Though often overlooked by the layperson due to their diminutive size, protists are amongst the most abundant organisms on the planet. The term protist encompasses both the animal and plant varieties, as well as some that are hard to categorize as one or the other.
Of the 30,000 known animal protists, roughly 30 per cent are parasitic. Some of these protists have only a slight affect on their hosts, infecting only a specific type of animal thus keeping contamination to a minimum. However, there is a minority of animal protists that pose a great risk to human public health, not only due to the severity of the symptoms they induce and high fatality rates, but also due to the rapid way they can be spread amongst different carriers. When these carriers are cattle on which a nations economy depends, this opens up a whole new array of problems…(short extract)