Infectious bronchitis virus in Asia, Africa, Australia and Latin America: history, current situation and control measures

Abstract

ABSTRACTINTRODUCTIONInfectious bronchitis virus (IBV) is ubiquitous in most parts of the worldwhere poultry are reared and is able to spread very rapidly in non-protected birds. It is shed via both the respiratory tract and the faecesand can persist in the birds and faeces for several weeks or months.Although strict biosecurity and working with a one-age system areessential control measures, normally vaccination is an essential tool toincrease the resistance of the chickens against challenge with IBV strains.This paper presents an overview of the history and current situation ofIBV in Asia, Africa, Australia and Latin America, including the controlmeasures necessary to control it.HISTORY OF INFECTIOUS BRONCHITIS VARIANTSFor many years it was widely believed that the first variants ofinfectious bronchitis virus (IBV) occurred in the early 1950s as Jungherret al. (1956) in the USA showed that the Connecticut (Conn) isolate of1951 neither cross neutralised nor cross protected with the originalMassachusetts (Mass) isolate from the early 1940s. However, aretrospective study (Jia et al., 2002), using monoclonal antibodies andmolecular analysis of part of the S1 subunit of the spike glycoprotein (S)gene, identified non-Mass IBVs among US isolates as early as the 1940s.Since the 1950s there have been many reports of other IB variants inUSA (reviewed by Fabricant, 1998), some of which are found worldwide.However, most countries are now known to have their own indigenousvariants as well, and this paper will consider the situation outside USAand Europe.IBV appeared in Latin America by the 1950s and the first reportedisolate from that continent was of the Mass serotype in Brazil (Hipolito,1957), although isolation of the first variant (Arkansas [Ark]) was notreported in that county until some 10 years later (Branden & Da Silva,1986). In a study carried out in the mid 1990s, IB isolates of at least 5different antigenic types were found in commercial chickens of all typesthroughout Brazil, but mainly in the major poultry producing area of thesouth (Di Fabio et al., 2000). More recently, several different genotypeshave been identified in Brazil by analysis of either the S1 (Villarreal etal., 2007a; Villarreal et al., 2007b; Montassier et al., 2008) or thenucleoprotein (N) genes (Abreu et al., 2006), but protection studies havenot been performed. It is important to remember that in Brazil at thattime, as in most other parts of the world, the only live attenuated IBvaccines licensed for use were of the Mass serotype and protection