Rain splash dispersal of third-stage larvae of Cooperia spp. (Trichostrongylidae).

Laboratory investigations were designed to study the distribution of splash droplets caused by splashes of water on the surface of a cow pat. Laboratory and field experiments were designed to evaluate the possibility of water splash dispersal of third-stage Cooperia spp. larvae from cow pats to the surroundings. One incident drop of water 5 mm in diameter falling 2.2 m on a cow pat produced approximately 1,000 splash droplets. In still air, more than 90% of the splash droplets were found within 60 cm from the point of impact, and only a few travelled beyond 90 cm. After a latent period, incident drops of water 5 mm in diameter falling 2.2 m on a cow pat of 500 g, containing 450 third-stage larvae of Cooperia spp. per g feces, resulted in splash dispersal of larvae to a maximum distance of 63 cm from the point of impact; the majority of larvae were found within 21 cm. A field experiment confirmed that lateral splash dispersal of third-stage Cooperia spp. larvae during a shower can be very effective. On one occasion there was a splash dispersal of 4,851 third-stage Cooperia spp. larvae in 45 minutes to an area from 1 to 15 cm around the periphery of a cow pat of 500 g containing 120 third-stage larvae per g of feces. This corresponds to a dispersal of 8% of total.