The acute stage of the disease, occurring most often in the spring and summer, begins one to three weeks after infection and lasts for two to four weeks. Clinical signs include a fever, petechiae, bleeding disorders, vasculitis, lymphadenopathy, discharge from the nose and eyes, and edema of the legs and scrotum. There are no outward signs of the subclinical phase. Clinical signs of the chronic phase include weight loss, pale gums due to anemia, bleeding due to thrombocytopenia, vasculitis, lymphadenopathy, dyspnea, coughing, polyuria, polydipsia, lameness, ophthalmic diseases such as retinal hemorrhage and anterior uveitis, and neurological disease. Dogs that are severely affected can die from this disease.

Although people can get ehrlichiosis, dogs do not transmit the bacteria to humans; rather, ticks pass on the "ehrlichia" organism. Clinical signs of human ehrlichiosis include fever, headache, eye pain, and gastrointestinal upset. It is quite similar to Rocky Mountain spotted fever, but rash is not seen in patients.

Cutaneous

- Alopecia

- Skin lesions

- Ulcerative or exfoliative dermatitis

Visceral

- Epistaxis (nose bleeds)

- Kidney failure > increased urination and drinking

- Ocular signs

- Progressive loss of weight with decreased appetite

- Swollen lymphnodes

In dogs, signs of distemper vary widely from no signs, to mild respiratory signs indistinguishable from kennel cough, to severe pneumonia with vomiting, bloody diarrhea and death.

Commonly observed signs are a runny nose, vomiting and diarrhea, dehydration, excessive salivation, coughing and/or labored breathing, loss of appetite, and weight loss. If neurological signs develop, incontinence may ensue. Central nervous system signs include a localized involuntary twitching of muscles or groups of muscles, seizures with salivation and jaw movements commonly described as "chewing gum fits", or more appropriately as "distemper myoclonus". As the condition progresses, the seizures worsen and advance to grand mal convulsions followed by death of the animal. The animal may also show signs of sensitivity to light, incoordination, circling, increased sensitivity to sensory stimuli such as pain or touch, and deterioration of motor capabilities. Less commonly, they may lead to blindness and paralysis. The length of the systemic disease may be as short as 10 days, or the start of neurological signs may not come until several weeks or months later. Those few that survive usually have a small tic or twitch of varying levels of severity. With time, this tic will usually diminish somewhat in its severity.

Three stages of rabies are recognized in dogs and other animals.

1. The first stage is a one- to three-day period characterized by behavioral changes and is known as the prodromal stage.

2. The second stage is the excitative stage, which lasts three to four days. It is this stage that is often known as "furious rabies" due to the tendency of the affected animal to be hyperreactive to external stimuli and bite at anything near.

3. The third stage is the paralytic stage and is caused by damage to motor neurons. Incoordination is seen due to rear limb paralysis and drooling and difficulty swallowing is caused by paralysis of facial and throat muscles. This disables the victim's ability to swallow, which causes saliva to pour from the mouth also the reason bites are the most clear way for the infection to spread is because the virus is most concentrated in the throat and cheeks causing major contamination to saliva. Death is usually caused by respiratory arrest.

A dog that survives distemper will continue to have both nonlife-threatening and life-threatening signs throughout its lifespan. The most prevalent nonlife-threatening symptom is hard pad disease. This occurs when a dog experiences the thickening of the skin on the pads of its paws as well as on the end of its nose. Another lasting symptom commonly is enamel hypoplasia. Puppies, especially, will have damage to the enamel of teeth that are not completely formed or those that have not yet grown through the gums. This is a result of the virus's killing the cells responsible for manufacturing the tooth enamel. These affected teeth tend to erode quickly.

Life-threatening signs usually include those due to the degeneration of the nervous system. Dogs that have been infected with distemper tend to suffer a progressive deterioration of mental abilities and motor skills. With time, the dog can acquire more severe seizures, paralysis, reduction in sight and incoordination. These dogs are usually humanely euthanized because of the immense pain and suffering they face.

Ehrlichiosis (; also known as canine rickettsiosis, canine hemorrhagic fever, canine typhus, tracker dog disease, and tropical canine pancytopenia is a tick-borne disease of dogs usually caused by the organism "Ehrlichia canis". "Ehrlichia canis" is the pathogen of animals. Humans can become infected by "E. canis" and other species after tick exposure. German Shepherd Dogs are thought to be susceptible to a particularly severe form of the disease, other breeds generally have milder clinical signs. Cats can also be infected.

Canine leishmaniasis (LEESH-ma-NIGH-ah-sis) is a zoonotic disease (see human leishmaniasis) caused by "Leishmania" parasites transmitted by the bite of an infected phlebotomine sandfly. Canine leishmaniasis was first identified in Europe in 1903, and in 1940, 40% of all dogs in Rome were determined to be positive for leishmaniasis. Traditionally thought of as a disease only found near the Mediterranean basin, 2008 research claims new findings are evidence that canine leishmaniasis is currently expanding in continental climate areas of northwestern Italy, far from the recognized disease-endemic areas along the Mediterranean coasts. Cases of leishmaniasis began appearing in North America in 2000, and, as of 2008, "Leishmania"-positive foxhounds have been reported in 22 U.S. states and two Canadian provinces.

Rabies is a viral zoonotic neuroinvasive disease which causes inflammation in the brain and is usually fatal. Rabies, caused by the rabies virus, primarily infects mammals. In the laboratory it has been found that birds can be infected, as well as cell cultures from birds, reptiles and insects. Animals with rabies suffer deterioration of the brain and tend to behave bizarrely and often aggressively, increasing the chances that they will bite another animal or a person and transmit the disease. Most cases of humans contracting the disease from infected animals are in developing nations. In 2010, an estimated 26,000 people died from rabies, down from 54,000 in 1990.

The domestic ferret is known to be affected by several distinct ferret health problems. Among the most common are cancers affecting the adrenal glands, pancreas, and lymphatic system. Viral diseases include canine distemper and influenza. Certain health problems have also been linked to ferrets being neutered before sexual maturity was reached. Certain colors of ferret may also carry a genetic defect known as Waardenburg syndrome. Similar to domestic cats, ferrets may also be affected by hairballs, or dental problems.

A canine vector-borne disease (CVBD) is one of "a group of globally distributed and rapidly spreading illnesses that are caused by a range of pathogens transmitted by arthropods including ticks, fleas, mosquitoes and phlebotomine sandflies." CVBDs are important in the fields of veterinary medicine, animal welfare, and public health. Some CVBDs are of zoonotic concern.

Many CVBD infect humans as well as companion animals. Some CVBD are fatal; most can only be controlled, not cured. Therefore, infection should be avoided by preventing arthropod vectors from feeding on the blood of their preferred hosts. While it is well known that arthropods transmit bacteria and protozoa during blood feeds, viruses are also becoming recognized as another group of transmitted pathogens of both animals and humans.

Some "canine vector-borne pathogens of major zoonotic concern" are distributed worldwide, while others are localized by continent. Listed by vector, some such pathogens and their associated diseases are the following:

- Phlebotomine sandflies (Psychodidae): "Leishmania amazonensis", "L. colombiensis", and "L. infantum" cause visceral leishmaniasis (see also canine leishmaniasis). "L. braziliensis" causes mucocutaneous leishmaniasis. "L. tropica" causes cutaneous leishmaniasis. "L. peruviana" and "L. major" cause localized cutaneous leishmaniasis.

- Triatomine bugs (Reduviidae): "Trypanosoma cruzi" causes trypanosomiasis (Chagas disease).

- Ticks (Ixodidae): "Babesia canis" subspecies ("Babesia canis canis", "B. canis vogeli", "B. canis rossi", and "B. canis gibsoni" cause babesiosis. "Ehrlichia canis" and "E. chaffeensis" cause monocytic ehrlichiosis. "Anaplasma phagocytophilum" causes granulocytic anaplasmosis. "Borrelia burgdorferi" causes Lyme disease. "Rickettsia rickettsii" causes Rocky Mountain spotted fever. "Rickettsia conorii" causes Mediterranean spotted fever.

- Mosquitoes (Culicidae): "Dirofilaria immitis" and "D. repens" cause dirofilariasis.

The most common symptoms include headache, muscle aches, and fatigue. A rash may occur, but is uncommon. Ehrlichiosis can also blunt the immune system by suppressing production of TNF-alpha, which may lead to opportunistic infections such as candidiasis.

Most of the signs and symptoms of ehrlichiosis can likely be ascribed to the immune dysregulation that it causes. A "toxic shock-like" syndrome is seen in some severe cases of ehrlichiosis. Some cases can present with purpura and in one such case the organisms were present in such overwhelming numbers that in 1991 Dr. Aileen Marty of the AFIP was able to demonstrate the bacteria in human tissues using standard stains, and later proved that the organisms were indeed Ehrlichia using immunoperoxidase stains.

Experiments in mouse models further supports this hypothesis, as mice lacking TNF-alpha I/II receptors are resistant to liver injury caused by ehrlichia infection.

3% of human monocytic ehrlichiosis cases result in death; however, these deaths occur "most commonly in immunosuppressed individuals who develop respiratory distress syndrome, hepatitis, or opportunistic nosocomial infections."

Rabies is a viral disease that exists in Haiti and throughout the world. It often causes fatal inflammation of the brain in humans and other mammals, such as dogs and mongooses in Haiti. The term "rabies" is derived from a Latin word that means "to rage"; rabid animals sometimes appear to be angry. Early symptoms can include fever and tingling at the site of exposure, followed by one or more of the following symptoms: violent movements, uncontrolled excitement, fear of water, an inability to move parts of the body, confusion, and loss of consciousness. Once symptoms appear, death is nearly always the outcome. The time period between contracting the disease and showing symptoms is usually one to three months; however, this time period can vary from less than a week to more than a year. The time between contraction and the onset of symptoms is dependent on the distance the virus must travel to reach the central nervous system.

Haiti is one of five remaining countries in the Americas where canine rabies is still a problem. It has the highest rate of human rabies deaths in the western hemisphere with an estimated two deaths each week. Only about seven deaths are reported to health authorities each year due to poor surveillance, limitations in diagnostic capacity, and lack of awareness and education about the disease among Haitians.

Adrenal disease, a growth of the adrenal glands that can be either hyperplasia or cancer, is most often diagnosed by signs like unusual hair loss, increased aggression, constant grooming of owner or other ferrets as well as themselves, difficulty urinating (caused by an enlarged prostate) or defecating, or agitation when urinating, and (in the case of females) an enlarged vulva. Signs of an enlarged prostate should be considered an emergency; even if the growth is benign, it can still cause a hormonal imbalance which can have devastating effects on the ferret's health.

Treatment options include surgery or cryosurgery to excise the affected glands, melatonin or deslorelin implants, which treat the symptoms but not the disease itself, and/or hormone therapy. The causes of adrenal disease are as yet uncertain, but speculated triggers include unnatural light cycles, diets based around processed ferret foods, and prepubescent neutering. It has also been suggested that there may be a hereditary component to adrenal disease.

Adrenal disease is usually detected during the spring or fall, as it affects the hormones that make the fur grow. When affected ferrets shed their winter coat, the fur does not grow back. The hair loss pattern is usually very specific for adrenal disease. It begins at the base of the tail and then continues up the back. Ferrets treated for adrenal disease may temporarily have severe hair loss as their bodies recover.

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 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.

Death rates during outbreaks were usually extremely high, approaching 100% in immunologically naïve populations. The disease was mainly spread by direct contact and by drinking contaminated water, although it could also be transmitted by air.

Initial symptoms include fever, loss of appetite, and nasal and eye discharges. Subsequently, irregular erosions appear in the mouth, the lining of the nose, and the genital tract. Acute diarrhea, preceded by constipation, is also a common feature. Most animals die six to twelve days after the onset of these clinical signs.

Cat flu is the common name for a feline upper respiratory tract disease. While feline upper respiratory disease can be caused by several different pathogens, there are few symptoms that they have in common.

While Avian Flu can also infect cats, Cat flu is generally a misnomer, since it usually does not refer to an infection by an influenza virus. Instead, it is a syndrome, a term referring to the fact that patients display a number of symptoms that can be caused by one or more of the following infectious agents (pathogens):

1. Feline herpes virus causing feline viral rhinotracheitis (cat common cold, this is the disease that is closely similar to cat flu)

2. Feline calicivirus—(cat respiratory disease)

3. "Bordetella bronchiseptica"—(cat kennel cough)

4. "Chlamydophila felis"—(chlamydia)

In South Africa the term cat flu is also used to refer to Canine Parvo Virus. This is misleading, as transmission of the Canine Parvo Virus rarely involves cats.

Rinderpest (also cattle plague or steppe murrain) was an infectious viral disease of cattle, domestic buffalo, and many other species of even-toed ungulates, including buffaloes, large antelope and deer, giraffes, wildebeests, and warthogs. The disease was characterized by fever, oral erosions, diarrhea, lymphoid necrosis, and high mortality. Death rates during outbreaks were usually extremely high, approaching 100% in immunologically naïve populations. Rinderpest was mainly transmitted by direct contact and by drinking contaminated water, although it could also be transmitted by air. After a global eradication campaign, the last confirmed case of rinderpest was diagnosed in 2011.

On 14 October 2010, the United Nations Food and Agriculture Organization (FAO) announced that field activities in the decades-long, worldwide campaign to eradicate the disease were ending, paving the way for a formal declaration in June 2011 of the global eradication of rinderpest. On 25 May 2011, the World Organisation for Animal Health announced the free status of the last eight countries not yet recognized (a total of 198 countries were now free of the disease), officially declaring the eradication of the disease. In June 2011, the United Nations FAO confirmed the disease was eradicated, making rinderpest only the second disease in history to be fully wiped out (outside laboratory stocks), following smallpox.

Rinderpest is believed to have originated in Asia, later spreading through the transport of cattle. The term "Rinderpest" is a German word meaning "cattle-plague". The rinderpest virus (RPV) was closely related to the measles and canine distemper viruses. The measles virus emerged from rinderpest as a zoonotic disease between 1000 and 1100 AD, a period that may have been preceded by limited outbreaks involving a virus not yet fully acclimated to humans.

Post-kala-azar dermal leishmaniasis (PKDL) is a recurrence of kala-azar that may appear on the skin of affected individuals months and up to 20 years after being partially treated, untreated or even in those considered adequately treated. In Sudan, they can be demonstrated in up to 60% of treated cases. They manifest as hypopigmented skin lesions (such as macules, papules, nodules), or facial redness. Though any organism causing kala-azar can lead to PKDL, it is commonly associated with "Leishmania donovani" which gives different disease patterns in India and Sudan. In the Indian variant, nodules enlarge with time and form plaques but rarely ulcerate, but nodules from the African variety often ulcerate as they progress. Nerve involvement is common in African variety but rare in Indian subcontinent. Histology demonstrates a mixture of chronic inflammatory cells; there can be macrophage or epitheloid granuloma. Parasite concentration is not consistent among studies, perhaps reflecting low sensitivity of diagnostic methods used in earlier entries.

Current approach to diagnosis involves 1. demonstration of parasite by microscopy, "in vitro" culture or animal inoculation; 2. immunodiagnosis of parasite antigen; 3. detection of parasite DNA in tissue. Newer PCR based tools have higher sensitivity and specificity. Emergence of PKDL has been reported in HIV affected individuals and may become a problem in future.

Sodium stibogluconate alone or in combination with rifampicin is used for the treatment of PKDL for a long course of up to 4 months. Compliance can be an issue for such a long course.

Globally, 59,000 people die from rabies each year. This is the equivalent of one person dying every nine minutes, with half of the people who die from rabies being under the age of 15. The Pan American Health Organization (PAHO) and the Pan American Center of foot-and-mouth disease (PANAFTOSA) led a mission to eliminate dog-mediated rabies in the American region by 2015. These organizations are cognizant of the regional control of rabies. The PAHO and PANAFTOSA visited Haiti in early December, 2013, and the objectives of the mission were to assess the status of Haiti’s rabies program as delivered by the Haitian Ministry of Agriculture, Natural Resources and Rural Development (MARNDR) and the Ministry of Health (MSPP). The mission was to seek opportunities for collaboration between Haiti, Brazil, and the Centers for Disease Control and Prevention (CDC) in Haiti.

Even in 2017, rabies in Haiti is still identified as a national problem, even with PEP proposed.

Puppies are frequently infected with coccidia from the feces of their mother, and are more likely to develop coccidiosis due to their undeveloped immune systems. Stress can trigger symptoms in susceptible animals.

Symptoms in young dogs include diarrhea with mucus and blood, poor appetite, vomiting, and dehydration. Untreated the disease can be fatal.

Treatment is routine and effective. Diagnosis is made by low-powered microscopic examination of the feces, which is generally replete with oocysts. Readily available drugs eliminate the protozoa or reduce them enough that the animal's immune system can clear the infection. Permanent damage to the gastrointestinal system is rare, and a dog will usually suffer no long-lasting negative effects.

Ehrlichiosis is a tickborne

bacterial infection, caused by bacteria of the family Anaplasmataceae, genera "Ehrlichia" and "Anaplasma". These obligate intracellular bacteria infect and kill white blood cells.

The average reported annual incidence is on the order of 2.3 cases per million people.

Mucocutaneous leishmaniasis is an especially disturbing form of cutaneous leishmaniasis, because it produces destructive and disfiguring lesions of the face. It is most often caused by "Leishmania braziliensis", but cases caused by "L. aethiopica" have also been described.

Mucocutaneous leishmaniasis is very difficult to treat. Treatment involves the use of pentavalent antimonial compounds, which are highly toxic (common side effects include thrombophlebitis, pancreatitis, cardiotoxicity and hepatotoxicity) and not very effective. For example, in one study, despite treatment with high doses of sodium stibogluconate for 28 days, only 30% of patients remained disease-free at 12 months follow-up. Even in those patients who achieve an apparent cure, as many as 19% will relapse. Several drug combinations with immunomodulators have been tested, for example, a combination of pentoxifylline (inhibitor of TNF-α) and a pentavalent antimonial at a high dose for 30 days in a small-scale (23 patients) randomised placebo-controlled study from Brazil achieved cure rates of 90% and reduced time to cure, a result that should be interpreted cautiously in light of inherent limitations of small-scale studies. In an earlier small-scale (12 patients) study, addition of imiquimod showed promising results which need yet to be confirmed in larger trials.

DFTD tumours are "large, solid, soft tissue masses usually with flattened, centrally ulcerated, and surfaces", which are "typically multicentric, appearing first in the oral, face, or neck regions", and are " to nodular aggregates of round to spindle-shaped cells, often within a pseudocapsule and divided into lobules by delicate fibrous septae". The disease is described as being aggressive, locally. Tumours can cover the eyes.

As Iain O'Neill notes, it also presents a "high rate of regional lymph node involvement and systemic metastasis"; of the avenues by which the cancer can spread systemically, metastasis to the lungs, spleen, and heart are observed, as is secondary "intracranial involvement". O'Neill also notes that "organ involvement and superimposed infection may... contribute to mortality." Moreover, growth of large tumours impedes feeding, and starvation is another cause of death in affected devils.

In humans, eosinophilic granulomas are considered a benign histiocytosis that occurs mainly in adolescents and young adults. Clinically, unifocal lytic lesions are found in bones such as the skull, ribs and femur. Because of this, bone pain and pathologic fractures are common.

Aside from the mosquito allergy cat, cats with EGC usually have allergy, ectoparasite infestation or possibly ringworm or other skin infection. Other implicated causes include traumatic damage, autoimmune disease or FeLV infection.