Epidemic Typhus

(2) Causative Agent

Cause/Vector: Epidemic Typhus is caused by Rickettsia prowazekii bacteria. Rickettsia prowazekii is a gram-negative intracellular bacterium with a bacilli structure. The genome of Rickettsia prowazekii is composed of a singular circular chromosome. Rickettsia that are intracellular parasites of many animals and utilize the components within the cell to survive and multiply. They are difficult to cultivate because they usually only grow within cells they infect. The disease occurs after the bacteria is transferred to humans usually by vectors such as fleas or lice that have acquired the bacteria from animals such as rats, cats, opossums, raccoons, and other animals. Epidemic typhus is usually spread or transmitted from body lice feces contaminated with Rickettsia prowazekii or occasionally from animal droppings contaminated with these bacteria. Epidemic typhus also means that a few animals, (usually rats) via lice vectors, can incidentally infect large numbers of humans quickly when certain environmental conditions are present (poor hygiene, poverty, crowded human living conditions) with the more pathogenic Rickettsia prowazekii.

(7) Course of Disease

Complication: Complications that might occur with people infected with epidemic typhus are renal insufficiency, pneumonia, damage to the central nervous system. The worst types of complications involve swelling in the heart muscle or brain (encephalitis). Also, epidemic typhus has a milder form termed Brill-Zinsser disease; it occurs when rickettsia prowazekii bacteria reactivate in a person previously infected with epidemic typhus. Brill-Zinsser disease is quite mild, resulting in about a week-long fever, and a light rash similar to that of the original illness.

(9) Interventions

Preventions: Epidemic typhus can be reduced or prevented by good hygiene and clean living conditions that reduce or eliminate exposure to rats, mice, and other animals and the vectors that they carry (lice, fleas). Efforts to prevent typhus have been successful when people are able to avoid contact with the vectors that spread typhus (mainly fleas and lice) or fecal droppings from rodents. Many experts suggest that good sanitation and reducing populations of rats, mice, and other animals that may carry the bacteria and their vectors is effective. Insect repellents are advised if fleas and lice are found in the local environment.

(5) Course of disease

Symptoms: People who acquire epidemic typhus can experience symptoms such as high fever, headache, severe muscle pain (myalgia), cough, chills, and joint pain. Patients with severe epidemic typhus may develop additional symptoms like bleeding into the skin (petechiae), delirium, stupor, hypotension, and shock, which can cause their death (10%-60%). 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 except the palms of the hands and soles of the feet.

(10) References

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(1) Epidemic Typhus

Hi. I am Tiffany and I will be talking about Epidemic Typhus

(6) Course of disease

Diagnosis: Epidemic typhus prognosis can range from good, with early effective treatment, to poor, with the elderly often having the worst prognosis. Early diagnosis and appropriate treatment yield an excellent prognosis for almost all patients with any of the types of typhus. Delayed or undiagnosed or untreated typhus has a less promising prognosis. The diagnosis is based on the patient's clinical history, physical exam, and tests. Tests based on identification of the bacterial genus and species by PCR testing of skin biopsy of skin rash, skin lesions, or blood samples or by immunohistological staining that identifies the bacteria within infected tissue (skin tissue, usually). Although some state labs may do these tests, the CDC should be contacted for testing questions and be given information if there is an outbreak of epidemic typhus. These tests help distinguish between epidemic and endemic typhus, anthrax, and other viral diseases. 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 practitioners will frequently begin treatment without completing tests, simply on the basis of a patient's symptoms. The infections typically last from 1 week to several weeks. If they go untreated or if treatment does not begin soon after infection, the disease can linger for months.

(8) Interventions

Treatments: Antibiotic therapy is recommended for epidemic typhus infections because early treatment with antibiotics can cure most people infected with the bacteria. Consultation with an infectious-disease expert is advised especially if epidemic typhus in pregnant females is diagnosed. Treatments of antibiotics include: - Doxycycline (such as Vibramycin, Oracea, Adoxa, Atridox) - Tetracycline (like Sumycin): Tetracycline taken by mouth can permanently stain teeth that are still forming. It is usually not prescribed to children until after all of their permanent teeth have grown in. - Chloramphenicol - Azithromycin (an example woZithromax, Zmax) Patients with epidemic typhus may need intravenous fluids and oxygen. Untreated epidemic typhus has a death rate that ranges from about 10%-60% of infected patients, with those over 60 years of age having the highest death rates. . Without treatment, this type of typhus can be fatal. Although vaccines have been made in the past, currently there is no commercially available vaccine for epidemic typhus. The CDC does not recommend taking any antibiotics to prevent the disease. Typhus vaccine is a vaccine containing a suspension of inactivated Rickettsia prowazekii that has been grown in embryonate eggs, used to immunize against epidemic typhus.

(3) Population affected

Typhus risk factors include living in or visiting areas where the disease is endemic, such as many port cities where rat populations are high or areas where trash accumulates and hygiene may be low such as disaster zones, homeless camps, poverty-stricken areas, and other similar situations that allow rodent populations to come in close contact with people. Epidemic typhus occurs in communities and areas with poor sanitation, such as disaster areas, poverty-stricken areas, refugee camps, and jails. Epidemic typhus occurs in these communities because these areas have the highest populations of rats, mice, and animals, making these areas have the vectors carry the bacteria from the animals to the humans more easily. Outbreaks often occur during the colder months when infested clothing is not washed.