Mouse mites

In the laboratory, true mites are also a common type of animal parasite. They may infest the surfaces or interiors of experimental animals, causing discomfort and health issues. Therefore, laboratories routinely conduct animal health monitoring and implement appropriate prevention and control measures.

True mites (Acarina) are a group of parasitic organisms belonging to the class Arachnida within the phylum Arthropoda. These tiny arthropods typically feed on plants, insects, birds, mammals, or other invertebrates, though some species also parasitize humans and mammals. They obtain nutrients by either feeding on their host's body fluids—either externally or internally—or by causing damage to the host's tissues. True mites are usually very small in size and difficult to spot with the naked eye, requiring a microscope to observe their intricate structures. Below, we provide an introduction to three mite species commonly studied in our laboratory:

● The experimental rodent fur mite is a type of mite that parasitizes laboratory animals such as mice and rats. This mite is scientifically named *Radfordia affinis* and belongs to the order Astigmata.

Here's a brief introduction to the experimental animal, the mouse ear mite:

● The rat mite is a tiny mite species that parasitizes rats. Belonging to the family Rhizoglyphidae, these mites typically inhabit the skin of rats or hide in their nests. Rat mites have an elongated, oval-shaped appearance, with bodies usually white or translucent. They feed by sucking the blood of rats and use the rats' skin and fur as shelter.

● Although rat mites typically do not pose a direct health threat to humans, they can sometimes transmit certain diseases. For instance, they may serve as vectors for the infection of *Myocoptes musculinus*, a parasitic mite that can cause parasitic infestations in humans. Moreover, the presence of rat mites can also indicate an indoor rodent problem, as their existence usually suggests that mice are actively present nearby.

● To avoid being affected by rat mites, you should first ensure that the indoor and surrounding environments are clean and hygienic. If rat mites are detected, avoid direct contact with the mites during handling.

*Neofeltria feldmani*, belonging to the family Feltriidae, is a mite that parasitizes the surfaces of insects and other invertebrates. It closely resembles the rat-mite in both morphology and setation pattern, though it can be distinguished by having two claws at the tips of its second pair of legs. Female mites measure 351 × 185 micrometers, while males are slightly smaller at 277 × 261 micrometers. The body of this mite is oval or elongated in shape, typically yellow or white in color. *Neofeltria feldmani* primarily feeds on organic matter such as bacteria, molds, and fungi found on the surfaces of its hosts.

● Pseudoladefem is a type of stoma mite, characterized by their unique stomatal structures that enable them to breathe through these openings. They parasitize insects at various life stages—such as pupae, larvae, and adults—and feed by extracting the host's bodily fluids and secretions. Typically, Pseudoladefem mites lay eggs on the surface of their hosts and spread to new hosts either through direct or indirect contact.

● Phytoseiulus mites do not pose a direct health threat to humans, as they typically coexist with insects and other invertebrates. However, in certain situations, if the population of Phytoseiulus mites becomes excessively large, they may still affect their hosts—for instance, by damaging the insects' appearance or compromising their overall health.

● Understanding and controlling the Radopholus similis nematode typically involves studying the ecology and behavior of its host, as well as implementing appropriate measures to reduce their population. This includes maintaining a clean environment, minimizing habitats for insects and invertebrates, and employing suitable chemical or biological control methods to manage their numbers. When managing nematodes, it’s important to prioritize products that are highly safe, non-toxic, or low in toxicity, and to carefully follow proper application guidelines. Importantly, ensuring the health and welfare of animals is absolutely critical; therefore, when conducting scientific experiments, researchers must guarantee that animals receive adequate care and protection. In addressing issues related to experimental animal mites like Radopholus similis, it’s essential to consult relevant guidelines on laboratory animal protection and ethics, and to adhere strictly to established regulations governing laboratory animal management.

The body length of the experimental animal, the rat mite, is approximately 0.3 to 0.5 millimeters, featuring eight legs and an oval-shaped body. Typically, their bodies are transparent or white, but during the parasitic stage, they turn reddish as they feed on the host's blood. The eggs are oval or elliptical in shape; males and females look remarkably similar, with differences only in the arrangement of hairs and the structure of their reproductive organs. The first pair of legs is highly modified—short and stout—with tips positioned close to the mouthparts—while the remaining three pairs of legs each have distinctly outward-protruding margins along the body. Male mites measure 293 × 159 micrometers, whereas female mites are slightly larger, measuring 390 × 205 micrometers.

The rat mite primarily parasitizes the fur of laboratory animals, preferring to establish itself in areas such as the host's back, neck, and shoulders. These mites reproduce rapidly and can trigger irritant responses, leading to symptoms like itching and inflammation in the host.

Using conventional methods for monitoring ectoparasites in laboratory animals, we observed the parasitic status of mites on BALB/c mice. The results showed an infection rate of 14%, with *Myocoptes musculinus* identified as the predominant mite species. These mites typically infest areas such as the face, neck, and back, where they lay their eggs directly on the hair shafts. In cases of severe infestation, mice exhibited noticeable symptoms, including hair loss, swelling of the skin surface, and thickening or hardening of the epidermis. Histopathological analysis under a microscope revealed that mild infections primarily led to epidermal thickening. However, in one severely infected mouse, more pronounced pathological changes were observed: scattered small pustules formed on the epidermal surface, while lymphocytes and fibroblasts accumulated densely beneath the epidermis, accompanied by occasional hemorrhages and inflammatory cell infiltration. Notably, the dermal muscle layer remained unaffected. Thus, for researchers working with laboratory animals in scientific experiments, effectively controlling and preventing *Myocoptes musculinus* infections is of critical importance.

Mite exterminators and parasite-control methods are commonly used to manage infections of rodent mange mites in laboratory animals. This may involve cleaning and disinfecting both the animals and their living environments, as well as conducting regular inspections and isolating infected individuals when necessary.

References:

1. Yin Peiyun, Zhang Rijun – *Shanghai Journal of Laboratory Animal Science*

2. *Endemic Diseases Bulletin*, Issue 1, 1999