The tropical rat mite, Ornithonyssus bacoti, is a tiny parasitic arthropod that primarily feeds on the blood of rodents, particularly rats and mice. These mites are ectoparasites, meaning they live on the exterior of their hosts. While their preferred hosts are rodents, they will bite humans and other mammals when their primary food source becomes unavailable.
Identification and Lifecycle
The tropical rat mite, Ornithonyssus bacoti, is quite small, making it difficult to spot with the naked eye. Its size ranges from approximately 0.3 mm to 1.4 mm. These mites are generally translucent or grayish before feeding, but they become reddish-brown and more visible after consuming a blood meal.
The lifecycle of the tropical rat mite spans 11 to 13 days and includes five stages: egg, larva, protonymph, deutonymph, and adult. Female mites lay around 100 eggs in or near the host’s nest. Eggs hatch into larvae within one to four days, and only the protonymph and adult stages require blood meals for development. The entire lifecycle is completed on or near their rodent hosts.
Human Infestation and Symptoms
Human encounters with tropical rat mites usually occur when their primary rodent hosts are no longer available. This often happens if rats or mice die, are trapped, or abandon their nests in a building. The mites then disperse from the vacated nests, actively seeking a new blood meal. They can survive without a blood meal for nearly two weeks, or even up to six months in some cases, increasing the likelihood of human contact.
When tropical rat mites bite humans, they cause a condition known as rat mite dermatitis. Symptoms often include intense itching, which can be severe, along with the appearance of small, red bumps or papules on the skin. These bites may resemble mosquito bites and can appear in clusters, commonly found on the upper extremities, neck, upper trunk, and face, or in areas where clothing constricts. Tropical rat mites cannot survive or reproduce on human blood. They are not known to transmit diseases to humans.
Eradication Process
Eliminating a tropical rat mite infestation requires a two-step approach that addresses both the mites and rodents. The first step involves eradicating the rodent infestation. Simply treating for mites without removing the rodents will not provide a lasting solution, as new mites will continue to emerge from existing nests. Professional pest control services are recommended to locate and eliminate rats or mice from the property.
Once the rodent source has been removed, the second step focuses on treating the living space to eliminate the remaining mites. Thorough cleaning includes vacuuming all carpets, upholstered furniture, and along baseboards. All bedding, clothing, and other washable fabrics should be laundered in hot water to kill any mites present. Applying appropriate acaricides, which are mite-killing pesticides, to infested areas is also helpful. Professional pest control technicians can apply residual sprays or other treatments to manage the mite population.
Preventing Future Infestations
Preventing future tropical rat mite infestations centers on making your home less appealing and accessible to rodents. Sealing potential entry points is a primary measure, by inspecting and repairing cracks, gaps, and openings in the foundation, walls, and roofline. This includes ensuring that utility pipes, vents, and other structural elements are properly sealed to prevent rodent access.
Maintaining a clean and tidy property also discourages rodents. Regularly removing debris, such as piles of wood, old furniture, or overgrown vegetation, from around the house reduces hiding spots for rodents. Keeping vegetation trimmed back from the building’s exterior prevents rodents from using branches or vines to access the roof or upper levels. Additionally, securing trash cans with tight-fitting lids prevents rodents from accessing food sources.