Swine pox occurs worldwide affecting piglets pre-weaning, weaners, (all-ages). The effects of swine pox are red spots, brown or black scabs, conjunctivitis, stunting.
- Causes of Swine pox >
- Effects of Swine pox >
- Diagnosis of Swine pox >
- Treatment & Control of Swine pox >
Causes of Swine pox
Swine pox is caused by the swine pox virus, a large DNA virus of the group and swine pox in the past by vaccinia virus. These viruses are extremely resistant to drying and may persist for years in exudates in which they can resist temperatures of 100 ° C for 10 minutes. Swine pox virus grows in pig kidney cell lines or on the chorioallantoic membranes of eggs to cause recognisable changes (CPE) and intracytoplasmic inclusions.
The virus enters through locally Skin Abrasions and multiplies there or attacks the skin after viraemia. The incubation period is 4-5 days from infection to the development of pustules and these last 10-14 days. All stages from vesicle, maculé, pustule to ulcer may develop. Viraemia (presence of virus in the blood) in sows results in the birth of congenitally-infected piglets. Serum antibody NEUTRALIZING develops at 7 days, peaks at 20 days and has Largely gone by 50 days post infection. Cellular immunity peaks at 11-21 days post infection.
Effects of Swine pox
The incubation period is 3-6 days but may be up to 14 days and the lesions persist for 1-3 weeks. Slight fever (to 40 ° C, 104 ° F) may accompanying the appearance of the lesions. Red 1cm papules (spots) appear on the ventral abdomen and rapidly form circular red brown scabs, which soon blacken. In young piglets the bursting of the vesicular (blister) stage on the face may lead to wetting, scab formation and conjunctivitis. Slight inappetence may accompany the development of the lesions. Affected pigs appear hairy and growth may be depressed. A large percentage of successive litters of sucking and recently-weaned pigs may be affected but the disease is rare in adults.
Mortality is rare although transplacental infection in newborn pigs can cause deaths. Lesions may be seen on the edge of the tongue, lips and all over the body. Badly affected newborn piglets may have to be killed, but all other age groups normally recover.
Diagnosis of Swine pox
The size, colour and especially the uniformity and circular shape of the lesions is characteristic. Flank biting, "spirochaetal granuloma" and local infection with Staphylococcus hyicus may also resemble pig pox but the agents of these are usually demonstrable. Pathological examination can confirm the diagnosis as the skin lesions are those of a typical pox virus. Vacuolaton Nuclear and cytoplasmic inclusions may be seen at the papular stage in the cells of the epidermis. A mild vesicular stage occurs but the pustular and crusting stages are most prominent. Secondary bacterial infections may occur. Electron microscopy of scabs, scraping or culture can confirm the presence of the virus and differentiates from that or if Orf.
Treatment & Control of Swine pox
Treatment or control are rarely attempted because of the mildness of the disease, but the use of insecticide to eliminate lice and flies which transmit the disease on a farm and the thorough cleaning and disinfection of pens in which outbreaks of the disease have occurred to help reduce the incidence.
Cleaning and disinfection is necessary because the virus may persist in a farm for years between outbreaks in dust and dried secretions in unused pin and fittings. The residual or newly purchased Progeny virus infects pigs and weaned pigs from non-immune farms when mixed with carriers or placed in infected pens. Vaccines have been produced experimentally but do not protect completely as fever may still occur on challenge.
