Friday, February 10, 2023

Preprint: First Mass Mortality of Marine Mammals Caused by Highly Pathogenic Influenza Virus (H5N1) in South America

Credit Senasa_Peru 


Earlier this week, in Peru: SERNANP Reports At Least 585 Sea Lions & 50,000 birds killed by Avian Flu. we learned of the large-scale die off of sea lions due to HPAI H5N1.  While this is not the first instance of H5N1 infecting marine mammals (see here, here, and here), it is the largest, and deadliest to date. 

We've seen other avian flu viruses infect and kill marine mammals, including H3N8 in New England (2011), H10N8 in Germany (2014), and H5N8 in the Baltic Sea (2017), but this outbreak comes on the heels of suspected mammal-to-mammal transmission of H5N1 in farmed mink, raising concerns this could be another example. 

Today researchers from Argentina and Peru have published a preprint on their investigation into this die off, where they state that mammal-to-mammal transmission of the virus cannot be ruled out. 

We also learn, as we've seen with so many other recent mammalian infections (see herehere, and here), that these marine mammals suffered from severe neurological manifestations such as tremors, convulsions and paralysis. 

I've only reproduced the brief abstract, along with some brief excerpts from the report, so follow the link to read it in its entirety. 

First Mass Mortality of Marine Mammals Caused by Highly Pathogenic Influenza Virus (H5N1) in South America
 Victor Gamarra-Toledo,  Pablo Plaza, Giancarlo Inga,  Roberto Gutierrez, Oscar Garcia-Tello, Leonela Valdivia-Ramirez, Deyvis Huaman-Mendoza, Jose Nieto-Navarrete, Sandra Ventura,   A. Lambertucci

We report the first worldwide infection and massive mortality associated with a Highly Pathogenic Influenza Virus (H5N1) in sea lions of Peru. The transmission pathway of H5N1 may have been through the close contact of sea lions with infected wild birds. We cannot rule out direct transmission among sea lions.

We show that sea lions (Otaria flavescens) of Peru, an endangered species according to  the national legislation (6), were infected by HPAI (H5N1) and developed a deadly associated disease producing massive mortality in several regions of the Peruvian  coastline (Fig. 1). The sea lion mass mortality described is compatible with systemic HPIV that resulted in acute encephalitis and pneumonia.

 Some specific cases of infection and mortality of marine mammals due to HPIV with similar clinical and  anatomopathological characteristics have been reported in previous studies around the world (5,7,8). For instance, 1,400 dead harbor seals (Phoca vitulina) were found dead in Germany alone; necropsied individuals (n=17) showed congestive lungs and interstitial pneumonia due to HPIV (7). Similarly, in USA, seal mortalities were reported with pneumonia and neurological symptoms due to H5N1 (5). 

However, to our knowledge, this is the first confident report of massive mortality by disease associated with HPIV 108 (H5N1) in sea lions, and the first report of wild mammal mortality in South America.

The source of the HPAI affecting these sea lions was very probably the large number of infected birds/carcasses on the Peruvian coastline (4). Sea lions may be infected by close contact with these carcasses and even through their consumption (see Fig. 2 F).  However, the transmission pathway remains unknown until now. Such high levels of mortality in a social animal are worrisome.

 We cannot exclude direct transmission among sea lions due to their colonial breeding, and because many  animals died simultaneously in groups. In fact, based on recent research suggesting the first mammal-to-mammal infection in minks (Neovison vison) (9) and the large number of sea lions currently affected, we cannot rule out that the virus has adapted to mammals and that sea lion-sea lion transmission has begun in Peru; this should be urgently  investigated. 

Moreover, the mass mortality of animals that can weigh around 350 kg (10) produces an enormous biomass of infected tissue, which could perpetuate the transmission of H5N1 and other pathogens. This could have serious consequences for the ecosystem and human health.