Pasteurella are parasitic pathogens of the Brucella family. Preferentially, the bacteria infect livestock but can be transmitted to humans. The rod-shaped bacterium Pasteurella pestis is considered the causative agent of bubonic and pneumonic plague.
What are pasteurella?
Parasites infest other living things and feed on the host organisms or use them for reproductive purposes. Most parasites do not kill their host organisms because they themselves depend on the host for survival. However, parasites can harm hosts, impair their organ functions, destroy cells, or cause nutrient deficiencies. One of these parasites is the parasitic pathogen Pasteurella. The pathogen belongs to the Brucella family. The genus encompasses various gram-negative rod-shaped bacteria that are found particularly in the urogenital tract of farm animals such as cattle, pigs and sheep. For humans, the parasites are only rarely associated with serious hazards. Brucella pasteurella are nevertheless classified as human pathogens and are consequently associated with disease value for humans. Infections with Brucella are notifiable throughout Germany. In rare cases, an infection can cause brucellosis in humans. The best-known species of Pasteurella include Pasteurella multocida, pestis, pseudotuberculosis, tularensis, stomatis, and canis.
Occurrence, distribution, and characteristics
Pasteurella are rod-shaped bacteria and divide by fission. They do not contain a nucleus and are not equipped with organelles. Most species of Pasteurella are aerobic, meaning that the depend on oxygen for survival. The metabolism of aerobic pathogens requires oxygen molecules to generate the necessary metabolites. The opposite of the aerobic metabolic pathway is the anaerobic metabolic pathway, in which the organism relies on other forms of molecules to generate metabolic products. Some species of Pasteurella are facultatively anaerobic. This means that they can survive without oxygen in an emergency. The bacteria are asporogenic, so they do not form spores. The principle of zoonosis also applies to the bacterial species. The pathogens can therefore be transmitted from animals to humans and from humans to animals. The rod-shaped bacteria preferentially infect farm animals such as cattle, sheep or pigs. Transmission usually occurs through contact. In the case of transmission to humans, bite transmission should be emphasized. The bacteria enter the human body via the bite site. Pasteurella are consequently associated with a special form of zoonosis: the so-called zooanthroponosis. This type of zoonosis is spoken of in animal diseases that are transmissible to humans. The opposite is anthropozoonosis: a human disease that can be transmitted to animals. Contact with Pasteurella can cause disease in humans. Detection via the bacteria is pathogenic in the human body because the bacterium is not part of the normal bacterial population in the human organism. Normally, the human immune system fights the parasitic pathogen after contact, even before it can multiply. Thus, Pasteurella does not necessarily lead to disease. Within an organism, the rod-shaped parasites spread by migrating via the bloodstream to the individual organs and in this way colonize the entire body. Like all Brucella, the bacteria are unencapsulated. They stand in isolated or paired arrangements and are immobile. Reactions to Pasteurella range from local skin reactions to more serious infections such as brucellosis. Pasteurella pestis is a special case. This is the plague bacterium that survives for months in feces, sputum (cough mucus), or pus and multiplies intracellularly and extracellularly in the body. Most commonly, this species of the bacterium infects rodents. Transmission occurs through parasites such as ticks or fleas, which ingest the bacteria when they feed on rodents. However, infections are also possible through direct contact with infested rodents.
Diseases and complaints
Four different serotypes have been described with respect to the parasitic pathogen Pasteurella. Infection causes species-specific symptoms. That is, the pathogen manifests in different ways in livestock and in humans. In wild and domestic animals, Pasteurella causes hemorrhagic septicemia.This is a blood poisoning that is equivalent to a systemic inflammatory reaction of the entire organism. In humans, contact with Pasteurella usually causes only local reactions, which occur preferentially at the bite sites. In most cases, these are skin reactions such as redness and swelling. In the case of Pasteurella pestis, infection can result in bubonic plague or pneumonic plague. Bubonic plague begins with uncharacteristic symptoms such as nausea, fever, diarrhea, dizziness, and headache. The lymph nodes swell and cause plague bumps. If left untreated, sepsis occurs after a period of time and is fatal in most cases. Pneumonic plague, in turn, often arises from bubonic plague and is highly infectious with a particular risk of spread in cold, humid air. Mortality from pneumonic plague is significantly higher than from bubonic plague. Today, however, plague can be treated very well if diagnosed early. Brucellosis caused by Pasteurella is also a serious disease. Typical symptoms of such an infection are, in addition to fatigue or exhaustion, weight loss, more or less severe night sweats, joint pain and muscle aches, as well as concentration problems. These symptoms may be associated with nosebleeds, petechial haemorrhages, non-productive cough or constipation. Abdominal pain, hepatosplenomegaly, or lymphadenitis may also be symptomatic. Antibiotics play a major role in the therapy of all of the above conditions.
