Quantitative comparison of different purification and detection methods for Cryptosporidium parvum oocysts

Cryptosporidium parvum (C. parvum) is the causal agent of cryptosporidiosis in many animals, mainly cattle, and possesses a high zoonotic potential. It occurs worldwide and ubiquitously. Detection of C. parvum is mainly performed directly but purification of the oocysts is useful to increase sensitivity and to obtain oocyst material for further use. The study was designed to compare (a) three different direct diagnostic methods, namely modified Ziehl-Neelsen staining, carbol fuchsin staining and conventional PCR, and (b) three routine oocyst purification methods, in particular flotation with saturated sodium chloride solution, Sheather's sucrose solution and a Percoll(®) gradient. During comparison of purification methods, special regard was paid to the ability to separate morphologically intact oocysts from the morphologically degenerated fraction or viable from non-viable oocysts, respectively.

(a)

Most effective in C. parvum oocysts detection in calf faeces was PCR; carbol fuchsin and modified Ziehl-Neelsen stainings achieved comparable results. (b) Purification methods: Oocyst flotation using sodium chloride solution showed to be superior to Percoll(®) gradient centrifugation and sugar flotation in terms of purification quality, recovery efficacy (yield) and reduction of the proportion of degenerated or non-viable oocysts.