Scientists working on vaccine to fight potential bio-weapon

July 28th, 2008 - 5:51 pm ICT by IANS  

Washington, July 28 (IANS) Scientists are working on a vaccine to neutralise tularemia, a fatal disease caused by Francisella tularensis, a pathogen and a potential bio-warfare agent. Until recently, little was known about this bacterium. However, researchers have made rapid progress in understanding how it causes disease.

F. tularensis infection can cause a variety of symptoms, depending on the route of infection. For example, infection via an insect bite can lead to a swollen ulcer or fever, chills, malaise, headaches and a sore throat.

When infection occurs by eating contaminated food, symptoms can range from mild diarrhoea to an acute and fatal disease. If inhaled, F. tularensis infections can have a 30 percent mortality rate if left untreated.

“Only very few bacteria are needed to cause serious disease,” said researcher Petra Oyston. “Because of this and the fact that tularemia can be contracted by inhalation, Francisella tularensis has been designated a potential biological weapon.”

Since the events of September 2001 and the subsequent anthrax attacks in the US, concern about the potential misuse of dangerous pathogens including F. tularensis has increased.

As a result, more funding has been made available for research on these organisms and has accelerated progress on developing medical countermeasures.

Tularemia circulates in rodents and animals like rabbits and hares. Outbreaks in humans often happen at the same time as outbreaks in these animals.

The disease is probably transmitted by insects like mosquitoes, ticks and deer flies. People can also become infected by contact with contaminated food or water and by breathing in particles containing the bacteria. Farmers, hunters, walkers and forest workers are most at risk of contracting tularemia.

There is currently no vaccine against tularemia. Because there are few natural cases of tularemia, money was not spent on the development of a vaccine.

However, various nations developed F. tularensis as a biological weapon, including the reported production of antibiotic-resistant strains, so research into its pathogenesis has become a bio-defence issue.

“Progress is being made,” said Oyston. “Since the genome of F. tularensis was sequenced, researchers have taken great strides in understanding the molecular basis for its pathogenesis. This is essential information for developing a vaccine and getting it licensed.”

These findings will appear in the August issue of the Journal of Medical Microbiology.

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