A recent study published within the One Health Advances Journal discussed influenza A virus (IAV) infections in minks, emphasizing their contribution/role as an intermediate host.

Study: Mink infection with influenza A viruses: an ignored intermediate host? Image Credit: shauttra/Shutterstock.com

Background

IAVs infect different hosts, including humans, birds, and marine mammals. Studies have demonstrated mink infection with IAV subtypes and viral transmission via aerosols. Mink infection with avian H5N1, H9N2, H5N6, and human or swine H1N1 and H3N2 viruses has been reported.

Sequence data from the Global Initiative for Sharing Avian Influenza Data (GISAID) repository shows that the speed of IAV detection in mink has increased considerably over the past decade.

Although minks are highly at risk of IAV infection, outbreaks with severe outcomes are rare. Studies suggest that animal feed containing pork and poultry by-products is likely to be chargeable for mink infection with swine/avian IAVs.

In contrast, mink infection with the human influenza virus may very well be because of transmission from farm employees. In the current study, the authors summarized the evidence on mink infections with IAVs, specializing in their role as intermediate hosts.

Mink infection with emergent viruses

China has witnessed multiple outbreaks of viral infections in mink farms since 2010. A novel orthoreovirus was detected in Hebei, with a mortality rate of 5%. In 2014, a swine pseudorabies outbreak was documented in Shandong, with a high rate of mortality estimated at 87%. Newcastle disease virus was chargeable for pneumonia and hemorrhagic encephalitis in mink in 2014.

In 2015, the highly pathogenic avian influenza virus (HPAIV) H5N1 caused outbreaks in two farms in China, with mortality estimated at 56% and 64%, respectively. Mink infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has increased, particularly in North American and European countries.

Furthermore, SARS-CoV-2 transmission from infected minks to humans was documented in Denmark and the Netherlands. Reassortment and adaptation are suggested as critical for zoonotic influenza viruses in humans. As well as, co-infection with different viruses in animals/humans might end in novel strains with pandemic potential.

Pigs are considered the blending vessel as they harbor receptors for human and avian influenza viruses. Likewise, minks exhibit an analogous feature, as they’ve each sialic acid α2,3-galactose (SA α2,3-Gal) and SA α2,6-Gal receptors for avian and human strains, respectively. Subsequently, minks could represent one other mixing vessel for novel strain(s).

Mink farms and infectious diseases

Neovison vison, the American mink, is a very important species for the fur-farming industry. China, Poland, Denmark, and the Netherlands are the foremost fur-producing countries. Most minks (80%) in China are farmed within the Shandong province.

Minks are densely populated on these farms and sure sheltered in a single facility/constructing. Thus, infectious diseases occur because of intensive farming, inadequate biosecurity, and poor sanitation.

Aleutian mink disease virus (AMDV) is notable for its devastating effects on the adult reproductive system and the next impact on fur quality.

Gastroenteric and respiratory symptoms are caused because of canine distemper virus (CDV), SARS-CoV-2, and mink enteritis virus (MEV). Bacteria equivalent to Escherichia coli, Klebsiella pneumoniae, and Pseudomonas aeruginosa are implicated in hemorrhagic pneumonia. 

Molecular and serologic features of influenza virus infection in minks

Sequences from the GISAID repository show that IAVs detected in minks are phylogenetically related to prevailing human, avian, and swine strains.

H9N2 and H5N6/H5N1 have been the predominant mink influenza virus subtypes in China since 2013. Genetic analyses revealed that every one H9N2 viruses detected in minks belonged to G9/Y280 lineage, prevalent in poultry.

All H5N1 and H5N6 subtypes detected in China and Spain, aside from one H5N1 subtype in Sweden, were likely introduced in minks from infected poultry.

Molecular analyses revealed mammalian adaptive signatures (D701N and E627K substitutions) within the polymerase basic 2 (PB2) gene. Quite a few studies have assessed the seroprevalence of avian IAVs in minks.

Seropositivity was the best for H9N2 amongst all subtypes in minks, ranging between 20% and 47.5% during 2013-19, and far lower for H5N6 and H5N1. Seroepidemiologic data show that minks in China are highly exposed to human and avian influenza viruses, increasing the danger of novel variants because of co-infection.

Concluding remarks

Taken together, high susceptibility to and receptors for human and avian influenza viruses in minks meet the prerequisites to serve because the intermediate host for interspecies influenza transmission.

Subsequently, routine surveillance of IAVs in minks and preventive measures must be implemented. Vaccination against influenza must be introduced within the mink populations for public health and industrial advantages.