Distribution of lesions and antigen of highly pathogenic avian influenza virus A/Swan/Germany/R65/06 (H5N1) in domestic cats after presumptive infection by wild birds

Potential biosecurity breaches in poultry farms: Presence of free-ranging mammals near laying-hen houses assessed through a camera-trap study

Diligent application and implementation of biosecurity measures stand as the most effective measures to prevent disease transmission through direct or indirect interactions between poultry and free-ranging animals. Among these, free-ranging mammals can be hosts or disseminators of several pathogens relevant to poultry and of public health concern. Moreover, evidence of susceptibility to avian influenza virus infection in non-human mammals has raised questions about their potential role in the virus' epidemiology at the domestic animal-wildlife interface. Given this background, this study aimed to identify mammal species occurring near laying-hen houses and characterize the spatiotemporal patterns of these visits. Seven camera traps were deployed for a year-long period in three commercial poultry farms in a densely populated poultry area in Northern Italy. Various methods, including time series analysis and generalized linear models, were employed to analyze daily mammal visits. A total of 1,867 camera trap nights yielded 567 videos of seven species of wild mammals, and 1,866 videos showed domestic pet species (cats and dogs). Coypus (Myocastor coypus) and cats were the two mammals more frequently observed near poultry houses. For wild mammals, visits significantly increased at night, and slightly decreased during the spring season. Overall, the data hereby provided lay the groundwork for designing novel surveillance and intervention strategies to prevent cross-species disease transmission. Moreover, the utilization of visual evidence depicting free-ranging animals approaching poultry houses could assist health authorities in educating and raising awareness among stakeholders about potential risks of pathogen spillover.

Highly Pathogenic Avian Influenza A(H5N1) Clade 2.3.4.4b Virus Infection in Domestic Dairy Cattle and Cats, United States, 2024

We report highly pathogenic avian influenza A(H5N1) virus in dairy cattle and cats in Kansas and Texas, United States, which reflects the continued spread of clade 2.3.4.4b viruses that entered the country in late 2021. Infected cattle experienced nonspecific illness, reduced feed intake and rumination, and an abrupt drop in milk production, but fatal systemic influenza infection developed in domestic cats fed raw (unpasteurized) colostrum and milk from affected cows. Cow-to-cow transmission appears to have occurred because infections were observed in cattle on Michigan, Idaho, and Ohio farms where avian influenza virus-infected cows were transported. Although the US Food and Drug Administration has indicated the commercial milk supply remains safe, the detection of influenza virus in unpasteurized bovine milk is a concern because of potential cross-species transmission. Continued surveillance of highly pathogenic avian influenza viruses in domestic production animals is needed to prevent cross-species and mammal-to-mammal transmission.

Outbreak of Highly Pathogenic Avian Influenza A(H5N1) Virus in Seals, St. Lawrence Estuary, Quebec, Canada1

We describe an unusual mortality event caused by a highly pathogenic avian influenza (HPAI) A(H5N1) virus clade 2.3.4.4b involving harbor (Phoca vitulina) and gray (Halichoerus grypus) seals in the St. Lawrence Estuary, Quebec, Canada, in 2022. Fifteen (56%) of the seals submitted for necropsy were considered to be fatally infected by HPAI H5N1 containing fully Eurasian or Eurasian/North American genome constellations. Concurrently, presence of large numbers of bird carcasses infected with HPAI H5N1 at seal haul-out sites most likely contributed to the spillover of infection to the seals. Histologic changes included meningoencephalitis (100%), fibrinosuppurative alveolitis, and multiorgan acute necrotizing inflammation. This report of fatal HPAI H5N1 infection in pinnipeds in Canada raises concerns about the expanding host of this virus, the potential for the establishment of a marine mammal reservoir, and the public health risks associated with spillover to mammals.Nous décrivons un événement de mortalité inhabituelle causé par un virus de l'influenza aviaire hautement pathogène A(H5N1) clade 2.3.4.4b chez des phoques communs (Phoca vitulina) et gris (Halichoerus grypus) dans l'estuaire du Saint-Laurent au Québec, Canada, en 2022. Quinze (56%) des phoques soumis pour nécropsie ont été considérés comme étant fatalement infectés par le virus H5N1 de lignées eurasiennes ou de réassortiment eurasiennes/nord-américaines. Un grand nombre simultané de carcasses d'oiseaux infectés par le H5N1 sur les sites d'échouement a probablement contribué à la contamination de ces phoques. Les changements histologiques associés à cette infection incluaient : méningo-encéphalite (100%), alvéolite fibrinosuppurée et inflammation nécrosante aiguë multi-organique. Cette documentation soulève des préoccupations quant à l'émergence de virus mortels, à la possibilité d'établissement de réservoirs chez les mammifères marins, et aux risques pour la santé publique associés aux propagations du virus chez les mammifères.

Characterization of neurotropic HPAI H5N1 viruses with novel genome constellations and mammalian adaptive mutations in free-living mesocarnivores in Canada

The GsGd lineage (A/goose/Guangdong/1/1996) H5N1 virus was introduced to Canada in 2021/2022 through the Atlantic and East Asia-Australasia/Pacific flyways by migratory birds. This was followed by unprecedented outbreaks affecting domestic and wild birds, with spillover into other animals. Here, we report sporadic cases of H5N1 in 40 free-living mesocarnivore species such as red foxes, striped skunks, and mink in Canada. The clinical presentations of the disease in mesocarnivores were consistent with central nervous system infection. This was supported by the presence of microscopic lesions and the presence of abundant IAV antigen by immunohistochemistry. Some red foxes that survived clinical infection developed anti-H5N1 antibodies. Phylogenetically, the H5N1 viruses from the mesocarnivore species belonged to clade 2.3.4.4b and had four different genome constellation patterns. The first group of viruses had wholly Eurasian (EA) genome segments. The other three groups were reassortant viruses containing genome segments derived from both North American (NAm) and EA influenza A viruses. Almost 17 percent of the H5N1 viruses had mammalian adaptive mutations (E627 K, E627V and D701N) in the polymerase basic protein 2 (PB2) subunit of the RNA polymerase complex. Other mutations that may favour adaptation to mammalian hosts were also present in other internal gene segments. The detection of these critical mutations in a large number of mammals within short duration after virus introduction inevitably highlights the need for continually monitoring and assessing mammalian-origin H5N1 clade 2.3.4.4b viruses for adaptive mutations, which potentially can facilitate virus replication, horizontal transmission and posing pandemic risks for humans.

Highly Pathogenic Avian Influenza A(H5N1) Virus Clade 2.3.4.4b Infections in Wild Terrestrial Mammals, United States, 2022

We describe the pathology of natural infection with highly pathogenic avian influenza A(H5N1) virus of Eurasian lineage Goose/Guangdong clade 2.3.4.4b in 67 wild terrestrial mammals throughout the United States during April 1‒July 21, 2022. Affected mammals include 50 red foxes (Vulpes vulpes), 6 striped skunks (Mephitis mephitis), 4 raccoons (Procyon lotor), 2 bobcats (Lynx rufus), 2 Virginia opossums (Didelphis virginiana), 1 coyote (Canis latrans), 1 fisher (Pekania pennanti), and 1 gray fox (Urocyon cinereoargenteus). Infected mammals showed primarily neurologic signs. Necrotizing meningoencephalitis, interstitial pneumonia, and myocardial necrosis were the most common lesions; however, species variations in lesion distribution were observed. Genotype analysis of sequences from 48 animals indicates that these cases represent spillover infections from wild birds.

A Fatal A/H5N1 Avian Influenza Virus Infection in a Cat in Poland

A European Shorthair male cat, neutered, approximately 6 years of age, was presented to the veterinary clinic due to apathy and anorexia. The cat lived mostly outdoors and was fed raw chicken meat. After 3 days of diagnostic procedures and symptomatic treatment, respiratory distress and neurological signs developed and progressed into epileptic seizures, followed by respiratory and cardiac arrest within the next 3 days. Post-mortem examination revealed necrotic lesions in the liver, lungs, and intestines. Notably, the brain displayed perivascular infiltration of lymphocytes and histiocytes. Few foci of neuronal necrosis in the brain were also confirmed. Microscopic examination of the remaining internal organs was unremarkable. The A/H5N1 virus infection was confirmed using a one-step real-time reverse transcription polymerase chain reaction (RT-qPCR). The disease caused severe neurological and respiratory signs, evidence of consolidations and the presence of numerous B lines, which were detected on lung ultrasound examination; the postmortem findings and detection of A/H5N1 viral RNA in multiple tissues indicated a generalized A/H5N1 virus infection. Moreover, a multidrug-resistant strain of Enterococcus faecium was isolated in pure culture from several internal organs. The source of infection could be exposure to infected birds or their excrements, as well as contaminated raw poultry meat but, in this case, the source of infection could not be identified.

Naturally occurring highly pathogenic avian influenza virus H5N1 clade 2.3.4.4b infection in three domestic cats in North America during 2023

The Eurasian strain of highly pathogenic avian influenza (HPAI) H5N1 is a devastating pathogen for birds that also has the capacity to infect mammals. This report describes the presentation, clinical case findings (including haemogram and serum biochemistry), gross and microscopic lesions and virus detection in three HPAI H5N1-infected domestic cats from the USA in 2023. All three cats presented with neurological abnormalities and were euthanized due to a poor prognosis within 2 days (two cats) or 10 days (one cat) of known clinical disease onset. Necropsy consistently revealed pulmonary congestion and oedema, and cerebrocortical malacia with haemorrhage was also seen in the cat that survived for 10 days. On histology, all cats had necrotizing encephalitis and interstitial pneumonia with pulmonary congestion, oedema, vasculitis and vascular thrombosis. One cat also had microscopic multifocal necrosis in the liver, pancreas and an adrenal gland. To our knowledge, this report is the first to detail pathological findings in HPAI H5N1 naturally-infected cats during the widespread outbreak in North America beginning in 2021, and that describes a cat surviving for 10 days after onset of HPAI H5N1 encephalitis.

Emerging Respiratory Viruses of Cats

In recent years, advances in diagnostics and deep sequencing technologies have led to the identification and characterization of novel viruses in cats as protoparviruses and chaphamaparvoviruses, unveiling the diversity of the feline virome in the respiratory tract. Observational, epidemiological and experimental data are necessary to demonstrate firmly if some viruses are able to cause disease, as this information may be confounded by virus- or host-related factors. Also, in recent years, researchers were able to monitor multiple examples of transmission to felids of viruses with high pathogenic potential, such as the influenza virus strains H5N1, H1N1, H7N2, H5N6 and H3N2, and in the late 2019, the human hypervirulent coronavirus SARS-CoV-2. These findings suggest that the study of viral infections always requires a multi-disciplinary approach inspired by the One Health vision. By reviewing the literature, we provide herewith an update on the emerging viruses identified in cats and their potential association with respiratory disease.

Canine and Feline Influenza

Influenza virus infections of carnivores-primarily in dogs and in large and small cats-have been repeatedly observed to be caused by a number of direct spillovers of avian viruses or in infections by human or swine viruses. In addition, there have also been prolonged epizootics of an H3N8 equine influenza virus in dogs starting around 1999, of an H3N2 avian influenza virus in domestic dog populations in Asia and in the United States that started around 2004, and an outbreak of an avian H7N2 influenza virus among cats in an animal shelter in the United States in 2016. The impact of influenza viruses in domesticated companion animals and their zoonotic or panzootic potential poses significant questions for veterinary and human health.

Serological Screening of Influenza A Virus Antibodies in Cats and Dogs Indicates Frequent Infection with Different Subtypes

Influenza A viruses (IAVs) infect humans and a variety of other animal species. Infections with some subtypes of IAV were also reported in domestic cats and dogs. In addition to animal health implications, close contact between companion animals and humans also poses a potential risk of zoonotic IAV infections. In this study, serum samples from different cat and dog cohorts were analyzed for IAV antibodies against seven IAV subtypes, using three distinctive IAV-specific assays differing in IAV subtype-specific discriminatory power and sensitivity. Enzyme-linked immunosorbent assays against the complete hemagglutinin (HA) ectodomain or the HA1 domain were used, as well as a novel nanoparticle-based, virus-free hemagglutination inhibition assay. Using these three assays, we found cat and dog sera from different cohorts to be positive for antibodies against one or more IAV subtypes and/or strains. Cat and dog serum samples collected after the 2009 pandemic H1N1 outbreak exhibit much higher seropositivity against H1 compared to samples from before 2009. Cat sera, furthermore, displayed higher reactivity for avian IAVs than dog sera. Our findings show the added value of using complementary serological assays, which are based on reactivity with different numbers of HA epitopes, to study IAV antibody responses and for improved serosurveillance of IAV infections. We conclude that infection of cats and dogs with both human and avian IAVs of different subtypes is prevalent. These observations highlight the role of cats and dogs in IAV ecology and indicate the potential of these companion animals to give rise to novel (reassorted) viruses with increased zoonotic potential.

Influenza A Virus Infection in Cats and Dogs: A Literature Review in the Light of the "One Health" Concept

Influenza A viruses are amongst the most challenging viruses that threaten both human and animal health. Constantly evolving and crossing species barrier, the emergence of novel zoonotic pathogens is one of the greatest challenges to global health security. During the last decade, considerable attention has been paid to influenza virus infections in dogs, as two canine H3N8 and H3N2 subtypes caused several outbreaks through the United States and Southern Asia, becoming endemic. Cats, even though less documented in the literature, still appear to be susceptible to many avian influenza infections. While influenza epidemics pose a threat to canine and feline health, the risks to humans are largely unknown. Here, we review most recent knowledge of the epidemiology of influenza A viruses in dogs and cats, existing evidences for the abilities of these species to host, sustain intraspecific transmission, and generate novel flu A lineages through genomic reassortment. Such enhanced understanding suggests a need to reinforce surveillance of the role played by companion animals-human interface, in light of the “One Health” concept and the potential emergence of novel zoonotic viruses.

Global spatial risk pattern of highly pathogenic avian influenza H5N1 virus in wild birds: A knowledge-fusion based approach

Highly pathogenic avian influenza (HPAI) H5N1 viruses have continuously circulated throughout much of the world since 2003, resulting in huge economic losses and major public health problems. Wild birds have played an important role in the spread of H5N1 HPAI. To understand its spatial distribution, H5N1 HPAI have been studied by many disciplines from different perspectives, but only one kind of disciplinary knowledge was involved, which has provided limited progress in understanding. Combining risk information from different disciplines based on knowledge fusion can provide more accurate and detailed information. In this study, local k function, phylogenetic tree analysis, and logistic spatial autoregressive models were used to explore the global spatial pattern of H5N1 HPAI based on outbreak data in wild birds, genetic sequences, and risk factors, respectively. On this basis, Dempster-Shafer (D-S) evidence theory was further applied to study the spatial distribution of H5N1 HPAI. We found D-S evidence theory was more robust and reliable than the other three methods, providing technical and methodological support for application to the research of other diseases. The shortest distance to wild bird migration routes, roads and railways, elevation, the normalized difference vegetation index (NDVI), land use and land cover (LULC) and infant mortality rates (IMR) were significantly associated with the occurrence of H5N1 HPAI. The high-risk areas were mainly located in Northern and Central Europe, the eastern Mediterranean, and East and Southeast Asia. High-risk clusters were closely related to the social, economic and ecological environment of the region. Locations where the potential transmission risk remains high should be prioritized for control efforts.

Epidemiological Risk Factors for Animal Influenza A Viruses Overcoming Species Barriers

Drivers and risk factors for Influenza A virus transmission across species barriers are poorly understood, despite the ever present threat to human and animal health potentially on a pandemic scale. Here we review the published evidence for epidemiological risk factors associated with influenza viruses transmitting between animal species and from animals to humans. A total of 39 papers were found with evidence of epidemiological risk factors for influenza virus transmission from animals to humans; 18 of which had some statistical measure associated with the transmission of a virus. Circumstantial or observational evidence of risk factors for transmission between animal species was found in 21 papers, including proximity to infected animals, ingestion of infected material and potential association with a species known to carry influenza virus. Only three publications were found which presented a statistical measure of an epidemiological risk factor for the transmission of influenza between animal species. This review has identified a significant gap in knowledge regarding epidemiological risk factors for the transmission of influenza viruses between animal species.

Single-Stranded RNA Viruses

In this chapter, we describe 73 zoonotic viruses that were isolated in Northern Eurasia and that belong to the different families of viruses with a single-stranded RNA (ssRNA) genome. The family includes viruses with a segmented negative-sense ssRNA genome (families Bunyaviridae and Orthomyxoviridae) and viruses with a positive-sense ssRNA genome (families Togaviridae and Flaviviridae). Among them are viruses associated with sporadic cases or outbreaks of human disease, such as hemorrhagic fever with renal syndrome (viruses of the genus Hantavirus), Crimean–Congo hemorrhagic fever (CCHFV, Nairovirus), California encephalitis (INKV, TAHV, and KHATV; Orthobunyavirus), sandfly fever (SFCV and SFNV, Phlebovirus), Tick-borne encephalitis (TBEV, Flavivirus), Omsk hemorrhagic fever (OHFV, Flavivirus), West Nile fever (WNV, Flavivirus), Sindbis fever (SINV, Alphavirus) Chikungunya fever (CHIKV, Alphavirus) and others. Other viruses described in the chapter can cause epizootics in wild or domestic animals: Geta virus (GETV, Alphavirus), Influenza A virus (Influenzavirus A), Bhanja virus (BHAV, Phlebovirus) and more. The chapter also discusses both ecological peculiarities that promote the circulation of these viruses in natural foci and factors influencing the occurrence of epidemic and epizootic outbreaks

High doses of highly pathogenic avian influenza virus in chicken meat are required to infect ferrets

High pathogenicity avian influenza viruses (HPAIV) have caused fatal infections in mammals through consumption of infected bird carcasses or meat, but scarce information exists on the dose of virus required and the diversity of HPAIV subtypes involved. Ferrets were exposed to different HPAIV (H5 and H7 subtypes) through consumption of infected chicken meat. The dose of virus needed to infect ferrets through consumption was much higher than via respiratory exposure and varied with the virus strain. In addition, H5N1 HPAIV produced higher titers in the meat of infected chickens and more easily infected ferrets than the H7N3 or H7N7 HPAIV.

Acute bronchointerstitial pneumonia in two indoor cats exposed to the H1N1 influenza virus

OBJECTIVE

To describe 2 cases of acute bronchointerstitial pneumonia in indoor domestic cats infected by anthroponotic transmission of pandemic 2009 influenza A H1N1 virus from their owners.

CASE SERIES SUMMARY

Two indoor domestic shorthair cats from the same household were evaluated for acute onset of respiratory distress. The owners had been recovering from flu-like illness at the time of presentation. Venous blood gas showed increased pvCO2 while thoracic radiographs revealed severe bronchointerstitial to alveolar patterns in both cats. The cats were treated with oxygen supplementation, antimicrobials, analgesics, diuretics, corticosteroids, bronchodilators, mechanical ventilation (1 cat), and supportive care. Despite initial improvement in the clinical condition of each cat, respiratory function deteriorated and ultimately both cats were euthanized. Gross and histopathologic examination confirmed diffuse, severe bronchointerstitial pneumonia. Pandemic 2009 influenza A H1N1 viral testing by real time PCR was positive in 1 cat.

NEW OR UNIQUE INFORMATION PROVIDED

These cases provide further evidence that domestic felids are susceptible to pandemic 2009 influenza A H1N1 virus, and the literature is briefly reviewed for treatment recommendations. H1N1 should be considered in the differential diagnosis for domestic cats presenting with peracute to acute onset of respiratory distress in the right context. While human-to-cat transmission of H1N1 seems probable in several reported cases, cat-to-human transmission has not been identified.

Lung cytokine gene expression is correlated with increased severity of disease in a novel H4N8 influenza virus isolated from shorebirds

The lung cytokine gene expression profiles of mice infected with 2 strains of H4N8 viruses isolated from shorebirds and reference H4 viruses from ducks are compared. Major differences between the two H4N8 strains of shorebirds, one of which causes a severe respiratory disease in mice, are in the PB1 and NS1 genes. In mice with H4N8 virus induced pneumonia, overall expression of TNF-α, IL-6 and IL-12 genes was markedly higher than in mice infected with other H4 viruses tested, although gene expression of type I interferon was not increased until day 4 post viral infection. In contrast, in mice infected with a comparison H4N8 strain, gene expression of type I interferon peaked on day 1 post viral infection. Overall, the cytokine response corresponds with the severity of disease caused by shorebird H4N8 virus. The results obtained in this study provide valuable information to understand the immunopathology induced by a low pathogenic avian influenza virus, which may be useful in preparation for outbreaks of novel influenza A virus.

A novel canine influenza H3N2 virus isolated from cats in an animal shelter

The interspecies transmission of avian-origin H3N2 canine influenza virus (CIV) to dogs was first reported in 2007. The present study characterized a novel CIV H3N2 isolated from cats in an animal shelter. A comparative analysis of the deduced amino acid sequences of the A/Canine/Korea/CY009/2010(H3N2) (CY009) and A/Feline/Korea/FY028/2010 (H3N2) (FY028) strains isolated from dogs and cats, respectively, in the animal shelter identified point mutations in 18 amino acid positions within eight viral genes. Interestingly, CY009 and FY028 replicated well in specific pathogen-free embryonated chicken eggs and in mice, respectively. Mice infected with the FY028 strain exhibited significant over expression of IL-10, TNF-α, and IFN-γ (p<0.001) at 3 days postinfection. Thus, an emergency monitoring system should be developed to identify influenza mutations that occur during interspecies transmission in companion animals and for continuous public health surveillance.

Bringing together emerging and endemic zoonoses surveillance: shared challenges and a common solution

Early detection of disease outbreaks in human and animal populations is crucial to the effective surveillance of emerging infectious diseases. However, there are marked geographical disparities in capacity for early detection of outbreaks, which limit the effectiveness of global surveillance strategies. Linking surveillance approaches for emerging and neglected endemic zoonoses, with a renewed focus on existing disease problems in developing countries, has the potential to overcome several limitations and to achieve additional health benefits. Poor reporting is a major constraint to the surveillance of both emerging and endemic zoonoses, and several important barriers to reporting can be identified: (i) a lack of tangible benefits when reports are made; (ii) a lack of capacity to enforce regulations; (iii) poor communication among communities, institutions and sectors; and (iv) complexities of the international regulatory environment. Redirecting surveillance efforts to focus on endemic zoonoses in developing countries offers a pragmatic approach that overcomes some of these barriers and provides support in regions where surveillance capacity is currently weakest. In addition, this approach addresses immediate health and development problems, and provides an equitable and sustainable mechanism for building the culture of surveillance and the core capacities that are needed for all zoonotic pathogens, including emerging disease threats.

Domestic cats are susceptible to infection with low pathogenic avian influenza viruses from shorebirds

Domestic cats are susceptible to infection with highly pathogenic avian influenza virus H5N1, resulting in pneumonia and in some cases, systemic spread with lesions in multiple organ systems. Recent transmission of the 2009 pandemic H1N1 influenza virus from humans to cats also resulted in severe pneumonia in cats. Data regarding the susceptibility of cats to other influenza viruses is minimal, especially regarding susceptibility to low pathogenic avian influenza viruses from wild birds, the reservoir host. In this study, the authors infected 5-month-old cats using 2 different North American shorebird avian influenza viruses (H1N9 and H6N4 subtypes), 3 cats per virus, with the goal of expanding the understanding of avian influenza virus infections in this species. These viruses replicated in inoculated cats based on virus isolation from the pharynx in 2 cats, virus isolation from the lung of 1 cat, and antigen presence in the lung via immunohistochemistry in 2 cats. There was also seroconversion and lesions of patchy bronchointerstitial pneumonia in all of the cats. Infection in the cats did not result in clinical disease and led to variable pharyngeal viral shedding with only 1 of the viruses; virus was localized in the alveolar epithelium via immunohistochemistry. These findings demonstrate the capacity of wild bird influenza viruses to infect cats, and further investigation is warranted into the pathogenesis of these viruses in cats from both a veterinary medical and public health perspective.

Surveillance of feral cats for influenza A virus in north central Florida

BACKGROUND

Transmission of highly pathogenic avian influenza and the recent pandemic H1N1 viruses to domestic cats and other felids creates concern because of the morbidity and mortality associated with human infections as well as disease in the infected animals. Experimental infections have demonstrated transmission of influenza viruses in cats.

OBJECTIVES

An epidemiologic survey of feral cats was conducted to determine their exposure to influenza A virus.

METHODS

Feral cat sera and oropharyngeal and rectal swabs were collected from November 2008 through July 2010 in Alachua County, FL and were tested for evidence of influenza A virus infection by virus isolation, PCR, and serological assay.

RESULTS AND CONCLUSIONS

No virus was isolated from any of 927 cats examined using MDCK cell or embryonated chicken egg culture methods, nor was viral RNA detected by RT-PCR in 200 samples tested. However, 0.43% of cats tested antibody positive for influenza A by commercial ELISA. These results suggest feral cats in this region are at minimal risk for influenza A virus infection.

Low pathogenic avian influenza isolates from wild birds replicate and transmit via contact in ferrets without prior adaptation

Direct transmission of avian influenza viruses to mammals has become an increasingly investigated topic during the past decade; however, isolates that have been primarily investigated are typically ones originating from human or poultry outbreaks. Currently there is minimal comparative information on the behavior of the innumerable viruses that exist in the natural wild bird host. We have previously demonstrated the capacity of numerous North American avian influenza viruses isolated from wild birds to infect and induce lesions in the respiratory tract of mice. In this study, two isolates from shorebirds that were previously examined in mice (H1N9 and H6N1 subtypes) are further examined through experimental inoculations in the ferret with analysis of viral shedding, histopathology, and antigen localization via immunohistochemistry to elucidate pathogenicity and transmission of these viruses. Using sequence analysis and glycan binding analysis, we show that these avian viruses have the typical avian influenza binding pattern, with affinity for cell glycoproteins/glycolipids having terminal sialic acid (SA) residues with α 2,3 linkage [Neu5Ac(α2,3)Gal]. Despite the lack of α2,6 linked SA binding, these AIVs productively infected both the upper and lower respiratory tract of ferrets, resulting in nasal viral shedding and pulmonary lesions with minimal morbidity. Moreover, we show that one of the viruses is able to transmit to ferrets via direct contact, despite its binding affinity for α 2,3 linked SA residues. These results demonstrate that avian influenza viruses, which are endemic in aquatic birds, can potentially infect humans and other mammals without adaptation. Finally this work highlights the need for additional study of the wild bird subset of influenza viruses in regard to surveillance, transmission, and potential for reassortment, as they have zoonotic potential.

Marked endotheliotropism of highly pathogenic avian influenza virus H5N1 following intestinal inoculation in cats

Highly pathogenic avian influenza virus (HPAIV) H5N1 can infect mammals via the intestine; this is unusual since influenza viruses typically infect mammals via the respiratory tract. The dissemination of HPAIV H5N1 following intestinal entry and associated pathogenesis are largely unknown. To assess the route of spread of HPAIV H5N1 to other organs and to determine its associated pathogenesis, we inoculated infected chicken liver homogenate directly into the intestine of cats by use of enteric-coated capsules. Intestinal inoculation of HPAIV H5N1 resulted in fatal systemic disease. The spread of HPAIV H5N1 from the lumen of the intestine to other organs took place via the blood and lymphatic vascular systems but not via neuronal transmission. Remarkably, the systemic spread of the virus via the vascular system was associated with massive infection of endothelial and lymphendothelial cells, resulting in widespread hemorrhages. This is unique for influenza in mammals and resembles the pathogenesis of HPAIV infection in terrestrial poultry. It contrasts with the pathogenesis of systemic disease from the same virus following entry via the respiratory tract, where lesions are characterized mainly by necrosis and inflammation and are associated with the presence of influenza virus antigen in parenchymal, not endothelial cells. The marked endotheliotropism of the virus following intestinal inoculation indicates that the pathogenesis of systemic influenza virus infection in mammals may differ according to the portal of entry.

Surveillance for highly pathogenic avian influenza in wild birds in the USA

As part of the USA's National Strategy for Pandemic Influenza, an Interagency Strategic Plan for the Early Detection of Highly Pathogenic H5N1 Avian Influenza in Wild Migratory Birds was developed and implemented. From 1 April 2006 through 31 March 2009, 261,946 samples from wild birds and 101,457 wild bird fecal samples were collected in the USA; no highly pathogenic avian influenza was detected. The United States Department of Agriculture, and state and tribal cooperators accounted for 213,115 (81%) of the wild bird samples collected; 31, 27, 21 and 21% of the samples were collected from the Atlantic, Pacific, Central and Mississippi flyways, respectively. More than 250 species of wild birds in all 50 states were sampled. The majority of wild birds (86%) were dabbling ducks, geese, swans and shorebirds. The apparent prevalence of low pathogenic avian influenza viruses during biological years 2007 and 2008 was 9.7 and 11.0%, respectively. The apparent prevalence of H5 and H7 subtypes across all species sampled were 0.5 and 0.06%, respectively. The pooled fecal samples (n= 101,539) positive for low pathogenic avian influenza were 4.0, 6.7 and 4.7% for biological years 2006, 2007 and 2008, respectively. The highly pathogenic early detection system for wild birds developed and implemented in the USA represents the largest coordinated wildlife disease surveillance system ever conducted. This effort provided evidence that wild birds in the USA were free of highly pathogenic avian influenza virus (given the expected minimum prevalence of 0.001%) at the 99.9% confidence level during the surveillance period.

Lower respiratory tract infections in cats: reaching beyond empirical therapy

PRACTICAL RELEVANCE

Lower respiratory tract infections (LRTIs) in cats can be due to bacteria, parasites, fungi and viruses. This review details the practical investigation of these infections and highlights specific therapy where possible. The aim is to avoid the all-too-frequent temptation in practice to treat cats with lower respiratory tract signs empirically for feline bronchial disease (FBD)/asthma. This is potentially hazardous as immunosuppressive therapy for FBD/asthma could exacerbate disease due to a LRTI. Empirical treatment of suspected LRTI is also difficult to recommend given the wide range of potential pathogens.

CLINICAL CHALLENGES

Making a clinical ante-mortem diagnosis of LRTI in a cat can be challenging. Consistent historical, clinical, haematological and radiographic abnormalities are often lacking and findings may be non-specific. Astute clinical acumen, thorough investigation and high quality laboratory analysis are usually required for a diagnosis. Bronchoalveolar lavage, if feasible, and tests for lungworm should be routine in cats with lower respiratory tract signs. Lung fine needle aspiration may be useful in cases of diffuse or nodular pulmonary disease. Histopathology is rarely employed in ante-mortem investigations.

EVIDENCE BASE

The authors have reviewed a substantial body of literature to provide information on many of the reported bacterial, parasitic, fungal and viral pathogens, including some that occur in Asia. Attention has been given to specific therapy for each pathogen, with evidence-based comments when there is a deviation from routine recommendations.

Fatal pandemic (H1N1) 2009 influenza A virus infection in a Pennsylvania domestic cat

We report the earliest recognized fatality associated with laboratory-confirmed pandemic H1N1 (pH1N1) influenza in a domestic cat in the United States. The 12-year old, indoor cat died on 6 November 2009 after exposure to multiple family members who had been ill with influenza-like illness during the peak period of the fall wave of pH1N1 in Pennsylvania during late October 2009. The clinical presentation, history, radiographic, laboratory and necropsy findings are presented to assist veterinary care providers in understanding the features of this disease in cats and the potential for transmission of infection to pets from infected humans.

An emerging pulmonary haemorrhagic syndrome in dogs: similar to the human leptospiral pulmonary haemorrhagic syndrome?

Severe pulmonary haemorrhage is a rare necropsy finding in dogs but the leptospiral pulmonary haemorrhagic syndrome (LPHS) is a well recognized disease in humans. Here we report a pulmonary haemorrhagic syndrome in dogs that closely resembles the human disease. All 15 dogs had massive, pulmonary haemorrhage affecting all lung lobes while haemorrhage in other organs was minimal. Histologically, pulmonary lesions were characterized by acute, alveolar haemorrhage without identifiable vascular lesions. Seven dogs had mild alveolar wall necrosis with hyaline membranes and minimal intraalveolar fibrin. In addition, eight dogs had acute renal tubular necrosis. Six dogs had a clinical diagnosis of leptospirosis based on renal and hepatic failure, positive microscopic agglutination test (MAT) and/or positive blood/urine Leptospira-specific PCR. Leptospira could not be cultured post mortem from the lungs or kidneys. However, Leptospira-specific PCR was positive in lung, liver or kidneys of three dogs. In summary, a novel pulmonary haemorrhagic syndrome was identified in dogs but the mechanism of the massive pulmonary erythrocyte extravasation remains elusive. The lack of a consistent post mortem identification of Leptospira spp. in dogs with pulmonary haemorrhage raise questions as to whether additional factors besides Leptospira may cause this as yet unrecognized entity in dogs.

Highly pathogenic avian influenza virus H7N7 isolated from a fatal human case causes respiratory disease in cats but does not spread systemically

Highly pathogenic avian influenza viruses (HPAIV) of the H5 and H7 subtypes primarily infect poultry but are occasionally transmitted to humans and other mammalian species, often causing severe disease. Previously we have shown that HPAIV H5N1 causes severe systemic disease in cats. In this study, we investigated whether HPAIV H7N7 isolated from a fatal human case is also able to cause disease in cats. Additionally, we compared the cell tropism of both viruses by immunohistochemistry and virus histochemistry. Three domestic cats were inoculated intratracheally with HPAIV H7N7. Virus excretion was restricted to the pharynx. At necropsy, 7 days post inoculation, lesions were restricted to the respiratory tract in all cats. Lesions consisted of diffuse alveolar damage and colocalized with virus antigen expression in type II pneumocytes and nonciliated bronchiolar cells. The attachment patterns of HPAIV H7N7 and H5N1 were similar: both viruses attached to nonciliated bronchiolar epithelial cells, type II pneumocytes, as well as alveolar macrophages. These data show for the first time that a non-H5 HPAIV is able to infect and cause respiratory disease in cats. The failure of HPAIV H7N7 to spread beyond the respiratory tract was not explained by differences in cell tropism compared to HPAIV H5N1. These findings suggest that HPAIV H5N1 possesses other characteristics that allow it to cause systemic disease in both humans and cats.

Systemic influenza virus H5N1 infection in cats after gastrointestinal exposure

BACKGROUND

Highly pathogenic avian influenza virus (HPAIV) H5N1 infections in felids have been reported in several countries. Feeding on infected birds has been suggested as potential source of infection.

OBJECTIVES

The study aimed to verify gastrointestinal infection as possible portal of entry for HPAIV H5N1 in cats.

METHODS

Four cats were infected oculo-nasopharyngeally with 10⁶ 50% egg infectious dose (EID(50) ) of HPAIV H5N1 A/cat/Germany/R606/2006. Two cats were infected intravenously with 10⁶ EID(50) and two cats were inoculated orally with 10⁷ EID(50) HPAIV embedded in gelatine capsules to mimic gastrointestinal exposure and to avoid virus contact to oropharyngeal or respiratory tissues. Cats were monitored for 6 days by physical examination, virus excretion, and peripheral blood lymphocyte counts. Blood chemical parameters (including AST, ALT, CPK, and TBIL) and viral excretion using pharyngeal and rectal swabs were analyzed.

RESULTS

Infected cats showed elevated body temperature up to 41·3°C starting from day 1 or 2 p.i. All infected cats excreted virus in pharyngeal swabs within 2 days p.i. co-inciding with the development of clinical signs (anorexia, depression, and labored breathing) irrespective of the infection route. Virus dissemination occurred through cell-free and cell-associated viremia. Infected cats developed lymphopenia, hepatic necrosis, pneumonia, and significantly elevated levels of aspartate aminotransferase (AST), alanine aminotransferase (ALT), creatine phosphokinase (CPK), and TBIL.

CONCLUSIONS

The experiments show that the gastrointestinal tract can serve as portal for the entry of HPAIV H5N1 into cats. Infection routes used did not influence viral tissue tropism and course of disease.

Dogs are highly susceptible to H5N1 avian influenza virus

Replication of avian influenza viruses (AIVs) in dogs may facilitate their adaptation in humans; however, the data to date on H5N1 influenza virus infection in dogs are conflicting. To elucidate the susceptibility of dogs to this pathogen, we infected two groups of 6 beagles with 10(6) 50% egg-infectious dose of H5N1 AIV A/bar-headed goose/Qinghai/3/05 (BHG/QH/3/05) intranasally (i.n.) and intratracheally (i.t.), respectively. The dogs showed disease symptoms, including anorexia, fever, conjunctivitis, labored breathing and cough, and one i.t. inoculated animal died on day 4 post-infection. Virus shedding was detected from all 6 animals inoculated i.n. and one inoculated i.t. Virus replication was detected in all animals that were euthanized on day 3 or day 5 post-infection and in the animal that died on day 4 post-infection. Our results demonstrate that dogs are highly susceptible to H5N1 AIV and may serve as an intermediate host to transfer this virus to humans.

Cross-clade immunity in cats vaccinated with a canarypox-vectored avian influenza vaccine

Several felid species have been shown to be susceptible to infection with highly pathogenic avian influenza (HPAI) viruses of the H5N1 subtype. Infection of felids by H5N1 HPAI virus is often fatal, and cat-to-cat transmission has been documented. Domestic cats may then be involved in the transmission of infection to other animals but also to humans. A particular concern is the hypothetical role of the cat in the adaptation of the virus to mammalian species, thus increasing the pandemic risk. Therefore, the development of a HPAI vaccine for domestic cats should be considered a veterinary and also a public health priority. Here we show that vaccination of cats with a recombinant canarypox (ALVAC)(1)) virus, expressing the hemagglutinin (HA) of influenza virus A/chicken/Indonesia/03 (H5N1) confers protection against challenge infection with two antigenically distinct H5N1 virus isolates from humans. Despite low hemagglutination inhibiting (HI) antibody titers at the time of challenge, all vaccinated cats were protected against mortality and had reduced histopathological changes in the lungs. Importantly, viral shedding was reduced in vaccinated cats as compared to controls, suggesting that vaccination of cats could reduce the risk of viral transmission. In conclusion this study showed that the recombinant canarypox virus protected cats against homologous and heterologous H5N1 HPAI virus challenges.

Pathology and viral antigen distribution of lethal pneumonia in domestic cats due to pandemic (H1N1) 2009 influenza A virus

A novel swine-origin H1N1 influenza A virus has been identified as the cause of the 2009 influenza pandemic in humans. Since then, infections with the pandemic (H1N1) 2009 influenza virus have been documented in a number of animal species. The first known cases of lethal respiratory disease associated with pandemic (H1N1) 2009 influenza virus infection in house pets occurred in domestic cats in Oregon. A 10-year-old neutered domestic shorthair and an 8-year-old spayed domestic shorthair died shortly after developing severe respiratory disease. Grossly, lung lobes of both cats were diffusely firm and incompletely collapsed. Histologically, moderate to severe necrotizing to pyonecrotizing bronchointerstitial pneumonia was accompanied by serofibrinous exudation and hyaline membranes in the alveolar spaces. Influenza A virus was isolated from nasal secretions of the male cat and from lung homogenate of the female cat. Both isolates were confirmed as pandemic (H1N1) 2009 influenza virus by real-time reverse transcriptase polymerase chain reaction. With immunohistochemistry, influenza A viral antigen was demonstrated in bronchiolar epithelial cells, pneumocytes, and alveolar macrophages in pneumonic areas. The most likely sources of infection were people in the household with influenza-like illness or confirmed pandemic (H1N1) 2009 influenza. The 2 cases reported here provide, to the best of the authors' knowledge, the first description of the pathology and viral antigen distribution of lethal respiratory disease in domestic cats after natural pandemic (H1N1) 2009 influenza virus infection, probably transmitted from humans.

Serological survey for influenza type A viruses in domestic dogs (Canis lupus familiaris) and cats (Felis catus) in north-eastern Italy

To ascertain the potential transmission of influenza A viruses to dogs and cats, a serological survey was carried out in North-eastern Italy. In a 4-year period, 637 serum samples were screened using a Mab-based competitive ELISA for anti-nucleoprotein A (NPA) antibody detection of influenza viruses. No evidence of anti-NPA antibodies was observed.

Influenza virus infections in dogs and cats

During the last decade reports of influenza A virus infections in dogs and cats draw considerable attention to veterinary practitioners and scientists in the fields of virology and epidemiology. Earlier experimental studies showed that dogs and cats are susceptible to influenza A virus infection, but animals did not develop clinical signs. In recent years transmission of influenza virus of subtype H3N8 from horses to dogs, however, was accompanied by severe clinical signs and the infection was shown to be transmitted to other pet dog populations in the US. In Asia respiratory disease caused by influenza virus H3N2 was documented in dogs and also a fatal infection with the highly pathogenic avian influenza virus (HPAIV) H5N1 was reported. Transmission of HPAIV H5N1 from infected poultry or wild birds to large felids and domestic cats has been reported from eight countries in Asia and Europe which caused considerable problems and concerns for both veterinary and public health in recent years. Experimentally the infection could also be transmitted from diseased to naive cats. Due to the heterogeneity of influenza viruses in their natural reservoirs of water fowl and the recent clinical natural infections in carnivores with influenza viruses of the subtypes H3 and H5, influenza virus infections should also be considered in dogs and cats with lower respiratory disease. The transmission of influenza A virus to carnivores from different mammalian and avian species may allow viral adaptation and therefore the epidemiological role of infected dogs and cats needs close attention.

Polyganglioradiculoneuritis in a young cat: clinical and histopathological findings

An 18-month-old European shorthair cat was presented with a two week history of progressive decrease in consciousness, ambulatory tetraparesis, moderate ataxia and generalised decreased-to-absent postural reactions. Bilateral facial and nasal hypalgesia, absent menace response and anisocoria were found, and segmental spinal reflexes were normal. Neurological signs progressed to nonambulatory tetraparesis, tremor and spinal hyperalgesia. Histopathological examination revealed a mild-to-moderate lymphoplasmacytic and histiocytic infiltration, predominantly in the dorsal spinal roots, cranial nerves and ganglia in association with marked demyelination and proliferation of Schwann cells. Neurons and axons were preserved. Lesions were multi-focal and varied in severity. A predominantly sensory polyganglioradiculoneuritis was diagnosed. This lesion has not been reported previously in cats. Rabies, herpesviruses, feline infectious peritonitis, feline immunodeficiency virus, Toxoplasma gondii and feline leukaemia virus were excluded as possible aetiologies. Infections by other viruses or an autoimmune disease are discussed.

H5N1 avian influenza in cats. ABCD guidelines on prevention and management

OVERVIEW

Avian influenza is a disease of birds, caused by a type A influenza virus. The subtype H5N1 avian influenza occurs primarily in birds and infection varies from mild disease with little or no mortality to a highly fatal, rapidly spreading epidemic (highly pathogenic avian influenza). It is extremely rare for cats to be infected and there are only very few confirmed reports of the disease in cats in Europe.

INFECTION

Cats can be infected via the respiratory and oral routes (eg, by eating infected birds). The key precondition for infection is that the cat lives in an area where H5N1 virus infection has been confirmed in birds. Additionally, the cat should have had outdoor access to an environment where waterfowl is present, or contact with poultry or uncooked poultry meat, or close contact with an H5N1-infected, sick cat during the first week of infection. CLINICAL SUSPICION: Clinical signs in cats may include fever, lethargy, dyspnoea, conjunctivitis and rapid death. Neurological signs (circling, ataxia) have also been recorded.

DIAGNOSIS

The veterinary authorities should be notified. Oropharyngeal, nasal and/or rectal swabs or faecal samples of suspected cases should be submitted for PCR and/or virus isolation. Post-mortem samples of lung and mediastinal lymph nodes should be obtained. Particular care should be taken when handling the cat and/or samples.

DISEASE MANAGEMENT

The virus is sensitive to all standard medical disinfectants. Cats with suspected H5N1 infection should be kept in strict isolation. Owners should be advised to confine the cat to a separate room prior to bringing it to the veterinary clinic. VACCINATION AND DISEASE PREVENTION: No H5N1 vaccines are commercially available for cats. In the event of confirmed cases of H5N1 avian influenza in birds in the area, owners should keep their cats indoors until further information is available, and follow official regulations.

Highly pathogenic avian influenza virus (H5N1) infection in red foxes fed infected bird carcasses

Foxes experimentally fed infected bird carcasses excrete virus for >5 days without exhibiting severe disease and may thus disperse the virus.

Eating infected wild birds may put wild carnivores at high risk for infection with highly pathogenic avian influenza (HPAI) virus (H5N1). To determine whether red foxes (Vulpes vulpes) are susceptible to infection with HPAI virus (H5N1), we infected 3 foxes intratracheally. They excreted virus pharyngeally for 3–7 days at peak titers of 10^3.5–10^5.2 median tissue culture infective dose (TCID₅₀) per mL and had severe pneumonia, myocarditis, and encephalitis. To determine whether foxes can become infected by the presumed natural route, we fed infected bird carcasses to 3 other red foxes. These foxes excreted virus pharyngeally for 3–5 days at peak titers of 10^4.2–10^4.5 TCID₅₀/mL, but only mild or no pneumonia developed. This study demonstrates that red foxes fed bird carcasses infected with HPAI virus (H5N1) can excrete virus while remaining free of severe disease, thereby potentially playing a role in virus dispersal.

A network model of H5N1 avian influenza transmission dynamics in domestic cats

Naturally occurring cases of influenza in cats owing to the H5N1 strain have been reported in several countries. A cat reservoir of H5N1 in the United States could provide an environment for zoonotic disease spread to humans. This scenario was the impetus to develop a model to study potential transmission of H5N1 virus in domestic cats utilizing information on cat ownership and cat-cat interaction patterns, in addition to biological properties of the virus. The roaming behaviour of cats significantly influenced epidemic dynamics, as demonstrated by the simulation results from this model. A better understanding of the behaviour of domestic cats and the H5N1 influenza virus can be used to predict epidemic dynamics following the introduction of H5N1 virus into the United States and to develop effective strategies to prevent virus transmission to both cats and humans.

Evaluation of a point-of-care influenza antigen test for the detection of highly pathogenic avian influenza H5N1 virus in cats

Quick diagnosis of H5N1 infection in cats is important because of the zoonotic and pandemic potential of this virus. Human rapid influenza antigen tests are also sold commercially to veterinarians for use in cats. The point-of-care test actim(trade mark) Influenza A&B (Medix Biochemica, Kauniainen, Finland) was evaluated for the diagnosis of H5N1 infection in cats. The test showed a very low sensitivity and did not detect virus in samples of experimentally infected cats, so that its application cannot be recommended for the diagnosis of H5N1 infection in cats.

The first specific detection of a highly pathogenic avian influenza virus (H5N1) in Ivory Coast

The Virology Laboratory of the Central Laboratory of Animal Diseases in Ivory Coast at Bingerville received samples of wild and domestic avian species between February and December 2006. An RT-PCR technique was used to test for avian influenza (AI) and highly pathogenic AI subtype viruses. Among 2125 samples, 16 were type A positive; of which, 12 were later confirmed to be H5N1. Fifteen of these 16 type A positive samples were inoculated into the chorioallantoic cavity of 11-day-old embryonated hens' eggs for virus isolation. Eight produced virus with hemagglutination titres from 1/64 to 1/512. The 4/16 M-RT-PCR positive samples, which were H5N1 negative, were shown to be H7 subtype negative. The diagnostic efficiency of the laboratory for the surveillance of H5N1 in Ivory Coast was demonstrated. The positive cases of H5N1 were from a sparrowhawk (Accipter nisus); live market poultry and in free-range poultry, where the mortality rate was approximately 20% (2/10) and 96.7% (29/30) respectively. Currently, investigations into intensive poultry farms have proved negative for H5N1. No human cases have been reported this time.

Prevalence of influenza A H5N1 virus in cats from areas with occurrence of highly pathogenic avian influenza in birds

Natural and experimental infections have shown that cats are susceptible to highly pathogenic avian influenza A virus subtype H5N1 (HPAIV H5N1). Cats can be severely affected and die from the disease, but subclinical infections have also been reported. To learn more about the role of cats in the spread of the virus and about the risk posed to cats, the prevalence of H5N1 virus was examined in 171 cats from areas in Germany and Austria in which birds infected with HPAIV H5N1 had been found. Pharyngeal swabs were examined for H5N1 virus using real-time polymerase chain reaction, and serum samples were tested for antibodies to influenza virus. None of the cats showed evidence of infection with H5N1 virus. Prevalence of H5N1 virus was determined to be <1.8% (95% confidence interval (CI): 0.000000-0.017366); prevalence of antibodies was <2.6% (95% CI: 0.000000-0.025068).

Avian influenza A H5N1 infections in cats

Although cats had been considered resistant to disease from influenza virus infection, domestic cats and large felids are now known to be naturally und experimentally susceptible to infection with highly pathogenic avian influenza virus H5N1 (HPAIV H5N1). The virus causes systemic infection, lung and liver being the mainly affected organs. Infected cats show fever, depression, dyspnoea, and neurological signs, but subclinical infections have also occurred. Mostly, cats have been infected by direct contact with affected birds, especially by eating raw poultry; transmission from cat to cat may also occur. Little is known about the role of cats in the epidemiology of the virus. So far, no reassortment between avian and mammalian influenza viruses has occurred in cats, but experts fear that cats might give the virus an opportunity to adapt to mammals. This publication gives a review on avian influenza in cats with a focus on practical aspects for veterinarians.