Johns Hopkins Working Group on Civilian Biodefense Warns Tularemia--Rabbit Fever--Could Be Bioweapons Threat

The Working Group on Civilian Biodefense, an expert panel convened by the Center for Civilian Biodefense Studies at the Johns Hopkins Bloomberg School of Public Health, says that the highly infectious disease tularemia -- also known as rabbit fever --could pose serious consequences if used as a biological weapon.

In underscoring the importance of this issue, the report cites a World Health Organization study which projected estimates of 250,000 illnesses and 19,000 deaths in the event that a mass-casualty tularemia biological weapon were used against a modern city of 5 million people. In this latest report, the Hopkins Working Group recommends medical and public health guidelines and policies to minimize the consequences from an attack. The report is published in the June 6, issue of the Journal of the American Medical Association (JAMA).

"This report highlights the need to address the nation’s preparedness and response to possible bioweapon-induced epidemics," says the report's lead author, David T. Dennis, MD, MPH, a member of the Hopkins Working Group and a senior researcher with the Division of Vector-Borne Infectious Diseases at the Centers for Disease Control (CDC).

According to the report, a tularemia-based bioweapon would trigger cases of pneumonia, pleuritis, and lymph node disease within three to five days after exposure. Unless treated with effective antibiotics, the disease could lead to serious illness including possible respiratory failure, shock, or death.

"Diagnostic testing capabilities are available for tularemia, but they are not widely available. Effective antibiotic treatment regimens also exist for tularemia, but they are not the antibiotics clinicians would likely prescribe for routine treatment of pneumonia. Given the rarity of tularemia and the non-specific features of the disease, clinicians are not likely to order the needed diagnostic test, nor begin the proper antibiotics until some time into an epidemic," explains Dr. Dennis.

Tularemia is caused by exposure to the Francisella tularensis bacterium, which affects both animals and people. It is sometimes called "rabbit fever" because it often infects hunters and trappers who are exposed to contaminated animals or meat. It can also be spread to humans by tick or insect bites, inhaling infected dust, or eating or drinking contaminated materials, but it not spread from person to person. Rabbits, voles, squirrels, and other small animals are natural hosts for the disease. Tularemia occurs rarely in the United States. Last summer, an outbreak of tularemia pneumonia occurred in Martha's Vineyard, Mass. Cases of the disease were associated with infected dust from lawn mowing and other landscaping activities, activities that presumably can stir up contaminated dust. Outbreaks are common in Europe and Russia.

"One of the priorities that emerges from this analysis includes the need to develop simple, widely available, rapid diagnostic tests that could be used to identify persons infected with F. tularensis. We also need a better understanding of how effective new classes of antibiotics would be in treating this old scourge of tularemia," says Thomas Inglesby, MD, one of the report's authors and a researcher with the Center for Civilian Biodefense Studies at the Johns Hopkins Bloomberg School of Public Health.

In addition, the Hopkins Working Group report recommends the development of testing that can rapidly identify the antibiotic susceptibility of tularemia strains, allowing public health officials to make the most effective and timely interventions. The possibility that genetically induced antibiotic-resistant strains could be used as weapons has made this even more important, not only for tularemia, but for other potential weapons as well.

A tularemia vaccine is not currently available for general use, and it is only recommended for laboratory workers who are routine exposed to the disease. The Hopkins Working Group encourages the development of new DNA-based or antibody-based vaccines that could provide fast acting protection from tularemia both before and after exposure.

Over the past two years, the Working Group for Civilian Biodefense has published recommendations in JAMA for responding to potential terrorist use of smallpox, anthrax, plague, and botulism bioweapons. Further reports are anticipated.

The study was funded by the Center for Civilian Biodefense Studies at the Johns Hopkins Bloomberg School of Public Health.