Universidad Nacional del Comahue, San Carlos de Bariloche, Argentina
ABSTRACT
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.
The recent global epidemic event (2020-2022) caused by the highly pathogenic avian influenza (HPAI) A (H5N1) is the largest observed so far, several global outbreaks having been caused (1,2). This is the first time the presence of this pathogen has been registered in some regions, where it has produced massive mortality in wild birds (2–4). This is of great concern and suggests a change has taken place in the dynamics of this pathogen (2).
At the end of 2022, the H5N1 virus reached South America (Peru, Ecuador, Colombia, Venezuela and Chile), with alarming outcomes in Peru (4). This pathogen was detected for the first time in wild birds in Peru on 13 November, as it caused very huge mortality levels (>22,000 birds over 4 weeks within protected areas) (4). Reports on both protected and non-protected areas suggest the virus generated a disease that killed at least >50,000 wild birds by the end of 2022, particularly Peruvian pelicans (Pelecanus thagus) and Peruvian boobies (Sula variegata) (4, Gamarra-Toledo et al. unpublished data). Most birds showed signs of neurological problems (e.g., incoordination, tremors and partial convulsions) before dying; impressive images of sandy beaches with dozens of dying birds highlighted the magnitude of this catastrophe (Suppl Mat, https://www.youtube.com/watch?v=45UZVY4IxTY). The large biomass of infected wild birds may have led to a spillover event affecting predators and scavengers, including marine mammals cohabiting with them, as reported in other parts of the world (5). In this article, we report the death of 634 sea lions (mainly Otaria flavescens and a few Arctocephalus australis) on Peruvian coasts over 5 weeks, and give details of the analyses that prove their infection with the Highly Pathogenic Influenza Virus (H5N1).