In vitro development of Trichostrongylus axei, from infective larvae to young adults.

Advanced stages of Trichostrongylus axei were grown from exsheathed infective larvae in roller culture systems consisting of a complex cell-free medium, API-6, when used alone or supplemented for 8- or 21-day intervals with pepsin or reducing agents, or both. Young adult males and females were the most advanced stages attained. This stage was attained by days 18--21, when medium API-6 contained pepsin for 8 or 21 days, with or without reducing agents for the first 8 days; and by days 24--26, when medium API-6 was nonsupplemented. Trichostrongylus axei did not advance beyond early fourth stage or fourth molt when API-6 contained reducing agents for 8 or 21 days or reducing agents and pepsin for 21 days. The optimal culture system for development to young adults required medium API-6 supplemented with pepsin for 21 days and reducing agents for the first 8 days. This system produced maximal yields of less than 1% young adults in populations of about 100,000 T. axei by days 21--28.