First detection of influenza A virus genes from wild raccoons in Japan

Zoonotic Animal Influenza Virus and Potential Mixing Vessel Hosts

Influenza viruses belong to the family Orthomyxoviridae with a negative-sense, single-stranded segmented RNA genome. They infect a wide range of animals, including humans. From 1918 to 2009, there were four influenza pandemics, which caused millions of casualties. Frequent spillover of animal influenza viruses to humans with or without intermediate hosts poses a serious zoonotic and pandemic threat. The current SARS-CoV-2 pandemic overshadowed the high risk raised by animal influenza viruses, but highlighted the role of wildlife as a reservoir for pandemic viruses. In this review, we summarize the occurrence of animal influenza virus in humans and describe potential mixing vessel or intermediate hosts for zoonotic influenza viruses. While several animal influenza viruses possess a high zoonotic risk (e.g., avian and swine influenza viruses), others are of low to negligible zoonotic potential (e.g., equine, canine, bat and bovine influenza viruses). Transmission can occur directly from animals, particularly poultry and swine, to humans or through reassortant viruses in "mixing vessel" hosts. To date, there are less than 3000 confirmed human infections with avian-origin viruses and less than 7000 subclinical infections documented. Likewise, only a few hundreds of confirmed human cases caused by swine influenza viruses have been reported. Pigs are the historic mixing vessel host for the generation of zoonotic influenza viruses due to the expression of both avian-type and human-type receptors. Nevertheless, there are a number of hosts which carry both types of receptors and can act as a potential mixing vessel host. High vigilance is warranted to prevent the next pandemic caused by animal influenza viruses.

Bacterial and Viral Pathogens with One Health Relevance in Invasive Raccoons (Procyon lotor, Linné 1758) in Southwest Germany

In Europe, raccoons are invasive neozoons with their largest population in Germany. Globally, this mesocarnivore acts as a wildlife reservoir for many (non-)zoonotic (re-)emerging pathogens, but very little epidemiological data is available for southwest Germany. This exploratory study aimed to screen free-ranging raccoons in Baden-Wuerttemberg (BW, Germany) for the occurrence of selected pathogens with One Health relevance. Organ tissue and blood samples collected from 102 animals, obtained by hunters in 2019 and 2020, were subsequently analysed for two bacterial and four viral pathogens using a qPCR approach. Single samples were positive for the carnivore protoparvovirus-1 (7.8%, n = 8), canine distemper virus (6.9%, n = 7), pathogenic Leptospira spp. (3.9%, n = 4) and Anaplasma phagocytophilum (15.7%, n = 16). West Nile virus and influenza A virus were not detected. Due to their invasive behaviour and synanthropic habit, raccoons may increase the risk of infections for wildlife, domestic animals, zoo animals and humans by acting as a link between them. Therefore, further studies should be initiated to evaluate these risks.

Avian Influenza A Virus Associations in Wild, Terrestrial Mammals: A Review of Potential Synanthropic Vectors to Poultry Facilities

The potential role of wild mammals in the epidemiology of influenza A viruses (IAVs) at the farm-side level has gained increasing consideration over the past two decades. In some instances, select mammals may be more likely to visit riparian areas (both close and distant to farms) as well as poultry farms, as compared to traditional reservoir hosts, such as waterfowl. Of significance, many mammalian species can successfully replicate and shed multiple avian IAVs to high titers without prior virus adaptation and often can shed virus in greater quantities than synanthropic avian species. Within this review, we summarize and discuss the potential risks that synanthropic mammals could pose by trafficking IAVs to poultry operations based on current and historic literature.

Host Receptors of Influenza Viruses and Coronaviruses-Molecular Mechanisms of Recognition

Among the four genera of influenza viruses (IVs) and the four genera of coronaviruses (CoVs), zoonotic αIV and βCoV have occasionally caused airborne epidemic outbreaks in humans, who are immunologically naïve, and the outbreaks have resulted in high fatality rates as well as social and economic disruption and losses. The most devasting influenza A virus (IAV) in αIV, pandemic H1N1 in 1918, which caused at least 40 million deaths from about 500 million cases of infection, was the first recorded emergence of IAVs in humans. Usually, a novel human-adapted virus replaces the preexisting human-adapted virus. Interestingly, two IAV subtypes, A/H3N2/1968 and A/H1N1/2009 variants, and two lineages of influenza B viruses (IBV) in βIV, B/Yamagata and B/Victoria lineage-like viruses, remain seasonally detectable in humans. Both influenza C viruses (ICVs) in γIV and four human CoVs, HCoV-229E and HCoV-NL63 in αCoV and HCoV-OC43 and HCoV-HKU1 in βCoV, usually cause mild respiratory infections. Much attention has been given to CoVs since the global epidemic outbreaks of βSARS-CoV in 2002-2004 and βMERS-CoV from 2012 to present. βSARS-CoV-2, which is causing the ongoing COVID-19 pandemic that has resulted in 890,392 deaths from about 27 million cases of infection as of 8 September 2020, has provoked worldwide investigations of CoVs. With the aim of developing efficient strategies for controlling virus outbreaks and recurrences of seasonal virus variants, here we overview the structures, diversities, host ranges and host receptors of all IVs and CoVs and critically review current knowledge of receptor binding specificity of spike glycoproteins, which mediates infection, of IVs and of zoonotic, pandemic and seasonal CoVs.

Effects of freshwater crayfish on influenza A virus persistence in water

Several investigations have recently assessed the ability of some aquatic invertebrates to act as tools for avian influenza A virus (IAV) surveillance as well as their potential role(s) in IAV ecology. Because of this, as well as the high IAV seroprevalence rates noted in select mesocarnivores that commonly inhabit aquatic and semi-aquatic habitats, we evaluated the effects that freshwater crayfish have on IAV in water at three dose levels and monitored for the presence of IAV in crayfish tissues (gill and green gland) and haemolymph at multiple time points. At relatively high, medium and low (approximately 10⁴ , 10³ and 10²  EID₅₀ /ml, respectively) doses, mesocosms containing crayfish (Orconectes sp.) had less detectable IAV RNA present when final water samples were assayed (9 days post-contact [DPC]). In general, containers without crayfish present had nearly three-fold greater quantities of viral RNA at 9 DPC. A varying number of RNA positive samples were detected for the three crayfish sample types collected. Gill tissue produced the largest number of positive non-water samples (n = 26), with the highest quantities detected from crayfish sampled on 1 and 4 DPC (10^3.5  EID₅₀ equivalent/ml). On a few occasions, gill (n = 8) and haemolymph samples (n = 1) produced higher quantities of viral RNA than their respective water samples or water samples collected 1-2 DPC earlier, but these differences were typically minor. Based upon water samples, statistical models indicated that the interaction of dose and crayfish exposure days explained most of the variation in these data. Future efforts should address if crayfish exposed to IAV-laden water have the capacity to successfully transmit IAVs to mammals and birds which frequently prey upon them.

Influenza A Viruses in Peridomestic Mammals

During recent years, serological evidence has shown that a number of peridomestic mammals (e.g., those commonly found in or around human structures) are naturally exposed to influenza A viruses (IAVs). In addition, experimental studies have demonstrated that many of these species can successfully replicate several different IAVs, including IAVs of high consequence to public or agricultural health. The replication of some IAVs within this group of mammals could have implications for biosecurity associated with poultry production and live bird markets in some regions of the world. Given this evidence, the need for further study and understanding of the role that peridomestic mammals may play in IAV dynamics is increasingly being recognized. This chapter will provide a general overview on IAV associations in peridomestic mammals, especially as they pertain to avian IAVs, and provide some general views and guidelines for sampling these species in various situations.