This Gram-negative, intracellular bacteria is quite small and, in addition, it is responsible for causing the disease typhus, which is called classic, European, or epidemic typhus. This bacteria that attacks only humans is spread by the body louse, or occasionally the head louse, and it is usually worst in areas of crowding, poverty, or bad sanitation. The bacteria, which has a short generation time of about ten hours, is first picked up by the louse from a human blood that it consumed. The bacteria enter the digestive system of the louse, and they begin to replicate, which allows the louse to spread the disease to other humans. The bacteria enters the body through the feces or the vomit of the louse, or if a crushed louse is able to get into the skin. Eventually the bacteria in the digestive system of the louse becomes so numerous, that in about ten days the louse itself dies.

The symptoms begin about ten days after infection and usually include a fever, pain, stiffness, and headache. After about five days of the symptoms, a rash, dark red with bumps, appears all over the body. The person infected will become delirious, contract pneumonia, or even get gangrene and after about two to three weeks, the person will become better, or the disease will go to their nervous system when it becomes deadly. Typhus is an odd bacteria, because unlike most, about twenty five percent of its DNA does not code for anything. The twenty five percent is beginning to disappear through mutations, which is causing the bacteria to depend more on the host's reproductive system and metabolism, so it is becoming more and more like a virus than a bacteria, in that aspect. Also like a virus, they need to use the host to grow, and also they need them because they cannot metabolize glucose. A different variant caused by the same bacteria, called Brill Zinsser Disease, or recurdescent typhus, is a milder disease caused by a relapse of the typhus bacteria, usually still evident in the lymph nodes. Lice or even physical contact can transfer the bacteria and infect others in this sickness.

Epidemic typhus was a very deadly disease. It killed about three million people in World War I, and in the two world wars, it infected an estimated twenty to thirty million people, and killed about three million again. It was especially bad in the poorer less clean areas where the epidemics spread quickly and killed many. In some epidemics, the death rate can be as high as fifty to seventy five percent.

At the end of World War II, antibiotics were being discovered, there were some vaccines, and the lice that carried the bacteria were killed with pesticides such as DDT, so there were many less deaths from the bacteria especially in the army. Treatment was first attempted with chloromycetin and aureomycin, but later newer and better antibiotics were used. It was noted that the antibiotics tetracycline and chloramphenocal would stop the disease, and attempts at vaccination were made, but they were generally unsuccessful, because there would be some resistance to the disease, but the person would never become fully immune to the Rickettsia prowazekii bacteria. Finally, this bacteria is thought to be very similar to a mitochondrion in a eukaryotic cell.

Return to Bacterial Disease Page

http://www.cegs.siu.edu/fix/medmicro/ricke.htm
http://www.ucs.man.cca/~u57raj/intro.html
http://www.ncgr.org/microbe/rickettsiatxt.html

"Typhus" Microsoft Encarta1995