Microbiology and Immunology

WORLD OF MICROBIOLOGY AND IMMUNOLOGY Tularemia

557

•

apy, which could be administered in either a hospital or home

environment. Over 90% of TB patients can be cured by a com-

bination of inexpensive antibiotics, but it is necessary they be

used for a period of at least six months.

The impact of tuberculosis was evident in the nineteenth

and early twentieth centuries in literature, art, and music.

Puccini’s opera, La Boheme,was created around the tragic

death of the tubercular heroine, Mimi. Since TB often attacked

the young, many poets, artists and musicians fell prey to the

disease before they had a chance to fulfill their creative work.

Among them, Amedeo Modigliani, John Keats, Frederic

Chopin, and Anton Chekhov were claimed by the disease,

along with millions of other young people during the period. In

the United States, American playwright Eugene O’Neill was

one of the fortunate few who did recover in a sanatorium and

went on to write his plays. His early play, The Straw,written in

1919, dramatically shows what life was like in a sanatorium.

In the past, U.S. city and state governments were

actively involved in regulations that controlled infected people

from spreading the infection. At present, federal, state, and

local agencies must again take a leading role in formulating a

public policy on this complicated health problem. Several

states are using a program called Directly Observed Therapy

(DOT) to combat the rising incidence of TB. This program has

met with considerable success in lowering reported cases of

TB as much as 15% in New York City during the late 1990s.

DOT is offered at soup kitchens, clinics, hospitals,

neighborhood health centers, and drug rehabilitation centers.

Outreach workers enable those with TB to get help with the

least amount of red tape. The wide array of medicines needed

to treat the disease are made available, and ample funding has

been provided from federal, state, and local agencies.

Apartments are located for homeless patients and special pro-

visions are made to help released prison inmates and those on

parole. Guidelines for compassionate, supervised medical

services are periodically reviewed for the successful imple-

mentation of the DOT program.

Despite such measures, the U.S. Department of Health

and Human Services predicts tuberculosis, will spread further

by the year 2005. In 1990, there were 7,537,000 TB cases

worldwide. That number is expected to rise to 11,875,000 in

2005, a 58% increase. Most of the rise in rate is attributed to

demographic factors (77%) while 23% accounts for the epi-

demiological factors, i.e., the rise in HIV infection.

Approximately 30 million people around the world will die of

TB from 2000 to 2009. These predictions are considered con-

servative because many cases of TB are never reported.

See alsoAIDS, recent advances in research and treatment;

Bacteria and bacterial infection; Epidemiology, tracking dis-

eases with technology; Public health, current issues

TTularemiaULAREMIA

Tularemia is a plague-like disease caused by the bacterium

Francisella tularensisthat can transferred to man from ani-

mals such as rodents, voles, mice, squirrels, and rabbits.

Reflecting the natural origin of the disease, tularemia is also

known as rabbit fever. Indeed, the rabbit is the most common

source of the disease. Transfer of the bacterium via contami-

nated water and vegetation is possible as well.

The disease can easily spread from the environmental

source to humans (although direct person-to-person contact

has not been documented). This contagiousness and the high

death rate among those who contract the disease made the bac-

terium an attractive bioweapon. Both the Japanese and

Western armies experimented with Francisella tularensisdur-

ing World War II. Experiments during and after that war estab-

lished the devastating effect that aerial dispersion of the

bacteriacould exact on a population. Until the demise of the

Soviet Union, its biological weapons development program

actively developed strains of the bacterium that were resistant

to antibioticsand vaccines.

Tularemia naturally occurs over much of North America

and Europe. In the United States, the disease is predominant in

south-central and western states such as Missouri, Arkansas,

Oklahoma, South Dakota, and Montana. The disease almost

always occurs in rural regions. The animal reservoirs of the

bacterium become infected typically by a bite from a blood-

feeding tick, fly, or mosquito.

The causative bacterium, Francisella tularensis,is a

Gram-negative bacterium that, even though it does not form a

spore, can survive for protracted periods of time in environ-

ments such as cold water, moist hay, soil, and decomposing

carcasses.

The number of cases of tularemia in the world is not

known, as accurate statistics have not been kept, and because

illnesses attributable to the bacterium go unreported. In the

United States, the number of cases used to be high. In the

1950s thousands of people were infected each year. This num-

ber has dropped considerable, to less than 200 each year in the

1990s and those who are infected now tend to be those who

are exposed to the organism in its rural habitat (e.g., hunters,

trappers, farmers, and butchers).

Humans can acquire the infection through breaks in the

skin and mucous membranes, by ingesting contaminated

water, or by inhaling the organism. An obligatory step in the

establishment of an infection is the invasion of host cells. A

prime target of invasion is the immune cell known as

macrophages. Infections can initially become established in

the lymph nodes, lungs, spleen, liver, and kidney. As these

infections become more established, the microbe can spread to

tissues throughout the body.

Symptoms of tularemia vary depending on the route of

entry. Handling an infected animal or carcass can produce a

slow-growing ulcer at the point of initial contact and swollen

lymph nodes. When inhaled, the symptoms include the sudden

development of a headache with accompanying high fever,

chills, body aches (particularly in the lower back), and fatigue.

Ingestion of the organism produces a sore throat, abdominal

pain diarrhea, and vomiting. Other symptoms can include eye

infection and the formation of skin ulcers. Some people also

develop pneumonia-like chest pain. An especially severe

pneumonia develops from the inhalation of one type of the

organism, which is designated as Francisella tularensis biovar

womi_T 5/7/03 11:03 AM Page 557