What do human beings and horses have in common? They share a susceptibility to western equine encephalitis (WEE).
Culex tarsalis mosquitoes are the agents that spread the WEE virus. Culex tarsalis mosquitoes are generally known to make their homes around farms and irrigated fields.
Cases of western equine encephalitis in both humans and horses are fortunately rare. Less than a thousand cases have been reported since 1964.
Aduts are rarely struck with symptoms of WEE, though infants, children and the elderly can be more vulnerable. WEE has the potential to deliver a powerful impact on the central nervous system.
Western equine encephalitis was first seen and identified in a horse in the state of California in 1930. The usual location for WEE is west of the Mississippi, in the U.S., Canada and Mexico. Most known cases have been in the plains of western and central United States.
The western equine encephalitis virus is an arbovirus. This name is a shortened version of arthropod-borne virus. In the U.S., arboviruses are generally transmitted by mosquitoes, with birds sometimes being involved in the spreading of the infection.
Symptoms can appear five to 10 days after being bitten by an infected mosquito. Usually the western equine encephalitis virus will not cause serious symptoms though it does have the capacity to be fatal after causing a profound breakdown in the central nervous system.
Mild cases may cause headaches and fevers. More severe symptoms can be sleepiness, headache, high fever, nausea and vomiting.
Cognitive confusion, weakness, brain damage and coma can also occur. In the case of an infected infant, seizures are possible.
Other symptoms that may be experienced are vertigo, chills, abdominal pain, diarrhea, breathing problems, stiff neck, weakness and excessive sensitivity to light (photophobia).
While infection is relatively uncommon, small outbreaks can occur in a localized area. More people are moving into regions that were previously unpopulated by people but inhabited by infected mosquitoes and birds. As this trend continues, it may increase the risk for infection by the western equine encephalitis virus.
Infection with the western equine encephalitis virus is most likely to occur between April and September. July and August seem to be the peak months.
A doctor can make a diagnosis of western equine encephalitis based on blood tests or spinal fluid tests. Treatment is limited to the easing of symptoms. There are no vaccines or medications that can treat WEE.
Western Equine Encephalitis
eMedicine: Western Equine Encephalitis
Franklin County Mosquito Control District: Western Equine Encephalitis
Citizendia.org: Western Equine Encephalitis Virus
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