It’s “summertime and the livin’ is easy” according to the lyric from an old George Gershwin song. But sometimes, summer activities can lead to illnesses that can disrupt a child’s easy living.
Case: An otherwise healthy 11-year-old presents with four to five loose stools per day, mild nausea, excess flatulence, and cramps for 12 days with a 5-pound weight loss. His loose-to-mushy stools have no blood or mucous but smell worse than usual. He has had no fever, vomiting, rashes, or joint symptoms. A month ago, he went hiking/camping on the Appalachian Trail, drank boiled stream water. and slept in a common-use semi-enclosed shelter. He waded through streams and shared “Trail Magic” (soft drinks being cooled in a fresh mountain stream). Two other campers report similar symptoms.
Dr. Christopher J. Harrison
Differential diagnosis: Broadly, we should consider bacteria, viruses, and parasites. But generally, bacteria are likely to produce more systemic symptoms and usually do not last 12 days. That said, this could be Clostridioides difficile, yet that seems unlikely because he is otherwise healthy and has no apparent risk factors. Salmonella spp., Campylobacter spp. and some Escherichia coli infections may drag on for more than a week but the lack of systemic symptoms or blood/mucous lowers the likelihood. Viral agents (rotavirus, norovirus, adenovirus, astrovirus, calicivirus, or sapovirus) seem unlikely because of the long symptom duration and the child’s preteen age.
The history and presentation seem more likely attributable to a parasite. Uncommonly detected protozoa include Microsporidium (mostly Enterocytozoon bieneusi) and amoeba. Microsporidium is very rare and seen mostly in immune compromised hosts, for example, those living with HIV. Amebiasis occurs mostly after travel to endemic areas, and stools usually contain blood or mucous. Some roundworm or tapeworm infestations cause abdominal pain and abnormal stools, but the usual exposures are absent. Giardia spp., Cryptosporidium spp., Cyclospora cayetanensis, and/or Cystoisospora belli best fit this presentation given his hiking/camping trip.
Workup. Laboratory testing of stool is warranted (because of weight loss and persistent diarrhea) despite a lack of systemic signs. Initially, bacterial culture, C. difficile testing, and viral testing seem unwarranted. The best initial approach, given our most likely suspects, is protozoan/parasite testing.
The Centers for Disease Control and Prevention recommends testing up to three stools collected on separate days.1 Initially, stool testing for giardia and cryptosporidium antigens by EIA assays could be done as a point-of-care test. Such antigen tests are often the first step because of their ease of use, relatively low expense, reasonably high sensitivity and specificity, and rapid turnaround (as little as 1 hour). Alternatively, direct examination of three stools for ova and parasites (O&P) and acid-fast stain or direct fluorescent antibody testing can usually detect our main suspects (giardia, cryptosporidium, cyclospora, and cystoisospora) along with other less likely parasites.
Some laboratories, however, use syndromic stool testing approaches (multiplex nucleic acid panels) that detect over 20 different bacteria, viruses, and select parasites. Multiplex testing has yielded increased detection rates, compared with microscopic examination alone in some settings. Further, they also share ease-of-use and rapid turnaround times with parasite antigen assays while requiring less hands-on time by laboratory personnel, compared with direct microscopic examination. However, multiplex assays are expensive and more readily detect commensal organisms, so they are not necessarily the ideal test in all diarrheal illnesses.