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Chigger Bites

Updated : January 4, 2024





Background

Chigger is the generic term for mites of the Trombiculid group. Bites from these mites’ larvae can produce local pruritus & discomfort. This is referred to as trombiculiasis & trombiculosis. The reaction is usually moderate & self-limiting, although bites can occasionally transmit infection or cause a microbial superinfection. While there are many parasitic mite species in various settings around the world, the species most termed as chiggers comprise Eutrombicula alfreddugesi in the southern US, Trombicula autumnal in Europe, & Leptotrombidium species in Oceania & Asia.

This species’ larvae depend on the skin of various ranges of mammals, especially humans. Adult mites dig into the earth & feed on trash, while larvae collect on the margins of grass and leaves before latching on to a traveling host. They then travel to a favorite feeding place, attach to the host’s skin, and exude proteolytic enzymes that disintegrate the host’s epidermis. This causes an inflammatory process characterized by surrounding erythema, different degrees of swelling, & extreme itching.

Although the larvae are easily dislodged by scratching & rarely remain attached to humans for more than two days, the extreme pruritus, swelling, & localized allergic reaction can linger for weeks. On the skin, a light–red–orange–colored larva about 0.15 – 0.3 mm in length may be detected. Typically, trombiculiasis is diagnosed based on interaction with a trombiculid environment, the appearance of the lesions, as well as the elimination of other probable illnesses.

Epidemiology

Larval mites reach their parasitic stage in the Northern Hemisphere between September and June. As a result, nearly all cases of trombiculiasis occur throughout the summer & fall. However, in tropical places around the world, exposure can happen at any moment of the year. Chigger bites can develop in people of all ages who have previously been exposed to chigger environments.

Overgrown fields, forested areas, or damp soil near bodies of water are examples of these ecosystems. Trombiculiasis has typically been connected with harvest workers’ job exposure; however, it can also develop in suburban or metropolitan regions where there is visibility to a grassy field, garden, or an overgrown lawn. As a result, the true prevalence of trombiculiasis is unknown & limited to incident reports.

This is largely owing to the disease’s self-limiting character, which generally leads to underrepresentation. Chiggers are known human vectors of scrub typhus. The bacteria Orientia tsutsugamushi causes scrub typhus. The risk of disease in urban contexts is not well established; nevertheless, a recent Thai study discovered an elevated incidence of chigger infection (76.8%) in animals caught in Bangkok’s urban city parks. However, they found no O. tsutsugamushi in their research.

Chigger-associated scrub typhus is found all over the world. It was formerly considered to occur primarily in the Asian-Pacific region & northern Australia, dubbed the “Tsutsugamushi Triangle.” Nonetheless, observations of scrub typhus in southern Chile and Africa have expanded the disease’s endemic range. A recent study in North Carolina, USA, found Rickettsia disease in chiggers.

Anatomy

Pathophysiology

Trombiculid mites enter human skin through direct contact with open sleeves, pant cuffs, and shirt collars. The larvae then travel over the skin’s surface. Limitations to migration, including a belt and elastic waistline, lead larvae to congregate in these places. They produce digestive enzymes once hooked to the skin in order to liquefy the epidermis for eating. This causes discomfort & inflammation at the location of the bite.

The area around the wound would become inflamed as the larva mite liquefies the epidermis. This causes a papule to grow around the mite, giving the impression that it has burrowed into the dermis. The mite may be observed on the inside of the papule at times, but it will be going to be dislodged by the time the irritation occurs. The pruritus normally goes away after a few days, although it can continue for up to 2 weeks.

Chigger bites cause erythematous papules, which can appear in clusters. Surrounding vesicles, macules, and, in rare cases, bullae may form. Since mites travel on the host’s body to a sheltered location with the epidermis, they frequently congregate along the edges of closely fitting garments. Numerous bites may occur in a linear pattern along the waistline, the in-seam of underwear, or on top of socks and shoes.

Etiology

Trombiculiasis is formed by the biting of trombiculid parasites & needs exposure to the larval mites’ preferred habitat. When bitten, the mite’s digestive enzymes cause liquefaction of the recipient’s epidermis, resulting in a regional hypersensitivity response. This results in the characteristic erythema, papules, & urticaria.

Genetics

Prognostic Factors

As long as there is no re-exposure, trombiculiasis will usually resolve in a couple of weeks in the majority of cases. In general, the chance of superimposed pathogenic bacteria or the spreading of other bacterial infections is quite minimal. As a result, the prognosis for chigger bites is almost always favorable.

If re-infection is possible, the physician should advise the patient to avoid chigger environments, cover the skin when traveling through infested regions, or use repellents and pesticides to avoid contamination.

Clinical History

Clinical history

A clinical history of chigger bites includes gathering information about the patient’s recent exposure to potential chigger habitats and the onset and characteristics of the symptoms.

The healthcare provider may ask the patient about:

  • Exposure to chigger habitats: Chiggers are most commonly found in grassy or wooded areas, so the healthcare provider may ask if the patient has recently spent time in these environments, such as camping, hiking, or gardening.
  • Timing of symptoms: Chigger bites typically take several hours to develop after exposure, so the healthcare provider may ask when the patient first noticed the symptoms.
  • Symptoms: The healthcare provider will ask about the specific symptoms experienced by the patient, such as red, itchy welts on the skin, and any associated symptoms like fever, fatigue, or joint pain.
  • Location of bites: Chigger bites tend to occur in clusters around the ankles, waist, groin, and armpits, so the healthcare provider may ask about the specific location of the bites.
  • Other possible exposures: The healthcare provider may also ask about other possible exposures to insect bites or skin irritants, such as mosquito bites or exposure to poison ivy.

A thorough clinical history can help the healthcare provider make an accurate diagnosis of chigger bites and provide appropriate treatment recommendations.

Physical Examination

Physical examination

During a physical examination of chigger bites, the healthcare provider will typically inspect the affected areas for the characteristic signs of chigger bites, including:

  • Red, raised welts: Chigger bites are typically characterized by red, raised welts on the skin, which can be very itchy.
  • Clusters of bites: Chigger bites often occur in clusters or groups on the skin, as the larvae tend to feed in close proximity to each other.
  • Location: Chigger bites are most commonly found in areas of the body where the skin is thin or folds, such as around the ankles, waist, groin, and armpits.
  • Timeframe: The healthcare provider may also ask about the timing of the onset of symptoms, as chigger bites typically take several hours to develop after exposure to the larvae.

In addition to a physical examination, the healthcare provider may also take a detailed medical history and ask about recent travel, outdoor activities, and any other symptoms or concerns. If there is any uncertainty about the diagnosis or treatment, the healthcare provider may order further tests or refer the patient to a specialist.

Age group

Associated comorbidity

Associated activity

Acuity of presentation

Differential Diagnoses

Differential diagnosis

The differential diagnosis of chigger bites includes other conditions that can cause similar symptoms, such as:

  • Mosquito bites: Mosquito bites can cause red, itchy welts on the skin, similar to chigger bites. However, mosquito bites are often more widespread and can occur on any part of the body.
  • Flea bites: Flea bites are another common cause of red, itchy welts on the skin and can often be found around the ankles and legs. However, flea bites can also occur on other parts of the body.
  • Poison ivy/oak/sumac: These plants can cause a red, itchy rash on the skin, which may resemble chigger bites. However, the rash is usually more widespread and can occur anywhere the plant has come into contact with the skin.
  • Scabies: Scabies is a skin condition caused by the Sarcoptes scabiei mite, which can cause intense itching and a red, bumpy rash. The rash is often found in the folds of the skin, such as between the fingers, around the waist, and in the genital area.
  • Eczema: Eczema is a chronic skin condition that can cause red, itchy, and scaly patches on the skin. These patches can occur anywhere on the body and can be triggered by a variety of factors, including stress and allergies.

If you suspect you have been bitten by chiggers, it is important to consult with a healthcare provider to rule out other possible causes and receive appropriate treatment.

Laboratory Studies

Imaging Studies

Procedures

Histologic Findings

Staging

Treatment Paradigm

Chigger bite treatment focuses on symptom management with antihistamines or external corticosteroid creams. Cold compresses also help relieve pain & regional edema. There is no place for suffocating the parasite by covering the bite in nail paint, vaseline, and cream. Itching can be relieved with menthol and calamine cream applied topically.

Strong external corticosteroids with occlusion can be administered in extreme situations. If topical treatment fails, triamcinolone acetonide intralesional steroid injections might be utilized. But, in the majority of instances, this is unneeded. To prevent larvae, exposed garments should be cleaned in hot water and treated with pesticides. Doxycycline is used to treat scrub typhus.

by Stage

by Modality

Chemotherapy

Radiation Therapy

Surgical Interventions

Hormone Therapy

Immunotherapy

Hyperthermia

Photodynamic Therapy

Stem Cell Transplant

Targeted Therapy

Palliative Care

Medication

Media Gallary

References

https://www.ncbi.nlm.nih.gov/books/NBK538528/

Chigger Bites

Updated : January 4, 2024




Chigger is the generic term for mites of the Trombiculid group. Bites from these mites’ larvae can produce local pruritus & discomfort. This is referred to as trombiculiasis & trombiculosis. The reaction is usually moderate & self-limiting, although bites can occasionally transmit infection or cause a microbial superinfection. While there are many parasitic mite species in various settings around the world, the species most termed as chiggers comprise Eutrombicula alfreddugesi in the southern US, Trombicula autumnal in Europe, & Leptotrombidium species in Oceania & Asia.

This species’ larvae depend on the skin of various ranges of mammals, especially humans. Adult mites dig into the earth & feed on trash, while larvae collect on the margins of grass and leaves before latching on to a traveling host. They then travel to a favorite feeding place, attach to the host’s skin, and exude proteolytic enzymes that disintegrate the host’s epidermis. This causes an inflammatory process characterized by surrounding erythema, different degrees of swelling, & extreme itching.

Although the larvae are easily dislodged by scratching & rarely remain attached to humans for more than two days, the extreme pruritus, swelling, & localized allergic reaction can linger for weeks. On the skin, a light–red–orange–colored larva about 0.15 – 0.3 mm in length may be detected. Typically, trombiculiasis is diagnosed based on interaction with a trombiculid environment, the appearance of the lesions, as well as the elimination of other probable illnesses.

Larval mites reach their parasitic stage in the Northern Hemisphere between September and June. As a result, nearly all cases of trombiculiasis occur throughout the summer & fall. However, in tropical places around the world, exposure can happen at any moment of the year. Chigger bites can develop in people of all ages who have previously been exposed to chigger environments.

Overgrown fields, forested areas, or damp soil near bodies of water are examples of these ecosystems. Trombiculiasis has typically been connected with harvest workers’ job exposure; however, it can also develop in suburban or metropolitan regions where there is visibility to a grassy field, garden, or an overgrown lawn. As a result, the true prevalence of trombiculiasis is unknown & limited to incident reports.

This is largely owing to the disease’s self-limiting character, which generally leads to underrepresentation. Chiggers are known human vectors of scrub typhus. The bacteria Orientia tsutsugamushi causes scrub typhus. The risk of disease in urban contexts is not well established; nevertheless, a recent Thai study discovered an elevated incidence of chigger infection (76.8%) in animals caught in Bangkok’s urban city parks. However, they found no O. tsutsugamushi in their research.

Chigger-associated scrub typhus is found all over the world. It was formerly considered to occur primarily in the Asian-Pacific region & northern Australia, dubbed the “Tsutsugamushi Triangle.” Nonetheless, observations of scrub typhus in southern Chile and Africa have expanded the disease’s endemic range. A recent study in North Carolina, USA, found Rickettsia disease in chiggers.

Trombiculid mites enter human skin through direct contact with open sleeves, pant cuffs, and shirt collars. The larvae then travel over the skin’s surface. Limitations to migration, including a belt and elastic waistline, lead larvae to congregate in these places. They produce digestive enzymes once hooked to the skin in order to liquefy the epidermis for eating. This causes discomfort & inflammation at the location of the bite.

The area around the wound would become inflamed as the larva mite liquefies the epidermis. This causes a papule to grow around the mite, giving the impression that it has burrowed into the dermis. The mite may be observed on the inside of the papule at times, but it will be going to be dislodged by the time the irritation occurs. The pruritus normally goes away after a few days, although it can continue for up to 2 weeks.

Chigger bites cause erythematous papules, which can appear in clusters. Surrounding vesicles, macules, and, in rare cases, bullae may form. Since mites travel on the host’s body to a sheltered location with the epidermis, they frequently congregate along the edges of closely fitting garments. Numerous bites may occur in a linear pattern along the waistline, the in-seam of underwear, or on top of socks and shoes.

Trombiculiasis is formed by the biting of trombiculid parasites & needs exposure to the larval mites’ preferred habitat. When bitten, the mite’s digestive enzymes cause liquefaction of the recipient’s epidermis, resulting in a regional hypersensitivity response. This results in the characteristic erythema, papules, & urticaria.

As long as there is no re-exposure, trombiculiasis will usually resolve in a couple of weeks in the majority of cases. In general, the chance of superimposed pathogenic bacteria or the spreading of other bacterial infections is quite minimal. As a result, the prognosis for chigger bites is almost always favorable.

If re-infection is possible, the physician should advise the patient to avoid chigger environments, cover the skin when traveling through infested regions, or use repellents and pesticides to avoid contamination.

Clinical history

A clinical history of chigger bites includes gathering information about the patient’s recent exposure to potential chigger habitats and the onset and characteristics of the symptoms.

The healthcare provider may ask the patient about:

  • Exposure to chigger habitats: Chiggers are most commonly found in grassy or wooded areas, so the healthcare provider may ask if the patient has recently spent time in these environments, such as camping, hiking, or gardening.
  • Timing of symptoms: Chigger bites typically take several hours to develop after exposure, so the healthcare provider may ask when the patient first noticed the symptoms.
  • Symptoms: The healthcare provider will ask about the specific symptoms experienced by the patient, such as red, itchy welts on the skin, and any associated symptoms like fever, fatigue, or joint pain.
  • Location of bites: Chigger bites tend to occur in clusters around the ankles, waist, groin, and armpits, so the healthcare provider may ask about the specific location of the bites.
  • Other possible exposures: The healthcare provider may also ask about other possible exposures to insect bites or skin irritants, such as mosquito bites or exposure to poison ivy.

A thorough clinical history can help the healthcare provider make an accurate diagnosis of chigger bites and provide appropriate treatment recommendations.

Physical examination

During a physical examination of chigger bites, the healthcare provider will typically inspect the affected areas for the characteristic signs of chigger bites, including:

  • Red, raised welts: Chigger bites are typically characterized by red, raised welts on the skin, which can be very itchy.
  • Clusters of bites: Chigger bites often occur in clusters or groups on the skin, as the larvae tend to feed in close proximity to each other.
  • Location: Chigger bites are most commonly found in areas of the body where the skin is thin or folds, such as around the ankles, waist, groin, and armpits.
  • Timeframe: The healthcare provider may also ask about the timing of the onset of symptoms, as chigger bites typically take several hours to develop after exposure to the larvae.

In addition to a physical examination, the healthcare provider may also take a detailed medical history and ask about recent travel, outdoor activities, and any other symptoms or concerns. If there is any uncertainty about the diagnosis or treatment, the healthcare provider may order further tests or refer the patient to a specialist.

Differential diagnosis

The differential diagnosis of chigger bites includes other conditions that can cause similar symptoms, such as:

  • Mosquito bites: Mosquito bites can cause red, itchy welts on the skin, similar to chigger bites. However, mosquito bites are often more widespread and can occur on any part of the body.
  • Flea bites: Flea bites are another common cause of red, itchy welts on the skin and can often be found around the ankles and legs. However, flea bites can also occur on other parts of the body.
  • Poison ivy/oak/sumac: These plants can cause a red, itchy rash on the skin, which may resemble chigger bites. However, the rash is usually more widespread and can occur anywhere the plant has come into contact with the skin.
  • Scabies: Scabies is a skin condition caused by the Sarcoptes scabiei mite, which can cause intense itching and a red, bumpy rash. The rash is often found in the folds of the skin, such as between the fingers, around the waist, and in the genital area.
  • Eczema: Eczema is a chronic skin condition that can cause red, itchy, and scaly patches on the skin. These patches can occur anywhere on the body and can be triggered by a variety of factors, including stress and allergies.

If you suspect you have been bitten by chiggers, it is important to consult with a healthcare provider to rule out other possible causes and receive appropriate treatment.

Chigger bite treatment focuses on symptom management with antihistamines or external corticosteroid creams. Cold compresses also help relieve pain & regional edema. There is no place for suffocating the parasite by covering the bite in nail paint, vaseline, and cream. Itching can be relieved with menthol and calamine cream applied topically.

Strong external corticosteroids with occlusion can be administered in extreme situations. If topical treatment fails, triamcinolone acetonide intralesional steroid injections might be utilized. But, in the majority of instances, this is unneeded. To prevent larvae, exposed garments should be cleaned in hot water and treated with pesticides. Doxycycline is used to treat scrub typhus.

https://www.ncbi.nlm.nih.gov/books/NBK538528/

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