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Microorganism: prion

Disease: Creutzfeldt-Jakob

Occurrence of the disease

Current situation: At the end of the 1950s, the American neurologist, Carleton Gajdusek, was vacationing in Australia where, according to some of his colleagues, a tribe from Papua - New Guinea was affected by a disease known as kuru. Gajdosek went to Papua and settled there to study the disease. In the tribe’s language, the word kuru means “to tremble.” Victims of the disease generally lost control of their movements and died three months to a year after the appearance of the first symptoms. Women were more affected than men (3:1) and children, regardless of their sex, were more affected than were adults.

Autopsies of the brains of people affected by kuru revealed holes in their neurons (spongiform encephalopathy). Gajdusek then discovered that the members of the tribe practiced a post-mortem ritual: cannibalism. The causal agent for the disease, located mostly in the brain, was transmitted through this ritual. Certain parts of the deceased, such as the muscles, were reserved for the men. The brain and the internal organs were reserved for women and children. When cannibalism was discontinued, kuru disappeared.

By searching the literature, William Hadlow discovered that humans suffering from Creutzfeldt-Jakob disease, fatal familial insomnia, and Gerstmann-Straussler-Scheinker disease showed the same symptoms. Furthermore, the symptoms of scrapie and mad cow disease were also identical. In fact, the same type of agent causes all these diseases: prions.

Mechanism of action of the microorganism: prions are mainly found in brain neurons (message transmitters and receptors) and in neurons of the central nervous system (certain types of nerves). The cellular protein PrPc is normally present in the nervous systems of animals. In the presence of PrPsc (sc for scrapie, the term used to designate the disease caused by prions in sheep), PrPc undergoes a change in conformation to become an infectious protein itself: a prion.

Symptoms of the disease: confusion, motor disturbances (lack of coordination), dementia, nervous tics, memory impairment, insomnia, etc.

Incubation period: from 15 months to 30 years

Contagious period: the tissues of the central nervous system are contagious while symptoms are present but a few studies have shown that the disease may be transmissible even before the symptoms appear.

Hosts: humans and possibly animals

Transmission: poorly defined. Often, propagation is associated with the transplantation or the injection of infected tissues. Some researchers also believe that the consumption of meat containing prions responsible for mad cow disease can lead to Creutzfeldt-Jakob disease.

Mad cow disease is often associated with Creutzfeldt-Jakob disease because prions are responsible for both diseases. Because the inter-species incubation period is between ten and 40 years, it will take some time before we are able to attribute Creutzfeldt-Jakob disease to the ingestion of prion-contaminated bovine meat.

Discoverer of the microorganism: Stanley B. Prusiner

Treatment: none

Geographical distribution of the microorganism: this disease has been reported worldwide

Prevention: being very careful, during organ transplantation, to avoid using tissue infected with prions. In Canada, we do not accept blood donors who have recently spent time in England.

Vaccine: not available