Free Access
Vet. Res.
Volume 35, Number 1, January-February 2004
Page(s) 113 - 122
How to cite this article Vet. Res. (2004) 113-122
Vet. Res. 35 (2004) 113-122
DOI: 10.1051/vetres:2003044

Transmission and pathogenicity of encephalomyocarditis virus (EMCV) among rats

Vassiliki Spyroua, Huibert Mauriceb, CharalambosBillinisa, c, Maria Papanastassopouloua, Dimitra Psallad, Mirjam Nielene, Frank Koenenf and Orestis Papadopoulosa

a  Laboratory of Microbiology and Infectious Diseases, Faculty of Veterinary Medicine, Aristotle University, Thessaloniki, GR-54124, Greece
b  Wageningen University, Social Sciences, Farm Management Group, Hollandseweg 1, 6706 KN Wageningen, The Netherlands
c  Present address: Laboratory of Microbiology and Parasitology, Faculty of Veterinary Medicine, University of Thessaly, Trikalon 224, GR-43100 Karditsa, Greece
d  Laboratory of Pathology, Faculty of Veterinary Medicine, Aristotle University, Thessaloniki, GR-54124, Greece
e  University Utrecht, Faculty of Veterinary Medicine, Department of Farm Animal Health, Yalelaan 7, NL-3584 CL Utrecht, The Netherlands
f  Veterinary and Agrochemical Research Center (CODA), Groeselenberg 99, B-1180 Ukkel, Belgium

(Received 9 January 2003, accepted 18 August 2003)

Abstract - Due to the probable role played by rodents as a reservoir for the transmission of the EMC virus to pigs, the experiment reported here was performed in order to assess the transmission rate of EMCV within a rat population. Twenty-five eight-week-old Wistar rats housed in individual plastic cages were experimentally infected either with a Greek myocardial EMCV strain (5 rats with a 0.2 $\times$ 106 TCID50 dose per rat and 10 rats with a 0.5 $\times$ 104.5 TCID50 dose per rat, oronasally) or a Belgian myocardial EMCV strain (10 rats with a 0.5 $\times$ 104.5 TCID50 dose per rat, oronasally). Two to five days later, each inoculated rat was moved to a new clean cage and coupled with a contact rat to compare the pathogenicity of the two strains and to estimate the basic reproduction ratio R0, indicating the level of EMCV transmission. During the experiments, faecal virus excretion was measured as well as the serological response against EMCV. After euthanasia, virus isolation was attempted from different rat tissues. Neither strains produced mortality, nor clinical signs and only low titres of neutralising antibodies were found. All contact rats, however, were infected and the virus was isolated from their faeces and from various tissues. Both 10-pair experiments revealed a point estimate for the R0 of $\infty$ (95%-CI for both the Greek and Belgian EMCV strains = 4.48 - $\infty$), as did the 5-pair experiment with a higher dose of the Greek strain (95%-CI = 1.83 - $\infty$). Combining the results from the two 10-pair experiments resulted in an estimate for R0 of $\infty$ (95%-CI: 9.87 - $\infty$). These results indicate that the EMC virus can spread very easily within a rat population by horizontal rat-to-rat transmission (R0 >> 1).

Key words: encephalomyocarditis virus / rats / pathogenicity / transmission / R0

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© INRA, EDP Sciences 2004