ENCEPHALOMYOCARDITIS VIRUS INFECTION OF PIGS 2. Experimental Disease

Abstract

Encephalomycarditis virus recovered from a pig mortality in New South Wales was used to produce experimental infections. Of 34 pigs exposed, 17 died and a further 7 were found to have severe heart lesions when killed. Deaths occurred from 2 to 11 days after exposure with a mode of approximately 3 days. Ten of 11 pigs exposed by intramuscular injection died and the remaining pig was killed after 28 days and found to have severe resolving heart lesions. Of 15 pigs exposed per os to various doses of virus, 6 died, 4 were killed and found to have severe heart lesions and 5 were apparently not infected. Intranasal exposure of 8 pigs resulted in 1 death and 4 pigs with mild to severe heart lesions. Different doses of virus and routes of exposure did not substantially influence the character of the lesions. Lesions were similar to those found previously in field cases, and virus was recovered from all of 19 animals examined with severe acute lesions of 10 days standing or less.

Pathogenesis of encephalomyocarditis experimental infection in young piglets: a potential animal model to study viral myocarditis

“…Similar findings have also been observed in other experiments with high infectious doses and are common in spontaneous outbreaks of EMCV, when only some animals in the herd fall ill [11,19,21,41]. The starting myocarditis recorded in three pigs at 60-66-hpi implies that the incubation period was longer or that the infection evolved asymptomatically.…”

“…In swine, historical knowledge about the pathogenicity of EMCV indicates the heart as the main target organ [1,2,4,21,22]. In Table I.…”

“…In swine, the reported natural infections with EMCV have different epidemiological characteristics, probably depending on different EMCV strains which act with different pathogenicity [1,6]. EMCV has been recognised as a cause of fatal myocarditis in young piglets or reproductive failure in sows [1,2,6,17,19,21,26,30]. In Europe, EMCV was first isolated in an outbreak of fatal myocarditis in Italy in 1986 [16].…”

“…In Belgium, the virus has been frequently isolated in association with reproductive failure since 1991 [17], EMCV was isolated in Belgium in 1995 from an outbreak of fatal myocarditis in fattening pigs [19]. In dead pigs the dominant lesion could show focal to multifocal mononuclear myocarditis with myocardial necrosis [1,2,21]. The present paper was aimed at providing additional information of the pathogenesis of a Belgian isolate of EMCV in different organs in experimentally infected piglets.…”

Transmission of encephalomyocarditis virus in pigs estimated from field data in Belgium by means of R0

“…Neutralising antibodies can be detected as early as 5 days postinoculation in experimentally infected pigs [1], whereas the virus can be isolated from blood and excreta already one day after inoculation [3,7,17]. EMCV-transmission has been described from rodents to a wide variety of other species, including humans [1,16,22], while a recent study indicated that rats easily spread the virus among each other [24]. Although EMCV-transmission from rodents to pigs is considered important, also the impact of horizontal and vertical pig-to-pig transmission needs to be known/quantified to understand their contribution to the spread of the disease on a pig farm [7,17].…”