5.1 Porcine Health & Disease Management

Commercial Swine Production & Piglet Processing

Commercial swine production systems in North America are highly structured, intensive operations optimized for animal flow, growth efficiency, and biosecurity. Modern production is divided into specialized stages: gestation and farrowing (sows are housed, bred, and give birth), nursery (weaned piglets from 3 to 10 weeks of age), and finishing (grow-finish hogs from 10 to 26 weeks of age, reared to market weight of approximately 120-130 kg).

To break the transmission cycle of pathogens from older, shedding pigs to younger, susceptible cohorts, operations utilize the All-In/All-Out (AIAO) management system. In an AIAO workflow, groups of pigs of similar ages are moved together through each production phase. Once a group exits a room or barn, the facility is completely emptied, pressure-washed, disinfected with approved agents, and allowed a drying period (downtime) before the next batch enters. This practice is essential for controlling chronic diseases like PRRS and mycoplasmal pneumonia.

Neonatal Piglet Processing Protocols

Within the first week of life, neonatal piglets undergo processing to optimize growth, prevent cannibalistic behaviors, and ensure meat quality. These procedures must be conducted using clean, sanitized instruments to minimize secondary infections:

• Iron Supplementation: Piglets are born with extremely low iron stores (~50 mg) and double their body weight in the first week. Sow colostrum and milk provide only ~1 mg of iron daily, whereas piglets require ~7-10 mg daily. In confinement housing without access to soil, piglets quickly develop iron deficiency anemia (microcytic, hypochromic anemia). To prevent this, an injection of 100–200 mg of iron dextran is administered intramuscularly (IM) in the neck muscle (trapezius) within 1 to 3 days of birth. Injection in the hindlimb (ham) is avoided to prevent muscle staining, tissue damage, and potential carcass condemnation at slaughter.
• Tail Docking: Tail biting is a cannibalistic behavior common in intensive housing systems, triggered by crowding, poor ventilation, or nutritional deficits. Tail biting leads to pain, secondary bacterial infections, ascending pyemia, spinal abscesses, and hindlimb paralysis. To mitigate this risk, tails are docked within the first 7 days of life using clean, disinfected clippers or electric cauterizing units. The tail is cut leaving approximately 1.5 to 2.5 cm (or a stub covering the vulva in females). Leaving the tail too short increases the risk of rectal prolapse, while leaving it too long fails to prevent tail biting.
• Castration: Male piglets destined for market are castrated within the first 14 days of age to prevent boar taint, an unpleasant odor and taste in pork caused by the accumulation of androstenone (a testicular steroid) and skatole (a product of bacterial tryptophan degradation in the colon). Castration also reduces aggressive behavior and mounting in finishing pens. The procedure is performed by making two vertical incisions over the scrotum, extruding the testicles, and severing the spermatic cord via traction or cutting. In older pigs, surgical castration requires systemic anesthesia and analgesia.
• Ear Notching: This is the traditional identification method. The piglet's right ear represents the litter number, and the left ear represents the individual piglet number. Notches are placed in specific zones representing values (1, 3, 9, 27, 81) to uniquely identify individual animals.

Common Infectious Diseases of Swine

Veterinary practitioners must differentiate swine pathogens based on their clinical signs, pathology, and diagnostic profiles. The table below compares the five most high-yield swine diseases encountered on the NAVLE:

Porcine Reproductive and Respiratory Syndrome (PRRS)

PRRS is the most economically devastating disease affecting the global swine industry. The virus targets alveolar macrophages, compromising the pulmonary defense mechanisms and predisposing pigs to secondary bacterial infections (e.g., Streptococcus suis, Glaesserella parasuis). Clinical signs present in two phases: reproductive failure in the breeding herd (characterized by a sudden spike in late-term abortions, premature farrowings, and stillborn or mummified piglets) and respiratory disease in nursery and growing pigs (characterized by dyspnea, fever, and poor growth rates). Diagnosable via PCR on oral fluids or serum. Prevention relies on strict biosecurity (showering in/out, air filtration), herd closure (stopping replacement gilt entry for at least 30 weeks to allow immunity to stabilize), and strategic vaccination.

Porcine Epidemic Diarrhea Virus (PEDV)

PEDV is a highly contagious enteric coronavirus that replicates in the enterocytes of the small intestine, leading to acute malabsorptive diarrhea, vomiting, and severe dehydration. While finishing pigs recover after mild diarrhea, neonatal piglets (<2 weeks old) suffer near 100% mortality due to rapid dehydration. Pathologically, it causes severe villous atrophy (decreasing the villus-to-crypt ratio from the normal 7:1 down to 1:1). Control in an outbreak involves stabilizing the breeding herd's immunity via feedback (controlled exposure of gestating sows to minced intestinal tissue from infected piglets) to stimulate IgA production in colostrum.

African Swine Fever (ASF)

ASF is a highly contagious, reportable viral disease of domestic and wild pigs. The virus is extremely resilient in the environment and in cured pork products. Transmission occurs via direct contact, ingestion of contaminated feed/swill, or vectors like soft ticks (Ornithodoros spp.). It targets vascular endothelial cells and macrophages, causing widespread hemorrhage. On necropsy, key lesions include a massively enlarged, dark, friable spleen (splenomegaly) with marginal infarctions, hemorrhagic lymph nodes (resembling blood clots), and petechial hemorrhages on the renal cortex ("turkey egg kidney"). There is no vaccine or treatment; containment requires immediate reporting, quarantine, and depopulation.

Erysipelas (Diamond Skin Disease)

Erysipelas is a bacterial disease that occurs sporadically or as a herd outbreak. The bacterium, Erysipelothrix rhusiopathiae, is shed in saliva, feces, and urine, and can persist in soil. The acute form presents with sudden death, high fever (up to 108°F / 42.2°C), and characteristic rhomboid (diamond-shaped) skin lesions due to localized vasculitis and thrombosis. Chronic cases develop shifting lameness, severe proliferative arthritis, or vegetative valvular endocarditis (primarily affecting the mitral/left AV valve), leading to congestive heart failure and sudden death under stress. Penicillin is the drug of choice for acute cases.

Atrophic Rhinitis (AR)

Atrophic Rhinitis is a multi-factorial upper respiratory disease. Non-progressive AR is caused by Bordetella bronchiseptica and is mild and transient. Progressive AR is caused by toxigenic strains of Pasteurella multocida, which produce a potent dermonecrotic toxin that inhibits osteoblast activity and accelerates osteoclast activity in the nasal turbinates. This leads to the destruction of the turbinate bones and deviation or shortening of the upper jaw (snout). Diagnosis is confirmed at necropsy by sawing across the snout at the level of the second premolar and measuring turbinate space. Prevention focuses on vaccinating gestating sows to provide colostral immunity, optimizing ventilation (reducing ammonia levels), and strategic antimicrobial treatment (e.g., tylosin, sulfas) of piglets.