The term chigger bite refers to a parasitic infection caused by the species Penetrating tunga, a siphonapterous insect (flea) that burrows into the skin of the host’s feet, acting as an intraepidermal ectoparasite. This pathogen is associated with poverty and its prevalence in endemic areas ranges from 15% to 55%.
The bite of the chigger causes tungiasis, a disease included in the group of neglected tropical diseases (NTDs), which affect more than 1,000 million poor people living in warm and temperate regions each year. If you want to know more about this condition, read on.
What are chiggers and where are they found?
The terms chiggers AND spite refer to the same species: Penetrating tunga. As stated in the magazine Peruvian Dermatology, The first news of this species dates back to 1526, when the Spanish colonist González Fernández de Oviedo y Valdés reported this clinical picture in the conquerors located in Haiti in his diary.
The insect is part of the order siphonacteria, which includes fleas, the hematophagous (blood-feeding) external parasites irradiated in 1,900 different species. Because of their close contact with the circulatory systems of various hosts, many of these invertebrates are vectors of diseases such as typhus, plague and tapeworms.
For his part, Penetrating tunga it is the smallest flea that exists, with only 1mm in total length. It is also distinguished by its general habits, as it is capable of infecting 26 species of mammals divided into 5 different genera, while most of the species of the genus Tunga They have only one host, at most 2.
As indicated by the portal Orpha.net, The chigger is one of the few ectoparasites that have spread from the western to the eastern hemisphere, as in the past, infection was limited to the Americas only. Today this species is endemic to 88 different countries, including parts of the Caribbean, Central and South America, Africa and India.
Anyway, It should be noted that the prevalence is highly variable, depending on the area consulted. For example, in hyperendemic regions (where chigger is abundant) it is estimated that up to 50% of the population may be infected. In countries such as Colombia, on the other hand, 3 to 8 patients are reported for every 1,000 inhabitants.
How do chicks bite us? its life cycle
THE Centers for Disease Control and Prevention (CDC) show us, in detail, the life cycle of chicks. Among all the parasitic phases of this invertebrate, we point out the following:
- Chigger larvae are born in the environment, after an incubation period of 3-4 days. These tiny organisms go through 2 different larval stages until they enter the pupal stage, which lasts 3 to 4 weeks.
- One month after its formation, an adult, male or female, emerges from each cocoon. Specimens actively seek out warm-blooded animals to parasitize, as this fluid is their only food. Both males and females bite, but only the latter burrow under the skin.
- After cutting, Fertilized females burrow into the host’s epidermis. which causes inflammation in the form of a nodule. They are made in the granular layer of the skin and only the anus is visible and connects the animal to the outside.
- The females, having settled in the tissue of the host and nourished by its blood, begin to expel the eggs, as they have been fertilized by the males before burying themselves in the human skin. Over a period of 7 to 10 days they are capable of producing up to 200 eggs every 24 hours.
- After 2 weeks, female fleas die and shed their host skin. In any case, they have fulfilled their mission of effectively expanding the eggs through the center.
The moment of the bite
Most chicks perch on soles of feet, because his ability to jump is very small. There is no specific time when the bite occurs. It is enough to walk barefoot in a hyperendemic area to risk contracting tungiasis.
Furthermore, as indicated in art PLOS Neglected tropical diseasesTunga penetrans It is one of the few ectoparasites capable of completing its entire life cycle without leaving the host’s home. A person may release eggs between cracks in the floor of the house, and the larvae do well with minimal amounts of organic matter. For this reason, chigger bites can also occur inside the home.
How to recognize chigger bites?
At this point, it should be noted that what is causing the symptoms is not the parasite itself, but the reaction of the immune system against it. Localized acute inflammation (in the form of erythema, edema, pain, and pruritus) appears, caused by the growth of a foreign element within the host’s skin.
In addition to this, the Journal of the Institute of Tropical Medicine of São Paulo indicates that the parasite is directly visible. The female buried under the skin experiences a distinct hypertrophic growth, which is why she goes from 1 millimeter to 1 centimeter in size.
Several stages of the bite can be distinguished:
- Phase I: A 1 mm long red dot appears 30 minutes to a few hours after the bite.
- Phase II: 1 or 2 days after penetration, a noticeable whitish nodule begins to form under the skin, indicating chick growth. The parasite’s anal opening appears as a black dot in the center of the nodule; something similar to a pimple, but much more painful and itchy.
- Phase III: from 3 days to 3 weeks. The lesion is grossly evident and the subcutaneous nodule cannot be ignored.
- Once the chick dies, a black scab formed by coagulated blood and debris appears. This evolves over time to leave a superficial epidermal scar.
In 95% of cases this flea choose the feet as the preferred site of encystment. It has a predilection for the soles of the feet, the edges of the nails and the plantar surface of the toes. In the remaining 5% of cases it can happen on the hands.
At this point, it should be noted that there is no diagnostic test that reliably identifies tungiasis caused by a chigger bite. The fact that the patient has been (or resides) in one of the endemic regions — and has the above symptoms — is sufficient to initiate treatment.
Possible complications
One of the major points of research currently is the relationship of the chick to other microorganisms. As indicated by already cited sources, it is believed that Penetrating tunga may contain bacterial agents on or within its body surface. This would make it much easier for secondary infections to occur in hosts.
One of the more concerning microorganisms that could enter human skin with the flea is Clostridium tetanus. Infections secondary to chigger bites, therefore, can cause purulent events, skin ulcers, tissue necrosis, and even gangrene.
Chigger bite and its treatments
The first step in treating a chigger bite (and subsequent tungiasis) is surgically remove the parasite from the granular layer of the skin. Subsequently, the drug mupirocin 2% should be applied 2 times a day for 7-10 days. This is an antibacterial that prevents complications.
If the situation requires it, systemic antibiotics can also be administered. Additionally, special emphasis is placed on everyone in these regions receiving the tetanus vaccine, due to the chick’s close relationship to this organism.
You can imagine this clinical picture as a small pimple on the sole of the foot, but nothing is further from reality. A person may have multiple chiggers embedded in their foot and accessory infections, leading to necrosis, malodor, and putrefaction.
Prevention and recommendations
The main prevention against a chigger bite is to wear shoes at all times. Even so, in regions where the pathogen is endemic, very few people wear this garment. Ideally, these should be closed footwear (boots) and not sit or lie down on unfamiliar surfaces.
On the other hand, the United States National Library of Medicine recommends the application of topical DEET-type insecticides as an ancillary preventive method. These repellents need to be 30-50% concentrated to be effective without causing damage to the skin.
The chigger’s bite and socioeconomic reality
The chigger bite itself can be unpleasant, but the resulting tungiasis is much more worrying. Especially if the bacteria settle in the focus of the infection, the pathology can be complicated and put the patient’s life at risk.
It’s sad to see how something as simple as a pair of shoes can stop endemic events like this. Of course, this type of pathology makes us consider the context we have on the planet and become aware of the lack of resources in many populations.
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