MicrobiologyBytes

A number of flaviviruses constitute a significant threat to global health. Dengue virus (DENV) infection causes around 21,000 human deaths annually, and it is estimated that at least 120 countries have endemic DENV transmission, whilst in recent years, West Nile virus (WNV) has become more prominent as a zoonotic agent, particularly in North America where the virus first emerged in 1999 and rapidly spread across the continent. WNV has now emerged in a number of European countries, particularly around the Mediterranean basin, where infections in humans, horses and birds have been reported.

Cross-reactivity of sera raised against one flavivirus recognising another flavivirus has been well documented. One consequence of flavivirus cross-reactivity is the occurrence of false-positive results, yet cross-reactivity can lead to cross-protection. Understanding and manipulating the cross-reactive properties of flaviviruses has the potential to assist the development of effective broad-spectrum human vaccines against WNV and other existing and emerging flaviviruses.

Flavivirus-induced antibody cross-reactivity. J Gen Virol. Sep 7 2011
Dengue viruses (DENV) cause countless human deaths each year, whilst West Nile virus (WNV) has re-emerged as an important human pathogen. There are currently no WNV or DENV vaccines licensed for human use, yet vaccines exist against other flaviviruses. To investigate flavivirus cross-reactivity, sera from a human cohort with a history of vaccination against tick-borne encephalitis virus (TBEV), Japanese encephalitis virus (JEV) and yellow fever virus (YFV) were tested for antibodies by plaque reduction neutralisation test. Neutralisation of Louping ill virus (LIV) occurred, but no significant neutralisation of Murray Valley encephalitis virus (MVEV) was observed. Sera from some individuals vaccinated against TBEV and JEV neutralised WNV, which was enhanced by YFV vaccination in some recipients. Similarly, some individuals neutralised DENV-2, but this was not significantly influenced by YFV vaccination. Antigenic cartography techniques were used to generate a geometric illustration of the neutralisation titres of selected sera against WNV, TBEV, JEV, LIV, YFV and DENV-2. This demonstrated the individual variation in antibody responses. Most sera had detectable titres against LIV and some had titres against WNV and DENV-2. Generally, LIV titres were similar to titres against TBEV, confirming the close antigenic relationship between TBEV and LIV. JEV was also antigenically closer to TBEV than WNV, using these sera. The use of sera from individuals vaccinated against multiple pathogens is unique relative to previous applications of antigenic cartography techniques. It is evident from these data that notable differences exists between amino acid sequence identity and mapped antigenic relationships within the family Flaviviridae.

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A ProMED-mail post
Date: Wed 22 Jul 2009
Source: Emax Health [edited]
http://www.emaxhealth.com/2/39/32382/east-london-crow-tests-positive-west-nile-virus.html

The Middlesex-London Health Unit announced that a dead crow found in London’s east end has tested positive for West Nile virus and is the 1st in Middlesex-London to test positive for the disease this year [2009].

“What this tells us is that West Nile virus is still present in our community and that we need to be vigilant in protecting ourselves from mosquito bites and reducing the places where they breed,” says Andrew Powell, Vector-Borne Disease Coordinator with the Middlesex-London Health. “The community has always been a great partner in our surveillance and control programs, whether by letting us know when they find dead birds or by eliminating standing water found on their properties.”

To protect yourself and your family against West Nile virus [infection], the Health Unit recommends:

• Wearing light coloured clothing with long-sleeves, pants and socks in areas where mosquitoes are present, especially at dusk and dawn when they are most active.
• Using an insect repellent with DEET. Follow directions for use, especially for children.
• Fixing holes in screens, windows and doors.
• Regularly emptying standing water from garbage cans, wheelbarrows, toys, flowerpots and saucers, pool covers, tires, and other items around your home and yard.
• Cleaning clogged eaves troughs.
• Cleaning and changing water in bird baths every other day.
• Keeping pool pumps circulating.
• Aerating ponds or stocking them with fish.
• Covering openings in rain barrels.

The MLHU Vector-Borne Disease Surveillance Team has made more than 2104 monitoring visits to approximately 220 sites this summer [2009], treating over 8 hectares of surface water; this is in addition to the treatment of more than 100 000 roadside catch basins in London and Middlesex County. Although the Health Unit is reporting its 1st West Nile Virus-positive bird, none of the mosquitoes trapped so far this summer have tested positive for the disease [virus]. [Byline: Ruzik Tuzik]

[This report provides additional evidence of the presence of West Nile virus (WNV) in the UK. Previous reports in 2006 indicated that sentinel chickens developed antibodies to WNV or a closely related flavivirus, and a 2003 publication reported detection of WNV neutralizing antibody and small WNV-related RNA fragments in migratory and resident wild birds (Journal of General Virology for October 2003. Buckley A, Dawson A, Moss SR, Hinsley SA, Bellamy PE, Gould EA. Serological evidence of West Nile virus, Usutu virus and Sindbis virus infection of birds in the UK <http://www.sgm.ac.uk/JGVDirect/19341/19341a.htm>). The question of whether WNV is endemic in the UK or periodically reintroduced by wild birds remains unresolved, but repeated detection of the virus or specific WNV antibodies would add weight for endemicity. - Mod.TY]

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