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.

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.

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.

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).

Diagnosis is based on a circular "bull's-eye" rash at the site of infection called erythema chronicum migrans, which is very similar to that seen in Lyme disease. However, the symptoms of STARI are mild, and resemble influenza, with fatigue, muscle pains, and headache. Fever is sometimes seen, but is not characteristic.

Clinical appearance of the disease includes depression, a serous nasal discharge, and sporadically minor facial inflammation in mild form of the disease. In severe form, there is severe inflammation of one or both infraorbital sinuses with edema of the surrounding tissue. The swelling can cause closure of one eye or both of them. Intermandibular space and wattles of corks do swell as a course of the disease .

Southern tick-associated rash illness (STARI) or Masters' disease is an emerging infectious disease related to Lyme disease that occurs in southeastern and south-central United States. It is spread by tick bites, but the organism that causes the infection is unknown.

Six syndromes are known to occur after infection with Marek's disease. These syndromes may overlap.

- Classical Marek's disease or neurolymphomatosis causes asymmetric paralysis of one or more limbs. With vagus nerve involvement, difficulty breathing or dilation of the crop may occur. Besides lesions in the peripheral nerves, there are frequently lymphomatous infiltration/tumours in the skin, skeletal muscle, visceral organs. Organs that are commonly affected include the ovary, spleen, liver, kidneys, lungs, heart, proventriculus and adrenals.

- Acute Marek's disease is an epidemic in a previously uninfected or unvaccinated flock, causing depression, paralysis, and death in a large number of birds (up to 80%). The age of onset is much earlier than the classic form; birds are four to eight weeks old when affected. Infiltration into multiple organs/tissue is observed.

- Ocular lymphomatosis causes lymphocyte infiltration of the iris (making the iris turn grey), unequal size of the pupils, and blindness.

- Cutaneous Marek's disease causes round, firm lesions at the feather follicles.

- Atherosclerosis is induced in experimentally infected chickens.

- Immunosuppression – Impairment of the T-lymphocytes prevents competent immunological response against pathogenic challenge and the affected birds become more susceptible to disease conditions such as coccidiosis and "Escherichia coli" infection . Furthermore, without stimulation by cell-mediated immunity, the humoral immunity conferred by the B-cell lines from the Bursa of Fabricius also shuts down, thus resulting in birds that are totally immunocompromised.

Pacheco's disease is an acute and often lethal infectious disease in psittacine birds. The disease is caused by a group of herpesviruses, "Psittacid herpesvirus 1" (PsHV-1), which consists of four genotypes. Birds which do not succumb to Pacheco's disease after infection with the virus become asymptomatic carriers that act as reservoirs of the infection. These persistently infected birds, often Macaws, Amazon parrots and some species of conures, shed the virus in feces and in respiratory and oral secretions. Outbreaks can occur when stress causes healthy birds who carry the virus to shed it. Birds generally become infected after ingesting the virus in contaminated material, and show signs of the disease within several weeks.

The main sign of Pacheco's disease is sudden death, sometimes preceded by a short, severe illness. If a bird survives Pacheco's disease following infection with PsHV-1 genotypes 1, 2 or 3, it may later develop internal papilloma disease in the gastrointestinal tract.

Susceptible parrot species include the African gray parrot, and cockatoo. Native Australian birds, such as the eclectus parrot, Bourke's parrot, and budgerigar are susceptible to Pacheco's disease, although the disease itself has not been found in Australia.

Marek's disease is a highly contagious viral neoplastic disease in chickens. It is named after József Marek, a Hungarian veterinarian. Marek's disease is caused by an alphaherpesvirus known as 'Marek's disease virus' (MDV) or "Gallid alphaherpesvirus 2" (GaHV-2). The disease is characterized by the presence of T cell lymphoma as well as infiltration of nerves and organs by lymphocytes. Viruses "related" to MDV appear to be benign and can be used as vaccine strains to prevent Marek's disease. For example, the related Herpesvirus of Turkeys (HVT), causes no apparent disease in turkeys and continues to be used as a vaccine strain for prevention of Marek's disease (see below). Birds infected with GaHV-2 can be carriers and shedders of the virus for life. Newborn chicks are protected by maternal antibodies for a few weeks. After infection, microscopic lesions are present after one to two weeks, and gross lesions are present after three to four weeks. The virus is spread in dander from feather follicles and transmitted by inhalation.

Infectious coryza is a serious bacterial disease of chickens which affects respiratory system and it is manifested by inflammation of the area below the eye, nasal discharge and sneezing...The disease is found all over the world causing high economic losses. Economic loss is due to stumping off and reduction of egg production in case of laying chickens. The disease was discovered early 1930s by considering clinical signs

Common clinical signs of Tyzzer’s Disease include watery diarrhea, depression, emaciation, and a ruffled coat. Other observed clinical signs include melena, depression, lethargy, and decreased temperature. In muskrats, this disease is characterized by extensive hemorrhaging within the lower intestine and abdomen. Due to the fast-acting nature of this disease, infected individuals often do not live long enough to exhibit symptoms. It is not uncommon for an infected animal to die within 1-10 days of disease contraction.

During necropsy, inflammation of the ileum, cecum, and colon are commonly present. Perhaps the most distinctive trait of this disease, however, is the grayish yellow necrotic lesions found on the liver of diseased animals. The number of these spots present can range from one to countless. Occasionally, lesions are discovered in the lower intestinal tract and heart as well. Even with physical signs and symptoms present, a conclusive diagnosis is dependent upon the presence of "C. piliforme" within the liver of the infected animal.

Symptoms of meningococcemia are, at least initially, similar to those of influenza. Typically, the first symptoms include fever, nausea, myalgia, headache, arthralgia, chills, diarrhea, stiff neck, and malaise. Later symptoms include septic shock, purpura, hypotension, cyanosis, petechiae, seizures, anxiety, and multiple organ dysfunction syndrome. Acute respiratory distress syndrome and altered mental status may also occur. The petichial rash appear with the 'star-like' shape. Meningococcal sepsis has a greater mortality rate than meningococcal meningitis, but the risk of neurologic sequelae is much lower.

Tyzzer’s disease is an acute epizootic bacterial disease found in rodents, rabbits, dogs, cats, birds, pandas, deer, foals, cattle, and other mammals including gerbils. It is caused by the spore-forming bacterium "Clostridium piliforme", formerly known as "Bacillus piliformis". It is an infectious disease characterized by necrotic lesions on the liver, is usually fatal, and is present worldwide. Animals with the disease become infected through oral ingestion of the bacterial spores and usually die within a matter of days. Animals most commonly affected include young, stressed animals in laboratory environments, such as immature rodents and rabbits. Most commonly affected wild animals include muskrats "(Ondatra zibethicus)" and occasionally cottontail rabbits "(Lepus sylvaticus)". Even today, much remains unknown about Tyzzer’s disease, including how and why it occurs.

The patient with meningococcal meningitis typically presents with high fever, nuchal rigidity (stiff neck), Kernig's sign, severe headache, vomiting, purpura, photophobia, and sometimes chills, altered mental status, or seizures. Diarrhea or respiratory symptoms are less common. Petechiae are often also present, but do not always occur, so their absence should not be used against the diagnosis of meningococcal disease. Anyone with symptoms of meningococcal meningitis should receive intravenous antibiotics before the results of lumbar puncture, as delay in treatment worsens the prognosis.

Pogosta disease is a viral disease, established to be identical with other diseases, Karelian fever and Ockelbo disease. The names are derived from the words Pogosta, Karelia and Ockelbo, respectively.

The symptoms of the disease include usually rash, as well as mild fever and other flu-like symptoms; in most cases the symptoms last less than 5 days. However, in some cases, the patients develop a painful arthritis. There are no known chemical agents available to treat the disease.

It has long been suspected that the disease is caused by a Sindbis-like virus, a positive-stranded RNA virus belonging to the Alphavirus genus and family Togaviridae. In 2002 a strain of Sindbis was isolated from patients during an outbreak of the Pogosta disease in Finland, confirming the hypothesis.

This disease is mainly found in the Eastern parts of Finland; a typical Pogosta disease patient is a middle-aged person who has been infected through a mosquito bite while picking berries in the autumn. The prevalence of the disease is about 100 diagnosed cases every year, with larger outbreaks occurring in 7-year intervals.

Pacheco's disease is an eponymously named disease; it is named after the Brazilian veterinarian, Genesio Pacheco, who first came across the disease in 1929, in an outbreak affecting the turquoise-fronted amazon parrot, "Amazona aestiva". Initially, Pacheco's disease was thought to be a manifestation of avian psittacosis. The causative agent of the disease, a herpesvirus, was not identified until 1975.

Feline spongiform encephalopathy is a disease that affects the brains of felines. It is caused by proteins called prions.

Chronic Lyme disease is a generally unrecognised diagnosis that encompasses "a broad array of illnesses or symptom complexes for which there is no reproducible or convincing scientific evidence of any relationship to "B. burgdorferi" infection." There is no clinical evidence that "chronic" Lyme disease is caused by a persistent infection. It is distinct from post-treatment Lyme disease syndrome, a set of lingering symptoms which may persist after successful treatment of infection with Lyme spirochetes. The symptoms of "chronic Lyme" are generic and non-specific "symptoms of life".

A number of alternative treatments are promoted for "chronic Lyme disease", of which possibly the most controversial and harmful is long-term antibiotic therapy, particularly intravenous antibiotics. Most medical authorities advise against long-term antibiotic treatment for Lyme disease, though they agree that some patients do experience lingering symptoms. Following disciplinary proceedings by State medical licensing boards in the United States, a subculture of "Lyme literate" physicians has successfully lobbied for specific legal protections, exempting them from the standard of care and Infectious Diseases Society of America treatment guidelines. This "troubling" political interference in medical care has been criticised as an example of "legislative alchemy", the process whereby pseudomedicine is legislated into practice.

Feline spongiform encephalopathy (FSE) is a prion disease thought to be related or identical to Bovine spongiform encephalopathy (BSE).This disease is known to affect domestic and captive feline species. Lezmi S. et al. (2003), suggested that this infectious agent might be spread by both haematogenous and nervous pathways. Like BSE, this disease can take several years to develop. It is probable, but not proven, that the affected animals contract the disease by eating contaminated bovine meat.

Whipple's disease is a rare, systemic infectious disease caused by the bacterium "Tropheryma whipplei". First described by George Hoyt Whipple in 1907 and commonly considered a gastrointestinal disorder, Whipple's disease primarily causes malabsorption but may affect any part of the body including the heart, brain, joints, skin, lungs and the eyes. Weight loss, diarrhea, joint pain, and arthritis are common presenting symptoms, but the presentation can be highly variable and approximately 15% of patients do not have these classic signs and symptoms.

Whipple's disease is significantly more common in men, with 87% of the patients being male. When recognized and treated, Whipple's disease can usually be cured with long-term antibiotic therapy; if the disease is left untreated, it is ultimately fatal.

The most common symptoms are diarrhea, abdominal pain, weight loss, and joint pains. The joint pains may be due to migratory non-deforming arthritis, which may occur many years before any digestive tract symptoms develop; they tend to involve the large joints but can occur in any pattern and tend not to damage the joint surface to the point that the joint becomes deformed. Fever and chills occur in a small proportion of people.

In its more advanced form, malabsorption (insufficient absorption of nutrients from the diet) leads to wasting and the enlargement of lymph nodes in the abdomen. Neurological symptoms (discussed below) are more common in those with the severe form of the abdominal disease. Chronic malabsorptive diarrhea leads to the poor absorption of fat, causing steatorrhea (fatty, offensive stool), flatulence, and abdominal distension. Protein-losing enteropathy may also occur, causing depletion of albumin, a blood protein, which may lead to peripheral edema caused by the lowered oncotic pressures.

Hyperpigmentation of the skin occurs in almost half; some also have skin nodules. Various eye problems, such as uveitis, may occur; this is typically associated with deteriorating vision and pain in the affected eye. Endocarditis (infection of the heart valve) has been reported in a small number of cases, sometimes in people with no other symptoms of Whipple's disease; this is typically noticed as breathlessness and leg swelling due to fluid accumulation as the heart is unable to pump fluid through the body.

Of those affected by Whipple's disease, 10–40% of people have problems related to the involvement of the brain; the symptoms relate to the part of the brain that is affected. The most common problems are dementia, memory loss, confusion, and decreased level of consciousness. Eye movement disturbances and myorhythmia (rapidly repetitive movements of the muscles) of the face, together referred to as "oculomasticatory myorhythmia", are highly characteristic for Whipple's disease. Weakness and poor coordination of part of the body, headaches, seizures, as well as a number of more uncommon neurological features, are present in some cases.

The term "chronic Lyme disease" is often applied to several different sets of people. One usage refers to people suffering from the symptoms of untreated and disseminated late-stage Lyme disease: arthritis, peripheral neuropathy and/or encephalomyelitis. The term is also applied to people who have had the disease in the past and some symptoms remain after antibiotic treatment, which is also called post-Lyme disease syndrome. A third and controversial use of the term applies to patients with nonspecific symptoms, such as fatigue, who show no objective evidence they have been infected with Lyme disease in the past, since the standard diagnostic tests for infection are negative.

The Centers for Disease Control and Prevention state that some people after a "course of antibiotics will have lingering symptoms of fatigue, pain, or joint and muscle aches. In some cases, these can last for more than 6 months. Although often called 'chronic Lyme disease', this condition is properly known as 'post-treatment Lyme disease syndrome' (PTLDS)". This is estimated to occur in less than 5% of people who had Lyme disease and were treated.

While it is undisputed people can have severe symptoms, the cause and appropriate treatment are controversial. The symptoms may represent "for all intents and purposes" fibromyalgia or chronic fatigue syndrome. A few doctors attribute these symptoms to persistent infection with "Borrelia", or co-infections with other tick-borne pathogens, such as "Ehrlichia" and "Babesia". Other doctors believe that the initial infection may cause an autoimmune reaction that continues to cause serious symptoms even after the bacteria have been eliminated by antibiotics. A review looked at several animal studies that found persistence of live but disabled spirochetes following treatment of "B. burgdorferi" infection with antibiotics. The authors noted that none of the lingering spirochetes were associated with inflamed tissues and criticized the studies for not considering adequately the different pharmacodynamics and pharmacokinetics of the antibiotics used to treat the animals in the trials versus what would be expected to be used to treat humans. The authors concluded, "There is no scientific evidence to support the hypothesis that such spirochetes, should they exist in humans, are the cause of post-Lyme disease syndrome."

Major US medical authorities, including the Infectious Diseases Society of America, the American Academy of Neurology, and the National Institutes of Health, have stated there is no convincing evidence that "Borrelia" is involved in the various symptoms classed as chronic Lyme disease, and advise against long-term antibiotic treatment as ineffective and possibly harmful. Prolonged antibiotic therapy presents significant risks and can have dangerous side effects. Randomized placebo-controlled studies have shown that antibiotics offer no sustained benefit in people with "chronic Lyme"; with evidence of both placebo effects and significant adverse effects from such treatment. An advocacy group called the International Lyme And Associated Diseases Society (ILADS) argues the persistence of "B. burgdorferi" may be responsible for manifestations of late Lyme disease symptoms. It has questioned the generalizability and reliability of some of the above trials and the reliability of the current diagnostic tests.

The histiocytosis of Rosai–Dorfman disease can occur in lymph nodes, causing lymphadenopathy, or can occur outside lymph nodes in extranodal disease.

The symptoms of Cherry X disease vary greatly depending on the host. On cherry hosts symptoms can usually first be seen on the fruits, causing them to be smaller in size with a leathery skin. Pale fruit is common at harvest time. It is common for symptoms to first be seen in a single branch. The branch may lose its older leaves, and the leaves tend to be smaller with a bronzed complexion.

The rootstock that the cherry is grafted onto can play a significant role in the disease symptoms seen. Rootstocks of Mahaleb cherry exhibit different symptoms from stocks of Colt, Mazzard, or Stockton Morello. When the scion is grafted onto Mahaleb, symptoms consistent with Phytophthora root rot can be seen. To distinguish between root rot and x-disease the wood under the bark at the graft union should be examined. If it is x-disease the wood at the union will have grooves and pits this causes a browning of the phloem and shows the cells in decline. This rapid decline is caused by the rootstock cells near the graft union dying in large quantities. Foliage begins to turn yellow and the curl upward and inward toward the leaf midrib. Trees infected with Mahaleb rootstock die by late summer or early the following year.

When Cherries are grafted onto Colt, Mazzard, or Stockton Morello rootstocks, there is a different range of symptoms. Affected leaves are smaller than normal and the foliage may be sparse. Dieback of shoot tips is common as the disease progresses. Fruit on branches are smaller, lighter, pointed, low sugar content, poor flavor, and a bitter taste.

Peaches are the next most common economic fruit host of the X-disease. Symptoms can be seen after about two months single branches will begin to show symptoms of their individual leaves. These leaves curl up and inward with irregular yellow to reddish-purple spots. These spots can drop out leaving “shotholes”. Leaves that are affected by the disease will fall prematurely. After 2–3 years the entire tree will show symptoms.