Tiny Parasite, Big Problem: Managing Cyclosporiasis in Pediatric Patients

Cyclosporiasis is an intestinal infection caused by the parasite Cyclospora cayetanensis. Transmission of Cyclospora occurs through the ingestion of food or water contaminated with the parasite, which is shed through the feces of infected individuals. Once shed, Cyclospora oocysts require 1 to 2 weeks to become infectious—this limits the likelihood of direct person-to-person transmission but makes contact tracing particularly difficult during disease outbreaks.¹

Although not endemic to the United States, epidemiologic surveillance data indicates a current outbreak of cyclosporiasis in the United States. This outbreak, which has been largely linked to contaminated iceberg lettuce from central Mexico, has resulted in a substantial increase in documented cyclosporiasis cases across the country. Since May 1, 2026, nearly 14,000 laboratory-confirmed cases have been reported to the CDC, which significantly surpasses the 1100 cases reported during the same time period last year.² Given the current outbreak status, it is important for health care providers across the continuum of care, particularly those practicing in the community, to be prepared to advise patients on the management of this infection.

Because cyclosporiasis predominantly presents as gastrointestinal distress with watery diarrhea being a hallmark symptom, aggressive rehydration is the cornerstone of management. The infection is typically considered self-limiting; however, antibiotics targeting Cyclospora—namely sulfamethoxazole-trimethoprim—may be prescribed for patients with severe, persistent symptoms at the discretion of their health care provider.³

Although this management approach is generally consistent across age groups, careful consideration should be taken in the context of pediatric patients as their physiologic differences can significantly impact both disease progression and medication selection, with the latter putting them at 3 times the risk of experiencing a medication error.⁴

Oral Rehydration

When considering acute gastrointestinal illnesses, pediatric patients, particularly those who are younger, are at an increased risk for dehydration. This is due to their higher baseline total body water proportion, larger body surface area relevant to size, and increased insensible losses. Additionally, pediatric patients are more likely to ignore thirst cues than adults, as well as rely on parent or caregiver intervention to appropriately maintain hydration when sick.⁵ These factors contribute to an increased likelihood to progress to severe dehydration, with more than 200,000 hospitalizations occurring annually in the United States in young children alone.⁵

This makes oral rehydration particularly important for pediatric patients experiencing diarrheal illnesses such as cyclosporiasis. Oral rehydration solutions (ORS), such as Enfalyte (Mead Johnson Nutrition) or Pedialyte (Abbott Laboratories), are preferred due to their balance of water, glucose, and electrolytes that maximizes fluid absorption. Children with mild to moderate dehydration are rehydrated using weight-based replacement.⁶ For infants and children, 50 to 100 mL/kg of ORS should be given over 3 to 4 hours, with an additional replacement dose given for each diarrhea episode.

Replacement doses differ based on patient weight. Patients weighing less than 10 kg should be repleted with 60 to 120 mL per episode, up to 500 mL a day, whereas patients over 10 kg should be repleted with 120 to 240 mL per episode, up to 1 L a day. In adolescents weighing 30 kg or more, 2 to 4 L of ORS can be provided, with additional replacement for each diarrhea episode provided as needed up to 2 additional liters per day.⁷

Children with severe dehydration that present with altered mental status, persistent vomiting, or inability to maintain oral intake should seek further medical evaluation.

Antidiarrheals

Given the presentation of cyclosporiasis, parents and caregivers may request information regarding the use of antidiarrheals to combat symptoms. It is important to consider that antidiarrheals are generally not recommended in children unless specifically directed by a health care professional. Additionally, in the context of infection-related gastrointestinal illness, antidiarrheals may be further contraindicated as they may interfere with the body’s ability to eliminate infectious organisms or their toxins.⁷ Cyclosporiasis is a prime example since oocysts are released through the feces; therefore, during the current outbreak patients and caregivers should be counseled not to administer over the counter (OTC) antidiarrheal products to a child initially presenting with diarrhea until cyclosporiasis is ruled out.

Common OTC antidiarrheal products additionally have age-related exclusions for use in the pediatric patient population. For example, loperamide (Imodium; Kenvue) is generally not recommended in patients younger than 6 years of age due to an increased risk of potentially fatal ileus. This risk is especially pronounced in children younger than 3 years of age, a population in which use is strongly recommended to be avoided.⁸

Another common OTC antidiarrheal is bismuth subsalicylate (Pepto Bismol; Procter & Gamble). Bismuth subsalicylate, as well as other salicylates, should be avoided in children and teenagers—particularly those recovering from viral illnesses—due to an increased risk of Reye syndrome, which is characterized by behavioral changes, nausea, and vomiting which can progress to acute encephalopathy and hepatic dysfunction. The incidence of Reye syndrome is overall low, but the potential severity makes avoiding salicylates an important pediatric safety consideration.⁸ Of note, the manufacturer does offer a Pepto Bismol Kids product, however the active ingredient in this formulation is calcium carbonate instead of bismuth subsalicylate, making it an age-appropriate choice for children suffering from other gastrointestinal symptoms such as acid reflux.

Because OTC products generally may have different age restrictions depending on their active ingredients and formulations, caregivers should be encouraged to check product labeling and consult their pharmacist before administering an antidiarrheal medication to their child.

Antibiotic Treatment

Sulfamethoxazole-trimethoprim (Bactrim, Septra) is the first-line treatment for severe or persistent cyclosporiasis. In patients aged at least 2 months to 18 years of age, sulfamethoxazole-trimethoprim is prescribed as 8 to 10 mg/kg per day in 2 divided doses and given orally for 7 to 10 days.³

It is important to note that sulfamethoxazole-trimethoprim is contraindicated in infants younger than 2 months of age.⁹ The labeling restriction is related to the potential to cause serious adverse effects in very young infants, particularly kernicterus. Sulfonamides such as sulfamethoxazole can cause significant bilirubin displacement. Because neonates have increased blood-brain barrier permeability, high levels of unconjugated bilirubin promote passive diffusion across the blood-brain barrier. This contributes to kernicterus, which can lead to long term hearing loss, visual abnormalities, extrapyramidal symptoms, and negative impacts on dentition.

Conclusion

Cyclosporiasis is an important cause of prolonged diarrhea that should be considered in pediatric patients, particularly during national outbreaks. Caregivers should avoid independently administering OTC antidiarrheals unless directed by a healthcare professional as this can negatively impact the clearance of the parasite. Additionally, OTC antidiarrheal products, such as loperamide and salicylate-containing products, require special caution in children. Oral rehydration is instead the mainstay of treatment and should be calculated according to the child's weight and clinical status. Sulfamethoxazole-trimethoprim therapy can be prescribed and requires careful consideration of age, weight, contraindications, and appropriate dosing when used in neonates and young infants.

Recognizing these considerations allows pharmacists and other health care professionals to provide safer, more individualized care for children with cyclosporiasis while reducing the risk of medication-related harm.

REFERENCES

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9. Bactrim (sulfamethoxazole and trimethoprim). [package insert]. FDA. Updated May 2021. Accessed August 17, 2026. https://www.accessdata.fda.gov/drugsatfda_docs/label/2021/018374s028lbl.pdf