The pathogen of toxoplasmosis is the sporozoon Toxoplasma gondii. The only final hosts are the domestic cat and other felidae, in which the parasite lives in the intestine and forms oocysts in the sexual developmental stage. In general, infection occurs perorally by ingestion of water or food contaminated with oocysts (through the faeces of infected cats) or from meat products (the raw flesh of infected animals contains cysts with viable trophozoites).
In adult cats the infection usually proceeds asymptomatically. But connatally infected kittens often develop severe clinical symptoms, from which they die. Proliferation of the parasite in the intestine of the host can lead to diarrhoea. The infection of extraintestinal tissue frequently affects the lungs, liver, CNS, pancreas or eyes. In this case, the cats present with lethargy, anorexia, fever, icterus, dyspnoea, ataxia or uveitis.
In addition to its clincial relevance for cats, feline toxoplasmosis is an important zoonosis. After primary infection or reactivation of a latent infection, infected cats excrete oocysts with their faeces for one to three weeks. The parasites become infectious after two to four days in the environment and can perorally infect humans or warmblooded animals. Immunosuppressed individuals, in particular, may develop severe diseases, e.g. encephalitis in AIDS patients. In pregnant women and warm-blooded animals toxoplasma can be transmitted via the placenta to the foetus. Intrauterine infection can result in abortion, malformation and other damage to the newborn, depending on the time of infection, the dose of the infection and the immune status of mother and foetus.
Toxoplasma oocysts are rarely detected in faeces since their period of excretion is short. However, the PCR methods that have been established during recent years are much more sensitive than flotation and microscopy. The detection of specific antibodies in serum or plasma using IIFT, ELISA or agglutination assay is an important diagnostic tool. A positive result for Toxoplasma-specific IgG antibodies indicates an infection. Since toxoplasma cysts, and therefore IgG antibodies, persist lifelong, an acute infection can only be diagnosed by the detection of IgM antibodies, by a fourfold increase in the IgG titer in a follow-up sample taken after two to four weeks or by the determination of low-avidity IgG antibodies. IgM antibodies are generally detectable two to sixteen weeks after infection. Specific IgG, however, is exhibited three to four weeks after infection. Up to 20 % of infected cats do not develop detectable IgM antibody titers, and cases of reactivated toxoplasmosis that did not exhibit specific IgM have been described. Reliable differentiation between acute and past infection can be achieved by determination of low-avidity IgG antibodies, which indicate an acute Toxoplasma gondii infection, and of high-avidity antibodies, which point to a past infection. If the avidity test is negative despite the presence of clear symptoms of Toxoplasma gondii infection, a second sample should be tested for low-avidity antibodies some days later.
|Method||Substrate||Diagnostic application||Order number|
|IIFT1||Toxoplasma gondii trophozoites||IgG/IgM IIFT; first test for the diagnosis of toxoplasmosis in cats authorised in Germany pursuant to the TierSG; high sensitivity and specificity; qualitative and semi-quantitative determination of anti-Toxoplasma antibodies||FI 2410-1005 GF|
FI 2410-1010 GF
FI 2410-1005 MF
FI 2410-1010 MF
|ELISA||Purified and detergent-extracted Toxoplasma gondii organisms||IgG ELISA; high sensitivity and specificity due to the use of a specific lysate||EI 2410-9601 GF|
|ELISA Avidity||Purified and detergent-extracted Toxoplasma gondii organisms||ELISA for Determination of the avidity of Toxoplasma-specific IgG antibodies; alternative principle for the diagnosis of acute infections (no influencing persisting or absent IgM antibodies)||EI 2410-9601-1 GF2|
1 Authorised pursuant to § 17 c TierSG (German Epizootic Diseases Act), Reg. no: FLI-B 567.
2 The test is suited both for determination of the avidity of specific IgG antibodies and for standard IgG determination.