The nematodes are, after the insects, the group of organisms with the largest number of species identified. They include members of great medical, veterinary and agricultural significance, making this group one of the most important animal parasites. However there are many gaps in our knowledge of them. For example, there is still not a single nematode species for which we have detailed knowledge of feeding, digestion and nutritional requirements, showing that there are still many aspects to be learned about nutrition in nematodes. Our understanding of the process of protein digestion, a very important function in the biology of any organism, is still poor since our knowledge is composed of fragmentary data for different groups of nematodes. It is believed that peptidases are essential during the development process and in the most critical moments of parasite-host interactions, and are thus directly involved with the growth and survival of the parasite. Their identification and characterization are important for basic understanding of the biology of the parasite, and their relevance to parasitic nematodes as virulence factors is clear. Consequently, peptidases are currently viewed as potential targets for vaccines, drugs and serodiagnosis. Despite this, in most cases, the precise physiological functions of peptidases in parasites are not known.
