Consistency in use of terminology is an important requirement for clear communication in any field of science. In contrast to the basically homogeneous terminology of bacterial and fungal diseases, in the nomenclature of parasitic diseases or infections different names are being used with varying frequency for denoting the same disease entity, such as trypanosomosis and trypanosomiasis, fasciolosis and fascioliasis, etc. The existing usage of inconsistent disease terminology induced the World Association for the Advancement of Veterinary Parasitology to initiate codification of simple rules of formation of names to denote parasitic infections. This guideline was published in 1988 as the Standardised Nomenclature of Animal Parasitic Diseases (SNOAPAD)¹. Though the SNOAPAD initiatives were originally meant for those working in veterinary parasitology, the proposal was found sensible, and endorsed in 1990 by the World Federation of Parasitologists for adoption for all parasitic infections. Therefore, the reference to 'Animal' was dropped, thereby changing the acronym to SNOPAD². An overview of the SNOPAD history, and a study on the impact of the use of different disease names as database-search terms on yields of data are presented in two recent publications^3,4.

In the following the principles of SNOPAD are briefly summarized.

1. When disease names are formed from the taxonomic name of the parasite, of the suffixes -asis, -iasis used for describing a disease or infection should be discontinued, only the suffix -osis (in plural -oses) should be used.
2. Another major source of nomenclatural heterogeneity originates from the variation in the stem of words which are formed either from the nominative (eg. trypanosomosis, hypodermosis) or from the Greek genitive (eg. trypanosomatosis, hypodermatosis). For uniform usage SNOPAD offers a simple solution by proposing that the suffix -osis be added to the stem of the name of the parasite taxon, which, in general, is formed from the nominative case of the taxa by the omission of the last one or two letters (eg. Trypanosoma, trypanosomosis, Sarcocystis, sarcocystiosis, Fasciola, fasciolosis, Trichostrongylidae, trichostrongylidosis, Ascaris, ascariosis, Trichinella, trichinellosis, Hypoderma, hypodermosis).
3. When taxa end with -x in the nominative the stem is formed from the genitive and the disease name is derived from the stem of the genitive (eg. Endolimax, endolimacos, endolimacosis, Pulex, pulicos, pulicosis).
4. In some cases, the disease name is formed by adding the suffix -osis to the full name of the parasite taxon (eg. Hepatozoon, hepatozoonosis, Multiceps, multicepsosis, Loa, loaosis, Dermacentor. dermacentorosis, Argas, argasosis, Acarapis, acarapisosis).
5. Well-established vernacular disease names, not coined from the taxonomic name of the parasite, can also be used as alternatives to the related terms offered by SNOPAD. Examples of such names include sleeping sickness, Chagas' disease, nagana, malaria, East Coast Fever, hydatidosis, cysticercosis, visceral larva migrans, mange, scabies, myiasis, etc.
6. Disease names can also be formed by using formulas such as 'infection with', 'infection due to' or 'infection caused by' to which the name of the causative agent is added (eg. infection caused by Echinococcus granulosus).

For further details the original guideline should be consulted which contains a taxonomic and an alphabetic list of 374 standard names of parasitic diseases¹.

References:

1. Kassai, T., Cordero del Campillo, M., Euzeby, J., Gaafar, S., Hiepe, Th., Himonas, C. A., 1988. Standardized Nomenclature of Animal Parasitic Diseases (SNOAPAD). Veterinary Parasitology. 29, 299-326.
2. Kassai, T., Burt, M.D.B 1994. A plea for consistency. Parasitology Today. 10, 127-128.
3. Kassai, T.: Nomenclature for parasitic diseases: cohabitation with inconsistency for how long and why? Review. Vet. Parasitol., 138 2006. (3-4.) 169-178.
4. Kassai, T.: The impact on database searching arising from inconsistency in the nomenclature of parasitic diseases. Short communication. Vet. Parasitol., 138. 2006. (3-4.) 358-361.