Mucosal larval recovery techniques of cyathostomes: can they be standardized?

The methods used currently for enumeration of mucosal stages of cyathostomes include transmural illumination (TMI) and peptic digestion (DIG). Enumerating the inhibited early L3 (EL3) and differentiating between mucosal developing L3 (DL3) and L4 (ML4) is only possible when DIG is used. However, in some studies higher numbers of DL (DL3 + ML4) have been found when using TMI as opposed to DIG. This finding, however, is not consistent. Moreover, results are not consistent when DIG and TMI are compared for treated and control groups of horses in drug trials. Studies performed on the effect of freezing on DIG and TMI also show inconsistent results between laboratories. However, there is, evidence that digested samples can be preserved in 5-10% formalin or in 70% ethanol when used as a buffered isotonic solution. Based on these results it is premature to recommend standardized mucosal larval recovery techniques. Consequently, TMI and DIG should both be applied. Recommendations for further research for the development of standardized techniques are given.