Venezuelan Equine Encephalitis Symptoms

Introduction

Venezuelan equine encephalitis is an acute mosquito-transmitted disease caused by the Venezuelan equine encephalitis virus. Mosquitoes spread the virus, which primarily affects horses, humans, and wild animals. The spread of Venezuelan equine encephalitis virus varies in speed and intensity depending on the viral subtype and the densities of mosquito populations. The transmission is produced when a mosquito, known as the vector, bites an infected animal and then bites another host, passing on the infection. The epizootic subtypes of Venezuelan equine encephalitis virus are more intense in the horse family where they spread rapidly and can be extremely harmful.¹

Outbreaks can cover extensive geographic regions and persist for months to years. Sporadic flare-ups are frequently observed in Central and South America. The Venezuelan equine encephalitis virus occurs naturally and has also been developed as a biological weapon in laboratories. Past outbreaks of epizootic strains have impacted up to 75,000 individuals during a single outbreak.²

Epizootic subtypes IAB and IC can cause serious disease in both humans and the horse family. Venezuelan equine encephalitis can affect people of all ages, and outbreaks typically do not show any preference based on sex. However, infected children are more prone than adults to experience long-term neurological issues and deadly encephalitis. Pregnant women who become infected with Venezuelan equine encephalitis virus are at risk for congenital disabilities, spontaneous abortions, preterm deliveries, and stillbirths.²

Venezuelan equine encephalitis is often diagnosed based on clinical symptoms, but it's likely that many cases are mistaken for other common fever-causing illnesses. However, there are laboratory tests available for confirmation.²

At present, there is no targeted treatment available for Venezuelan equine encephalitis. Medical care mainly focuses on providing supportive measures. While many infections resolve on their own, some individuals may experience lasting neurological complications.²

Since there's no cure for Venezuelan equine encephalitis, the best way to prevent it is by avoiding infection. Controlling flare-ups involves reducing mosquito numbers. People, especially those in close contact with the horse family, should minimise physical exposure to mosquitoes, wear protective clothing and use repellents regularly.²

While there is no FDA-approved human vaccine at present, TC-83 is a vaccine that has been used in both humans and horses. However, it's not readily accessible to the general public and is usually reserved for individuals with a high exposure risk such as those working in the laboratory or military.²

It's crucial for people living and working in areas where Venezuelan equine encephalitis is common to be able to recognize the signs and symptoms of the illness. This helps in controlling its spread. In this article, we'll delve into these symptoms, so keep reading for more information!

Clinical presentation of Venezuelan equine encephalitis

Patient History

In cases where patients report being exposed to mosquitoes in an area where Venezuelan equine encephalitis is prevalent, Venezuelan equine encephalitis should be considered as a possible diagnosis. Additionally, individuals experiencing fever after recent travel to rural regions of Central America or tropical South America should be suspected of having either Venezuelan equine encephalitis or dengue fever.³

Venezuelan equine encephalitis infection typically shows symptoms similar to the flu about 1 to 6 days after infection. While some individuals may carry the virus without displaying symptoms, the frequency of asymptomatic cases remains uncertain.³

The early signs of infection typically involve feeling tired, weak, and unwell, along with experiencing fever, chills, muscle aches, lower back pain, nausea, vomiting, and extreme fatigue. Some individuals may also experience a severe headache, sometimes with sensitivity to light. Fever might decrease temporarily, only to return the next day. These initial symptoms may be followed by diarrhoea and a sore throat.³

Children are especially vulnerable to developing serious central nervous system involvement, such as encephalitis. Symptoms of this involvement may include disorientation, drowsiness, stiffness in the neck, convulsions, inappropriate antidiuretic hormone secretion, paralysis, coma, and even death. Moreover, contracting an infection while pregnant can result in fetal death or miscarriage, and a congenital infection can lead to malformations in the central nervous system.³

The majority of Venezuelan equine encephalitis virus infections in humans result in mild symptoms that typically last for 3-5 days. While most individuals recover within 5 days, some may experience symptoms for up to 2 weeks.³

Physical examination

Fever is frequently observed in humans with Venezuelan equine encephalitis virus infection. Other common physical signs include rapid heartbeat, pharyngitis, conjunctival congestion, flushed face, and sometimes swelling of lymph nodes. In some instances, patients may also experience drowsiness, sensitivity to light, and mild confusion as the infection progresses.³

Few patients with severe neurologic complications from Venezuelan equine encephalitis exhibit notable physical symptoms such as stiffness in the neck, stupor, delirium, coma, nystagmus, cranial nerve palsies, abnormal reflexes, ataxia, stiffness, and spastic paralysis. Tremors, unusual movement patterns, and visual field defects are less frequently observed in these cases.³

In horses, symptoms of infection such as fever, rapid heart rate, anorexia, and depression typically show up about 2 days after getting infected. Some of these horses develop encephalitis within 5-10 days of infection. The animals might display signs of circling, ataxia, and being overly excited. Usually, death happens around 1 week after infection.³

Summary

Venezuelan equine encephalitis is a mosquito-transmitted disease caused by the Venezuelan equine encephalitis virus, primarily affecting horses, humans, and wild animals. Outbreaks can cover extensive regions and persist for months to years. The disease can cause serious complications in both humans and horses, with pregnant women and children being particularly vulnerable to severe neurological issues and fatal encephalitis.

Clinical presentation of Venezuelan equine encephalitis typically resembles flu-like symptoms, including fever, fatigue, muscle aches, nausea, vomiting, and headache. In severe cases, individuals may experience neurological symptoms such as disorientation, convulsions, paralysis, coma, and even death. Physical examination may reveal signs like fever, rapid heartbeat, pharyngitis, conjunctival congestion, and in severe cases, neurological deficits such as stiffness in the neck, delirium, and abnormal reflexes.

In horses, symptoms manifest as fever, anorexia, depression, and neurological signs like circling, ataxia, and excitement, with death typically occurring within a week of infection. Prevention involves reducing mosquito populations and minimising exposure to mosquitoes, while treatment focuses on supportive care as there is no specific cure or widely accessible vaccine for humans.