Natural and Experimental Infection of White-Tailed Deer (Odocoileus Virginianus) From the United States With an Ehrlichia Sp. Closely Related to Ehrlichia Ruminantium

Abstract

ABSTRACT:An Ehrlichia sp. (Panola Mountain [PM] Ehrlichia sp.) closely related to Ehrlichia ruminantium was recently detected in a domestic goat experimentally infested with lone star ticks (LSTs, Amblyomma americanum) collected from Georgia, USA. The infected goat exhibited pyrexia and mild clinical pathologic abnormalities consistent with ehrlichiosis. At least two other Ehrlichia species (Ehrlichia chaffeensis and Ehrlichia ewingii) are maintained in nature by a cycle involving LSTs as the primary vector and white-tailed deer (Odocoileus virginanus) as a known or suspected reservoir. To investigate the possibility that white-tailed deer are potential hosts of the PM Ehrlichia sp., whole blood samples collected from 87 wild deer from 2000 to 2002 were screened with a species-specific nested PCR assay targeting the citrate synthase gene. In addition, two laboratory-raised white-tailed deer fawns were each infested with 120 wild-caught LST adults from Missouri, USA, and blood samples were periodically collected and tested for the PM Ehrlichia sp. Of 87 deer tested from 20 locations in the southeastern United States, three (3%) deer from Arkansas, North Carolina, and Virginia were positive for the PM Ehrlichia sp. Wildcaught ticks transmitted the PM Ehrlichia sp. to one of two deer fawns, and colony-reared nymphal LSTs acquired the organism from the deer, maintained it transstadially as they molted to adults, and transmitted the PM Ehrlichia sp. to two naïve fawns. These findings indicate that white-tailed deer are naturally and experimentally susceptible to infection with an Ehrlichia sp. closely related to E. ruminantium and are able to serve as a source of infection to LSTs.

Ehrlichiosis in Brazil

“…Recently, an Ehrlichia sp. closely related to E. ruminatium was detected in white-tailed deer from the United States, suggesting that the range of Ehrlichia species infecting these animals is broader than first thought (YABSLEY et al, 2008). To date, there are no reports of other Ehrlichia species rather than E. chaffeensis in wild ruminants from Brazil; monitoring of these animals is highly desired.…”

Natural history of Ehrlichia ruminantium

“…The Panola Mountain Ehrlichia species included in the Ehrlichia phylogenetic tree The organism does, however, produce a mild febrile illness in goats (Loftis et al, 2008a) and in humans (Reeves et al, 2008), and its natural reservoir may be the widely distributed white-tailed deer (Odocoileus virginanus) (Yabsley et al, 2008). Subsequent to its first detection the Panola Mountain Ehrlichia organism has been found in A. americanum ticks in 10 states in the U.S.A. (Loftis et al, 2008b) and the presence of genetic variations between isolates from different locations suggests that the organism is not a recent introduction into the United States.…”

Progress and obstacles in vaccine development for the ehrlichioses

“…ticks, including two North American species, Amblyomma maculatum and Amblyomma cajennense , appear to have similar transmission efficiency [20]. Notably, a closely related organism (by glt A and map 1 sequence analysis) has recently been discovered in the USA in a naturally infected goat and in ticks collected from ten states [26,27]. …”