Two weeks ago, in Russia: Mass Mortality Event (Seals) In Caspian Sea Linked To Avian Flu we looked at the mass die off of (reportedly) 2,500 seals last December, and a report from Dagestan State University stating that an (as yet unsubtyped) avian influenza A virus was detected in the carcasses of the seals they tested.
While H5N1 was not confirmed, it was mentioned in their statement as a likely cause.
A little over a week ago Russia's Federal Service for Veterinary and Phytosanitary Surveillance (Rosselkhoznadzor) announced they were unable to confirm those test results, and have asked the Dagestan State University to provide biological samples of what they tested.
Since then, Russian media has been filled with conflicting reports and opinion pieces on the cause of this mass mortality event.
Some are blaming illegal and/or poorly run landfills, which have allegedly polluted the waters of the Caspian sea, and have allowed seagulls to feed on the carcasses of dead animals. One recent Russian media (translated) report explains:
Most violations are blamed on some municipalities that do not fulfill their obligations to create places for the storage of MSW. In addition, in Dagestan they cannot build waste transfer stations in any way. Because of this, a landfill appeared next to the Cherskes-Ozen River. Seagulls fed there, which were in contact with dead seals . Plus - from there the viruses flowed into the sea and infected animals.
This landfill `scandal' in Dagestan gets a lot of play in the local media, and appears to be a political hot potato. Others are promoting the idea that natural events - like seismic activity under the Caspian sea - led to the release of methane, hydrocarbons, or heavy metals, which killed the seals.
Yesterday, Russian media reported:
Experts will find out the reason for the death of seals in Dagestan
Specialists will conduct a large expedition to identify the causes of death of seals in Dagestan. Work is scheduled to start in spring 2023. According to one of the alleged versions, the animals could have been poisoned by heavy metals or hydrocarbons, the deposits of which are located in the Caspian Sea. Versions were also put forward about the presence of strains of bird flu in the bodies of dead mammals. The Volga Interregional Environmental Prosecutor's Office believes that the seals died due to the release of natural gas. However, there is no clear answer to this question yet.
While it seemed that we'd have to wait a few months for more answers, yesterday the Fisheries Committee of the Ministry of Ecology and Natural Resources of the Republic of Kazakhstan released their own analysis, which claims that thousands of seals died from pneumonia caused by viral infections (influenza and morbillivirus) - likely exacerbated by chronic exposure to `immunotoxic elements and compounds'.
They do not identify the type or strain of influenza in their report, nor is it clear exactly how they arrived at their conclusions.
Their (translated) statement - which is unlikely to be the last word on this topic - follows:
07 February 2023 - 17:56
🦭In the period from November 7 to December 3, 2022, during raid activities on the coast of the Caspian Sea in the Tupkaragan district of the Mangistau region, 172 carcasses of dead seals were found.
🔍To find out the reasons for the death of seals, the Fisheries Committee of the MENR RK involved scientific organizations: the Center for the Study and Rehabilitation of the Caspian Seal, the Institution "Institute of Hydrobiology and Ecology", LLP "Research and Production Center for Microbiology and Virology", LLP "Kazakhstan Agency of Applied Ecology", as well as interested state bodies: the Department of Ecology of the Mangistau region, territorial divisions of the Committee for Veterinary Control and Supervision of the Ministry of Agriculture of the Republic of Kazakhstan.
📊According to the results of the conclusion, the Working Group, consisting of representatives of scientific organizations and competent state bodies, came to the conclusion that the main cause of death of most Caspian seals found in November 2022 was virus-associated acute pneumonia as a result of an outbreak of mixed influenza and morbillivirus infections during the autumn concentration of animals in the Kazakhstani part of the sea. Chronic poisoning of marine animals with immunotoxic elements and compounds contributes to their increased susceptibility to infectious diseases due to a decrease in immunity and general body resistance.
📌Thus, the cause of death of the Caspian seals found in November 2022 was pneumonia, exacerbated due to viral infections caused by a decrease in the immunity of animals, including due to pollution of their habitat.
Despite some degree of uncertainty, HPAI remains a plausible explanation for this mammalian mass mortality event, although there may have been other contributing factors.
Whether (or when) we'll get a definitive answer, is hard to say.