Improved in vitro cultivation of larvae of the bovine lungworm Dictyocaulus viviparus.

Parasitic larvae of Dictyocaulus viviparus are of major importance for the development of immunity in cattle. The conditions for in vitro cultivation of D. viviparus larvae as well as their morphology have thus far been only poorly investigated. Exsheathed larvae were cultivated in vitro in RPMI-1640 (Gibco-BRL, pH 7.2) containing 20% newborn Calf serum, 200 U Moronal/ml, and 200 U penicillin/streptomycin/ml. Incubation was performed at 39.5 degrees C at 0, 5%, 10%, and 20% CO2. Average development rates to third-moult (3 M) or fourth-stage (L4) larvae at 5% CO2 incubation were 8.33% (SD +/- 7.76%), 22.52% (SD +/- 13.09%) at 10% CO2, and 38.01% (SD +/- 15.63%) at 20% CO2. These differences were statistically significant. Some morphological features of these larvae are described.