The four main types of typhus are:
Epidemic typhus is caused by Rickettsia prowazekii, which is carried by the body louse, Pediculus humanus corporis. When the lice feed on a human, they may simultaneously defecate. When the person scratches the bite, the faeces, which carry the bacteria, are scratched into the wound. Body lice are common in areas in which people live in overcrowded, dirty conditions, with few opportunities to wash themselves or their clothing. Because of this fact, this form of typhus occurs simultaneously in large numbers of individuals living within the same community.
Epidemic typhus causes fever, headache, weakness, and muscle aches. It also causes a rash composed of both spots and bumps. The rash starts on the back, chest, and abdomen, then spreads to the arms and legs. The worst types of complications involve swelling in the heart muscle or brain (encephalitis). Without treatment, this type of typhus can be fatal. The disease is characterized by high fever, intractable headache, and rash. Temperature reaches 104° F in several days and remains high. Headache is generalized and intense. A macular eruption (dark spot on the skin) appears on the day, initially on the upper trunk, which then spreads to the entire body excepting, usually, the face, palms and soles of the feet. The case-fatality rate is between 1% and 20%. Prostration is due to low blood pressure, may be followed by vascular collapse. Fatalities are rare in children; mortality increases with age.
Brill-Zinsser disease is a reactivation of an earlier infection with epidemic typhus. It affects people years after they have completely recovered from epidemic typhus due to weakening of their immune system. The bacteria can then gain hold again, causing illness, which tends to be extremely mild. Brill-Zinsser disease is quite mild, resulting in about a week-long fever, and a light rash similar to that of the original illness.
Scrub typhus is caused by Rickettsia tsutsugamushi. This bacterium is carried by mites or chiggers. As the mites feed on humans, they deposit the bacteria. Scrub typhus occurs commonly in the southwest Pacific,
Scrub typhus causes a wide variety of effects. The main symptoms include fever, headache, muscle aches and pains, cough, abdominal pain, nausea and vomiting, and diarrhea. Some patients experience only these symptoms. Some patients develop a rash, which can be flat or bumpy. The individual spots eventually develop crusty black scabs. Other patients go on to develop a more serious disease, in which encephalitis, pneumonia, and swelling of the liver and spleen (hepatosplenomegaly) occur. Onset is sudden with fever, chills, headache, and generalized swelling of lymph nodes. At onset of fever, a red lesion develops at the site of the bite. High fever to 104 °F develops during the first week as well as a severe headache. A cough is present during the first week of fever and pneumonia may develop. A rash also develops on the torso often extending to the arms and legs.
Also called endemic typhus, it is carried by fleas. When a flea lands on a human, it may defecate as it feeds. When the person scratches the itchy spot where the flea was feeding, the bacteria-laden faeces are scratched into the skin, thus causing infection. The causative bacterium is called Rickettsia typhi. Endemic typhus occurs most commonly in warm, coastal regions. In the
A number of tests exist that can determine the reactions of a patient’s antibodies (immune cells in the blood) to the presence of certain viral and bacterial markers. When the antibodies react in a particular way, it suggests the presence of a rickettsial infection. Many tests require a fair amount of time for processing, so the practitioners will frequently begin treatment without completing tests, simply on the basis of a patient’s symptoms.
Cleanliness is important in preventing body louse infestations. The easiest control method for occasional infestations is to expose infested clothing to a minimum temperature of 70o C for at least one hour. In general, chemical control is required, which involves dusting technique to apply insecticides and treating clothing. Suitable insecticidal dusts for body louse control are permethrin (0.5%), temephos (2%), propoxur (1%) and carbaryl (5%). One thorough treatment of infested clothing with insecticide should be sufficient. Dusting is not recommended for people with dermatological problems or exposed wounds. Where infestation is known to be widespread, systematic application of insecticide to all persons in the community is recommended.