Transmission of Cytauxzoon felis to domestic cats by Amblyomma americanum nymphs

Abstract

BackgroundSuccessful Cytauxzoon felis transmission studies have occurred using Amblyomma americanum adults acquisition-fed as nymphs on an experimentally infected domestic cat or Dermacentor variabilis adults fed as nymphs on a splenectomized bobcat. Here, we evaluated A. americanum and D. variabilis nymphs acquisition-fed as larvae on a C. felis-infected carrier domestic cat for competence to transmit the protozoan parasite as nymphs to naïve, healthy domestic cats.MethodsAmblyomma americanum and D. variabilis larvae were applied to a chronically infected, parasitemic C. felis donor cat (Felis catus) and allowed to feed to repletion. Engorged larvae were collected and held through ecdysis. Three cats were each infested with 66 A. americanum or 66 D. variabilis emerged nymphs. Cytauxzoon felis infections in principal cats were determined by clinical signs and detection of circulating parasite by blood smear and PCR evaluation.ResultsClinical signs of cytauxzoonosis were observed in cats infested with A. americanum nymphs beginning 12–15 days post-infestation (dpi). The same cats were PCR positive on 12–14 dpi; piroplasms were evident in blood smears at 16 dpi, and macrophage schizonts were observed in stained spleen impression smears in two animals at necropsy. Cats infested with acquisition-fed D. variabilis nymphs remained clinically normal and did not develop detectable parasitemia over the course of the study as determined by blood smear and PCR.ConclusionsCytauxzoon felis was successfully transmitted to domestic cats by A. americanum nymphs acquisition-fed as larvae on the donor cat. However, we were not able to transmit C. felis to healthy domestic cats with D. variabilis nymphs that were simultaneously acquisition-fed on the same donor cat. Results from this study suggest that larval and nymphal A. americanum likely play important roles in natural transmission cycles of C. felis.

Prevalence of Cytauxzoon felis Infection-Carriers in Eastern Kansas Domestic Cats

“…Acute cytauxzoonosis is one of the most fatal diseases in domestic cats, such that for a long time domestic cats were thought to have a minimal, if any, role in the enzootic maintenance of C. felis [ 11 , 18 , 32 ]. Over the past two decades, several prevalence studies have confirmed domestic cats as C. felis reservoirs [ 39 , 40 , 41 ] and experimentally demonstrated that domestic cats can serve as competent reservoirs for subsequent C. felis transmission by ticks, especially A. americanum [ 3 , 4 , 38 ]. C. felis -carrier surveys in states adjacent to Kansas have identified that 0.8–12.9% of domestic cats may be C. felis -carriers [ 39 , 41 ].…”

“…Successful transmission of infectious sporozoites requires transstadial maintenance of the parasite through larvae-to-nymph or nymph-to-adult ecdysis. In the U.S., competent biological transmission vectors for C. felis include the ixodid ticks Dermacentor variabilis (American dog tick) and Amblyomma americanum (Lone star tick) [ 2 , 3 , 4 , 5 ]. The geographic distribution of D. variabilis extends throughout the eastern half of the U.S. and in focal regions along the western coast [ 6 , 7 ].…”

Acute Cytauxzoon felis Cases in Domestic Cats from Eastern Kansas, a Retrospective Case-Control Study (2006–2019)

“…Transstadial maintenance of the parasite through the larvae-to-nymph or nymph-to-adult ecdysis is required for the transmission of the infectious sporozoites to a new felid host during the subsequent tick bloodmeal. The competent biological transmission vectors of C. felis in the U.S. include Dermacentor variabilis (American dog tick) and Amblyomma americanum (Lone star tick) [ 2 , 3 , 4 , 5 ]. The range of D. variabilis encompasses the eastern U.S. as well as focal regions in the west [ 6 , 7 ].…”

A Fluorescence In Situ Hybridization (FISH) Test for Diagnosing Babesiosis

“…Because Theileria equi was until recently classified as Babesia equi , it may be phylogenetically closer to Babesia than other Theileria species, leading to the cross-reactivity observed in the Babesia genus-specific FISH test. Cytauxzoon felis is a tick-borne apicomplexan parasite that infects felids worldwide and causes severe disease among domestic cats in the US [ 22 ]. The ability of the Babesia genus-specific FISH test to differentiate B. felis from C. felis requires further investigation, because in silico analysis predicts that there may be a weak cross-recognition of C. felis .…”