What Is Scrub Typhus? Symptoms of Chigger Bites and High-Incidence Areas

Recently, hot and rainy weather has prevailed in many places, marking the peak season for scrub typhus. Chiggers (yàng chong), also known as scrub mites or sand mites, have been responsible for repeated cases of chigger bites leading to death in various places in recent years, with June—September being the peak period for chiggers each year. So what is scrub typhus? What symptoms appear after a chigger bite? Where are they generally found?

Chiggers can transmit scrub typhus. This disease was first discovered and recorded by the Chinese scientist Ge Hong of the Jin Dynasty (313 AD). In animal classification, chiggers belong to the phylum Arthropoda, class Arachnida. More than 3,000 species of chiggers are known worldwide, and over 350 species have been recorded in China. Common species in South China include Leptotrombidium deliense, Leptotrombidium akamushi, and Eushoengastia indica. Their greatest morphological difference from insects is that adults have 4 pairs of legs rather than 3. Therefore, calling them “small insects” is inaccurate. The pathogen transmitted by chiggers is Orientia tsutsugamushi, a microorganism between bacteria and viruses in nature.

What is scrub typhus?

Scrub typhus is an acute natural focal infectious disease transmitted to humans through chigger larvae. Clinically, it presents as an ulcer or eschar at the bite site, sudden high fever, rash, enlarged lymph nodes, and enlarged liver and spleen. Severe cases present with serious multi-organ damage, including heart, liver, and kidney failure. Recently, as Foshan enters summer with hot and rainy weather, it is the peak season for scrub typhus.

Where are chiggers generally found?

Currently, chiggers are mostly distributed in tropical and subtropical coastal areas of China such as Hainan, Guangdong, Guangxi, and Fujian. They mostly live in damp grasslands and forests, and are more active in spring and summer. They absorb toxins by biting rats, goats, and other animals, then transmit the toxins to humans, spreading through the bloodstream.

What symptoms appear after a chigger bite?

1. When a chigger bites a person, it releases an enzyme that numbs them, so the person feels no pain during the bite. In addition to red eyes, scrub typhus causes skin redness and swelling, enlarged and painful lymph nodes near the bite site, numbness in the limbs, nausea, and drowsiness. After being bitten, persistent high fever, an eschar on the body surface, and corneal congestion may occur.

2. Chiggers prefer to bite moist areas of the body, such as the armpits, under the breasts, the perineum, and the back. After being bitten, an eschar forms, which is the hallmark of scrub typhus. Fever and headache are early manifestations of scrub typhus. As the disease progresses, the patient may develop skin congestion and even bleeding, and in severe cases, multiple organ failure and even death.

What to do after a chigger bite

Currently, cases of multiple organ failure ultimately leading to death due to scrub typhus are very rare, and the vast majority of patients have mild symptoms. Antibiotics such as tetracycline and chloramphenicol have a specific effect on scrub typhus. If treated early, it is not difficult to treat and the results are very good. After being bitten, patients should rest in bed, drink plenty of water, eat liquid or soft food, pay attention to oral hygiene, and keep the skin clean.

However, many scrub typhus patients confuse their symptoms with an ordinary cold or fever, thinking they will be fine after taking some medicine, which delays the condition and eventually leads to severe illness. If a patient only starts proper treatment three to four weeks after onset, the treatment results are poor, triggering failure of multiple organs including the kidneys, lungs, liver, and heart, and even death.

Therefore, if a chigger bite is discovered, the correct approach is to immediately seek help from the infectious disease department of a hospital. Do not handle it yourself, to avoid causing further infection.

How to prevent scrub typhus?

When traveling, enjoying spring outings and flowers, or going out at night to cool off, there are too many small bugs in the grass, and chiggers are one of the very dangerous ones. Here we remind everyone that scrub typhus chiggers mostly grow in damp and shady areas such as ponds, paddy fields, and grass, and reproduce most actively during the 1 week after the rainy season ends.

1. When playing or working in grass or fields, it is best to wear long sleeves and long pants, tighten the cuffs, collar, and pant legs, and apply insect repellent to the cuffs, collar, and exposed skin.

2. In the first few days after rain when it just clears up, it is best not to sit on the grass.

3. After field work, promptly shake out and change clothing, place them separately, wash them, and take a shower in time.

4. Children are easily overlooked after being bitten, which can then lead to severe illness, so parents should take even more preventive measures.

Doctor's reminder

The first symptom of scrub typhus is high fever, which patients easily mistake for a cold and ignore or delay treatment. Chigger larvae bites are also more commonly found in hidden, moist, sweaty areas such as the armpits, groin, perineum, perianal area, and lower back, making the eschar (or ulcer) difficult to find. When a patient cannot clearly describe their medical history, it is also easily misdiagnosed.

Therefore, if residents develop a high fever of unknown cause after outdoor activities, they should be alert to whether they have contracted scrub typhus, carefully check their body for an eschar from an insect bite, and seek medical attention as soon as possible.