Insights into Editorials: Understanding scrub typhus
The centre recently asked for a detailed report on scrub typhus, a bacterial disease, from the Himachal Pradesh government in view of the rising number of cases. The centre has assured support to the state for managing the endemic disease.
- The situation is being closely monitored and, if requested, the centre will provide all logistical and technical support to the Himachal Government.
- The disease has affected more than 700 people and claimed 20 lives. In Delhi, where the disease in not very common, 33 people have tested positive and two have died of it so far this year.
What is Scrub Typhus?
Scrub typhus is an infectious disease with symptoms similar to any viral fever. However, it is not caused by a virus, but by a parasite called Orientia tsutsugamushi, which is transmitted by the bite of infected mite larvae in soil containing scrub vegetation.
The disease is also known as bush typhus because the mites (Leptotrombidium deliense, commonly known as trombiculid mite) that cause it reside in vegetation predominantly comprising small shrubs.
The disease is more common during the wet season when the mites lay eggs. Incubation period (time between bite and beginning of symptoms) is 10 – 14 days.
It is usually transmitted by mites that are found in the shrubs in hilly areas. It can also be transmitted by lice, ticks and fleas.
Causes of Scrub Typhus:
The species which transmits Scrub typhus are found in areas which have heavy scrub vegetation.
- Orientia tsutsugamushi gets transmitted through the bite of trombiculid mites. These mites feed on rural and forest rodents, including voles, rats and field mice.
- A person develops infection after the bite of the mite larva. When a person gets bitten by this mite, it leaves a characteristic black colored eschar which helps with the diagnosis.
The symptoms of scrub typhus are similar to chikungunya. At onset there is fever, headache, bodyache, cough and gastrointestinal symptoms. Patients with a mild infection may recover without any other symptoms. However, roughly every second patient develops a visible black scab at the point of the bite, with a swelling of the lymph nodes.
- In about a third of cases, a delayed onset of rashes occurs 4-6 days into the disease. Severe cases typically include encephalitis and interstitial pneumonia due to vascular injury. The fatality rate is 7%.
- Other symptoms include high fever, skin rashes, respiratory problems, red eyes and unconsciousness. Some of the patients also develop joint pains, which is characteristic of chikungunya.
- It may progress on to respiratory distress, pneumonitis (inflammation of lung tissue), and multi-organ failure.
Himachal Pradesh is one of the endemic areas for the disease — it is also endemic in Pakistan, Afghanistan, Thailand, northern Australia, the Arabian peninsula and Japan. It is an occupational disease frequently found in people who work in the fields and are in the habit of gardening.
Why Himachal Pradesh is more vulnerable?
In Himachal Pradesh, the disease spreads most commonly during grass cutting operations in the orchards, and is alleged to have taken a serious turn this year due to laxity in controlling the mite.
What needs to be done?
If detected in time, the disease can be cured using antibiotics. Antibiotics like Doxycycline or Azithromycin are commonly used to treat the disease. Dengue and chikungunya are self-limiting viral diseases that do not have any treatment, apart from management of symptoms. In scrub typhus, however, administering antibiotics on time can save lives.
But, getting an early diagnosis is a problem in Himachal, where Indira Gandhi Medical College and Hospital (IGMCH) is the only scrub typhus testing and treating centre.
- Limit the spread of rodents.
- Pets should be cleaned regularly.
- Skin should be properly covered while visiting jungle or area with lot of shrubs.
No vaccines are available as of now. Clearing the brush and using residual insecticides to spray the infested areas help in decreasing and eliminating mite population. Insect repellants should be used when the patient is at risk for exposure.