Scrub Typhus – a Re-Emerging Disease India Can No Longer Afford to Ignore

There is a need for greater awareness of the potentially fatal illness, which is misconceived as an exotic disease only affecting people in rural areas and whose symptoms can be mistaken for dengue, malaria or typhoid.

The disease is prevalent in both rural and urban India. Credit: Reuters

In the coming months, an illness presenting symptoms of dengue, typhoid, severe pneumonia or multi-organ dysfunction, may, in fact, be scrub typhus – be it in Goa or Gorakhpur, Darjeeling or Delhi, Bikaner or Bellary.

In July 2016, a 40-year-old tailor from Bellary district had been suffering from fever for 12 days and had been experiencing vomiting for five days. He was suspected to have dengue because of his low platelet count. However, tests for dengue were negative and his fever persisted. He also had a painless ulcer with a black scab in the centre (termed an eschar) and made a rapid recovery after oral medication.

Last August, a 35-year-old farmer from Chakrata in Uttarakhand had been suffering from fever for five days, which was followed by a dry cough and increasing breathlessness. She was diagnosed with pneumonia and treated with antibiotics. However, within the next two days, pneumonia progressed and she had to be admitted to the ICU of a hospital near Dehradun where she was put on a ventilator. She had an eschar similar to the first patient in her armpit and had a low platelet count with complications in multiple organs.

A 65-year-old from Kannur district in Kerala was admitted to a hospital with fever, abdominal pain, breathlessness, renal failure and an altered level of consciousness – suggesting a serious involvement of multiple organs. Her diagnosis was made just in time and she improved, though gradually.

All three showed different facets of scrub typhus, a re-emerging infectious disease in India, which has been reported from all the areas mentioned above. After several hundreds of cases were seen in Assam during the Second World War, it seemingly disappeared from sight.

It, however, resurfaced in the 1990s, causing some fatalities among the cadets of the Indian Military Academy in Dehradun who had trekked in the hills. In the new millennium, clinical researchers familiar with the disease regularly documented cases from Himachal Pradesh and Tamil Nadu, with a few cases even reported in Delhi.

In recent years, the scale of the disease has expanded, with a couple of thousand cases reported from most Indian states, mainly from the tertiary care institutions. Investigations into outbreaks of a “mystery fever” that caused tens of deaths in a few weeks, in Alwar for example, have also uncovered scrub typhus as the underlying cause.

A review of the disease in 2013 noted that “scrub typhus is probably the single most prevalent, under-recognised, neglected and severe but easily treatable disease in the world.”

I had the opportunity of detecting a large outbreak of this disease in Uttarakhand in 2012, and our study of the seasonality, clinical manifestations and outcomes of scrub typhus was recently published in the Indian Journal of Medical Research. The scale and severity of scrub typhus were daunting and for a period of the year, nearly one-third to half of the ICU beds were occupied by patients suffering from this disease.

Even at the Christian Medical College in Vellore, scrub typhus accounts for 36% of patients admitted with tropical infections, outnumbering those with malaria and dengue fever. It is time that we become familiar with the facts of this disease and clear some of the misconceptions around it, in order to diagnose it early and prevent its serious complications.

Causes of scrub typhus

Scrub typhus is caused by a bacterium called Orientia tsutsugamushi, which is introduced into our bodies from the bites of the infected larvae of a certain kind of mite. The adult mites do not bite, and the larvae – which are too small to be seen by the naked eye – do so in a painless manner.

These larvae are present on blades of grass, small bushes, shrub, and usually bite rats, shrews or even birds. We become accidental victims during the course of a range of activities – cutting grass, collecting fuelwood, walking barefoot or sitting on the grass.

Thus, even city dwellers are at a risk of infection if there happen to be rats around (common sight in both urban and rural areas), and if the grass in their lawn or parks is inhabited by these mite larvae, which explains why some of the occupants of posh colonies of Chandigarh and Delhi developed scrub typhus.

Surveys conducted in the Northeast, South India and North India have shown that 30-50% of the population surveyed had been exposed to the organisms which cause scrub typhus. Exposure to infection is therefore common and the disease is probably greatly underreported.

 Common symptoms

The disease may occur to a certain extent throughout the year. However, we found that in northern India, most patients presented with signs of the disease in the months from July to November, which is similar to the seasonal pattern in north-eastern India. In southern India, cases are most frequent in the months from October to February. These months correspond with the increased activity of mites after rains.

Scrub typhus is a disease with diverse manifestations and variable severity. It always begins with a fever with non-specific features like a headache or muscle aches and may continue as such, thus being mistaken for dengue, malaria or typhoid.

In some patients, after a few days of untreated illness, complications may develop and the patient may present with a cough or shortness of breath, jaundice, abdominal pain, altered consciousness or a combination of these symptoms. These symptoms are confusing to doctors who may not suspect scrub typhus as the underlying cause.

In our study, nearly half of our patients with scrub typhus presented signs of severe pneumonia and were unresponsive to usually administered antibiotics like penicillin, cephalosporin or quinolone. This pneumonia was often rapidly progressive, requiring ICU care with mechanical ventilation.

Chest X-ray of a patient with extensive pneumonia due to scrub typhus. Courtesy: Anurag Bhargava

Scrub typhus can present like acute encephalitis, and it recently became known that a significant proportion of children suspected of having Japanese encephalitis in Gorakhpur, UP, in fact, presented evidence of scrub typhus. This is a subject of further research, and since scrub typhus is treatable, there is hope for reducing the deaths which until now were being attributed to Japanese encephalitis, for which no curative treatment exists.

Diagnoses and treatment

There is a need for greater awareness of scrub typhus, especially among physicians working at the primary and secondary care levels, and for better availability of diagnostics in the healthcare system. An experienced physician may be able to diagnose scrub typhus with confidence on a physical examination alone if he or she looks carefully for the presence of an eschar, which is an indication of scrub typhus in India and is seen in nearly half the cases.

The eschar is an ulcer, one to two centimetre in size with a black scab in the centre (resembling a cigarette burn), which occurs at the site of the larvae bite, and does not cause pain or itching. This lack of symptoms and the fact that it may be in the armpits, groin or abdomen, means that a cursory examination is not enough and a careful clinical examination is required.

A close up of the eschar on the abdomen of a patient with severe pneumonia due to scrub typhus. Courtesy: Anurag Bhargava

Tests which are commonly performed in patients with fever may show low platelets (which can be confused with dengue) and raised liver enzymes. The diagnostic tests for scrub typhus rely on demonstration of antibodies against the organism and may not be positive in the first week of illness. Reliable point-of-care tests for scrub typhus, akin to those available for malaria, are an urgent need.

The uncertainties involved in the diagnosis of scrub typhus and the time taken for conducting some of the tests may delay the initiation of treatment, which greatly increases the risk of serious complications. The treatment of scrub typhus in its early stages is simple and highly effective and involves drugs like doxycycline and azithromycin, which however should only be given under supervision.

Doxycycline should not be taken during pregnancy. The response to an antibiotic effective against scrub typhus is so prompt (within 48 hours) that it constitutes a kind of therapeutic test.

Misconceptions surrounding scrub typhus

As pointed earlier, scrub typhus is not a new but a re-emerging disease in India. The name, scrub typhus, is a bit of a misnomer as it is not limited to scrubland – a place where shrubs are the dominant vegetation (one report even referred to it as ‘jungle fever‘).

It has been reported from a wide variety of habitats from agricultural plains to hills to coastal regions and even deserts. In our study, there were more than 100 patients with scrub typhus from Uttar Pradesh’s agricultural belt, where this disease is not commonly suspected or reported. The disease is not limited to rural areas, although rural folk may be at higher risk due to their occupation or living conditions. Some of these misconceptions may lead many – including doctors – to believe that scrub typhus is an exotic new disease only affecting rural people in the hills or jungles.

Some media reports on scrub typhus are also misleading. Scrub typhus is related to rickettsia – a group of intracellular organisms transmitted by bites of ticks, lice, fleas or mites. Rickettsial infections include epidemic typhus spread by lice or spotted fever spread by ticks, and these have sometimes been confused by the media with scrub typhus.

It was epidemic typhus which killed Napoleon’s soldiers and not scrub typhus as reported. This distinction is important as scrub typhus, unlike epidemic typhus, is not contagious.

How to prevent scrub typhus 

Contact with the mite larvae can be prevented by not sitting or lying directly on the ground, or walking barefoot. Changing the clothes after the day’s work and a thorough wash also helps. Insect repellent creams may also be protective. Making our homes and surroundings less hospitable to rodents is advisable. Short-term prevention in soldiers and travelers can involve weekly administration of an antibiotic like doxycycline but is not recommended for long-term residents. There is no vaccine for scrub typhus.

As the season for scrub typhus approaches, we need to recognise it as a disease prevalent in rural and urban India, which is causing life-threatening illnesses. Doctors should keep this possibility in mind, examine carefully for the presence of eschar in all patients with acute febrile illness, pneumonia, altered consciousness and initiate therapy early in case clinical features are compatible and other diseases have been excluded. Measures to prevent bites are feasible and should be known to people at risk, especially to those who live in rural areas.

Anurag Bhargava is a professor of medicine at Yenepoya Medical College, Mangalore, has been trained at AIIMS, New Delhi and has worked at all levels of care across India for over 25 years. 

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