Introduction
Venezuela Equine Encephalitis (VEE) is a mosquito-borne viral disease that causes infection in humans and equines.1 VEE is caused by Venezuelan Equine Encephalitis Virus (VEEV) and is endemic in Central and South America, with the majority of outbreaks occurring in Venezuela, Colombia, Peru, Ecuador, Costa Rica, Nicaragua, Honduras, El Salvador, Guatemala, Mexico and the United States.1 VEEV is a natural pathogen and affects humans and equines including:
- Horses
- Donkeys
- Zebras
- Mules
VEEV infection in adults usually presents as a flu-like illness but children are more likely to develop neurological disease or encephalitis. Neurological disorders are complications associated with initial VEEV infection and these can include:1
- Seizures
- Intellectual disabilities
- confusion
- Behavioural changes
Pregnant women are also at an increased risk of complications from VEEV infection with miscarriages, congenital disabilities for their babies, stillbirth and early delivery being possible.1
Overall, complications associated with VEE can range from mild and manageable to life-changing conditions. It is important to understand the complications of VEE, to better manage and treat conditions associated with VEEV infection, especially considering that there is no specific treatment against VEEV infection.1 Understanding how to cope with complications can improve patients' quality of care. This article will discuss how to cope with complications caused by VEE.
Understanding venezuelan equine encephalitis (VEE)
Causes
VEE is caused by the VEE virus which is a single-stranded alphavirus that belongs to the Togaviridae family.1 VEEV is a pathogen that is transmitted by mosquitoes and infection occurs with the mosquito acting as a vector. Transmission occurs between mosquitoes and an equine species and between humans and mosquitoes.1
There are six subtypes of the VEE virus, I - VI and within each subtype there are many variants.1 VEEV can be split into two types of strains: epizootic strains, which are outbreaks that infect a large population very quickly, and enzootic strains, which are strains always present in the population at low numbers.2
Epizootic strains include subtype I, variants A, B and C and they are responsible for causing epidemic outbreaks in both human and equine populations.1 Epizootic strains are highly pathogenic and spread through the population quickly and the main reservoirs are horses.1 These strains are responsible for causing severe disease including encephalitis in both equine and human populations.1
Enzootic strains are subtype 1, variant D and E and Subtypes II-VI and they usually cause mild or no illness in equines but they can however cause severe disease in humans.1 Enzootic strains are found circulating in rodents and when mosquitoes cycle between rodents and humans, VEE infection can occur leading to human epidemics.1
Transmission
Mosquito vectors
VEEV is transmitted by mosquitoes. Ochleratus taeniorhychus is the main mosquito transmitting epizootic strains and Culex species responsible for transmitting enzootic strains.1 Mosquitoes become infected when they feed on reservoirs that contain the virus, such as horses or rodents and they then spread the virus, which is present in their salivary glands, to another host during the next feed.3
Animal reservoirs
Enzootic subtypes are detected and isolated from ecological habitats where there is a rodent-mosquito cycle. Species such as Oryzomys, Zygodontomys, Heteromys and Proechimys are the main reservoirs of VEEV.3 When the animal becomes infected with VEEV naturally, and a mosquito feeds on the rodent, it then becomes infected and will transmit the virus, spreading the virus to other organisms such as humans, causing an infection. The main reservoir for epizootic strains is in the equine population.
Symptoms of VEE include4
- Fever
- Headache
- Anorexia
- Weight loss
- Weakness
- Depression
- Dehydration
- Weakness
- Paralysis
- Difficulty in swallowing and sore throat
- Inflammation in the brain
- Seizures and other neurological disorders
Diagnosis
VEE is diagnosed in the lab using blood samples. Testings include ELISA, or PCR on blood or cerebrospinal fluid to identify the virus in the samples.4
Common complications of VEE
Complications of VEE can be separated into three categories:
- Neurological Complications
- Physical complications
- Psychological complications
Neurological complications
VEE is associated with neurological conditions and these can include:1
- Seizures: These are uncontrolled electrical activity in the brain and can cause confusion, loss of consciousness, jerky movements of limbs and cognitive or emotional changes. Seizures can occur after an infection such as VEEV5
- Encephalitis: Is a life-threatening condition when the brain becomes inflamed.6 It can lead to confusion, seizures, difficulty in speaking, changes in behaviour and loss of consciousness
- Long-term cognitive deficits: Include problems with memory when patients have difficulties remembering their names, and important events, losing focus in conversations, poor judgement and acting impulsively7
Physical complications
Muscle weakness: is a term to describe a lack of muscle strength, making daily tasks more difficult to complete. Patients may have reduced strength, they are more fatigued and their limbs are more heavy.
Psychological complications
Anxiety: can be described as feeling uneasy or worried and this can be triggered by physical impairments caused by VEE, such as feeling fatigued and struggling with daily activities.
Depression: is when a patient is persistently sad for a long period and this can be caused by the prolonged recovery needed to overcome VEE infection and the impact VEE may have on the patient’s daily life.
Medical management of complications
Managing VEE complications is important as there is no treatment available against VEEV1. Management of complications can be separated into immediate medical response and symptomatic treatment.
Immediate medical response
There are no human vaccines or antiviral treatments against VEE infection. However, complications can be treated. Encephalitis is a life-threatening condition and will require immediate treatment,6 but there is no antiviral treatment available. Anti-inflammatory medications such as corticosteroid medicine are given to reduce inflammation in the brain to treat encephalitis.6
Symptomatic treatment
Complications caused by VEEV are mainly treated by treating the symptoms. For seizures, anti-seizure medication is given to stop having seizures. To treat encephalitis, patients will be placed in intensive care units, where fever is managed, pain relief is given and oxygen is supplied mechanically using respiratory support. For physical complications such as muscle weakness, pain medication is used to reduce pain felt by the patients and physical therapy to regain muscle strength.
Rehabilitation and long-term care
Treating complications associated with VEE will require rehabilitation and long-term care management to provide the best care for patients and to recover from VEE infection.
Neurological rehabilitation
Cognitive impairment can in some cases be reversible but in most cases, treatment will be required to improve cognitive impairment and reduce its impact on the patient.7
- Cognitive Therapy: This is a therapy focused on managing behaviour, thoughts and feelings, by changing how the patient handles their thoughts. Reducing negative thinking patterns and replacing them with positive thoughts can improve patient care and quality of life despite neurological conditions caused by VEE infection.
- Occupational Therapy: This is aimed at assisting patients struggling with completing daily tasks. Cognitive impairment is a complication caused by VEEV and a symptom would be struggling to complete daily tasks every day and occupational therapists help patients to carry out said tasks.
Physical rehabilitation
- Physiotherapy: This is an approach to help patients regain movement and strength following VEEV infection. As mentioned above, muscle weakness is a complication caused by VEE, and physiotherapy is used to help patients by giving patients advice and exercise to improve mobility.
- Exercise programs: Exercise is a great way to physically rehabilitate yourself following a VEEV infection. It is important to regain strength loss and to strengthen the muscles to aid you in daily activities and for your general health.
Psychological support
Complications like anxiety and depression will take long-term care and this is done through counselling and therapy sessions. Psychological support is important for a patient to deal with the emotional and psychological conditions caused by VEEV infection and the lasting impact on their daily life. Support groups are also important for the patients and their families and caregivers.
Coping strategies for patients and families
Coping with complications caused by VEEV may be difficult for both patients and their families and having strategies is important for their well-being. These can include:
- Improving education and awareness: Government and healthcare officials should push more for public understanding of VEE and the potential signs of complications. This is even more important for conditions such as life-threatening encephalitis.
- Changing lifestyle: having a healthy diet, regular exercise and sleeping well is important for everyone, but especially for patients following any infection, to help speed up recovery and recover from complications.
- Stress management: mental health is just as important as physical health and patients and their family should not neglect their mental health. Mindfulness techniques and using mental health resources such as counselling or therapy are important and should be offered by medical professionals.
Preventative measures
As there is no treatment against VEEV, prevention is even more important to prevent complications caused by VEEV.
Vector control
Vector control is one of the most important preventative measures. Controlling mosquito vectors is an important strategy employed to reduce transmission of VEEV, therefore reducing complications caused by VEEV. Reducing mosquito is possible by:
- Larval source reduction
- Insecticide spraying
Vaccination programs
Vaccination of equids is the best method to reduce transmission of the VEE virus and has been used since 19301 through TC-83. However, there are no vaccines for humans but the TC-83 vaccine (available for equines) has been used to provide immunity for those who work in laboratory research.1
Conclusion
Venezuela Equine Encephalitis (VEE) is a mosquito-borne viral disease that causes infection in humans and equines. VEEV infection in adults usually presents as flu-like illness but complications such as neurological, psychological and physical disorders can occur following VEEV infection.
Managing VEE complications is important as there is no treatment available against VEEV.1 Management of complications can be separated into immediate medical response and symptomatic treatment. Regardless of which route treatment takes, treatment of complications associated with VEE will require rehabilitation and long-term care to provide the best care for patients.
Most VEEV infections will cause flu-like illness but in some individuals, complications can occur. With early diagnosis, and early treatment, the outcome of the patient is improved and recovery is possible.
References
- Crosby, Brianna, and Maria E. Crespo. ‘Venezuelan Equine Encephalitis’. In StatPearls. Treasure Island (FL): StatPearls Publishing, 2024. http://www.ncbi.nlm.nih.gov/books/NBK559332/.
- Shapiro-Ilan, David I., Denny J. Bruck, and Lawrence A. Lacey. ‘Chapter 3 - Principles of Epizootiology and Microbial Control’. In Insect Pathology (Second Edition), edited by Fernando E. Vega and Harry K. Kaya, 29–72. San Diego: Academic Press, 2012. https://doi.org/10.1016/B978-0-12-384984-7.00003-8.
- Guzmán-Terán, Camilo, Alfonso Calderón-Rangel, Alfonso Rodriguez-Morales, and Salim Mattar. ‘Venezuelan Equine Encephalitis Virus: The Problem Is Not over for Tropical America’. Annals of Clinical Microbiology and Antimicrobials 19, no. 1 (19 May 2020): 19. https://doi.org/10.1186/s12941-020-00360-4.
- Young, Amy. ‘Venezuelan Equine Encephalitis (VEE) | School of Veterinary Medicine’, 28 August 2020. https://ceh.vetmed.ucdavis.edu/health-topics/venezuelan-equine-encephalitis-vee.
- Mayo Clinic. ‘Seizures - Symptoms and Causes’. Accessed 24 May 2024. https://www.mayoclinic.org/diseases-conditions/seizure/symptoms-causes/syc-20365711.
- nhs.uk. ‘Encephalitis - Treatment’, 3 October 2018. https://www.nhs.uk/conditions/encephalitis/treatment/.
- ‘Cognitive Impairment’. Accessed 24 May 2024. https://www.icudelirium.org/patients-and-families/cognitive-impairment#:~:text=Signs%20of%20Cognitive%20Impairment&text=Display%20problems%20with%20memory%20including,Use%20poor%20judgment.