Infectious Diseases

Highly contagious viral airway disease caused by the equine influenza virus (orthomyxovirus, type A). It spreads rapidly by droplets and typically causes sudden fever and a dry cough; with an uncomplicated course healthy horses usually recover, but premature exertion can prolong the illness.

EHV-1 and EHV-4 are widespread, highly contagious herpesviruses of the horse. EHV-4 mainly causes airway infections, EHV-1 additionally abortion (viral abortion) and the feared neurological form (equine herpesvirus myeloencephalopathy, EHM). Once infected, horses carry the virus latently and can reactivate it under stress.

Strangles is a highly contagious bacterial infection of the upper airways and lymph nodes caused by Streptococcus equi subsp. equi. Typical are fever, purulent nasal discharge and painfully swollen, often abscessing throat lymph nodes. Most horses recover, but some become inconspicuous long-term shedders that carry the pathogen onward.

Tetanus is a life-threatening disease caused by the soil bacterium Clostridium tetani. Spores enter the body through the smallest wounds, and their toxin makes the muscles cramp. Horses are especially sensitive and the course is often fatal — vaccination (primary immunisation and booster) is the decisive protection.

Equine Lyme borreliosis is transmitted by ticks via bacteria of the Borrelia burgdorferi complex. Many horses carry antibodies without ever falling ill — attributing symptoms to an active borreliosis is diagnostically demanding and professionally disputed. The clinical picture is considered non-specific and is classified neutrally and cautiously.

West Nile virus (WNV) is a mosquito-borne virus that can cause inflammation of the brain and spinal cord in horses. Most infected horses show no symptoms; if a horse becomes neurologically ill, however, the course is serious and a substantial proportion die or must be euthanised. A vaccine is available.