• Coronary blood flow: similar to 90% of the human population and unlike the dog, the coronary supply is right-side dominant and has no pre-existing collateral circulation. The left azygous vein drains the intercostal vessels into the coronary sinus; if this vessel is ligated, all venous drainage will go into the coronary sinus.{4761}
• Torus pyloricus: this is an outpouching of the stomach, located near the pylorus.{4761}
• Gastrointestinal anatomy: the majority of the large intestine is arranged in a spiral, in the left upper quadrant. There are two types of Peyer's patches, multiple discrete ones in the jejunum containing B and T cells, and a long ileal one containing B cells.{4761}
• Lymph nodes: are "inverted"; the germinal centers are in the internal part of the node. Afferent lymph percolates from the central cortex to the outer paracortex.{4761}
• Swine leukocyte antigen system (similar to MHC in the mouse): SLA class I genes restrict T-cell activation and induce self-tolerance. SLA class II genes are in B cells, activated macrophages, some CD8+ T cells, and vascular endothelium. SLA class III genes function in the complement system, similar to humans. Antibody/antigen complexes are eliminated via the lung in swine, not the liver and spleen.{4761}
• Pancreatic exocrine system: Humans have a major duodenal papilla near their bile duct, and an accessory duct entering at the minor papilla. The pig has only a single pancreatic duct that passes into the duodenum; therefore secretions must be returned to the animal somehow. Cattle have an accessory pancreatic duct and a large secondary system, but one can collect very large volumes of pancreatic secretion for enzyme studies.{4003}

• Sexual maturity: 3-7 months
• Estrous cycle length: 21 days (17-25); estrus lasts 48 hr
• Gestation: 114-115 days
• Farrowing duration: 3-4 hours typically (range 1-8); provide assistance if >30-60 minutes elapse between each piglet.
• Colostrum must be ingested during the first 12 hours; no transplacental transfer occurs. Sow's milk has insufficient iron, so piglets must be given 100-200mg iron dextran IM within 48 hr of farrowing.

Xenotransplantation research{4761}

Hyperacute rejection is mediated by complement in the pig organs. NHPs and human have high titers of "xenoantibodies" which target carbohydrate antigens, especially Gal1 expressed in donor tissue endothelium, and this response results in vascular injury and DIC.

Later, delayed rejection occurs through cell-mediated responses over 3-4 days. Endothelial cells in the graft are activated, leading to thrombosis, expression of adhesion molecules, and cytokine release. In humans, CD4+ T cells, monocytes and NK cells mediate rejection of porcine xenografts. Transgenic science is being used to combat xenotransplant rejection, i.e. to moderate the cell surface carbohydrate phenotype of vascular endothelial cells.

Another major problem is xenozoonoses. Immunosuppressed recipients may become infected by organisms that do not normally infect humans. Gnotobiotic pigs are therefore being used.

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Diseases{4761}

• Salmonellosis should not be treated because of the carrier state and zoonotic potential.
  • S. cholerasuis causes septicemia and pneumonia
  • S. typhimurium causes enterocolitis
• Haemophilus parasuis causes Glasser's disease or infectious polyarthritis, in 3 week-4 month old swine. Signs are fever, ADR, lameness, neurologic signs, dyspnea and death. Chronic disease can include fibrinous pericarditis and congestive heart failure. In endemic herds it can be cultured at 1 week of age and is common in healthy pigs; like most of these diseases, it is an opportunistic pathogen. Treatment of all these is a combination of bacterins, better sanitation and stress reduction.
• Erysipelothrix rhusiopathiae causes swine erysipelas: classic diamond-shaped skin lesions, fever, ADR, stiff gait, sitting posture, abortions, and sudden death.
• Streptococcus suis (Lancefield group D) causes streptococcal meningitis in 5-16 week old swine. Fever is the initial sign, progressing to anorexia, depression, ataxia, paddling, opisthotonus, seizures and death.
• Pseudorabies is caused by an alpha herpes virus and infects and kills several species (cattle, sheep, goats, dogs, cats, rodents, macaques and marmosets), but pigs are subclinical and latent hosts. Neonatal pigs get CNS signs: stumbling, salivation, nystagmus, opisthotonus and seizures. Once the CNS signs start, mortality is 100%. Older pigs get minor respiratory signs (sneezing, nasal discharge, cough) for a week, which can easily be confused with swine influenza.
• Porcine circovirus associated diseases (PCVAD): a constellation of diseases of multifactorial cause.

Pig with multisystemic wasting disease caused by PCV2.

Respiratory diseases

• Atrophic rhinitis is usually caused by a combination of Pasteurella multocida, Bordetella bronchiseptica, and Haemophilus parasuis, and it is exacerbated by other viral diseases, high ammonia levels, dust, and genetic factors.
• Pasteurellosis by itself (P. multocida) is caused by the toxins it produces. Signs are dyspnea, cough, anorexia, and fever. Morbidity and mortality are variable; usually they just have decreased weight gain. Gross lesions include consolidation, suppurative pleuritis and pericarditis, adhesions and pulmonary abscesses.
• Actinobacillus pleuropneumoniae produces hemolytic toxins that damage capillary endothelium, resulting in edema and fibrin deposition. Peracute disease is sudden death. Acute disease is fever, depression, anorexia, cyanosis, dyspnea and death in 36 hr. Chronic disease is cough, decreased weight gain and lameness. Recovered swine are carriers.
• Mycoplasma
  • M. hyorhinis is a common cell culture contaminant. In pigs 3-10 weeks of age it causes lethargy, anorexia, labored respiration, arched back, lameness and fever which abates in 2 weeks.
  • M. hyopneumoniae affects 3-6 month old pigs causing decreased growth and chronic cough, with low mortality. It is probably the most common cause of endemic pneumonia in swine.
• Porcine cytomegalovirus causes inclusion body rhinitis (IBR), with classic intranuclear inclusions. Disease is subclinical in pigs >3 weeks old; typical signs of this disease are fetal and piglet death, runting, pneumonia and poor weight gain.
• Swine influenza, caused by type A influenza virus, causes fever, conjunctivitis, rhinitis, nasal discharge, and a barking cough that lasts for 5-7 days with no mortality. Interspecies transmission readily occurs.
• Verminous pneumonia is caused mostly by Ascaris suum (also by Metastrongylus, but that has an indirect life cycle involving earthworms so doesn't often appear in lab housing). Ascaris has a direct life cycle involving migration of larvae through the liver to the lungs, where they are coughed up and swallowed to start all over again. Mucoid plugs containing adults an eggs obstruct the bronchioles of the diaphragmatic lobes, causing atelectasis. Neopredisan disinfectant (p-chloro-methyl cresol) is effective.

Gastrointestinal diseases

• Swine dysentery, caused by Brachyspira hyodysenteriae, usually causes severe diarrhea and fever, dehydration, weight loss and weakness. Spirochaetes can be seen in the crypts and lumen of the large bowel.
• Proliferative enteropathy, caused by Lawsonia intracellularis, affects post-weaned pigs and causes hemorrhagic diarrhea subsequent to stress.
• Colibacillosis is the most important diarrheal disease of neonatal to post-weaning swine.
• Clostridial enteritis is caused by C. perfringens type A (enteritis with low mortality) or type C (100% fatal necrotic enteritis in piglets born to non-immune sows).
• Salmonella typhimurium and S. cholerasuis, see above
• Transmissible gastroenteritis (TGE) is a coronavirus that cross-reacts with feline infectious peritonitis and canine coronavirus. Pigs get anorexia, vomiting, and diarrhea. Stomachs are distended with milk and the small intestine is distended and thin-walled. The most striking lesion is severe villus atrophy of the jejunum and ileum, causing massive loss of absorptive surface.
• Porcine rotavirus is a major cause of morbidity and mortality in very young pigs, with death due to dehydration. Rotaviruses are hard to kill in the environment.
• Balantidiasis, caused by Balantidium coli, invades necrotic tissue and is usually a sequel to other primary causes of enteritis. It is zoonotic. Most infections are subclinical and it is not considered a primary pathogen.
• Coccidiosis (usually Isospora suis but also Eimeria and Cryptosporidium parvum) affect 1-2 week old piglets. Yellow-gray diarrhea of varying consistency develops but piglets continue to nurse. Lesions are found in the jejunum and ileum.
• Giardiasis: causes formless feces but no pathologic lesions.
• Nematodiasis
  • Trichuris suis in the small intestine and cecum can cause profuse bloody diarrhea, emaciation and growth retardation. Because eggs don't become infective for 3-4 weeks, good sanitation works.
  • Strongyloides ransomi, the small intestinal threadworm, causes nonhemorrhagic diarrhea.

Skin disease

• Exudative epidermitis (greasy pig disease) is caused by Staphylococcus hyicus. In addition to the typical exudative dermatitis, it causes vesicles or ulcers in the mouth and tongue and on the snout. It is very persistent in the environment.
• Swine pox is a minor skin disease, causing classic pox lesions in the skin but not elsewhere.
• Mange is caused by Sarcoptes scabiei var suis and is pretty common.
• Lice are sucking lice (Haematopinus suis) which can result in anemia.
• Porcine dermatitis and nephropathy syndrome probably has multifactorial causes. A host of agents, including PCV2, PRRSV, Pasteurella multocida, Streptococcus suis, E. coli, Proteus, Haemophilus parasuis, Actinobacillus pleuropneumonias, Bordetella bronchiseptica, Arcanobacterium pyogenes, Staphylococcus aureus, and even Salmonella have been incriminated as causing this disease. The hallmark lesion is generalized vasculitis and glomerulonephritis suggestive type 3 hypersensitivity, with antibody-antigen complexes in the tissues.{4779}

Pig with typical skin lesions of PDNS.

Reproductive diseases

• Brucella suis causes abortion, infertility, metritis, lameness, orchitis, spondylitis and posterior paralysis. The European hare is a carrier. Gross lesions are abscesses resulting from bacteremia.
• Leptospira interrogans serovar pomona is the most common cause in swine, with late abortions, stillbirths and weak piglets. Hemorrhages are seen in the lungs and kidneys, and microscopically there is interstitial nephritis.
• Parvovirus (PPV) causes embryonic and fetal death when gilts are exposed during the first 70 days of gestation; otherwise most pigs have been exposed and are immune.
• Porcine Reproductive and Respiratory Syndrome (PRRS) was first identified in the late 1980s and has spread everywhere since. It is caused by an arterivirus. Clinical signs depend on age: late gestation abortions when infected during the 3rd trimester; dyspnea and tachypnea in newborns with 100% mortality; pneumonia and secondary bacterial infections in post-weaning pigs. The disease persists in swine without stimulating antibody production, making serologic screening inaccurate. Diagnosis is by viral isolation, FA, IHC or PCR along with clinical signs. Characteristic histologic lesions are multifocal lymphohistiocytic myocarditis, interstitial pneumonia, hypertrophy and hyperplasia of type II pneumocytes, and mild lymphohistiocytic choroiditis with cuffing of vessels in the meninges, choroid plexus and brain.

Metabolic and Nutritional diseases

• Porcine stress syndrome is a cascade of events in pigs with a mutation in the calcium release channel protein called the ryanodine receptor. Sarcoplasmic reticulum in skeletal muscle releases calcium when stressed by anaesthesia or other events, leading to the cascade of events. Susceptible strains are Yorkshire, Pietrain, Duroc, Landrace, and Poland China (abbreviated by the Army as You Poor Dumb Little Pigs). Initial signs include tachypnea, muscle rigidity and hyperthermia. Metabolic acidosis, myoglobinemia, hyperkalemia and hyperglycemia occur, followed by muscle rigidity and cardiovascular collapse. Dantrolene prevents PSS by decreasing calcium release from sarcoplasmic reticulum.
• Salt poisoning may be caused by eating too much salt, but the more common syndrome is water deprivation. Within a few hours, the pigs become tense and apprehensive, the nose twitches, and the head is elevated. There is a rhythmic chomping of the jaws, pigs become blind and deaf, and will eventually paddle continuously. Paradoxically, giving water just causes the hyperosmolarity in the CNS to turn into edema and exacerbates the problem.
• Gastric ulcers are found in a specific region of the stomach, the pars oesophagea. The pathogenesis is speculative. Pigs can acutely become pale and weak with vomiting of blood; or they can chronically be anemic and anorexic, with passage of dark feces. Usually only single pigs are affected, which helps differentiate this from salmonellosis and TGE.

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Sheep and Goats

Health screening for ruminants should include Johne's disease, brucellosis and internal and external parasites. In addition:{4776}

• Sheep: add Q fever, contagious ecthyma, casous lymphadenitis, Johne's disease, ovine progressive pneumonia
• Goats: add Q fever, caprine arthritis encephalitis, tuberculosis
• Cattle: add tuberculosis, respiratory diseases

• B. abortus: sheep, cattle, goats. Asymptomatic in cows, localizes in mammary lymph nodes and placenta causing abortion in 5th month and retained placenta. Organisms are shed in milk permanently.
• B. melitensis: sheep. Asymptomatic, lasts 3 months; some have third-trimester abortions. Can also cause third-trimester abortion in goats.
• B. ovis: ovine epididymitis and orchitis, testicular atrophy.

Strain 19 vaccine (live) induces an antibody response, wherease RB51 (attenuated) does not; they are used in young animals except bull calves (concern over orchitis and spread). Vaccine ameliorates clinical signs but does not prevent animals from becoming infected. Vaccination should only be done when animals aren't stressed.

Campylobacteriosis (vibriosis)

C. fetus subsp. intestinalis is the most important cause of late abortion in ewes in the US. C. fetus subsp. venerealis is the main cause of bovine campylobacterial abortions.

Clostridial diseases

Clostridium perfringens type C causes enterotoxemia in sheep, goats and cattle, generally fatal hemorrhagic enterocolitis during the first 72 hours of life; mortality is generally <15%. Trypsin inhibitors in colostrum prevent inactivation of the toxin, which injures epithelial cells and enters the bloodstream, leading to acute toxemia. A toxoid is available to be given to dams prior to parturition; an antitoxin is also available. Disease may become endemic.

Clostridium perfringens type D causes "pulpy kidney disease" (most often in sheep), so called because immediately post-mortem the kidneys are extremely necrotic and soft. The toxin is activated by trypsin. Young animals die within a couple of hours occasionally preceded by neurological signs. Pathognomonic signs are hyperglycemia and glucosuria and occur due to toxin effects on liver glycogen metabolism. Vaccination prevents this disease. Treatment, if the animals aren't dead already, is supportive.

Clostridium tetani (the toxins again) causes sporadic, acute and fatal neuropathy. The incubation period may be long, up to 3 weeks. Animals are bloated and spastic, have prolapsed third eyelids, a stiff gait, can't chew, and are febrile. Mortality is 100%, from respiratory failure. Necropsy is not rewarding; there will just be inflammation associated with the wound entry site. A toxoid is available as is antitoxin.

Clostridium novyi causes black disease (infectious necrotic hepatitis) or bighead, or red water (bacillary hemoglobinuria); C. chauvoei causes blackleg.

Clostridium septicum causes malignant edema, which is gas gangrene around local injury.

E. coli

Clinical signs vary with the type and site of infection. ETEC cause gastroenteritis and/or septicemia, cystitis and pyelonephritis, and abortions. Vaccines are available for cattle.

Corynebacterium pseudotuberculosis

The presumed cause of any draining, abscessed lymph nodes.

The list in LAM2 goes on and on... shortening to save time here...

Leptospirosis

Listeriosis

Lyme disease (borreliosis)

Mastitis

Moraxella bovis

Mycobacterial diseases

• M. bovis
• M. paratuberculosis (Johne's)

Pasteurellosis

Salmonellosis

Yersiniosis

Mycoplasmosis

Rickettsia

• Eperythrozoon and Haemobartonella
• Q fever: C. burnetii is a major cause of late abortion in sheep

Viral, chlamydial, prion

• Adenovirus
• Bluetongue (reovirus)
• Bovine leukemia virus
• Bovine viral diarrhea (flavivirus)
• Caprine arthritis encephalitis (lentivirus)
• Ovine progressive pneumonia (maedi, visna; retrovirus)
• Infectious bovine rhinotracheitis (herpes)
• Parainfluenza-3 (paramyxovirus)
• Respiratory syncytial viruses (paramyxovirus)
• Contagious ecthyma (orf; parapoxvirus)
• Foot and mouth disease (aphthovirus)
• Malignant catarrhal fever (gamma herpes)
• Pseudorabies (alpha herpes)
• Rabies (rhabdovirus)
• Vesicular stomatitis (rhabdovirus)
• Scrapie (prion)
• Enzootic abortion of ewes (chlamydial abortion)

Parasitic

Protozoan

• anaplasmosis
• babesiosis
• coccidiosis
• cryptosporidiosis
• giardiasis
• neosporosis (confused with toxoplasmosis until 1988)
• sarcocytosis
• toxoplasmosis
• trichomoniasis

Nematodes

• Haemonchus contortus
• Ostertagia
• Trichostrongylus
• Nematodirus
• Cooperia
• Strongyloides
• Bunostomum
• Oesophagostomum
• Chabertia
• Trichuris
• Dictyocaulus

Cestodes

• Moniezia and Thysanosoma
• Echinococcus
• Gid (Coenuris cerebralis from Taenia multiceps)

Trematodes

• Fascioliasis

Mites

Lice

Ticks