Tularemia - a Biological Weapon?
 
 


Tularemia: a Biological Weapon?

 

 

Tularemia as a Biological Weapon:

 

In field investigations, the appropriate agencies are always concerned about the potential mortality rate of any given pathogen.  In the case of tularemia, a disease typically transmitted by small mammals, the field study has become two-fold as Francisella tularensis, Pasteurella tularensis, has been under investigation as a potential biohazard that can be used in the new era of biological terrorism or biological warfare.

 

A study of database information from 1966 to 2000 has determined that a weapon using airborne tularemia could result in an outbreak of acute, undifferentiated febrile illness with initial stages of pneumonia and pleuritis beginning to develop within three to five days. Because of this, epidemiological, clinical and microbiological findings of any suspected outbreak should be investigated as a possible intentional infection and health officials should be alerted.

 

I know of no other infection of animals communicable to man that can be acquired from sources so numerous and so diverse. In short, one can but feel that the status of tularemia, both as a disease in nature and of man, is one of potentiality.  R.R. Parker

 

Tularemia is a bacterial zoonosis, and is caused by Francisella tularensis, and is considered to be one of the most infectious pathogenic bacteria known, as it only requires inoculation or inhalation of only ten organisms in order to cause disease. Humans can be come infected through a variety of environmental exposures and can develop a severe illness that can be fatal.  It is not transmitted human to human. As a result, it is considered to be a dangerous potential biological weapon because of its extreme contagion, ease of being spread, and its ability to cause illness and death.

 

History and Potential as a Biological Weapon:

 

Tularemia was initially described as a plague-like illness of rodents in 1911 and was subsequently discovered to be a potentially severe and fatal illness among the human population.  This agent's potential to cause an epidemic became evident during the 1930s and 1940s when large waterborne outbreaks occurred in the Russia and in Europe, with some cases showing up in the United States as well. Public health officials were concerned and immediately launched field and laboratory investigations into tularemia's microbiology, ecology, pathogenicity, and prevention.

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F. Tularensis has been considered to be a potential biological weapon as it was one of the agents that was studied in Manchuria from 1932 to 1945 and was also studied for military purposes in the West.  A former Soviet Union weapons scientist suspected that tularemia outbreaks on the Soviet and German eastern front during World War II might have been intentional.  During the 1950s and 1960s, the United States military actually developed weapons that could disseminate/distribute tularemia aerosols.  At the same time, they also worked to understand the "pathophysiology" of the disease and developed vaccines and antibiotics/treatments for those infected.
 

This biological weapons development was discontinued and all the biological arsenal was destroyed by 1973.  Since that time, the U.S. Army Medical Research Institute of Infectious Diseases has continued research on F. tularensis in order to better protect the military and civilians of this country. They have established protocols on decontamination, prophylaxis, clinical recognition, laboratory diagnosis and medical management.  It was established that it would cost the U.S. over five billion dollars for every 100,000 people infected with this disease.  Such a cost would have a debilitating effect on this country.

 

Epidemiology:

 

Tularemia has been found through most of North America, Europe, and Asia.  In the United States, cases have been reported in every state except Hawaii. It is predominantly a rural disease, but has been known to show up in urban areas as well. The natural reservoirs of infection are small mammals, including mice, water rats, squirrels and rabbits. They become infected through bites of ticks, flies, mosquitoes and exposure to contaminated environments. Contaminated hay, water, infected dead animal bodies, chronically infected animals and aerosol particles have been shown to be infective.  F. tularensis is considered to be one of the most infectious bacteria known and will cause severe illness and death in humans.

Humans become infected through insect bites, handling infected animals (tissue or fluids), or ingestion of contaminated water, soil, food, or by inhaling infected aerosols.  All ages and sexes are susceptible to tularemia.  Some activities make some individuals more prone to exposure such as hunting, farming, or anything that will expose an individual to wild animals. Laboratory workers are also susceptible to infection through accidental inoculation or inhalation of an aerosol.  Person to person transmission has not been documented.

Clinical Presentation:

The symptoms of tularemia are not immediately diagnostic.  The incubation period is anywhere from two to ten days. The disease can present in multiple ways. Usually patients present with several systemic or body-wide symptoms such as fever, skin lesions, and swollen lymph nodes. Sometimes the patients present with GI symptoms such as pain and diarrhea.  Sometimes a pneumonia-like illness can present, and this can sometimes delay diagnosis.

The onset of the disease is sudden, with a fever, headache, chills, low back aches, nasal congestion, and sore throat. Progressive weakness, malaise, inability to eat, and weight loss are characteristics of a continuing illness. Fortunately, tularemia responds well to antibiotics, which have reduced the mortality rate which used to be as high as 60%.
 

Diagnosis:

Because tularemia occurs in humans so infrequently, it is frequently misdiagnoses upon first presentation to medical personnel. Usually the first indication that it is tularemia is when public health officials begin to see clusters of acute, severe respiratory illnesses such as atypical pneumonia, pleuritis, and swollen lymph nodes. These patients will present with unusual epidemiological features.

Once tularemia is suspected, local and state health officials must be notified in order to launch an immediate field and epidemiological investigation. If F. tularensis cannot be ruled out and a bioterrorist event is suspected the state public health laboratory director and state public health department epidemiologist must be notified.  If necessary, the FBI will be notified.

Vaccination:

Beginning in the 1930s, live vaccine was used to immunize millions of people in the Soviet Untion.  Here in the United States, a vaccine was derived for laboratory workers who routinely work with F. tularensis. Immunity is achieved within about two weeks following either natural infection or through vaccination.

Environmental Control:

Avoid contact with sick or dead animals and the use of insect repellant when outside in a potentially dangerous area. If contamination occurs, a 10% bleach solution followed by a 70% alcohol solution can be used. Individuals who have been exposed should wash well with soap and water and clothing washed with soap and water as well. Municipal water supplies are protected with standard chlorine levels protecting against a waterborne infection.

Recent Outbreaks/Scares:

2000: During the summer, a tularemia outbreak occurred in Martha's Vineyard that left one person dead and brought the CDC in to investigate for possible F. tularensis aerosol exposures. Over the next few summers, Martha's Vineyard became known as the only place in the world where lawn mowing resulted in documented cases of tularemia.

 

1999 – 2000: Outbreak of tularemia in Kosovo.

 

2004: Accidental infection of F. tularensis occurred in three researchers at Boston University Medical Center because they failed to follow appropriate safety procedures.

 

2005: After the anti-war demonstration on September 24, 2005, small amounts of F. tularensis were found in the Mall area of Washington DC triggering off biohazard sensors at six locations surrounding the Mall.  No one has been reported to be infected from that incident.

 

2007: Again in Boston, this time at Boston University's Center for Advanced Biomedical Research where F. tularensis is kept for research purposes, smoke set off alarms.  It was later determined that it was only an electrical problem, no bacterial contamination could be found.