The influence of desiccation and UV radiation on the development and survival of free-living stages of cyathostomins under field and laboratory conditions

The present work describing both laboratory and field experiments was performed to assess the effects of desiccation and UV radiation on the development and survival of free-living stages of equine cyathostomins.

Cyathostomin larvae in horse faeces did not develop to the infective stage when faecal humidity levels dropped below 23 %, nonetheless solitary preinfective larvae were still recovered after 151 days (humidity 19.5 %). The development to infective stage after remoistening occurred for the last time after 54 days following desiccation.

Preinfective stages are susceptible to the effects of the direct desiccation stage. The preinfective larvae were rapidly killed within one minute, the cyathostomin eggs within 5 hours. The numerous normal mobile infective larvae were encountered after 35 days of the desiccated period. The preinfective stage of cyathostomins also showed very little tolerance to direct sun radiation: most eggs were killed by the exposure within 3 hours and the preinfective larvae within 1 hour. The survival of infective larvae was, on the other hand, unaffected by sun radiation after 7 days (P < 0.05). However, desiccated infective larvae were then found to be susceptible to UV radiation, resulting in total mortalities after 5 days.