Eastern equine encephalitis (EEE) is a serious viral disease that causes inflammation of the brain, with the potential for significant neurological damage. The EEE virus has a particular tropism for the central nervous system, primarily affecting the brain and spinal cord.
Brain Regions and Subregions Affected
- Cerebral Cortex: The cerebral cortex, responsible for higher cognitive functions such as thinking, memory and perception, can be affected, resulting in mental confusion, personality changes and learning difficulties.
- Basal Ganglia: The basal ganglia, involved in motor control and learning skills, can be damaged, leading to tremors, involuntary movements, and coordination difficulties.
- Thalamus: The thalamus, which acts as a relay center for sensory and motor information, can be affected, causing sensory changes, such as numbness or tingling, and motor difficulties.
- Brain Stem: The brain stem, responsible for vital functions such as breathing and heartbeat, can be compromised, leading to breathing difficulties, changes in heart rate and, in severe cases, coma and death.
Neurotransmitters Affected
Inflammation caused by the EEE virus can lead to an imbalance in neurotransmitters, chemicals that allow neurons to communicate. Some of the neurotransmitters that can be affected include:
- Dopamine: Dopamine, involved in motor control, motivation and the reward system, can be reduced, resulting in tremors, difficulty moving and apathy.
- Serotonin: Serotonin, which regulates mood, sleep and appetite, can be affected, leading to mood changes such as depression and anxiety, sleep disturbances and changes in appetite.
- Glutamate: Glutamate, an important excitatory neurotransmitter, can be released in excess during inflammation, causing excitotoxicity and neuronal damage.
- GABA: GABA, an inhibitory neurotransmitter, can be reduced, leading to increased neuronal excitability and seizures.
Mosquito Vector Biology
The EEE virus is transmitted primarily by mosquitoes of the genus Culex. These mosquitoes breed in moist areas such as marshes, swamps, and flooded areas. Females feed on blood to obtain the nutrients needed to produce eggs. During feeding, they can acquire the EEE virus from infected birds and subsequently transmit it to horses, humans, and other susceptible mammals.
Details of Mosquito Biology
- Life Cycle: Culex mosquitoes go through four stages of development: egg, larva, pupa, and adult. The complete life cycle can take 7 to 10 days, depending on temperature and food availability.
- Feeding Habit: Females feed on blood, while males feed on nectar and plant juices. Blood feeding is essential for egg production.
- Behavior: Culex mosquitoes are most active at dusk and dawn, when temperatures are milder. They are attracted to light, heat, and carbon dioxide exhaled by animals.
- Distribution: Culex mosquitoes are found worldwide in areas with temperate and tropical climates.
Prevention
Prevention of EEE involves measures to reduce the population of mosquito vectors, such as eliminating breeding sites, using insect repellents, and wearing protective clothing. Vaccination of horses is also an important measure to prevent the disease in animals and reduce the risk of transmission to humans.
