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H5N2 Highly Pathogenic Avian Influenza Viruses from the US 2014-2015 outbreak have an unusually long pre-clinical period in turkeys

View Article: PubMed Central - PubMed

ABSTRACT

Background: From December 2014 through June 2015, the US experienced the most costly highly pathogenic avian influenza (HPAI) outbreak to date. Most cases in commercial poultry were caused by an H5N2 strain which was a reassortant with 5 Eurasian lineage genes, including a clade 2.3.4.4 goose/Guangdong/1996 lineage hemagglutinin, and 3 genes from North American wild waterfowl low pathogenicity avian influenza viruses. The outbreak primarily affected turkeys and table-egg layer type chickens. Three isolates were selected for characterization in turkeys: the US index isolate from December 2014 (A/northern pintail/WA/40964/2014), and two poultry isolates from April 2015 (A/chicken/IA/13388/2015 and A/turkey/MN/12528/2015).

Results: Four week old broad-breasted white turkeys were inoculated with one of three doses (102, 104 or 106 50% egg infectious doses [EID50] per bird) of each of the isolates to evaluate infectious dose and pathogenesis. The mean bird infectious dose of A/northern pintail/WA/40964/2014 and A/turkey/MN/12528/2015 was 105 EID50 per bird, but was 103 EID50 per bird for A/chicken/IA/13388/2015, suggesting the latter had greater adaptation to gallinaceous birds. All three isolates had unusually long mean death time of 5.3–5.9 days post challenge, and the primary clinical signs were severe lethargy and neurological signs which started no more than 24 h before death (the average pre-clinical period was 4 days). Infected turkeys also shed high levels of virus by both the oropharyngeal and cloacal routes.

Conclusions: The unusually long mean death times, high levels of virus in feces, and increased adaptation of the later viruses may have contributed to the rapid spread of the virus during the peak of the outbreak.

No MeSH data available.


Related in: MedlinePlus

Oropharyngeal (OP) and cloacal (CL) shed determined by real-time RT-PCR for each virus by time post challenge with 106 50% egg infectious doses (EID50) per bird. Data are absent from the A/northen pintail/WA/40964/2014 isolates at 12, 24, 36 h and 3 days because the samples were not collected, at 10 and 14 days because no turkeys survived to these time points. Thick bars indicate the mean of the group and error bars represent one standard deviation
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Fig1: Oropharyngeal (OP) and cloacal (CL) shed determined by real-time RT-PCR for each virus by time post challenge with 106 50% egg infectious doses (EID50) per bird. Data are absent from the A/northen pintail/WA/40964/2014 isolates at 12, 24, 36 h and 3 days because the samples were not collected, at 10 and 14 days because no turkeys survived to these time points. Thick bars indicate the mean of the group and error bars represent one standard deviation

Mentions: Oro-pharyngeal and CL shed titers for groups exposed to 106EID50/bird are shown in Fig. 1. Oro-pharyngeal shedding was detectable at all times and peaked 3–4 days PC for all three isolates with titers exceeding 106EID50/ml from birds exposed to TK/12528 and CK/13388. Although titers from birds exposed to NOPI/40964 were about one log10 lower the difference was not significant. Cloacal shedding also peaked at 3 days PC from birds exposed to TK/12528 and CK/133388, but was later for NOPI/40964 exposed birds where the highest titers were at 7 days PC. Turkeys in the 106EID50/bird dose group that survived to 10 days PC were still shedding virus. There were no differences in the numbers of turkeys shedding among the isolates for the 106EID50/bird dose group (all were 100%).Fig. 1


H5N2 Highly Pathogenic Avian Influenza Viruses from the US 2014-2015 outbreak have an unusually long pre-clinical period in turkeys
Oropharyngeal (OP) and cloacal (CL) shed determined by real-time RT-PCR for each virus by time post challenge with 106 50% egg infectious doses (EID50) per bird. Data are absent from the A/northen pintail/WA/40964/2014 isolates at 12, 24, 36 h and 3 days because the samples were not collected, at 10 and 14 days because no turkeys survived to these time points. Thick bars indicate the mean of the group and error bars represent one standard deviation
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC5120423&req=5

Fig1: Oropharyngeal (OP) and cloacal (CL) shed determined by real-time RT-PCR for each virus by time post challenge with 106 50% egg infectious doses (EID50) per bird. Data are absent from the A/northen pintail/WA/40964/2014 isolates at 12, 24, 36 h and 3 days because the samples were not collected, at 10 and 14 days because no turkeys survived to these time points. Thick bars indicate the mean of the group and error bars represent one standard deviation
Mentions: Oro-pharyngeal and CL shed titers for groups exposed to 106EID50/bird are shown in Fig. 1. Oro-pharyngeal shedding was detectable at all times and peaked 3–4 days PC for all three isolates with titers exceeding 106EID50/ml from birds exposed to TK/12528 and CK/13388. Although titers from birds exposed to NOPI/40964 were about one log10 lower the difference was not significant. Cloacal shedding also peaked at 3 days PC from birds exposed to TK/12528 and CK/133388, but was later for NOPI/40964 exposed birds where the highest titers were at 7 days PC. Turkeys in the 106EID50/bird dose group that survived to 10 days PC were still shedding virus. There were no differences in the numbers of turkeys shedding among the isolates for the 106EID50/bird dose group (all were 100%).Fig. 1

View Article: PubMed Central - PubMed

ABSTRACT

Background: From December 2014 through June 2015, the US experienced the most costly highly pathogenic avian influenza (HPAI) outbreak to date. Most cases in commercial poultry were caused by an H5N2 strain which was a reassortant with 5 Eurasian lineage genes, including a clade 2.3.4.4 goose/Guangdong/1996 lineage hemagglutinin, and 3 genes from North American wild waterfowl low pathogenicity avian influenza viruses. The outbreak primarily affected turkeys and table-egg layer type chickens. Three isolates were selected for characterization in turkeys: the US index isolate from December 2014 (A/northern pintail/WA/40964/2014), and two poultry isolates from April 2015 (A/chicken/IA/13388/2015 and A/turkey/MN/12528/2015).

Results: Four week old broad-breasted white turkeys were inoculated with one of three doses (102, 104 or 106 50% egg infectious doses [EID50] per bird) of each of the isolates to evaluate infectious dose and pathogenesis. The mean bird infectious dose of A/northern pintail/WA/40964/2014 and A/turkey/MN/12528/2015 was 105 EID50 per bird, but was 103 EID50 per bird for A/chicken/IA/13388/2015, suggesting the latter had greater adaptation to gallinaceous birds. All three isolates had unusually long mean death time of 5.3–5.9 days post challenge, and the primary clinical signs were severe lethargy and neurological signs which started no more than 24 h before death (the average pre-clinical period was 4 days). Infected turkeys also shed high levels of virus by both the oropharyngeal and cloacal routes.

Conclusions: The unusually long mean death times, high levels of virus in feces, and increased adaptation of the later viruses may have contributed to the rapid spread of the virus during the peak of the outbreak.

No MeSH data available.


Related in: MedlinePlus