Effect of route of inoculation on histopathological changes induced in mice by dugbe virus (a Nigerian tick-borne virus).

The effect of the route of inoculation of Dugbe virus (a Nigerian tick-borne virus) in baby mice was investigated. Striking differences were observed in the onset of morbidity, organ virus titres at the terminal stages of the infection, the pathology of the various organs and the haematological picture, depending upon whether the animals were infected intracerebrally (i.c.) or intraperitoneally (i.p.). Mice infected i.c. became moribund 2-3 days earlier than those infected i.p. Furthermore, the virus titres of the various organs were generally higher by 1-2 log in the former group of mice. The most distinguishing feature of the brain pathology of i.p. inoculated mice was the presence of intranuclear inclusion bodies in the neurons of the hippocampus. In contrast, there were no inclusions after i.c. inoculation. There was depletion of mature lymphocytes from germinal centres of the spleen in i.c. inoculated mice, whereas in the i.p. inoculated mice there was lymphoid hyperplasia. At the terminal stages of i.c. infection there was a tremendous increase in neutrophils, while in i.p. inoculated mice there was an increase in plasmacytoid lymphocytes. Anaemia was another haematological feature of i.p. inoculated mice; on the other hand, there was no anaemia in i.c. inoculated mice.