Colorado Tick Fever

[摘要] 1. 1. Four strains of Colorado tick fever virus were adapted to dilute brown agouti mice by intracerebral inoculation. Three of the above strains had been adapted previously to hamsters, while one strain was adapted directly from a human blood sample. One of the strains was carried through 50 consecutive mouse brain passages.2. 2. Virus could be demonstrated in the blood of mice by the first day after inoculation, reaching maximal level on the third day. The concentration of the virus in brain tissue showed gradual rise with maximal level on the fifth day post inoculation. Virus was present in all tissues tested but the greatest concentration was observed in the central nervous system and the lowest in the serum.3. 3. Mice 8 days of age are fully as susceptible to infection by intraperitoneal route as are 28-day old mice to intracerebral inoculation. Resistance to intraperitoneal inoculations of virus begins to manifest itself in 14-day old mice.4. 4. Neutralization tests with Colorado tick fever virus and antisera prepared against thirteen different viral and rickettsial agents indicated the immunological individuality of Colorado tick fever virus.5. 5. Of the various species of animals tested for susceptibility to Colorado tick fever virus, it was shown that hamsters succumb to infection, while cotton rats and opossums circulate the virus in their blood but sheep and rabbits do not.6. 6. The virus is readily filterable as indicated by the fact that the difference in titers between filtered and unfiltered suspensions of Colorado tick fever virus never exceeded 5–10 LD50, which falls within the limits of experimental error.7. 7. On the basis of rough estimation the virus has a diameter of 35 to 50 millimicrons.8. 8. The virus remains viable at room temperature for more than 64 days, but less than 100 days, and remains quite stable when kept in the frozen or lyophilized state.

[学科分类] 生物科学（综合）