Recent spread of new strains of foot - and - mouth disease virus type A in the Middle East and North Africa

Introduction: Foot-and-mouth disease (FMD) serotype A is endemic in Afghanistan, Iran, Pakistan and Turkey, while sporadic outbreaks occur in the southern Middle Eastern countries. Periodically new genetic lineages appear to spread in a westward direction from Iran into Turkey, the best known event being the spread of the A22 strain throughout the Middle East from 1964 onwards. The precise origin of these variants is unknown. In 2005 and 2006, a new strain of FMDV A was identified in Iran, Pakistan, Saudi Arabia and Turkey (including Thrace). Additionally, during January and February 2006, FMD type A was reported in eight Egyptian governorates. The origins of these outbreaks have been studied by phylogenetic analysis of the VP1 gene. Materials and methods: Samples received from FMD outbreaks were typed by ELISA and viruses isolated in cell culture. The genome region encoding the VP1 outer capsid protein was amplified by RT-PCR using specific primers and the resultant amplicons were directly sequenced. Vaccine matching was performed using virus neutralization and/or LP-ELISA employing antisera raised in cattle against a range of vaccine virus strains. Results: Phylogenetic analyses revealed that recent FMDV A isolates from Iran, Pakistan, Saudi Arabia and Turkey formed single genetic lineage distinct from previous virus strains present in the region, including A-Iran-96 and A-Iran-99. Vaccine matching tests revealed the new lineage to be antigenically different to A-Iran-96 and more like A22. Genetically, the Egyptian type A virus differed considerably from the Middle Eastern viruses and was more closely related to FMD viruses from East Africa; antigenically, a vaccine incorporating A Eritrea 98 would be expected to afford protection. Discussion: Monitoring the emergence of new strains of FMDV in the Middle East is important to enable appropriate vaccines to be selected and control measures to be implemented as rapidly as possible. It is proposed that the new Middle East strain be named A-Iran-05.