Snot – why is this epidemic so dangerous?

The disease is caused by a rod-shaped bacterium called Burkholderia mallei. The pathogen is transmitted through direct or indirect contact with infected horses. All bodily fluids are potentially infectious and can also be transmitted indirectly via bedding, feed, or water to the mucous membranes of the throat or intestines. Open wounds can also provide an entry point for the bacteria. After multiplying in nearby lymph nodes, the pathogen can spread through the blood or lymphatic system in the body, usually affecting the lungs first.

Outside the organism, the pathogen is not particularly stable and can be easily killed by light, dryness, or commercially available disinfectants. However, the bacteria can survive for several weeks in damp and dark environments. The pathogen primarily affects horses and donkeys, but other mammals and humans can also become infected. It is therefore referred to as a zoonosis. Due to its transmissibility to humans, its dangerousness, and its high infectivity, the pathogen is considered a biological weapon and may only be handled in laboratories with special safety measures.

Depending on the virulence (= disease-causing potential) of the pathogen, the infection can be acute, chronic, or latent (= without symptoms). Depending on the location of the changes, a distinction was previously made between skin, nasal, and lung rot. This classification is now considered outdated, as the different forms often merge into one another and sometimes occur in parallel.

After an incubation period (the time from infection to the onset of the disease) of 3 to 7 days, the first symptoms appear. In the acute form, which occurs mainly in donkeys and mules, the initial symptoms are rather unspecific, such as chills, high fever, nasal discharge, and reddening of the mucous membranes. These are accompanied by swelling of the lymph nodes and lymphatic vessels, abscesses, extensive purulent skin ulcers, bloody nasal discharge, purulent eye discharge, and difficulty swallowing. The acute form of glanders progresses very rapidly and usually leads to the death of the animal within a few days due to extensive necrosis (tissue death), pneumonia, and organ failure.

In chronic glanders, the initial symptoms are very often overlooked due to their significantly milder form. At the onset, horses usually only show recurrent fever, coughing, and breathing difficulties. The lymph nodes may be swollen and lumpy, but not painful. As the disease progresses, which can take years, a dull coat, emaciation and reduced performance can be observed. In addition, nasal discharge and nodular changes in the nasal mucosa (= nasal discharge) often occur. Skin changes are rare in the chronic form, but can occur in the form of nodular ulcers. In the area of the skin ulcers, the lymph nodes thicken and the lymph vessels harden, forming string-like, twisted structures under the skin that can also break open to the outside. Massive water retention and inflammation of the subcutaneous connective tissue can cause severe swelling of the hind legs, known as elephantiasis malleosa.

A latent infection only occurs in animals with a good immune status. The animal's own defenses and the pathogen are in balance, so that there are almost no symptoms. The infection lies dormant but can be reactivated at any time by a weakening of the immune system, allowing latently infected horses to excrete infectious pathogens again.

If there is reasonable suspicion of glanders, a veterinarian and the responsible official veterinarian must be notified immediately, as this is a notifiable disease. The veterinarian will conduct a thorough general examination and compile a detailed preliminary report. However, due to the diverse and largely unspecific symptoms, they will only be able to make a tentative diagnosis. To confirm this and rule out other diseases, further laboratory diagnostic tests are essential. The pathogen can be detected directly or indirectly using various methods.

Treatment of horses infected with glanders is prohibited in countries where the disease is considered eradicated. Infected animals must be killed and disposed of properly to prevent the disease from spreading further. Infected humans are treated with antibiotics, although the choice of medication is not always easy, as the pathogen is already resistant to a number of active ingredients.

The prognosis for acutely ill animals is poor, as they either die within a few days or have to be euthanized after diagnosis. In chronic and latent forms of the disease, it often goes undetected for years, allowing further animals to become infected and the disease to spread unrecognized.

Germany has been considered free of glanders since 1956. The German Animal Diseases Act stipulates that animals from countries where the disease is still prevalent may not be imported into Germany in order to prevent the pathogen from being reintroduced. In laboratories, work with the glanders pathogen may only be carried out under the strictest safety precautions. In exceptional cases, antibiotic treatment may be administered if human contact is suspected.