Minimum transmission time of Cytauxzoon felis by Amblyomma americanum to domestic cats in relation to duration of infestation, and investigation of ingestion of infected ticks as a potential route of transmission

Objectives The objectives of the present study were to determine the duration of infestation by Amblyomma americanum necessary for transmission of Cytauxzoon felis to domestic cats and to determine if ingestion of C felis-infected A americanum by cats is a route of transmission. Methods Forty-nine cats were assigned to one of seven groups, with seven cats per group. Cats were infested with A americanum adults, acquisition fed as nymphs on a cytauxzoonosis survivor cat, for 12 h (group 1), 18 h (group 2), 24 h (group 3), 36 h (group 4), 48 h (group 5) and to repletion (group 7; control). Cats in group 6 were fed C felis-infected ticks. Thumb counts were performed at the end of the duration of infestation for groups 1-5 and at 48 h for the control group. For group 6, 50 live C felis-infected adult A americanum were mixed with food and fed to each of the cats. Transmission of C felis was determined by examining blood of cats by DNA extraction followed by PCR. Results Of 50 ticks placed on each cat (groups 1-5 and 7), the arithmetic mean attachment SEM ranged from 46.9 +/- 1.9 in group 3 to 49.3 +/- 0.3 in group 1. In group 6, the average number +/- SEM of ticks ingested was 46.5 +/- 2.3. One cat in group 5 that had been infested for 48 h became infected with C felis. None of the cats in group 6 (ingestion) became infected with C felis. Six of 7 (85.7%) cats in group 7, the control group, became infected with C felis. Conclusions and relevance Our results indicate that transmission of C felis to domestic cats can happen as quickly as >36 h but 48 h of exposure to A americanum infected with C felis and that ingestion of C felis-infected A americanum is not a likely route of transmission.