Fleas are ectoparasitic blood-sucking insects with the ability to jump, which commonly infest wild and domestic animals (mainly dogs and cats) but also humans.
Besides Yersinia pestis (see plague) the Yersinia group of bacteria also includes two species frequently causing illness (mainly enteritis) in humans; Yersinia enterocolitica and Yersinia pseudotuberculosis.
Cholera is an acute diarrhoeal infection caused by the bacterium Vibrio cholera of serogroups O1 or O139. Humans are the only relevant reservoir, even though Vibrios can survive for a long time in coastal waters contaminated by human excreta.
Cryptosporidia are intestinal parasites infecting a variety of animals (e.g. cattle, sheep, rodents, cats and dogs, but also birds, fish and reptiles). Human infections occur due to Cryptosporidium parvum, a species that also affects domestic animals.