Microbiology and Immunology

WORLD OF MICROBIOLOGY AND IMMUNOLOGY BSE and CJD disease

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From the initial lymph node, the Brucella spread out to other

organ targets, including the spleen, bone marrow, and liver.

Inside these organs, the infected cells form granulomas.

Diagnosing brucellosis involves culturing the blood,

liver, or bone marrow for Brucella organisms. A positive culture

alone does not signify brucellosis, since persons who have been

treated for the disease may continue to harbor Brucella bacteria

for several months. Confirmation of brucellosis, therefore,

includes a culture positive for Brucella bacteria as well as evi-

dence of the characteristic symptoms and a history of possible

contact with infected milk or other animal products.

In humans, brucellosis caused by B. abortusis a mild dis-

ease that resolves itself without treatment. Brucellosis caused

by B. melitensisand B. suis,however, can be chronic and

severe. Brucellosis is treated with administration of an antibiotic

that penetrates host cells to destroy the invasive bacteria.

Since the invention of an animal vaccinefor brucellosis

in the 1970s, the disease has become somewhat rare in the

United States. Yet the vaccine cannot prevent all incidence of

brucellosis. The Centers for Disease Controlusually reports

fewer than 100 total cases per year in the United States. Most

of these were reported in persons who worked in the meat pro-

cessing industry. Brucellosis remains a risk for those who

work in close contact with animals, including veterinarians,

farmers, and dairy workers.

Brucellosis also remains a risk when animal products

from foreign countries are imported into the United States.

Outbreaks of brucellosis have been linked to unpasteurized

feta and goat cheeses from the Mediterranean region and

Europe. In the 1960s, brucellosis was linked to bongo drums

imported from Africa; drums made with infected animal skins

can harbor Brucella bacteria, which can be transmitted to

humans through cuts and scrapes in the human skin surface.

In the United States, preventive measures include a rig-

orous vaccinationprogram that involves all animals in the

meat processing industry. On an individual level, people can

avoid the disease by not eating animal products imported from

countries where brucellosis is frequent, and by avoiding foods

made with unpasteurized milk.

See also Bacteria and bacterial infection; Food safety;

Infection and resistance; Pasteurization

BSE BSE and CJD disease ANDCJD DISEASE

Bovine spongiform encephalopathy (BSE) and Creutzfeldt-

Jakob Disease (CJD) are ailments in which the functioning of

the brain is progressively impaired. Both diseases are associ-

ated with visually abnormal pinpoints (or plaques) in the

brain, and in a changed texture of the brain tissue. The brain

tissue, particularly in the cortex and cerebellum, becomes

filled with large open spaces (vacuoles) and becomes spongy

in texture. The “spongiform” part of BSE comes from this tex-

ture characteristic.

BSE is a disease of animals such as cattle and sheep,

while CJD is associated with humans. However, the two dis-

eases may have a common cause. The cause of BSE and CJD,

and of other diseases such as scrapie, transmissible mink

encephalopathy, fatal familial insomnia, and kuru, are prions.

Prions are particles that are made solely of protein. Even

though they lack genetic material, they are infectious.

Both BSE and CJD are characterised by a loss of coor-

dination and the control over functions such as grasping and

holding, dementia, paralysis, eventually leading to death. There

is no cure for either disease, and no are vaccines available.

CJD derives its name from its discoverers. Progressive

and ultimately fatal dementia that was accompanied by other

neurological abnormalities was described in six patients in the

1920s by two German neuroscientists, Hans Gerhard

Creutzfeldt and Alphons Maria Jakob. In the 1960s, the neu-

rological changes associated with the development of CJD had

become accepted by the medical community.

The average incidence rate for CJD over time is about

one person per million. Clusters of CJD do occur. The most

recent example is the 48 confirmed cases that were diagnosed

in Britain between 1996 and 2001. There is no evident

predilection for a gender, any ethnic group, or for geographi-

cal location. However, the incidence in those over 55 years of

age is far higher (over 30 times) than for those under 55 years.

Three means of acquiring CJD have been identified.

First, the disease can be genetically inherited. This is also

described as familial CJD. Secondly, the disease can appear

with no exact origin being known. About 85% of CJD cases

are of this unknown variety. Lastly, the disease can be

acquired during surgery. This so-called iatrogenic form is typ-

ically a result of CJD-contaminated equipment or tissue (brain

and corneal grafts are two examples).

There is no cure for CJD. Treatment consists of man-

aging the patient so that his/her increasingly impaired men-

tal faculties do not result in injury, and in personal care as

these functions become impossible for the person to perform

themselves.

BSE causes a progressive neurological deterioration in

cattle that is similar to the course of CJD in humans. Cattle with

BSE are more temperamental, have problems with their posture

and coordination, have progressively greater difficulty in rising

off the ground and walking, produce less milk, have severe

twitching of muscles, and loss weight even though their appetite

is undiminished. The so-called incubation period, the time from

when the animal is first infected until symptoms appear, ranges

from two to eight years. After appearance of symptoms, deteri-

oration is rapid and the animal dies or is destroyed within six

months. The disease is one of several so-called transmissible

spongiform encephalopathies (TSEs) in animals.

BSE was confirmed as a disease of cattle in November

of 1996. Since then, almost all reported cases have been in cat-

tle born in the United Kingdom. Other countries in Europe and

Asia have reported BSE, but in far fewer numbers than in

Britain. No cases have been detected in the United States (the

U.S. has not imported U.K. beef since 1985 and maintains a

rigorous surveillance program). As of November 2001, the

total number of confirmed cases of BSE in U.K. cattle was just

over 181,000. In 1993, a BSE epidemic in the U.K. peaked at

almost 1,000 new cases per week. While the cause of this

near-exclusivity has yet to be conclusively determined, the

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