These results show that the South African strain of dourine like the
chronic form of the disease in other countries is not readily transmitted to
laboratory animals. But where the invasive power of the strain has been
boosted by serial blood passage in equines it is easily transmitted to rabbit
testicles and to white rats provided the rats are splenectomised.
The rabbit-adapted parasite remains localised and shows little tendency
to enter the blood stream. In the splenectomised white rat, the parasites
rapidly increase in virulence and are soon adapted to normal white rats.
The strain has been passaged over 50 times in normal white rats. Guinea
pigs and rabbits, are resistant. The strain differs in this respect from our
imported one which is virulent for these animals. What part bartonellosis
plays in rendering splenectomised rats susceptible to the disease is not known.
Both the rabbit-testicle and rat-adapted parasites were indistinguishable
morphologically from the original strain, and from our imported strain. An
antigen prepared from the rat strain gave the same results as our routine
antigen when tested against sera from normal and dourine infected horses.
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