Monday, August 20, 2018

PRO/AH/EDR> Usutu virus vectors - North America

USUTU VIRUS VECTORS - NORTH AMERICA
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Date: Fri 17 Aug 2018
Source: PLoS (Public Library of Science) Neglected Tropical Diseases
[edited]
<http://journals.plos.org/plosntds/article?id=10.1371/journal.pntd.0006732>


ref: Cook CL, Huang YS, Lyons AC, et al. North American _Culex
pipiens_ and _Culex quinquefasciatus_ are competent vectors for Usutu
virus. PLoS Negl Trop Dis. 2018; 12(8): e0006732. doi:
10.1371/journal.pntd.0006732
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Abstract
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Background. Usutu virus (USUV) is a member of the Japanese
encephalitis virus (JEV) serocomplex in the Flaviviridae family.
Emergence of USUV in Europe has led to disease burdens in birds and
created increasing concern for the potential zoonotic transmission to
humans. Whilst USUV has not been detected in the New World, the
identification of competent vector species in North America is
critical in the assessment of the likelihood of its dispersal and
establishment of enzootic transmission cycles. The objective of this
study was to determine vector competence of potential mosquito vectors
in North America for USUV. 3 medically important mosquito species were
selected for testing because of their involvement in the transmission
of West Nile virus and St Louis encephalitis virus, 2 related JEV
serocomplex flaviviruses in the New World.

Methodology/principal findings. Oral challenge of _Culex pipiens_,
_Culex quinquefasciatus_, and _Aedes albopictus_ was performed to
determine the susceptibility and vector competence of North American
mosquitoes for USUV. Infection status was monitored by the isolation
of virus from homogenized mosquito tissues. The disseminated form of
infection was demonstrated by the detection of infectious virus in the
head, wings, and legs of infected mosquitoes. The presence of viral
RNA in saliva of infected _Cx. pipiens_ and _Cx. quinquefasciatus_
indicated that both species are competent for transmission of USUV.

Conclusions/significance. Results indicate that members of the _Cx.
pipiens_ complex are susceptible to USUV and competent for its
transmission potential in North America in the event of its
introduction. In contrast, _Ae. albopictus_ were highly refractory to
USUV infection, suggesting that this species is unlikely to contribute
to USUV transmission in North America.

Author summary
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Usutu virus is an emerging mosquito-borne flavivirus maintained
between avian and mosquito species. Although the pathogen has only
been detected in Africa and Europe, a growing concern of its dispersal
and zoonotic potential warrants the investigation on the vector
competence of mosquito species outside the endemic regions for USUV.
Identification of species involved in the transmission cycles allows
for the formulation of disease control strategies such as vector
control. As observed with West Nile virus and Japanese encephalitis
virus, the presence of competent vector species is critical for the
establishment of enzootic transmission cycles and contributes to the
viral maintenance in nature. Despite differences in the genetics and
bionomics of _Culex pipiens_ in the Old World, members of the _Cx.
pipiens_ species in the New World are competent for USUV based on the
results of per os challenges performed in this study. _Cx. pipiens_
and _Cx. quinquefasciatus_ are capable of initiating enzootic
transmission cycles in the presence of susceptible avian species and
should be targeted for vector control in the event of a disease
outbreak.

--
Communicated by:
ProMED-mail
<promed@promedmail.org>

[This is a good news/bad news report. The good news is that _Aedes
albopictus_, a mosquito expanding its range in the USA, was shown to
be refractory to USUV. The bad news is that 2 common and widely
distributed mosquito species, _Cx. pipiens_ and _Cx.
quinquefasciatus_, are susceptible to infection by that virus and
capable of initiating enzootic transmission cycles in the presence of
susceptible avian species.

Over the past 16 years, USUV become fairly widely distributed in
Europe with rare cases in humans and sporadic cases in birds. Although
it may seem very unlikely that USUV would arrive in North America from
Africa or Europe and become established, one only need remember West
Nile virus and its arrival in New York in 1999 and its subsequent
dissemination in the continental USA and much of the Americas to know
that this type of arrival and dissemination can happen when competent
vector mosquitoes are present and abundant, and just await the arrival
of the virus. - Mod.TY]

[See Also:
Usutu virus - Europe (02): France
http://promedmail.org/post/20180628.5881284
Usutu virus - Europe: France
http://promedmail.org/post/20180621.5868708
2017
----
Usutu virus - Europe (04): Austria
http://promedmail.org/post/20171012.5376689
Usutu virus - Europe (03): Germany (NW) blood donor
http://promedmail.org/post/20170413.4967711
Usutu virus - Europe (02): comment
http://promedmail.org/post/20170108.4749481
Usutu virus - Europe http://promedmail.org/post/20170107.4747454
2016
----
Usutu virus - Netherlands http://promedmail.org/post/20161110.4620228
2012
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Usutu virus - Germany (03) 1st case
http://promedmail.org/post/20120821.1255556
Usutu virus - Germany (02): blackbirds
http://promedmail.org/post/20120726.1215627
Usutu virus - Germany: mosquito isolate
http://promedmail.org/post/20120425.1114006
2011
---
Usutu virus - Germany (02): birds, conf.
http://promedmail.org/post/20110916.2827
Usutu virus - Germany: mosquito isolate, birds susp.
http://promedmail.org/post/20110913.2792
2009
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Usutu virus - Italy http://promedmail.org/post/20091217.4273
2006
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Usutu virus, avian - Switzerland: correction
http://promedmail.org/post/20060826.2427
Usutu virus, avian - Switzerland: corr.
http://promedmail.org/post/20060826.2426
Usutu virus, avian - Switzerland
http://promedmail.org/post/20060825.2402
2004
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2004 Usutu virus, avian - Austria (02)
http://promedmail.org/post/20041116.3084
2004 Usutu virus, avian - Austria
http://promedmail.org/post/20040827.2394
2003
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Usutu virus, avian - Austria (02): background
http://promedmail.org/post/20031024.2665
Usutu virus, avian - Austria http://promedmail.org/post/20031024.2661
2002
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Usutu virus, emergence in Europe (02)
http://promedmail.org/post/20020918.5339
Usutu virus, emergence in Europe
http://promedmail.org/post/20020722.4838]
.................................................ml/ty/mj/lxl
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