Several rickettsia species cause the disease known as epidemic typhus in humans. The disease is spread by ticks, mites, fleas, or lice, each agent having a distinct epidemiology, but all causing a disease with signs similar to a bad cold with fever lasting form one to several weeks, chills, headache, and muscle pains, as well as a body rash. There is often a large painful sore at the site of the bite and nearby lymph nodes are swollen and painful.
The four main types of typhus are:
Epidemic typhus is prevalent worldwide. It is an acute disease passed from human to human by the body louse. Endemic epidemic typhus exists in highland populations in Africa and South America but tourists are at minimal risk of acquiring lice and disease. Since World War II, large outbreaks of typhus have occurred mainly in Africa, with reported cases coming predominantly from three countries: Burundi, Ethiopia and Rwanda.
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 fifth to sixth 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.
Tick typhus, actually a form of spotted fever, is not uncommon in travellers who spend time trekking or on safari in Africa or the Indian subcontinent. Trekkers in southern Africa may be at risk from cattle or wild-animal ticks.
Seek local advice on areas where ticks pose a danger and always check your skin carefully for ticks after walking in a danger area such as a tropical forest. A strong insect repellent can help, and serious walkers in tick areas should consider having their boots and trousers impregnated with benzyl benzoate and dibutylphthalate.
Scrub typhus is spread by mites that feed on infected rodents and exists mainly on Pacific islands and in southeast and east Asia. Incidence is highest during the spring and summer when the activity of humans brings them in contact with mites seeking animal hosts.
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, Southeast Asia, and Japan. It is a very common cause of illness in people living in or visiting these areas. It occurs more commonly during the wet season.
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.
Murine typhus is relatively common throughout the world and is transmitted by fleas. It is clinically similar to epidemic typhus, but milder. Highest incidence of cases occurs during the summer months when rats and their fleas are most active and abundant.
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 United States, southern Texas and southern California have the largest number of cases.
Symptoms of the disease include chills, headache and fever, lasting about 12 days. Rash and other manifestations are similar to epidemic typhus.
DIAGNOSIS
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.
Prompt removal of attached ticks and use of repellents to prevent tick attachment provide the best preventions against tick typhus. Laundering of louse-infested clothing is the most effective means to avoid person-to-person spread of lice and prevent epidemic typhus. Precautions taken when walking in rural areas and the use of insect repellents will help prevent tick and mite-borne typhus. Prevention for each of these forms of typhus includes avoidance of the insects that carry the causative bacteria. Other preventive measures include good hygiene and the use of insect repellents.
Vaccination against typhus is not required by any country as a condition for entry. Treatment of all forms of typhus is similar. Production of typhus vaccine in the United States has been discontinued and there are no plans for commercial production of a new vaccine.
TREATMENT
The antibiotics tetracycline or chloramphenicol is used for treatment of each of the forms of typhus. Chloramphenicol, doxycycline or other forms of tetracycline result in rapid resolution of fever and relapses are infrequent. A single dose of 200 mg of doxycycline (two tablets), irrespective of the patient’s age can be given.
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.