Genetically diverse herpesviruses in South American Atlantic coast seabirds

Abstract

Different herpesviruses have been associated with respiratory and enteric disease and mortality among seabirds and waterfowl. In 2011, a respiratory disease outbreak affected 58.3% (98/168) of the Magellanic penguins undergoing rehabilitation due to an oil spill off the southern Brazilian coast. Etiology was attributed to a novel herpesvirus identified by histopathology, immunohistochemistry, electron microscopy and molecular studies with partial DNA sequencing. Since migration, rehabilitation and translocation may facilitate the spread of pathogens between populations and trigger the onset of clinical disease in animals with latent infections, investigation of herpesvirus occurrence in asymptomatic seabirds was performed. Samples from free-ranging seabirds were collected in Argentinian Patagonia (Magellanic penguins) and the Abrolhos Archipelago in Brazil (Brown boobies, Masked boobies, Red-billed tropicbirds, White-tailed tropicbirds and South American tern). Furthermore, asymptomatic seabirds housed at the facility where the outbreak occurred were also sampled. In total, 354 samples from eight seabird species were analyzed by PCR for herpesvirus. Four different sequences of herpesviruses were identified, one in Yellow-nosed Albatross, one in Boobies and Tropicbirds and two in Magellanic penguins. Magellanic penguin herpesvirus 1 was identified during the penguin outbreak at the rehabilitation facility in Brazil, while Magellanic penguin herpesvirus 2 was recovered from free-ranging penguins at four reproduction sites in Argentina. Phylogenic analysis of the herpesviruses sequences tentatively identified suggested that the one found in Suliformes and the one associated with the outbreak are related to sequences of viruses that have previously caused seabird die-offs. These findings reinforce the necessity for seabird disease surveillance programs overall, and particularly highlight the importance of quarantine, good hygiene, stress management and pre-release health exams in seabirds undergoing rehabilitation.

Fig 1. H&E slide of trachea epithelium with multiple foci of necrosis and squamous metaplasia.

Syncytial giant cells in the tracheal epithelium of Magellanic penguins contained amphophilic intranuclear inclusions (black arrow) characteristic of Herpesvirus infection. H&E.

Fig 2. Electron microscopy of Magellanic penguin tracheal epithelial cell.

The epithelial cell nuclei with intranuclear viral particles and enveloped virions in the extracellular space from a Magellanic penguin (Spheniscus magellanicus).

Fig 3. Immunohistochemical assay of Magellanic penguin (Spheniscus magellanicus) trachea tissue.

(A) Negative immunohistochemical assay of Magellanic Penguin (Spheniscus magellanicus) trachea tissue using specific anti-Gallid herpesvirus 1 murine monoclonal antibody and (B) positive control of trachea from chickens (Gallus gallus) naturally infected with GaHV-1, showing intense coloration where reaction occured. Hematoxylin Mayer.

Fig 4. Molecular phylogenetic analysis by Maximum Likelihood method.

The evolutionary history was inferred by using the Maximum Likelihood method based on the Le_Gascuel_2008 model [13]. The tree with the highest log likelihood (-1242.2246) is shown. The tree is drawn to scale, with branch lengths measured in the number of substitutions per site. The analysis involved 26 amino acid sequences. Evolutionary analyses were conducted in MEGA6 [11].