Changes

immunofluorescent antibody testing, Sabin-Feldmann dye test, and agglutination tests. Although these tests are theoretically able to detect all classes of immunoglobulin against ''Toxoplasma gondii'' in many species, it seems that feline serum positive for IgM only often reads as a false negative^{5, 6} and so careful interpretation is necessary, particularly since the IgM antibody class appears to correlate more closely to clinical disease than IgG⁷. IgG antibody persists at high levels for at least six years after infection, and so a single IgG measurement is not particularly useful for clinical diagnosis. A rising IgG titre may be more suggestive of active toxoplasmosis: however, IgG is not produced until 2-3 weeks post-infection which may be too late to be useful in acute cases, and many animals with chronic toxoplasmosis will not be assayed until IgG is already at its maximal titre.

immunofluorescent antibody testing, Sabin-Feldmann dye test, and agglutination tests. Although these tests are theoretically able to detect all classes of immunoglobulin against ''Toxoplasma gondii'' in many species, it seems that feline serum positive for IgM only often reads as a false negative^{5, 6} and so careful interpretation is necessary, particularly since the IgM antibody class appears to correlate more closely to clinical disease than IgG⁷. IgG antibody persists at high levels for at least six years after infection, and so a single IgG measurement is not particularly useful for clinical diagnosis. A rising IgG titre may be more suggestive of active toxoplasmosis: however, IgG is not produced until 2-3 weeks post-infection which may be too late to be useful in acute cases, and many animals with chronic toxoplasmosis will not be assayed until IgG is already at its maximal titre.

A more practically useful form of serology is examination IgM in aqueous humour or cerebrospinal fluid. Demonstration of an IgM titre of above 1:64 or a

A more practically useful form of serology is examination of IgM in aqueous humour or cerebrospinal fluid. IgM, in contrast to IgG and IgA, has only been detected in the aqueous humour and CSF of cats with clinical disease ^{5, 8}. An IgM titre of above  Most cats with

fourfold or greater increase in IgG titre, or the documentation

of local antibody production or DNA in aqueous

eyes or CNS can be used to document clinical toxoplasmosis.

While IgG and IgA class antibodies are produced

experimental inoculation, IgM has only been detected in

the aqueous humour or CSF of cats with clinical disease

(Lappin 1996, Dubey and Lappin 1998). Most cats with

local production of T gondii-specific antibodies in aqueous

local production of T gondii-specific antibodies in aqueous

humour have responded to the administration of anti-

humour have responded to the administration of anti-