Summertime Hazards

Ascaris can produce abdominal pain and discomfort, and may lead to malabsorption syndrome, weight loss, or vitamin deficiency. Very large infestations can sometimes lead to intestinal obstruction—I saw a case of this a few years ago, when I was working in Omaha, Neb. The parasite also can migrate to the bile duct and obstruct the liver.

With lower-level infestations, however, the nonspecific epigastric and diffuse abdominal discomfort may be indistinguishable from functional abdominal pain.

However, if the problem persists—or if the child has wheezing or pneumonia symptoms, get a complete blood count. If you see eosinophilia, order an ova and parasite stool exam.

▸ Dientamoeba fragilis. If you trained prior to the 1990s, you probably were taught that D. fragilis is merely a harmless commensal and doesn't need to be treated. However, it has become apparent in the last decade or so that this parasite can cause symptoms, including chronic loose stools, cramps, and flatulence. The child usually doesn't look especially ill but complains of abdominal upset and may have up to three to four loose, mucus-containing stools per day.

And D. fragilis hangs on—after the second week or so, you can be fairly certain it's not rotavirus or another acute gastrointestinal virus. Along with giardia, also think of D. fragilis.

Interestingly, D. fragilis will often piggyback with pinworms, literally sticking itself to the pinworm eggs. Therefore, if you've already treated the child for pinworms and the GI symptoms continue, you might want to order another ova and parasite stool exam. This time, however, special procedures are required. Because this organism is so fragile—hence the name—it deteriorates rapidly at room temperature. Parents should be instructed to collect a fresh stool sample and immediately place it in a preservative-containing pack (we use ParaPak). For the greatest sensitivity, three samples must be collected on separate days. Sensitivity of the test is about 85%–90% for three samples taken on consecutive days, and up to 95% if collected on alternate days.

The order to the lab should request a microscopic exam, not just an antigen screen. Microscopy will pick up not only D. fragilis, but other less common parasitic creatures that you don't want to miss, such as Entamoeba histolytica. Parents must also be told to stop any over-the-counter antidiarrheals such as Kaopectate or Pepto-Bismol 24–48 hours prior to the first stool collection, as these agents will make it difficult to visualize the parasites.

If D. fragilis is identified, treatment is metronidazole three times a day for 10 days. Because of fecal-oral transmission, consider asking the parents if they're experiencing loose stools as well. Symptoms tend not to be as dramatic in adults as in kids, but if they've got D. fragilis and you treat them, they often feel better.

▸ Blastocystis hominis. Although similar to D. fragilis in structure, B. hominis is still considered a commensal and not pathogenic. However, if present in high enough quantities, it can still cause nonspecific abdominal symptoms, loose stools, flatulence, and mucus in the stool. If you do a work-up and find no other explanation for the symptoms, it's not unreasonable to treat using the 10-day metronidazole regimen. Here, too, a microscopic exam is necessary to visualize the cysts in the stool.

Although not known to produce any toxins or direct irritants to the colon, it's possible that B. hominis just has not been investigated closely enough to prove its pathogenicity. New data suggest this may be the case.

We've been seeing more lab reports of both D. fragilis and B. hominis in the last few years. It's not clear whether that's because of increased use of preservative packs or actual increased prevalence.

But we definitely seem to get more calls from parents and physicians about parasites as the weather gets warmer.