Neonatal Polyarthritis (Joint-Ill)
Neonatal septic polyarthritis, which causes death in up to 1.5% of affected pigs, is caused by various facultative and specific pathogens that cause localized infections that precede septicemia. Healthy, suckling pigs typically “paddle” with their legs, abrading the skin of the carpi or coronary bands; an infection often becomes established under scabs that develop. Poor hygiene at tail docking, ear notching, or castration, and careless clipping of needle teeth can also result in localized infections. If an infected wound leads to bacteremia, organisms can cross the synovial membrane, and polyarthritis is likely. Microorganisms can also gain entry to the circulatory system via the tonsils or oropharynx or as a result of an ascending omphalophlebitis. Pigs with exudative epidermitis (see Exudative Epidermitis) are also prone to polyarthritis, but this may be a reflection of the same skin damage discussed above.
Affected pigs are lethargic and may fail to suckle. Joints are swollen, painful, and warm, and lameness affecting one or more limbs is severe. With time, the soft, fluctuant swellings become firm. At necropsy, the umbilicus should be examined to see whether it is hard and swollen. Typically, cream or green pus is found in and around swollen joints (particularly the elbows, carpi, stifles, and hocks), in the umbilical stalk, and sometimes over the meninges or in the fissure between the cerebrum and cerebellum. Organisms isolated from baby pigs included streptococci (including Streptococcus suis), staphylococci, Actinobacillus suis, Trueperella pyogenes, Escherichia coli, and occasionally, Pasteurella multocida, Erysipelothrix rhusiopathiae, or Haemophilus spp. If untreated, affected pigs become runts that fail to thrive in the nursery.
Treatment must be based on bacterial culture and antimicrobial sensitivity profiles and applicable regulations on product use. Antimicrobial therapy should be initiated early in the course of the disease if it is to be effective, and treating all pigs in the group at risk may be prudent, especially if S suis is implicated. Penicillins have been the drugs of choice, depending on the causal agent and sensitivity. However, a broader range of drugs is available, including lincomycin, trimethoprim/sulfonamide, and tylosin, provided causal organisms are sensitive. The range of suitable drugs is increased further if streptococcosis caused by S suis develops (see Streptococcal Infections in Pigs).
Regardless of the cause of a local infection, if there is an ongoing problem with septic polyarthritis, it is important to observe the practices used in farrowing rooms and to look for opportunities for improvement. An “all-in/all-out” flow of pigs is important, and scrupulous hygiene in farrowing crates helps to reduce environmental contamination and incidence of neonatal polyarthritis. Prevention may be difficult because most types of floors, including those bedded with straw, can cause skin abrasions. Plastic-covered woven wire provides a smooth, relatively soft, self-cleaning floor and may help; plain woven wire is similar if it is smooth. If replacement of flooring is not economically viable, sections of clean, soft carpeting may help reduce skin abrasions.
Separate instruments should be used for teeth and tail clipping, and they should be cleaned and disinfected between pigs, preferably using a dry paper towel. Soaking instruments in contaminated disinfectant solution between pigs or litters promotes contamination and infection. If teeth are not clipped or if there are sharp remnants of clipped teeth, pigs that suckle aggressively can lacerate the faces of other pigs, resulting in pyoderma. Castration equipment must be kept sterile and sharp. If tail stumps are infected, antiseptic solution may be used as a spray to improve hygiene.
Litters from gilts are more prone to neonatal polyarthritis. Colostral protection against this syndrome and other infectious diseases of baby pigs increases as a sow ages. Because pigs in large litters have to compete more to suckle and are, therefore, more prone to lesions on their faces and forelimbs, cross-fostering within 24 hr of birth to balance litter sizes may help. Piglets nursing sows with hypogalactia or agalactia spend more time nursing, leading to more forelimb lesions.
Diseases of the Foot
Neonatal foot lesions fall into two main categories: either the sole or heel is damaged by the floor, or the hoof wall is traumatized by the sow standing on a pig's foot or by entrapment in the flooring.
Bruises or lacerations develop on either the sole or heel. The lesions are associated with worn and rough floor surfaces and with floors that have solid as well as perforated surfaces. Rough flooring can also cause bruising in soft tissue below the hoof wall. If spaces between slats are large, digits can be entrapped, and lameness results from bruising or infection at the coronary band. Pigs on expanded metal floors can incur heel and wall injuries leading to loss of accessory digits. Second and third digits may be damaged as the pigs thrust with their feet during suckling and catch their toes against sharp metal edges. Sharp spicules on woven wire cause lacerations and predispose to infectious laminitis and polyarthritis.
Prevention is based on selecting floors that minimally injure feet or skin. Because of similarities with infectious polyarthritis, the approach to treatment and prevention is similar (see above). Improved hygiene within the environment may help reduce septic laminitis and allow injuries to heal.
Splayleg or spraddleleg (see Splayleg) is precipitated by weakness and immaturity of skeletal muscles at birth because myotubular development is impaired. Forelimbs, hindlimbs, or all four limbs may be affected so that the piglet either walks with difficulty or cannot stand. The disorder appears sporadically in litters, and only a few pigs in a litter are typically affected. There is a hereditary component in European Landrace and, to a lesser extent, in Large White pigs. Male, premature, and small pigs, and pigs from older sows seem more susceptible. Deficiencies of choline, methionine, and thiamine in the sow's diet may precipitate the syndrome, and zearalanone toxicity via the sow's milk has been implicated, but there is controversy as to the exact cause. To varying degrees, affected pigs are unable to move around and die either because the sow crushes them or they become hypoglycemic because they cannot feed. Alternatively, skin and foot abrasions develop, predisposing to arthritis, polyarthritis, or pododermatitis and osteomyelitis of the digits.
Timely management practices are essential to ensure that pigs can feed and avoid hypoglycemia and hypothermia. If only the hindlimbs are affected, they can be hobbled so that the pig can lever itself up using forelimbs and hop around to nurse. Various hobbles, including a figure-8 tape or bandage, have been successful. Some recommend taping the pelvic limbs so they are directed cranially on the belly. By using the limbs or pushing against a bellyband, the pig potentially develops and strengthens muscles, which can enable to pig to walk after a few days. Hobbles must be removed within a few days of pigs walking, to avoid ischemic necrosis of skin and other tissues as the pigs grow.
Pigs with splayleg may require assistance to suckle colostrum and milk for the first few days of life. Some advocate the use of “hot boxes” to nurture these and other ailing pigs, relying on milk replacers as the main source of food once the pig has had colostrum. Because slippery floors exacerbate the condition, temporary use of sanitized mats may help. Any nutritional deficiency or mycotoxin contamination of food should be addressed.
Iron toxicosis in piglets (see Iron Toxicity in Newborn Pigs) after injection with iron preparations soon after birth may be associated with muscle fiber fragility, especially if there is a selenium deficiency in the sow and, therefore, the piglet. Inadequate hygiene or technique when baby pigs are injected with an iron preparation can lead to bruising and septic myositis. This problem can be resolved by adequate training of farrowing room staff.
Meningoencephalocoele and cerebellar hypoplasia interfere with locomotion in affected pigs, as can infections with Listeria monocytogenes and Streptococcus suis. Thus, S suis can cause locomotion problems as a result of meningitis and neurologic signs, or a suppurative arthritis can be the primary complaint. Congenital tremors cause pigs to shake when awake and remain still when sleeping. Either heredity or viral infections may cause the problem. In the USA and other parts of the world, porcine circovirus has been implicated in congenital tremors. The tremors usually are most severe during the first week of life and make it difficult for pigs to nurse. Affected pigs must be assisted with nursing until the tremors subside.
Hereditary and Congenital Disorders
Mycotoxins in the sow's feed can cause arthrogryposis, which leads to deformity of limb bones, but the primary effect may be on neuromuscular function. Pigs affected by hereditary hyperostosis have thickened thoracic limbs and a domed forehead and generally do not survive. Polydactyly and syndactyly are occasional abnormalities that may affect locomotion of the baby pig; syndactylous or mule-footed pigs have been propagated and sold by some producers with no obvious disabilities for the pigs. When causal agents contaminate the feed, sources of these products should be found and avoided; if hereditary disease is suspected, the source(s) of replacement stock must be investigated.
Last full review/revision September 2015 by Jerry L. Torrison, DVM, PhD, DACVPM