Molecular phylogenetic analysis of Echinococcus granulosus sensu lato infecting sheep in Italy.

Cystic Echinococcosis (CE), caused by the larval form of Echinococcus granulosus sensu lato, is a neglected zoonosis still threatening public health worldwide. In Italy different epidemiological scenarios were reported depending on the geographical area and associated socio-economic activities. Although in northern Italy the occurrence of E. granulosus is considered sporadic, in the southern regions and, particularly in Sardinia, CE prevalence reaches high levels. We analysed CE cysts collected from infected sheep from various areas of mainland Italy and the Sardinia island, with the main objective to investigate intergenotypic and intragenotypic variations at national level. CE cysts were collected from slaughtered sheep following post mortem inspection at local abattoirs. Total genomic DNA was extracted and amplification and sequencing of the partial mitochondrial genes nad5 and cox1 were performed. A Bayesian phylogenetic tree was estimated on a nad5 dataset (n = 260) composed of E. granulosus samples from this study (n = 126) and all the nad5 haplotypes available in GenBank (n = 134). In addition, haplotype network, diversity and neutrality analysis were performed on nad5 and cox1 sequences of Italian origin obtained in this study. E. granulosus sensu stricto (s.s.) was found to be the only Echinococcus species infecting sheep in Italy, mainly represented by G1 genotype (76 %) and, to a lower extent, by G3 genotype (24 %). Phylogenetic analyses revealed 40 nad5 and 33 cox 1 haplotypes, and the presence of two founder haplotypes, belonging to G1 and G3 genotype, showing 100 % similarity with DNA sequences from different geographic regions. The lack of geographical segregation, high haplotype and low nucleotide diversity coupled with significant negative values of Tajima's D and Fu's Fs observed in this study indicated high genetic variation and demographic expansion of E. granulosus s.s. in Italy.

First Reported Circulation of Equine Influenza H3N8 Florida Clade 1 Virus in Horses in Italy.

BACKGROUND: Equine influenza (EI) is a highly contagious viral disease of equids characterized by pyrexia and respiratory signs. Like other influenza A viruses, antigenic drift or shift could lead to a vaccine-induced immunity breakdown if vaccine strains are not updated. The aim of this study was to genetically characterize EIV strains circulating in Italy, detected in PCR-positive samples collected from suspected cases, especially in the absence of formal active surveillance. METHODS: Between February and April 2019, blood samples and nasal swabs collected from each of the 20 symptomatic horses from North and Central Italy were submitted to the National Reference Centre for Equine Diseases in Italy to confirm preliminary analysis performed by other laboratories. RESULTS: None of the sera analysed using haemagglutination inhibition and single radial haemolysis presented a predominant serological reactivity pattern for any antigen employed. All nasal swabs were positive with IAV RRT-PCR. Only one strain, isolated in an embryonated chicken egg from a sample collected from a horse of a stable located in Brescia, Lombardy, was identified as H3N8 Florida lineage clade 1 (FC1). In the constructed phylogenetic trees, this strain is located within the FC1, together with the virus isolated in France in 2018 (MK501761). CONCLUSIONS: This study reports the first detection of H3N8 FC1 in Italy, highlighting the importance of monitoring circulating EIV strains to verify the vaccine composition appropriateness for maximum efficacy.

Primary cerebral cystic echinococcosis in a child from Roman countryside: Source attribution and scoping review of cases from the literature.

BACKGROUND: Human cystic echinococcosis (CE) is a zoonotic parasitic infection caused by the larval stage of the species belonging to the Echinococcus granulosus sensu lato (s.l.) complex. Parasitic cysts causing human CE are mainly localized in the liver and in the lungs. In a smaller number of cases, larvae may establish in any organ or tissue, including the central nervous system (CNS). Cerebral CE (CCE) is rare but poses serious clinical challenges. METHODS: This study presents a case of CCE in a child living in the countryside near Rome (Italy), along with a comparative molecular analysis of the isolated cyst specimens from the patient and sheep of local farms. We also systematically searched the literature to summarize the most relevant epidemiological and clinical aspects of this uncommon localization. FINDINGS: The comparative molecular analysis confirmed that the infection was caused by E. granulosus sensu stricto (s.s.) (G3 genotype), and most likely acquired in the family farm. The literature search identified 2,238 cases of CCE. In 80.51% of cases, brain was the only localization and single CCE cysts were present in 84.07% of cases. Mean patients' age was 20 years and 70.46% were children. Cyst rupture was reported in 12.96% and recurrence of CCE after treatment in 9.61% of cases. Permanent disability was reported in 7.86% of cases, while death occurred in 6.21%. In case series reporting all CE localization, CCE represented 1.5% of all CE cases. In the few reports that identified at molecular level the CCE cyst, E. granulosus s.s. was found in 40% and E. canadensis in 60% of cases. CONCLUSIONS: We report a rare case of CCE and evidenced the probable local origin of infection. The proportions of CE cases with uncommon localizations and with high impact on patients' lives have been globally neglected and should be included in the computation of the global burden of CE.

A multifunctional locus controls motor neuron differentiation through short and long noncoding RNAs.

The transition from dividing progenitors to postmitotic motor neurons (MNs) is orchestrated by a series of events, which are mainly studied at the transcriptional level by analyzing the activity of specific programming transcription factors. Here, we identify a post-transcriptional role of a MN-specific transcriptional unit (MN2) harboring a lncRNA (lncMN2-203) and two miRNAs (miR-325-3p and miR-384-5p) in this transition. Through the use of in vitro mESC differentiation and single-cell sequencing of CRISPR/Cas9 mutants, we demonstrate that lncMN2-203 affects MN differentiation by sponging miR-466i-5p and upregulating its targets, including several factors involved in neuronal differentiation and function. In parallel, miR-325-3p and miR-384-5p, co-transcribed with lncMN2-203, act by repressing proliferation-related factors. These findings indicate the functional relevance of the MN2 locus and exemplify additional layers of specificity regulation in MN differentiation.

Clinical impact, diagnosis and control of Equine Herpesvirus-1 infection in Europe.

Equine herpesvirus-1 (EHV-1) can affect the entire equine sector in EU, and the large outbreak reported in 2021 in Spain drew attention to the needs of the European Commission for scientific advice for the assessment of EHV-1 infection within the framework of Animal Health Law. EHV-1 is considered endemic in the EU; its main risk is linked to the characteristic of producing latent life-long infections. These can reactivate producing clinical disease, which can include respiratory, abortive and possibly fatal neurological forms. From the epidemiological and genomic viewpoint, there are no specific neuropathogenic EHV-1 strains; the respiratory, reproductive and neurological signs are not found to be strain-specific. This was also the case of the virus that caused the outbreak in Valencia (Spain) in 2021, which was genetically closely related to other viruses circulating before in Europe, and did not present the so-called neuropathogenic genotype. The outbreak reported in Valencia was followed by wide geographic spread of the virus possibly due to a delay in diagnosis and late application of biosecurity measures. The recommended and most sensitive diagnostic test for detecting EHV-1 is PCR performed on swabs collected according to the type of clinical signs. Serological assays on paired blood samples can help to detect a recent infection, while no diagnostic methods are available to detect EHV-1 latent infections. Safe movements of horses can be ensured at premovement phase by testing and issuing health certificates, and by isolating animals upon arrival at new premises with regular health monitoring. In case of suspicion, movements should be forbidden and EHV-1 infection early detected/confirmed by validated diagnostic tools. During outbreaks, no movements should be allowed until 21 days after the detection of the last case. In general, vaccination against EHV-1 should be promoted, although this offers limited protection against the neurological form of the disease.

Assessment of listing and categorisation of animal diseases within the framework of the Animal Health Law (Regulation (EU) No 2016/429): infection with Equine Herpesvirus-1.

Equine Herpesvirus-1 infection has been assessed according to the criteria of the Animal Health Law (AHL), in particular criteria of: Article 7 on disease profile and impacts, Article 5 on the eligibility of the disease to be listed, Article 9 for the categorisation of the disease according to disease prevention and control measures as in Annex IV and Article 8 on the list of animal species related to Equine Herpesvirus-1 infection. The assessment has been performed following a methodology composed of information collection and compilation, and expert judgement on each criterion at individual and collective level. The outcome is the median of the probability ranges provided by the experts, which indicates whether the criterion is fulfilled (66-100%) or not (0-33%), or whether there is uncertainty about fulfilment (33-66%). For the questions where no consensus was reached, the different supporting views are reported. According to the assessment performed, Equine Herpesvirus-1 infection can be considered eligible to be listed for Union intervention according to Article 5 of the Animal Health Law with 33-90% certainty. According to the criteria as in Annex IV of the AHL related to Article 9 of the AHL for the categorisation of diseases according to the level of prevention and control, it was assessed with less than 1% certainty that EHV-1 fulfils the criteria as in Section 1 (category A), 1-5% for the criteria as in Section 2 (category B), 10-66% for the criteria as in Section 3 (category C), 66-90% for the criteria as in Section 4 (category D) and 33-90% for the criteria as in Section 5 (category E). The animal species to be listed for EHV-1 infection according to Article 8(3) criteria are the species belonging to the families of Equidae, Bovidae, Camelidae, Caviidae, Cervidae, Cricetidae, Felidae, Giraffidae, Leporidae, Muridae, Rhinocerontidae, Tapiridae and Ursidae.

West Nile and Usutu viruses co-circulation in central Italy: outcomes of the 2018 integrated surveillance.

BACKGROUND: West Nile (WNV) and Usutu (USUV) are emerging vector-borne zoonotic flaviviruses. They are antigenically very similar, sharing the same life cycle with birds as amplification host, Culicidae as vector, and man/horse as dead-end host. They can co-circulate in an overlapping geographic range. In Europe, surveillance plans annually detect several outbreaks. METHODS: In Italy, a WNV/USUV surveillance plan is in place through passive and active surveillance. After a 2018 WNV outbreak, a reinforced integrated risk-based surveillance was performed in four municipalities through clinical and serological surveillance in horses, Culicidae catches, and testing on human blood-based products for transfusion. RESULTS: Eight WNV cases in eight equine holdings were detected. Twenty-three mosquitoe catches were performed and 2367 specimens of Culex pipiens caught; 17 pools were USUV positive. A total of 8889 human blood donations were tested, and two asymptomatic donors were USUV positive. CONCLUSIONS: Different surveillance components simultaneously detected WNV only in horses and USUV only in humans and mosquitoes. While in endemic areas (i.e. northern Italy) entomological surveillance is successfully used as an early detection warning, this method in central Italy seems ineffective. To achieve a high level of sensitivity, the entomological trapping effort should probably exceed a reasonable balance between cost and performance. Besides, WNV/USUV early detection can be addressed by horses and birds. Further research is needed to adapt the surveillance components in different epidemiological contexts.

Seroprevalence and risk factors associated with exposure to Leishmania infantum in dogs, in an endemic Mediterranean region.

Canine leishmaniasis (CanL) is a zoonotic parasitic disease caused by Leishmania infantum in the Mediterranean area and transmitted by phlebotomine sand fly vectors. The domestic dog is the main reservoir host. The aim of this study was to assess the influence of different individual, environmental and spatial risk factors on the dog exposure to L. infantum and to estimate the seroprevalence among owned and kennel dogs, in the Lazio region (central Italy), where canine leishmaniasis is endemic. In the period 2010-2014, 13,292 sera from kennel and owned dogs were collected by official and private veterinarians. The presence of anti-Leishmania IgG was analysed by indirect fluorescent antibody test (IFAT), using a 1:80 titre cut-off. At the univariable analysis, CanL seropositivity was associated with sex, size, breed, coat length, living with other dogs and forest/semi-natural land cover. At the multivariable analysis, age, ownership and attitude were confirmed as risk factors, being more than 2 years old, owned, and hunting dogs at higher risk. Being a Maremma sheepdog was a protective factor. A true overall seroprevalence of 6.7% (95% CI: 6.2-7.2) was estimated in the whole population while 7.3% (95% CI: 6.8-7.8) was estimated in kennel dogs and 74.3% (95% CI: 70.8-77.6) in owned dogs. The role of kennels as a key component for CanL active and passive surveillance was also highlighted. This study confirmed the endemicity of CanL in the Lazio region and focused some factors that can influence the seropositivity of dogs in a Mediterranean region.

Size, demography, ownership profiles, and identification rate of the owned dog population in central Italy.

The One Health paradigm recognizes that information on infectious diseases, zoonosis and related predictors in animal populations is essential. Pets live in close contact with humans and interact with wild animals, but the lack of reliable information on pet population size, demography and ownership profiles is a constant worldwide. Reliable data must be made available in order to address proper public health policies regarding the design of surveillance plans, the management of canine welfare and stray dog phenomenon, the control of dog behaviour-related problems, and the livestock/wildlife endangerment. Dog identification & registration (I&R) have become mandatory in most European countries in recent years, but the process is far from being widely accomplished, thus resulting in an underestimation of the real canine population. To date, data on the completeness of Dog Registries is very limited. A cross-sectional survey through 630 face-to-face questionnaires was performed with the aim of investigating the dog population size, demography, ownership profiles, and the I&R rate in central Italy. Logistic regression models investigated risk factors with the following outcome variables: dog presence into the Dog Registry, veterinary care frequency, and dog ownership. The present study identified that the dog population is higher than previously reported in Italy and in Europe, whilst lower compared to countries with a poor Human Development Index (a statistic composite index of life expectancy, education, and per capita income indicators used by United Nation). Almost half of the interviewed people (47%) owned at least one dog, totalling 315 dogs. The mean number of dogs per household was 0.7 and 1.5 per dog-owning household. The Bayesian model estimated 481,294 (95% CI: 470,860-491,978) dogs (90 dogs/km2; human:dog ratio 9.0, 95% CI: 8.8-9.2) suggesting that a high density of people does not limit the dog ownership. Dogs resulted predominant among pets. The majority of dogs were males, crossbred, acquires as a gift, lived in rural areas, outdoors and attended a veterinary visit 1-2 times per year. The percentage of neutered dogs were higher in females (55%) than in males (8%). Only 75.3% (95% CI: 73.6-76.9) of the dogs were correctly identified and registered. The Dog Registry completeness increased during the first decades after its establishment, but no improvement has been made afterwards. The dogs correctly identified and registered were more likely to be purebred, neutered, lived in urban areas and visited a veterinarian frequently. Several strategies are recommended to encourage I&R, including promoting responsible dog ownership, engaging private veterinarians and dog breeders, and establishing an effective control system. The present study identified also that the dog source and the kind of feeding were variables associated with the veterinary care frequency. Owning a dog was associated with living in rural areas and the presence of children. The present study reported the poor presence of reliable predictors for the dog ownership. This is the first study to provide an estimate of the canine population abundance, characteristics, and ownership profiles in a European large metropolitan area.

Prevalence estimation of Italian ovine cystic echinococcosis in slaughterhouses: A retrospective Bayesian data analysis, 2010-2015.

Cystic echinococcosis (CE) is a complex zoonosis with domestic and sylvatic life-cycles, involving different intermediate and definitive host species. Many previous studies have highlighted the lack of a surveillance system for CE, its persistence in Italy, and endemicity in several Italian regions. Because of the absence of a uniform surveillance program for both humans and animals, disease occurrence is widely underestimated. This study aimed to estimate the prevalence of ovine CE in Italy. Survey data on the prevalence of Echinococcus granulosus complex infections in Italian sheep farms from 2010 to 2015 were obtained in collaboration with Regional Veterinary Epidemiology Observatories (OEVRs). Bayesian analysis was performed to estimate the true CE farm prevalence. The prior true CE prevalence was estimated using data from Sardinia. Second, Bayesian modelling of the observed prevalence in different regions and the true prevalence estimation from the first step were used to ultimately estimate the prevalence of ovine CE in Italy. We obtained survey data from 10 OEVRs, covering 14 Italian regions. We observed that the risk of CE infection decreased over the years, and it was strictly correlated with the density of susceptible species. Using Sardinia as prior distribution, where the disease farm prevalence was approximately 19% (95% CI, 18.82-20.02), we estimated that the highest endemic CE farm prevalence was in Basilicata with a value of 12% (95% BCI: 7.49-18.9%) and in Piemonte 7.64%(95% BCI: 4.12-13.04%). Our results provide spatially relevant data crucial for guiding CE control in Italy. Precise information on disease occurrence location would aid in the identification of priority areas for disease control implementation by the authorities. The current underestimation of CE occurrence should urge the Italian and European governments to become aware of the public health importance of CE and implement targeted interventions for high-risk areas.

A cross-sectional serosurvey in a sheep population in central Italy following a bluetongue epidemic.

Bluetongue (BT) is a viral disease that affects ruminants and is transmitted by midges of the genus Culicoides spp. The seroprevalence, the clinical form and the occurrence rates significantly differ in relation to several factors such as bluetongue virus (BTV) serotype, host species, breed susceptibility, specific previous exposure, vector ecology, husbandry and health status. Following the 2001-2006 BTV2 and BTV16 epidemics in central Italy, a new epidemic caused by BTV1 occurred in 2013-2015 causing 398 outbreaks in a susceptible population of about 1 million ruminants. The present study assessed the BTV1 seroprevalence in the sheep population of central Italy by conducting two cross-sectional surveys, in the proximity of and within BT outbreak farms. A total of 2,984 sheep from 437 farms were sampled. The animal-level prevalence was 19% (95% CI: 17-21%), the between-herd prevalence was 46% (95% CI: 41-51%) and the within-herd prevalence was 21% (95% CI: 16-26%). Risk factors were investigated by logistic regression models. Living on a farm where an outbreak occurred and the number of outbreaks in proximity of the farm were identified as risk factors, while herd size was identified as a protective factor. This study represents the first BT survey in southern Europe and reports valuable findings on BTV epidemiology. Despite intensive virus circulation, the estimated seroprevalences were low. The assessment of the population immunity level is crucial for defining an efficient vaccination strategy and for predicting the impact of future virus circulation. In view of the low seroprevalence detected albeit an extensive BTV1 circulation, the population immunity was likely to be inadequate in preventing new BTV1 epidemics. Moreover, considering the recurrent introduction of new serotypes from North Africa and the Balkans, the control of multi-serotype BTV infections will continue to present a challenge in the near future.

Endoparasites in household and shelter dogs from Central Italy.

Intestinal and respiratory parasites are among the most common pathogens in dogs and some of them are recognized as zoonotic agents. In Italy, various taxa have been reported, with variable prevalence estimates depending on study area, dog category and coprological exam technique. In this paper, we report the results of six years of passive surveillance. In the period January 2006-December 2012, 2,775 dog faecal samples from Lazio Region (Central Italy), were examined for parasites, 1,156 from household and 1,619 from shelter dogs, respectively. The following parasites were detected: Giardia duodenalis, Cystoisospora sp., Ancylostomatidae, Toxocara canis, Toxascaris leonina, Trichuris vulpis, Eucoleus böhmi, Eucoleus aerophilus, Mesocestoides sp., Taeniidae and Dipylidium caninum. Helminths were more frequent than protozoa, with total prevalences of 29.1% and 10.7%, respectively. T. vulpis and Ancylostomatidae were the most common parasites, with prevalences of 9.9% and 9.6% respectively. T. vulpis and Ancylostomatidae were significantly more prevalent in shelter dogs than in household ones. T. canis and Cystoisospora sp. were significantly more frequent in household dogs. The assessment of the prevalence in sheltered and in household dogs is useful to infer the occurrence of different parasites in the origin population and to plan possible control intervention.

Parasites in stray dogs from Italy: prevalence, risk factors and management concerns.

Parasites are among the most common pathogens recorded in dogs. High prevalence rates are usually reported in stray and shelter dogs, as these animals are less likely to be tested and treated. In this study a survey was carried out on intestinal and lung parasites of stray dogs at the moment of the admission in a shelter in Central Italy. In the period June 2014-June 2015, 262 individual faecal samples were examined. Twelve parasitic taxa were detected. Helminths were more prevalent than protozoa (61.8% and 25.6%, respectively). Ancylostomatidae showed the higher prevalence (40.5%), followed by Giardia duodenalis (21.4%), Toxocara canis (20.6%) and Trichuris vulpis (17.6%). Angiostrongylus vasorum was the most prevalent lungworm (12.6%), Crenosoma vulpis being recorded just in one dog. G. duodenalis had a high prevalence, probably because of the diagnostic techniques adopted, actually the most sensitive available for its detection. Nevertheless, the zoonotic potential of this parasite in dogs appears reduced, as all the isolates were identified as C (24.0%) and D (76.0%) dog specific assemblages. Taeniidae constituted a high potential zoonotic risk, as from the eggs it is impossible to exclude they were Echinococcus granulosus, the most relevant zoonotic parasite in Europe. The present study underline the importance of stray dogs control, aimed at preventing or minimizing parasitic spread and zoonotic transmission.

Erratum to: Parasites in stray dogs from Italy: prevalence, risk factors and management concerns.

The original version of the table of contents unfortunately contained a mistake. The published entry: De Liberato Claudio, Berrilli Federica, Odorizi Livio, Scarcella Roberto, Barni Marco, Amoruso Cristina, Scarito Alessia, Di Filippo Margherita Montalbano, Carvelli Andrea, Iacoponi Francesca and Scaramozzino Paola - Parasites in stray dogs from Italy: prevalence, risk factors and management concernsshould be corrected as follows:De Liberato Claudio, Berrilli Federica, Odorizi Livio, Scarcella Roberto, Barni Marco, Amoruso Cristina, Scarito Alessia, Montalbano Di Filippo Margherita, Carvelli Andrea, Iacoponi Francesca and Scaramozzino Paola - Parasites in stray dogs from Italy: prevalence, risk factors and management concerns.

A Cross-Sectional Survey to Estimate the Cat Population and Ownership Profiles in a Semirural Area of Central Italy.

Understanding animal population size and its demographic features is essential to address Public Health policies as well as to provide valuable information to pet industries and veterinary practitioners. Nevertheless, official data on feline population are not available worldwide. In the present study, the owned cat population size, its demographic attributes, and the ownership profiles have been investigated through a face-to-face questionnaire in a semirural area of Central Italy. The human : cat ratio was equal to 6.8 (95% CI: 5.7-7.5); 29.3% of households own at least one cat. The majority of cats were living in a rural area (67.8%) and outdoors, were neutered (70.5%), and were fed with commercial food (54.8%) and they visited a veterinarian 1-2 times a year (43.3%). The cat ownership was strongly associated with people living in a rural area and owning another pet. As the cat owned population was mainly kept outdoors in rural areas, the possible relation between the owned and the stray animals is worthy to be monitored in future researches. Our study revealed that the feline owned population was larger than expected and that social and economic human factors do not influence the cat ownership. Health Authorities and veterinary practitioners should promote responsible ownership to increase the veterinary care, to intensify the official identification, and to properly manage the outdoor lifestyle.

First cases of Schmallenberg virus in Italy: surveillance strategies.

Following the first report of Schmallenberg virus (SBV) in the brain of a dystocic goat foetus in 2012 in Northern Italy, immediate response actions were adopted to avoid the virus circulation. The brain tested positive by 2 different one-step real-time RT-PCR protocols; these results were also confirmed by partial sequencing of the viral genome. At that time this was the first detection of the new Orthobunyavirus genus within the Bunyaviridae family in Italy. An epidemiological investigation in the involved farm was carried out in collaboration with the CESME - National Reference Centre for the study and verification of Foreign Animal Diseases (Istituto Zooprofilattico Sperimentale dell'Abruzzo e del Molise 'G. Caporale', Italy). Epidemiological information on the flock was provided and analysed, whole blood and serum samples were also collected from all animals in the farm for both virological and serological investigations. All blood samples tested negative for SBV, whereas serological positive results were obtained by virus-neutralization (VN). Epidemiological investigations indicated the possible virus circulation in the area. The subsequent surveillance actions were mainly based on the standardization and reenforcement of passive surveillance protocols, a risk-based serological surveillance programme through VN and an entomological surveillance programme in the involved geographical areas were also put in place. Eventually SBV local circulation was confirmed by real time RT-PCR in 6 Culicoides pools, collected between September and November 2011 in 3 farms in the surroundings of the area of SBV outbreak.

Bluetongue virus serotypes 1 and 4 in Sardinia during autumn 2012: new incursions or re-infection with old strains?

Since 2000 several bluetongue virus (BTV) incursions have occurred in Sardinia (Italy) involving serotypes 1, 2, 4, 8 and 16. In October 2012, new BT outbreaks caused by BTV-1 and BTV-4 were reported. Nearly 500 flocks were infected and 9238 sheep died because of the infection. When sequenced, Seg-10 of both strains shared 99% similarity at nucleotide level with BTV strains that have circulated in the Mediterranean basin in the last few years. Similarly, Seg-5 sequences of BTV-1 and BTV-4 newly isolated Sardinian strains are identical and cluster together with recent BTV-1 circulating in the Mediterranean Basin and the BTV-4 strains isolated in Tunisia in 2007 and 2009. These BTV-4 strains differ from the ones that circulated in Europe from 2003 to 2005 and appear to be reassortant strains.