Genus Ephemerovirus

Type Species	Bovine ephemeral fever virus	(BEFV)

Distinguishing Features

Virions are bullet- or cone-shaped with a length of ~ 140-200  nm and diameter ~ 60-80  nm. Virions have a buoyant density in CsCl of 1.19  g/cm³ and sedimentation coefficient of 625S. The virus is sensitive to acid or alkali and most stable at pH 7.0-8.0.

Bovine ephemeral fever virus (BEFV) particles contain at least five structural proteins, designated: L (Mr 180 10³); G (Mr 81 10³); N (Mr 52 10³); P (Mr 43 10³); and M (Mr 29 10³). The G protein is a virus membrane-associated glycoprotein which contains 5 potential sites for attachment of N-linked glycans. The N protein is phosphorylated. The M protein is also phosphorylated in virions. In addition to these proteins, a Mr 90 10³, non-virion glycoprotein (G_NS) has been identified in BEFV-infected mammalian cells. G_NS is highly glycosylated (8 potential sites for N-linked glycans). The G and G_NS proteins, although not identical, exhibit homologies with each other and to lesser extents with the G proteins of other animal rhabdoviruses. In Adelaide River virus (ARV), the G protein (Mr 90 10³) contains 6 potential sites for N-linked glycans, the G_NS protein contains 9. Two glycoproteins have been identified in mammalian cells infected with Berrimah virus (BRMV).

The 14.9  kb negative sense viral RNA genome of BEFV includes 10 genes in the order 3-N-P-M-G-G_NS-₁-₂---L-5 and intergenic regions of between 26 and 53  nts. The and L genes overlap by 21  nts. Additional small ORFs occur in alternative frames in the P and ₂ genes. Each gene, except ₁, is initiated from a UUGUCC sequence (mRNA: 5-cap-AACAGG . . . ) and terminates at a putative polyadenylation site: GNAC(U_6-7)-3. In ARV, the 14.6  kb genome contains 9 genes in the order 3-N-P-M-G-G_NS-₁-₂--L-5 and intergenic regions of 1-4  nts. The and L genes overlap by 22  nts. ARV lacks a gene comparable to that of BEFV. An additional ORF occurs in an alternative frame in the P gene. Each gene is initiated from a viral 3-UUGUC sequence (mRNA: 5-cap-AACAG . . . ), however the putative polyadenylation signals are more variable than those of BEFV and may account for the synthesis of polycistronic mRNAs. The products of ephemerovirus ₁, ₂, and genes have not been identified. The ₁ gene product appears to be a viroporin but the functions of other products have not been established. Proteins encoded in the ARV ₁, ₂ and genes share homology with the corresponding BEFV proteins.

The G protein of bovine ephemeral fever virus contains 4 distinct neutralization sites. G protein purified from virions or expressed from recombinant vaccinia virus protects cattle from experimental infection. The G_NS glycoprotein does not induce neutralizing antibodies and is not protective.

Biological Properties

Bovine ephemeral fever is an economically important enzootic disease of cattle and water buffalo in most tropical and sub-tropical regions of Africa, Australia, the Middle-East and Asia. BEFV infection causes a sudden onset of fever and other clinical signs including lameness, anorexia and ruminal stasis, followed by a sustained drop in milk production. Although the mortality rate is low (1-2%), it is highest in well-conditioned beef cattle and high producing dairy cattle. The virus is transmitted by and replicates in hematophagous arthropods and has been isolated from both culicoides and mosquitoes.

Other species in the genus are not recognized as animal pathogens, but are known to infect cattle and have been isolated from healthy sentinel cattle (ARV, BRMV) or from insects (Kimberley virus, KIMV; Malakal virus, MALV; Puchong virus, PUCV).

List of Species Parameters in the Genus

Species exhibit low to no cross-neutralization. They cross-react strongly in CF or indirect immunofluorescence tests and may show low level cross-reactions by indirect immunofluorescence with viruses of the genus Lyssavirus. However, sequence comparisons with other rhabdoviruses indicate that in evolutionary terms the ephemeroviruses are closer to members of the genus Vesiculovirus than to those of other defined genera in the family. Analyses of the amino acid sequences of BEFV and ARV proteins indicate highly significant sequence homologies between most of the corresponding proteins, with the higher homologies in the L and N proteins than the G proteins. BEFV and ARV N proteins share 48% amino acid sequence identity. Amino acid sequence data is not available for other species. Only those viruses known to encode both G and G_NS glycoproteins are assigned as defined species.

List of Species in the Genus

Official virus species names are in italics. Tentative virus species names, alternative names ( ), strains or serotypes are not italicized. Virus names, genome sequence accession numbers [ ], and assigned abbreviations ( ) are:

Species in the Genus

Adelaide River virus	[L09206, L09208, U05987, U10363]	(ARV)
Berrimah virus		(BRMV)
Bovine ephemeral fever virus	[M94266, U04166, U18106, U72399]	(BEFV)

Tentative Species in the Genus

Kimberley virus	(KIMV)
Malakal virus	(MALV)
Puchong virus	(PUCV)