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.

Patients can present with fever, headache, myalgias, and malaise. Laboratory tests may reveal thrombocytopenia, leukopenia, and evidence of liver damage.

Signs and symptoms may include:

- fever

- severe headache

- muscle aches (myalgia)

- chills and shaking, similar to the symptoms of influenza

- nausea

- vomiting

- loss of appetite

- unintentional weight loss

- abdominal pain

- cough

- diarrhea,

- aching joints

- sensitivity to light

- weakness

- fatigue

- change in mental status (extreme confusion, memory loss, inability to comprehend environment- interaction, reading, etc.)

- temporary loss of basic motor skills

Symptoms may be minor, as evidenced by surveillance studies in high-risk areas. Gastrointestinal tract symptoms occur in less than half of patients and a skin rash is seen in less than 10% of patients. It is also characterized by a low number of platelets, a low number of white blood cells, and elevated serum transaminase levels in the majority of infected patients. Even though people of any age can get HGA, it is usually more severe in the aging or immune-compromised. Some severe complications may include respiratory failure, kidney failure, and secondary infections.

The most common symptoms are fever, headache, malaise, and muscle aches (myalgia). Compared to human granulocytic ehrlichiosis, rash is more common. Laboratory abnormalities include thrombocytopenia, leukopenia, and elevated liver tests.

The severity of the illness can range from minor or asymptomatic to life-threatening. CNS involvement may occur. A serious septic or toxic shock-like picture can also develop, especially in patients with impaired immunity.

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."

Ehrlichiosis ewingii infection is an infectious disease caused by an intracellular bacteria, "Ehrlichia ewingii". The infection is transmitted to humans by the tick, "Amblyomma americanum". This tick can also transmit "Ehrlichia chaffeensis", the bacteria that causes human monocytic ehrlichiosis (HME).

Human monocytotropic ehrlichiosis (HME) is a form of ehrlichiosis associated with "Ehrlichia chaffeensis". This bacterium is an obligate intracellular pathogen affecting monocytes and macrophages.

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.

Human granulocytic anaplasmosis (HGA) is a tick-borne, infectious disease caused by "Anaplasma phagocytophilum", an obligate intracellular bacterium that is typically transmitted to humans by ticks of the "Ixodes ricinus" species complex, including "Ixodes scapularis" and "Ixodes pacificus" in North America. These ticks also transmit Lyme disease and other tick borne diseases.

The bacteria infect white blood cells called neutrophils, causing changes in gene expression that prolong the life of these otherwise short-lived cells.

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.

Signs and symptoms of PHF include acute-onset fever, depression (sometimes profound), inappetance, mild colic-like symptoms, decreased manure production, profuse watery non-fetid diarrhea endotoxemia, edema due to protein imbalances, abortion by pregnant mares, and acute laminitis (20 to 40 percent of cases). Infected horses founder usually within three days of the initial symptoms, thought to be secondary to endotoxemia. Death may occur and is usually due to severe laminitis leading to founder.

Horses may not always display any other symptoms beyond a fever.

Potomac Horse Fever (PHF) is a potentially-fatal febrile illness affecting horses caused by the intracellular bacterium "Neorickettsia risticii". PHF is also known as Shasta River Crud and Equine Monocytic Ehrlichiosis. It was first described in areas surrounding the Potomac River northwest of Washington, D.C., in the 1980s, but cases have been described in many other parts of the United States, such as Minnesota, California, and Pennsylvania. Currently, it is found in more than 40 U.S. states and Canada.

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.

"Bartonella quintana" is transmitted by contamination of a skin abrasion or louse-bite wound with the faeces of an infected body louse ("Pediculus humanus corporis"). There have also been reports of an infected louse bite passing on the infection.

Tick paralysis results from injection of a toxin from tick salivary glands during a blood meal. The toxin causes symptoms within 2–7 days, beginning with weakness in both legs that progresses to paralysis. The paralysis ascends to the trunk, arms, and head within hours and may lead to respiratory failure and death. The disease can present as acute ataxia without muscle weakness.

Patients may report minor sensory symptoms, such as local numbness, but constitutional signs are usually absent. Deep tendon reflexes are usually decreased or absent, and ophthalmoplegia and bulbar palsy can occur.

Electromyographic (EMG) studies usually show a variable reduction in the amplitude of compound muscle action potentials, but no abnormalities of repetitive nerve stimulation studies. These appear to result from a failure of acetylcholine release at the motor nerve terminal level. There may be subtle abnormalities of motor nerve conduction velocity and sensory action potentials.

An emerging infectious disease (EID) is an infectious disease whose incidence has increased in the past 20 years and could increase in the near future. Emerging infections account for at least 12% of all human pathogens. EIDs are caused by newly identified species or strains (e.g. Severe acute respiratory syndrome, HIV/AIDS) that may have evolved from a known infection (e.g. influenza) or spread to a new population (e.g. West Nile fever) or to an area undergoing ecologic transformation (e.g. Lyme disease), or be "reemerging" infections, like drug resistant tuberculosis. Nosocomial (hospital-acquired) infections, such as methicillin-resistant Staphylococcus aureus are emerging in hospitals, and extremely problematic in that they are resistant to many antibiotics. Of growing concern are adverse synergistic interactions between emerging diseases and other infectious and non-infectious conditions leading to the development of novel syndemics. Many emerging diseases are zoonotic - an animal reservoir incubates the organism, with only occasional transmission into human populations.

Tick paralysis is the only tick-borne disease that is not caused by an infectious organism. The illness is caused by a neurotoxin produced in the tick's salivary gland. After prolonged attachment, the engorged tick transmits the toxin to its host. The incidence of tick paralysis is unknown. Patients can experience severe respiratory distress (similar to anaphylaxis).

The disease is classically a five-day fever of the relapsing type, rarely exhibiting a continuous course. The incubation period is relatively long, at about two weeks. The onset of symptoms is usually sudden, with high fever, severe headache, pain on moving the eyeballs, soreness of the muscles of the legs and back, and frequently hyperaesthesia of the shins. The initial fever is usually followed in a few days by a single, short rise but there may be many relapses between periods without fever. The most constant symptom is pain in the legs. Recovery takes a month or more. Lethal cases are rare, but in a few cases "the persistent fever might lead to heart failure". Aftereffects may include neurasthenia, cardiac disturbances and myalgia.

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.

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.

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

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.

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.

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.

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.