Mastomys natalensis is a possible natural rodent reservoir for encephalomyocarditis virus.

Hirofumi Sawa,William W Hall,Yasuko Orba,Bernard M Hang'Ombe,Michihito Sasaki,Mai Kishimoto

doi:10.1099/jgv.0.001564

Abstract

Encephalomyocarditis virus (EMCV) infects a wide range of hosts and can cause encephalitis, myocarditis, reproductive disorders and diabetes mellitus in selected mammalian species. As for humans, EMCV infection seems to occur by the contact with animals and can cause febrile illnesses in some infected patients. Here we isolated EMCV strain ZM12/14 from a natal multimammate mouse (Mastomys natalensis: M. natalensis) in Zambia. Pairwise sequence similarity of the ZM12/14 P1 region consisting of antigenic capsid proteins showed the highest similarity of nucleotide (80.7 %) and amino acid (96.2%) sequence with EMCV serotype 1 (EMCV-1). Phylogenetic analysis revealed that ZM12/14 clustered into EMCV-1 at the P1 and P3 regions but segregated from known EMCV strains at the P2 region, suggesting a unique evolutionary history. Reverse transcription PCR (RT-PCR) screening and neutralizing antibody assays for EMCV were performed using collected tissues and serum from various rodents (n=179) captured in different areas in Zambia. We detected the EMCV genome in 19 M. natalensis (19/179=10.6 %) and neutralizing antibody for EMCV in 33 M. natalensis (33/179=18.4 %). However, we did not detect either the genome or neutralizing antibody in other rodent species. High neutralizing antibody litres (≧320) were observed in both RT-PCR-negative and -positive animals. Inoculation of ZM12/14 caused asymptomatic persistent infection in BALB/c mice with high antibody titres and high viral loads in some organs, consistent with the above epidemiological results. This study is the first report of the isolation of EMCV in Zambia, suggesting that M. natalensis may play a role as a natural reservoir of infection.

Highlights

Encephalomyocarditis virus (EMCV) infects a wide range of animal species and causes various conditions ranging from subclinical to lethal disease with myocarditis, encephalitis, neurological disorders, reproductive failure and diabetes mellitus in humans or animals [1]
Obvious cytopathic effect (CPE) with cell rounding and detachment was observed in BHK-21 cells inoculated with tissue homogenates from one M. natalensis captured in Mpulungu, which showed no macroscopic signs of serious infection
EMCV were isolated from a wide range of wild rodents; including rats (Rattus spp.) [35,36,37,38], mice (Mus spp.) [39,40], squirrels (Sciurus spp.) [41], dormice (Myoxus glis) [42], water-rats (Hydromys chrysogaster) [43], cotton rats (Sigmodon hispidus)

Summary

Introduction

Encephalomyocarditis virus (EMCV) infects a wide range of animal species and causes various conditions ranging from subclinical to lethal disease with myocarditis, encephalitis, neurological disorders, reproductive failure and diabetes mellitus in humans or animals [1]. Pigs are the most susceptible animal for EMCV, and EMCV infection causes a serious threat to the pig industry with sudden death often associated with myocarditis and reproductive failures including abortion [13,14,15]. Higher seropositive rates were observed in populations that have more frequent contact with wild animals such as hunters, indicating that EMCV may be a zoonotic pathogen which could be transmittd from animals to humans [16,17]. There have been no reports of direct transmission from rodents to other animals or humans, these rodent species have been considered to be a potential EMCV reservoir for susceptible animals, such as pigs, wild animals or potentially humans

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