Rising Cases of Cyclosporiasis This Summer

If you’ve been battling a persistent stomach illness, it might be something called cyclosporiasis, a parasitic infection that can lead to weeks of severe diarrhea, cramps, and bloating.

This particular infection usually peaks during the summer, but reports from various states indicate a rise in cases that is unusual for this time of year.

In Michigan, for example, health officials typically see around 50 cases of cyclosporiasis every year, but since June 22, they’ve reported a staggering 681 cases, suggesting a widespread outbreak stemming from a common source. Nearby states are also experiencing unusual increases in case numbers.

Ohio has noted 177 reported cases just this year, with a significant spike to 171 occurring in June alone, primarily after June 20.

Meanwhile, New York state has recorded 112 cases outside of New York City, with 107 of those reported since May 1.

Other states have reported infections too, but it remains unclear if they are connected.

Investigations are in progress to determine the cause of these outbreaks in Michigan and Ohio and perhaps other states, though it seems like it could take some time to find answers.

Dr. Max Teplitski, a former head of the Division of Food Safety at the USDA and now a chief science officer with the International Fresh Produce Association, noted that tracing cyclosporiasis back to a specific source is particularly challenging.

Teplitski recently co-led an FDA advisory committee aimed at understanding why cyclospora outbreaks have been increasingly frequent in the U.S. in recent years.

“Cyclospora is a strange one,” he remarked.

With some foodborne pathogens like E. coli and Salmonella, researchers can sequence their DNA to find a match between the strain causing illness and the one found in contaminated food or water. This genetic tracking is crucial for identifying outbreaks.

There’s a national surveillance program called PulseNet that continuously analyzes bacterial DNA to compare cases in real-time. When similar genetic traits emerge across various cases in different states, that suggests a shared source might be at play.

But cyclospora doesn’t behave like that.

Teplitski explained that, unlike some bacteria, cyclospora undergoes complex reproduction that makes tracking its lineage nearly impossible. The parasite has both male and female forms that exchange genetic material, leading to genetic variability from one generation to the next.

Without the benefit of molecular testing, piecing together an outbreak relies heavily on the painstaking work of epidemiologists who trace each confirmed case of infection, asking detailed questions about the individuals’ recent food and activity history. This process can be tedious since people often struggle to recall what they consumed several days prior. To aid in their investigations, they sometimes delve into grocery receipts or credit card statements.

While these interviews typically focus on food consumption, experts like Teplitski hope investigators will also consider potential water sources, such as lakes and water parks, where exposure could occur.

“It’s crucial to explore all angles,” he emphasized.

Cyclosporiasis is spread via human feces, and people typically contract the parasite by consuming contaminated food or water, particularly raw produce or while swimming.

Common sources include hard-to-wash items like berries and herbs, alongside recreational water locations such as pools and lakes.

Since the mid-1990s, the foods most frequently linked with outbreaks include:

• Raspberries: 12 outbreaks
• Basil: 11 outbreaks
• Salad mixes: 8 outbreaks
• Cilantro: 6 outbreaks
• Berry mixes: 6 outbreaks
• Lettuce: 2 outbreaks
• Snap peas: 2 outbreaks

Post-ingestion, the parasite begins its lifecycle in the intestines, where it separates into male and female forms, reproduces, and eventually destroys intestinal cells before being expelled from the body.

Once in the environment, the parasite matures over weeks, becoming ready to infect a new host. This maturation process means people typically don’t spread it directly to those nearby, as transmission tends to be more indirect.

Symptoms from a cyclospora infection present differently than those caused by Salmonella or E. coli, according to Dr. Rebecca Schein from Michigan State University Health Sciences. Although some may have a fever, it’s not common.

“Most people experience very watery diarrhea, often more than three times a day, coupled with a feeling of bloating and discomfort that can last for weeks,” she explained. “You might feel like you just ate a heavy Thanksgiving meal, but every day.”

This stomach bug can linger even in otherwise healthy individuals. “For those with a normal immune system, it may eventually fade away, but it could take up to six weeks,” said Schein, noting that symptoms may wax and wane during that time.

Individuals with compromised immune systems may find their symptoms persist without treatment.

“In such cases, the symptoms won’t disappear until they receive medical intervention,” she added.

Generally, when seeking the cause of a stomach ailment, doctors will often check for various pathogens in a patient’s stool using multiplex tests. Unfortunately, cyclospora isn’t included in those panels.

“It’s easy to overlook if the proper tests aren’t administered, which complicates matters,” Schein noted. Correct diagnosis requires a specific test that uses a special staining method to highlight the parasite’s eggs under a microscope, turning them pink or orange.

This past May, the Texas health department issued a health advisory urging that doctors may need to conduct up to three tests over a 24-hour period to confirm a diagnosis due to the sporadic nature of egg shedding.

Once diagnosed, treatment is generally straightforward. The standard approach involves a combination of antibiotics known as trimethoprim-sulfa, commonly marketed as Bactrim or Septra, typically administered for seven to ten days, though patients with weakened immunity might require longer treatment.

Schein explained that this antibiotic works by disrupting the parasite’s ability to utilize folate, a vitamin essential for its energy production.

If someone experiences diarrhea lasting longer than three to five days—or two days in areas near known outbreaks—it’s crucial they seek testing.

“It’s advisable to treat cyclosporiasis because, aside from the discomfort, the infection can persist and potentially spread in the environment if untreated,” Schein cautioned.

Researchers in Norway conducted a study in 2021, intentionally contaminating berries with multiple parasites, including cyclospora, to evaluate the effectiveness of various washing methods.

Their methods included running water over the berries for one minute, using a salad spinner with water, and immersing them in a vinegar solution for a minute. They discovered that cleaning blueberries was notably easier than raspberries, explaining the frequent association of the latter with outbreaks.

Interestingly, cyclospora appeared to cling to raspberries more tenaciously compared to other parasites tested. The vinegar rinse proved slightly more effective than plain water, but overall, no method provided a foolproof solution against the bacteria.

In essence, washing your produce remains a vital practice to eliminate potential contaminants before they enter your kitchen.

The FDA offers some handy guidelines for cleaning fresh fruits and vegetables:

• Wash hands thoroughly for 20 seconds with warm soap and water both before and after handling produce.
• If the produce is damaged, cut away the affected areas before use.
• Rinse all produce before peeling to prevent surface dirt from transferring onto the clean parts.
• Gently rub produce under running water; there’s no need for soap.
• Use a clean vegetable brush for firm produce like melons.
• Dry fruits and vegetables with a clean cloth or paper towel to further reduce bacteria.
• Remove the outer leaves of lettuce or cabbage prior to use.