Serial Passage of the Human Influenza Virus in the European Hamster (Cricetus cricetus),

The study of viruses pathogenic for man is largely dependent on having an animal host suitable for experimentation. So far in the study of human influenza, ferrets and mice have proved to be best suited to this purpose, although both animals are far from being ideal. A number of others such as the hedgehog, 1 white rat, guinea pig 2 guinea pig foetus, 3 Chinese mink, and David's squirrel 4 have been shown to be susceptible only to varying degrees. However, search for additional suitable animals is being continued by most investigators engaged in the study of viruses, and the purpose of the present communication is to report briefly the results of the attempts to infect the European hamster (Cricetus cricetus) † with influenza virus.

The strain of virus employed in these experiments was obtained 4 months previously from a person suffering from a rather typical attack of influenza. This virus had been identified immunologically as belonging to the group of human influenza viruses. In ferrets it produced characteristic symptoms but no lung lesions.

The following procedure was adopted: In each passage 2 hamsters were inoculated intranasally with 0.5 cc of virus suspension while under ether anesthesia. One of the animals was sacrificed on the 4th day, and 20% suspensions in broth-saline solution of the turbinates and lungs were prepared separately for subinoculation to mice and for transfer to the 2 hamsters of the succeeding passage. The second hamster in each passage series was held for determination of immunity response. Blood was drawn from the heart preceding, and 2 weeks following, inoculation, and the serum was tested quantitatively for neutralizing antibodies. Thus in each passage effort was made to determine the existence of infection by the recovery of the virus in mice and by a rise in the circulating antibodies.