Cyclospora cayetanensis Ortega, Gilman and Sterling, 1994.

Type host: Homo sapiens Linnaeus, 1758, Humans.

Other hosts: Pan troglodytes (chimpanzee) from Uganda (Ashford et al., 1993); Papio sp. (baboons) and chimpanzees from Tanzania (Smith et al., 1996).

Type locality: SOUTH AMERICA: Peru, San Juan de Miraflores, ~15 km S of Lima.

Geographic distribution: Cosmopolitan.

Description of oocyst: Oocyst shape: spheroid; number of walls: 2; wall thickness: 1.1; wall characteristics: outer, ~2/3 of total thickness, rough; inner, smooth; L x W: 8.6 (8-10); L/W ratio: 1.0; M: absent; OR: present; PG: present. Distinctive features of oocyst: small size.

Description of sporocysts and sporozoites: Sporocyst shape: ovoid; L x W: 6 x 4 (5.5-7 x 3-4); L/W ratio: 1.5; SB: present; SSB: present; PSB: absent; SR: present; SR characteristics: large spherical globules; SP: 1 x 9 (1 x 8-10). Distinctive features of sporocyst: presence of SB and SSB and SP that are longer than L of sporocyst.

Prevalence: 15/230 (6%) and 26/147 (18%) from 2 separate prospective cohort studies in children ranging from birth to 2.5 yrs of age.

Sporulation: Exogenous. About 20% of oocysts in 2.5% aqueous (w/v) potassium dichromate sporulate between 7-13 days when kept at 25º or 32ºC (Ortega et al., 1993).

Prepatent period: Unknown.

Patent period: 7-70 days (Ortega et al., 1993).

Site of infection: The jejunum seems to be the preferred site of infection. Ortega et al. (1997) described 2 asexual (merogonous) generations, the first with 8-12 merozoites and the second with only 4 merozoites.

Material deposited: Phototype in the USNPC No. 83416, document #97.

Remarks: Since the early 1980s, it was believed that the oocysts of this organism represented a species of blue-green algae and the acronym CLB, for cyanobacteria-like body, was commonly used to describe it when found in the feces of humans who were experiencing episodes of diarrhea (for historical reviews see McClelland, 1997; Ortega et al., 1993, 1994; Soave, 1996). Ashford (1979) was probably the first to recognize that the stage found in the feces, oocysts, represented a coccidium, but he failed to name it. It wasn't until Ortega et al. (1993), in Peru, repeated the work of Ashford (1979) and induced the sporulation of the CLBs in the laboratory that the identity of this organism as a Cyclospora sp. came to light. Ortega et al. (1994) finally named the organism and distinguished it from other members in the genus which only have been found in myriapods, snakes, insectivores and rodents. Unfortunately, there is still some uncertainty as to the exact structures in the sporulated oocyst. The written description of Ortega et al. (1994) states, "A polar body and oocyst residuum are also present." However, neither the photomicrographs nor the line drawing they present show either of these structures nor is any qualitative or quantitative information given; thus, the actual presence of these diagnostic features of the sporulated oocyst is uncertain at this time.

References: Ashford (1979); Ashford et al. (1993); McClelland, 1997; Ortega et al. (1992, 1993, 1994, 1997, 1998); Smith et al. (1996); Soave (1996).