ARS | Publication request: In Vitro Cultivation of a Zoonotic Babesia Sp. Isolated from Eastern Cottontail Rabbits (Sylvilagus Floridanus) on Nantucket Island, Massachusetts

Submitted to: Journal of Clinical Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 11, 2005
Publication Date: July 1, 2005
Citation: Holman, P.J., Spencer, A.M., Droleskey, R.E., Goethert, H.K., Telford III, S.R. 2005. In vitro cultivation of a zoonotic Babesia sp. isolated from eastern cottontail rabbits (Sylvilagus floridanus) on Nantucket Island, Massachusetts. Journal of Clinical Microbiology. 43:3995-4001.

Interpretive Summary: Babesia are a type of parasite that live inside red blood cells. They are transmitted by the bite of an infected tick. Most of these parasites are found only in animal red blood cells. There are cases, however, where humans have been infected with these parasites and have become sick. Much work has gone into determining the animal source of the parasites that cause disease in humans. This paper shows that in several cases of human disease, the Babesia in their red blood cells is the same as that found inside the red blood cells of cottontail rabbits on Nantucket Island, MA. The ticks on this island that bite rabbits and transmit the parasite are also found in most of the eastern half of the US. This observation leads to the possibility that people can be bitten by infected ticks in a larger portion of the US than previously thought.

Technical Abstract: A Babesia sp. found in eastern cottontail rabbits (Sylvilagus floridanus) on Nantucket Island, Massachusetts, is the same organism that caused human babesiosis in Missouri and Kentucky in the basis of morphology and identical small subunit ribosomal RNA (SSU rRNA) gene sequences. Continuous cultures of the rabbit parasite were established from infected blood samples collected from two cottontail rabbits live-trapped on Nantucket Island. HL-1 medium or MEM Alpha medium supplemented with 20% human serum best supported in vitro propagation of the parasite in human or cottontail erythrocytes, respectively. Parasite growth was not sustained in domestic rabbit erythrocytes or in medium supplemented with domestic rabbit serum. The cultured parasites were morphological indistinguishable form the Kentucky human isolate. Transmission electron microscopy revealed similar fine structure of the parasite regardless of host erythrocyte utilized in the cultures. Two continuous lines of the zoonotic Babesia sp. were established and confirmed to share identical SSU rRNA gene sequences with each other and with the Missouri and Kentucky human Babesia isolates.