Special Topics On Swine Disease– Sarcoptic Mange

Special Topics On Swine Disease– Sarcoptic Mange

Overview:
Swine sarcoptic mange is a chronic parasitic skin disease caused by Sarcoptes scabiei var. suis, a mite from the Sarcoptidae family, which parasitizes the skin of pigs. It poses a significant threat to swine health. Infected pigs frequently rub against surfaces, resulting in thickened, rough skin and hair loss. Lesions, bleeding, scabs, and crust formation often develop on areas such as the face, ears, shoulders, and abdomen. This disease is a chronic and contagious condition.

Pathogen:
Sarcoptes scabiei (burrowing mite) lives in tunnels it burrows within the deep layers of the pig’s skin. The mite is very small (0.2–0.5 mm), yellowish, and tortoise-shaped, with a convex dorsal surface and a flat ventral surface. The ventral side has four pairs of short, conical legs, and the anterior part features a blunt, rounded mouthpart adapted for chewing. The mites excavate tunnels in the host’s epidermis, feeding on skin tissues and lymphatic fluid, where they also develop and reproduce. The entire life cycle, including egg, larva, nymph, and adult stages, occurs within the host. Outside the host, the mites typically survive for about 3 weeks.

Epidemiology:
Pigs of all ages and breeds are susceptible to this disease. The main routes of transmission are direct contact between infected and healthy pigs, and indirect contact via mite-contaminated housing, bedding, and equipment. Piglets often lie close together, which facilitates rapid disease transmission. Poor environmental hygiene, dark and damp pig houses, and malnutrition contribute to the occurrence and spread of the disease. The condition spreads fastest during autumn and winter, particularly in cold and rainy weather.
The disease is mainly transmitted through direct contact, such as infected sows transmitting the mites to nursing piglets or infected pigs spreading it to pen mates. Indirect transmission can occur via contaminated pig houses, equipment, clothing and hands of farm personnel, and even dogs on the premises. Factors like dark, humid pig houses, poor ventilation, poor hygiene, injuries from biting or fighting, and skin abrasions all favor the development and spread of the disease.

Clinical Signs:
The disease occurs more frequently in piglets. Early symptoms usually start around the eyes, cheeks, and base of the ears, then spread to the back, flanks, and inner thighs. The primary clinical sign is intense itching, causing pigs to rub against objects or scratch with their limbs, often breaking the skin and leading to hair loss, scab formation, thickened skin, folds, and cracks.
Swine sarcoptic mange presents two clinical types: allergic dermatitis type and hyperkeratotic type.

1. Allergic Dermatitis Type:
This is the most common type and often overlooked. It primarily affects suckling and weaned piglets and can occur year-round, with higher incidence during spring-summer and autumn-winter transitions. Main clinical signs include:

1. Piglets and weaned pigs are most susceptible. Itching is a more reliable indicator of infection than mite detection. Excessive scratching and rubbing cause skin reddening, lymph exudation, and formation of black scabs after drying.
2. In early stages, lesions begin at the head, eye area, cheeks, and base of the ears, then spread to the back and inner thighs.
3. After mites infest the skin, they tunnel, lay eggs, consume lymph fluid, and release toxins. Within three weeks, skin lesions appear, starting from the head, especially around the ears, eyes, and nose. Black scabs, red spots, and papules develop, later spreading over the entire body, tail, and limbs, triggering both delayed and immediate hypersensitivity reactions, causing intense itching. This significantly affects the pig's feeding and rest, impairing digestion and nutrient absorption.
4. Infected pigs frequently rub against walls, pen bars, or troughs, causing localized hair loss. In cold seasons, exposed skin loses heat rapidly, leading to fat depletion, emaciation, and sometimes death due to severe secondary infections.
5. Severe infestations result in bleeding, connective tissue proliferation, and skin thickening, making the skin more prone to secondary infections such as Staphylococcus aureus, leading to eczematous exudative dermatitis. Lesions spread quickly and are highly contagious, ultimately causing severe physical deterioration and death due to exhaustion.

2. Hyperkeratotic Type:
Also referred to as chronic mange, this type is more common in breeding sows, boars, and adult pigs. Main clinical signs include:

1. As the disease progresses and allergic reactions subside (usually after several months), hyperkeratosis and connective tissue proliferation occur. The skin thickens, forming large folds, cracks, and hair loss. The hair becomes coarse with dandruff, typically affecting the inner ears, neck, and lower limbs, especially the hocks, where grayish, loose, thick scabs form. Pigs frequently scratch with their hooves or rub against walls and fences, causing hair loss, skin damage, cracking, and bleeding.
2. Hyperkeratotic lesions on the ears of breeding sows and boars serve as the primary source of mites in pig farms. Piglets are often infected by sows during nursing. Breeding sows show excessive keratinization on the body and ears, while fattening pigs exhibit intense itching, scratching themselves with hind limbs or rubbing against walls.

In summary, key features of the disease include severe itching, hair loss, scab formation, skin folds or cracks, and secondary infections with Staphylococcus aureus leading to eczematous exudative dermatitis, with lesions spreading and showing high transmissibility.

Prevention:

1. Deworm pigs both internally and externally at least twice a year, during the spring-summer and autumn-winter transitions. Each deworming cycle should last 5–7 consecutive days.
2. Combine enhanced prevention with eradication. Deworm all pigs on the farm simultaneously. A commonly overlooked but critical step is environmental decontamination within 7–10 days after deworming the pigs, to ensure thorough mite elimination. Use a 1:300 dilution of pyrethroid solution or a 2% diluted trichlorfon solution to disinfect the pig house, including floors, walls, roofs, surroundings, vegetation, and equipment, to eliminate residual mites. Also, treat manure and waste through high-temperature composting to kill mites. Eliminating mites from the environment is one of the most effective and crucial measures to prevent mange. To prevent reinfection of healthy pigs from contaminated pens and equipment, thoroughly remove manure, compost it, and disinfect all surfaces pigs may contact, such as walls, floors, troughs, and waterers. Maintain regular disinfection and keep the pig house dry.