I looked, and behold, an ashen horse; and he who sat on it had the name Death; and Hades was following with him. Authority was given to them over a fourth of the earth, to kill with sword and with famine and with pestilence and by the wild beasts of the earth.
-- Revelation 6:8 (NASB)
Setting aside for a moment the fact that most of Revelation is obviously highly symbolical, the question might naturally arise whether wild beasts are really the threat. After all, the European Cave Lion is now extinct, and we have hunted most of the big predators to the point where they are endangered species in very real risk of extinction. The idea of thousands of grizzly bears descending on New York City, or of thousands of leopards chasing people through the streets of Paris, or of thousands of crocodiles making the streets of Sidney run red sounds like a really bad movie, not a serious possibility.
But then, the text does not say bears or leopards or crocodiles, only "wild beasts". If we back away from our preconceptions just a bit, it is easy to see that "wild beasts" can still pose a problem today. Feral dogs have posed a problem throughout history, and coyotes are expanding in North America. Rats have carried the fleas that brought the Black Death, bats can carry rabies, and armadillos -- also spreading in North America -- can spread leprosy to humans.