Detection of a Rickettsia sp. and an Ehrlichia chaffeensis-like organism in ticks parasitizing the endangered Florida Grasshopper Sparrow (Ammodramus savannarum floridanus)

Between 2013 and 2015, 163 resident endangered Florida Grasshopper Sparrows (Ammodramus savannarum floridanus) and four migratory Eastern Grasshopper Sparrows (A. savannarum pratensis) were examined for the presence of ticks in peninsular Florida. Thirteen Amblyomma maculatum and seven Haemaphysalis chordeilis ticks were removed from 13 Florida Grasshopper Sparrows. Two A. maculatum were discovered on two Eastern Grasshopper Sparrows. Polymerase chain reaction (PCR) and sequencing of resultant amplicons of some of the tick specimens were performed to determine if ticks were infected with pathogenic bacteria. Salivary gland and midgut contents of five of six (83%) of the H. chordeilis tested positive for a novel Rickettsia closely related to, but distinct from, Rickettsia aeschlimannii (causative agent of Mediterranean spotted fever-like illness), an infectious zoonotic bacterium that has not been previously reported in the United States. Four of 14 (29%) of the A. maculatum tested positive for an agent most closely related to an uncultured Ehrlichia previously isolated from Oriental house rats (Rattus tanezumi; 97.5% identity to GenBank KM817187), which is genetically similar to Ehrlichia chaffeensis (causative agent of human monocytic ehrlichiosis), another infectious zoonotic bacterium. Blood from 16 Florida Grasshopper Sparrows and one Eastern Grasshopper Sparrow tested negative for spotted fever group rickettsiae, Anaplasma spp. and Ehrlichia spp. We recommend that additional collections and screening of ticks and blood from Florida Grasshopper Sparrows be undertaken to determine the rates of infection with rickettsiae and ehrlichiae in these imperiled songbirds.