Neospora caninum is an invalid species name: an evaluation of facts and statements

Abstract

An evaluation of both the formal requirements of the International Rules of Zoological Nomenclature and the scientific reasons for the description of new genera and species shows that the name Neospora caninum is a nomen nudum. The only characteristic criteria for discriminating between the previously described species Hammondia heydorni and the proposed new species N. caninum (i.e. the lack of a parasitophorous vacuole) has been shown to be wrong in many publications. Furthermore, absolutely no criteria were presented as to why a new genus (i.e. Neospora) should be established besides the already existing genera Hammondia, Toxoplasma and Isospora. In addition, recent transmission experiments show that an oocyst isolate (from the faeces of dogs) is morphologically indistinguishable from H. heydorni [synonymous with Isospora bigemina - small form, Isospora heydorni (Tadros and Laarman 1976) and H. heydorni (Tadros and Laarman 1976) Dubey 1977] and is almost identical with respect to molecular biological features with the NC-1 strain of N. caninum.

Effects of toltrazuril and ponazuril on Hammondia heydorni (syn. Neospora caninum ) infections in mice

“…Neospora caninum is an apicomplexan parasite that is identical to Hammondia heydorni ( Schares et al 2001a( Schares et al , 2001bHeydorn and Mehlhorn 2002;Mehlhorn and Heydorn 2003). This parasite has often been found in cases of abortion and severe neuromuscular disease in fetal cattle and dogs.…”

Electron microscopic study of in vitro cultures of Hammondia heydorni (Berlin 1996) tachyzoites after passages through dogs, mice, rats, guinea pigs and jirds

“…In contrast to these isolates, all isolates forming slightly larger oocysts with a diameter ‡10 lm show high conformity in all aspects with the 1988 isolate of Blagburn et al (Speer et al 1988;Speer and Dubey 1989b;Ellis et al 1999; Ellis and Pomroy cited by Dubey et al 2002a;Dubey et al 2002aDubey et al , 2002bHeydorn and Mehlhorn 2002). Thus, they belong to the second small coccidian species of the dog.…”

“…Thus, they belong to the same group of oocysts described by Heydorn (1973) and Schares et al (2001aSchares et al ( , 2002. All investigated isolates forming oocysts with a diameter smaller than 10 lm show high conformity in morphological, biological, serological and molecular biological characteristics with the NC-1 and NC-beef strains of Dubey's N. caninum (Heydorn 1973;McAllister et al 1998;Lindsay et al 1999;Mu¨ller et al 2001;Schares et al 2001aSchares et al , 2001bDubey et al 2002aDubey et al , 2002bHeydorn and Mehlhorn 2002). Thus, they have to be considered as members of the same species.…”

“…It produced low numbers of oocysts of which the smallest measured 10.4·9.4 lm in size. It could also not be distinguished from the almost identical NC-1 strain of Dubey's N. caninum, as shown in transmission and molecular biological experiments (Mu¨ller et al 2001, Schares et al 2001a, 2001bHeydorn and Mehlhorn 2002).…”

“…In this paper, the size of oocysts was uncritically not referred to the original description of Heydorn (1973) or to that of the species description of Tadros and Laarman (1976), but was based on data given by Levine and Ivens (1965) and Dubey and Fayer (1976). This led to the doubtful application of the name Hammondia heydorni to all small coccidian oocysts which were isolated from the faeces of dogs worldwide, without any true comparison of the different isolates until the description of oocysts of the incorrectly named Neospora caninum (Dubey 1993;Dubey et al 2002a;Heydorn and Mehlhorn 2002). The most important error leading to the recent confusion in naming the two distinct small coccidian species of dogs (Dubey et al 2002b) was made by Dubey, who as author or co-author of several papers arbitrarily considered and still considers an oocyst isolate of Blagburn et al (1988) as the ''type or reference material'' for H. heydorni.…”