Chiggers are tiny, six-legged larval mites that can cause itchy red welts on the skin. These arachnids, more closely related to spiders and ticks than to insects, are commonly known as red bugs or harvest mites. While their bites are irritating, the idea that chiggers “spread” in a contagious manner from person to person is a common misunderstanding.
How Chiggers Transfer to Hosts
Chiggers are parasitic only in their larval stage. These larvae are very small, typically measuring between 0.15 to 0.3 millimeters, and are yellowish to light-red in color. They do not fly or jump; instead, they wait on vegetation, such as tall grasses, weeds, or leaf litter, usually close to the ground. When a host, like a human or animal, brushes past, the chiggers quickly transfer onto them.
Upon landing on a host, chiggers crawl before selecting a feeding site, preferring areas where clothing fits tightly or where the skin is thin and moist. Common attachment sites on humans include ankles, waistbands, behind the knees, and armpits. Chiggers do not burrow into the skin or feed on blood; rather, they inject digestive enzymes that break down skin cells, which they then consume. This process causes the itchy welts, and once fully fed, the larva detaches and drops off to continue its life cycle in the environment.
Do Chiggers Spread Between People or Pets?
Chiggers do not spread from person to person or from pets to people. Once a chigger larva has attached to a host and begun feeding, it remains on that host until it is fed and detaches naturally. They do not leave one host to seek another. Direct contact with someone who has chigger bites or a pet with chiggers will not result in new infestations.
The bites appear in clusters, particularly around areas of tight clothing, leading some to believe they have spread. However, these clusters simply indicate multiple chiggers attached to a host from the environment in the same area. After feeding and detaching, the chigger continues its life cycle on the ground, developing into a non-parasitic nymph and then an adult mite that feeds on small insects and insect eggs.
Disease Transmission by Chiggers
While chigger bites cause irritation, North American chiggers are not known to transmit diseases to humans. The itching and skin reactions are due to the digestive enzymes injected by the chigger larvae. Scratching the bites can sometimes lead to secondary bacterial infections, but this is a result of broken skin, not direct pathogen transmission by the chigger itself.
Globally, certain species of chiggers found in parts of Asia and the Pacific Islands can transmit the bacterium that causes scrub typhus. This condition can be life-threatening if untreated, presenting with symptoms like fever, headache, and a skin lesion. However, this disease risk is specific to geographical regions outside of North America.
Where Chiggers Live and Thrive
Chiggers are widely distributed globally but thrive in specific environmental conditions. They are most commonly encountered in areas with dense vegetation, such as tall grasses, weeds, brushy fields, and wooded edges. Moist, shaded environments, including leaf litter and areas near natural bodies of water, are favorable habitats for chiggers.
Chigger activity is dependent on temperature and humidity. They are most active during warm weather, from late spring through early fall. They become inactive in colder temperatures. This preference for warm, humid, and vegetated areas explains why people often encounter them when recreating outdoors.