Transmissible gastroenteritis in Cuba: experimental reproduction of the disease and molecular characterization of the virus

Transmissible gastroenteritis (TGE) is a highly contagious enteric disease of pigs caused by an enteropathogenic coronavirus, TGEV. The sequence of the 5’ end of the spike glycoprotein (S) gene best distinguishes this virus from related coronavirus. Since February 2003, a large number of unexplained outbreaks of gastroenteritis have occurred on pig farms in Havana. The problem was identified as TGE for the first time in May 2003. This paper describes the virological and molecular studies that led to this diagnosis. The disease was experimentally reproduced in susceptible piglets, a sow, and in weaned pigs. TGEV recovered from the diarrheic faeces of the sick piglets was identified by electron microscope negative staining, viral isolation in secondary swine kidney cultures, and by RT-PCR using previously reported primers. The PCR product amplified from the 5’ end of the S gene was directly sequenced. The nucleotide sequence and the deduced amino acid residues of the amplified region are reported. A phylogenetic analysis was performed by comparing a 393-414 nucleotide stretch near the 5’ end of the S gene in 36 viruses from different countries and with different isolation dates. The virus causing the outbreak in Cuba seems to be closely related to a TGEV previously isolated in the US Midwest. The source of infection remains unknown. Additional key words: coronavirus, phylogenetic analysis, RT-PCR, spike protein, TGEV.