Not-So-Novel Michigan Rabbit Calicivirus | CDC EID

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Volume 16, Number 8–August 2010
Letter
Not-So-Novel Michigan Rabbit Calicivirus

To the Editor: A disease outbreak in a Michigan rabbitry led Bergin et al. (1 ) to identify a new rabbit calicivirus distinct from rabbit hemorrhagic disease virus, which they designated as Michigan rabbit calicivirus (MRCV). They found that in domestic rabbits from the United States, 2 different forms of rabbit calicivirus with differences in pathogenicity are circulating. Bergin et al. showed that, phylogenetically, MRCV was more closely related to the nonpathogenic rabbit calicivirus (RCV) than to pathogenic strains and used this observation as an argument for its classification as a novel calicivirus. However, they did not include the publicly available sequences of other nonpathogenic strains, such as Ashington (97% of the capsid viral protein [VP] 60) and the newly identified Lagovirus spp. RCV-A1 (complete genome) (2 ).

Using the same dataset as Bergin et al. and including these sequences, we performed genetic analyses focusing mainly on the capsid VP60. The lack of information for open reading frame 1 for the nonpathogenic strains led to this option. Independently of the sequences’ length, RCV-A1 was more closely related to the Lagovirus spp. European brown hare syndrome virus, here used as an outgroup, and clearly apart from a highly supported primary group that was further subdivided into 2 also highly supported subgroups, 1 composed of pathogenic rabbit hemorrhagic disease virus strains and another encompassing the RCV-like group (RCV, Ashington and Lambay (2 ), and MRCV). Here, only the phylogenetic tree that corresponds to the more complete VP60 sequences is shown (Figure).

We conclude that MRCV is not a novel calicivirus but a new variant of the nonpathogenic RCV-like group. However, the low pathogenicity presented by MRCV and the presence of viral RNA in the liver rather than in the intestine are clearly new features among the nonpathogenic RCV-like group (5 ).

This work was supported by Foundation for Science and Technology Portugal grants SFRH/BD/31048/2006 and SFRH/BPD/27021/2006 to J.A. and P.J.E., respectively.
Joana Abrantes and Pedro J. Esteves
Author affiliations: CIBIO-UP (Centro de Investigação em Biodiversidade e Recursos Genéticos, Vairão –Universidade do Porto, Porto, Portugal (J. Abrantes, P.J. Esteves); Institut National de la Santé et de la Recherche Médicale (INSERM), Unité 892, Université de Nantes, Nantes, France (J. Abrantes); and CESPU (Cooperativa de Ensino Superior Politécnico e Universitário), Gandra, Portugal (P.J. Esteves).

References
1.Bergin IL, Wise AG, Bolin SR, Mullaney TP, Kiupel M, Maes RK. Novel calicivirus identified in rabbits, Michigan, USA. Emerg Infect Dis. 2009;15:1955–62. PubMed DOI: 10.3201/eid1512.090839
2.Strive T, Wright JD, Robinson AJ. Identification and partial characterisation of a new lagovirus in Australian wild rabbits. Virology. 2009;384:97–105. PubMed DOI: 10.1016/j.virol.2008.11.004
3.Saitou N, Nei M. The neighbor-joining method: a new method for reconstructing phylogenetic trees. Mol Biol Evol. 1987;4:406–25. PubMed
4.Tamura K, Dudley J, Nei M, Kumar S. MEGA4: Molecular Evolutionary Genetics Analysis (MEGA) software version 4.0. Mol Biol Evol. 2007;24:1596–9. PubMed DOI: 10.1093/molbev/msm092
5.Capucci L, Fusi P, Lavazza A, Pacciarini ML, Rossi C. Detection and preliminary characterization of a new rabbit calicivirus related to rabbit hemorrhagic disease virus but nonpathogenic. J Virol. 1996;70:8614–23. PubMed
Figure
Figure. Evolutionary relationships of Lagovirus strains. The evolutionary history was inferred by using the neighbor-joining method (3) with the pairwise deletion option...

Suggested citation for this article
Abrantes J, Esteves PJ. Not-so-novel Michigan rabbit calicivirus [letter]. Emerg Infect Dis [serial on the Internet]. 2010 Aug [ date cited].
http://www.cdc.gov/EID/content/16/8/1331.htm

DOI: 10.3201/eid1608.091803

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