Cyclospora is a protozoan pathogen linked clinically to acute, chronic diarrhea. Infection with the parasite is referred to as Cyclosporiasis. It was not until 1977 and 1978 that the first three diagnosed cases of Cyclospora were reported, though at the time they did not know what they had identified. It was not until the next year, in 1979, that scientist R.W. Arthur would identify Cyclospora for what it was, a parasite.
At the time, Dr. Arthur was working as a scientist in Papua New Guinea when he discovered the parasite and that it was transmitted through feces. He also noted that the oocysts (the organism shed by the infected person or animal) was immature and did not immediately infect others at the time it was ingested. He also noted how difficult identification of an infected person would be because the unsporulated oocysts looked like fungus spores under close observation. To this day, identification of Cyclospora requires a pathogen-specific test that is often not performed, and a number of false negatives can occur even in a person who has a acute Cyclospora illness.
Today we know that Cyclospora is endemic not only to Papua New Guinea, but to Peru, Guatemala, Honduras, Mexico and other Latin America countries. It is not endemic to the United States or Canada, which i s why practitioners often fail to properly diagnose victims of Cyclosporiasis. As such, it has traditionally been called the travelling disease, or travelers’ diarrhea, by many doctors since only those who travel seem to get the disease. Since it has become the subject of more research (mostly since 1990), however, and since more and more cases are appearing in the U.S. due to the large amount of imported food, practitioners are more often aware of Cyclospora and test for it.
Most Outbreaks of Cyclospora Linked to Imported Food
Cyclospora outbreaks have become common with the large amount of imported foods, many which come from Mexico and Central America. Cyclospora is now a common source of pathogenic outbreak in the Unites States, with one or more outbreak sin most recent calendar years. By 2017, Cyclospora had become a routine finding by health agencies and epidemiologists among people who had no international travel, with numerous large-scale outbreaks linked to cilantro, lettuce, and other fruits and vegetables. Ironically, the shipping process allows the unsporulated oocysts to mature allowing for infection after ingestion within days or a couple of weeks.
The Cyclospora parasite requires time (days to weeks) after being passed in a bowel movement to become contagious to other humans, which makes human to human direct infection difficult. Instead, the parasite contaminates food or water and is then consumed, thereafter with an incubation period of days to weeks it presents with a prolonged illness, often noted by the ebb and flow (recurrence) of acute symptoms for 100 days or more. According to the CDC, “the period between becoming infected and becoming sick is usually around 1 week. Cyclospora infects the small intestine (bowel) and usually causes watery diarrhea, with frequent, sometimes explosive, bowel movements. Other common symptoms include loss of appetite, weight loss, gut cramps/pain, bloating, increased gas, nausea, and tiredness. Vomiting, body aches, fever, headache, and other flu-like symptoms might be noted. Some men and women that are infected with Cyclospora don’t have any signs.” Symptoms may include:
According to the CDC, “health care providers must think about a diagnosis of cyclosporiasis in patients with protracted or remitting-relapsing diarrheal illness.” But because most U.S. laboratories do not test for Cyclospora, even if stool is analyzed for parasites, the CDC has noted that healthcare professionals need to specifically arrange testing for Cyclospora – a Cyclospora screen. Testing can be performed via ova and parasite examination, using molecular approaches, or via a gastrointestinal pathogen panel evaluation.
Since Cyclosporiasis is a nationally notifiable disease, healthcare professionals must report suspected and confirmed cases of disease to public health jurisdictions.
Cyclospora is not a bacteria, but in 1995 while conducting research in Nepal, in a double-blind, placebo-controlled trial researchers found that trimethoprim-sulfamethoxazole (TMP-SMZ) was effective in treating the illness – TMP-SMZ, or Bactrim by its brand name, is highly effective in cutting the disease short. Unfortunately, some people are allergic to sulfa-based antibiotics, and must rely on largely inefficient and ineffective secondary protocols.
Individuals with symptoms linked to Cyclospora should contact their healthcare provider for treatment immediately. In many of the recent cases of a large Cyclospora outbreak, the victims have found out their likely diagnosis on television before they presented for a Cyclospora test. Many had been in and out of their physician’s offices without satisfaction, often with negative stool cultures leaving both the victim and the medical professional wondering about the etiology of the disease. But in several recent outbreaks, such as the recent Del Monte vegetable tray outbreak, the McDonald’s Southwest Grilled Chicken Salad outbreak, and the previous Olive Garden/Red Lobster salad outbreak, news coverage put many victims on notice and they presented to their physicians’ offices for testing.
Many of the victims were sick for weeks or months prior to finding out they had Cyclospora. Many were extremely worried given the severity of their illness, the attendant weight loss, with thoughts this could be cancer or another terminal illness.
 Ashford RW. Occurrence of an undescribed coccidian in man in Papua New Guinea. Ann Trop Med Parasitol. 1979;73:497–5; Ortega YR, Sterling CR, Gilman RH, Cama VA, Diaz F. Cyclospora species: a new protozoan pathogen of humans. N Engl J Med. 1993;328:1308–1312; Ortega YR, Gilman RH, Sterling CR. A new coccidian parasite (Apicomplexa: Eimeriidae) from humans. J Parasitol. 1994;80:625–629; Ortega YR, Sanchez R. Update on Cyclospora cayetanensis, a food-borne and waterborne parasite. Clin Microbiol Rev. 2010;23:218–234.
 Larry Strausbaugh, et. al., Cyclospora cayetanensis: A Review, Focusing on the Outbreaks of Cyclosporiasis in the 1990s, Clinical Infectious Diseases, Volume 31, Issue 4, October 2000, Pages 1040–105.
 Hoge CW, Shlim DR, Ghimire M, et al. Placebo-controlled trial of co-trimoxazole for cyclospora infections among travellers and foreign residents in Nepal, Lancet, 1995, vol. 345 (pg. 691-3).