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Tularemia (francisella tularensis), also known as rabbit fever, deerfly fever and Ohara's disease, like the plague is a bacterial infection that can occur naturally from the bite of insects, usually ticks and deerflies. The disease can also be acquired through contact with infected rabbits, muskrats and squirrels, ingestion of contaminated food or inhalation of contaminated dust. Once contracted, is not directly spread from human to human.
Tularemia remains infectious in the blood for about two weeks and in lesions for a month. The disease can occur at any time of the year, but is most common in the early winter during rabbit-hunting season and in the summer when tick and deerfly activity is at its peak. Tularemia contracted naturally has a death rate of approximately 5%. The pneumonic form, which might be precipitated by a terrorist attack, would have a much higher death rate of 30% or greater.
Tularemia can appear in several different forms in humans, depending on the route of exposure. The usual presentation are ulceroglandular, typhoidal or septicemic. In humans as few as 10 to 50 organisms can cause disease if inhaled or injected, but over 108 would be required for the disease if ingested.
Ulceroglandular tularemia is acquired naturally from dermal or mucous membrane exposures of blood or tissue fluids of infected animals. The typhoidal form makes up 5% to 15% of naturally occurring cases, which result from inhalation of infectious aerosols. Pneumonia can result from any of the forms of tularemia but is most prominent in typhoidal. Incubation periods range from two to 10 days, depending on the dose and route of exposure.
Symptoms of ulceroglandular disease include lymphadenopathy, fever, chills, headache and malaise. About 90% to 95% of patients may present cutaneous ulcers. When ulcers are absent, it is referred to as glandular tularemia. When symptoms are confined to the throat, it is called primary ulceroglandular disease. Oculoglandular tularemia results from contact to the eyes from an infected fluid or blood. Typhoidal or septicemic tularemia produces fever, prostration and weight loss, without adenopathy (any disease of a gland, especially a lymphatic gland).
Diagnosis of primary typhoidal tularemia is difficult because the symptoms are very non-specific. After exposure, the usual treatment is two weeks of tetracycline. Streptomycin is given for more severe exposures. Aminoglycosides, genatamycin, kanamycin and chloramphenicol are also effective antibiotics. Tularemia survives outside the host in carcasses and organs up to 133 days, in grain dust and bedbugs for 136 days, in rabbit meat for 31 days, in straw for 192 days, and in water for up to 90 days. A vaccine is under development and has been successful during tests on more than 5,000 people, without significant adverse reactions.
Q-Fever (Coxiella burnetii), also known as Query Fever, is a bacterial disease that occurs naturally in sheep, cattle and goats. It is present in very high concentrations in the placental tissues of these animals. Coxiella burnetii is the bacterial agent that causes Q-Fever.
Incidence of the disease is worldwide and it is likely that more cases occur than those reported. Many epidemics occur in stockyards, meat-packing plants and medical labs that use sheep in research.
Transmission occurs from airborne dissemination of rickettsiae in dust from contaminated premises. Organisms can be carried in the air over a half-mile downwind. Infections also occur from contact with infected animals, their birth products (especially sheep), wool from sheep, straw, fertilizer and laundry of exposed persons. The disease has also been traced to unpasteurized milk from cows. Transmission from human to human is very rare.
Several varieties of ticks may also carry the disease and transmit it from animal to animal. Mortality rates from this disease are very low, from 1% to 3%, though it is an incapacitating agent because it is highly infectious when delivered through inhalation. As little as one organism can cause clinical symptoms. The usual infectious dose is considered to be 10 organisms through inhalation.
Symptoms are not specific to the disease and may be mistaken for symptoms of a viral illness or atypical pneumonia. The incubation period is 10 to 20 days. Patients may experience fever, cough and chest pain as soon as 10 days after exposure. Although rare, other symptoms that may appear include chills, headache, weakness, malaise, severe sweats, hepatitis, endocarditis, pericarditis, pneumonitis and generalized infections.