Hayes Yard virus: a novel ephemerovirus isolated from a bull with severe clinical signs of bovine ephemeral fever is most closely related to Puchong virus.

Bovine ephemeral fever is a vector-borne disease of ruminants that occurs in tropical and sub-tropical regions of Africa, Asia and Australia. The disease is caused by a rhabdovirus, bovine ephemeral fever virus (BEFV), which occurs as a single serotype globally. Although several other closely related ephemeroviruses have been isolated from cattle and/or arthropods, only kotonkan virus from Nigeria and (tentatively) Mavingoni virus from Mayotte Island in the Indian Ocean have been previously associated with febrile disease. Here, we report the isolation of a novel virus (Hayes Yard virus; HYV) from blood collected in February 2000 from a bull (Bos indicus) in the Northern Territory of Australia. The animal was suffering from a severe ephemeral fever-like illness with neurological involvement, including recumbency and paralysis, and was euthanised. Histological examination of spinal cord and lung tissue identified extensive haemorrhage in the dura mata with moderate perineuronal oedema and extensive emphysema. HYV displayed cone-shaped morphology, typical of rhabdoviruses, and was found to be most closely related antigenically to Puchong virus (PUCV), isolated in 1965 from mosquitoes in Malaysia. Analysis of complete genome sequences of HYV (15 025 nt) and PUCV (14 932 nt) indicated that each has a complex organisation (3' N-P-M-G-GNS-α1-α2-ß-γ-L 5') and expression strategy, similar to that of BEFV. Based on an alignment of complete L protein sequences, HYV and PUCV cluster with other rhabdoviruses in the genus Ephemerovirus and appear to represent two new species. Neutralising antibody to HYV was also detected in a retrospective survey of cattle sera collected in the Northern Territory.

Longitudinal study of the detection of Bluetongue virus in bull semen and comparison of real-time polymerase chain reaction assays.

Infection with Bluetongue virus (BTV) is a significant impediment to the global movement of bovine semen. Repeat testing of blood from donor animals is specified in the World Organization for Animal Health (OIE) Manual for the export of semen from regions where BTV may be present. Screening of blood or semen samples has usually been carried out by virus isolation (VI) either by inoculation of chicken embryos followed by passage onto insect and mammalian cell cultures or in vivo inoculation of sheep followed by serology to detect seroconversion. Direct testing of semen for BTV would enable earlier release of semen samples and avoid repeat testing of the donor, as well as provide an option for releasing batches of semen that were collected without certification of the donor. Quantitative (real-time) reverse transcription polymerase chain reaction (qRT-PCR) assays overcome most of the limitations of other methods and have the potential to provide higher sensitivity. The present study compared 5 qRT-PCR assays, including 2 commercially available kits, for the detection of BTV in semen serially collected from 8 bulls over a period of 90 days after experimental infection. The results of the study show that at least one of the qRT-PCR assays is extremely reproducible and has both very high sensitivity and specificity to reliably detect all available serotypes. The preferred qRT-PCR gave consistently superior results to VI, sheep inoculation, and conventional RT-PCR. Therefore, the assay can be recommended for the screening of bovine semen for freedom from BTV.

A reverse-transcription PCR method for detecting all known ephemeroviruses in clinical samples.

Bovine ephemeral fever virus (BEFV) is an economically important vector-borne pathogen of cattle in tropical and sub-tropical regions of Australia, Asia, Africa and the Middle East. Although clinical cases of bovine ephemeral fever are usually attributed to BEFV, definitive diagnosis is rarely performed and at least two other related viruses, kotonkon virus (KOTV; an ephemerovirus) and Fukuoka virus (FUKAV; an unassigned rhabdovirus), can cause similar clinical signs. As vaccines have been developed against BEFV but not against KOTV or FUKAV, a test capable of detecting and differentiating these pathogens would be useful. In the present study, an RT-PCR method using degenerate primers designed to a region of block III of the polymerase (L) gene was developed and optimised for primer annealing temperature and MgCl2 concentration. The RT-PCR detected all known ephemeroviruses and several other closely related insect-transmitted rhabdoviruses, including FUKAV. Viruses could be identified by subsequent sequencing and phylogenetic analysis of the amplicons. BEFV could be detected using tissue culture isolates or cattle blood to a sensitivity of 500 RNA copies per reaction. This test will be useful for establishing the identity of the causative agent of bovine ephemeral fever from field samples and cultured isolates.