Diseases conditions of cats

Toxoplasmosis in Cats

Toxoplasmosis in Cats

Overview of Toxoplasmosis in Cats

Toxoplasmosis is an infectious disease caused by a single-celled parasite called Toxoplasma gondii. Toxoplasmosis, commonly shorted and referred to as “Toxo”, can occur in both cats and dogs. Cats are generally asymptomatic carriers of this infectious disease but can be affected under certain circumstances. This disease is zoonotic, which means it is transmissible to humans, and pregnant women especially must be careful when handling their cat's litter boxes.

Below is an overview of Toxoplasmosis in Cats followed by in-depth details about the diagnosis, treatment and follow-up care for this condition.

Kittens are more susceptible to toxoplasmosis infection than adult cats and have more severe signs of disease when infected. Also, cats that are outdoors and hunt wildlife are at higher risk than cats confined to an indoor environment. Animals that are fed raw or incompletely cooked meat are at higher risk, as well as animals that are immunosuppressed.

Cats usually contract the disease by the following means:

  • Transplacental transmission. The organism is ingested by a pregnant animal, multiplies in the placenta and then infects the developing fetus.
  • Ingestion of the organism when they feed on the tissues of infected birds and rodents.
  • Ingestion of food or water contaminated with infected feces.
  • Transfusion of infected blood (rare).

    What to Watch For

    The signs of toxoplasmosis in pets are nonspecific, and most cats show no signs of infection. These signs may include fever, loss of appetite and depression. Further signs may occur, but that depends on where the infection occurs; toxoplasmosis can affect any organ system but primarily affects the lungs, the central nervous system (brain) and the eyes.

  • Central nervous system signs may include depression, a head tilt, partial or total blindness, seizures and death.
  • Respiratory signs may include fever, cough, and increased respiratory rate and effort.
  • Uveitis (inflammation of the interior of the eye) may cause excessive blinking (blepharospasm), squinting, and sensitivity to light (photophobia).
  • Other signs that may be observed are ascites (accumulation of fluid in the abdomen), jaundice, hepatomegaly (liver enlargement), muscle pain, loss of appetite, and weight loss.
  • Diagnosis of Toxoplasmosis in Cats

    The best method to diagnose toxoplasmosis is measurement of antibodies to the organism. Your veterinarian may also do other diagnostic tests, such as:

  • Complete blood count (CBC)
  • Biochemistry profile
  • Fecal examination
  • Ocular (eye) examination
  • IgG and IgM antibody testing (titers)
  • ELISA test (antigen test)
  • Chest x-rays
  • Cerebrospinal fluid analysis (CSF analysis)
  • Analysis of pleural (chest) or peritoneal (abdominal) fluid
  • Transtracheal aspirate
  • Treatment of Toxoplasmosis in Cats

  • Antibiotics such as clindamycin, trimethoprim-sulfonamide, or sulfonamides combined with pyrimethamine.
  • Anticonvulsants for seizures.
  • Intravenous (IV) fluids for debilitated animals.
  • Home Care

    At home care consists of administering any medications prescribed by your veterinarian.

    Preventative Care

    Pet cats should be fed only dry, canned or cooked food. Cats should not be fed uncooked meat, entrails or bones as these tissues may contain toxoplasma cysts. Take measures to prevent cats from successfully hunting wildlife (keep indoors, attach bells to collars).

    Secure trash containers to prevent garbage scavenging by cats. Remove carcasses of rodents or birds before cats can consume them.

    Preventing human exposure to toxoplasmotitis from cats

    Pregnant women and immunocompromised individuals should not clean cat litter boxes and they should avoid contact with cat feces and soil where cats may have defecated. If another family member cannot clean the cat litter box, the box should be emptied daily, and cleaned with scalding water once weekly.

    In-depth Information on Toxoplasmosis in Cats

    Related Symptoms or Diseases

  • Feline infectious peritonitis (FIP) is a progressive and ultimately fatal disease caused by a coronavirus that affects cats only. The symptoms of FIP may appear almost identical to those of toxoplasmosis and must be differentiated by laboratory tests and titers for each of the diseases.
  • Feline leukemia virus (FeLV) causes non-specific signs of illness as well as anemia (low red blood cell count). This disease can be easily differentiated from toxoplasmosis on the basis of a blood test for feline leukemia.
  • Feline immunodeficiency virus (FIV) causes non-specific signs of illness by compromising a cat's immune system thereby making them susceptible to secondary infections. FIV can be easily distinguished from toxoplasmosis with a blood test for FIV.
  • Hemobartonellosis is a disease caused by a blood parasite that affects both dogs and cats. Infection with hemobartonella results in anemia, fever and an enlarged spleen. Haemobartonellosis is diagnosed on the basis of a blood smear where the blood parasites can be seen within the red blood cells.
  • Immune-mediated diseases such as those that attack red blood cells, joints and muscle can cause fevers, joint and muscle pain, and anemia, which may appear similar to those symptoms of toxoplasmosis. Immune mediated diseases are often diagnosed with blood tests, joint taps or muscle biopsies, depending on the nature of the pet's symptoms.
  • Cancer causes signs of illness that can mimic those of any disease including toxoplasmosis.
  • Systemic fungal infection, such as blastomycosis, histoplasmosis and cryptococcis, can produce signs of disease similar to those of toxoplasmosis, such as fever, lethargy, loss of appetite and difficulty breathing. Fungal infections are more common in certain parts of the United States, and unless you live in a certain area or your pet has traveled to those areas, your veterinarian may not pursue a fungal infection as a differential diagnosis.
  • Diagnosis In-depth

    The diagnosis of toxoplasmosis can be very difficult. In addition to obtaining a complete medical history (including your pet's travel history) and performing a complete physical examination, your veterinarian will likely perform many of the following diagnostic tests.

  • A complete blood count (CBC) is done to determine if your pet is anemic (low red blood cell count) and to assess the white blood cell count. Pets with toxoplasmosis are commonly anemic, but the white blood cell count often remains unchanged.
  • A serum chemistry profile allows your veterinarian to evaluate the internal organs such as the liver, pancreas and kidneys. Because toxoplasmosis often causes elevations in liver enzymes and total bilirubin (causing jaundice), this test is essential to evaluate involvement of the liver. Additionally, elevations in blood sugar, total protein levels and globulin levels may be present.
  • Examination of a fecal (stool) sample may be performed to look for toxoplasma oocysts (one of the life cycle stages of toxoplasma). Because infected cats shed oocysts intermittently, a fecal sample may be negative despite serious infection. Thus, a negative fecal sample does not rule out toxoplasmosis.
  • An ocular (eye) examination should be part of the physical examination performed by your veterinarian to look for evidence of uveitis (inflammation of the interior of the eye), hemorrhage or lesions in the back of the eye (fundic lesions) that are commonly present with toxoplasmosis. The finding of these lesions does not definitively diagnose toxoplasmosis, but it does raise the index of suspicion for the disease and should prompt your veterinarian to submit additional tests to look for toxoplasmosis.
  • Immunoglobulin G (IgG) and Immunoglobulin M (IgM) antibody testing with the Immunoflourescence Assay (IFA) is the most common method of diagnosing toxoplasmosis. IgG-IFA antibodies do not develop until 2 weeks post-infection and may remain high for several years. Therefore, high IgG-IFA antibody titers do not definitively diagnose an active infection. Instead, the diagnosis of active infection using IgG-IFA antibody titers requires that the titers increase fourfold over a 2-3 week period. Your veterinarian would need to draw two blood samples 3 weeks apart to demonstrate the rise in titers. An IgM-IFA antibody titer can be measured and can detect active infection. A positive IgM-IFA titer along with a negative IgG-IFA titer is diagnostic of an active infection. The reverse (positive IgG-IFA with negative IgM-IFA titers) would indicate a chronic infection.
  • An ELISA test may also be used to detect IgM antibodies. A high IgM-ELISA titer (>1:256) with a negative or low IgG-IFA titer indicates an active infection. Interpretation of titers is difficult and this information should be used in conjunction with other laboratory tests and the patient's clinical condition to render a diagnosis.

    Other tests that may aid in the diagnosis of toxoplasmosis include:

  • Thoracic (chest) x-rays are helpful to rule out other causes of respiratory compromise such as pneumonia, cancer, and fungal infection.
  • Analysis of cerebrospinal fluid obtained by a cerebrospinal fluid tap is used to help differentiate toxoplasmosis from other diseases causing central nervous system problems. The fluid is analyzed for red and white blood cells (none should be present) and antibody titers may be measured in the fluid as well. Test results must be assessed in conjunction with other findings in the patient as CSF analysis alone is not sufficient to provide a diagnosis.
  • On rare occasions, tachyzoites (one of the life cycle stages of toxoplasma) may be found in pleural (chest) or abdominal (belly) fluid that is obtained from a pet infected with toxoplasmosis. A sample for analysis is obtained by removing fluid from the pet's chest or abdomen by sterile aspiration. Because all pets with toxoplasmosis do not experience the escape of fluid into the chest or abdomen (effusions), this test is limited to those that do.
  • Additionally, tachyzoites may be found in fluid obtained by aspirating a sample pf bronchial exudate (transtracheal aspirate) in infected pets with pulmonary (lung) lesions. A transtracheal aspirate is performed with the pet under sedation. A sterile endotracheal tube is placed in the pet's trachea (windpipe), sterile saline is squirted down the tube via a long sterile catheter, and the pet is induced to cough by gentle percussion of the chest wall. Fluid is then aspirated into a sterile syringe and examined under a microscope.
  • Treatment In-depth

    Because the results of some diagnostic tests take several days to return, your veterinarian may need to initiate supportive therapy before a definitive diagnosis is made.

  • Antibiotics such as clindamycin, trimethoprim-sulfa, sulfonamides and pyrimethamine are administered to pets with toxoplasmosis. Clindamycin is the antibiotic of choice and is generally administered twice a day for 4 weeks. Trimethoprim-sulfa can be used alone or in combination with pyrimethamine. Both drugs are given twice daily for 4 weeks. Trimethoprim-Sulfa and pyrimethamine in combination may cause bone marrow suppression in cats. Bone marrow suppression can be corrected by supplementing the pet's diet with folinic acid or yeast.
  • Anticonvulsant medications such as diazepam (Valium®), phenobarbital or pentobarbital may be used to control seizures.
  • Intravenous fluids and/or intravenous nutrition may be necessary for pets that are dehydrated or severely debilitated due to infection with toxoplasmosis. Nutritional support is particularly important while a patient is fighting an infection. If the pet is not vomiting but refuses to eat, your veterinarian may elect to place a naso-esophageal tube to permit feeding of a liquid diet. If the pet is vomiting, nutrition can be provided via a sterile intravenous catheter. Your pet may be referred to a 24- hour care practice or to a specialist for nutritional support.
  • Follow-up Care for Cats with Toxoplasmosis

    At home, administer any medications prescribed by your veterinarian. Some antibiotics may cause intestinal upset resulting in vomiting and diarrhea. If vomiting and diarrhea occur during the administration of an antibiotic, contact your veterinarian as soon as possible.

    If your pet is receiving trimethoprim-sulfa and pyrimethamine, your veterinarian will ask you to recheck your pet's CBC periodically during treatment to detect whether bone marrow suppression is present or not.

    Encourage your pet to eat and drink. Pets that are unwilling to eat or drink should be re-examined immediately. Your veterinarian will schedule a recheck examination and will submit blood to recheck antibody titers after the course of antibiotic administration is completed.

    Preventing Cat Exposure

    Pet cats should be fed only dry, canned or cooked food. Cats should not be fed uncooked meat, entrails or bones as these tissues may contain toxoplasma cysts. Take measures to prevent cats from hunting wildlife. Keep them indoors or attach bells to their collars. Secure trash containers to prevent garbage scavenging by cats, and remove the carcasses of rodents or birds before cats can consume them.

    Preventing Human Exposure From Cats

    Pregnant women and immunocompromised individuals should not clean cat litter boxes and should avoid contact with cat feces and soil where cats may have defecated. If another family member cannot clean the cat litter box, the box should be emptied daily, and cleaned with scalding water once weekly.