Transmission of Cytauxzoon felis by injection of Amblyomma americanum salivary glands

Background: Cytauxzoonosis is a life-threatening disease of cats, caused by the tick-borne piroplasmid hemo-parasite, Cytauxzoon felis. Current experimental models for cytauxzoonosis rely on either tick transmission or direct injection of infected cat tissues. These models require researchers to directly work with infected ticks or use cats with acute cytauxzoonosis. To improve the feasibility and accessibility, there is a need to establish sharable resources among researchers. In related piroplasmid parasites, sporozoite-based inoculums are routinely produced from tick salivary glands, cryopreserved and distributed to other investigators and facilities. For these parasites, sporozoites have been the basis for vaccine development and in vitro cultivation, both of which remain lacking for C. felis research. If infectious sporozoites can be similarly isolated for C. felis, it would significantly broaden our capabilities to study this parasite. Aims of this study was to determine if C. felis sporozoites in-oculums collected from the salivary glands of Amblyomma americanum ticks were capable of inducing cytaux-zoonosis in naive cats.Materials and methods: A. americanum nymphs were acquisition-fed on a donor cat chronically infected with C. felis and allowed to molt to adults. Four groups of adult ticks (n = 50/group) were either stimulation-fed for 4 days on naive cats or were heated at 37 degrees C for 4 days. After these treatments, salivary glands (SG) of each group of ticks were collected to create inoculums. Infectivity of these inoculums was then tested by subcutaneous in-jection into naive cats.Results: The two naive cats used for stimulation feeding and as controls both developed cytauxzoonosis, indi-cating these groups of ticks were capable of producing infectious sporozoites. Of the 2 cats that were injected with SGs from the stimulation-fed ticks, one cat developed cytauxzoonosis and C. felis infection was confirmed by both light microscopy and PCR. The other cat did not develop cytauxzoonosis and only had equivocal evidence of infection. Neither cat injected with SGs from the heated ticks developed cytauxzoonosis. One of these cats had equivocal evidence of infection and one had no evidence of infection.Conclusion: This study validates the feasibility of collecting infectious sporozoites from C. felis-infected ticks that can be used to infect naive cats. While this model requires further optimization, it has the potential to expand resources to study C. felis and further advance research in this field.

Automated summary

The aim of this study was to determine if C. felis sporozoites collected from the salivary glands of Amblyomma americanum ticks could induce cytauxzoonosis in naive cats. The results showed that the inoculums produced by stimulation-fed ticks were capable of causing cytauxzoonosis, validating the feasibility of collecting infectious sporozoites from C. felis-infected ticks.