|
||||||||||||
Scrub Typhus: essential data |
|
Rickettsial weapon acting on humans |
|
Synopsis, Diagnosis, Symptoms,
|
|
|---|---|
Safety Precautions for Scrub Typhus Casualties |
Standard Precautions defined by the 1996 CDC guidelines should be adopted for handling patients.Tick control may need to be practiced.Biosafety level 2 or 3 practices should be adopted for handling of samples. |
| Causative organism: (Systematic name in 1997) |
|
|---|---|
| Older names: |
|
| Alternative disease names: |
|
| Properties: | Very small Gram-neg. pleiomorphic intracellular coccobacillus.
(Very small variably shaped or short rod-shaped microorganism staining red in the Gram stain that must survive in the cells of a host.) |
| Antibiotic treatments: |
|
| Vector involvement: | Scrub typhus is carried by a large number number of mites known as the Trombiculid or scrub typhus mites. The most important of these is the genus Leptotrombidium. |
| Epidemiology of natural outbreaks: | Natural outbreaks of the disease are limited to India, Asia south and east of India, and Australia. The major animal reservoirs are rodents, especially rats. |
If the disease arises from a bite by an infected vector (a mite of the genus Leptotrombidium) then an ulcer forms at the bite. Otherwise, the first symptoms are a lymphadenopathy (swollen glands) and a rash that begins on the trunk and spreads outwards. Pneumonitis is also common.
Differential DiagnosisOther disease or conditions that need to be eliminated | |
|---|---|
| Other infectious diseases | Other problems |
|
|
| NOTE: Differential diagnosis of Rickettsial disease is difficult, but antibiotic treatments are generally effective against them and it is preferable to begin a general antibiotic treatment as soon as Rickettsial involvement is suspected than to wait for confirmation | |
Symptoms and effects.
After an incubation period of a little over a week (10-12 days), the victim develops a fever, headache, anorexia and general apathy. Within a few days (5-8) a dull red rash develops, especially on the trunk that spreads to cover the entire body within a few days. Further developments may include enlargement of the spleen, neurological problems, delirium and prostration. The mortality rate is 6-35% with death often the result of secondary infection and usually coming at about the second week of infection.
Re-infection is not uncommon in endemic areas.
Vaccination (Immunoprophylaxis)
A vaccine is not available
Antibiotics
The disease responds well to tetracyclines, which must be taken until three days after the fever subsides. Doxycycline is preferred.
Supportive care
Ticks must be removed. The disease can affect many organs, so a wide range of supportive measures measures, e.g. analgesics, maintenance of blood pressure, supporting of breathing, must be kept ready. Intravenous prednisolone and cold-sponging of patients with high fevers (>40°C, 104°F) are often used in the treatment of rickettsial disease.
Decontamination
The agent is killed by standard disinfectants (1% sodium hypochlorite, 70% ethanol, glutaraldehyde, formaldehyde) and to moist heat (121°C for at least 15 min) and dry heat (160-170°C for at least 1 hour)
Treat the affected area for tick infestation. The patient and his medical and nursing staff may also need to be treated with malathion or DDT to prevent reinfection.
Agent Properties and Potential Uses
The disease is found in Australia and tropical Asia from the Pacific to Pakistan and was a major problem for Allied forces in the Pacific campaigns of World War II. Misdiagnosis is relatively common because the rash and ulcerated bites are not as common as the textbooks say. The microorganism uses rats as a host and is transmitted by mites. The mites pass the pathogen to their offspring through infected eggs. The agent is very fragile when separated from its host and vector organisms.
Terrorist Acquisition and Attempted Use.
| Disease | IDC-9M | IDC-10 |
|---|---|---|
| Scrub typhus | 081.2 | A75.3 |
|