In spring 2022, Europe faced an unprecedented heatwave, increasing the risk of West Nile virus (WNV) outbreaks. As early as 7 June 2022, WNV was detected in Culex mosquitoes in northern Italy, and – in the following days – in two blood donors, a patient with encephalitis, wild birds and additional mosquito pools. Genome sequencing demonstrated co-circulation of WNV lineage 2 and a newly introduced WNV lineage 1, which was discovered in the region in 2021.

Since 1997, G1-lineage H9N2 avian influenza viruses have been circulating in Asia and later on in the Middle East, and they have been associated to mild respiratory disease, drops in egg production and moderate mortality in chickens, in particular in the presence of concurrent infections. In this study, we investigated the importance of the G1-lineage H9N2 A/chicken/Israel/1163/2011 virus as a primary pathogen in layers, analyzing its tropism and binding affinity for the oviduct tissues, and investigating the long-term impact on egg production. Besides causing a mild respiratory infection, the virus replicated in the oviduct of 60% of the hens causing different degrees of salpingitis throughout the organ, in particular at the level of the infundibulum, where the detection of the virus was associated with severe heterophilic infiltrate, and necrosis of the epithelium. Binding affinity assays confirmed that the infundibulum was the most receptive region of the oviduct. The drop in egg production was at its peek at 2 weeks post-infection (pi) (60% decrease) and continued up to 80 days pi (35% decrease). On day 80 pi, non-laying birds showed egg yolk peritonitis, and histopathological analyses described profound alteration of the infundibulum architecture, duct ectasia and thinning of the epithelium, while the rest of the oviduct and ovary appeared normal. Our results show that this H9N2 virus is a primary pathogen in layer hens, and that its replication in the infundibulum is responsible for acute and chronic lesions that limits the effective functionality of the oviduct, compromising the commercial life of birds.

Background. A new strain of WNV lineage 1 (WNV − 1) emerged in the Veneto Region, northern Italy, in 2021, eight years after the last outbreak of WNV − 1 in Italy. The virus, which co-circulates with WNV-2, has become endemic in the Region, where, in 2022, most human cases of neuroinvasive disease (WNND) reported in Europe have occurred. Methods. Comparative analysis of the epidemiology and clinical presentation of WNV-1 and WNV-2 infection in humans, as well as the temporal and geographic distribution of WNV-1 and WNV-2 among wild birds and Culex pipiens mosquitoes in Veneto, from May 16^th to August 21^st, 2022, to determine if the high number of WNND cases was associated with WNV-1. Results. As of August 21^st, 2022, 222 human cases of WNV infection were confirmed by molecular testing, including 103 with fever (WNF) and 119 with WNND. WNV lineage was determined in 201 (90.5%) cases, comprising 138 WNV-1 and 63 WNV-2 infections. During the same period, 35 blood donors tested positive, including 30 in whom WNV lineage was determined (13 WNV-1 and 17 WNV-2). Comparative analysis of the distribution of WNV-1 and WNV-2 infections among WNND cases, WNF cases and WNV-positive blood donors showed that patients with WNND were more likely to have WNV-1 infection than blood donors (odds ratio 3.44; 95% CI 95% 1.54 to 8.24; p = 0.0043). As observed in humans, in wild birds WNV-1 had higher infectious rate (IR) and showed a more rapid expansion than WNV-2. At variance, the distribution of the two lineages was more even in mosquitoes, but with a trend of rapid increase of WNV-1 IR over WNV-2. Conclusions. Comparative analysis of WNV-1 vs WNV-2 infection in humans, wild birds, and mosquitos showed a rapid expansion of WNV-1 and suggested that WNV-1 infected patients might have an increased risk to develop severe disease.

Since 2006, multiple outbreaks of avian influenza (AI) have been reported in Nigeria involving different subtypes. Surveillance and molecular epidemiology have revealed the vital role of live bird markets (LBMs) in the dissemination of AI virus to commercial poultry farms. To better understand the ecology and epidemiology of AI in Nigeria, we performed whole-genome sequencing of nineteen H9N2 viruses recovered, from apparently healthy poultry species, during active surveillance conducted in nine LBMs across Nigeria in 2019. Analyses of the HA gene segment of these viruses showed that the H9N2 strains belong to the G1 lineage, which has zoonotic potential, and are clustered with contemporary H9N2 identified in Africa between 2016 and 2020. We observed two distinct clusters of H9N2 viruses in Nigeria, suggesting different introductions into the country. In view of the zoonotic potential of H9N2 and the co-circulation of multiple subtypes of AI virus in Nigeria, continuous monitoring of the LBMs across the country and molecular characterization of AIVs identified is advocated to mitigate economic losses and public health threats.

The increasing involvement of wild waterfowl in H5 Highly Pathogenic Avian Influenza Virus (HPAIV) circulation continues to pose a threat to animal and public health worldwide. In winter 2020–2021, two field surveillance activities were carried out on a weekly basis, through virological and serological analyses, in 823 hunted and 521 trapped migratory aquatic birds in northeast Italy. Sixty Eurasian teals were recaptured several times, which allowed us to follow the progression of the HPAI H5 infection in naturally infected wild waterfowl. Oropharyngeal, cloacal, and feather swabs (OS, CS and FS) were collected from each duck and tested by real time rRT-PCR Type A influenza. The identified viruses were characterized and pathotyped by sequencing. Several viruses belonging to three different HPAI H5 subtypes were detected: H5N8, H5N5, and H5N1. High prevalence of infection with HPAI H5 clade 2.3.4.4b during November–December 2020 (up to 27.1%) was observed in captured Eurasian teals, while infection rates in hunted dabbling ducks, mainly Eurasian wigeons, showed the highest prevalence of infection in November 2020 (8.9%) and January 2021 (10.2%). All HPAI positive birds were also clinically healthy when recaptured weeks apart. The OS and FS showed the highest detection efficiency of HPAIV. Our results highlight that HPAI passive surveillance should be complemented by a targeted active surveillance to more efficiently detect novel HPAI viruses.

The role of wild birds in the transmission and spread of mycoplasmas is not clear. Up to now different Mycoplasma species have been isolated from wild birds many of which are not considered pathogens sensu stricto for domestic flocks. This report describes the first isolation of Mycoplasma synoviae in a captive lesser flamingo (Phoeniconaias minor) held in a zoo in Italy and the laboratory investigations performed to elucidate its origin. Results showed that the strain was similar to the MS-H vaccine strain using the vlhA methods although no vaccination with this product was used in the zoo. This paper describes investigations into a case in which 10 of 12 adult lesser flamingos (Phoeniconaias minor) died after having recently been moved from the Netherlands to a new zoo in Northern Italy. While most of the birds appeared to have died from the stress of movement and poor adaptation to their new environment, Mycoplasma synoviae, an important poultry pathogen in the layer and meat industry, was isolated for the first time from the trachea of one animal presenting catarrhal tracheitis and fibrinous airsacculitis. Genetic analysis of the conserved region of the vlhA was not able to differentiate the flamingo strain from the MS-H vaccine strain. However differences in the sequences of the obg gene of the flamingo and vaccine strain were detected. A test for temperature-sensitivity (ts) gave a ts − phenotype for the flamingo strain, in contrast to the ts + status of the MS-H strain. Based on this information and knowing that the flamingos were not vaccinated against M. synoviae, it is highly likely that the flamingo was infected with a genetically similar wild strain by contact with infected birds. This case provides evidence for the potential role of international trade of ornamental birds as a possible route of introduction of new mycoplasma strains between countries, and moreover highlight that vlhA gene sequencing was not sufficient to discriminate the wild strain isolated from the flamingo from the MS-H vaccine strain.