Summary

Eastern equine encephalitis virus can be ingested in large amounts by the mites Haemogamasus liponyssoides and Ornithonyssus bacoti through feeding on the blood of infected hosts. As shown by mouse inoculation, the virus persisted in H. liponyssoides at room temperatures about 24 hours and at 42°F for as long as 11 days with a progressive drop in titer from 104.5 LD50/0.03 ml i.c. on day 1 to 101.5 on day 8. In O. bacoti held at room temperature, the virus persisted for 7 days, while at 42°F it was recoverable for 46 days. In this mite, the titer of the virus fluctuated roughly between 103 and 105 LD50/0.03 ml i.c. over the 46-day observation period without significant increase or decrease. Since no increase in virus was observed, it is probable that the mite-virus relationship is not biological at these temperatures.

Virus transmission by bite was not demonstrated. Transmission to suckling mice was achieved through contamination of abraded skin and nasal mucosa with a suspension of triturated mites. Individual infected mites inserted under the skin of suckling mice produced infection in a high percentage of attempts. No infection occurred when 21-day-old mice ingested numbers of infected mites.