Toxoplasma

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Toxoplasma gondii

Toxoplasma gondii is the contributing agent of a toxoplasmosis that occurs worldwide with high prevalence.

The development cycle of Toxoplasma gondii involves three phases:

Intestinal phase with production of sexual forms (gamogony) takes place in enterocytes of definitive hosts. Only domestic cats, and several other felid species of little epidemiological significance, can function as definitive hosts. Only extra-intestinal development is seen in intermediate hosts (pigs, sheep, and many other animal species) as well as in hosts (humans). Following the primary infection of a cat with Toxoplasma cysts in raw meat, asexual reproductive forms develop in the small intestine epithelium at first, with sexually differentiated stages and oocysts following later. The oocysts are shed in feces after prepatent period of three to nine days. When cats are infected with sporulated oocysts, the prepatent period is extended to 20-35 days. Oocyst sheeding lasts from only a few days to a maximum of three weeks, but can be highly intense.

External phase: Oocysts excreted in cat feces sporulate at room temperature within two to four days, getting them infected. Kept moist, they remain infected for up to five years and are not killed by standard disinfectant agents.

Extraintestinal phase: This phase follows a peroral ingestion with oocysts or cysts and is observed in intermediate hosts (dogs, sheep, pigs, other vertebrates, birds).
Cases are differentiated as to time of acquisition, i.e., postnatal and prenatal infections (see tab.)

Disease	Symptoms	Mechanism of Infection
Postnatal toxoplasma infection	In general unspecific symptoms like swelling of the lymph nodes, feeling of sickness, limb pain and fever. rarely hepatitis, myocarditis, pneumonia, encephalitis	Oral ingestion of oocysts or cysts with food
Reactivation toxoplasmosis	In immunosuppressed persons: encephalitis, pneumonia, myocarditis, meningoencephalitis, eye damage, generalized lymphadenitis
Prenatal toxoplasmosis	Infection in the first trimester of pregnancy: abortion Infection in the second or third trimester of pregnancy: abortion (10%), premature birth, damages of the fetus: pneumonia, myocarditis, nephritis, hepatitis, hydrocephalus, microcephaly, intracranic calcification, chronic chorioretinitis Children of women, who are infected just before birth, appear to be clinically normal at birth, but signs of brain and eye damage, as well as other symptoms, may manifest later in infancy and early childhood. Oral ingestion of oocysts or cysts with food.	Prenatal infection of the fetus with toxoplasma occurs only in pregnant women with primary infection

Infections may be diagnosed by:

Microscopy: Determination of acute infection by coloured Giemsa or marked antibodies
Serology: Determination of specific antibodies based on the ELISA technique

NovaLisa? Toxoplasma gondii IgG/IgM µ-capture ELISA:

The NovaLisa? Toxoplasma gondii IgG/IgM µ-capture ELISA is intended for the quantitative (IgG) and qualitative (IgM) determination of IgG-/IgM-class antibodies against Toxoplasma gondii in human serum or plasma (citrate).

Antigens:

IgG: Toxoplasma gondii (Lysate) antigens
IgM: P30

Specific performance characteristics:

	Intraassay			Interasay			Sensitivity%	Specificity%
	n	Mean	CV%	n	Mean	CV%
IgG	6	0.978	5.7	4	0.752	7.1	100	96.8
	6	1.647	5.3	4	1.26	10.1
	6	2.496	6.2	4	1.98	6.3
IgM	20	0.429	5.6	12	13.25	8.8	95.5	98.2
IgM	20	1.725	3.2	11	48.06	8.	95.5	98.2

NovaLisa? Toxoplasma gondii IgG Avidity Test

The avidity determination is a diagnostic method which is used to differentiate a recent (acute) and a more distant (past) infection with Toxoplasma gondii in patient sera. Avidity is the binding force of the antibody (serum specimen) with the corresponding antigen.

Low avid IgG antibodies in the early stage of infection can be differentiated from high avid antibodies associated with a past infection.

The determination of IgG antibody avidity is an additional analysis to the classic serology in regard to the status of a Toxoplasma gondii infection.

The NovaLisa? Toxoplasma gondii IgG Avidity Test is an additional reagent-kit that has to be used in combination with NovaLisa? Toxoplasma gondii IgG ELISA.

Performance Characteristics:

The NovaLisa? Toxoplasma gondii IgG Avidity Test has been evaluated for use in Toxoplasmosis with sera of acute and past infections. A total number of 69 defined patient samples were tested. These sera were supplied by the Institute of Parasitology, University Bonn.

		Defined Samples
		Acute Infection	Past Infection	Total
Novalisa Toxoplasma gondii IgG Avidity Test	Acute Infection	22	2	24
	Past Infection	3	42	45
	Total	25	44	69