Susceptibility of Rodents ( Myospalax fontanieri ) to Experimental Infection with Rickettsiae of Chinese Typhus

Abstract

In general, guinea pigs have served satisfactorily as the experimental animal in the study of rickettsial diseases. However, when dealing with the European type of typhus fever, which occurs locally, these animals presented certain disadvantages. The only clinical manifestation of this disease in guinea pigs is a more or less typical period of fever following an average interval of incubation. With the possible exception of the finding of Durand, 1 who used a special technique, their blood serum has not been found to agglutinate proteus X₁₉. So unless one uses the rarely obtainable rickettsial emulsion as the antigen, there can be no positive serological evidence of this infection. The study of histological lesions would necessitate the sacrifice of the animals which is often undesirable. Rabbits have been used to obtain a positive Weil-Felix reaction, but even then, the titre is usually low and is, therefore, often inconclusive. Rats give only an inapparent infection. Recently the ground squirrel or “Zieselmaus” has been independently 2 , 3 found to be extremely susceptible to the European type of typhus. As many as 70% of the animals infected die from this disease. However, the blood serum of this animal also failed to give a positive Weil-Felix reaction. It was for the purpose of finding another laboratory animal in which these difficulties might be circumvented that led us to make a study of a local species of rodent (Myospalax fontanieri), Milne-Edwards; the following is a brief report of our results.