Molecular detection of Marek's disease virus in feather and blood samples from young laying hens in Colombia.

Marek's disease virus (MDV) is an immunosuppressive pathogen that can cause low production efficiency and high mortality rates in chickens. There is no current information on the MDV serotypes and pathotypes circulating in vaccinated commercial farms in Colombia where the birds are vaccinated in the incubator with Gallid herpesvirus (GaHV-2) and Meleagrid herpesvirus 1 (MeHV-1). Based on that, the main focus of this study was to understand the MDV's infection dynamics for the three known serotypes and to detect wild-virus pathogenic strains in 4-layer poultry farms in Antioquia. Samples of blood, feathers and spleens were collected from three randomly chosen animals according to age category: 1, 15, 30, 60, 90, and 120 days. Quantitative real-time PCR (qPCR) that differentiates between the three serotypes of MDV was used to assess viral loads over time, and phylogenetic analysis of the Meq oncogene was done to compare the strains of MDV with those of known pathogenicity. Meleagrid herpesvirus 1 (MeHV-1) was detected in all blood and feather follicle samples with an average number of genome copies (per 10,000 cells) of 31.44 in blood as expected as a result of vaccination. GaHV-2 was also detected in almost 100% of the blood and feather follicle samples throughout all defined age categories, with an average of 10.65 genome copies in blood samples. Gallid herpesvirus 3 (GaHV-3) was detected in 72% of blood and 84.61% of feather samples, with less than 1 copy per 10,000 cells. Based on the number of 132 bp repeats of the BamHI-H and BamHI-D regions in pooled feather samples, there were 70% (8/25) of attenuated MDV and 30% (17/25) of virulent MDV strains circulating in the farms. Virus isolation was performed successfully from every farm. In conclusion, different strains of MDV are circulating for up to 120 days in layers in Antioquia-Colombia and could be of major impact in poultry health. Keywords: Marek's disease virus (MDV); Antioquia-Colombia; qPCR; PCR; Meq gene phylogeny.

The role of animal reservoirs in social-environmental landscapes: remarks on the control of avian influenza and preparedness for pandemics.

Influenza viruses are well known for their ability to infect and cause disease in a broad range of hosts. Modern advances in reverse genetics have enabled scientists to probe the mutations that allow influenza viruses to perform host switching. Despite this detailed understanding of the molecular modifications that allow host switching and adaptation, there is a gap in knowledge regarding the factors external to the virus and their interactions that act as triggers leading to a pandemic. Studies on the ecology of zoonotic pathogens should be the new paradigm for understanding not only influenza viruses but any other infectious disease that can be a threat to animal and human health. The literature regarding influenza pandemics and influenza virus reservoirs was reviewed to analyse how social and economic changes can influence the appearance of new outbreaks of influenza. In addition, the importance of new research in a dynamic environment driven by the expansion of human territories and animal production systems is highlighted. A new paradigm is proposed for novel research approaches to infectious diseases such as influenza.

Les virus influenza se caractérisent par le large spectre d'hôtes qu'ils sont capables d'infecter et chez lesquels ils provoquent des maladies. Les avancées récentes de la génétique inverse ont permis aux chercheurs de suivre les mutations qui favorisent le passage des virus influenza d'un hôte à l'autre. Bien que les modifications moléculaires à l'origine du passage viral d'une espèce hôte à l'autre et de l'adaptation des virus à de nouveaux hôtes soient désormais bien comprises, d'importantes lacunes subsistent concernant les facteurs extérieurs aux virus et les interactions qui déclenchent la survenue de pandémies. L'étude de l'écologie des agents zoonotiques devrait constituer un nouveau paradigme de la recherche et permettra de mieux comprendre non seulement les virus influenza mais aussi toute maladie infectieuse présentant un danger pour la santé animale et publique. Les auteurs ont étudié la littérature consacrée aux pandémies de grippe et aux réservoirs des virus influenza et analysé l'influence des changements socio-économiques sur la survenue de nouveaux foyers de grippe. Ils soulignent également l'importance de conduire de nouveaux travaux de recherche dans un environnement dynamique transformé par l'extension des territoires utilisés par l'homme ainsi que par les systèmes de production animale. Un nouveau paradigme est ainsi proposé, qui permettra d'élaborer une méthodologie de recherche inédite dans le domaine des maladies infectieuses telles que les grippes.

Es bien conocida la capacidad que tienen los virus de la influenza de infectar y causar enfermedades a un conjunto muy heterogéneo de organismos anfitriones. Valiéndose de los últimos avances de la genética inversa, los científicos han podido utilizar sondas génicas con las mutaciones que permiten a los virus de la influenza pasar de un anfitrión a otro. Pese al detallado conocimiento que se tiene de las modificaciones moleculares que hacen posible el cambio de anfitrión y las correspondientes adaptaciones, no se sabe gran cosa de los factores externos al virus y del modo en que estos factores interaccionan para ejercer de desencadenantes de una pandemia. Los estudios sobre la ecología de patógenos zoonóticos deben ser el nuevo paradigma para comprender no solo los virus de la influenza, sino también los de otras enfermedades infecciosas que puedan constituir una amenaza sanitaria o zoosanitaria. Los autores repasan la bibliografía existente sobre pandemias de influenza y reservorios de este virus con el fin de analizar la repercusión que pueden tener los cambios sociales y económicos en la aparición de nuevos brotes de influenza. Además, se detienen a recalcar la importancia de las nuevas investigaciones en un entorno dinámico, cuya fuerza motriz es la expansión de los territorios humanos y los sistemas de producción animal. Los autores proponen un nuevo paradigma a partir del cual investigar con planteamientos novedosos enfermedades infecciosas como la influenza.

Genesis of pandemic influenza.

During the last decade the number of reported outbreaks caused by highly pathogenic avian influenza (HPAI) in domestic poultry has drastically increased. At the same time, low pathogenic avian influenza (LPAI) strains, such as H9N2 in many parts of the Middle East and Asia and H6N2 in live bird markets in California, have become endemic. Each AI outbreak brings the concomitant possibility of poultry-to-human transmission. Indeed, human illness and death have resulted from such occasional transmissions with highly pathogenic avian H7N7 and H5N1 viruses while avian H9N2 viruses have been isolated from individuals with mild influenza. The transmission of avian influenza directly from poultry to humans has brought a sense of urgency in terms of understanding the mechanisms that lead to interspecies transmission of influenza. Domestic poultry species have been previously overlooked as potential intermediate hosts in the generation of influenza viruses with the capacity to infect humans. In this review, we will discuss molecular and epidemiological aspects that have led to the recurrent emergence of avian influenza strains with pandemic potential, with a particular emphasis on the current Asian H5N1 viruses.