چکیده (انگلیسی):

Objective: To determine the ability of oysters to trap and maintain viable Cryptosporidium
oocysts, and the feasibility of Cryptosporidium multiplication in oysters' organs.
Methods: Seventy oysters were raised in experimentally seeded natural seawater for up
to 3 months, with weekly oocysts inoculations. Cryptosporidium oocysts, viable and nonviable,
as well as other stages were detected using two immunofluorescence vital staining
techniques (Sporo-Glo and Merifluor®) with confocal microscopy. Viability rate at
various times after inoculations were calculated.
Results: Cryptosporidium oocysts were found most concentrated in oysters' digestive
organs than in gill and water inside the oysters. Oocysts numbers were 857.33 at 24 h
after inoculation and strikingly decreased to 243.00 and 126.67 oocysts at 72 h and 7
days, respectively. The oocysts in oyster were also less viable over time; 70%, 60% and
30% viable at 24 h, 72 h and 7 days after inoculation, respectively. At 77 days, the
number of oocysts was very low and none was found at 84 days onwards. Although some
oocysts were ruptured with released sporozoites, there was no evidence throughout the
study of sporozoites multiplication to indicate that oyster is a biological host. Despite the
significant reduction in oocysts number after 7 days of inoculation, the remained viable
oocysts can still cause cryptosporidiosis.
Conclusion: The findings confirm that Cryptosporidium parvum does not multiply in
oyster, and is therefore not a biological host. Nevertheless, the results suggest that oyster
can be an effective transmission vehicle for Cryptosporidium oocysts, especially within
24–72 h of contamination, with viable oocysts present at up to 7 days post infection.
Unless consuming well-cooked oyster dishes, eating raw oyster remains a public health
concern and at least 3 days of depuration in clean sea water prior to consumption is
recommended.