What are the clinical symptoms of swine sarcoptic mange?
Swine sarcoptic mange is a surface parasitic disease caused by sarcoptic mange mites parasitizing the skin of pigs, characterized by itching and inflammation of the skin. Due to rubbing of the body surface, the skin of affected pigs becomes thickened and rough with hair loss, and injuries, bleeding, and blood coagulation forming scabs occur on the face, ears, shoulders, abdomen and other areas.
(1) Skin allergic reaction type
The skin allergic reaction type is the most common and also the most easily overlooked, and the main susceptible animals are commonly suckling piglets and nursery pigs; it can occur in all four seasons, with an increase during the transitions from spring to summer and from autumn to winter. The main clinical symptoms are as follows:
1. Suckling piglets and nursery pigs are more susceptible; as an indicator of sarcoptic mite infection, itching is more reliable than finding the mites. Excessive scratching and rubbing makes the pig's skin red; tissue fluid seeps out and forms black scabs after drying.
2. In the early stage of sarcoptic mange infection in suckling piglets and nursery pigs, it starts from the head, around the eyes, the cheeks and the base of the ears, then spreads to the back and the inner side of the hind legs.
3. After pigs are infected with mange mites, the mites tunnel into the pig's skin and lay eggs, suck lymph fluid, and secrete toxins; after 3 weeks, skin lesions appear, often starting from the head, especially small scabs (black) around the ears, eyes, and nose, then spreading to the entire body surface, tail and limbs, with erythema, papules, and black scabs appearing, and causing delayed-type and immediate-type allergic reactions, resulting in intense itching. Due to the itching, the affected pigs' normal feeding and rest are affected, and their digestion and absorption functions are reduced;
4. Affected pigs often rub the affected areas against walls, pen railings, troughs and other places, causing local hair loss. In cold seasons, because the skin is exposed due to hair loss, body heat is lost in large amounts, and the fat stored in the body is consumed in large quantities, leading to emaciation, and sometimes when secondary infection is severe, it causes death.
5. When sarcoptic mite infection in pigs is severe, it causes bleeding, connective tissue proliferation and skin thickening, resulting in damage to the pig's skin, which easily causes combined infection with Staphylococcus aureus, causing eczematous exudative dermatitis in pigs, with the affected area rapidly spreading around to the whole body, and it is highly contagious, ultimately causing a severe decline in the pig's body condition, exhaustion and death.
(2) Skin hyperkeratosis type
1. With the progression of the course of sarcoptic mite infection in pigs and the fading of the allergic reaction (generally after several months), excessive skin keratinization and connective tissue proliferation appear, and the pig's skin can be seen to thicken, forming large skin folds, fissures, and hair loss, with rough and scaly coat. It is commonly seen on the inner side of the auricle, around the neck, and the lower parts of the limbs in adult pigs, especially forming gray, loose thick scabs at the ankle joints. The pigs frequently scratch with their hooves or rub their skin against walls and fences, causing hair loss and skin damage with cracking and bleeding.
2. The hyperkeratotic ears of sows that have farrowed and breeding boars are the main source of mite infection in pig farms, and piglets are often infected by sows while suckling. The body and ear skin of sows that have farrowed show excessive keratinization; fattening pigs with skin itching rub their skin against walls; fattening pigs with skin itching scratch with their hind hooves.
In summary, severe itching, hair loss, scab formation, skin folds or fissures, and eczematous exudative dermatitis formed after mixed infection with Staphylococcus aureus, with the affected area gradually spreading around and being highly contagious, are the characteristics of this disease. Cao Yonghui