In 2005 an equine rhinitis A virus (ERAV) isolate was recovered from a
febrile horse during a respiratory outbreak in Ontario. This isolate (ERAV/ON/05)
was propagated in cell culture and used to study its genomic characteristics and
to investigate the clinical features in experimentally infected ponies. The fulllength
genome of this isolate was sequenced and compared with other ERAV
available in GenBank. The isolate genome is 7839 nucleotides (nts) in length
with a variable 5’UTR and a more conserved 3’UTR. When the isolate was
compared to other reported ERAV, an insertion of 13 nts in the 5’UTR was
identified. Phylogenetic analysis demonstrated that ERAV/ON/05 was closely
related to the ERAV/PERV isolate, which was recovered in 1962 in the United
Kingdom. An experimental model was developed to study the clinical infection in
naïve healthy ponies (ERAV/ON/05 n=4 and placebo n=4). ERAV/ON/05
induced clinical respiratory disease compared to placebo. The clinical signs
consisted of pyrexia, nasal discharge, increased and abnormal lung sounds,
increased size of submandibular lymph nodes and persistent mucopus in the
trachea (up to 21 days post-infection). The virus was isolated from the lower and
upper airways up to day 7 post-infection, corresponding with the detection of
neutralizing ERAV antibodies. Assessment of the cytokine profile from
bronchoalveolar lavage (BAL) cells demonstrated that this infection induced
down-regulation of the mRNA expression of IL-4. One year later, four previously
infected ponies with neutralizing antibodies to ERAV were assigned to a reinfection
trial. None of the re-infected ponies developed clinical disease, and only
one animal had a four-fold increase in antibody titres to ERAV. Attempts to
recover the virus from the re-infected ponies using cell culture were negative;
however, a down-regulation of the mRNA expression of IL-4 and IFN-β was
identified in BAL cells. In conclusion, this study shows that the genome of ERAV has not
significantly changed in the last 50 years and more importantly the virus induces
clinical respiratory disease similar to other common equine respiratory viruses.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:OGU.10214/3645 |
| Date | 15 May 2012 |
| Creators | Diaz-Mendez, Andres |
| Contributors | Viel, Laurent, Nagy, Eva |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Rights | http://creativecommons.org/licenses/by-nc-nd/2.5/ca/ |
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