Comprehensive Prevention and Treatment Methods and Technical Points for Mange in Foxes and Raccoon Dogs

Mange is a chronic parasitic skin disease caused by mites of the families Sarcoptidae and Psoroptidae parasitizing the body surface or under the skin of fur-bearing animals. It is a contagious contact disease; if feeding and management are improper and treatment is not timely, it will directly affect animal health and fur quality, causing serious losses to farms.

In recent years, with the increase in the number of foxes and raccoon dogs raised and the increase in density, the incidence of mange in foxes and raccoon dogs has also been rising, and some farms even frequently see cases of foxes and raccoon dogs dying from mange.

1 Pathogens

Mites are incomplete arthropods, and their development process includes 4 stages: egg, larva, nymph and adult.

1.1 Sarcoptes scabiei burrows into the host epidermis and excavates tunnels, and the mites develop and reproduce within the tunnels. In the tunnels, at fairly regular intervals, there are small openings connecting with the outside, for air passage and as passages for larvae to enter and exit. The female mite lays eggs in the tunnel, and each female can lay 40 to 50 eggs in her lifetime. After 2 to 3 days, larvae hatch from the eggs; the larvae crawl to the skin surface, excavate small pits in the skin between the hairs, molt inside them into nymphs, burrow into the skin, form narrow and small burrows, and molt inside them into adults.

1.2 The female Psoroptes mite has an oval body and is dirty white. The female mite produces several dozen to 100 eggs. Under suitable conditions, after 3 to 4 days, six-legged larvae hatch from them; after molting for several days, these larvae become terminal protonymphs, and after another molt they become adults.

2 Epidemiological Characteristics

Foxes and raccoon dogs transmit the disease to each other through direct contact or indirect contact. Diseased animals are the main source of infection; for example, intensive rearing and breeding can all spread it. It can also be spread indirectly through directly contaminated cages, food bowls, whelping boxes, work clothes, gloves, and so on. In autumn and winter, insufficient light, high temperature and high humidity, and poor ventilation are favorable for mite development, so mange spreads more widely and the disease is more severe. In late spring and early summer, as the animals molt, ventilation improves, and the skin receives sufficient light, Sarcoptes and Psoroptes mites die in large numbers; at this time symptoms lessen or the animals recover completely.

3 Clinical Symptoms

3.1 Intense itching caused by Sarcoptes is the main symptom of this disease and runs through the entire course of the illness. It generally first occurs on the skin of the soles of the feet, then gradually spreads to the hocks and elbows, then spreads to the head, tail, neck and the inner side of the chest and abdomen, and finally develops into systemic infection. The more severe the infection, the more intense the itching. Its characteristic is that after diseased foxes and raccoon dogs enter a warm small chamber or after exercise, the itching becomes even more intense, causing them to lick continuously, scratch with the front claws, and constantly rub against surrounding objects, thereby worsening inflammation of the affected area and also spreading large amounts of pathogens around them. Because the body skin of foxes and raccoon dogs is extensively affected, appetite decreases, and sometimes poisoning and death occur, but most cases have a good prognosis after treatment.

3.2 Ear mange: in the early stage, the local skin becomes inflamed, with mild itching. Diseased foxes and raccoon dogs occasionally shake their heads, or rub the ear shells against the ground, small chambers, or cage netting, and scratch the affected area with their paw claws, causing the skin of the external ear canal to redden and swell, forming inflammatory blisters with serous exudation. The exudate adheres to the hair on the lower edge of the ear shell; after drying, it forms crusts that are thickly embedded in the ear canal like a paper roll and block the ear canal. Sometimes ear mange mites burrow into the inner ear, damage the tympanic membrane, and cause perforation of the tympanic membrane. At this time, the appetite of diseased foxes and raccoon dogs decreases, and the head turns at an angle of 90 to 120 degrees toward the affected ear side. Severe cases may extend to the ethmoid bone and brain, resulting in spasms or epileptic symptoms.

4 Diagnosis

This disease is relatively easy to diagnose based on the characteristic clinical symptoms (crusting) produced by mite infestation of the skin of affected animals. For diseased animals with inconspicuous symptoms, it is necessary to collect crusts from the skin of the affected area and examine whether mites are present before a definitive diagnosis can be made. On farms with the conditions, use a surgical blade to scrape a small amount of the dirty blood material beneath the crust, place it in a clean glass dish, soak it in 10% NaOH solution for 3 to 5 minutes, then dip 1 drop of the suspension onto a glass slide and observe under a low-power microscope; mites can then be seen in the field of view. Mites can also be observed with a magnifying glass of relatively high magnification.

Differential diagnosis of inflammation: clinically, it should be distinguished from fungal disease. The main differences are: mange can infect all parts of the body, diseased animals have intense itching, and apart from hair loss, the shape of the lesions is irregular; fungal infection causes only mild itching, and most lesions appear as circular ringworm patches with obvious boundaries; after the crusts fall off, they appear bright red and moist, with an erosive surface and residual hair. If diseased material is collected, processed and examined under a microscope, the two are even easier to distinguish.

5 Prevention and Treatment Measures

Mites are highly contagious through contact. Missing affected areas and scattering diseased material can all cause new infections. The following measures can be taken for treatment.

5.1 Clipping hair and removing crusts: to allow the drug to fully contact the mites, clip the hair on the affected area and within 3 to 4 cm around it, collect the hair and dander in a waste container for burning or soak them in acaricide, and wash with warm soapy water to remove hard crusts and dirt.

5.2 Repeated medication: drugs for treating mange mostly have no killing effect on mite eggs; therefore, treatment should be repeated once 5 to 7 days after treatment in order to kill newly hatched larvae and achieve thorough treatment.

5.3 Drug treatment: there are many drugs for treating mange, some of which are no longer used. Several commonly used drugs are introduced below.

5.3.1 Ivermectin or avermectin: generally inject 0.02 mL per kg body weight subcutaneously in the neck, once every 7 days, and 3 consecutive treatments can cure it. However, in recent years, judging from treatment results, foxes and raccoon dogs have shown a tendency to develop resistance to the above two drugs. Therefore, the dose may be considered slightly increased, for example, using 0.03 to 0.04 mL per kg body weight, once every 5 days, with relatively significant effect.

5.3.2 Dectomax, produced by Pfizer of the United States, is the first-choice drug. This drug is more effective than ivermectin and avermectin in treating mange, and has low toxicity; generally 1 to 2 uses can cure it.

5.3.3 Others: according to reports, treatment with external medicinal liquids such as acaricide or decis has obvious effects, and after 1 to 2 treatments, recovery occurs; however, it is only suitable for small-area infections. Specific operation method: restrain the animal diagnosed with mange, clip the hair and crusts, use tweezers to hold a cotton ball, dip sufficient medicinal liquid and apply it to the affected area, repeatedly using several cotton balls to wipe 3 to 4 times. After application, send the diseased animal back to its original cage, and after 5 to 7 days, treat once more by the above method, and it can be cured.

According to information, for foxes and raccoon dogs with mange, applying 2% trichlorfon or 15% concentrated iodine tincture to the affected area more than 2 times can have a relatively good therapeutic effect.

5.4 Isolation and treatment: when mange occurs in foxes and raccoon dogs, the whole group should be examined, and diseased animals found should be immediately isolated and treated. Contaminated cages and equipment should be disinfected with 2% to 3% hot creolin or lysol solution. It is best, immediately after treating diseased animals, to thoroughly disinfect the cages and environment with the above medicinal liquids, leaving no hidden dangers. To prevent the spread of mange, all crusts and hair clipped from treated affected animals must be destroyed. When introducing new breeds, strict inspection should be carried out, and they should be kept in isolation for a period of time; only when there is confirmed no mange should they be mixed into the group for rearing. After keepers contact diseased animals, attention should be paid to disinfection to avoid cross-infection.