Toxoplasma gondii

Test code: X0002

Test name: Qualitative detection of Toxoplasma gondii by polymerase chain reaction

Infections by Toxoplasma gondii are prevalent in many species of domestic and wild animals (Dubey, 1993). Although chronic infection of this obligate parasite is usually asymptomatic, T. gondii has emerged as a major opportunistic pathogen in the immunocompromised, such as AIDS patients. Surprisingly, spontaneous cases of fulminating fatal toxoplasmosis have been reported in adult squirrel monkeys (Saimiri sciureus) which are immunologically normal (Inoue, 1997). While the disease mechanism of this fatal toxoplasmosis in squirrel monkeys is not clear, infections of nonhuman primates with this parasite are common, and it has been shown that New World monkeys are more susceptible to T. gondii infection than Old World monkeys (Ruch, 1959). The outbreak of fatal toxoplasmosis (Cunningham, et al., 1992) is a major concern in caring for these primate colonies, as a recent study has indicated the possibility of horizontal transmission through the respiratory route (Furuta, et al., 2001) in addition to the fecal-oral route.

The “gold standard” for the detection of T. gondii in clinical specimens is mouse inoculation and detection of T. gondii specific antibodies. This method is sensitive and specific but very time-consuming, taking up to six weeks to obtain a diagnosis. Cell culture detection of this parasite is also slow, and lacks sensitivity. PCR detection of this parasite has been found to be a sensitive, specific and rapid method for the detection of T. gondii DNA in a wide spectrum of samples, such as amniotic fluid (Grover, et al., 1990), blood (Dupouy-Camet, et al., 1993; Ho-Yen, et al., 1992), tissue samples (Johnson, et al., 1993) and cerebrospinal fluid (Cristina, et al., 1993; Farmley, et al., 1992). Although serology testing can help diagnose recent infection with this parasite, PCR testing is found to be more sensitive in identifying acute infection (Hussein, et al., 2002).

Utilities:

• Confirm the disease causing agent
• Shorten the time required to confirm a clinical diagnosis of T. gondii infection
• Ensure that horse populations are free of T. gondii
• Early prevention of spread of this parasite
• Minimize human exposure to this parasite
• Safety monitoring of biological products that derive from horses

References:
Dubey, J.P. (1993) Toxoplasma, Neoplasma, Sarcocystis, and other tissue cyst-forming coccidian of human and animals. pp1-56. In: Parasitic protozoa (Kreier, P.J. ed), vol. 6, 2nd ed., Academic Press, Inc., San Diego, California.
Inoue, M. (1997) Acute toxoplasmosis in squirrel monkeys. J. Vet. Med. Sci. 59:593-595.
Ruch, T.C. (1959). pp.297-299, 313-318, 423-424. In: Diseases of laboratory primates. W.B. Saunders Co., Philadelphia.
Cunningham, A.A., Buxton, D. and Thomson, K.M. (1992) An epidemic of toxoplasmosis in a captive colony of squirrel monkeys (Saimiri sciureus). J. Comp. Pathol. 107:207-219.
Furuta, T., Une, Y., Omura, M., Matsutani, N., Nomura, Y., Kikuchi, T., Hattori, S. and Yoshikawa, Y. (2001) Horizontal transmission of Toxoplasma gondii in squirrel monkeys (Saimiri sciureus). Exp. Anim. 50:299-306.
Grover, M.C., Thulliez, P., Remington, J.S. and Boothroyd, J.C. (1990) Rapid prenatal diagnosis of congenital Toxoplasma infection by using polymerase chain reaction and amniotic fluid. J. Clin. Microbiol. 28:2297-2301.
Dupouy-Camet, J., de Souza, S.L., Maslo, C., Paugam, A., Saimot, A.G., Benarous, R., Tourte-Schaefer, C. and Derouin, F. (1993) Detection of Toxoplasma gondii in venous blood from AIDS patients by polymerase chain reaction. J. Clin. Microbiol. 31:1866-1869.
Ho-Yen, D.O., Joss, A.W.L., Balflour, A.H., Smyth, E.T.M., Baird, D. and Chatterton, J.M.W. (1992) Use of the polymerase chain reaction to detect Toxoplasma gondii in human blood samples. J. Clin. Pathol. 45:910-913.
Johnson, J.D., Butcher, P.D., Savva, D. and Holliman, R.E. (1993) Application of the polymerase chain reaction to the diagnosis of human toxoplasmosis. J. Infect. 26:147-158.
Cristina, N.H., Pelloux, C., Goulhot, J.P., Brion, P., Leclercq, P. and Ambrosis-Thomas, P. (1993) Detection of Toxoplasma gondii in AIDS patients by the polymerase chain reaction. Infection 21:150-153.
Farmley, S.F., Goebel, F.D. and Remington, J.S. (1992) Detection of Toxoplasma gondii in cerebrospinal fluid from AIDS patients by polymerase chain reaction. J. Clin. Microbiol. 30:3000-3002.
Hussein, A.H., Nagaty, I.M. and Fouad, M.A. (2002) Evaluation of IgM-ELISA versus PCR in diagnosis of recent Toxoplasma gondii infection. J Egypt Soc Parasitol. 32:639-46.

Specimen requirements: 1 ml whole blood in EDTA (purple top) or ACD (yellow top) tube, or 1 ml amniotic fluid, CSF or tissue, shipped overnight at room temperature; or tissue shipped frozen.

For specimen types other than those listed here, please call to confirm specimen acceptability and shipping instructions.

For all specimen types, if there will be a delay in shipping, or during very warm weather, refrigerate specimens until shipped and ship with a cold pack unless more stringent shipping requirements are specified. Frozen specimens should be shipped so as to remain frozen in transit. See shipping instructions for more information.

Turnaround time: 2 business days

Methodology: Qualitative PCR

Normal range: Nondetected