Francisella tularensis – Infection, Transmission & Diseases

Francisella tularensis

Francisella tularensis is the causative agent of the infectious disease tularemia . The pathogen is a rod-shaped bacterium from the Pasteurellacae family.

What is Francisella tularensis?

The bacterium Francisella tularensis is a gram-negative pathogen. In contrast to gram-positive bacteria, gram-negative bacteria have an outer cell membrane in addition to the thin peptidoglycan layer made of murein. The pathogen Francisella tularensis is pleomorphic. Pleomorphic bacteria are multifaceted. They change their cell shape depending on the environmental conditions. Their appearance also depends on the stage of development.

Francisella tularensis belongs to the coccoid rod-shaped bacteria. Rod bacteria are actually elongated, while the coccoid rod bacteria are somewhat rounded. There are four different subtypes of the pathogen. However, the three clinically significant forms are identical in serology. Two groups of Francisella tularensis can be distinguished biochemically and genotypically. The Jellison type A bacterium Francisella tularensis biovar tularensis is highly virulent and causes severe disease progression, which is often fatal. The bacterium Francisella tularensis biovar holarctica of Jellison type B is less virulent. But this bacterium can also cause severediseasescause.

Occurrence, Distribution & Properties

Francisella tularensis is native to Scandinavia, Russia, China, Japan, USA and Canada. Francisella tularensis biovar tularensis type A is mainly distributed in North America. Francisella tularensis biovar palaearctica occurs worldwide. Pathogen reservoirs are rabbits, rats, squirrels, mice and rabbits. But the pathogen can also be found in the soil and in the water. The small mammals become infected either through contact with contaminated water or soil material or through blood-sucking parasites such as flies, ticks or mosquitoes.

The bacterium is transmitted to humans through mucous membrane or skin contact with contaminated animal material. The consumption of insufficiently heated, infectious meat is also a possible source of infection. In particular, the consumption of rabbit meat has proven to be a possible route of infection. Inhaling contaminated dust (e.g. from hay, straw or earth) can also lead to infection. The same applies to contact with infected mosquitoes, ticks or flies.

The infection cannot be transmitted from person to person. However, when handling pathogens or inhaling aerosols containing pathogens, people can become infected in the laboratory. However, the rural population is more frequently affected by an infection with Francisella tularensis. Infection occurs here mostly through the processing of game meat or other agricultural products.

The pathogen Francisella tularensis is highly contagious. This means that even smaller amounts of pathogens are sufficient to trigger an infection. The incubation period is three to five days. Depending on the infection dose, route of infection and pathogen virulence, the incubation period can also be up to three weeks.

Diseases & Ailments

Tularemia is a reportable zoonosis . Although the disease is rather rare, it is often severe and life-threatening. A distinction can be made between an external (localized) and an internal (invasive) form.

The external ulceroglandular form is the most common form of tularemia. It begins very suddenly with a sharp rise in fever. Ulcers form at the entry point of the pathogen . The local lymph nodes are inflamed with pus. In oculoglandular tularemia, also known as parinaudal conjunctivitis, the entry point of the pathogen is on the conjunctiva of the eye . It can be recognized as a yellow node. In the eye, the pathogen causes a painful inflammation of the conjunctiva ( conjunctivitis ). The lymph nodes in the neck and in front of the ear are swollen.

No portal of entry can be identified in glandular tularemia. Ulcers do not form either. Only the regional lymph nodes are swollen and painful. Glandulopharyngeal tularemia is found primarily in children. This is where ulcers form in the mouth and throat . The lymph nodes in the angle of the jaw are swollen.

When the pathogens are inhaled or get to the internal organs through the bloodstream , the internal or invasive form of the disease develops. Typhoid tularemia occurs primarily during slaughter or laboratory work. The lungs and airways are often affected. The patients have a high fever and suffer from headaches and sweating . A feared complication of typhoid tularemia is lung abscess . In addition, the meninges ( meningitis ) can become inflamed. Also inflammation of the mediastinitis ( mediastinitis ) or the pericardium ( pericarditis ).) are possible. Other complications are rhabdomyolysis and osteomyelitis . Typhoid tularemia is also known as septic or generalized tularemia. It is very dangerous and is associated with a high mortality rate.

Intestinal tularemia is thought to develop from eating contaminated meat that has been undercooked. Typical symptoms are vomiting , nausea , sore throat , diarrhea and abdominal pain .

The second most common form of tularemia is pulmonary tularemia. It manifests itself in the form of pneumonia . Patients have cough with sputum , shortness of breath and chest pain. Abdominal tularemia shows a typhoid-like clinical picture. Liver and spleen are swollen. Patients suffer from diarrhea and abdominal pain.

Tularemia is treated with antibiotics . Streptomycin in particular has proven to be effective. There is resistance to penicillin and sulfonamides . Even with antibiotic treatment, five percent of all invasive forms are fatal. Without treatment, mortality is over 30 percent. The lethality of the American forms of tularemia is significantly higher than that of the European strains of Francisella tularensis.

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Hello! I am Lisa Newlon, and I am a medical writer and researcher with over 10 years of experience in the healthcare industry. I have a Master’s degree in Medicine, and my deep understanding of medical terminology, practices, and procedures has made me a trusted source of information in the medical world.