By Dr. Colin Michie
Food. Food. Food. It floods all media! Bargain meals, drinks, smoothies, snacks, vitamins, protein diets, maxing peptide turbo specials – all with advertisements and advice. Yet the safety of food and water is never mentioned! A great diversity of foods, beverages and water we buy and prepare are safe – this is a major achievement in public health – but parasites can challenge and catch us out.
In May, a cyclospora diarrhoea outbreak began in the US. The problem has not yet been resolved. Over a thousand cases have been identified. Early reports suggested shredded lettuce in Taco Bell was responsible, but at the time of writing, the Cyclospora cayetano have been traced to iceberg lettuces grown in Mexico. Cyclospora pests are unlikely to be a risk to salad shoppers on St. Maarten, but check the sources of your salads! Cyclospora were first described in the Cayetano Heredia University, Lima, in late 1970s Peru – the species name ‘cayetano’ commemorates this discovery. Large outbreaks were documented 20 years later. Crops including salads and herbs around the world have since been found to contain cyclospora.
Cyclospora are difficult to track for two reasons: First, identification times. There is a delay of one to two weeks between ingesting parasites in a salad and developing the main symptom – diarrhoea. Medical consults, samples and diagnosis add extra time. Second, many affected individuals have mild symptoms and do not necessarily receive investigations, so accurate accounting of cyclospora infestations is difficult – this is truly a neglected tropical disease. Many developing countries do not have facilities to check samples for this organism. It is possible some outbreaks – particularly in children with diarrhoea – are much larger than expected.
Cyclospora invade the small intestine then get to work making eggs. They are much larger than viruses or bacteria – and potent, too. Eating small numbers of them can result in explosive, watery diarrhoea. They rarely invade further than the gut lining unless the immune system is damaged. It is the immune system that eventually kills off the protozoans; but during this time, cyclospora eggs are passed out in the stool. There is likely to be a loss of appetite, bloating, cramping and weight loss, possibly fever and “flu-like” illness. Pharmacological treatment is needed to prevent recurrent diarrhoea. Treatments with trimethoprim-sulfamethoxazole, often sold as Bactrim, are effective as they starve protozoans of folic acid which they need to make eggs.
Cyclospora eggs have to mature in a warm environment outside a person for weeks before becoming infectious. Most transmissions described are through food chains; infestations have been identified in travellers, who may suffer with multiple parasitic gut infections.
Other more invasive protozoans may be better known. Such tiny beastly parasites include amoebiasis, toxoplasmosis, giardiasis, cryptosporidiosis and trypanosomiasis. All infest us through faecal contamination of foods – they are not passed between humans. The wider ecologies of protozoans are a research frontier because there are also harmless protozoans living in our gut microbiomes. Are these “better” bugs useful or protective? Such questions are being examined now that genetic typing can identify and count protozoans more accurately. Other questions can be asked – for instance: Do fellow mammals share cyclospora with humans? Rodents are the most numerous mammals on our planet; their numbers have escalated in urban areas. Many critters are known to carry giardia and cryptosporidia, rarely cyclospora, but it is not clear if they spread their protozoans to humans or cause outbreaks.
Cyclospora have been found in many animals, domesticated and in zoos, but the risks from their protozooans to us is probably small. Year on year, cyclospora contamination from sanitation failures or recycled waste water appears to be driving larger outbreaks. Whether it is providing effective latrines on farms or carrying out wastewater analysis, attempts are being made to control protozoans and other pathogens in water supplies and food systems. It is likely, too, that changes in local climates are making it possible for more cyclospora eggs to mature and become infectious.
Several practical habits can reduce our personal exposures to a protozoan infection, such as from cyclospora. Although potentially contaminated foods should be removed by supermarkets and shops, it can be valuable to check online and to share information about possible risks. Social media has recently been found unreliable in this respect and unverified information can lead to confusion – care is needed.
A family that once looked after me in St. Maarten washed all salads and vegetables thoroughly in salt water as a protective strategy against food poisoning. Washing fresh foods is useful, although adding salt adds little value to the disinfection. Observing careful handwashing before preparing meals or eating is always a wise precaution, but it is worth remembering every day that parasites love dirt and soils.
Dr. Colin Michie specializes in paediatrics, nutrition, and immunology. Michie has worked in the UK, southern Africa and Gaza as a paediatrician and educator and was the associate Academic Dean for the American University of the Caribbean Medical School in Sint Maarten.
Useful resources: cdc.gov/cyclosporiasis/about/index.html ~ cdc.gov/foodnet/about/index.html
~ iris.who.int/items/75c7c8fb-7c2d-49f6-ac95-a5e0ffe98bdd
