About a month ago, the State Veterinarians Office reported the first case of West Nile Virus (WNV) diagnosed in a Colorado horse in 2010.
Since that time, five more cases have been reported to the State Veterinarian’s Office in Colorado, for a total of six cases.
The 2010 WNV positive equine cases have been plotted on a map which is posted on a website at www.colorado/gov/ag/animals under the “News” heading. The WNV-positive horses that have been diagnosed are located throughout the state and are not localized to a particular region of the state. Positive equine cases have been reported from La Plata, Mesa, Montezuma, Prowers, Pueblo and Weld counties.
West Nile Virus is a disease that threatens the health of humans, horses and other animals. The greatest implication of this disease is the virus’ capability to cause encephalitis (inflammation of the brain) in humans and horses, which may result in death. Clinical signs may include muscle tremors, hyper excitability, and weakness of the hind legs, paralysis, lethargy, incoordination, recumbency and fever in some cases.
If you see horses that are exhibiting clinical signs consistent with WNV, it is very important to confirm the diagnosis through laboratory testing. Other neurological diseases such as rabies, Western Equine Encephalitis, equine herpes virus, myeloencephalopathy (EHM), or other equine neurological conditions could present with similar clinical signs. It is also important that the State Veterinarian’s Office is able to obtain accurate and complete disease incidence data as it tracks positive equine neurological cases. In the situation where a horse has expired and serology is not possible, brain tissue can be submitted to the CSU veterinary diagnostic laboratory for PCR testing.
The West Nile Virus can be carried by infected birds and then spread locally by mosquitoes that bite these birds. The mosquitoes can then pass the virus to humans and animals; transmission does not occur from an infected horse to humans.
Late summer and early fall have traditionally been the time of year when we are most likely to see WNV cases reported in horses. How many more cases will be seen this year is impossible to predict, but the WNV-positive cases presented to date highlight the importance of immunization against this serious equine disease. Immunization of horses has proven to be an effective tool in the prevention of WNV.
Another important WNV prevention strategy involves vector control. Vector control involves eliminating breeding sites for mosquitoes, minimizing exposure during active mosquito feeding times (dawn and dusk) by stalling horses and using fans, using repellants, and larvae control in ponds and water sources.
The State Veterinarians Office is advising horse owners to consult their private practicing veterinarian to determine an appropriate prevention strategy for their horses.