[Equine influenza outbreaks with viral antigenic drift in Berlin 1988-1991].

This research explores three occurrences of equine influenza in Berlin between 1988 and 1991, revealing varying symptoms from the typical influenza, extreme neutropenia, lymphocytosis, and unchanged monocyte levels. Despite regular vaccination, several horses fell ill, believed to be due to the high antigenic drift of the influenza virus.

Outbreaks and Clinical Symptoms

• The paper begins by discussing three outbreaks of equine influenza in Berlin (Germany) in the years 1988, 1989, and 1991. Details are provided about the clinical symptoms, hematological and virological aspects, and several epizootiological (epidemiology in animals) aspects.
• Interesting deviations from the typical pattern are reported. Many horses didn’t exhibit common flu symptoms such as cough or fever. However, when a cough was present, it was moist in nature, diverging from a typical dry cough associated with influenza.
• In many cases, a mucous nasal discharge lasting 4-5 days was reported. It’s a clear indication of the respiratory issue caused by the influenza virus.

Hematological Findings

• Hematologically, extreme neutropenia (a decrease in neutrophils, a type of white blood cell) was observed. This data suggests that the virus severely affected the horses’ immune system.
• Lymphocytosis (increase in lymphocytes, another type of white blood cell) was also noted. The increase may indicate the body’s response to viral infection, as lymphocytes are integral to the immune system’s defense mechanism.
• The level of monocytes (a type of white blood cell that can morph into macrophages to combat infections) remained generally unchanged, indicating a complex immune response that needs further studies for comprehension.

Ineffectiveness of Vaccinations

• Despite regularly being vaccinated against equine influenza, some horses fell ill, indicating an inefficiency in the vaccines used.
• The researchers surmise that this may be due to a significant antigenic drift in the influenza virus compared to the strains used in existing vaccines. Antigenic drift is a natural process whereby the virus mutates over time, creating new strains that can evade immunity developed from past vaccination or infection.
• However, this research does not pinpoint the origin of the new strains causing these influenza outbreaks, but it raises questions about the potency and adaptability of existing vaccination programs.