It’s in the news a lot these days. (As if Lindsay Lohan needed another problem in her life.)
Chikungunya (pronunciation: chik-en-GUN-ye) virus (CHIKV) is transmitted to people by mosquitoes. It literally means "that which bends up" in an African dialect. The most common symptoms of Chikungunya virus infection are fever and joint pain. Other symptoms may include headache, muscle pain, joint swelling or rash.
The virus was first identified in the mid-1950s but most of us were not too concerned because it resided in the Eastern Hemisphere.
That all changed in 2014. CHIKV jumped to the Americas with a profound impact in the Caribbean. It is estimated that over 1 million cases occurred this past year. Again, a lot of us said “Oh well, I’m not planning any riding in the Dominican Republic anytime soon.” Most of the cases seen in the U.S. were travel-related. However, Florida did have some isolated cases of local transmission.
What does 2015 have in store for us as far as CHIKV, and what does it mean for our horses? One of the reasons CHIKV did not spread much farther is that it is primarily carried by the Aedes aegypti mosquito, which has a limited range in the U.S.
We can learn from how the virus has acted in the rest of the world. If CHIKV were carried by the Asian Tiger mosquito, Aedes albopictus, things might be drastically different. Its normal range covers the Eastern Seaboard. An even scarier thought is that CHIKV has previously mutated and shown to be carried in exactly that way.
There is limited experimental evidence with CHIKV in horses, but we do have some clues. We know that horses can be very sensitive to theses types of virus (EEE, EVE, West Nile). Studies from Indonesia report that horses have shown an immune response to virus by developing antibodies to infection, but no horses have been documented to show a persistent spread of virus through the blood or virema. In fact, one study from the 1960s purposefully injected horses to evaluate their reaction and could not document any adverse effects or persistent viremia.
So, it is thought that horses have finally got one thing going for them against the nasty world of viruses. This was also confirmed in discussions with veterinary virologists from CHIKV endemic areas such as India and Venezuela. Although the disease is present there in high numbers, it does not seem to cause disease in horses but is definitely a problem in humans and non-human primates.
The best protection? Wear a good insect repellent and make sure that you apply it frequently.