Last updated: 9 September 1997
Field observations
In August 1995 EMCV was isolated for the first time from
fattening pigs in Belgium. Between August 1995 and December 1996, EMCV was
diagnosed in 154 pig holdings. In 46 farms EMCV was isolated in relation
to myocardial problems in fattening pigs. In 108 farms EMCV was isolated
in relation to reproductive problems or to sudden death in suckling
piglets (see Figure).
In fattening pigs sudden death was the most
characteristic symptom. A transitory paralysis was noticed in some
animals. The first outbreak started in periods characterised by very hot
temperatures. At the end of the autumn the number of outbreaks dropped
down and increased again at the end of the next summer. In the first
outbreak, over a period of four weeks, a mortality of 25% was noticed in
the affected pig house with pigs of about 70 kg. The mortality was
localised in some pens of the pig house. The remaining pigs had a
significant growth delay. At slaughter the seroprevalence in this pig
house was 52%. In the neighbouring pig house with pigs of 70 kg, the
symptoms were similar, but the mortality was lower. At slaughter the
seroprevalence was only 10%. In the remaining six pig houses, with pigs of
40 kg, 60 kg and 100 kg, no clinical disease was noticed, but virus was
isolated from the faeces of some animals. In the other outbreaks in
fattening pigs the mortality ranged around 5% and remained limited to some
pens in one pig house. Excitation was often the provoking factor.
In 3 days to 5 weeks old suckling piglets, sudden death
without any preliminary clinical symptom was also characteristic.
Generally the whole litter died. The losses varied between 1 and 10
litters in a pig herd and lasted maximum 10 weeks.
When EMCV was isolated in relation to reproductive
failure, abortions, still born and weak born piglets with high mortality
were noticed. In general the problems were restricted to 5 to 10 sows.
In closed farms the disease mostly remained restricted
to one age category. Some farms were affected by a plague of rats
An ad random serological survey, during the same period,
in sows from 668 farms revealed a seroprevalence of 3 % of the farms. A
farm was considered positive when one animal had a titer higher than 1/16.
Macroscopic and microscopic lesions
In fattening pigs and suckling piglets the macroscopic
lesions corresponded to these described in the literature. Common necropsy
findings were accumulation of excessive exudate in the body cavities and
greyisch-white necrosis of the myocardium aspecially the right ventricle.
Mineralisation was often visible. Microscopically myocarditis with
mononuclear cell infiltration was evident. Non purulent interstitial
myocardial muscle necrosis were most stricking. Dissociation and
degeneration of the heart muscle fibre were always present. In about half
of the cases there was a dystrofic calcification. In foeti these
myocardial lesions were never noticed.
In the outbreaks were EMCV was isolated in relation to
reproductive failure, mummification was noticed in 21 farms. No myocardial
lesions were found in the sows with reproductive failure or in their
offspring.
Information provided by:
Drs. Frank Koenen (frkoe@var.fgov.be) and Hans
Vanderhallen (hans.vanderhallen@var.fgov.be), Veterinary and
Agrochemic Research Center (CODA-CERVA), Groeselenberg 99, B-1180 Ukkel,
Belgium. Tel: +32 2 375 44 55; fax: +32 2 375 09 79.
References
Castryck, F., Miry, C., Koenen, F. and Ducatelle, R.
(1996). Clinical and pathological aspects of encephalomyocarditis virus
infections in pigs in Belgium. Proceedings of the 14th International Pig
Veterinary Society Congress, Bologna, Italy, 7-10 July 1996, p. 132.
Koenen, F. (1994). Clinical, serological, virological
and histological observations of encephalomyocarditis virus infection in
pigs. Pig Journal 33: 21-29.
Koenen, F. and Vanderhallen, H. (1997) Comparative study
of the pathogenic properties of a Belgian and a Greek encephalomyocarditis
Virus (EMCV) isolate for sows in gestation. J. Vet. Med. B 44: 281-286.
Koenen, F., De Clercq, K. and Strobbe, R. (1991).
Isolation of encephalomyocarditis virus in the offspring of swine with
reproductive failure in Belgium. Vlaams Diergeneeskd Tijdschr 60: 113-115.
Koenen, F., De Clercq, K., Lefebvre, J. and Strobbe, R.
(1994). Reproductive failure in sows following experimental infection with
a Belgian EMCV isolate. Veterinary Microbiology 39: 111-116.
Koenen, F., Vanderhallen, H., Castryck, F. and Miry, C.
(1997). Epidemiologic and molecular characteristics of recent EMCV
outbreaks in Belgium. Proceedings of the 4th International Congress of
Veterinary Virology, Edinburgh, Scotland, 24-27 August 1997, pp. 22.
Koenen, F., Vanderhallen, H., Castryck, F., Miry, C. and
Fockedey, M. (1996). Epidemiologic, pathogenetic and molecular analysis of
the first encephalomyocarditis outbreak in fattening pigs in Belgium.
Proceedings of the 14th International Pig Veterinary Society Congress,
Bologna, Italy, 7-10 July 1996, p. 96.
Koenen, F., Vanderhallen, H., Papadopoulos, O., Billinis,
C., Paschaleri-Papadopoulou, E., Brocchi, E., De Simone, F., Carra, E. and
Knowles, N.J. (1997). Comparison of the pathogenic, antigenic and
molecular characteristics of two encephalomyocarditis Virus (EMCV)
isolates from Belgium and Greece. Res. Vet. Sci. 62: 239-244.
Vanderhallen, H. and Koenen, F. (1997) Rapid diagnosis
of Encephalomyocarditis Virus infections in pigs using a reverse
transcription-polymerase chain reaction. J. Virol. Meth. 66: 83-89.
Vanderhallen, H. and Koenen, F. (1997). Identification
of EMCV in clinical samples by RT-PCR followed by genetic typing using
sequence analysis. Proceedings of the 4th International Congress of
Veterinary Virology, Edinburgh, Scotland, 24-27 August 1997, pp. 201.
