Porcine epidemic diarrhea virus (PED virus or PEDV) is a coronavirus that infects the cells lining the small intestine of a pig, causing porcine epidemic diarrhoea, a condition of severe diarrhea and dehydration. Older hogs mostly get sick and lose weight after being infected, where as newborn piglets usually die within five days of contracting the virus. PEDV cannot be transmitted to humans, nor contaminate the human food supply.

It was first discovered in Europe, but has become increasingly problematic in Asian countries, such as Korea, China, Japan, the Philippines, and Thailand. It has also spread to North America: it was discovered in the United States on May 5, 2013 in Indiana, and in Canada in the winter of 2014. In January 2014, a new variant strain of PEDV with three deletions, one insertion, and several mutations in S (spike) 1 region was identified in Ohio by the Animal Disease Diagnostic Lab of Ohio Department of Agriculture.

PEDV has a substantial economic burden given that it is highly infectious, resulting in significant morbidity and mortality in piglets. Morbidity and mortality rates were lower for vaccinated herds than for nonvaccinated herds, which suggests the emergence of a new PEDV field strain(s) for which the current vaccine, based on the CV777 strain, was partially protective. Consumers are likely to feel the effects of the viral disease in the form of higher prices for pork products.

Porcine circovirus(PCV) is a single-stranded DNA virus (class II), that is nonenveloped with an unsegmented circular genome. The viral capsid is icosahedral and approximately 17 nm in diameter. PCV is a member of the virus family Circoviridae.

PCVs are the smallest viruses replicating autonomously in eukaryotic cells.They replicate in the nucleus of infected cells, using the host polymerase for genome amplification.

There are 2 strains: type 1 and type 2. Porcine Circovirus Associated Disease is caused by porcine circovirus type 2 (PCV2).

PCV-1 (first identified in 1974) readily infects, but is not known to cause disease in swine; the type 2 has caused problems in recent years with the increasing occurrence of postweaning multisystemic wasting syndrome (PMWS), which over time results in significant depletion of lymphocytes; postmortem examination of diseased animals reveals enlarged lymph nodes and abnormal lung tissue.

The infectious agent responsible is a virus CSFV (previously called hog cholera virus) of the genus Pestivirus in the family Flaviviridae.CSFV is closely related to the ruminant pestiviruses that cause bovine viral diarrhoea and border disease.

The effect of different CSFV strains varies widely, leading to a wide range of clinical signs. Highly virulent strains correlate with acute, obvious disease and high mortality, including neurological signs and hemorrhages within the skin.

Less virulent strains can give rise to subacute or chronic infections that may escape detection, while still causing abortions and stillbirths. In these cases, herds in high-risk areas are usually serologically tested on a thorough statistical basis.

Infected piglets born to infected but subclinical sows help maintain the disease within a population. Other signs can include lethargy, fever, immunosuppression, chronic diarrhoea, and secondary respiratory infections. The incubation period of CSF ranges from 2 to 14 days, but clinical signs may not be apparent until after 2 to 3 weeks. Preventive state regulations usually assume 21 days

Streptococcus suis is a peanut-shaped, Gram-positive bacterium, and an important pathogen of pigs. Endemic in nearly all countries with an extensive pig industry, S. suis is also a zoonotic disease, capable of transmission to humans from pigs.

Humans can be infected with S. suis when they handle infected pig carcasses or meat, especially with exposed cuts and abrasions on their hands. Human infection can be severe, with meningitis, septicaemia, endocarditis, and deafness as possible outcomes of infection. Fatal cases of S. suis are uncommon, but not unknown.

Penicillin is the most common antibiotic used in treatment of S. suis infection; in cases with cardiac involvement (endocarditis), gentamicin should also be given for synergistic effect.

Erysipelothrix rhusiopathiae is a Gram-positive, catalase-negative, rod-shaped, nonspore-forming, nonacid-fast, nonmotile bacterium. The organism was first established as a human pathogen late in the 19th century. It may be isolated from soil, food scraps, and water contaminated by infected animals. It can survive in soil for several weeks. In pig faeces, the survival period of this bacterium ranges from 1 to 5 months It grows aerobically and anaerobically and does not contain endotoxin. Distributed worldwide, E. rhusiopathiae is primarily considered an animal pathogen, causing a disease known as erysipelas in animals (and erysipeloid in humans – see below). Turkeys and pigs are most commonly affected, but cases have been reported in other birds, sheep, fish, and reptiles In pigs, the disease is known as "diamond skin disease". The human disease called erysipelas is not caused by E. rhusiopathiae, but by various members of the genus Streptococcus.

It is most frequently associated as an occupational disease of butchers.

P. multocida causes a range of diseases in wild and domesticated animals, as well as humans. The bacterium can be found in birds, cats, dogs, rabbits, cattle, and pigs. In birds, P. multocida causes avian or fowl cholera disease; a significant disease present in commercial and domestic poultry flocks worldwide, particularly layer flocks and parent breeder flocks. P. multocida strains that cause fowl cholera in poultry typically belong to the serovars 1, 3, and 4. In the wild, fowl cholera has been shown to follow bird migration routes, especially of snow geese. The P. multocida serotype-1 is most associated with avian cholera in North America, but the bacterium does not linger in wetlands for extended periods of time. P. multocida causes atrophic rhinitis in pigs; it also can cause pneumonia or bovine respiratory disease in cattle. In humans, P. multocida is the most common cause of infection from wound infections after dog or cat bites. The infection usually shows as soft tissue inflammation within 24 hours. High leukocyte and neutrophil counts are typically observed, leading to an inflammatory reaction at the infection site (generally a diffuse, localized cellulitis). It can also infect other locales, such as the respiratory tract, and is known to cause regional lymphadenopathy (swelling of the lymph nodes). In more serious cases, a bacteremia can result, causing an osteomyelitis or endocarditis. The bacteria may also cross the blood–brain barrier and cause meningitis.

Pasteurella is a genus of Gram-negative, facultatively anaerobic bacteria. Pasteurella species are nonmotile and pleomorphic, and often exhibit bipolar staining ("safety pin" appearance). Most species are catalase- and oxidase-positive.The genus is named after the French chemist and microbiologist, Louis Pasteur, who first identified the bacteria now known as Pasteurella multocida as the agent of chicken cholera. Pathogenesi

Many Pasteurella species are zoonotic pathogens, and humans can acquire an infection from domestic animal bites. In cattle, sheep, and birds, Pasteurella species can cause a life-threatening pneumonia; in cats and dogs, however, Pasteurella is not a cause of disease, and constitutes part of the normal flora of the nose and mouth Pasteurella haemolytica is a species that infects mainly cattle and horses: P. multocida is the most frequent causative agent in human Pasteurella infection Common symptoms of pasteurellosis in humans include swelling, cellulitis, and bloody drainage at the site of the wound. Infection may progress to nearby joints, where it can cause further swelling, arthritis, and abscesses

Pasteurella spp. are generally susceptible to chloramphenicol, the penicillins, tetracycline, and the macrolides

The common occurrence of the bacteria is a reason to be medically proactive and defensive (antibacterial treatments are often necessary) if a bite occurs.

Coccidiosis is a parasitic disease of the intestinal tract of animals caused by coccidian protozoa. The disease spreads from one animal to another by contact with infected feces or ingestion of infected tissue. Diarrhea, which may become bloody in severe cases, is the primary symptom. Most animals infected with coccidia are asymptomatic, but young or immunocompromised animals may suffer severe symptoms and death.

While coccidia can infect a wide variety of animals, including humans, birds, and livestock, they are usually species-specific. One well-known exception is toxoplasmosis caused by Toxoplasma gondii.

Humans may first encounter coccidia when they acquire a young puppy or kitten that is infected. Other than T. gondii, the infectious organisms are canine and feline-specific and are not contagious to humans, unlike the zoonotic diseases.

Listeria is a genus of bacteria that, until 1992, contained 10 known species, each containing two subspecies. As of 2014, another five species were identified Named after the British pioneer of sterile surgery Joseph Lister, the genus received its current name in 1940. Listeria species are gram-positive, rod-shaped, and facultatively anaerobic, and do not produce endospores The major human pathogen in the Listeria genus is L. monocytogenes. It is usually the causative agent of the relatively rare bacterial disease listeriosis, a serious infection caused by eating food contaminated with the bacteria. The disease affects pregnant women, newborns, adults with weakened immune systems, and the elderly.

Listeriosis is a serious disease for humans; the overt form of the disease has a case-fatality rate around 20%. The two main clinical manifestations are sepsis and meningitis. Meningitis is often complicated by encephalitis, when it is known as meningoencephalitis, a pathology that is unusual for bacterial infections. L. ivanovii is a pathogen of mammals, specifically ruminants, and has rarely caused listeriosis in humans.The incubation period can vary between 3 and 70 days.

Listeriosis is an infectious but not contagious disease caused by the bacterium Listeria monocytogenes, far more common in domestics animals (domestic mammals and poultry), especially ruminants, than in human beings. It can also occur in feral animals—among others, game animals—as well as in poultry and other birds.

The causative bacterium lives in the soil and in poorly made silage and is acquired by ingestion. It is not contagious; over the course of 30-year observation period of sheep disease in Morocco, the disease only appeared in the late 2000s (decade) when feeding bag-ensiled corn became common In Iceland, the disease is called "silage sickness"

The disease is usually sporadic, but can occur as farm outbreaks in ruminants.

Three main forms are usually recognized throughout the affected species:

• encephalitis, the most common form in ruminants
• late abortion
• gastro-intestinal septicemia with liver damage, in monogastric species as well as in preruminant calves and lambs 

Listeriosis in animals can rarely be cured with antibiotics (tetracyclines, chloramphenicol and benzyl penicillin also) when diagnosed early, in goats, for example, by treating upon first noticing the disease's characteristic expression in the animal's face, but is generally fatal.

Derzsy's disease is caused by a virus from the Parvoviridae family. It affects geese and Muscovy ducks.

The virus is shed in the faeces and thus transmission is horizontal, via the direct faecal-oral route and also indirectly via fomites. Vertical transmission is also possible.

Clinical disease only occurs in young geese and ducks between birth and 4–5 weeks of age.
Epidemiology

Several genotypes have been described.The genotype is based upon the sequence of the VP3 protein.
Clinical signs and diagnosis

Acute disease leads to death in most birds between the ages of 7–10 days. Clinical signs are quite limited in those cases. Older animals tend to show severe systemic and neurological signs and diarrhoea. Adults do not show any clinical signs.

Viral isolation should be attempted for diagnosis, and immunofluorescence and electron microscopy can confirm the viral infection. Pathological changes may also help the diagnosis.