Assessment of the Effect of Sodium Hypochlorite, An Artificial Exsheathment Medium, on the Viability of Nematode Larvae

Sodium hypochlorite (NaOCl) is used extensively as an artificial exsheathment medium of nematode larvae in various studies, such as comparing the efficacy of drugs, and assessment of resistance to anthelmintics or evaluation of plant extracts as anthelmintics due to its unique capacity for tissue dissolution. Studies with NaOCl by other authors indicate that the compound, although highly effective as an exsheathing agent, significantly lowers the infectivity of the exsheathed larvae produced, suggesting reduced viability. We used Strongyloides papillosus larvae, a nematode that naturally lacks a protective sheath and a potentially highly motile organism, as a model to exclude or confirm possible negative effects on the viability of the parasite. Motility was taken as a viability assay. Larvae were designated as actively motile, sluggish, or immotile. Results were presented as additional supplementary movie files. The viability of larvae is dependent on both the concentration and the time of exposure to the compound. There are certain concentration (C) and time (T) limits beyond which viability is impaired (0.3% ˃ C ˃ 0.2%; 10 min ˃ T ˃ 5 min). It is concluded that results from studies where NaOCl is used as an exsheathment medium should be interpreted with caution as the compound is capable of reducing the viability of larvae. It may even induce structural damage.