Influenza is an extremely contagious respiratory disease, which predominantly affects the upper respiratory tract. There are four types of influenza virus, and pigs and chickens are considered two key reservoirs of this virus. Equine influenza (EI) virus was first identified in horses in 1956, in Prague. The influenza A viruses responsible for EI are H7N7 and H3N8. Outbreaks of EI are characterized by their visible and rapid spread, and it has been possible to isolate and characterize H3N8 outbreaks in several countries. The clinical diagnosis of this disease is based on the clinical signs presented by the infected animals, which can be confirmed by performing complementary diagnostic tests. In the diagnosis of EI, in the field, rapid antigen detection tests can be used for a first approach. Treatment is based on the management of the disease and rest for the animal. Regarding the prognosis, it will depend on several factors, such as the animal's vaccination status. One of the important points in this disease is its prevention, which can be done through vaccination. In addition to decreasing the severity of clinical signs and morbidity during outbreaks, vaccination ensures immunity for the animals, reducing the economic impact of this disease.

Equine Influenza (EI) is a disease caused by the genus A influenza virus, with a global distribution and under constant review. Equine Influenza is highly contagious and affects the respiratory tract. Vaccination in horses is an adequate prevention method, however some strains have the capacity to infect immunized horses, due to the mutagenic changes that the virus undergoes. This work aimed to study the Veterinary Medicine performance regarding Equine Influenza in Portugal in the years 2018 and 2019, and to compare the clinical practice in Portugal with that of other European countries. The study was based on the responses to a questionnaire consisting of nine questions on: 1) Geographical area of clinical practice; 2) Activity of equines assessed; 3) Number of suspected cases of Equine Influenza in the last two years; 4) Number of cases of Equine Influenza diagnosed with the support of laboratory tests in the last two years; 5) Number of vaccinations against Equine Influenza in the year 2018; 6) Number of vaccinations against Equine Influenza in the year 2019; 7) Whether the vaccination protocol used follows FEI/FEP standards; 8) Whether the vaccination protocol is annual or biannual; and 9) Use of laboratory tests for Equine Influenza in the last two years. The surveys were circulated online in Portugal and in Germany, France, Ireland, Italy, the Netherlands, the United Kingdom and Sweden for anonymous reply. In Portugal, 50 responses to the survey were obtained. Veterinarians reported suspected cases. Only four cases were confirmed using laboratory tests. 22 professionals applied more than 100 vaccines against Equine Influenza in the year 2018, and a decrease was observed in the year 2019. The Veterinarians did not reveal a preference for biannual or annual vaccination. Most professionals (94%) did not use laboratory tests to confirm the suspected infection. In Portugal it was possible to identify an opportunity to improve the clinical practice of Veterinarians in the use of laboratory tests for disease diagnosis and vaccination. The decree law that establishes the compulsorily notifiable diseases does not match the list of the World Organisation for Animal Health (OIE) and therefore the General Directorate of Food and Veterinary (DGAV) does not have the data needed to properly notify the disease. Equine Influenza needs greater attention in Portugal and there are a number of measures that can be adopted to improve disease management in the country.