Trypanosomiasis

“The kiss of death”

 

 

 

Introduction

American Trypanosomiasis, also known as Chagas Disease, was discovered by Carlos Chagas.  In 1909, while working for the Oswaldo Cruz Institute, Chagas was sent to Lassance, Brazil to help fight an outbreak of malaria.  While living there, he observed that the rural homes were infested with “kissing bugs,” and that these bugs bit and sucked blood from faces of people while they were sleeping.  He decided one day to inspect the inside of the intestines of the bugs. Upon doing so he found a new species of flagellate protozoa.  He proved experimentally that monkeys could get this parasite by being bitten by an infected bug.  Because these bugs were found in people’s homes and biting them, Chagas suspected that this parasite caused disease in humans as well.  On April 23, 1909, he first discovered the parasite in the blood of a sick three-year-old girl, proving that it caused disease.

 

 

Transmission Aspects

        The disease is found in Mexico, Central American, and Northern South America. The causative agent, a protozoan parasite, Trypanosoma cruzi, enters the body through an open wound or mucous membrane.  The wound is normally caused by the bite of a revuiid bug, such as Triatoma infestans, Rhodnius polixus, and Panstrongylus megistus.

The revuiids are found in rural areas, in the cracks of poorly constructed homes.  Also, they are found in homes made from mud and thatch.  People who sleep in these kinds of homes are the most likely to become infected.  These bugs especially like to bite children on their faces, and are therefore known as “kissing bugs.”

The disease is transmitted a few different ways:

 

The bugs become infected after biting and sucking on the blood of an infected human or other animal.  A human that becomes infected when an open wound or mucous membrane comes in contact with the feces of these bugs.  The feces contain the parasites, which are in the metacyclic trypomastigotes stage of their lives.  Once inside the bloodstream, they penetrate various tissues.  Inside these cells the metacyclic trypomastigotes transform to amastigotes.  Within the infected cells, the amastigotes divide by binary fission.  The amastigotes once again become trypomastigotes, and then are released from the cells, destroying them.  At this point, the trypomastigotes can either infect other cells within the host or become amastigotes again, or they are ingested by a revuiid bug.  If ingested, the trypomastigotes develop into epimastigotes.  They multiply in the gut and then move to the hindgut, where they develop into metacyclic trypomastigotes.  At this point, they leave the host in its feces and then are free to infect other humans and animals.

 

 

There are no misconceptions of the spread of this disease.  Some people may think that just by staying in areas/countries where the bugs are found, they could get the disease. They have to stay in poorly constructed homes, this is where the bugs are founds.  Tourists are safe when they stay in hotels.

 

Damage Done to Host

 

Types of Damage:

The parasite T. cruzi plays a major role in creating organ lesions in the host, usually more commonly and intensively in the heart, esophagus and the colon. These lesions lead to an inflammatory response, cellular lesions and fibrosis.

 

Causes of Damage:

Trypansomas cruzi, the parasite involved in Chagas disease. It has four forms and only one is parasitic, the trypomastigote. The blood trypomastigote is an infective flagellate found in the blood and the metacyclic trypomastigote is found in the terminal part of the digestive and urinary tracts.


As with the transmission of the disease, there are no common misconceptions on how the disease is presented, except for how exactly the disease is contracted. The bugs themselves do not have the disease until they are infected with contaminated feces.

 

 

 


Clinical Characteristics

Signs and Symptoms

There are three stages of Chagas disease, the acute stage, intermediate stage, and the chronic stage, with each stage presenting different symptoms. The acute stage of the disease can occur within a few days to a few weeks of the initial bite. In the acute stage of Chagas the patients generally have a distinct swelling on one eye, called Romaña’s sign, other symptoms in this stage include:

The intermediate stage of the disease presents no symptoms and this stage occurs 8 – 10 weeks after infection and can last for many years before the chronic symptoms manifest. The chronic stage occurs years after the initial infection (10 – 30 years), and these symptoms are more devastating than that of the acute stage and they include:

 

 

Diagnosis of Chagas Disease

            During the acute stage of the disease the motile trypanosomes parasite can be detected by blood smears. To detect the parasite there are traditional methods that can be used including:

 

Though the above tests are highly specific they are very time consuming and have a low sensitivity. A more sensitive test that has proven to be a better alternative is PCR (polymerase chain reaction). The PCR technique is used to amplify the kinetoplast DNA of the trypanosomes, and it is a good detector of Trypanosoma cruzi. The best method to diagnose the chronic or intermediate stage of the test is by using serological test using the antibodies against the parasite. The serological test includes:

 

The problem with some of these test are that the results can be inconsistent, so a negative result does not actually mean that the person is free of infection. This is due to the low sensitivity of the test used. The serological test such as the ELISA, or IFA would show a positive result even though the parasitology test was negative. There should be more test performed for Chagas detection because some say that the serological test are accurate and other say that they are not.

            Once the disease has been diagnosed the appropriate course of treatment includes Benznidazole. Once the disease has proceeded to the chronic stage antibiotics are effective in treatment. There is currently no available vaccine for the disease.

 

 

 

References

 

Chiari Egler. Chagas Disease Diagnosis Using Polymerase Chain Reaction, Hemoculture and Serologic Methods. 1999; 299 - 300

Walter M. R. Oelemann, Maria Da Glória M. Teixeira, Giovani C. Veríssimo Da Costa,José Borges-Pereira, José Adail F. De Castro, José Rodrigues Coura, and José Mauro Peralta Evaluation of Three Commercial Enzyme-Linked Immunosorbent Assays for Diagnosis of Chagas ‘disease. 1998; 2423-2427

Murray, Patrick. Ken Rosenthal and Michael Pfaller. Medical Microbiology. 5th Ed. Elsevier Inc. 2005.

Kirchhoff LV. American trypanosomiasis (Chagas' disease)--a tropical disease now in the United States. New England Journal of Medicine. Vol. 329:639-644, August 26, 1993 

http://www.cdc.gov/ncidod/dpd/parasites/chagasdisease/factsht_chagas_disease.htm

 

http://www.who.int/tdr/diseases/chagas/diseaseinfo.htm

 

http://www.tulane.edu/~dmsander/WWW/224/Trypano.html

 

http://www.answers.com/topic/carlos-chagas

 

http://upload.wikimedia.org/wikipedia/en/b/b8/Chagas_disease_cycle.jpeg

 

http://www.cdc.gov/ncidod/dpd/parasites/chagasdisease/factsht_chagas_disease.htm#symptoms

 

http://memorias.ioc.fiocruz.br/94sup1/4400.pdf#search='hemoculture'

http://www.emedicine.com/med/topic327.htm

http://www.uta.edu/chagas/html/indxCycl.html

http://www.spectroscopynow.com/ftp_images/Digests34_Chagas.jpg

http://bmj.bmjjournals.com/content/vol326/issue7404/images/small/twib2806.f3.gif

http://cruzi.pathology.northwestern.edu/engmanlab/Rsrch/Figures/reduviid.jpg

 

 

Contact Info:
Bina Dharia
Jide Fagbemi
Ellen Valley

 

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