Attempts to Transmit Poliomyelitis Virus to Rodents. ∗

Although a variety of animals have in the past been injected with the virus of poliomyelitis with the intent to infect them, only a few species of primates have without question been successfully infected. Most experimental work reported has been done either with Macacus mulatta, (rhesus), M. irus (cynomolgus) or chimpanzees. These animals are expensive and as a consequence much important experimental work has been neglected because of the prohibitive cost.

Recently, renewed search for a cheaper, suitable, experimental animal was undertaken by several investigators, among them, Armstrong of the National Institute of Health and ourselves. For the most part rodents have been used in these experiments and our results with 25 strains of virus have been negative with all species tested with the exception of the Antelope ground squirrel which occasionally developed questionable neurologic symptoms but which we cannot state definitely were caused by poliomyelitis virus. Armstrong, 1 on the other hand, reports successful infection of the cotton rat, Sigmodon hispidus hispidus, with a strain of virus from Lansing, Michigan.

Table I gives a summary of recent attempts on our part to infect Sigmodons as well as several other species of rodents, both with Los Angeles strains of poliomyelitis virus and with the Armstrong virus.

It will be seen from the table that: (1) Rodents of the genera listed have been refractory to inoculation with a number of strains of poliomyelitis virus collected in Los Angeles. (2) These same animals are subsequently susceptible to inoculation with the Armstrong virus.

It is known that rodents occasionally harbor natural infectious neurotropic viruses, e.g., lymphocytic choriomeningitis has been isolated from white mice, and Theiler 2 , 3 and Olitsky 4 , 5 report natural infections in mice of an encephalomyelitis virus, which produces typical paralytic symptoms.