Equine picornavirus (EqPV), strain My 63, was isolated from
the liver and spleen of an aborted foal (Bohm, 1964). It was less than 28 nm
in diameter, contained an RNA genome and was ether, chloroform and trypsin
resistant. It was stable over a wide pH range (2.2-8.0) and rapidly
inactivated by heating at 50 °C. Divalent cations stabilized this isolate
against thermal inactivation. No serological investigations were undertaken.
However, this virus is no longer available.
During 1974/75 twelve acid stable picornaviruses were
isolated from nasopharyngeal swabs taken from horses in England (Mumford and
Thomson, 1978). Ten of the viruses were isolated from a single, healthy animal
over a period of 18 months. Four of the isolates which were compared in VN
tests belonged to a single serotype, but were not identical. The virus isolate
4442/75 was 22 nm in diameter, possessed a RNA genome, was resistant to
chloroform, rapidly inactivated at 50 °C, but stabilized by 1M MgCl2.
It was stable at pH 3.1-7.0 but rapidly inactivated at pH 2.7. The buoyant
density in CsCl was 1.40-1.43 g/ml, but increased to 1.44-1.48 g/ml on
prolonged centrifugation. EqPV/4442/75 grows, producing CPE, on RK-13, IB-RS-2
and LLC-MK2 cells (N.J. Knowles, unpublished data).
In Japan four acid-labile and two acid-stable
picornaviruses were isolated from the saliva of racehorses associated with
Getah virus infection. They formed two serological groups correlating with
acid-stability/lability (Fukunaga et al., 1981). In a subsequent study
the acid-labile viruses were identified as equine rhinovirus 2 (now named
equine rhinitis B virus 1), while the acid-stable viruses were shown to be
related to 4442/75 (Fukunaga et al., 1983). Both viruses were
re-isolated from two of the horses one year later demonstrating a persistent
infection. They produced CPE on RK-13 but not on Vero cells.
References
Bohm, H.O. (1964). Uber die isolierung und
charakterisierung eines picornavirus vom pferd. Zentbl. Vet. Med. 11: 240-250
.
Fukunaga, Y., Kumanomido, T., Imagawa, H., Ando, Y., Kamada,
M., Wada, R. and Akiyama, Y. (1981). Isolation of picornavirus from horses
associated with Getah virus infection. Jap. J. vet. Sci. 43: 569-572 .
Fukunaga, Y., Kumanomido, T., Kamada, M. and Wada, R.
(1983). Equine picornavirus: isolation of virus from the oral cavity of
healthy horses. Bull. Equine Res. Inst. 20: 103-109.
Mumford, J.A. and Thomson, G.R. (1978). Studies on
picornaviruses isolated from the respiratory tract of horses. Proc. 4th. Int.
Congress on Equine Infect Diseases. Ed. by J.T. Bryans and H. Gerber. Vet.
Pub. Inc., Princeton, N.J. Lyon, Sept., 1976 pp. 419-429.
