A horse protected by a vaccine against the West Nile Virus

West Nile Virus: How to Protect Your Horse

Lena Voss in Health & Wellness June 2025 • 4 min read.

"A new study reveals how a readily available vaccine can help prevent West Nile Virus in horses."

West Nile Virus (WNV) poses a significant threat to horses, particularly with the rise of neurological cases linked to lineage 2 strains in South Africa. Understanding the different lineages of WNV is crucial for effective prevention and treatment. Lineage 1 is found in North America, North Africa, Europe, and Australia, whereas Lineage 2 is endemic in central and southern Africa. This distinction is key to developing effective strategies to combat the virus.

Initially, WNV wasn't considered a major threat to horses in South Africa. However, recent increases in encephalitis cases linked to lineage 2 WNV have changed this perception. These infections often result in severe neurological symptoms, leading to high euthanasia rates, underscoring the urgent need for preventative measures.

Vaccines like the canarypox-WNV recombinant vaccine and inactivated WNV vaccines have been developed, primarily targeting lineage 1 strains. The effectiveness of these vaccines against lineage 2 WNV infections, however, requires careful evaluation. This study explores the potential of Duvaxyn WNV, an inactivated lineage 1 vaccine, to protect horses against both lineages.

Duvaxyn WNV: A Promising Solution

A horse protected by a vaccine against the West Nile Virus

The study, conducted with 22 seronegative horses, investigated the serum neutralising antibody responses after vaccination with Duvaxyn WNV. Horses were divided into two groups: a vaccinated group and an unvaccinated control group. The vaccinated group received two doses of Duvaxyn WNV, followed by a booster a year later. Blood samples were collected regularly to measure antibody titres against both lineage 1 (NY385/99) and lineage 2 (SPU93/01) strains of WNV.

The results showed that Duvaxyn WNV effectively stimulated high titres of serum neutralising antibodies against both WNV strains. After the initial two doses, antibody levels peaked, demonstrating the vaccine's ability to trigger a strong immune response. A single booster dose a year later resulted in an even stronger anamnestic response, with antibody titres rising significantly.

Effective Primovaccination: Duvaxyn WNV leads to high levels of serum-neutralising antibodies.
Strong Booster Response: A single dose after one year results in a significant increase in antibody titres.
Dual Lineage Protection: Effective against both Lineage 1 and Lineage 2 WNV strains.
Annual Booster: Could be sufficient to maintain immunity against Lineage 2 WNV.

While antibody titres against lineage 2 WNV (SPU93/01) were slightly lower compared to lineage 1 (NY385/99), the overall response was robust and consistent. This suggests that Duvaxyn WNV can offer cross-protection against different WNV lineages, which is crucial in regions where multiple strains circulate. The consistency and strength of the immune response underscore the potential of Duvaxyn WNV as a valuable tool in WNV prevention.

Protecting Your Horse: Key Takeaways

These findings reinforce the importance of vaccination in protecting horses from WNV. Duvaxyn WNV has demonstrated the ability to stimulate a strong immune response against both lineage 1 and lineage 2 WNV strains. This suggests that a single annual booster may be sufficient to maintain immunity against lineage 2 WNV, offering a practical and effective approach to WNV prevention in horses.

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This article is based on research published under:

DOI-LINK: 10.4102/jsava.v84i1.1052, Alternate LINK

Title: Serum Neutralising Antibody Response Of Seronegative Horses Against Lineage 1 And Lineage 2 West Nile Virus Following Vaccination With An Inactivated Lineage 1 West Nile Virus Vaccine

Subject: General Veterinary

Journal: Journal of the South African Veterinary Association

Publisher: AOSIS

Authors: Michael C. Pearce, Marietjie Venter, Tjitske Schouwstra, Charmaine Van Eeden, Petrus Jansen Van Vuren, Janusz Paweska, Bo Liu, Arrie Du Plessis

Published: 2013-11-21

Everything You Need To Know

What makes West Nile Virus a significant concern for horse owners?

West Nile Virus poses a threat to horses because it can lead to severe neurological symptoms and high euthanasia rates, especially with the emergence of lineage 2 strains. Understanding the different lineages is crucial because lineage 1 is prevalent in North America, North Africa, Europe, and Australia, while lineage 2 is endemic in central and southern Africa. Equine Encephalitis can result from West Nile Virus.

How does the Duvaxyn WNV vaccine work to protect horses against West Nile Virus, and how does it compare to other vaccines?

Duvaxyn WNV is an inactivated lineage 1 vaccine that has shown promise in protecting horses against both lineage 1 and lineage 2 strains of West Nile Virus. A study showed that it stimulates high levels of serum-neutralising antibodies against both WNV strains. While antibody titres against lineage 2 WNV (SPU93/01) were slightly lower compared to lineage 1 (NY385/99), the overall response was strong and consistent. Other vaccines mentioned include the canarypox-WNV recombinant vaccine and inactivated WNV vaccines.

Can you explain the setup of the study that evaluated the effectiveness of the Duvaxyn WNV vaccine?

The study involved vaccinating horses with Duvaxyn WNV and measuring their antibody responses to West Nile Virus lineage 1 (NY385/99) and lineage 2 (SPU93/01) strains. The horses received two initial doses of Duvaxyn WNV, followed by a booster a year later. The study tracked serum neutralising antibody responses in vaccinated and unvaccinated control groups to assess the vaccine's effectiveness. The results indicated a strong immune response, suggesting that Duvaxyn WNV can offer cross-protection against different WNV lineages.

What did the study reveal about the antibody response after administering Duvaxyn WNV, including the booster?

Following the initial two doses of Duvaxyn WNV, antibody levels peaked, demonstrating the vaccine's ability to trigger a strong immune response. A single booster dose a year later resulted in an even stronger response, with antibody titres rising significantly. This suggests that an annual booster of Duvaxyn WNV may be sufficient to maintain immunity against lineage 2 WNV, though antibody titres against lineage 2 WNV (SPU93/01) were slightly lower compared to lineage 1 (NY385/99), the overall response was robust and consistent.

What are the implications of these findings for West Nile Virus prevention in horses, especially regarding the different virus strains?

The finding suggests that Duvaxyn WNV can effectively protect horses against both lineage 1 and lineage 2 strains of West Nile Virus. Given the rise of neurological cases linked to lineage 2 strains, particularly in regions like South Africa, this vaccine provides a practical way to prevent WNV in horses. The potential need for annual boosters offers a manageable approach to maintaining immunity and reducing the risk of infection. The Duvaxyn WNV vaccine can help prevent West Nile Virus in horses.