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Dear Sir:
We were disappointed to see the continued use of the name Heligmosomoides polygyrus in experimental studies using the model gastrointestinal nematode parasite maintained in laboratory mice, as in the recent paper in the American Journal of Tropical Medicine and Hygiene by Tetsutani and others.1 This parasite is now more properly known as Heligmosomoides bakeri. This conclusion is not based on an arbitrary, taxonomic, nomenclature judgment, but on a detailed molecular study by Cable and others,2 which showed conclusively that the laboratory model organism is not closely related to the nematode from wood mice (Apodemus spp.) that was originally described as H. polygyrus and has priority for this name.
There is a large body of literature in support of this conclusion. The history of the debate about what to call the laboratory-maintained parasites is long, going back to the early 1900s. This debate was originally muddled by the debate over the continued use of Nematospiroides dubius in some laboratories and H. polygyrus in others.3 When Ehrenford4 originally cultured a nematode from Peromyscus maniculatus gambeli in California, he identified it as the European species because of its morphologic similarity.4–6 However, there have always been concerns that the American species maintained in laboratory mice (Mus spp.) is different from the European species from wood mice. The American species has a different morphology7 and many molecular differences;8,9 reciprocal cross-infections fail without immunosuppressive treatment.10
There have always been suspicions that the laboratory model is fundamentally different from the species occurring in wild mice. Durette Desset and others7 and Tenora and Barus11 established them as distinct subspecies. However, the work of Cable et al.2 and Nieberding and others12,13 makes it clear that these species are not closely related, but have different ribosomal DNA and mitochondrial DNA sequences that differ as much from each other as they do from other valid species of the genus (e.g., Heligmosomoides glareoli).
Tenora and others14 suggested that the two organisms should be raised to full species status but provided little supporting evidence. However, Cable and others2 then provided the key novel molecular data and raised the subspecies (H. p. polygyrus and H. p. bakeri) to the status of full species, which was reflected in their status as two distinct species derived from different (unrelated) hosts in different parts of the world. Following international rules for nomenclature, the parasite from wood mice has priority for the name H. polygyrus.
We realize that there are many publications in the public domain reporting experiments in which the laboratory mouse–maintained parasite is referred to as H. polygyrus, but this is no longer acceptable. We considered the impact this name change would have on the international community working on the laboratory model system, but the differences between H. bakeri and H. polygyrus are so substantial that they override any plea for nomenclatural stability. We would have expected immunologists who are familiar with frequent changing of the names of molecular markers on their cells as new information becomes available to be less resistant to changing the name of a parasite in which molecular systematics and taxonomy have shown a clear difference in species. Systematics and taxonomy are also legitimate sciences in their own right and parasites, like molecules, need to be renamed and reclassified when new data become available.
We believe that three years after the renaming of the laboratory-maintained intestinal parasite of mice as H. bakeri, it is time for everyone to conform to the International Code for Zoological Nomenclature. The parasite maintained in laboratory mice is H. bakeri, and the name H. polygyrus is reserved for the organism that infects wild wood mice (Apodemus spp.) in the Palaearctic.
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