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The Nature of Exposure Drives Transmission of Nipah Viruses from Malaysia and Bangladesh in Ferrets.

Clayton BA, Middleton D, Arkinstall R, Frazer L, Wang LF, Marsh GA - PLoS Negl Trop Dis (2016)

Bottom Line: In contrast, all naïve ferrets developed acute infection following assisted and direct exposure to oronasal fluid from animals that were shedding either NiV-BD or NiV-MY.In contrast, active transfer of infected bodily fluids consistently results in transmission, regardless of the virus strain.These observations suggest that the risk of NiV transmission is underpinned by social and environmental factors, and will have practical implications for managing transmission risk during outbreaks of human disease.

View Article: PubMed Central - PubMed

Affiliation: Health and Biosecurity, Australian Animal Health Laboratory, Commonwealth Scientific and Industrial Research Organisation, Geelong, Victoria, Australia.

ABSTRACT
Person-to-person transmission is a key feature of human Nipah virus outbreaks in Bangladesh. In contrast, in an outbreak of Nipah virus in Malaysia, people acquired infections from pigs. It is not known whether this important epidemiological difference is driven primarily by differences between NiV Bangladesh (NiV-BD) and Malaysia (NiV-MY) at a virus level, or by environmental or host factors. In a time course study, ferrets were oronasally exposed to equivalent doses of NiV-BD or NiV-MY. More rapid onset of productive infection and higher levels of virus replication in respiratory tract tissues were seen for NiV-BD compared to NiV-MY, corroborating our previous report of increased oral shedding of NiV-BD in ferrets and suggesting a contributory mechanism for increased NiV-BD transmission between people compared to NiV-MY. However, we recognize that transmission occurs within a social and environmental framework that may have an important and differentiating role in NiV transmission rates. With this in mind, ferret-to-ferret transmission of NiV-BD and NiV-MY was assessed under differing viral exposure conditions. Transmission was not identified for either virus when naïve ferrets were cohoused with experimentally-infected animals. In contrast, all naïve ferrets developed acute infection following assisted and direct exposure to oronasal fluid from animals that were shedding either NiV-BD or NiV-MY. Our findings for ferrets indicate that, although NiV-BD may be shed at higher levels than NiV-MY, transmission risk may be equivalently low under exposure conditions provided by cohabitation alone. In contrast, active transfer of infected bodily fluids consistently results in transmission, regardless of the virus strain. These observations suggest that the risk of NiV transmission is underpinned by social and environmental factors, and will have practical implications for managing transmission risk during outbreaks of human disease.

No MeSH data available.


Related in: MedlinePlus

Transmission study–cohabitation plus direct transfer of secretions: Infection outcomes.Animals are presented by cage groupings for the NiV-BD (A) and NiV-MY (B) infection groups. Donors were each housed with two recipients (arrows). Recipients received their first direct exposure dose at 6 days following infection of donors and a second dose at the time of euthanasia of donor ferrets; the infectious dose (total 50% tissue culture infective dose) for each exposure event is given with the day post infection (dpi) on which the donor was sampled, and, in parentheses, the corresponding day post commencement (dpc) of cohousing of recipients. Viral shedding by recipients was assessed over the course of the study; + denotes a positive sample. Dpi, days post-donor infection; NW, nasal wash; OS, oral swab; RS, rectal swab; #, sample positive by RT-PCR but virus isolation not attempted.
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pntd.0004775.g006: Transmission study–cohabitation plus direct transfer of secretions: Infection outcomes.Animals are presented by cage groupings for the NiV-BD (A) and NiV-MY (B) infection groups. Donors were each housed with two recipients (arrows). Recipients received their first direct exposure dose at 6 days following infection of donors and a second dose at the time of euthanasia of donor ferrets; the infectious dose (total 50% tissue culture infective dose) for each exposure event is given with the day post infection (dpi) on which the donor was sampled, and, in parentheses, the corresponding day post commencement (dpc) of cohousing of recipients. Viral shedding by recipients was assessed over the course of the study; + denotes a positive sample. Dpi, days post-donor infection; NW, nasal wash; OS, oral swab; RS, rectal swab; #, sample positive by RT-PCR but virus isolation not attempted.

Mentions: One donor ferret in the NiV-BD group was febrile when recipient animals were introduced at d6pi; the other three donors (one NiV-BD and both NiV-MY donors) were not. The two virus exposure doses for each recipient pair are presented in Fig 6; titres were comparable for the virus strains and, as expected, viral titre in secretions collected at the time of donor euthanasia were equivalent to or higher than those from samples earlier in the donor infection course.


The Nature of Exposure Drives Transmission of Nipah Viruses from Malaysia and Bangladesh in Ferrets.

Clayton BA, Middleton D, Arkinstall R, Frazer L, Wang LF, Marsh GA - PLoS Negl Trop Dis (2016)

Transmission study–cohabitation plus direct transfer of secretions: Infection outcomes.Animals are presented by cage groupings for the NiV-BD (A) and NiV-MY (B) infection groups. Donors were each housed with two recipients (arrows). Recipients received their first direct exposure dose at 6 days following infection of donors and a second dose at the time of euthanasia of donor ferrets; the infectious dose (total 50% tissue culture infective dose) for each exposure event is given with the day post infection (dpi) on which the donor was sampled, and, in parentheses, the corresponding day post commencement (dpc) of cohousing of recipients. Viral shedding by recipients was assessed over the course of the study; + denotes a positive sample. Dpi, days post-donor infection; NW, nasal wash; OS, oral swab; RS, rectal swab; #, sample positive by RT-PCR but virus isolation not attempted.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4920392&req=5

pntd.0004775.g006: Transmission study–cohabitation plus direct transfer of secretions: Infection outcomes.Animals are presented by cage groupings for the NiV-BD (A) and NiV-MY (B) infection groups. Donors were each housed with two recipients (arrows). Recipients received their first direct exposure dose at 6 days following infection of donors and a second dose at the time of euthanasia of donor ferrets; the infectious dose (total 50% tissue culture infective dose) for each exposure event is given with the day post infection (dpi) on which the donor was sampled, and, in parentheses, the corresponding day post commencement (dpc) of cohousing of recipients. Viral shedding by recipients was assessed over the course of the study; + denotes a positive sample. Dpi, days post-donor infection; NW, nasal wash; OS, oral swab; RS, rectal swab; #, sample positive by RT-PCR but virus isolation not attempted.
Mentions: One donor ferret in the NiV-BD group was febrile when recipient animals were introduced at d6pi; the other three donors (one NiV-BD and both NiV-MY donors) were not. The two virus exposure doses for each recipient pair are presented in Fig 6; titres were comparable for the virus strains and, as expected, viral titre in secretions collected at the time of donor euthanasia were equivalent to or higher than those from samples earlier in the donor infection course.

Bottom Line: In contrast, all naïve ferrets developed acute infection following assisted and direct exposure to oronasal fluid from animals that were shedding either NiV-BD or NiV-MY.In contrast, active transfer of infected bodily fluids consistently results in transmission, regardless of the virus strain.These observations suggest that the risk of NiV transmission is underpinned by social and environmental factors, and will have practical implications for managing transmission risk during outbreaks of human disease.

View Article: PubMed Central - PubMed

Affiliation: Health and Biosecurity, Australian Animal Health Laboratory, Commonwealth Scientific and Industrial Research Organisation, Geelong, Victoria, Australia.

ABSTRACT
Person-to-person transmission is a key feature of human Nipah virus outbreaks in Bangladesh. In contrast, in an outbreak of Nipah virus in Malaysia, people acquired infections from pigs. It is not known whether this important epidemiological difference is driven primarily by differences between NiV Bangladesh (NiV-BD) and Malaysia (NiV-MY) at a virus level, or by environmental or host factors. In a time course study, ferrets were oronasally exposed to equivalent doses of NiV-BD or NiV-MY. More rapid onset of productive infection and higher levels of virus replication in respiratory tract tissues were seen for NiV-BD compared to NiV-MY, corroborating our previous report of increased oral shedding of NiV-BD in ferrets and suggesting a contributory mechanism for increased NiV-BD transmission between people compared to NiV-MY. However, we recognize that transmission occurs within a social and environmental framework that may have an important and differentiating role in NiV transmission rates. With this in mind, ferret-to-ferret transmission of NiV-BD and NiV-MY was assessed under differing viral exposure conditions. Transmission was not identified for either virus when naïve ferrets were cohoused with experimentally-infected animals. In contrast, all naïve ferrets developed acute infection following assisted and direct exposure to oronasal fluid from animals that were shedding either NiV-BD or NiV-MY. Our findings for ferrets indicate that, although NiV-BD may be shed at higher levels than NiV-MY, transmission risk may be equivalently low under exposure conditions provided by cohabitation alone. In contrast, active transfer of infected bodily fluids consistently results in transmission, regardless of the virus strain. These observations suggest that the risk of NiV transmission is underpinned by social and environmental factors, and will have practical implications for managing transmission risk during outbreaks of human disease.

No MeSH data available.


Related in: MedlinePlus