Pojavnost influence u životinja u Hrvatskoj: kratak pregled povodom 100 godina od pojave pandemije 1918.

Influenza is an important respiratory disease of human beings and different animal species caused by influenza viruses belonging to the family Orthomyxoviridae, which comprises four genera (Influenzavirus A, B, C and D). In an introductory overview a brief historical review of the main pandemics of influenza A in humans worldwide is given. Spanish, Asian, Hong Kong, Russian influenza and North American swine influenza, as well as infections caused by the recently occurring influenza D virus, are briefly described. Aquatic birds are the natural reservoirs of influenza A viruses worldwide, and harbour viruses with all possible combinations of 16 haemagglutinin (HA) and 9 neuraminidase (NA) subtypes. The crossing of the species barrier by avian influenza viruses is presented. A previous review on the zoonotic nature of influenza viruses was published in Croatia in 1982. Outbreaks of equine, swine and avian influenza have been described in Croatia. HI antibodies to A/swine/Texas/4199/1998 (H3N2) were detected in dog sera. Epizootics of equine influenza caused by H7N7 and H3N8 subtypes have been known in Croatia for 80 years. Recent outbreaks showed an antigenic drift of the viruses involved. American lineage H3N8 was detected. The last serological evidence worldwide of A/equine H7N7 was reported from Croatia. New outbreaks of H3N8 were likely the result of vaccine failure. Serological examination of domestic pigs has revealed the prevalence of the H1N1 and H3N2 subtypes. Tested feral pigs were serologically positive to H1N1 and H3N2 subtypes. Recent clinical outbreaks of swine influenza caused by the H1N1 subtype were documented by immunohistochemistry, nucleic acid detection and virus isolation. Avian influenza had no impact on poultry production in Croatia until late 2005 when a highly pathogenic zoonotic avian influenza (HPAI) virus of the H5N1 subtype was detected in wild birds in eastern Croatia. The multiple introduction of the Asian HPAI H5N1 virus into Croatia by wild birds was documented. From October 2016 until March 2017, 19 outbreaks of HPAI H5N8 were detected in Croatia, 16 in wild birds and three in poultry. The new H5N5 reassortant virus was introduced from Asia. Avian influenza virus of H16 subtype was isolated from black-headed gulls.Influenca je zarazna bolest ljudi i različitih životinjskih vrsta prouzročena virusima influence porodice Orthomyxoviridae, koji su svrstani u 4 roda: Influenzavirus A, B, C i D. Uvodno je iznesen kratak povijesni prikaz najvažnijih pandemija influence A u ljudi u 20. stoljeću: španjolske, azijske, hongkongške, ruske i sjeverno-američke (svinjske) gripe te infekcije prouzročene novim influenca D virusom. Vodene ptice prirodni su rezervoar virusa influence A diljem svijeta. U njih su dokazane sve antigenske kombinacije od mogućih 16 podtipova hemaglutinina i 9 podtipova neuraminidaze. Opisan je međuvrsni prijenos ptičjih virusa influence o čemu se u nas može naći podosta rasprava u znanstvenoj i stručnoj literaturi. U Hrvatskoj su u prošlosti opisane epizootije influence konja, svinja i ptica, a protutijela inhibicije hemaglutinacije za A/swine/Texas/4199/1998 (H3N2) dokazana su u serumu pasa. Nakon prvog opisa prije 80 godina, česta su izvješća o pojavi epizootija influence konja prouzročene podtipovima H7N7 i H3N8. U novijim epizootijama dokazano je antigensko skretanje uzročnika s naglaskom da izdvojeni podtip H3N8 pripada američkoj liniji. Već duže vrijeme nema dokaza o aktivnosti podtipa H7N7 u svijetu. Nalaz specifičnih protutijela za taj podtip posljednji put je dokazan upravo u Hrvatskoj. Smatra se da se pojava novih epizootija influence konja uzrokovanih podtipom H3N8 može pripisati neodgovarajućem antigenskom sastavu rabljenih cjepiva. Na osnovi seroloških istraživanja influence u domaćih svinja pokazalo se da u njihovoj populaciji kolaju podtipovi H1N1 i H3N2. Serološki je utvrđeno da ti podtipovi kolaju i u populaciji divljih svinja u Hrvatskoj. U najnovije doba opisana je klinička slika influence svinja uzrokovane podtipom H1N1 u nekim mnoštvenim uzgojima u Hrvatskoj. Osebujan klinički nalaz potkrijepljen je pozitivnim nalazom pretragom RT-PCR-om, pozitivnim imunohistokemijskim nalazom u tkivu plućiju zahvaćenih svinja te izdvajanjem virusa na staničnoj kulturi MDCK. Influenca ptica nije imala nekog utjecaja na peradarsku proizvodnju u Hrvatskoj sve do 2005. godine, kada je zoonotski visoko patogeni virus ptičje gripe podtip H5N1 bio utvrđen u divljih ptica na području Istočne Hrvatske. Nakon toga ustanovljena je višestruka pojava azijskog visokopatogenog podtipa H5N1 u divljih ptica u Hrvatskoj. Od listopada 2016. do ožujka 2017. godine zabilježeno je 19 pojava visokopatogenog podtipa H5N8, od čega 16 u divljih ptica, a tri u domaće peradi. Nova presloženica H5N5 u Hrvatsku je bila prenesena iz Azije. U riječnog galeba u okolici Zagreba dokazan je podtip H16

Molecular epidemiology of equine influenza virus subtype H3N8 in Croatia (1968-2021)

Equine influenza (EI) is one of the most important viral diseases of horses. The first equine influenza virus (EIV) subtype H7N7 was isolated in 1956. It was circulating worldwide until its disappear- ance in the 1980s. In contrast, EIV subtype H3N8, described in 1963, is still circulating in the horse population. Outbreaks of EI have been reported in Croatia since the 60s of the previous century. The first EIV subtype H3N8 was isolated in Croatia in 1968. Since then, the same subtype caused three EI outbreaks in Croatia in 1988, 2004 and 2015, respectively. In July 2021, outbreaks of acute respiratory infection were reported in two stud farms in continental Croatia, with differences in severity of clinical signs and epidemic size. EIV subtype H3N8 was confirmed as a causative agent. Molecular charac- terization and phylogenetic analysis showed that the virus is a member of Florida sublineage clade 1. It was the first evidence of the Florida sublineage clade 1 EIV circulation in our country because the last two outbreaks, 2004 and 2015, were caused by Florida sublineage clade 2. This study investigated the molecular epidemiology of EIV subtype H3N8 isolated in Croatia from 1968 to 2021. Results confirmed that EIVs subtype H3N8 isolated in Croatia are closely related to other European strains isolated at the time of outbreaks in other European countries. Croatian isolates’ evolution follows global EIV subtype H3N8 evolution, which indicates the sporadical introduction of the EIV in Croa- tia. In conclusion, molecular epidemiology of EIV subtype H3N8 in Croatia highlights the necessity of immunoprophylaxis with vaccines containing recent strains to protect the horse population

Molecular epidemiology of equine influenza virus subtype H3N8 in Croatia (1968-2021)

Equine influenza (EI) is one of the most important viral diseases of horses. The first equine influenza virus (EIV) subtype H7N7 was isolated in 1956. It was circulating worldwide until its disappear- ance in the 1980s. In contrast, EIV subtype H3N8, described in 1963, is still circulating in the horse population. Outbreaks of EI have been reported in Croatia since the 60s of the previous century. The first EIV subtype H3N8 was isolated in Croatia in 1968. Since then, the same subtype caused three EI outbreaks in Croatia in 1988, 2004 and 2015, respectively. In July 2021, outbreaks of acute respiratory infection were reported in two stud farms in continental Croatia, with differences in severity of clinical signs and epidemic size. EIV subtype H3N8 was confirmed as a causative agent. Molecular charac- terization and phylogenetic analysis showed that the virus is a member of Florida sublineage clade 1. It was the first evidence of the Florida sublineage clade 1 EIV circulation in our country because the last two outbreaks, 2004 and 2015, were caused by Florida sublineage clade 2. This study investigated the molecular epidemiology of EIV subtype H3N8 isolated in Croatia from 1968 to 2021. Results confirmed that EIVs subtype H3N8 isolated in Croatia are closely related to other European strains isolated at the time of outbreaks in other European countries. Croatian isolates’ evolution follows global EIV subtype H3N8 evolution, which indicates the sporadical introduction of the EIV in Croa- tia. In conclusion, molecular epidemiology of EIV subtype H3N8 in Croatia highlights the necessity of immunoprophylaxis with vaccines containing recent strains to protect the horse population