Swine population medicine, infection and production systems
Locate the problem in the production flow
Age group and production stage help organize a swine problem. Describe whether illness affects suckling piglets, weaners, growers, finishers or breeding animals, and compare expected with observed performance. Record animal movements, mixing, ventilation, feed and water changes, mortality and prior interventions. A herd average can hide a severely affected subgroup. Production records are useful only when definitions and denominators are consistent between the periods being compared.
Use syndromes without confusing them with confirmation
Respiratory, reproductive, enteric, neurological and skin syndromes have overlapping causes. PRRS, influenza, circovirus-associated disease and bacterial coinfections can produce complex herd presentations. Purple ears or fever alone do not distinguish PRRS from every other serious infection. Proliferative enteropathy involves Lawsonia intracellularis, while other organisms and management conditions can also cause diarrhea and poor growth. African swine fever and classical swine fever have important overlapping clinical features; suspicion requires the appropriate competent-authority pathway and laboratory assessment, not visual certainty.
Connect pathology, samples and epidemiology
Choose animals and specimens that represent the disease stage and the actual diagnostic question. A result from one chronically treated animal may not describe a new outbreak. PCR demonstrates targeted nucleic acid under the assay conditions; it does not automatically establish that the detected agent caused every lesion or is infectious in every setting. Serology can indicate exposure or response and needs interpretation with timing, vaccination history and test limitations. Necropsy and sample collection require appropriate biosafety, particularly where serious animal disease is suspected.
Prevent exposure and support welfare
Biosecurity concerns routes of introduction and spread through animals, people, equipment, vehicles, feed and other relevant materials. All-in/all-out management reduces some mixing and environmental carryover when the units and cleaning process are actually separated; the phrase alone does not guarantee pathogen freedom. Nutrition, water access, temperature, ventilation and stocking arrangements influence resilience and welfare. Antimicrobial selection, vaccination and disposal follow current veterinary and regulatory arrangements, which vary by place and product. Do not claim that one vaccine is universally available or that an old global statement about no vaccine remains current forever. These chapters provide written herd reasoning, not farm-specific dosing, outbreak declaration or control authority.