RESUMEN
A number of contemporary outbreaks of Newcastle disease (ND) in Israel, Turkey, Georgia and Bulgaria have all been caused by a very similar viruses related to lineage 5a (genotype VIIa). Comparison with published ND virus (NDV) sequences suggests that this virus strain originated in South-East Asia and on introduction has circulated widely in backyard poultry in the Middle East and into Eastern Europe. An intracerebral pathogenicity index of 1.9 was obtained for a representative isolate from Bulgaria. In addition, the International Reference Laboratory for ND has characterized a molecular epidemiologically linked virus that has been reported to have caused disease in well-vaccinated broiler chickens in Pakistan. In the 1990s, another strain from the 5a lineage NDV was introduced into Europe and spread across the continent causing numerous outbreaks up to 1999. Despite improved controls, including good diagnostic tests and widespread vaccination, in commercial poultry, the novel circulating NDV strains described here have been established widely in the region and represent an increased risk for similar disease outbreak events to reoccur within the EU.
Asunto(s)
Enfermedades Transmisibles Emergentes/virología , Brotes de Enfermedades/veterinaria , Enfermedad de Newcastle/virología , Virus de la Enfermedad de Newcastle/patogenicidad , Animales , Pollos , Enfermedades Transmisibles Emergentes/epidemiología , Enfermedades Transmisibles Emergentes/transmisión , Europa Oriental/epidemiología , Genotipo , Epidemiología Molecular , Enfermedad de Newcastle/epidemiología , Enfermedad de Newcastle/transmisión , Virus de la Enfermedad de Newcastle/genética , Virus de la Enfermedad de Newcastle/inmunología , Filogenia , Aves de Corral , Enfermedades de las Aves de Corral/epidemiología , Enfermedades de las Aves de Corral/virología , ARN Viral/química , ARN Viral/aislamiento & purificación , Vacunas Virales , VirulenciaRESUMEN
This study reports the first incursion into European poultry of H5N1 highly pathogenic notifiable avian influenza A (HPNAI) viruses from clade 2.3.2 that affected domestic poultry and wild birds in Romania and Bulgaria, respectively. Previous occurrences in Europe of HPNAI H5N1 in these avian populations have involved exclusively viruses from clade 2.2. This represents the most westerly spread of clade 2.3.2 viruses, which have shown an apparently expanding range of geographical dispersal since mid-2009 following confirmation of infections in wild waterfowl species in Mongolia and Eastern Russia. During March 2010, AI infection was suspected at post-mortem examination of two hens from two backyard flocks in Tulcea Country, Romania. HPNAI of H5N1 subtype was confirmed by reverse transcription polymerase chain reaction (RT-PCR). A second outbreak was confirmed 2 weeks later by RT-PCR, affecting all hens from another flock located 55 km east of the first cluster. On the same day, an H5N1 HPNAI virus was detected from a pooled tissue sample collected from a dead Common Buzzard found on the Black Sea coast in Bulgaria. Detailed genetic characterization of the haemagglutinin gene revealed the cleavage site of the isolates to be consistent with viruses of high pathogenicity belonging to clade 2.3.2 of the contemporary Eurasian H5N1 lineage. Viruses from a clade other than 2.2 have apparently spread to wild birds, with potential maintenance and spread through such populations. Whilst the scale of threat posed by the apparent westward spread of the clade 2.3.2 viruses remains uncertain, ongoing vigilance for clinical signs of disease as part of existing passive surveillance frameworks for AI, and the prompt reporting of suspect cases in poultry is advised.
Asunto(s)
Enfermedades Transmisibles Emergentes/veterinaria , Brotes de Enfermedades/veterinaria , Subtipo H5N1 del Virus de la Influenza A/aislamiento & purificación , Gripe Aviar/transmisión , Aves de Corral/virología , Animales , Animales Salvajes/virología , Aves/virología , Bulgaria/epidemiología , Enfermedades Transmisibles Emergentes/epidemiología , Enfermedades Transmisibles Emergentes/transmisión , Subtipo H5N1 del Virus de la Influenza A/clasificación , Subtipo H5N1 del Virus de la Influenza A/patogenicidad , Gripe Aviar/epidemiología , Gripe Aviar/virología , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , Rumanía/epidemiologíaRESUMEN
Bulgaria has a unique geographic position in Europe, with two migratory wild bird routes, Via Pontica and Via Aristotelis, passing through the country. Via Pontica is the second-largest migration route in Europe, with hundreds of thousands of birds, representing more than 110 species, wintering in lakes by the Black Sea and the wetlands near the Danube River. Via Aristotelis is situated in West Bulgaria along the Strouma and Mesta river valleys, and it is of regional importance for the Balkan Peninsula. In this study, we examined more than 2000 samples from wild birds from the orders Anseriformes, Ciconiiformes, Gruiformes, and Charadriformes in the period 2006-2008. We isolated three influenza viruses, subtypes H4N6, H7N7, and H10N7, all from mallards, Anas platyrhynchos. The H7N7 was isolated from a hunter-killed mallard at the river bank of Kamchia (Via Pontica). The cleavage site sequence of the hemagglutinin gene in the H7N7 isolate was PEIPKGR*GLF, which is characteristic of a low-pathogenic virus. The H4N6 isolates belonged to a mallard wintering along the Maritza River (Via Aristotelis). We detected the H10N7 virus in samples from mallards that inhabit the Ogosta River, one of the feeders of the Danube (Via Pontica). All these viruses were detected during the active migration of the birds, February-March.
Asunto(s)
Patos , Gripe Aviar/virología , Animales , Bulgaria/epidemiología , Gripe Aviar/epidemiología , Vigilancia de la PoblaciónRESUMEN
Nota de Investigacón Bulgaria has a surveillance program on avian influenza to keep a close watch on health of poultry, exotic birds, and wild birds. The samples include sera for serologic examination, and carcasses, tissue samples, tracheal and cloacal swabs, and feces for virologic examination. The number of samples depends on the epizootic situation in the country and in neighboring countries. Migration and resting and living areas of wild birds also are under consideration. The territory of Bulgaria is divided into 28 regions. For each of these regions, there are exact types and numbers of samples, depending on latitude, water reservoir, farms, and backyards. Since October 2005, surveillance has become harder because of the situation in Romania and Turkey. Since 2006, the number of samples has vastly increased.