- Francisella tularensis outcomes tularaemia in man and sure small mammals, similar to rabbits, hares, beavers and several other rodent species.
- Tularaemia was initially described in Tulare county, California.
- It may be transmitted by direct contact, by biting flies, mosquitoes and ticks, by contaminated water or meat or aerosols.
- Francisella tularensis can also be know as Pasteurella tularensis or Brucella tulerensis)
Morphology of Francisella tularensis:
- It’s a very small, nonmotile, nonsporing, capsulate, gram-negative coccobacillus, about 0.3 to 0.7 μm × 0.2 μm in measurement.
- In tradition it tends to be pleomorphic to and bigger, even filamentous, types are current.
- It stains poorly with methylene blue however dilute carbol fuchsin (10%) produces attribute bipolar staining.
Cultural Traits of Francisella tularensis:
- F. tularensis is strictly cardio.
- It is not going to develop on odd nutrient media however grows properly on blood agar containing 2.5 p.c glucose and 0.1 p.c cysteine hydrochloride.
- Minute droplet-like colonies develop in 72 hours.
Biochemical traits of Francisella tularensis:
- Underneath appropriate situations acid is shaped from glucose and maltose. Indole and urease exams are adverse.
- Two biovars are acknowledged. Strains of F. tularensis have been subdivided into biotypes based mostly on their virulence and epidemiological behaviour.
- Extremely virulent strains are discovered solely in N. America, whereas strains of low virulence are seen in Europe and Asia additionally.
Pathogenesis of Francisella tularensis:
- The an infection, which is a typical zoonosis, is especially unfold by bugs or ticks amongst lagomorphs and rodents.
- It’s transmitted to man by means of dealing with of contaminated animals, e.g. rabbits or hares tick, mosquito or fly bites, inhalation of contaminated mud, ingestion of contaminated water or meat.
- Laboratory staff are at greater danger whereas dealing with contaminated laboratory animals or cultures of the organism.
- Man to man transmission of an infection apparently doesn’t happen.
- In human beings, tularemia could current as a neighborhood ulceration with lymphadenitis, a typhoid like fever with glandular enlargement or an influenza like respiratory an infection.
- The severity of illness is far better with sort A strains and case fatality charges could exceed 5 p.c.
- Illness attributable to sort B strains is far much less extreme, with very low mortality.
Laboratory Analysis of Francisella tularensis :
- F. tularensis is extraordinarily harmful to deal with within the laboratory and Class 3 containment is required for all manipulations and animal work.
- Analysis could also be made by tradition or by inoculation into guinea pigs or mice. A PCR has been described, however shouldn’t be extensively accessible.
- Serology is most probably to be constructive after 3 weeks.
- Rising titres of agglutinins to F. tularensis or particular person titres of 160 are diagnostic.
- Serum from instances of F. tularensis could cross-react with brucellosis and vice versa, normally to comparatively low titre.
- An intradermal delayed hypersensitivity check has been used prior to now however the antigen shouldn’t be available.
Therapy of Francisella tularensis:
- Streptomycin or gentamicin are the antibiotics of selection in tularaemia and are normally healing.
- A vaccine based mostly on the live-attenuated LVS pressure confers some safety.
- It may be administered by scarification to individuals who’re topic to excessive danger of an infection.
- F. tularensis has been developed as a organic warfare agent and has potential software in bioterrorism.