Anthrax – also dangerous to humans

Anthrax is an acute, often fatal infectious disease that mainly affects cattle and sheep, but horses are also highly susceptible. The disease gets its name from the "burnt" appearance of the spleen in infected animals. Anthrax is found worldwide and is considered a zoonosis, as it is also dangerous to humans. It is a notifiable animal disease, but is now rarely observed in Germany. The anthrax bacterium is considered one of the most dangerous pathogens and could also be used by terrorists as a biological weapon.

INHALT
Cause, transmission, and development Symptoms Diagnosis Treatment Forecast Prophylaxis
Cause, transmission, and development

The pathogen that causes anthrax is the bacterium Bacillus anthracis. The actual infectious form is the spores produced by the pathogen, which are a permanent form of the bacterium. These spores are very resistant and can survive in the soil for many years. They are considered the most resistant permanent forms in the bacterial kingdom. Even decay, dryness, the tanning process, and leather preservation do not kill them.

For a long time, pasture soils were contaminated for years or decades by the excrement of animals infected with anthrax or by carcasses. Transmission occurs through feed or water contaminated with anthrax spores; there is no infection from animal to animal. In the animal or human organism, the spores transform back into reproducible pathogens, where they secrete highly potent toxins that destroy tissue through bleeding, severe inflammatory reactions, and edema (water retention).

Thanks to comprehensive official control measures and modern animal carcass disposal facilities, the disease has been virtually eradicated, at least in Germany. However, the disease still occurs regularly in the Middle East, so there is still a risk that the pathogen could be introduced through imports of animal raw materials such as hides, skins, hair, or wool.

Symptoms

After an incubation period (the time between infection and the onset of symptoms) of only one to two days, the first symptoms appear. Different courses of the disease have been described.

In horses, peracute forms of the disease can occur, in which the animals suddenly collapse and die before clinical symptoms appear, while working, in the stable, or even in the pasture.

The acute form is characterized by high fever, increased heart rate, labored breathing, pale blue mucous membranes, and colic with bloody diarrhea. The animals are initially highly agitated, then show depressive behavior, increasing weakness, unsteady gait, and muscle cramps. Death occurs within a few hours to several days due to suffocation.

During the subacute course, symptoms similar to those in the acute form occur, but there is intermittent improvement in the symptoms. Recurrent colic, only slightly elevated body temperature, and lower jaw edema (= water retention) may occur. The subacute course can last for months, and the affected horses may recover or ultimately die from colic.

Horses can also develop a local form of anthrax called cutaneous anthrax. This usually occurs after infection with the pathogen through blood-sucking insects, causing pus-filled boils and fluid accumulation in the skin and subcutaneous tissue. These so-called carbuncles are commonly found on the neck, chest, abdomen, and limbs.

Diagnosis

The veterinarian can and may only make a suspected diagnosis on a live animal, as taking samples is too dangerous due to the potential spread of the pathogen. The disease is a notifiable animal disease, which means that even a suspected infection must be reported immediately to the competent veterinary authority.

Since the blood of dead animals contains large quantities of the pathogen, which would immediately form spores on contact with the outside air, the carcasses must not be cut open on site under any circumstances. Due to the high risk of infection, tests to detect the pathogen are carried out exclusively in special high-security laboratories.

Treatment

As this is a notifiable animal disease, independent treatment attempts are prohibited. Once a suspected case of anthrax has been reported, the competent authority will initiate the control measures prescribed by the state. These may include the killing and safe disposal of sick and suspect animals.

Forecast

With the exception of cutaneous anthrax, the prognosis for anthrax infection is poor. Due to reporting requirements and legal regulations, sick or suspected animals must usually be killed anyway.

Prophylaxis

Thanks to legal regulations for combating anthrax, the disease has already been virtually eradicated in Germany. There is currently no approved vaccine for animals.

If an outbreak of anthrax occurs in a herd, the following preventive measures can help to prevent the pathogen from spreading further:

  • Quarantine of the herd until all prescribed disease prevention measures have been completed
  • Safe disposal of known sources of infection
  • Drainage and repeated plowing of contaminated pastures and meadows
  • Burning contaminated feed and bedding