Bovine AstrovirusEncephalitis in a Hereford Steer

ROSE RUMNEY

OVC 2017

Case History•Called to farm to see an off-feed backgrounder steer

•Herd information:• Closed beef herd•Approximately 20 cows with suckling calves: fed dry hay with

access to pasture for grazing•Approximately 20 backgrounder yearlings housed indoors: fed dry

hay and high moisture corn.• Low input herd: no vaccinations, no coccidiostats, no implants, no

parasiticides.•No other livestock on the premises

Examination Findings

•Steer by himself in a pen indoors

•Owner reported off-feed for the past day or two

•Physical Examination Findings:•Most parameters within normal limits

• Some abnormalities noted:

•Decreased rumen fill

• Performing repetitive licking and chewing motions

• ‘Blank’ expression

http://www.flickriver.com/photos/hanneorla/86557460

Examination Findings•While leaving the pen the steer flipped from standing into dorsal recumbency and had a generalized tonic-clonic seizure.

•Convulsions lasted for 1-2 minutes• Frantic paddling motions of all four limbs

• Extension and flailing of head

• Nystagmus

• Apparent lack of consciousness

•Post-ictally the steer laid in lateral recumbency for ~5 minutes

•Then stood up and resumed moving around the pen normally

•Owner reported that this was the first time he had observed this behaviour

•Tried to restrain the steer to collect blood: seized again.

Initial Differential Diagnoses:•Bacterial Meningitis

•Rabies

•Polioencephalomalacia

•Nervous Coccidiosis

•Neurological Bovine Infectious Rhinotracheitis(Herpesvirus)

•Listeriosis

•Malignant Catarrhal Fever

•Histophilus somni

•Vitamin A deficiency

•BSE

Treatment:•Treated empirically based on signs of neurological disease:• Thiamine

• Trimethoprim Sulfadoxine

•Dexamethasone

•Died overnight

•Due to rabies concerns a full post mortem was not performed• Head removed and delivered to the AHL for diagnostic testing

•Fecal sample collected: only occasional coccidia oocysts seen

Diagnostic Testing:

•Rabies: Negative

•Histology:•Marked non-suppurative

meningoencephalitis• Throughout brainstem and

cerebral cortex

• Broad perivascular cuffing of blood vessels by lymphocytes

Photo credit: Dr. Maria Spinato

Diagnostic Testing:Tests for:• Listeriosis (Listeria monocytogenes)

•Malignant Catarrhal Fever (Ovine herpesvirus-2)

= Negative

Tentative Diagnosis:

Idiopathic Non-Suppurative Meningoencephalitis

More Diagnostic Testing:• Bovine herpesvirus-1

• Bovine respiratory syncytial virus

• Bovine parainfluenza virus-3

•Avian Astrovirus (chicken astrovirus + avian nephritis virus)

= All Negative

PCR for bovine astrovirus = Positive

Diagnosis: Bovine astrovirus encephalitis

Wait…….Astrovirus?•Astroviruses were first discovered in humans in 1975 (Madely and Cosgrove, 1975)

•A common causative agent of gastroenteritis in human infants

•Their role in diarrhea in cattle is not as well established, but enteric strains are thought to be prevalent within the cattle population (Candido et al, 2015)

Figure 1: Madely and Cosgrove, 1975.

Astrovirus Encephalitis•Neurotropic strains first identified in 2010 as a cause of encephalitis in immuno-suppressed humans (Quan et al, 2010; Brown et al, 2015)

• Caused by a different strain of virus than that involved in enteric disease

• In 2013 a neurotropic strain of astrovirus was identified as causing ‘shaking mink syndrome’ a neurological disease of young mink (Blomstrom et al, 2010)

Bovine Astrovirus Encephalitis•The first case of bovine astrovirus encephalitis was identified in 2013 in the United States (Li et al, 2013)

•In subsequent years more cases have been reported in Switzerland and Germany (Bouzalas et al 2014, Seuberlich et al 2016, Schlottauet al, 2016)

•This is the first case identified in Canada

•Phylogenetic analyses have shown that these neurotropic strains are most closely related to an ovine strain of astrovirus(Bouzalas et al, 2014; Bouzalas et al 2016)

Astrovirus: Clinical Syndrome•The published literature reports a variety of clinical signs associated with central neurological disease in affected animals:

•In all cases histological analysis of the brain showed a marked non-suppurativeencephalitis, with lymphocytic perivascular cuffing of blood vessels.

•Most cases involved relatively young animals (1-3 years of age), with only a single animal within a herd affected (Li et al 2013, Bouzalas et al 2014, Seuberlich et al 2016, Schlottauet al 2016)

• Head pressing• Circling• Seizures• Stargazing

• Cortical Blindness• Disorientation• Opisthotonus

Astrovirus: An Emerging Pathogen?•It appears that neurotropic astrovirus infections are not new:• Recent retrospective analyses performed on cases previously

diagnosed as ‘idiopathic non-suppurative encephalitis’ have found that neurotropic-astrovirus infections represent up to 25% of these cases! (Li et al 2013, Bouzalas et al 2016)

• The cases examined dated back to 1995, suggesting that this pathogen has been present for a long time (Li et al 2013)

• It seems that this is not a new disease! We are just learning to identify it now.

Back to our clinical case:•Information relayed back to the farmer:• Your steer died of astrovirus encephalitis

• We don’t know how it is spread

• We don’t know how to treat it

• We don’t know how to prevent it

• We don’t know why that particular steer was affected

• We don’t know if there is a risk to your other animals.

•Astrovirus encephalitis is currently a very active area of research, so hopefully soon we will know some of these answers!

Acknowledgements•A heartfelt thank-you to:• Eldale Veterinary Clinic and Dr. Nick Gallo

• The Animal Health Laboratory and Dr. Maria Spinato

Questions?

ReferencesMadeley CR, Cosgrove BP. Viruses in infantile gastroenteritis. Lancet 1975, 124.

Candido M, Alencar ALF, Almeida-Queiroz SR, Buzinaro MG, Munin FS, de Godoy SHS, Livonesi MC, Fernandes AM, de Sousa RLM. Molecular detection and phylogenetic analysis of bovine astrovirus in Brazil. Arch Virol 2015;160:1519-1525.

Quan PL, Wagner TA, Briese T, Torgerson TR, Hornig M, Tashmukhamedova A, Firth C, Palacios G, Baisre-De-Leon A, Paddock CD, Hutchison SK, Egholm M, Zaki SR, Goldman JE, Ochs HD, Lipkin WI. Astrovirus encephalitis in boy with X-linked agammaglobulinemia. Emerg Infect Dis 2010;16:918-925.

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Bouzalas IG, Wuthrich D, Walland J, Drogemuller C, Zurbriggen A, Vandevelde M, Oevermann A, Bruggmann R, Seuberlich T. Neurotropic astrovirus in cattle with nonsuppurative encephalitis in Europe. J Clin Microbiol 2014;52:3318-3324.

Seuberlich T, Wuthrich D, Selimovac-Hamza S, Drogemuller C, Oeverman A, Bruggmann R, Bouzalas I. Identification of a second encephalitis-associated astrovirus in cattle. Emerg Microbes Infect 2016;5:5-7.

Schlottau K, Schulze C, Bilk S, Hanke D, Hoper D, Beer M, Hoffman B. Detection of a novel bovine astrovirus in a cow with encephalitis. Transbound Emerg Dis 2016;63:253-259.

Bouzalas IG, Wuthrich D, Selimovic-Hamza S, Drogemuller C, Bruggman R, Seuberlich T. Full-genome based molecular characterization of encephalitis-associated bovine astroviruses. Infect

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