Experimental Intervention

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Science  04 Oct 2013:
Vol. 342, Issue 6154, pp. 15-17
DOI: 10.1126/science.342.6154.15-c

We know that some viruses can rapidly spread among wild birds, as witnessed by pandemic influenza viruses. Realizing their close similarity to mammalian retroviruses, Niewiadomska and Gifford have been sleuthing among the genomes of reticuloendotheliosis viruses (REV) of birds. Sequences of these viruses have surprisingly also turned up within the genomes of a couple of large DNA viruses: fowlpox and gallid herpesvirus 2 (Marek's disease). Phylogenetically, REV history stretches back beyond the origins of echidnas in the mammalian lineage, more than 8 million years ago, but they only turned up in birds during the 1930s. How? Via human intervention. Further sleuthing in the literature led to just one archived sample of duck infectious anemia virus, which traced back to a series of experiments on a bird malaria isolate collected in Southeast Asia. There was a lot of interest in this newly discovered parasite, and samples were disseminated to five different laboratories. Unfortunately, the malaria samples had somehow become contaminated with REVs, possibly during serial passage using mammalian blood or possibly by contact with the bêtes noirs for pathogen spillovers—bats. The REV was then able to integrate into bona fide bird viruses, and thence into vaccine strains, and ineluctably became one of the hazards modern poultry have to face.

PLOS Biol. 11, e1001642 (2013).

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