Open Access
Review Article

Table 3

Advantages and limitations of the techniques used to assess infectivity and viability.

Methods Parasites Advantages Limitations
Bioassays
[I]
Cp & Ch / G / T - Requires a single (oo)cyst
- Application on complex food matrices
- Reliable exposure assessment of humans to infective protozoa.
− Reliable assessment of inactivation efficacy
- Ethical concerns
- Expensive method and labor intensive
- Lack of reliability with low numbers of (oo)cysts
- Discrimination of large but not fine differences between treatments
- Long time-to-results (one week minimum)
Cell Culture
[I]
Cp & Ch / T - Correlation with bioassays
- Requires a single (oo)cyst
- Reliable exposure assessment of humans to infective protozoa
- Reliable assessment of inactivation efficacy
- Lack of standardized assays
- Medium (48/72h) to long (10 days) time to results
- Not applicable to Giardia
- No application on complex food matrices
Methods based on morphology and physical properties
[V]
C / G - Correlation between electrorotation and PI exclusion method
- Rapid
- Require a single (oo)cyst
- Require purified (oo)cysts
- No data on viability relative to infectivity measure
- No application in exposure assessment in food
Excystation
[V]
C / G / T - Correlation with PI exclusion method
- Rapid
- Non-expensive
- Requires large numbers of purified (oo)cysts
- Variable excystation rate
- Over/underestimation of the exposure of humans to infective protozoa*
- Over/underestimation of inactivation efficacy*
- No application on complex food matrices
Vital dye exclusion
[V]
C / G / T - Correlation with excystation for PI dye (C)
- Rapid and relatively simple
- Non-expensive
- Requires a single (oo)cysts
- Application on complex food matrices
- Requires purified (oo)cysts
- Few applications for T. gondii
- Overestimation of the exposure of humans to infective protozoa*
- Underestimation of inactivation efficacy*
RT-PCR
[V]
C / G / T - Rapid
- Identification of (oo)cysts of human health significance
- Easy to standardize
- Requires low numbers of (oo)cysts
- Application on complex food matrices
- Limit of detection variable depending on matrices
- Overestimation of the exposure of humans to infective protozoa*
- Underestimation of inactivation efficacy*
FISH
[V]
C - Rapid
- Non-expensive
- Requires a single (oo)cysts
- Requires purified (oo)cysts
- Overestimation of the exposure of humans to infective protozoa*
- Underestimation of inactivation efficacy*
- No application on complex food matrices
NASBA
[V]
C - Correlation with PI exclusion method
- Rapid
- Non-expensive
- Requires low numbers of (oo)cysts
- Overestimation of the viable population
- Non-quantitative
- No data on viability relative to infectivity measure
- No application in exposure assessment in food
PMA-PCR
[V]
C - Rapid
- Requires low numbers of (oo)cysts
- Can be coupled to genotyping
- Easy to standardize
- Overestimation of the viable population
- No data on viability relative to infectivity measure
- No application in exposure assessment in food

[I]: infectivity. [V]: viability. C: Cryptosporidium spp.; Cp: C. parvum; Ch: C. hominis; G: Giardia duodenalis; T: Toxoplasma gondii.

*

Based on the comparison of viability relative to infectivity.

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