Toxoplasmosis: a history of clinical observations

A method that increases the sensitivity and specificity of the direct agglutination (AG) test for diagnosis of Toxoplasma gondii infection is described. Qualitative results in the Sabin-Feldman dye test (DT) and AG test were in excellent agreement (98%). Differences in titers between these two tests often related to the length of time the individual was infected. The AG test titer was most often lower than the DT titer during acute (recent) infection; the AG test titer was most often higher than the DT titer in older or chronic infection. If the AG test antigen described here can be made available, the AG test would be ideal for use as a screening test and would provide a simple and inexpensive means for the surveillance of seronegative women during pregnancy and for detection of seroconversions.

Direct agglutination test for diagnosis of Toxoplasma infection: method for increasing sensitivity and specificity.

In this paper the history of Toxoplasma gondii and toxoplasmosis is reviewed. This protozoan parasite was first discovered in 1908 and named a year later. Its medical importance remained unknown until 1939 when T. gondii was identified in tissues of a congenitally infected infant, and veterinary importance became known when it was found to cause abortion storms in sheep in 1957. The discovery of a T. gondii specific antibody test, Sabin-Feldman dye test in 1948 led to the recognition that T. gondii is a common parasite of warm-blooded hosts with a worldwide distribution. Its life cycle was not discovered until 1970 when it was found that felids are its definitive host and an environmentally resistant stage (oocyst) is excreted in feces of infected cats. The recent discovery of its common infection in certain marine wildlife (sea otters) indicates contamination of our seas with T. gondii oocysts washed from land. Hygeine remains the best preventive measure because currently there is no vaccine to prevent toxoplasmosis in humans.

The history of Toxoplasma gondii--the first 100 years.

An immunoglobulin M (IgM)-immunosorbent agglutination assay (IgM-IS-AGA) was negative in all sera from individuals negative in the Sabin-Feldman dye test, in sera from individuals with chronic Toxoplasma infection, and in cord blood samples from uninfected infants. In contrast, all sera that were obtained from individuals with a recent history of acute Toxoplasma infection and from infants with congenital Toxoplasma infection and that were positive in both the dye test and the IgM-indirect fluorescent-antibody (IgM-IFA) test were positive in IgM-ISAGA. A total of 21 (67.7%) of 31 sera that were negative in the IgM-IFA test, despite being obtained from individuals with recently acquired Toxoplasma infection, and 8 (72.7%) of 11 sera that were negative in the IgM-IFA test and obtained from infants with congenital Toxoplasma infection were positive in IgM-ISAGA. The presence of rheumatoid factor, antinuclear antibodies, or both did not cause false-positive results in the IgM-ISAGA but did so in the IgM-IFA test. Thus, IgM-ISAGA in both more sensitive and more specific than the IgM-IFA test for detection of IgM antibodies to Toxoplasma gondii and, therefore, for the diagnosis of acute congenital and acquired Toxoplasma infections.

https://jcm.asm.org/content/jcm/14/5/486.full.pdf

Immunoglobulin M-immunosorbent agglutination assay for diagnosis of infectious diseases: diagnosis of acute congenital and acquired Toxoplasma infections.

Toxoplasma gondii has a complex life cycle with multiple forms. Intermediate hosts such as humans are infected by sporozoites in oocysts or bradyzoites in pseudocysts whereas the sexual stages occur in the intestine of the definitive host, feline species. The parasite is unusual in that it does not need to pass through sexual stages or its definitive host for transmission to other species. This chapter summarizes the history of the discovery of the parasite, identification of the definitive host and transmission stages of the parasite, as well as other important discoveries in the basic biology and life cycle of T. gondii. This chapter also provides photomicrographs of the life cycle stages of this organism.

History and Life Cycle of Toxoplasma gondii

The preservation of a pure suspension of Toxoplasma gondii for use as antigen in a direct agglutination test for Toxoplasma antibodies is described. The test is macroscopic and avoids the use of live parasites; it is easily carried out and the results obtained have shown good correlation with other tests in common use. The specificity of the test was demonstrated by experiments on immunization, by absorption studies and by absence of cross-reactions in the sera of man and animals infected with a wide range of parasites. Agglutinins, which we have termed ‘natural’ agglutinins, appear to occur in some sera and can be absorbed with suspensions of T. gondii . The distribution of antibodies in approximately 500 blood donors engaged in sedentary occupations around London was determined. Males and females were equally affected and age appeared to be without influence on agglutinating titres. Chronic infection in rats gave rise to high agglutinating titres, and growth was retarded.

J.D. Fulton

Papers

Studies on agglutination of Toxoplasma gondii