Colorado Tick Fever: Prolonged Viremia in Hibernating Citellus Lateralis

Richard W. Emmons Viral and Rickettsial Disease Laboratory, California State Department of Public Health, Berkeley 4, California

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Sixteen Citellus lateralis ground squirrels were infected with Colorado tick fever virus and placed at 4°C. Seven animals hibernated well, and four of these had viremia when removed from the cold 110 to 124 days later. In three animals, viremia persisted for 11, 17, and 47 days after removal from the cold. The total viremic periods were 127, 133, and 160 days. Neutralizing antibody was demonstrated in a larger proportion of the poor hibernators than of the good hibernators. Limited attempts to infect Dermacentor andersoni nymphal ticks by feeding them on animals with post-hibernation viremia were unsuccessful.

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