Common Diseases
Part of Veterinary Medicine
Identifying and managing the most prevalent diseases affecting livestock in subsistence and rebuilding contexts.
Why This Matters
Every region has its characteristic disease burden for livestock. In tropical climates, tick-borne diseases, internal parasites, and heat-related disorders dominate. In temperate zones, respiratory diseases, clostridial infections, and nutritional disorders are more common. But across all climates and all species, a handful of diseases account for the majority of livestock deaths and production losses — and most of these are manageable with knowledge, even without pharmaceutical inputs.
Understanding common diseases by species allows you to build recognition-action protocols: see these signs, take these steps. The alternative — treating every sick animal as an undifferentiated mystery — wastes resources, delays appropriate treatment, and allows preventable losses. Pattern recognition in animal disease is a learnable skill that improves rapidly with deliberate attention.
This article covers the most widely encountered diseases across the major livestock species. Species-specific conditions (mastitis, hoof rot, bloat) are covered in dedicated articles.
Respiratory Diseases
Respiratory disease is the leading cause of death in young livestock globally. It affects cattle, sheep, goats, horses, pigs, and poultry through overlapping but distinct pathogen complexes.
Signs: Nasal discharge (clear → cloudy → purulent as disease progresses), cough, increased respiratory rate, labored breathing, elevated temperature, reduced appetite, social withdrawal.
Pneumonia in cattle and small ruminants: Often begins viral (IBR, PI3, BRSV in cattle; various pneumoviruses in sheep) and becomes complicated by bacterial pathogens (Mannheimia, Pasteurella). Animals in stress (weaning, transport, cold/wet weather, overcrowding) are most vulnerable. Treatment focus: isolation, dry shelter, supportive care, fresh water and palatable food. Antibiotics if available and if bacterial involvement is suspected (purulent discharge, fever over 40°C).
Pneumonia in pigs: Enzootic pneumonia (Mycoplasma hyopneumoniae) is almost universal in intensively-raised pigs. Signs are a chronic non-productive cough in growing pigs with reduced growth rate. Rarely fatal on its own but predisposes to more serious secondary infections.
Infectious bronchitis and Newcastle disease in poultry: These spread rapidly through flocks. Newcastle disease causes gasping, twisted necks, green diarrhea, and high mortality. Infectious bronchitis causes respiratory signs and drops in egg production. No treatment; focus on biosecurity (isolation of new birds, quarantine of sick birds).
Clostridial Diseases
Clostridium bacteria produce some of the most lethal toxins in the animal kingdom. These bacteria are ubiquitous in soil and gut, and cause disease when conditions favor toxin production — usually associated with gut disturbance, wounds, or rapid dietary changes.
Blackleg (Clostridium chauvoei): Young cattle and sheep. Sudden death or rapidly progressing swelling, gas crepitation under skin, lameness. Usually fatal. Carcasses swell quickly. Burn or deeply bury — do not skin, as the organism persists in soil for decades.
Tetanus (Clostridium tetani): All species, any wound. Muscle rigidity, “sawhorse” stance, lockjaw, sensitivity to noise, death from respiratory paralysis. Fatal in most unvaccinated animals. Prevention through vaccination is far more effective than treatment.
Enterotoxemia (Pulpy Kidney, Overeating Disease — C. perfringens): Sheep, goats, cattle, pigs. Sudden death in well-fed animals, especially after grain introduction or lush pasture change. Toxin production in the gut. Prevention: gradual dietary transitions, avoid overeating scenarios. Vaccination in endemic areas.
Gas gangrene: Any species with deep puncture wounds or tissue damage. Rapid swelling, gas under skin, darkening tissue, systemic toxemia. Aggressive wound debridement and drainage are essential.
Foot and Mouth Disease
Foot and mouth disease (FMD) is a highly contagious viral disease affecting all cloven-hoofed animals (cattle, sheep, goats, pigs, deer). It does not affect horses. Signs: blisters (vesicles) on the mouth, tongue, gums, feet (coronary band area), and teats. Animals are extremely lame, reluctant to move, and stop eating due to mouth pain. Mortality in adults is low; mortality in young animals can be high. Milk production drops severely.
FMD is a report-able disease in most countries, but in a post-collapse scenario: isolate affected animals, provide soft feed and fresh water, treat foot lesions with antiseptic, allow immunity to develop naturally (recovery takes 2–3 weeks). Animals that recover are immune for several months. The virus is destroyed by sunlight, pH below 6 or above 9, and heat.
Metabolic Disorders
Metabolic disorders are caused by nutritional imbalance rather than pathogens. They affect high-producing animals most severely.
Milk fever (hypocalcemia): Dairy cows and does around parturition. Calcium drops when lactation begins faster than the body mobilizes it. Signs: weakness, inability to rise, cold extremities, bloat, low temperature, coma. Treatment: calcium gluconate solution given subcutaneously or intravenously (SQ is safer without veterinary training). Prevention: avoid calcium-rich feeds in the dry period.
Ketosis: High-producing dairy cows in early lactation, ewes with twin or triplet pregnancies (pregnancy toxemia). Body mobilizes fat faster than it can metabolize it, producing ketones. Signs: sweet/acetone breath, reduced appetite, depression, weight loss. Treatment: propylene glycol (50–100 ml orally twice daily) or any digestible carbohydrate source (molasses). Prevention: maintain good body condition entering late pregnancy; avoid fat cows at calving.
Grass tetany (hypomagnesemia): Cattle and sheep on lush spring pasture. Sudden-onset muscle tremors, staggering, convulsions, death. Treatment: magnesium sulfate solution SQ. Prevention: provide magnesium mineral supplements on lush pastures.
Enteric (Gut) Diseases
Neonatal diarrhea (scours): The most common cause of death in neonatal calves, lambs, and kids in the first 2 weeks of life. Caused by E. coli, Salmonella, Cryptosporidium, Rotavirus — often in combination. Signs: profuse watery diarrhea, dehydration, weakness. Treatment priority: oral rehydration fluid (water + salt + sugar + baking soda solution), warmth, colostrum if available. Antibiotics for E. coli or Salmonella if available. The animal dies from dehydration, not the bug — fluid replacement is the intervention.
Coccidiosis: Affects calves, lambs, kids, and poultry. Bloody diarrhea, straining, weakness in young animals. The protozoan Eimeria destroys intestinal lining. Reduce crowding, improve hygiene. Supportive care with oral rehydration.
Salmonellosis: Any species. Acute watery (often bloody) diarrhea, fever, rapid deterioration. Highly contagious — isolate immediately and treat handlers as potentially exposed. Salmonella is zoonotic (see related article on zoonotic diseases).
Disease Prioritization in Resource-Limited Settings
When pharmaceutical inputs are scarce, prioritize your management energy on:
- Prevention through vaccination (where vaccines are available), biosecurity, nutrition, and parasite control — see dedicated articles.
- Early detection through daily observation — treat early-stage disease with supportive care before it becomes critical.
- Triage — identify animals likely to recover with supportive care versus those requiring specific pharmaceutical intervention. An animal with advanced pneumonia and fever over 41°C has lower survival odds than one with early-stage disease and a temperature of 40°C. Allocate scarce antibiotics to those where they will be most effective.
- Isolation — prevents most contagious diseases from spreading through the herd. When in doubt, isolate.