Abstract
Babesia odocoilei is a tick-borne protozoal parasite which infects the erythrocytes of members of the families Cervidae and Bovidae. Infection can result in hemolytic anemia, lethargy, anorexia, and death. The reservoir host of B. odocoilei is the white-tailed deer (Odocoileus virginianus); however, infections with overt disease have only been documented in reindeer (Rangider tarandu tarandus), caribou (Rangider tarandu caribou) and captive elk (Cervus elaphus canadensis). Infected elk may remain asymptomatic, creating the risk for dissemination of the pathogen when elk are relocated. Additionally, infected asymptomatic elk may contribute to the spread of B. odocoilei in the local wildlife/captive population via feeding ticks. Information regarding endemic regions of B. odocoilei infection is limited due to frequent asymptomatic infections and a lack of targeted surveillance of B. odocoilei in wildlife. To obtain data on B. odocoilei infection in wild elk in Pennsylvania, we tested blood samples collected from 190 hunter-harvested wild elk between 2016 and 2017. Of the 190 blood samples tested, 18.4% (35/190) tested positive for Babesia spp. Genetic sequencing of the positive samples showed a 98.0–100.0% match for B. odocoilei. No other Babesia species were identified. Results of this study documents B. odocoilei infection within hunter-harvested wild elk from Pennsylvania.
Highlights
Intraerythrocytic protozoal parasites of the genus Babesia are widespread throughout North America, infecting a variety of hosts
In 2016 and 2017, blood samples were collected during the 6-day hunting season in early November from wild elk harvested in five counties in Pennsylvania, USA: Elk county, Clearfield county, Cameron county, Centre county, and Clinton county
190 wild elk blood samples were collected during two hunting seasons in Pennsylvania: 85 from 2016 and 105 from 2017
Summary
Intraerythrocytic protozoal parasites of the genus Babesia are widespread throughout North America, infecting a variety of hosts. Potential for emerging diseases caused by the Babesia species is dependent on maintenance of the parasite via the cycle of transmission between competent vectors and vertebrate hosts within the environment. In North America, Ixodidae ticks are the only known vector for Babesia species, transmitting the parasite to vertebrate hosts while attached and feeding. High parasitemia of Babesia species in a host can lead to babesiosis, a disease with a range of symptoms dependent on the infecting species and host [1,2]. Babesia odocoilei falls within the informally named Small Babesia clade, Babesides, and is maintained in nature through a cycle involving white-tailed deer (Odocoileus virginianus) and blacklegged tick (Ixodes scapularis) [3,4,5,6,7]. Infection was thought to be limited to members of the family Cervidae; recent publications have documented infection in desert bighorn sheep (Ovis canadensis nelsoni) and musk oxen
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