The Susceptibility of African Wild Animals to Yellow Fever

I. Monkeys

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Tests of susceptibility to yellow fever virus were made in Perodicticus potto ibeanus and Galago crassicaudatus lasiotis. The potto was found to be susceptible, in that the virus propagates in it and is present in its blood in considerable quantity for several days. The galagos were even more highly susceptible, exhibited circulating virus in higher titre and about half of them died of the disease. It was found that they may be infected by a dose of virus which is much too small to cause specific infection in white mice. Yellow fever virus was transmitted from one galago to another by the bites of 2 Aëdes africanus. Naturally-acquired immunity to yellow fever was found in galagos captured in the coastal area of Kenya Colony. The results indicate that some species of this genus may be of considerable importance in the epidemiology of extrahuman cycles of the disease.

About 50 per cent of infected galagos exhibit an emerald green coloration of the serum for 2 to 5 days, coinciding roughly with the period of circulating virus.

The lesions induced by yellow fever virus in galagos, although similar in the gross to those in man and rhesus monkeys, differ in their microscopic aspects. Neither inclusion bodies nor acidophilic necrosis of hepatic cells were observed in them; the microscopic lesions are therefore less conspicuous in galagos.