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WEST NILE VIRUS - FORMER SOVIET UNION: BACKGROUND
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Date: 26 Aug 2006 11:22:47 -0400
From: Steve Berger <mberger@post.tau.ac.il>
Source: GideonOnline [edited]
<http://www.GideonOnline.com>
Endemic areas for West Nile virus in the former Soviet Union include
Ukraine, Belarus, the southern area of European Russia (regions of
desert, steppe, and deciduous forests) and the western Siberia-Altai
territory (steppe and combined forest-steppe), Armenia, Azerbaijan,
Kazakhstan, Tajikistan, Uzbekistan, and Turkmenistan.
- Since the 1970s, illness has been observed in Kazakhstan and the
republics of Central Asia, Astrakhan region (in Russia), Ukraine, and
Azerbaijan.
- High risk exists in the desert territories of the Volga basin.
Seropositive humans have been identified in Armenia and Georgia.
- Seropositivity rates of 0.4 percent to 8 percent were demonstrated
among healthy blood donors in European Russia and western Siberia
during 1963 to 1993.
- 1.7 percent of the general Belarusian population are seropositive:
5.8 percent in Gomel, and 15.4 percent in Brest Region; 0.6 to 5.8
percent of cattle, 2.9 to 6.8 percent of wild small mammals, and 6.5
to 16.7 percent of birds.
Chronology:
- 1963 to 1968 - At least 10 cases of human disease were reported in
the Volga Delta. At the time, the virus was recovered from ticks,
water birds and mosquitoes.
- 1977 - Cases of human disease were reported in the area of Brest
(Belarus). Additional cases were reported during the 1980s.
- 1997 - 38 cases (16 with encephalitis) were reported in Ukraine.
- 1999 - An outbreak (826 suspect cases, 84 with meningoencephalitis,
40 fatal) was reported in southern Russia (Volgograd, Astrakhan, and
Krasnodar regions). Seropositivity rates in the Astrakhan region
increased from 31.6 percent in 1998 to 44.4 per cent in 1999.
- 2002 - An outbreak (33 cases) was reported in the Astrakhan region,
most from the Volga middle delta.
- 2004 - 3 cases were reported in West Siberia.
- 2005 - An outbreak (73 cases, 3 fatal) was reported in the
Astrakhan region and 15 in the Rostov region.
Local vectors include _Culex pipiens_, _C. modestus_ and _Aedes vexans_.
- The key ornithophilic vector is _Culex molestus_. Both _C.
modestus_ and _C. pipiens_ feed on birds as well as humans.
- Additional regional [tick] vectors include _Ornithodoros capensis_
(Azerbaijan), _Hyalomma marginatum_ (Astrakhan and Azerbaijan), _Hy.
detritum_ (Turkmenistan) and _Rhipicephalus turanicus_ (Azerbaijan).
- Potential anthropophilic [mosquito] vectors in the Volgograd region
include _Culex modestus_, _Aedes vexans_, _Coquillettidia
richiardii_, _Ae. caspius_, and _Cx.
pipiens_.
- Local vectors in Ukraine iclude _Aedes cantans_, _Ae. caspius_,
_Ae. circumluteolus_, _Ae. excrucians_ and _Anopheles maculipennis_.
In the Volga Delta, 56 species of birds are involved in virus circulation.
- In the coastal area of the Delta, the most important hosts are
shore birds (notably in the order Gressores): the green heron
(_Nicticorax nicticorax_) - of which 45 percent are seropositive;
great cormorant (_Phalacrocorax carbo_); coot (_Fulica atra_), water
hen (_Gallinula chloropus_); and great grebe (_Podiceps cristatus_);
and to a lesser extent gulls and terns.
- In the agricultural region of the Delta, 20 species of birds
(particularly rooks, crows, and pigeons) are involved in virus
circulation.
- In the Kuban and Terek River Deltas, the most important birds are
herons, coots, and some wild ducks.
- West Nile virus was identified in the southern portion of Western
Siberia during 2002 in dead rooks (_Corvus frugilegus_), teal (_Anas
crecca_) and garganey (_Anas querquedula_).
- Circulation of West Nile virus among birds was confirmed in the far
eastern region of Russia during 2003 to 2004 - among cinereous
vultures (_Aegypius monachus_ and cattle egrets (_Bubulcus ibis_).
- During 2004, infection was also confirmed in _Ixobrychus
eurhytmus_, _Pica pica_, _Corvus macrorhynchos_ and _Falco
tunnuncules_.
- Wild birds which nest in Azerbaijan are involved in the
transmission of West Nile virus in the European region.
--
ProMED-mail
<promed@promedmail.org>
[Caution must be exercised when determining the role of arthropod
vectors and vertebrate animals in the transmission and maintenance of
a virus in any given region. Mere isolation of the virus from a
field-collected arthropod does not establish its capacity to serve as
a vector. That is done by determining its relative susceptibility
following ingestion of a blood meal containing a known amount of
virus, replication of the virus in the body of the arthropod, the
subsequent presence of the virus in salivary glands followed by
transmission by bite to a susceptible vertebrate animal. The
arthropod must be associated with host vertebrates in nature at the
time and in the place that these hosts are viremic.
Similarly, serological data have to be interpreted with caution.
Presence of antibodies to a given virus simply indicates that they
were exposed to it, and does not prove that the animal developed a
viremia of high enough titer and sufficient duration to infect
arthropod vectors. Establishing vector and host capacity requires
laboratory experiments under conditions of adequate biological
safety. These experiments are expensive to conduct.
A map of the former Soviet Union can be accessed at:
<http://www.lib.utexas.edu/maps/europe/europe_ref04.jpg>
ProMED thanks Dr. Berger for providing this summary. - Mod.TY]
[see also
West Nile virus - Russia (Astrakhan) 20060826.2417
2005
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West Nile virus - Russia 20051106.3246
West Nile virus - Russia (Astrakhan) (02) 20051007.2927
West Nile virus- Russia (Astrakhan) 20050911.2688
West Nile virus, human, 2004 - Russia (West Siberia) 20050131.0332
West Nile virus, birds, 2003-2004 - Russia (Far East) 20050124.0260
2004
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West Nile virus, vulture - Russia (Vladivostok) 20040630.1744
West Nile virus, birds, 2003 - Russia (Siberia) 20040426.1162
2003
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West Nile virus, birds, 2002 - Russia (Siberia) 20030516.1216
1999
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West Nile virus infection - Russia (Volgograd) 19990915.1651]
..............................................dk/ty/pg/lm
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