Cryptobia (Trypanoplasma) salmositica is a haemoflagellate that causes morbidity and mortality in salmon, Oncorhynchus spp, on the Pacific coast of North America. In this review, Patrick Woo briefly describes the pathogen, its transmissions (either indirectly via its leech vector, Piscicola salmositica, or directly between fish) and the clinical signs of the disease. He then outlines strategies that have been developed to protect fish against the pathogen, and the mechanism of innate resistance to disease in Cryptobia-tolerant fish. Protective strategies include the breeding of fish that are resistant to infection, and the use of an attenuated C. salmositica strain to protect susceptible fish from disease for at least two years. He ends the review with suggestions for further research that include the use of the leech vector to deliver the vaccine and the development of more novel protective strategies (eg. immunochemotherapy, anti-idiotype vaccine) against cryptobiosis.