Transmission of Nocardia farcinica by two Ixodid species

Abstract

The cultural, morphological and pathogenic characteristics of Nocardia farcinica were studied.

Guinea pigs were susceptible to Nocardia farcinica, showing typical lesions following injections with cultures or infected tick materials.

Rabbits readily acquired a generalized infection with Nocardia farcinica but only a small proportion of those so injected developed lesions.

Generalized Nocardia farcinica infections did not result from minor skin traumata (pin -pricks and scarification) made in rabbits' ears and guinea pigs' backs which had previously been painted with cultures of the organism, and neither did they result when ticks were fed on surfaces so treated.

The feeding performance and developmental periods of Amblyomma variegatum and Hyalomma anatolicum excavatum were also precisely studied.

Larvae and nymphs of Amblyomma variegatum acquired Nocardia farcinica infection from rabbits and, at periods of up to nine weeks, transmitted these infections to other rabbits when feeding as the subsequent instars. Trials proved that this period of retention of transmissible infection can extend up to 33 weeks.

Nymphs and adults of Amblyomma variegatum showed their ability to retain transmissible infection under various environmental conditions.

Larvae and nymphs of Hyalomma anatolicum excavatum acquired Nocardia farcinica infection from rabbits and, at periods of up to eight weeks, transmitted the infection to other rabbits when feeding as the following instars. However, subsequent trials showed that Hyalomma anatolicum excavatum cannot retain naturally transmissible Nocardia farcinica infection for longer periods.

Trans-ovarial transmission was not achieved with either species.

These clear demonstrations of the trans-stadial transmission of the bovine farcy organism confirmed the existence of an epidemiological feature which has previously only been suspected.