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  Discussion on Vaccination against lineage 2 WNV
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DrO

Posted on Friday, Jul 17, 2015 - 12:14 pm:

In 2014 the incidence of lineage 2 WNV exploded into Europe leaving horse owners wondering does the current crop of vaccines, developed for lineage 1, protect. Earlier studies suggested yes but this was the first large scale field trial. Unlike the experimental models used earlier this field model suggested a much less pathogenic infection with only 10% of the controls that were infected becoming ill. This vaccine did show cross protection. Other vaccines have been tested and you will find more on this in the article West Nile Virus associated with this discussion area. You can access it from the navigation bar at the top of the page.
DrO

Clin Vaccine Immunol. 2015 Jul 15.
Cross-protection evaluation of a lineage 1 West Nile virus inactivated vaccine against natural infections from a virulent lineage 2 strain in horses, under field conditions.
Chaintoutis SC1, Diakakis N2, Papanastassopoulou M3, Banos G4, Dovas CI5.

Although experimental data regarding cross-protection of horse WNV vaccines against lineage 2 infections exist, their cross-protective efficacy under field conditions has not been demonstrated. This study was conducted to evaluate the capability of an inactivated lineage 1 vaccine (Equip WNV) to protect against natural infections from the Nea Santa-Greece-2010 lineage 2 strain. In total 185 WNV-seronegative horses in Thessaloniki-Greece, were selected during two consecutive years (2011-2012). One hundred and forty were immunized and 45 were used as controls. Horses were examined for signs compatible with WNV-infection. Neutralizing antibody titers against the Greek strain and the PaAn001/France lineage 1 strain were determined in immunized horses. WNV circulation was detected during both years in the study area. It was estimated that 37% and 27% of the horses were infected during 2011 and 2012, respectively. Three control animals developed clinical signs and WNV-diagnosis was confirmed. Signs related to WNV infection were not observed in vaccinated animals. Non-vaccinated animals were associated with a 7.58±1.82% higher chance of exhibiting signs compared to immunized (P<0.05). Neutralizing antibodies raised against both strains in all immunized horses were detectable one month after the initial vaccination course. The cross-protective capacity of the lowest titer (1:40) was evident in 19 animals which were subsequently infected, and did not exhibit signs. Neutralizing antibodies were detectable until the annual booster, where strong anamnestic responses were observed (GMTRlin.1=30.2, GMTRlin.2=27.5). Results indicate that Equip WNV is capable of inducing cross-protection in horses, against natural infections from a virulent lineage 2 WNV strain.
Member:
moxshi

Posted on Friday, Jul 17, 2015 - 12:59 pm:

Good to know! Especially as this year, I've never, EVER, seen the mosquitoes this bad. When I was feeding last night, I could hear a high-pitched whining that I didn't recognize, and kept trying to tell from which direction it was coming. My horses have been COVERED with mosquitoes when I lead them from paddock to barn through the grass (even when grass is mowed) and in their paddocks (pretty well eaten down) at dusk, their faces and cheeks, necks, bellies and sides are literally covered with the awful things and in the morning, the horses look textured with bumps rather than smooth and shiny.
When I looked up during spraying of a horse last night, I was almost traumatized by the CLOUD of mosquitoes over us . . . and that was where they whining sound was coming from!
I am so glad I had the horses vaccinated against WNV this year. I had skipped it last year.
Thanks for the info, Dr. O.}}
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