Viral neurotropism, peripheral neuropathy and other morphological abnormalities in bovine ephemeral fever virus-infected downer cattle.
OBJECTIVE
This study assessed the neurotropism of bovine ephemeral fever (BEF) virus (BEFV) and described histomorphological abnormalities of the brain, spinal cord and peripheral nerves that may causally contribute to paresis or paralysis in BEF.


METHODS
Four paralysed and six asymptomatic but virus-infected cattle were monitored, and blood and serum samples screened by qRT-PCR, virus isolation and neutralisation tests. Fresh brain, spinal cord, peripheral nerve and other tissues were qRT-PCR-tested for viral RNA, while formalin-fixed specimens were processed routinely and immunohistochemically evaluated for histomorphological abnormalities and viral antigen distribution, respectively.


RESULTS
The neurotropism of BEFV was immunohistochemically confirmed in the brain and peripheral nerves and peripheral neuropathy was demonstrated in three paralysed but not the six aneurological but virus-infected animals. Wallerian degeneration (WD) was present in the ventral funicular white matter of the lumbar spinal cord of a paralysed steer and in cervical and thoracic spinal cord segments of three paralysed animals. Although no spinal cord lesions were seen in the steer euthanased within 7 days of illness, peripheral neuropathy was present and more severe in nerves of the brachial plexuses than in the gluteal or fibular nerves. The only steer with WD in the lumbar spinal cord also showed intrahistiocytic cell viral antigen that was spatially distributed within areas of moderate brain stem encephalitis.


CONCLUSIONS
The data confirmed neurotropism of BEFV in cattle and documented histomorphological abnormalities in peripheral nerves and brain which, together with spinal cord lesions, may contribute to chronic paralysis in BEFV-infected downer cattle.
Berrimah Veterinary Laboratories, Department of Primary Industry & Fisheries, GPO Box 3000, Darwin, Northern Territory 0801, Australia. Robert.Barigye@nt.gov.au, rbarigye@yahoo.com.
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Barigye
Berrimah Veterinary Laboratories, Department of Primary Industry & Fisheries, GPO Box 3000, Darwin, Northern Territory 0801, Australia.
S
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Davis
Berrimah Veterinary Laboratories, Department of Primary Industry & Fisheries, GPO Box 3000, Darwin, Northern Territory 0801, Australia.
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R
Hunt
Berrimah Veterinary Laboratories, Department of Primary Industry & Fisheries, GPO Box 3000, Darwin, Northern Territory 0801, Australia.
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N
Hunt
Berrimah Veterinary Laboratories, Department of Primary Industry & Fisheries, GPO Box 3000, Darwin, Northern Territory 0801, Australia.
S
S
Walsh
Berrimah Veterinary Laboratories, Department of Primary Industry & Fisheries, GPO Box 3000, Darwin, Northern Territory 0801, Australia.
N
N
Elliott
Berrimah Veterinary Laboratories, Department of Primary Industry & Fisheries, GPO Box 3000, Darwin, Northern Territory 0801, Australia.
C
C
Burnup
Berrimah Veterinary Laboratories, Department of Primary Industry & Fisheries, GPO Box 3000, Darwin, Northern Territory 0801, Australia.
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Aumann
Berrimah Veterinary Laboratories, Department of Primary Industry & Fisheries, GPO Box 3000, Darwin, Northern Territory 0801, Australia.
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C
Day
Berrimah Veterinary Laboratories, Department of Primary Industry & Fisheries, GPO Box 3000, Darwin, Northern Territory 0801, Australia.
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Dyrting
Berrimah Veterinary Laboratories, Department of Primary Industry & Fisheries, GPO Box 3000, Darwin, Northern Territory 0801, Australia.
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Weir
Berrimah Veterinary Laboratories, Department of Primary Industry & Fisheries, GPO Box 3000, Darwin, Northern Territory 0801, Australia.
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LF
Melville
D000818:Animals; D001921:Brain / Q000473:pathology / Q000821:virology; D002417:Cattle; D004810:Ephemeral Fever / Q000097:blood / Q000150:complications / Q000473:pathology* / Q000821:virology*; D018115:Ephemeral Fever Virus, Bovine / Q000302:isolation & purification* / Q000502:physiology; D015876:Northern Territory; D010243:Paralysis / Q000209:etiology / Q000662:veterinary / Q000821:virology; D010523:Peripheral Nervous System Diseases / Q000150:complications / Q000473:pathology / Q000662:veterinary* / Q000821:virology; D012367:RNA, Viral / Q000032:analysis; D060888:Real-Time Polymerase Chain Reaction / Q000662:veterinary; D013116:Spinal Cord / Q000473:pathology / Q000821:virology
D012367:RNA, Viral
Wallerian degeneration; bovine ephemeral fever virus; downer cows; encephalitis; neurotropism; peripheral neuropathy