoeba coli, Toxoplasma gondii, Toxocara cards (visceral larva migrans), Pediculus capias and humanas and Phthirus pubis (lice), Sarcoptes scabiei (scabies), and Tric/iomoruzs hominis. Practicing in upstate New York, one would not expect to encounter many others until recently, for the reasons noted above. This recent increased expectation is particularly pertinent for those who practice in cities and states where immigration of persons from foreign countries endemic for parasitic diseases is high.
Today, medical students are exposed to much less in the way of lectures about the parasitoses than they were in my day; at the University of Rochester School of Medicine and Dentistry, for example, they receive 10 hours of such presentations, probably enough to prepare them for the 2% of questions directed to the parasitoses on the National Board of Medical Examiners' tests. Ten hours doesn't seem enough, given the increasing number of parasitic diseases practitioners can expect to encounter today and in the years ahead.
In his overview of parasitic diseases in children in the United States in this issue of Pédiatrie Armais, Richards lists four protozoan and seven helminthic pathogenic parasites that were found in 216 275 stools examined in 49 US state public health laboratories in 1987.4 Actually, there were 8 protozoan and 15 helminthic pathogenic organisms that were identified, albeit many were identified less often than those listed by Richards.5 While these data give us some idea of the prevalence of parasitic diseases present at that time, they are incomplete because many, many more patients were diagnosed in local hospital laboratories, rather than in state public health laboratories. Further, 7 years have gone by since that study was undertaken, and again, we can expect that the detected prevalence of those diseases and perhaps others has risen in the United States.
The 1994 Red Book (Report of the American Academy of Pediatrics' Committee on Infectious Diseases) describes 27 parasitic diseases briefly, including clinical manifestations, epidemiology, diagnostic tests, treatment, isolation of hospitalized patients, and control measures.6 Eight more are described more briefly in a table. The 1994 Red Book also has reproduced from the December 10, 1993, issue of the Medical Letter on Drugs and Therapeutics recommendations for the treatment of infections by 84 parasites. Thus, most practicing pediatricians have on hand a ready reference about the parasitoses that occur in the United States and worldwide. More detailed information can be gained from textbooks on parasitology.2'7 Those who choose to peruse them will find their contents fascinating.
1. Adler MB, ChLsholm B. Health promotion and disease prevention foi lhe international traveler. NUTSÍ Proa. 1991; 16: i0-25.
2. Markell EK, Voge M, John DT. Medicai Parasealagy. 7th ed. Phibdeiphia, Pa: WB Saunders Co; 199Z.
3. Ascariasis. Lancet. 1989; 1:99 7 -998. Editorial.
4. Richards FO Jr. An overview of parasitic diseases in children in the United States: What's old! What's new; Where's help? Pedían Ann. l994;23:392-397.
5. Kappus KK. J urne k DQ Roberts JM. Results of testing for intestinal parasites by siate diagnostic laboratories. United States. 19S7. MMATi. i99l;40:25-45.
6. Committee on Infectious Diseases. 1994 Bed Book. Elk Grove Village, 111: American Academy of Pediatrics; 1994.
7. Garcia LS, Bruckner DA. Diagnotor Medical Parasitology. Washington, DC: American Society for Microbiology; 1993.