Influenza A in Swedish harbour seals (Phoca vitulina)
Evidence of infection with influenza A has been documented in several different marine mammals. However, large outbreaks with mass mortalities have only been seen in harbour seals. In 2014, the first outbreak with influenza A virus (IAV) in harbour seals in Europe was reported. The outbreak start...
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| Format: | Second cycle, A2E |
| Language: | Swedish Inglés |
| Published: |
2022
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| Online Access: | https://stud.epsilon.slu.se/17548/ |
| _version_ | 1855572914938576896 |
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| author | Johnsson, Johanna |
| author_browse | Johnsson, Johanna |
| author_facet | Johnsson, Johanna |
| author_sort | Johnsson, Johanna |
| collection | Epsilon Archive for Student Projects |
| description | Evidence of infection with influenza A has been documented in several different marine mammals.
However, large outbreaks with mass mortalities have only been seen in harbour seals. In 2014, the
first outbreak with influenza A virus (IAV) in harbour seals in Europe was reported. The outbreak
started in coastal waters off the Swedish west coast and spread to Denmark, Germany, and the
Netherlands. More than 2 000 harbour seals died during the event.
The aim of this study was to do a follow-up on the outbreak with IAV in Swedish harbour seals
in 2014. The overall purpose was to increase the knowledge about IAV infections in the Swedish
harbour seal populations. More specific objectives included mapping circulation of specific subtypes
and evaluating cadaver blood as a sample material instead of pure serum for IAV antibody detection
and subtyping.
Serum samples were acquired from live-captured seals in 2014, and cadaver blood samples from
hunted or found dead seals from 2014-2021. All samples were screened for anti-nucleoprotein
antibodies using a commercial competitive ELISA. Positive and doubtful samples were confirmed
and subtyped by hemagglutination inhibition assay (HI). In addition, information from sampled seals
was gathered to draw relevant conclusions from test results.
The results show a high level of antibodies against IAV H10N7 in a large proportion of serum
samples from 2014, with declining levels of antibodies against IAV in a lower proportion of cadaver
blood samples from the west coast in 2015 and 2016. IAV antibodies were not found in samples
from the Kalmarsund population or in the population off the west coast after 2016. Half of the ELISA
positive or doubtful cadaver blood samples could be confirmed and subtyped by HI. Data from
sampled seals made it possible to connect all ELISA positive samples to exposure to the outbreak
in 2014. Evidence of circulation of other IAV subtypes was not found.
This study indicates that IAVs do not circulate and persist within the Swedish harbour seal
populations, and that the populations most likely are naive in the case of a possible new spillover
event. Environmental contaminants, low genetic variation, larger populations, and smaller habitats
are identified as important risk factors for increased incidence of disease and spread of infection in
a potential new outbreak. Cadaver blood is an accessible sample which according to this study can
be useful in IAV surveillance on a population level to determine whether a population has been
exposed to the IAV or not. It can therefore be an important tool for understanding disease dynamics,
disease control and possibly prevention of pandemic influenza. |
| format | Second cycle, A2E |
| id | RepoSLU17548 |
| institution | Swedish University of Agricultural Sciences |
| language | Swedish Inglés |
| publishDate | 2022 |
| publishDateSort | 2022 |
| record_format | eprints |
| spelling | RepoSLU175482023-01-20T00:15:07Z https://stud.epsilon.slu.se/17548/ Influenza A in Swedish harbour seals (Phoca vitulina) Johnsson, Johanna Pests of plants Evidence of infection with influenza A has been documented in several different marine mammals. However, large outbreaks with mass mortalities have only been seen in harbour seals. In 2014, the first outbreak with influenza A virus (IAV) in harbour seals in Europe was reported. The outbreak started in coastal waters off the Swedish west coast and spread to Denmark, Germany, and the Netherlands. More than 2 000 harbour seals died during the event. The aim of this study was to do a follow-up on the outbreak with IAV in Swedish harbour seals in 2014. The overall purpose was to increase the knowledge about IAV infections in the Swedish harbour seal populations. More specific objectives included mapping circulation of specific subtypes and evaluating cadaver blood as a sample material instead of pure serum for IAV antibody detection and subtyping. Serum samples were acquired from live-captured seals in 2014, and cadaver blood samples from hunted or found dead seals from 2014-2021. All samples were screened for anti-nucleoprotein antibodies using a commercial competitive ELISA. Positive and doubtful samples were confirmed and subtyped by hemagglutination inhibition assay (HI). In addition, information from sampled seals was gathered to draw relevant conclusions from test results. The results show a high level of antibodies against IAV H10N7 in a large proportion of serum samples from 2014, with declining levels of antibodies against IAV in a lower proportion of cadaver blood samples from the west coast in 2015 and 2016. IAV antibodies were not found in samples from the Kalmarsund population or in the population off the west coast after 2016. Half of the ELISA positive or doubtful cadaver blood samples could be confirmed and subtyped by HI. Data from sampled seals made it possible to connect all ELISA positive samples to exposure to the outbreak in 2014. Evidence of circulation of other IAV subtypes was not found. This study indicates that IAVs do not circulate and persist within the Swedish harbour seal populations, and that the populations most likely are naive in the case of a possible new spillover event. Environmental contaminants, low genetic variation, larger populations, and smaller habitats are identified as important risk factors for increased incidence of disease and spread of infection in a potential new outbreak. Cadaver blood is an accessible sample which according to this study can be useful in IAV surveillance on a population level to determine whether a population has been exposed to the IAV or not. It can therefore be an important tool for understanding disease dynamics, disease control and possibly prevention of pandemic influenza. Hos flera olika arter av marina däggdjur har evidens för infektion med influensa A virus (IAV) dokumenterats, men stora utbrott med hög dödlighet har endast rapporterats hos knubbsälar. Det första utbrottet med IAV hos knubbsälar i Europa inträffade 2014. Utbrottet startade utanför den svenska västkusten och spred sig vidare till Danmark, Tyskland och Nederländerna. Uppskattningsvis dog fler än 2 000 sälar under utbrottet. Syftet med den här studien var att göra en uppföljning av utbrottet med IAV hos svenska knubbsälar 2014. Den övergripande målsättningen var att bidra till en ökad kunskap om IAV-infektioner hos svenska knubbsälar. Mer specifikt syftade studien till att öka kunskapen om vilka H-subtyper av IAV som svenska knubbsälar har exponerats för, samt att utvärdera användningen av kadaverblod i stället för rent serum för påvisande av IAV antikroppar hos knubbsäl. Serumprover samlades in under en hälsokontroll av knubbsälar på västkusten 2014. Kadaverblodsprover samlades in från jagade och påträffade döda knubbsälar under åren 2014–2021. Initialt gjordes en screening av samtliga prover med en multispecies ELISA som detekterar antikroppar mot virusets nukleoprotein. Positiva prover bekräftades och subtypades därefter med hemagglutinations inhibitions test (HI). Provsvar sammanställdes därefter med tillhörande metadata för att kunna dra relevanta slutsatser. Analysresultatet visade på en hög andel antikroppar mot IAV H10N7 i merparten av serumproverna från 2014, med en minskande andel antikroppar i kadaverblodsproverna från 2015 och 2016. Antikroppar hittades inte i prover från Kalmarsundspopulationen eller i prover från västkusten insamlade efter 2016. Hälften av de ELISA-positiva kadaverblodsproverna kunde bekräftas och subtypas med HI. Metadata från provtagna sälar gjorde det möjligt att relatera samtliga prover med antikroppar till exponering för utbrottet med H10N7 2014. Resultaten visade att det inte förekom andra subtyper av IAV. Studien indikerar att IAV inte cirkulerar hos svenska knubbsälar, vilket även innebär att de svenska knubbsälspopulationerna är naiva och potentiellt mottagliga om IAV skulle introduceras på nytt. Miljöföroreningar, låg genetisk variation, stora populationer och mindre habitat identifieras som riskfaktorer som kan bidra till en ökad sjukdomsförekomst och smittspridning vid ett nytt potentiellt utbrott. Kadaverblod är ett tillgängligt prov som enligt den här studien kan användas för att övervaka IAV hos knubbsälar på en populationsnivå. Kadaverblod kan därför fungera som ett viktigt verktyg för att öka förståelsen kring sjukdomsdynamik, sjukdomskontroll och för att förebygga utbrott med nya IAV. 2022-02-16 Second cycle, A2E NonPeerReviewed application/pdf sv https://stud.epsilon.slu.se/17548/1/johnsson_j_220120.pdf Johnsson, Johanna, 2022. Influenza A in Swedish harbour seals (Phoca vitulina) : a serological study. Second cycle, A2E. Uppsala: (VH) > Dept. of Biomedical Sciences and Veterinary Public Health (until 231231) <https://stud.epsilon.slu.se/view/divisions/OID-713.html> urn:nbn:se:slu:epsilon-s-17548 eng |
| spellingShingle | Pests of plants Johnsson, Johanna Influenza A in Swedish harbour seals (Phoca vitulina) |
| title | Influenza A in Swedish harbour seals (Phoca vitulina) |
| title_full | Influenza A in Swedish harbour seals (Phoca vitulina) |
| title_fullStr | Influenza A in Swedish harbour seals (Phoca vitulina) |
| title_full_unstemmed | Influenza A in Swedish harbour seals (Phoca vitulina) |
| title_short | Influenza A in Swedish harbour seals (Phoca vitulina) |
| title_sort | influenza a in swedish harbour seals (phoca vitulina) |
| topic | Pests of plants |
| url | https://stud.epsilon.slu.se/17548/ https://stud.epsilon.slu.se/17548/ |