Rat mites are external parasites primarily associated with rodents, yet their presence on humans is a common concern. These tiny creatures, though not typically interested in humans as primary hosts, can incidentally encounter people. Understanding how long these mites might persist on human skin is important for anyone who experiences their bites. While rat mites can cause temporary irritation, they do not establish long-term infestations on humans.
Rat Mites and Their Preferred Host
Rat mites, scientifically known as Ornithonyssus bacoti, are a type of mite commonly referred to as tropical rat mites. These arachnids are closely related to spiders and ticks, possessing eight legs in their adult stage. They are small, generally ranging from 0.75 to 1.5 millimeters in length, making them barely visible to the naked eye, though they may appear reddish after feeding on blood.
These mites are natural parasites of rodents, particularly rats such as the roof rat (Rattus rattus) and Norway rat (R. norvegicus), and also infest mice. They thrive in rodent nests, where they feed on the blood of their hosts and complete their life cycle, which typically lasts between 7 and 16 days.
Survival on Humans
Rat mites cannot survive or reproduce on humans long-term because humans are not their natural hosts. While they will bite humans to obtain a blood meal when their preferred hosts are unavailable, human blood is not sufficient for their nutritional needs to complete their life cycle. Consequently, these mites do not establish permanent infestations on human skin or in human environments.
When a rat mite bites a human, it is typically a temporary occurrence. The mites generally remain on a human for only a few hours to a day or two, rarely longer. Although some mites can survive for several weeks without a blood meal in their environment, they cannot continue their life cycle or lay eggs on a human host.
Impact of Rat Mite Bites on Humans
When rat mites bite humans, the immediate effects commonly include itching, discomfort, and the development of small, red bumps on the skin. These bites often appear as pimple-sized lesions, typically 1 to 4 millimeters in diameter, and can be intensely itchy. The irritation and rash that follow are primarily allergic reactions to the mite’s saliva injected during feeding.
Unlike some other types of mites, rat mites do not burrow into human skin. While uncomfortable, these bites are not considered medically serious. Rat mites are not known to transmit diseases to humans. Bites can occur anywhere on the body, but are sometimes concentrated in areas where clothing fits tightly, or on the neck, upper trunk, and extremities.
Understanding Infestation Source
Rat mites primarily infest homes or other structures when their usual rodent hosts are present. The most common scenario leading to human encounters occurs when the rodent population either dies, abandons its nests, or is eradicated.
When their primary food source is gone, the mites disperse from empty nests or dead hosts in search of new blood meals. Humans are then incidentally encountered as the mites seek any warm-blooded creature. Mites are attracted to cues like carbon dioxide and body heat, drawing them towards areas of human activity within a building, such as bedrooms or living spaces. This explains why people might suddenly experience bites without ever seeing the rodents themselves.