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First described in 1979, this is an emerging parasitic disease with a cosmopolitan distribution (Almeria et al. 2019). There are regular outbreaks in USA and Canada associated with the importation of fresh berries (Dixon et al. 2016). The life cycle begins with the ingestion of oocysts (8–10 μm diameter) containing infective sporozoites. Once the oocysts reach the duodenum and upper small intestine, they release the sporozoites and these invade the gut epithelial cells. They then transform into type I merozoites that then divide to form type II merozoites. The type II merozoites transform into meronts and these give rise to microgametocytes and macrogametocytes. Fusion of a microgametocyte with a macrogametocyte gives rise to zygote, and this develops into an oocyst that is shed with the faeces. The oocyst then undergoes sporulation to produce two sporocysts each containing two sporozoites. Sporulation takes 7–15 days depending upon the environmental conditions and therefore transmission probably occurs through contamination of food and water rather than direct person‐to‐person/contaminated object contact.

The symptoms of infection are non‐specific and resemble those of many other gastrointestinal diseases. Patients suffer from abdominal pain, watery diarrhoea, flatulence, low‐grade fever, anorexia, and weight loss. In endemic regions, the symptoms tend to be worse in young children and in non‐endemic regions most people who become infected express symptoms. Persons who are immunosuppressed and AIDS patients are more seriously affected.