SECTION 15 Infectious Diseases

Section Editor: Lynn F. Guptill, DVM, PhD, DACVIM (Small Animal)

Bartonellosis

Blastomycosis

Borreliosis (Lyme Disease)

Brucellosis in Dogs

Campylobacteriosis

Canine Distemper Virus

Canine Infectious Tracheobronchitis (Kennel Cough)

Ehrlichiosis and Anaplasmosis in Dogs

Feline Coronavirus

Feline Immunodeficiency Virus

Feline Leukemia Virus

Feline Upper Respiratory Infection

Giardiasis

Helicobacteriosis

Hepatozoonosis in Dogs

Histoplasmosis

Leishmaniasis

Leptospirosis

Methicillin-Resistant Staphylococcus Infections

Neosporosis in Dogs

Parvovirus in Cats

Parvovirus in Dogs

Protothecosis in Dogs

Pythiosis

Rabies

Rocky Mountain Spotted Fever

Tetanus

Toxoplasmosis

Tritrichomoniasis in Cats

Bartonellosis

Lynn F. Guptill, DVM, PhD, DACVIM (Small Animal)

BASIC INFORMATION

TREATMENT AND FOLLOW-UP

Treatment Options

No antibiotics have been proven effective for clearing Bartonella infections. Antibiotics that are commonly used include doxycycline and azithromycin. Treatment is recommended when an animal has clinical signs consistent with bartonellosis and no other cause is found for those signs. Treatment is often continued for at least 4-6 weeks. Treatment of asymptomatic animals is not recommended.

Follow-up Care

So little is known about treatment of Bartonella infections that follow-up testing is difficult to define. Sometimes a repeated blood culture is recommended in cats and tests for antibodies are repeated in dogs and cats. Because the length of time that antibodies persist after treatment is unknown, it is difficult to know the best time at which to do follow-up testing.

Bartonella infections do not result in immunity to bartonellosis. Control of fleas and ticks is the most effective means of preventing infection. A thorough flea and tick control program should be instituted for any animal with suspected bartonellosis. No vaccines are available for the disease.

Prognosis

Prognosis has not been established in animals. B. henselae causes cat scratch disease in people, as well as numerous other illnesses. Other Bartonella species are also associated with clinical illnesses in humans, some of which are serious. Immunocompromised people are especially susceptible to Bartonella infections, and clinical infections can be life-threatening. Precautions should be taken to minimize any bites or scratches from animals infected with Bartonella.

SPECIAL INSTRUCTIONS:

Blastomycosis

Anisa D. Dunham, AS, RVT, Lynn F. Guptill, DVM, PhD, DACVIM (Small Animal)

BASIC INFORMATION

Description

Blastomycosis is a fungal infection that usually starts in the lungs and then spreads to other parts of the body. Dogs and cats are both susceptible, but the disease occurs most often in dogs.

Cause

Blastomycosis is caused by the fungus Blastomyces dermatitidis. It is an organism that grows in and receives its nourishment from dead or decaying organic matter in the soil. It can survive in a wide range of moistures and temperatures. In the United States, it occurs most commonly in the Ohio, Mississippi, Missouri, Tennessee, and St. Lawrence River valleys. It can also be found in the southern Great Lakes region and in the mid-Atlantic states.

Infection occurs most commonly via inhalation or ingestion of the fungus from the environment. Infection may be limited to the lungs or may spread to multiple sites in the body.

Clinical Signs

Signs may initially be nonspecific and include lethargy, decreased appetite, and weight loss. Increased respiratory rate, difficulty breathing, and coughing may occur. Inflammation of the eyes, vision changes, enlarged lymph nodes (glands), and lameness from bony involvement are other possible signs.

Skin lesions occur in about half of the cases and are usually crusty bumps that drain a thick liquid. Organisms present in this liquid may spread the infection if it contaminates an open wound. Feet and nail beds are sometimes affected.

Altered mental attitude and difficulty walking are signs of central nervous system (primarily brain) disease. Other organs that may be affected include the testicles, prostate, and mammary glands (breast tissue). Gastrointestinal signs are uncommon.

Diagnostic Tests

Routine laboratory tests and chest x-rays are commonly recommended to investigate the clinical signs. X-rays of the legs may be done if lameness and bone pain are present. Blood tests are available for blastomycosis at certain outside laboratories. Although these tests are sensitive, false-negative and false-positive results can occur.

Finding the organism in affected tissues is the best diagnostic test. Needle aspiration or biopsy of an enlarged lymph node, skin lesion, blind eye, or other affected tissue may be done. A tracheal wash (collecting fluid from the airway through a catheter inserted into the windpipe) or bronchoscopy (examination of the airway through a fiberoptic viewing scope) may be considered if the lungs are involved. In cases of central nervous system involvement, a spinal tap may be considered to collect cerebrospinal fluid. The fluid is then submitted for analysis and culture. In some cases, the fungal agent can be cultured from infected tissues.

TREATMENT AND FOLLOW-UP

Treatment Options

The oral antifungal drugs, itraconazole and fluconazole, are generally considered effective but must be given for a prolonged period (months). Ketoconazole may be less expensive, but it is also less effective and has more side effects. Intravenous amphotericin B may be needed in animals with severe disease, especially if they do not respond to or do not tolerate oral medications. Amphotericin B is used cautiously, because it is toxic to the kidneys. Some forms are less toxic than others.

Seriously ill animals often require hospitalization, with intensive treatment and monitoring for the first several days of treatment. Dogs with severe lung disease may need supplemental oxygen. Death of the fungal organisms that occurs within the first few days of therapy may make the lung changes temporarily worse. Eyes that are blind and have persistent inflammation or glaucoma may be surgically removed.

Follow-up Care

Periodic recheck visits and repeated laboratory testing are required for several months to monitor the response to treatment and for side effects of the medications. Treatment is continued for at least 2-3 months, and for 1 month beyond the disappearance of all clinical signs.

After therapy is completed, the animal is commonly re-evaluated for up to 6 months to assess for relapses, which can occur in as many as 20-25% of treated animals. Strict adherence to treatment protocols is needed for the best response.

Prognosis

Prognosis is variable and depends on the extent and severity of the disease, as well as the initial response to treatment. Prognosis is better in animals with mild clinical signs or signs limited to one organ system. Prognosis is guarded (uncertain) in animals with widespread disease, central nervous system involvement, or severe involvement of any organ system.

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Borreliosis (Lyme Disease)

Lynn F. Guptill, DVM, PhD, DACVIM (Small Animal)

BASIC INFORMATION

Description

Borreliosis (Lyme disease) is a tick-borne disease that affects animals and people worldwide.

Causes

Borreliosis is one of a large group of tick-transmitted diseases caused by spirochete bacteria. This handout focuses on Lyme disease. The causative agent of Lyme disease in the United States is Borrelia burgdorferi, which is transmitted most commonly by deer ticks. Most cases of Lyme disease in the United States occur in the eastern coastal states and upper midwestern states. Lyme disease primarily affects dogs; cats are much more resistant to the disease.

Clinical Signs

Approximately 5-10% of dogs exposed to B. burgdorferi develop signs of Lyme disease, which is a low number. Initially, fever, lethargy, decreased appetite, and lameness are the most common signs. Lameness tends to shift from one leg to another over several weeks. Joint swelling and enlarged lymph nodes may occur. Multiple joints may be affected. Inflammation of the eyes (uveitis) may develop.

Rarely, and possibly more frequently in Labrador and golden retrievers, severe kidney disease occurs. Dogs with kidney disease often have sudden onset of lethargy, decreased appetite, vomiting, and weight loss. This manifestation of Lyme disease may progress rapidly to kidney failure.

Diagnostic Tests

Routine laboratory (blood and urine) tests, abdominal and joint x-rays, and an abdominal ultrasound may initially be recommended to investigate the source of the clinical signs. Biochemistry panels may show low blood protein levels and evidence of kidney malfunction or failure. Urine analysis may show increased protein in the urine, poor ability of the kidneys to concentrate the urine, or both. A joint tap and analysis of joint fluid may also be recommended.

Tests for antibodies to B. burgdorferi may be done on blood samples. Two tests may be run 2-3 weeks apart to determine whether the antibody levels are increasing. In dogs that have been vaccinated for Lyme disease, special tests may be needed to differentiate whether the antibodies are from the vaccination or from natural exposure to the bacteria. Dogs with positive antibody tests may not have clinical disease; they may only have been exposed to the bacteria.

Bacterial culture is not often practical but may be attempted. Skin biopsies from near the site of attachment of a tick may provide the best tissue to culture. Polymerase chain reaction (PCR) tests for bacterial DNA may be done in some cases (when available) on biopsies of skin or joint tissue.

TREATMENT AND FOLLOW-UP

Treatment Options

Treatment is recommended when the history, clinical signs, and laboratory test results are consistent with possible Lyme disease. Doxycycline is the most commonly recommended antibiotic and is usually administered for 3-6 weeks. Doxycycline has anti-inflammatory properties that may also be helpful. Amoxicillin, given for 1 month, is also considered an effective treatment. Side effects of doxycycline and amoxicillin in dogs are usually limited to mild vomiting or diarrhea. These drugs are often given with food to decrease these side effects.

Nonsteroidal antiinflammatory drugs (NSAIDs) may be recommended to relieve joint pain. (See also the handout on Immune-Mediated Arthritis.) Side effects of NSAIDs include vomiting, diarrhea, and sometimes stomach or intestinal ulceration. Stop the medication and notify your veterinarian immediately if any of these problems occur.

Antibiotic treatment of dogs that are clinically healthy but have a positive screening test for B. burgdorferi is considered controversial. Dogs with kidney disease require specific treatment for that disorder in addition to antibiotic treatment. (See also the handouts on Protein-Losing Nephropathy in Dogs and Acute Kidney Failure.) NSAIDs must be used with caution in animals with kidney disease.

Follow-up Care

B. burgdorferi may be difficult to completely clear from an infected dog, and clinical signs may recur weeks to months after treatment. Treatment also does not protect the animal against reinfection. Vaccination may be recommended in some areas where Lyme disease is common.

Ticks should be removed from dogs each day during the tick season. Strict tick control is an important means of preventing exposure to Lyme disease. Sometimes it is recommended that dogs exposed to B. burgdorferi be periodically tested for protein in their urine.

Prognosis

Most dogs treated for Lyme disease have a good prognosis, although relapse, re-exposure, and reinfection are possible. Dogs with severe kidney disease attributed to Lyme disease have a poor prognosis.

SPECIAL INSTRUCTIONS:

Brucellosis in Dogs

Anisa D. Dunham, AS, RVT, Lynn F. Guptill, DVM, PhD, DACVIM (Small Animal)

BASIC INFORMATION

Description

Brucellosis is a zoonotic disease (a disease that can be transmitted from animals to humans) that affects primarily reproductive organs. It can also infect other tissues of the body, such as intervertebral discs of the spine, eyes, and kidneys.

Cause

Brucellosis in dogs is caused by the bacterial organism Brucella canis. Transmission usually occurs during breeding, at birth, or from intimate contact with infected animals, possibly via inhalation of aerosols associated with abortion or vaginal discharges. The organisms reside within cells, making them difficult to eliminate.

Clinical Signs

Reproductive problems include failure to conceive after breeding, abortion of dead puppies, production of stillborn or weak puppies, and testicular abnormalities. Nonreproductive problems may include back pain, lameness, weakness, and partial paralysis. Uveitis, an inflammation of the eye, may also be seen.

Diagnostic Tests

Initially, routine laboratory tests or x-rays may be recommended, depending on the clinical signs. Diagnosis of brucellosis can be made based on several tests, such as the following:

• Blood tests are the primary method of diagnosis. Some rapid, in-clinic tests are very sensitive and can have false-positive results. Positive tests must be confirmed by specialized assays done at outside reference laboratories, such as state diagnostic laboratories.

• Bacterial culture of the blood may be done, but false-negative results may occur, because the bacteria are not always present in the blood. Urine, semen, and intervertebral disc material may also be cultured.

Semen analysis may be done in infertile male dogs. Abnormalities seen may include immature or deformed sperm. Biopsy and microscopic evaluation of reproductive tissues can support the diagnosis. Other tests may be indicated to rule out other diseases that cause similar clinical signs.

TREATMENT AND FOLLOW-UP

Treatment Options

Treatment for brucellosis may not be advisable, since the infection can be zoonotic, and eradication from tissues is uncertain and difficult to prove. If infected dogs are treated, they must be removed from breeding programs and neutered. Combinations of antibiotics are needed to treat the disease. The combination of a tetracycline (such as doxycycline, minocycline) and an aminoglycoside (such as gentamicin) antibiotic is most likely to be effective. Resolving the infection is difficult, and relapses are common. Multiple courses of therapy separated by 1-2 months may be needed. (See the handouts on Discospondylitis and Anterior Uveitis for more details on the treatment of these two conditions.)

Follow-up Care

Periodic recheck visits and repeated testing (x-rays, laboratory tests) are usually needed to monitor response to treatment. Blood tests for brucellosis may be repeated every 3-6 months to monitor for relapse.

Kennels containing animals that are positive for brucellosis are usually quarantined and infected animals removed. All dogs in the kennel are then tested monthly, and the kennel is released from quarantine only after all dogs have had two consecutive negative tests. Cleaning and disinfection procedures must be carefully followed. People working with infected animals should wear gloves and other appropriate personal protective equipment.

Prevention

Preventive measures are very important in breeding kennels and in any facility that houses a large number of dogs. New animals should be quarantined until two negative test results are obtained, 1 month apart. Dogs that leave the facility should be tested again before being allowed to return.

Prognosis

Although adult dogs are not often seriously ill, relapses are common. Since brucellosis can be transmitted to people and there is no known cure for brucellosis, euthanasia of infected dogs should be considered. All breeding animals should be tested for brucellosis 3-4 weeks before each breeding. Dogs used as blood donors are also commonly tested.

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Campylobacteriosis

Lynn F. Guptill, DVM, PhD, DACVIM (Small Animal)

BASIC INFORMATION

Description

Campylobacteriosis is an infection associated with diarrhea. It affects many species of animals, including dogs, cats, and cattle, as well as humans.

Causes

Campylobacteriosis is caused by several species of gram-negative bacteria in the genus Campylobacter. Transmission occurs when the organism is swallowed, often in water or food contaminated with feces. The organism can persist in the environment for several days, and possibly longer at cooler temperatures and when contained in organic material.

Clinical Signs

Dogs and cats are often asymptomatic carriers. Clinical signs are believed to develop more often (and are more severe) in animals that are young, are immune suppressed, or have another infection. Animals with campylobacteriosis are likely to be at risk for other intestinal infections, such as coccidiosis, giardiasis, or Salmonella infection. Diarrhea may contain mucus or blood and is often watery. A more widespread (systemic) disease has been reported in a few dogs, with signs of fever, decreased appetite, or jaundice (yellow color to the skin and mucous membranes of the eyes and mouth).

Diagnostic Tests

Diagnosis of campylobacteriosis may be suspected based on the clinical presentation and can be confirmed through several laboratory tests. Testing can involve the following:

• Microscopic examinations of fecal samples using specialized methods may identify the curved (“gull-wing” shaped) Campylobacter bacteria. Helicobacter bacteria may look similar; however, so other tests are needed to confirm campylobacteriosis.

• Culture of fresh feces or a rectal swab is often recommended, and specialized culture conditions are required. The best culture results are achieved when feces are transported to the laboratory quickly.

• Additional testing on the cultured bacteria may be recommended to determine which Campylobacter species is present.

• Identification of the species can be important in locating the source of the infection and whether it is likely to be transmissible to humans.

Laboratory tests, other fecal assays, x-rays, and other tests may be recommended if affected animals are systemically ill and to rule out other diseases that cause similar clinical signs.

TREATMENT AND FOLLOW-UP

Treatment Options

The effectiveness of antibiotic therapy for campylobacteriosis in dogs and cats is unknown. It is possible that the diarrhea may stop without treatment in some animals. It is also not known whether antibiotics will stop the shedding of the bacteria in the feces. Antibiotics that are commonly prescribed include erythromycin and second-generation cephalosporins. Fluoroquinolone antibiotics, metronidazole, and sulfadimethoxine are not often used, because Campylobacter species can become resistant to these drugs.

Follow-up Care

Strict sanitation and hygiene practices are needed to limit the spread of Campylobacter organisms and prevent reinfection. Crowding and close confinement of multiple animals should be avoided. Fecal material must be removed daily. Clean all organic material (feces, dirt) from all surfaces (cages, kennels, food bowls) prior to disinfecting them. Bathing the animals during treatment may be helpful, because it removes fecal material and decreases bacterial contamination.

Some animals continue to shed Campylobacter even when treated with antibiotics.

Campylobacter species are transmissible to humans and can cause severe gastrointestinal disease, particularly in immune-compromised individuals. Caution should be exercised (wear gloves, wash hands thoroughly) when handling and treating animals with campylobacteriosis.

Prognosis

Prognosis is good for most animals with campylobacteriosis.

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Canine Distemper Virus

Lynn F. Guptill, DVM, PhD, DACVIM (Small Animal)

BASIC INFORMATION

Description

Canine distemper virus (CDV) is very contagious and infects the respiratory tract, the gastrointestinal (GI) tract, and the central nervous system (CNS, including brain and spinal cord). The disease can be prevented by vaccination.

Cause

CDV is an enveloped virus closely related to measles virus. It is highly concentrated in respiratory tract secretions and is also found in other body fluids, such as urine. CDV is commonly spread through the air and survives in cold, freezing environments. The virus can be destroyed by sunlight, high heat, drying, and many common disinfectants.

Clinical Signs

Clinical signs vary widely in severity. Signs may be very mild, with only fever, lethargy, and slight nasal or eye discharge. Severe systemic infection occurs most often in young puppies and unvaccinated adult dogs. Clinical signs in severe cases may include fever, watery or cloudy nasal and eye discharge, and coughing that may be accompanied by difficulty breathing. Decreased appetite, vomiting, and diarrhea may also occur. Examination of the eyes with an ophthalmoscope may reveal inflammation in the retina.

CNS signs include seizures, behavioral changes, weakness, and difficulty walking. Involuntary repetitive contractions (tic, myoclonus) of certain muscles, often in one limb, and twitching of facial muscles may be seen. Neurologic signs may occur at the same time as respiratory and GI signs, or they may occur several weeks after recovery from those signs.

Other findings may include thickened foot pads (known as hard pad disease); abnormal tooth enamel (pits, discoloration); and dry, painful eyes from decreased tear production. In some cases, infected dogs have minimal clinical signs initially, then months to years later develop CNS signs. This variant of CDV disease is called old dog distemper.

Diagnostic Tests

No single test is available to make the diagnosis of CDV infection, so a number of tests are usually recommended to search for evidence of the disease, such as the following:

• A complete blood count may show low numbers of lymphocytes (a form of white blood cell affected by the virus).

• A biochemistry panel may show blood protein abnormalities.

• Analysis of cerebrospinal fluid (CSF) taken by a spinal tap may be recommended and may show increased numbers of lymphocytes and high protein concentrations.

• X-rays of the chest and abdomen may be recommended if respiratory or GI tract signs are present.

• Tests for antibodies to CDV in the blood and/or CSF may help identify an active infection.

• Special stains on scrapings or swabs taken from the conjunctiva, skin, or other samples can sometimes reveal viral components in the cells, but false-negative results are common.

Other tests may be recommended to rule out other diseases that cause similar clinical signs.

TREATMENT AND FOLLOW-UP

Treatment Options

Dogs with suspected CDV infection should be isolated from other dogs because of the highly contagious nature of the virus. No drug is available that will destroy the virus or rid it from the body, so supportive care is usually instituted.

Supportive care for respiratory and GI infection may include intravenous fluids and antivomiting medications. Nebulization and physical therapy (coupage) of the chest may be done to loosen and remove thickened respiratory secretions. Secretions are also cleaned from the nose and eyes. Antibiotics may be needed to treat secondary bacterial infections.

Animals with CNS disease may require anticonvulsant medications to control seizures, and steroids (prednisone) may be used in some animals to treat CNS inflammation.

Follow-up Care

Animals that appear to recover from respiratory and/or GI illness may develop CNS signs a few weeks to months later. Close monitoring is needed to watch for neurologic abnormalities. Recovering dogs may shed virus for several weeks, and care must be exercised to minimize or prevent interaction with other dogs, particularly dogs that are not vaccinated.

Prior to disinfection of cages and floors, all organic material must be removed. Disinfectants must contact treated surfaces for prolonged periods, depending on label directions. Immunity to CDV persists for many years following recovery from infection.

Prognosis

Animals with mild respiratory or GI tract signs may recover; however, many infected dogs will develop CNS disease. Prognosis for dogs with CNS disease is guarded (uncertain) to poor. Some dogs may recover but have permanent problems, such as seizures (that can be controlled with medication), vision abnormalities, and/or involuntary muscle tics. Euthanasia may be considered for severely ill animals that do not respond to supportive therapy.

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Canine Infectious Tracheobronchitis (Kennel Cough)

Lynn F. Guptill, DVM, PhD, DACVIM (Small Animal)

BASIC INFORMATION

Description

Canine infectious tracheobronchitis (ITB), also known as kennel cough, results from infection of the respiratory tract with one or more viruses and bacteria. It is highly contagious.

Causes

The most common causes include canine parainfluenza virus, canine adenovirus 2, canine influenza virus, and bacteria such as Bordetella bronchiseptica and Mycoplasma species. ITB may develop from a single agent, or it may be a mixed infection. Common mixed infections involve B. bronchiseptica, canine parainfluenza virus, and/or canine adenovirus 2.

Viruses and B. bronchiseptica are spread through the air via close contact or by fomites (contaminated inanimate objects). Direct contact with infected secretions is the most common way that ITB spreads from dog to dog. Clinical disease often follows exposure to other infected dogs at kennels, dog parks, and dog shows.

Clinical Signs

The most common sign is coughing that often comes in spasms. The cough may be dry and hacking (“goose honk”) or productive (gagging or coughing up secretions). These signs are sometimes mistaken for something caught in the dog’s throat. Coughing episodes may be triggered by excitement, activity, or pressure on the neck (such as pulling against a collar).

Pneumonia and other generalized signs (nasal discharge, fever, decreased appetite, respiratory difficulty) may occur with complicated or serious infections. Unvaccinated and young dogs are most susceptible to complicated ITB. Secondary bacterial infections may also lead to bronchopneumonia.

Diagnostic Tests

Classic clinical signs and a history of recent exposure to other dogs are suggestive of ITB. Routine laboratory tests, such as a complete blood cell count and biochemistry profile, are often normal unless pneumonia or other complications are present. Chest x-rays may be recommended if pneumonia is suspected.

Special procedures, such as a tracheal wash (collecting fluid from the airway through a catheter inserted into the windpipe) or bronchoscopy (examination of the airway through a fiberoptic viewing scope), may be needed in complicated ITB cases or in dogs with pneumonia. Collected fluids are usually analyzed microscopically and submitted for bacterial culture and antibiotic susceptibility testing. Tests for antibodies in the blood and cultures for viruses may be done in some cases but are not often needed.

TREATMENT AND FOLLOW-UP

Treatment Options

Treatment for uncomplicated ITB is mainly supportive and involves administration of cough-suppressant medications. Cough suppressants are not recommended if the cough is productive or if pneumonia is present. Increasing the humidity in the environment can ease breathing and loosen respiratory secretions. Most uncomplicated infections resolve with time and do not require antibiotics. Antibiotics may be given to treat complicated ITB or secondary bacterial infections.

Dogs with pneumonia may require intensive care in an isolation ward, with intravenous fluids, supplemental oxygen, and antibiotics. Inhalation therapy with saline, a bronchodilator drug, and/or antibiotics may also be recommended.

Follow-up Care

It is important to prevent the spread of this disease to other dogs by taking the following steps:

• Isolate dogs with ITB from other dogs until all clinical signs have resolved.

• Keep recovered dogs away from unvaccinated or immune-compromised dogs and puppies.

• Most of the infectious agents that cause ITB are inactivated by bleach. Disinfect all items (cages, bowls, brushes) that have come in contact with the infected dog with a solution of bleach diluted (1:32) in water.

• ITB may be transmitted by fomites and by a person who has been exposed to an infected dog. To prevent this type of transmission, isolation of infected dogs and strict disinfection of facilities and equipment is essential. It is sometimes necessary to close facilities that house dogs for awhile when outbreaks of ITB occur.

Vaccines are available for B. bronchiseptica, parainfluenza virus, and adenovirus 2. Puppies are initially given two or three vaccinations 2-3 weeks apart. The vaccines are repeated at 1 year of age and then every 3 years. Bordetella vaccines may be required more often for dogs that are frequently kenneled. Vaccines do not prevent all infections, but they usually decrease the severity of disease.

It is possible for B. bronchiseptica to be transmitted from dogs to immune-compromised people, so preventive measures should be taken when caring for an infected animal.

Prognosis

For most dogs, prognosis is very good. The disease can be life-threatening in young puppies and in dogs compromised by other illnesses. For dogs with pneumonia, prognosis depends on the severity of the pneumonia and any other complicating conditions.

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Canine Influenza

Anisa D. Dunham, AS, RVT, Lynn F. Guptill, DVM, PhD, DACVIM (Small Animal)

BASIC INFORMATION

Description

Canine influenza (CI) is a newer influenza strain that was first reported in 2004 at a Florida greyhound track. The virus first affected pet dogs in 2005. Dogs are the only known susceptible species. This strain (H3N8) is not known to infect humans.

Cause

Canine influenza is caused by an H3N8 strain of the influenza A virus family. It is a mutated strain of an equine influenza virus. Healthy dogs of all ages are susceptible. The influenza is thought to be transmitted by an infected dog sneezing or coughing on another dog, much the same way as influenza is spread among humans. It can also be transmitted via contaminated inanimate objects (fomites) and by people who touch both infected and uninfected dogs.

The incubation period is usually 2-5 days. Infected dogs shed the virus for 7-10 days after clinical signs appear. Since the virus is new, all dogs are considered susceptible to infection, and most dogs exposed to CI become infected. Approximately 80% of infected dogs develop clinical signs. Infected dogs that do not exhibit clinical signs can still shed the virus and spread the infection.

Clinical Signs

The disease may be mild or severe. Most dogs exhibit the mild form of the disease. The most common clinical sign is a cough that lasts 10-30 days despite treatment with antibiotics and cough suppressants. Most dogs have a soft, productive (moist) cough, but others have a dry cough that is similar to kennel cough. Many dogs have a nasal discharge that is purulent (contains pus) and a low-grade fever. Some dogs are more severely affected and may develop pneumonia with a high fever (104-106 ° F) and difficulty breathing.

Diagnostic Tests

Serologic tests that measure antibodies in the blood are commonly used to confirm a CI infection. Antibodies can be detected as early as 7 days after the onset of clinical signs. The first sample is tested within these 7 days, and a second sample is taken 2-3 weeks later. A fourfold increase in antibody levels from the first (acute) sample to the second (convalescent) sample indicates a positive diagnosis of CI. If no early sample was obtained, a positive convalescent sample confirms that the dog was exposed but does not indicate whether an infection was present.

A disadvantage of serology is that it cannot be used to confirm the presence of an acute, active infection. A rapid test is available that can be used to tentatively diagnose an active infection. The test can be run on a nasal swab and is most sensitive during the first 2-3 days of illness. Polymerase chain reaction tests done at outside laboratories are more accurate.

TREATMENT AND FOLLOW-UP

Treatment Options

Treatment is mostly supportive. In the mild form of the disease, nasal discharge may indicate a secondary bacterial infection, so treatment with a broad-spectrum antibiotic may be recommended. Pneumonia associated with the severe form of the disease can also be complicated by a bacterial infection, so broad-spectrum antibiotics are also commonly recommended in those cases. Intravenous fluids may be needed for dehydrated dogs. Cough suppressants are not very helpful in most cases.

Antiviral drugs developed for treatment of influenza in humans, such as Tamiflu, are not used to treat CI, because the appropriate dose and duration of treatment in dogs are unknown. In addition, when used in humans, the drug needs to be started within 48 hours of infection, and canine influenza is rarely diagnosed that early.

Follow-up Care

Dogs showing signs of CI should be isolated as soon as possible, to prevent spread of the disease to other dogs. Do not take these dogs to dog parks, boarding facilities, or other places where other dogs can be exposed to the virus. Recovering animals are also isolated for a couple of weeks to prevent transmission or possible reinfection before the dog has time to build up an adequate immune response to the virus. Wash your hands thoroughly after handling each dog. Thoroughly disinfect areas where the dog is housed with dilute bleach or another suitable disinfectant. All surfaces, equipment, and cages that have come in contact with an infected dog should be thoroughly cleaned and disinfected.

Prognosis

Prognosis is good in most cases. Good nursing care and nutrition are essential for a full recovery. Approximately 5-8% of clinically ill dogs die of this disease.

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Coccidioidomycosis

Anisa D. Dunham, AS, RVT, Lynn F. Guptill, DVM, PhD, DACVIM (Small Animal)

BASIC INFORMATION

Description

Coccidioidomycosis is a systemic (affecting the whole body) fungal infection that typically originates in the lungs and may spread to the lymph glands, bones, and other organs. It has also been called valley fever and San Joaquin Valley fever.

Cause

Coccidioidomycosis is acquired from the environment. The fungus Coccidioides immitis is found most commonly in sandy, alkaline soil. Distribution in the United States is considered to be limited to the southwest desert regions. Coccidioidomycosis also occurs in Mexico, Central America, and some areas of South America. Outbreaks of disease can occur when drought is followed by conditions that allow the release and spread of fungal elements into the air.

Infection occurs via inhalation of the organism from the environment into the lungs or, rarely, from direct inoculation of the organism into the skin. Infection can spread from the lungs to other tissues.

Clinical Signs

Any tissue may be affected. In dogs, sites commonly affected include the lungs, bones, liver, spleen, kidneys, heart, reproductive tract, eyes, and central nervous system (especially brain). In cats, the skin is affected more commonly. Skin lesions may appear as draining tracts and abscesses.

Systemic (widespread) infection probably occurs more commonly in dogs than in cats. Infected cats and dogs may cough. Nonspecific signs, such as decreased appetite, lethargy, and weight loss, are also common. Other signs depend on the tissue affected. Lameness occurs in animals with bone or joint involvement, and seizures or behavioral changes may occur in animals with brain infection.

TREATMENT AND FOLLOW-UP

Treatment Options

The antifungal drugs, itraconazole and fluconazole, are generally effective. These drugs must be given for prolonged periods (months), and the response to treatment should be regularly evaluated by a veterinarian. Severely affected animals often initially require hospitalization and intensive care, sometimes for 1-2 weeks. Treatment is continued for at least 1 month beyond resolution of all clinical signs. Another drug, amphotericin B, may be given to animals with severe disease. It is not used in many cases because it is potentially toxic to the kidneys and must be given by injection. Some forms are less toxic than others.

Follow-up Care

Blood tests are commonly done before and 2 weeks after beginning treatment, and then monthly during treatment to monitor for possible adverse effects. Other monitoring tests (x-rays, eye examinations, others) are also performed at regular intervals to assess response to treatment. Animals are often re-evaluated at 1, 3, and 6 months after treatment is discontinued to look for evidence of relapse. Notify your veterinarian if any signs return after treatment is stopped.

Prognosis

Prognosis is variable, depending on the extent of disease, severity of clinical signs, and initial response to treatment. Prognosis is best in animals with less severe involvement and clinical signs limited to one organ system. Prognosis is guarded (uncertain) to poor in animals with widespread disease, central nervous system infection, or very severe involvement of any organ system.

Strict adherence to treatment protocols is needed for the best response. Treatment of systemic fungal infections requires a commitment to months of medication and follow-up evaluations with your veterinarian. Relapses occur, and follow-up visits (after treatment is completed) are important to help recognize signs of possible relapse.

SPECIAL INSTRUCTIONS:

Coccidiosis, Enteric

Lynn F. Guptill, DVM, PhD, DACVIM (Small Animal)

BASIC INFORMATION

Description

Enteric coccidiosis is a worldwide intestinal disease that causes diarrhea in dogs and cats.

Causes

Several species of microscopic, single-celled, protozoan parasites cause enteric coccidiosis. The most common one to infect dogs and cats is Isospora (Cystoisospora). All enteric coccidia are spread by the fecal-oral route, which means that the organisms are commonly swallowed in water or food contaminated with feces. Some infections may occur by eating tissues from infected animals. Most coccidial organisms are hardy and can persist in the environment.

Clinical Signs

Some infections cause no clinical signs, and the animal may be a silent carrier. In other animals, diarrhea (sometimes bloody), weight loss, and dehydration occur. Diarrhea is more likely in young and immune-suppressed animals.

Diagnostic Tests

Microscopic examination of feces usually reveals the organism in infected animals. Because the organisms may be shed intermittently, examination of more than one fecal sample may be necessary.

TREATMENT AND FOLLOW-UP

Treatment Options

Treatment with sulfadimethoxine is the most common therapy used in dogs and cats. Other sulfa drugs may also be effective. Supportive care, such as fluid therapy for dehydration, may also be necessary.

Follow-up Care

To prevent and control the spread of intestinal coccidiosis, overcrowding of animals must be avoided, and good hygiene should be maintained. Organisms are resistant to most disinfectants but can be killed by steam. Some commercial formulations of ammonia are effective, but they should be used only by trained, experienced people using appropriate personal protective equipment.

Removal of all organic material (dirt, feces) is important in preventing infection. Bathing affected animals during treatment helps remove fecal material containing infectious organisms. In certain kennel and cattery situations, treatment may be recommended for all animals in contact with the infected animal.

Prognosis

Prognosis for infected dogs and cats is generally good, because most respond well to therapy and recover quickly from the disease.

SPECIAL INSTRUCTIONS:

Cryptococcosis

Anisa D. Dunham, AS, RVT, Lynn F. Guptill, DVM, PhD, DACVIM (Small Animal)

BASIC INFORMATION

Description

Cryptococcosis is a systemic (present throughout the body) fungal infection that occurs worldwide. It usually originates in the nasal cavity, in tissues alongside the nose, or in the lungs. It may spread to the skin, eyes, or central nervous system (CNS) (brain and spinal cord). Cats are affected most often.

Causes

The most common causes are Cryptococcus neoformans and Cryptococcus gattii. C. neoformans is often associated with pigeon droppings, bird habitats, or roosts, such as barn lofts, hay mows, statues, and certain buildings.

Pigeons are considered to be an important vector (agent that spreads the disease from one host to another) of C. neoformans. Unlike other systemic fungal infections, it is not confined by any geographic boundaries. The organism may survive in the environment for years. C. neoformans may be found in nasal washes of dogs and cats as an incidental finding; it may or may not progress to clinical disease.

C. gattii is a more geographically restricted organism. It is associated most commonly with the bark and leaf litter of certain eucalyptus trees found in tropical and subtropical environments, and in the Pacific Northwest. It is inactivated by direct exposure to sunlight.

Cryptococcosis is not spread from animal to animal; rather, the infection usually occurs via inhalation of the organisms from the environment. Most of the yeast organisms are too large to be inhaled directly into the lungs, so they often stop in the nasal passages. The small dried forms of the organism can be inhaled directly into the lungs. After the organism is inhaled, it may spread to nearby tissues by direct extension or to other locations via the blood.

Clinical Signs

Lethargy and loss of appetite are common. Fever is uncommon. Upper respiratory signs (sneezing and nasal discharge) are seen in most affected cats. Soft tissue masses or ulcerated lesions may occur in the nasal passage, the bridge of the nose, or in the mouth. Nodules may be seen if the skin or underlying tissues are affected, including the footpad and nail beds.

Behavioral changes, mental dullness, seizures, circling, neck pain, paresis (partial paralysis or impaired movement), and ataxia (lack of coordinated muscle movements) are seen if the CNS is involved. Lameness, blindness, kidney failure, and enlarged lymph nodes may also occur. Most animals with CNS involvement also have the disease in other organs.

Diagnostic Tests

Diagnosis of cryptococcosis can be made on the basis of several laboratory tests:

• A complete blood cell count is often normal, but a mild anemia may be seen. The serum biochemistry profile is usually normal.

• Chest x-rays are usually normal but may show abnormal lung patterns or fluid in the chest.

• The organism can often be identified microscopically in nasal swabs, discharge from skin lesions, or samples taken from soft tissue masses.

• Bronchoscopy (examination of the airways of the lungs using a fiberoptic viewing scope) or rhinoscopy (examination of the nasal passages) may be needed to confirm the diagnosis.

• Fungal culture can also be done.

• Special imaging, such as computed tomography (CT scan) or magnetic resonance imaging (MRI) of the skull or CNS and collection of cerebrospinal fluid (spinal tap) may be recommended.

• A test for cryptococcal antigens (proteins of the organism) in the blood or cerebrospinal fluid is very reliable and is used for diagnosis and to monitor response to treatment.

TREATMENT AND FOLLOW-UP

Treatment Options

Antifungal drugs, such as fluconazole, itraconazole, or amphotericin B, are effective treatments. Fluconazole may be the preferred treatment for CNS disease. Amphotericin B is very effective; however, it is expensive, is usually administered intravenously, and can be toxic to the kidneys. Large lesions may be reduced in size with surgery before medical therapy is started. Treatment is needed for many months and is continued for 1 month after resolution of all clinical signs.

Follow-up Care

Physical and eye examinations are usually performed monthly and include a serum biochemistry profile to check for liver abnormalities that may be caused by the medications. It may be useful to repeat the antigen test to monitor treatment response. Animals are commonly re-examined 3-6 months after treatment is discontinued to check for relapses.

Prognosis

Prognosis depends on the extent of disease. Animals with primarily skin involvement have the best prognosis. Cats with feline leukemia virus or feline immunodeficiency virus infection may require longer therapy. Prognosis is guarded (uncertain) for animals with CNS involvement or severe systemic illness.

SPECIAL INSTRUCTIONS:

Cryptosporidiosis

Lynn F. Guptill, DVM, PhD, DACVIM (Small Animal)

BASIC INFORMATION

Description

Cryptosporidiosis is an intestinal disease that causes diarrhea in many species, including dogs, cats, farm animals, and humans.

Causes

Cryptosporidium species are microscopic, single-celled, protozoan parasites that are found all over the world. Several distinct species exist, and those that infect dogs and cats do not seem to commonly infect humans.

Cryptosporidiosis is spread by the fecal-oral route, which means the organism is often swallowed in food or water contaminated by feces. The organism is very hardy and persists in the environment for prolonged periods.

Clinical Signs

Many infections in dogs and cats cause no clinical signs or only a mild, self-limited (short-lived) diarrhea. Diarrhea, when it occurs, is characterized by a high volume of semiformed to liquid feces and normal frequency of defecation. Weight loss may be seen in animals with persistent diarrhea. Diarrhea is more likely in young and immune-suppressed animals.

Diagnostic Tests

Diagnosis can be made using a number of different methods, such as the following:

• Microscopic examination of fresh feces may reveal the organism. Routine methods of fecal examination are not sensitive enough to detect Cryptosporidium. and special techniques are often needed to identify the organisms. It is often recommended that fecal samples be sent to an outside laboratory that is capable of making the diagnosis.

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Tags: Small Animal Practice Client Handouts

Sep 11, 2016 | Posted by admin in SMALL ANIMAL | Comments Off

Fastest Veterinary Medicine Insight Engine

15: Infectious Diseases

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