MICROBIOLOGY

• Obligate intracellular coccidian parasite; infects epithelial cells of small intestine. Destroys brush border and alters mucosal architecture.[4]
• Excreted in stool as oocysts (spherical, 8-10 μm in diameter), which may be shed intermittantly and at low levels. Sporulation (maturation of oocysts) occurs outside host and takes 7-12d.
• Transmitted by fecal-contaminated soil, food and water. Humans only known host and reservoir. Human-to-human transmission unlikely as excreted oocysts must sporulate before becoming infectious.
• Both sporadic infections and outbreaks occur. Frequency peaks during spring & summer in the U.S., associated with fruits and vegetables, i.e., raspberries, mixed salad greens, cilantro, and basil.[5]
  • 2018 outbreak season comprised 2 multistate outbreaks and 761 laboratory-confirmed cases.[6]
• Lack of validated molecular typing tool limits outbreak investigations.[6]
• Endemic areas, i.e., Peru, Nepal, Haiti, Guatemala, Indonesia. Low-level endemicity in US cannot be excluded.