In this genomic era when researchers are forever hunting for cryptic and hidden species, which differ ever so slightly from a well-established species, it is an extremely rare for someone to describe a new nematode from a common terrestrial mammalian host. Rojas et al. have done just that in a new article published in the journal 'Parasitology', and have successfully described and named Spirocerca vulpis from the red fox (Vulpes vulpes). Similar worms from the stomachs of red foxes have been reported in the past by Diakou et al. in Greece and Al-sabi et al. in Denmark, but had not been elevated to species status before.
When veterinary students are taught about the spirurids that reside in the GI tract, they are taught about a fascinating creature called Spirocerca lupi, an inhabitant of the oesophagus of canines and felines. Spirocerca lupi causes granulomas in the oesophagus and scarring of the aorta. The esophageal granulomas can become neoplastic and transform into fibrosarcomas and osteosarcomas. Migrations of the S. lupi away from the esophagus into other organs of the body can also occur rarely.
The new worm described by Rojas et al. differs morphologically from Spirocerca lupi . It is also located in a different predilection site - the stomach, while Spirocerca lupi is found in the esophagus. The authors report that a significant proportion (22%) of the fox population of Spain harbor smooth surfaced gastric nodules caused by Spirocerca vulpis, with one fox harboring a nodule in the pericardium. Spirocerca vulpis causes granulomas in the serosa or the wall of the stomach that grossly are grey-brown, smooth surfaced and surrounded by a zone of hyperemia. The adult worms live inside these nodules and are surrounded by an exudate. Worms of both sexes are reported to have six anteriorly projecting teeth and the females have embryonated eggs that resemble those of S. lupi. The oesophagus, which is a diagnostic feature in nematodes, is described as being cylindrical and muscular anteriorly and being glandular posteriorly. Analysis of the mitochondrial cox1 gene of the genus Spirocerca and closely related Cylicospirura and Protospirura revealed that S. vulpis was significantly different from S. lupi and the others.
In addition, Rojas et al. in another paper titled "Phylogenetic analysis of Spirocerca lupi and Spirocerca vulpis reveal high genetic diversity and intra-individual variation" show that each individual worm in the genus Spirocerca has high individual variation in the nuclear ITS-1 locus, which is a compelling finding. It is well known that the internal transcribed spacers are multi-copy genes, with Ascaris possessing upto 40 copies per individual cell. It is also known that intra-individual variability exists in the ITS1 genes of Ascaris, as shown by Leles et al. in 2010. While Ascaris has 2-4 genotypes per individual, Spirocerca has unto 6 different ITS1 genotypes per individual.
Every new species that is described needs to be submitted to a collection for archival purposes. The type specimens for Spirocerca vulpis may be found in the National Natural History Collection of the Hebrew University of Jerusalem in Israel. It is now a valid species and you might find it in print as Spirocerca vulpis sp. nov., with 'sp. nov.' indicating that is a 'species novae' or a new species in the existing genera Spirocerca.
Some things to be gleaned from the papers are that (1) the species appears to be host restricted to red foxes (Vulpes vulpes), but it is unknown if other carnivores can be affected as no cross-transmission studies have been done yet. (2) It has also not yet been found/reported in North America, but an absence of a report is not always an indication of absence of existence in parasitology. (3) Both species of the genus Spirocerca are not known to be zoonotic. (4) Diagnosticians must add S. vulpis to their differentials list if they find a Spirocerca egg in red fox fecal samples.
References:
Rojas, Alicia, et al. "Spirocerca vulpis sp. nov.(Spiruridae: Spirocercidae): description of a new nematode species of the red fox, Vulpes vulpes (Carnivora: Canidae)." Parasitology(2018): 1-12.
Diakou, Anastasia, et al. "First report of Spirocerca lupi infection in red fox Vulpes vulpes in Greece." Wildlife biology18.3 (2012): 333-336.
Al-Sabi, Mohammad Nafi Solaiman, et al. "Genetically distinct isolates of Spirocerca sp. from a naturally infected red fox (Vulpes vulpes) from Denmark." Veterinary parasitology 205.1-2 (2014): 389-396.
Rojas, Alicia, et al. "Phylogenetic analysis of Spirocerca lupi and Spirocerca vulpis reveal high genetic diversity and intra-individual variation." Parasites & vectors 11.1 (2018): 639.
Leles, Daniela, et al. "ITS1 intra-individual variability of Ascaris isolates from Brazil." Parasitology international 59.1 (2010): 93-96.
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