Preliminary studies on transmission of Chlamydia to cattle by ticks (Ornithodoros coriaceus).

Preliminary findings indicate that Ornithodoros coriaceus ticks can harbor Chlamydia for long periods and are able to transmit the agent to cattle. Field-collected O coriaceus ticks, which were infected experimentally with a bovine chlamydial agent from an aborted fetus, transmitted the agent 25 and 48 days later to three pregnant heifers. Two of these heifers aborted and the third delivered a term calf. The control heifer also aborted after intradermal (simulated tick) exposure. Also, a chlamydial agent was isolated from field-collected O coriaceus ticks in an epizootic bovine abortion (EBA)-enzootic area that were held for at least 6 months. In the same enzootic area, a chlamydial agent was isolated from a prematurely delivered calf during a severe EBA outbreak. Seemingly, this species is a cause, if not the cause, of EBA.