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| | ===Laboratory Tests=== | | ===Laboratory Tests=== |
| | | | |
| − | DIAGNOSIS OF CLINICAL FELINE
| + | Demonstration of ''Toxoplasma gondii'' in the tissues with associated inflammation is required for the definitive diagnosis of clinical toxoplasmosis. This is usually achieved post-mortem, but ante-mortem testing of tissues and effusions for bradyzoites or tachyzoites is possible. Many normal animals possess ''Toxoplasma gondii''-specifice antibodies in the serum , aqueous humour and CSF, and so serology alone is not appropriate for diagnosis of toxoplasmosis. However, a combination of various diagnostic procedures can be used to build a presumptive diagnosis. Cytology is of some use in the diagnosis of toxoplasmosis. Tachyzoites may be seen in the blood, cerebrospinal fluid, peritoneal and pleural effusions or transtracheal washes from clinically ill animals<sup>1</sup>. CSF analysis may show elevated protein levels. In addition to using cytology to demonstrate T gondii |
| − | TOXOPLASMOSIS
| + | tachyzoites, PCR, tissue culture and animal inoculation |
| − | Definitive diagnosis of clinical feline toxoplasmosis
| + | techniques can be used to detect the organism in whole |
| − | requires demonstration of the organism in the tissues in
| + | blood, aqueous humour or CSF. Tissue biopsy sections |
| − | association with inflammation. This is usually achieved
| + | can be assessed for the presence of T gondii by haematoxylin |
| − | at necropsy in cats with overwhelming tachyzoite replication.
| + | and eosin (H&E) staining, immunohistochemical |
| − | Occasionally, a definitive diagnosis of clinical
| + | staining, PCR, cell culture or animal inoculation. |
| − | feline toxoplasmosis is made antemortem by demonstrating
| + | Immunohistochemical staining procedures are superior |
| − | bradyzoites or tachyzoites in tissues or effusions.
| + | to H&E staining because they are specific for T gondii |
| − | Since T gondii-specific antibodies can be detected in
| + | (see figure on page 580). It may be difficult to document |
| − | the serum, CSF and aqueous humour of normal animals,
| + | the organism in the tissues of some clinically ill cats |
| − | as well as those with clinical signs of disease, it is not
| + | because of the small sections of tissue evaluated |
| − | possible to make an antemortem diagnosis of clinical
| + | histopathologically and because the pathogenesis of disease |
| − | toxoplasmosis based on these tests alone. However, a
| + | in some may be immune-mediated. This appears to |
| − | presumptive antemortem diagnosis of clinical feline
| + | be particularly true for the ophthalmic form of the disease |
| − | toxoplasmosis may be based on the following combination
| + | in cats. |
| − | of findings: | + | |
| | + | * Clinical signs of disease referable to toxoplasmosis; |
| | + | Routine haematology, biochemistry and urinalysis show no changes specific for toxoplasmosis. However, during ''T. gondii'' infection, several features may be seen and could be suggestive. For haematology, these might include: non-regenerative anaemia, neutrophilic leucocytosis, lymphocytosis, monocytosis, neutropenia or eosinophilia. Biochemical profiles could show increased creatine kinase, ALT, SAP, bilirubin and total protein, and proteinuria and bilirubinuria may be revealed by urinalysis<sup>1</sup>. |
| | + | |
| | * Demonstration of antibodies in serum, aqueous | | * Demonstration of antibodies in serum, aqueous |
| | humour or CSF (documents exposure to T gondii); | | humour or CSF (documents exposure to T gondii); |
| − | * Demonstration of an IgM titre of above 1:64 or a
| |
| − | fourfold or greater increase in IgG titre, or the documentation
| |
| − | of local antibody production or DNA in aqueous
| |
| − | humour or CSF (suggests recent or active infection);
| |
| − | * Clinical signs of disease referable to toxoplasmosis;
| |
| − | * Exclusion of other common aetiologies;
| |
| − | * Positive response to appropriate treatment (see
| |
| − | below).
| |
| − |
| |
| − |
| |
| − | Routine haematology, biochemistry and urinalysis show no changes specific for toxoplasmosis. However, during ''T. gondii'' infection, several features may be seen and could be suggestive. For haematology, these might include: non-regenerative anaemia, neutrophilic leucocytosis, lymphocytosis, monocytosis, neutropenia or eosinophilia. Biochemical profiles could show increased creatine kinase, ALT, SAP, bilirubin and total protein, and proteinuria and bilirubinuria may be revealed by urinalysis.<sup>1</sup>
| |
| − |
| |
| − | Cytology is of some use in the diagnosis of toxoplasmosis. Tachyzoites may be seen in the blood, cerebrospinal fluid, peritoneal and pleural effusions or transtracheal washes from clinically ill animals<sup>1</sup>. CSF analysis may show elevated protein levels.
| |
| − |
| |
| − |
| |
| − | T gondii oocysts are 10 x 12 ,um in size and can be
| |
| − | demonstrated microscopically in feline faeces following
| |
| − | 0 2 4 6 8 12 16 20 26 34
| |
| − | Weeks after inoculation
| |
| − | Temporal appearance of
| |
| − | T gondii-specific IgM, IgG
| |
| − | and IgA antibodies in the
| |
| − | serum of experimentally
| |
| − | flotation using solutions with a specific gravity of 1-18. inoculated cats
| |
| − | Oocysts of the non-pathogenic coccidians Hammondia
| |
| − | hammondi and Besnoitia darlingi cannot be distinguished
| |
| − | microscopically from those of T gondii; definitive diagnosis
| |
| − | relies on laboratory animal inoculation. Most cats
| |
| − | with clinical toxoplasmosis have completed the oocyst
| |
| − | shedding period and so the diagnostic utility of faecal
| |
| − | examination is limited. However, due to the potential
| |
| − | zoonotic risk, a faecal examination should be performed
| |
| − | for any cat with clinical signs referable to toxoplasmosis.
| |
| − |
| |
| − | SEROLOGY
| |
| | T gondii-specific antibodies, antigens and immune | | T gondii-specific antibodies, antigens and immune |
| | complexes have been detected in the serum of cats | | complexes have been detected in the serum of cats |
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| | recognition patterns between the queen and kittens. | | recognition patterns between the queen and kittens. |
| | | | |
| − | AQUEOUS HUMOUR AND CSF ANTIBODY
| + | * Demonstration of an IgM titre of above 1:64 or a |
| − | AND DNA MEASUREMENT
| + | fourfold or greater increase in IgG titre, or the documentation |
| | + | of local antibody production or DNA in aqueous |
| | + | humour or CSF (suggests recent or active infection); |
| | Detection of T gondii-specific antibodies produced by the | | Detection of T gondii-specific antibodies produced by the |
| | eyes or CNS can be used to document clinical toxoplasmosis. | | eyes or CNS can be used to document clinical toxoplasmosis. |
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| | (Burney and others 1998). | | (Burney and others 1998). |
| | | | |
| − | DEMONSTRATION OF T GONDII IN TISSUES
| + | *Faecal examination |
| − | In addition to using cytology to demonstrate T gondii
| + | T gondii oocysts are 10 x 12 ,um in size and can be |
| − | tachyzoites, PCR, tissue culture and animal inoculation
| + | demonstrated microscopically in feline faeces following |
| − | techniques can be used to detect the organism in whole
| + | 0 2 4 6 8 12 16 20 26 34 |
| − | blood, aqueous humour or CSF. Tissue biopsy sections
| + | Weeks after inoculation |
| − | can be assessed for the presence of T gondii by haematoxylin
| + | Temporal appearance of |
| − | and eosin (H&E) staining, immunohistochemical | + | T gondii-specific IgM, IgG |
| − | staining, PCR, cell culture or animal inoculation.
| + | and IgA antibodies in the |
| − | Immunohistochemical staining procedures are superior
| + | serum of experimentally |
| − | to H&E staining because they are specific for T gondii
| + | flotation using solutions with a specific gravity of 1-18. inoculated cats |
| − | (see figure on page 580). It may be difficult to document
| + | Oocysts of the non-pathogenic coccidians Hammondia |
| − | the organism in the tissues of some clinically ill cats
| + | hammondi and Besnoitia darlingi cannot be distinguished |
| − | because of the small sections of tissue evaluated
| + | microscopically from those of T gondii; definitive diagnosis |
| − | histopathologically and because the pathogenesis of disease
| + | relies on laboratory animal inoculation. Most cats |
| − | in some may be immune-mediated. This appears to
| + | with clinical toxoplasmosis have completed the oocyst |
| − | be particularly true for the ophthalmic form of the disease | + | shedding period and so the diagnostic utility of faecal |
| − | in cats.
| + | examination is limited. However, due to the potential |
| | + | zoonotic risk, a faecal examination should be performed |
| | + | for any cat with clinical signs referable to toxoplasmosis. |
| | | | |
| − | | + | * Positive response to appropriate treatment (see |
| − | Diagnosis is made by biologic, serologic, or histologic methods, or by some combination of the above. Clinical signs of toxoplasmosis are nonspecific and are not sufficiently characteristic for a definite diagnosis. Antemortem diagnosis may be accomplished by indirect hemagglutination assay, indirect fluorescent antibody assay, latex agglutination test, or ELISA. IgM antibodies appear sooner after infection than IgG antibodies but generally do not persist past 3 mo after infection. Increased IgM titers (>1:256) are consistent with recent infection. In contrast, IgG antibodies appear by the fourth week after infection and may remain increased for years during subclinical infection. To be useful, IgG titers must be measured in paired sera from the acute and convalescent stages (3-4 wk apart) and must show at least a 4-fold increase in titer. Additionally, CSF and aqueous humor may be analyzed for the presence of tachyzoites or anti- T gondii antibodies. Postmortem, tachyzoites may be seen in tissue impression smears. Additionally, microscopic examination of tissue sections may reveal the presence of tachyzoites or bradyzoites. T gondii is morphologically similar to other protozoan parasites and must be differentiated from Sarcocystis spp (in cattle), S neurona (in horses), and Neospora caninum (in dogs).
| + | below). |
| | | | |
| | ===Diagnostic Imaging=== | | ===Diagnostic Imaging=== |