Chronic diarrhea due to Cyclospora spp. infection.

Dear editor,

In March 2012, a old man presented with the complaints of shortness of breath, myalgia, fatigability, and anorexia. Physical examination revealed normal findings. He had history of watery stool since one month.

Stool and blood sample were collected. Macroscopic appearance of stool was yellow, watery with no blood and mucus. Microscopic examination of saline wet mount was negative for ova and cyst. Iodine wet mount of stool revealed moderate number of unicellular cysts with double layer [Figure 1]. Routine stool culture for bacteria was negative. The result of routine blood analysis was normal except for low hemoglobin content (4.2-g Hb/dl). Serological tests such as rapid human immunodeficiency virus test and hepatitis B surface Ag detection were negative.

Figure 1

Iodine wet mount of stool showing oocyst of Cyclospora spp. in unconcentrated stool (×40)

Stool examination was repeated after formal-ether sedimentation technique and modified acid-fast staining (AFB) was performed. Modified AFB staining revealed colorless to pink as well as deep purple oocysts, morphologically consistent with that of Cyclospora spp. oocysts, confirmed by more than one experienced personnel [Figure 2]. Subsequent stool sample also revealed oocyst like structure in iodine wet mount and modified AFB staining.

Figure 2

Modified acid fast staining of stool showing oocyst of Cyclospora spp. in unconcentrated stool (×100)

In most laboratories, stool is not usually examined for Cyclospora spp. unless such testing is requested. Under iodine wet mount, immature oocyst is uniformly spherical with bi-layered thick wall. Outer rough coat is thick while the inner layer is smooth with polar body and oocyst residuum in the center.[12]

Most common method used to identify oocysts of Cyclospora is modified acid fast staining.[34] The oocysts showed variability from no stain to light pink to deep purple under modified acid fast staining. The consistent morphology of Cyclospora spp. oocysts is confirmed by more than one experienced personnel. Since only trained personnel can identify oocyst, negative report is very likely. Oocyst of Cyclospora spp. is often confused with Cryptosporidium oocyst.

The identity of Cyclospora spp. oocyst is confirmed by ocular micrometer and ultraviolet (UV) fluorescence microscopy. Cyclospora oocyst are larger (8-11 μm) in diameter and are found in low to moderate numbers in stool than Cryptosporidium (4-6 μm) in diameter.[5] The identity and clinical relevance can be confirmed by repeating the stool examination for three consecutive days. Specific chemotherapy is available for Cyclospora spp. Therefore, it is important to differentiate oocyst of Cyclospora from Cryptosporidium oocyst.

The drug of choice for Cyclospora infection is trimethoprim-[sulfamethoxazole].[5] Awareness among clinicians to request for modified acid fast staining in case of clinical suspicion of Cyclospora infection may help to know the presence of the oocyst of the parasite. Non-availability of ocular micrometer and UV fluorescence microscopy are the main limiting factors.

To conclude, the incidence of Cyclospora infection in the immunocompetent individual is underestimated due to lack of awareness and appropriate diagnostic methods for identification.