Thursday, 13 June, 2024

Scrub Typhus: A Neglected Illness

Prof. Dr. Shyam P Lohani

A series of news reports have recently been published in broadsheet newspapers and social media about the outbreak of the bacterial disease known as Scrub typhus in Nepal. Oftentimes, the news reports have caused panic among general population and portrayed the disease as of epidemic proportion. However, this particular disease can effectively be cured with the available antibiotics. Scrub typhus is one of the most under-reported and misdiagnosed febrile illnesses that might require patients to be hospitalised.

The disease is caused by Orientia tsutsugamushi and endemic to many countries around the world, including Nepal. It is an acute febrile illness caused by gram negative bacteria. In 2015, the presence of Scrub typhus was officially confirmed in Nepal with 101 cases from 16 districts and eight deaths. The next outbreak was recorded in 2016 with 800 cases in 47 districts with 14 deaths (NHRC, 2017). In 2019, this disease has been found in as many as 63 districts of the country and affected hundreds of Nepali people with three reported deaths already. The disease is spreading in many hilly districts in the recent times owing to climate change that favours vector propagation.
Scrub typhus was first described in China in 313 AD and was first isolated in Japan in 1930. Since then it has caused millions of cases throughout the world. Scrub typhus cases are mainly found in rural areas of Southeast Asia, China, Indonesia, Japan, and northern part of Australia and people with the history of travel to those areas. Before World War II, thousands of people died of Scrub typhus as there was no effective antibiotics were available.
Currently, it is estimated that about one million cases of scrub typhus occur annually and that as many as one billion people living in endemic areas may have been infected by O. tsutsugamushi at some point of time (Medscape, 2019). The pathogen, O tsutsugamushi, that causes Scrub typhus, is transmitted to humans through the bite of an infected chigger, the larval stage of Leptotrombidium mites. Wild rats serve as the natural reservoir for the chiggers and represent a risk factor for human infection, but they are rarely infected with O tsutsugamushi. When the chiggers feed on humans, infection occurs.
The behavioural factors such as taking a rest directly on the grass, working in short sleeves, working with bare hands, and squatting to defecate or urinate posed the highest risks. Scrub typhus affects people of all ages. Men and women are affected with equal frequency and no race-related differences in incidence have been found. However, in recent news from the western part of Nepal, more females are said to have contracted Scrub typhus which might be due to their working outside fields.
The chigger bite is often painless, unnoticed and inoculates the bacteria to human body. The bacteria are not transmitted from one person to another person. The incubation period lasts between 6 to 20 days with average duration of 10 days. After incubation, persons may experience symptoms such as headaches, shaking chills, lymphadenopathy, conjunctival infection, fever, body aches, muscle pain, anorexia, and mental changes ranging from confusion to coma. The fever usually of very high grade reaches up to 104-105°F. People with severe illness may develop organ failure and bleeding which is often fatal if untreated. At the site of bite, a small painless papule initially appears and enlarges gradually. An area of central necrosis develops and is followed by eschar formation. The eschar is well developed at the beginning of the fevers, which may lead the patient to seek for health care. The symptoms of scrub typhus are similar to many other illnesses, therefore, misdiagnosis is common and mismanagement may result in to complications. The illness is mild and self-limiting to fatal.

The diagnosis of the scrub typhus is usually made with the clinical manifestations by the health care providers. The history is very important for diagnosis as people who have spent time in the areas where Scrub typhus is found are likely to develop symptoms. Laboratory testing can take several weeks; therefore, health care providers may start the treatment before laboratory result is available. The antibiotic, doxycycline, is effective for the management of scrub typhus and should be started as early as scrub typhus is suspected. This antibiotic can be given to people of all ages.
No vaccine is available for scrub typhus. Therefore, avoiding the contact with infected chiggers is the best approach to prevention. When traveling or working in the areas of lots of vegetation or brush where chiggers are found, appropriate personal protective clothing such as long shirts and pants, long boots should be used. The use of insect repellent such as product with 20-30 per cent DEET is recommended. The repellent should not be sprayed under the clothing. The synthetic pyrethroids such as permethrin kill chiggers and can be used to treat boots, clothing, and other personal protective equipment. The permethrin based product should not be used directly on the skin and is for treating cloths only. The countrywide awareness campaign targeting general public about the protective clothing as well as use of repellent treated clothing is the keys in preventing Scrub typhus.

(Prof. Lohani is the Clinical Director of the Nepal Drug and Poison Information Centre and
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