The genus is distinguished on the basis of genetic characters. The 2B and 3C proteins of erboviruses have exceptionally large chain lengths (283 and 251 aa, respectively).
No surface morphology is visible by EM.
Physicochemical and physical properties
Equine rhinitis B virus (ERBV) has a buoyant density in CsCl of 1.41–1.45 g cm-3. pH stability is variable; ERBV-1 and ERBV-2 are labile below pH 5.0 while ERBV-3 is stable over a wide pH range (2.2–8.0). ERBV is rapidly inactivated by heating at 50°C but divalent cations stabilize against thermal inactivation.
Genome (Wutz et al., 1996): c. 8,828 nt (5′-UTR: up to 905 nt; ORF: 7,752–7,770 nt; 3′-UTR: 164 nt). The IRES is of type II. No pseudoknots have yet been identified within the 5′-UTR. The location of the cre has not been identified.
Genome organization and replication
The deduced polyprotein is of 2,583–2,589 amino acids. No evidence for alternative sites of initiation of protein synthesis is available as is found in the aphthoviruses. The L protein appears to be a proteinase, but has only 23% and 18% aa sequence identity to the L proteins of foot-and-mouth disease virus (FMDV, genus Aphthovirus) and equine rhinitis A virus (ERAV, genus Aphthovirus) respectively. 2A is a short FMDV-like polypeptide (NPG↓P).
ERBV causes upper respiratory tract disease in horses, with a viraemia and faecal shedding. Infections may be persistent.
Derivation of names
Erbovirus: from equine rhinitis B virus
Species demarcation criteria
There is only a single species in the genus.