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The etiological agent of Tularemia is a potential weapon of bioterrorism that could infect more than 80% of the global population. Get detailed information about this condition, including its causes, symptoms, diagnosis and treatment.
It is an acute bacterial disorder of rabbits transmissible to humans. The ailment is named after Tulare County in California.
The infectious condition is also known by other names like:
Picture 1 – Tularemia
- Pahvant Valley plague
- Rabbit fever
- Deer fly fever
- Ohara's fever
Based on the presenting manifestations, the disorder can be classified into the following types:
- Ulceroglandular tularemia
- Glandular tularemia
- Oropharyngeal tularemia
- Pneumonic tularemia
- Oculoglandular tularemia
- Typhoidal tularemia
Approximately 200 cases of the disorder in humans are reported annually in the south-central and western United States. It is even endemic in parts of Europe and Asia. Recently, its incidence has eventually dropped to one per million individuals per year in the United States.
The incubation period of the disorder is normally 1 to 14 days, but the symptoms may appear 3 to 5 days after exposure to the infectious agent. Some of the common signs and symptoms observed in patients include:
- Joint pain
- Muscle stiffness
- Sudden weight loss
- Shortness of breath
Ulceroglandular tularemia is typically characterized by red nodules or rash on the skin that gradually develops into painful sores called ulcers. The type is also associated with swollen lymph nodes, which eventually get filled with pus. However, the swelling of the lymph nodes is more apparent in the case of glandular tularemia. The oculoglandular disorder is marked by conjunctivitis, in which the infected eyes undergo painful swelling along with white discharge. Sore throat is usually seen in patients who suffer from the pharyngeal form of the disorder. The pneumonic condition is more serious as it involves the lungs. Typhoidal tularemia could cause serious symptoms such as:
- Enlarged spleen
- Liver abnormalities
- Renal disorders
The bacterium Francisella tularensis is primarily responsible for causing the infection. It is a parasitic organism that requires a host in the form of a higher living being for its survival. Several subspecies of the microorganism are present in rabbits, hares, beavers and muskrats. Humans normally get infected when the F. tularensis-carrying ticks and deer flies bite them. A variety of other arthropods and insects can also transmit the bacterial illness from an infected rabbit or any other rodent. Individuals who directly come into contact with the infected animals can also contract the disease. Hunters, landscape workers, foresters, farmers and veterinarians are more likely to get infected as their profession demands direct animal contact. Even minute cuts, scrapes or abrasions on the skin form the common routes of bacterial transmission. The eye usually gets infected when touched by contaminated hands, causing ocular tularemia. Skinning as well as handling of infected animals can readily transmit the disorder. Pneumonic tularemia occurs when dried disease-carrying animal materials are aerosolized and inhaled. While farming, mowing a yard, sheering sheep, or working on animals in laboratory, the bacteria can become airborne and attack the pulmonary organ. Individuals who frequently eat the meat of these animals are at a greater risk of acquiring the pharyngeal form of the infection. This happens when the meat is uncooked or undercooked, causing a host of gastrointestinal symptoms. Although the transmission of the disorder from domestic dogs and cats is rare, these animals can inadvertently pick up the bacteria on their claws after killing a wild rodent and pass it on to humans. In certain instances, the transmission has been known to occur from contaminated food and water.
In most cases, physicians are unable to suspect the possibility of the disorder, owing to the presence of influenza-like symptoms. A history of tick bites or an occupational exposure to rodents can provide some information to the healthcare providers who may order a few diagnostic tests and exams for further evidence. Some of these include:
The test checks for the presence of antibodies in the blood, another sign of a possible infection in the body. High quantities of the antibodies could however, indicate a remote disease rather than an acute infection.
Special incubators and growth media are used for the identification of bacteria. Because microorganisms may only be intermittently present in blood or urine, multiple cultures are taken before the result is considered negative.
Polymerase chain reaction (PCR) method can detect the microbial pathogens in small samples of blood, sputum or urine culture. The test enables discrimination of the pathogenic organisms from the non-pathogenic ones by analyzing some specific genes in the bacteria. Florescent stain tests are also available to study the various segments of the microorganism. The bacterial RNA can be analyzed with other experimental tests.
The signs and symptoms of this pneumonic condition can prompt physicians to conduct an X-ray of the chest. Patchy distribution in the lungs signifies a bacterial growth.
Antibacterial therapy is effective in treating the less severe forms of the condition. Among the various antibiotics, streptomycin is the most widely used drug. It is intramuscularly administered to the patients, twice a day, for 1 to 2 weeks. A 10 day course of intravenous or oral gentamicin is an alternate option for the infected patients. Oral treatment with doxycycline, fluoroquinolones, or chloramphenicol has shown less clinical effectiveness in the past with greater chances of recurrence. Individuals who are placed at a higher risk of contracting the infection are administered with an attenuated, live vaccine in order to induce immunity against the harmful bacteria. However, it should never be given post-bacterial attack.
Individuals must adopt certain measures in order to reduce the chances of encountering the virulent bacteria. These generally involve:
- Avoiding the use of contaminated water for different purposes
- Application of repellant to resist insect or arthropod bite
- Treating clothes with permethrin to repel the insects from sitting
- Wearing light-colored clothes with full sleeves along with long pants tucked into the shoes to spot any tick crawling
- Taking a bath after a long outdoor trip
- Using impervious gloves when handling animals
- Washing the hands thoroughly with soap water after handling live animals or carcasses
- Eliminating the bacteria in infected meat by following proper cooking techniques
- Regular checking of the pet’s body to detect any tick or fly
- Keeping the surroundings clean to prevent breeding of blood feeding-insects and arthropods
The negligence of patients to detect or treat the disorder in time can cause the infection to spread to other regions of the body, resulting in complications like:
Picture 2 – Tularemia Image
- Lung abscesses
The severity of Tularemia depends on the route of infection and the virulence of the causative bacterial strain. A great degree of protection must be taken in a high-risk situation. Preventive antibiotics are efficacious and appear promising for the treatment of the condition provided it is diagnosed at an early stage.