ABSTRACT
Cryptosporidium have been documented to be one of the main causative organisms in waterborne gastroenteritis in children. In the present study, a polyspecific anti- Cryptosporidium oocyst antibodies have been raised in pathogen rabbit and used to detect C. parvum oocysts in stool using direct immunofluorescent assay [DIFA]. The effect of different common laboratory preservatives on the stability of C. parvum oocysts was studied. A total number of 316 stool specimens have been collected from diarrheic children ranging in age from one month to 12 years attending the Suez Canal University Hospital. The stability of oocysts stored for one month at room temperature and at 4°C in 10% formalin, 2.5% potassium dichromate, polyvinyl alcohol [PVA], sodium-acetate-formalin [SAF] and merthiolate-iodine-formaldehyde [MIF] was tested against the developed antibodies using DIFA at different time intervals [1, 3, 7, 14 and 30 days]. The percentage of infection was 6% and it was common in infants [less than 2 years] than in children [above 2 years]. The results revealed that the most effective preservative was 10% formalin at both temperatures if the samples were used within two weeks of preservation. 2.5% potassium dichromate seemed to be the second efficient preservative, if the samples were preserved at 4°C, and used within the first week of preservation. Unpreserved [control] and preserved samples in PVA and SAF could be used if DIFA was done on the first day of preservation. On the other hand, MIF failed to keep C. parvum oocysts suitable for detection by DIFA even in the first day of preservation. From the above mentioned results, it was concluded that DIFA was more practical than the ordinary staining procedures, and DIFA of stool samples preserved in 10% formalin was the best laboratory diagnostic technique particularly for field and survey studies