Trypanosoma cruzi (Chagas' disease)

Test code: X0010 - Ultrasensitive qualitative detection of Trypanosoma cruzi by real time polymerase chain reaction

Trypanosoma cruzi, a protozoan parasite, causes Chagas' disease (“American trypanosomiasis”). It is transmitted through parasitic blood-feeding arthropod vectors of the family Reduviidae, particularly Triatoma spp. (assassin bugs or  "kissing bugs"), which occur naturally in Central and South America. These insects normally transmit the infectious stages of the protozoa to mammals through contamination of the insect's bite by its feces, although vertical transmission of T. cruzi has also been shown to occur (Azogue et al., 1985; Miles, 1972). Various mammals, including human beings, are the natural hosts of Triatoma spp. as well as T. cruzi. Wild-caught New World monkeys from Central or South America are often infected with Trypanosoma species, including T. cruzi. Old World monkeys, including some macaques (eg Macaca mulatta, Macaca silenus, Macaca nigra) and lemurs (eg Lemur catta), are also susceptible when translocated into the geographic range of reduviids or when experimentally infected.

Infected animals may remain subclinical for years or may infrequently produce a variety of clinical effects such as anorexia, dyspnea, fever, leukocytosis, lymphadenopathy and myocarditis. During remission, the parasite may remain undetectable in the blood for long periods, then return to detectable levels periodically, often triggered by stress or immune system challenge. In humans, reactivation of Chagas' disease in patients infected with the human immunodeficiency virus (HIV) has been reported since the early 1990s. The clinical manifestations of reactivated Chagas' disease are severe central nervous system (CNS) alterations and cardiomyopathy. Trypomastigotes of T. cruzi, observed by direct microscopic examination of blood smears, characterize the acute phase of infection and confirm Chagas' disease reactivation. Reactivation of T. cruzi has also been reported in rhesus monkeys experimentally infected with SIV.

Traditional laboratory diagnosis of T. cruzi relies on blood smear observation or serological detection. Unfortunately, these methods lack sensitivity and specificity. PCR detection of this parasite offers significant advantages over traditional methods in terms of both specificity and sensitivity (Ndao et al., 2000; Gutierrez et al., 2004).

Utilities:

• Help confirm the disease causing agent
• Shorten the time required to confirm a clinical diagnosis of T. cruzi infection.
• Help ensure that animal groups and populations are free of T. cruzi
• Early prevention of spread of this parasite among a population
• Minimize human exposure to this parasite

References:
Azogue, E., La Fuente, C. and Darras, C. (1985) Congenital Chagas' disease in Bolivia: epidemiological aspects and pathological findings. Trans R Soc Trop Med Hyg 79:176-180.
Gutierrez, R., Angulo, V.M., Tarazona, Z., Britto, C. and Fernandes, O. (2004) Comparison of four serological tests for the diagnosis of Chagas disease in a Colombian endemic area. Parasitology. 129:439-444.
Miles, M.A. (1972) Trypanosoma cruzi-milk transmission of infection and immunity from mother to young. Parasitology 65:1-9.
Ndao, M., Kelly, N., Normandin, D., Maclean, J.D., Whiteman, A., Kokoskin, E., Arevalo, I. and Ward, B.J. (2000) Trypanosoma cruzi infection of squirrel monkeys: comparison of blood smear examination, commercial enzyme-linked immunosorbent assay, and polymerase chain reaction analysis as screening tests for evaluation of monkey-related injuries. Comp. Med. 50:658-665.

Specimen requirement: 0.2 ml whole blood in EDTA (purple top) tube, or 0.2 ml plasma, serum or CSF.

Contact Zoologix if advice is needed to determine an appropriate specimen type for a specific diagnostic application. For specimen types not listed here, please contact Zoologix 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 real time PCR

Normal range: Nondetected