Scrub Typhus Symptoms: Early Signs of Tick-Borne Infections

Scrub Typhus Symptoms: Identifying Tick-Borne Bacterial Infection

Scrub typhus symptoms are caused by a bacterial infection that primarily affects endothelial cells. This causes instant inflammation and leads to a dark, scab-like lesion at the bite site. Eschar (a dark, scab-like lesion) is a hallmark of scrub typhus but may not be present in all patients. Its visibility can vary based on skin tone and bite location. Antibiotics like doxycycline are the first preferred choice of doctors in treating this infection.

Scrub typhus is a serious bacterial infection that spreads through bites from infected chiggers (mite larvae). The bacteria Orientia tsutsugamushi are the main causative agent of this serious condition. It is not contagious and does not spread directly from one individual to another. Scrub typhus is increasingly reported in India, especially in endemic regions, but exact annual case numbers vary due to underdiagnosis and limited surveillance.

Here we will delve into a detailed discussion regarding various scrub typhus symptoms and diagnostic tests to identify tick-borne infections. Additionally, this article will highlight specific treatment approaches to treat this tick-borne infection.

What are the symptoms of scrub typhus?

Scrub typhus typically begins with fever, chills, headache, and swollen lymph nodes. In this section, we will discuss the symptoms of scrub typhus in adults and children. These include:
    

• Fever: It is the hallmark of scrub typhus symptoms, especially in children and adults. It mainly transmits through chiggers, which triggers an inflammation response in the body, leading to high fever, with a temperature more than 104℉. The onset of fever is an inflammatory response, a key part of the body’s defence mechanism. Many individuals experience chills and body aches along with fever after a few days of the onset of infection.
• Chills and Body Aches: Scrub typhus causes body aches, or myalgia, due to inflammation of the blood vessels. The bacteria Orientia tsutsugamushi cause vasculitis (inflammation of blood vessels) and surrounding tissues, which can lead to pain and discomfort throughout the body. The inflammation can affect various organs and tissues, including muscles, and cause aches.
• Headache: The bacterium which causes scrub typhus directly invades the central nervous system and the body’s inflammatory response. It can directly infect and damage brain cells, leading to common scrub typhus symptoms like severe headache and rash. Additionally, the infection can trigger inflammation in the brain and other surrounding tissues, further contributing to headaches.
• Eschar: Scrub typhus causes eschars (black, scab-like lesions) at the site of the chigger bite. This occurs due to the multiplication of the bacterium within the skin cells, leading to subsequent tissue damage. These bacteria multiply at the bite site, leading to the formation of a papule that ulcerates and becomes necrotic, eventually forming the characteristic eschars.
• Respiratory Problems: It occurs as the bacterium causes chronic inflammation and damage to the respiratory system. The inflammation, along with potential damage to delicate lung tissues, including blood vessels and air sacs, disrupts normal lung function. This can range from mild bronchitis and pneumonia to severe acute respiratory distress syndrome (ARDS).
• Gastrointestinal Issues: Scrub typhus triggers systemic vasculitis, which can impact various organs, including the gastrointestinal tract. The inflammation and damage to blood vessels in the stomach and intestines can lead to ulcers and erosions in the inner mucosal linings. These mucosal ulcers can become a source of bleeding, which may manifest as haematemesis.
• Mental Changes: The bacteria also exhibit neurotropic effects, which means they can directly affect the brain and nervous system. It can easily cross the blood-brain barrier and invade the brain tissues, leading to various neurological issues and mental changes. The bacteria multiply and can have a direct impact on normal brain function, causing cognitive decline.
• Heart Problems: The scrub typhus bacterium can infect the heart muscle, causing myocarditis (inflammation of the heart muscle). This inflammation can weaken the heart’s ability to pump blood effectively, potentially leading to heart failure. It can also cause vasculitis in those blood vessels that supply blood to the heart, causing reduced blood flow and eventually serious heart problems.

How to Diagnose Scrub Typhus?

Diagnosis of scrub typhus relies on a combination of clinical suspicion and laboratory testing. Clinical suspicion arises from a history of recent travel to endemic areas, exposure to chiggers, and characteristics of scrub typhus. Apart from these, there are various laboratories that confirm the presence of infection in the blood sample. These include:

• Indirect Immunofluorescence Antibody (IIFA) Test: This serological test is the gold standard for detecting antibodies to Orientia tsutsugamushi. It is a time-consuming method that requires specialised equipment and expertise. This test detects the specific antibodies in a patient’s serum that primarily bind to the bacterial antigens on a slide.
• Enzyme-linked Immunosorbent Assay (ELISA): The IgM ELISA test detects antibodies in human serum or plasma, indicating a potential active or recent scrub typhus infection. It detects IgM antibodies within the sample, where high levels indicate a potential active or recent infection. Antibodies in the sample bind to specific antigens, and a subsequent reaction with an enzyme-conjugated antibody produces a detectable colour change.
• Immunochromatographic Tests (ICTs): An ICT is a rapid, point-of-care method for diagnosing scrub typhus. It detects antibodies against the bacterium present within the human plasma or serum. This test utilises a lateral flow, immunochromatographic assay, where a sample on the device binds with the antibody, producing many coloured bands, indicating a possible infection.
• Weil-Felix Test: Weil-Felix is historically used but is now considered unreliable. ELISA and IFA are preferred for accurate diagnosis. This test relies on cross-reactivity between rickettsial antigens and those of certain Proteus antigens. If the patient’s blood contains antibodies against Rickettsia, they will react with the corresponding Proteus antigens, causing agglutination (clumping).

What are the treatments for scrub typhus?

Doctors primarily treat scrub typhus with antibiotics to inhibit the growth and multiplication within the body. Doxycycline is the drug of choice for most patients, and doctors administer this orally to them until the fever subsides. Apart from this, other antibiotics are used to manage scrub typhus signs and symptoms. These include:

• Azithromycin: It is an alternative for patients who cannot take doxycycline due to allergic responses.
• Chloramphenicol: This is another alternative for managing symptoms of scrub typhus, particularly if other antibiotics are not suitable.
• Rifampin: Doctors generally recommend this, especially where resistance to other antibiotics is a concern.
   

What are the preventive measures for scrub typhus?

Preventive measures for scrub typhus include wearing protective clothing, using insect repellents, avoiding infested areas, and maintaining cleanliness. Specifically, wearing long-sleeved clothes, applying DEET-based repellents, and avoiding going to grassy or wooded areas can help minimise exposure to mites that carry the bacterial strain.

In some cases, you can use insecticides to control mite populations in specific areas. However, you must consult with professionals to avoid any potential risks of contamination and toxin exposure.

Final Words

Scrub typhus usually occurs in Asia-specific regions due to the optimum climate and fluctuating temperatures. Larval mites can easily thrive in rural and suburban areas and affect at least 1 out of 10 individuals throughout the year. Common scrub typhus symptoms, such as potentially enlarged lymph nodes, can lead to complications like organ damage and severe bleeding if it is left untreated.