Lymphoid leucosis is a disease that affects chickens, caused by the retrovirus "Avian leukosis virus".

It is a neoplastic disease caused by a virus, which may take the form of a tumor of the bursa of Fabricius and may metastasize to other tissues of the chicken and cause enlargement and swelling of the abdomen.

Symptoms include enlargement of abdomen, bursa, weight loss, weakness and emaciation, and depression. The disease is more likely to affect chicken around five to eight months of age who are more vulnerable. Green diarrhea tends to develops at the terminal stage.

In rabbits of the genus "Sylvilagus" (cottontail rabbits) living in the Americas, myxomatosis causes only localized skin tumors, but the European rabbit ("Oryctolagus cuniculus") is more severely affected. At first, normally the disease is visible by lumps (myxomata) and puffiness around the head and genitals. It may progress to acute conjunctivitis and possibly blindness; however, this also may be the first visible symptom of the disease. The rabbits become listless, lose appetite, and develop a fever. Secondary bacterial infections occur in most cases, which cause pneumonia and purulent inflammation of the lungs. In cases where the rabbit has little or no resistance, death may take place rapidly, often in as little as 48 hours; most cases result in death within 14 days. Often the symptoms like blindness make the infected rabbit more vulnerable to predators.

Porcine circoviral disease (PCVD) and Porcine circovirus associated disease (PCVAD), is a disease seen in domestic pigs. This disease causes illness in piglets, with clinical signs including progressive loss of body condition, visibly enlarged lymph nodes, difficulty in breathing, and sometimes diarrhea, pale skin, and jaundice. PCVD is very damaging to the pig-producing industry and has been reported worldwide. PCVD is caused by porcine circovirus type 2 (PCV-2).

The North American industry endorses "PCVAD" and European use "PCVD" to describe this disease.

After an incubation period of up to seven days, the signs associated with swine vesicular disease occur. The first sign is a transient mild fever. Other signs include:

- Vesicles in the mouth and on the snout and feet

- Lameness and an unsteady gait, shivering and jerking–type leg movements

- Ruptured vesicles can cause ulcers on limbs and feet, and foot pads may be loosened.

Young animals are more severely affected. Recovery often occurs within a week. There is no mortality.

Swine vesicular disease has the same clinical signs as foot-and-mouth disease, and can only be diagnosed by laboratory testing.

Porcine enzootic pneumonia is caused by "Mycoplasma hyopneumoniae" and describes an important respiratory disease of pigs.

It is part of the Porcine Respiratory Disease Complex along with Swine Influenza, PRRS and Porcine circovirus 2, and even though on its own it is quite a mild disease, it predisposes to secondary infections with organisms such as "Pasteurella multocida".

Clinical signs are most commonly seen in pigs over 8 weeks of age, and the disease occurs worldwide. Transmission is horizontal and vertical from sows.

Crayfish plague, "Aphanomyces astaci", is a water mold that infects crayfish, most notably the European "Astacus" which dies within a few weeks of being infected. When experimentally tested, species from Australia, New Guinea and Japan were also found to be susceptible to the infection.

Rabbits helped keep vegetation in their environments short through grazing and short grasses are conducive to habitation by the butterfly, "Plebejus argus""." When the population of rabbits experienced a decline due to Myxomatosis, grass lengths increased, limiting the environments in which "P. argus" could live, thereby contributing to the decline of the butterfly population.

Clinical signs are normally only seen in either piglets less than 3 weeks old or pregnant sows.

Signs in piglets include rhinitis, pneumonia, anaemia, fever and sudden death. Black discoloration around the eyes is often seen and gastrointestinal and neurological signs are also reported.

Signs in pregnant sows include reproductive failure, genital ulceration and agalactia.

Both PMWS and porcine dermatitis and nephropathy syndrome (PDNS) are associated to PCV-2. Many pigs affected by the circovirus also seem to develop secondary bacterial infections, like Glässer disease ("Haemophilus parasuis"), pulmonary pasteurellosis, colibacilosis, salmonellosis and others. Postmortem lesions occur in multiple organs, especially in lymphoid tissues and lung, giving rise to the term "multisystemic". Lesions may also affect the skin, kidney, reproductive tissue, brain, or blood vessels.

Wasting pigs is the most common sign of PMWS infection, increasing the mortality rate significantly.

Aujeszky's disease, usually called pseudorabies in the United States, is a viral disease in swine that has been endemic in most parts of the world. It is caused by "Suid herpesvirus 1" (SuHV1). Aujeszky's disease is considered to be the most economically important viral disease of swine in areas where hog cholera has been eradicated. Other mammals, such as humans, cattle, sheep, goats, cats, dogs, and raccoons, are also susceptible. The disease is usually fatal in these animal species bar humans.

The term "pseudorabies" is found inappropriate by many people, as SuHV1 is a herpesvirus and not related to the rabies virus.

Research on SuHV1 in pigs has pioneered animal disease control with genetically modified vaccines. SuHV1 is now used in model studies of basic processes during lytic herpesvirus infection, and for unravelling molecular mechanisms of herpesvirus neurotropism.

Pigs usually cough and may show more severe respiratory signs if secondary bacteria have invaded. This may lead to signs of pneumonia and systemic involvement.

Diagnosis relies on culture and isolation of the bacteria but this can be challenging.

PCR, ELISA, fluorescent antibody testing and post-mortem findings all help in making the diagnosis.

Foot-and-mouth disease or hoof-and-mouth disease (Aphthae epizooticae) is an infectious and sometimes fatal viral disease that affects cloven-hoofed animals, including domestic and wild bovids. The virus causes a high fever for approximately two to six days, followed by blisters inside the mouth and on the feet that may rupture and cause lameness.

Foot-and-mouth disease (FMD) has very severe implications for animal farming, since it is highly infectious and can be spread by infected animals comparatively easily through contact with contaminated farming equipment, vehicles, clothing, feed and by domestic and wild predators. Its containment demands considerable efforts in vaccination, strict monitoring, trade restrictions, quarantines and occasionally the culling of animals.

Susceptible animals include cattle, water buffalo, sheep, goats, pigs, antelope, deer, and bison. It has also been known to infect hedgehogs and elephants; llamas and alpacas may develop mild symptoms, but are resistant to the disease and do not pass it on to others of the same species. In laboratory experiments, mice, rats, and chickens have been successfully infected by artificial means, but they are not believed to contract the disease under natural conditions. Humans are very rarely infected.

The virus responsible for the disease is a picornavirus, the prototypic member of the genus "Aphthovirus". Infection occurs when the virus particle is taken into a cell of the host. The cell is then forced to manufacture thousands of copies of the virus, and eventually bursts, releasing the new particles in the blood. The virus is genetically highly variable, which limits the effectiveness of vaccination.

Zoonoses are infectious diseases of animals (usually vertebrates) that can naturally be transmitted to humans.

Major modern diseases such as Ebola virus disease and salmonellosis are zoonoses. HIV was a zoonotic disease transmitted to humans in the early part of the 20th century, though it has now evolved to a separate human-only disease. Most strains of influenza that infect humans are human diseases, although many strains of swine and bird flu are zoonoses; these viruses occasionally recombine with human strains of the flu and can cause pandemics such as the 1918 Spanish flu or the 2009 swine flu. "Taenia solium" infection is one of the neglected tropical diseases with public health and veterinary concern in endemic regions. Zoonoses can be caused by a range of disease pathogens such as viruses, bacteria, fungi and parasites; of 1,415 pathogens known to infect humans, 61% were zoonotic. Most human diseases originated in animals; however, only diseases that routinely involve animal to human transmission, like rabies, are considered direct zoonosis.

Zoonoses have different modes of transmission. In direct zoonosis the disease is directly transmitted from animals to humans through media such as air (influenza) or through bites and saliva (rabies). In contrast, transmission can also occur via an intermediate species (referred to as a vector), which carry the disease pathogen without getting infected. When humans infect animals, it is called reverse zoonosis or anthroponosis. The term is from Greek: ζῷον "zoon" "animal" and νόσος "nosos" "sickness".

The course of fasciolosis in humans has 4 main phases:

- Incubation phase: from the ingestion of metacercariae to the appearance of the first symptoms; time period: few days to 3 months; depends on number of ingested metacercariae and immune status of host

- Invasive or acute phase: fluke migration up to the bile ducts. This phase is a result of mechanical destruction of the hepatic tissue and the peritoneum by migrating juvenile flukes causing localized and or generalized toxic and allergic reactions. The major symptoms of this phase are:

- Fever: usually the first symptom of the disease;

- Abdominal pain

- Gastrointestinal disturbances: loss of appetite, flatulence, nausea, diarrhea

- Urticaria

- Respiratory symptoms (very rare): cough, dyspnoea, chest pain, hemoptysis

- Hepatomegaly and splenomegaly

- Ascites

- Anaemia

- Jaundice

- Latent phase: This phase can last for months or years. The proportion of asymptomatic subjects in this phase is unknown. They are often discovered during family screening after a patient is diagnosed.

- Chronic or obstructive phase:

This phase may develop months or years after initial infection. Adult flukes in the bile ducts cause inflammation and hyperplasia of the epithelium. The resulting cholangitis and cholecystitis, combined with the large body of the flukes, are sufficient to cause mechanical obstruction of the biliary duct. In this phase, biliary colic, epigastric pain, fatty food intolerance, nausea, jaundice, pruritus, right upper-quadrant abdominal tenderness, etc., are clinical manifestations indistinguishable from cholangitis, cholecystitis and cholelithiasis of other origins. Hepatic enlargement may be associated with an enlarged spleen or ascites. In case of obstruction, the gall bladder is usually enlarged and edematous with thickening of the wall (Ref: Hepatobiliary Fascioliasis:

Sonographic and CT Findings in 87 Patients During the InitialPhase and Long-Term Follow-Up. Adnan Kabaalioglu, Kagan Ceken, Emel Alimoglu, Rabin Saba, Metin Cubuk, Gokhan Arslan, Ali Apaydin. AJR 2007; 189:824–828). Fibrous adhesions of the gall bladder to adjacent organs are common. Lithiasis of the bile duct or gall bladder is frequent and the stones are usually small and multiple.

Swine vesicular disease is most commonly brought into a herd by the introduction of a subclinically infected pig.

The disease can be transmitted in feed containing infected meat scraps, or by direct contact with infected feces (such as in an improperly cleaned truck).

The incubation period for foot-and-mouth disease virus has a range between one and 12 days. The disease is characterized by high fever that declines rapidly after two or three days, blisters inside the mouth that lead to excessive secretion of stringy or foamy saliva and to drooling, and blisters on the feet that may rupture and cause lameness. Adult animals may suffer weight loss from which they do not recover for several months, as well as swelling in the testicles of mature males, and in cows, milk production can decline significantly. Though most animals eventually recover from FMD, the disease can lead to myocarditis (inflammation of the heart muscle) and death, especially in newborn animals. Some infected ruminants remain asymptomatic carriers, but they nonetheless carry FMDV and may be able to transmit it to others. Pigs cannot serve as asymptomatic carriers.

Zoonotic transmission can occur in any context in which there is companionistic (pets), economic (farming, etc.), predatory (hunting, butchering or consuming wild game) or research contact with or consumption of animals, animal products, or animal derivatives (vaccines, etc.).

Respiratory infection is usually asymptomatic in pigs more than 2 months old, but it can cause abortion, high mortality in piglets, and coughing, sneezing, fever, constipation, depression, seizures, ataxia, circling, and excess salivation in piglets and mature pigs. Mortality in piglets less than one month of age is close to 100%, but it is less than 10% in pigs between one and six months of age. Pregnant swine can reabsorb their litters or deliver mummified, stillborn, or weakened piglets. In cattle (see next section), symptoms include intense itching followed by neurological signs and death. In dogs, symptoms include intense itching, jaw and pharyngeal paralysis, howling, and death Any infected secondary host generally only lives two to three days.

Genital infection appears to have been common in a great part of the 20th century in many European countries in swine herds, where boars from boar centres were used for natural service of sows or gilts. This disease manifestation has always been asymptomatic in affected pigs, and presence of the infection on a farm was detected only because of cases in cattle showing pruritus on the hindquarters (vaginal infection, see below).

In susceptible animals other than swine, infection is usually fatal, and the affected animals most often show intense pruritus in a skin area.

Pruritus in Aujeszky's disease is considered a phantom sensation, and virus has never been found at the site of pruritus.

Inclusion Body Rhinitis, also known as IBR or Cytomegalic Inclusion Disease, is a pig disease caused by porcine cytomegalovirus, which is a member of the herpesvirus family. It is a notifiable disease that is found worldwide. It is spread both vertically and horizontally and prevalence is high.

It is not a zoonosis but the risk to humans that receive pig organ transplants is currently under investigation.

Cysticerci can develop in any voluntary muscles in humans. Invasion of muscle by cysticerci can cause myositis, with fever, eosinophilia, and muscular pseudohypertrophy, which initiates with muscle swelling and later progress to atrophy and fibrosis. In most cases, it is asymptomatic since the cysticerci die and become calcified.

A large burden of adult worms in the intestines promotes symptoms such as nausea, heartburn, dyspepsia, and diarrhea from two to seven days after infection, while small worm burdens generally are asymptomatic. Eosinophilia presents early and increases rapidly.

The great majority of trichinosis infections have either minor or no symptoms and no complications. There are two main phases for the infection: enteral (affecting the intestines) and parenteral (outside the intestines). The symptoms vary depending on the phase, species of "Trichinella", quantity of encysted larvae ingested, age, sex, and host immunity.

The term neurocysticercosis is generally accepted to refer to cysts in the parenchyma of the brain. It presents with seizures and, less commonly, headaches. Cysticerca in brain parenchyma are usually 5–20 mm in diameter. In subarachnoid space and fissures, lesions may be as large as 6 cm in diameter and lobulated. They may be numerous and life-threatening.

Cysts located within the ventricles of the brain can block the outflow of cerebrospinal fluid and present with symptoms of increased intracranial pressure.

Racemose neurocysticercosis refers to cysts in the subarachnoid space. These can occasionally grow into large lobulated masses causing pressure on surrounding structures.

Neurocysticercosis involving the spinal cord, most commonly presenting as back pain and radiculopathy.

Dutch elm disease (DED) is caused by a member of the sac fungi (Ascomycota) affecting elm trees, and is spread by elm bark beetles. Although believed to be originally native to Asia, the disease was accidentally introduced into America and Europe, where it has devastated native populations of elms that did not have resistance to the disease. It has also reached New Zealand. The name "Dutch elm disease" refers to its identification in 1921 and later in the Netherlands by Dutch phytopathologists Bea Schwarz and Christine Buisman who both worked with Professor Johanna Westerdijk. The disease affects species in the genera "Ulmus" and "Zelkova", therefore it is not specific to the Dutch elm hybrid.