A woman checks on a donkey at an equine shelter in Lanus, Argentina, in a file photo. AGUSTIN MARCARIAN (Reuters)
Cases of Equine Encephalomyelitis have Argentine health authorities on tenterhooks. The National Service of Agri-Food Health and Quality (Senasa) reported on Saturday, November 25, the presence of positive cases of Alphavirus or equine encephalomyelitis in the departments of Lavalle, Corrientes and San Cristóbal, Santa Fe. The result was given after an analysis of samples from horses that presented nervous symptoms, or died. It is a disease caused by a viral infection that affects equines – such as horses, mares, donkeys, zebras and their hybrids – and in some cases can be transmitted to humans. Ximena Melón, director of animal health at Senasa, has confirmed that the cases occurred due to equine encephalomyelitis, in its Western variant, the same type that was diagnosed in the country in 1988.
"A meeting was held with the private sector and the broad call was made with all the representatives of the sector [...] and a series of issues that are specifically related to this finding were discussed," the official said in a video broadcast on the institution's social networks. Meanwhile, Senasa is coordinating the immediate availability of vaccines for equine livestock through veterinary chambers throughout the country. For its part, the College of Veterinary Physicians of the Province of Santa Fe reported on its social networks that this is a situation of mandatory reporting to Senasa, and that any case of equines with nervous symptoms, even if it is a suspicion, must be notified to the health authorities.
The alert for equine encephalomyelitis has reached Paraguay, a country that remains attentive to the possible appearance of cases. In a statement from the Ministry of Public Health and Social Welfare issued on Monday, Paraguayan authorities said that although no suspected or confirmed cases of the disease have been reported in the country, they have intensified surveillance of possible outbreaks and call on the population to go to the doctor if they present the signs of the disease.
What is equine encephalomyelitis?
Equine encephalomyelitis is a viral infection caused by a virus of the Togaviridae family, which is transmitted by mosquito bites. Equine encephalomyelitis – as the name suggests – affects equines, such as horses, mares and donkeys, and can cause severe encephalitis in animals and humans due to the damage it causes to the central nervous system.
There are three types of equine encephalomyelitis: Eastern, Western and Venezuelan. These diseases are considered exotic in Argentina, with the last official record dating back to 1988. According to Senasa, the case fatality rate in equines that get sick can reach 90% in the Eastern variant, and 20 to 30% in the Western variant, while Venezuela's oscillates in a greater range, ranging from 40 to 90%. Animals that survive any of the diseases can be left with sequelae. In humans, the lethality is estimated to be lower.
How is it transmitted?
This viral disease is transmitted from birds or small rodents to mosquitoes, which in turn infect horses and humans. According to the College of Veterinary Physicians of the Province of Santa Fe, the mosquitoes that transmit the disease are usually found in warm and humid areas. They become infected by biting a horse or other animal that is infected with the virus. They can then transmit the virus to other horses or humans by biting them.
The viruses that cause Eastern and Western equine encephalomyelitis usually develop in birds and rodents, and are then transmitted through mosquitoes. Medical research indicates that horses, humans, and other mammals are incidental hosts.
Equine encephalomyelitis transmission cycle. College of Veterinary Physicians of the Province of Santa Fe 1st Circ.
Once the virus is acquired, the incubation period of the disease, i.e. the time from infection to the appearance of clinical signs, is 5 to 14 days. Natural transmission between horses, or from horses to humans, has not been reported. Human-to-human transmission has also not been reported.
Can equine encephalomyelitis be transmitted to humans?
Yes. Both horses and humans can acquire the disease after being bitten by a mosquito carrying the virus. In humans, all three viruses may be able to cross the placenta, and congenitally infected children have been reported, according to the document "Review of the vaccination strategy against the equine encephalomyelitis virus of the East and West in the Argentine Republic." So far, the Ministry of Health has not reported any current cases in humans.
What are the symptoms in humans?
Eastern, Western, and Venezuelan equine encephalomyelitis have a number of signs and symptoms that vary slightly. In the case of Western equine encephalomyelitis, which is currently found in Argentina, humans usually have no symptoms, or it develops mildly in adults, with no specific signs of the disease and few deaths. It is possible to present abruptly:
- Occasionally, respiratory signs may be observed
It is important to pay attention to the appearance of symptoms such as headache, irritability, focused neurological deficiency, neck stiffness, confusion, drowsiness or stupor, disorientation, tremors, seizures and paralysis, as these are symptoms of Eastern equine encephalomyelitis that can cause significant harm to humans.
What are the symptoms in horses?
Horses show signs of nervousness, and sometimes mortality. Other signs and symptoms in equines include:
- Elevated body temperature
- Decubitus, i.e. the animal lies horizontally on the ground
Diagnosis, Treatment, and Prevention of Equine Encephalomyelitis
Eastern, Western, and Venezuelan equine encephalitis is usually diagnosed by a clinical study of blood serum in both humans and horses. Currently, there is no specific treatment for equine encephalomyelitis, but support is provided to sustain vital functions.
The main measure to prevent the disease in humans is to use repellents and prevent the proliferation of mosquitoes. In the case of equine owners, they are recommended to consult with their veterinarian for a vaccination plan and to consult a specialist in case of equines that present symptoms.
Argentine health authorities recommend vaccinating horses as a preventive measure before moving or moving, as well as using repellents and keeping their pens clean to avoid mosquitoes that can infect them. In case a horse presents symptoms of equine encephalomyelitis, it is important that it is seen by a veterinarian as soon as possible.
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