User:Sarazeidan

History

In 1643, captain William Mynors sailed past a small island close to Malaysia; they called it “The Christmas Island.” Many of the plants and animals found on that island were unique to it. These species included two endemic populations of rats. Unfortunately, these two species of rats have gone extinct. In the 1900’s, a parasitologist had noticed Rattus macleari species were getting sick, so he suspected they were getting sick because of a species of trypanosomes. There was no proof that this was actually correct until science and scientists came along. Some scientists from the American Museum of Natural History took some rats that had been collected from Christmas Island and deposited as specimen into museums. The scientists then found evidence that the parasite causing the disease and extinction is Trypanosoma lewisi. T. lewisi hopped off black rates on the ship, as the island’s rats transmitted the parasite. The hosts were killed by the parasite and got extinct.

Background

Trypanosome lewisi is a parasite of Rattus spp. It also infects other rodents such as: mice and kangoaroo rates in America. These species included two endemic species of rats, Rattus macleari and Rattus nativitatis. It is not very clear whether or not the same lewisi parasite infects both species. However, both parasites are very similar. Trypanosome lewisi is transported via the northern rate flea, Nosopsyllus fasciatus, where parasites develop in the midgut of the insect. Epimastigotes are the stage that is present in the insect, while trypomastigote is the stage that is present in the main host. Metacyclic trypomastigote appear in the rectum of the insect, which is how it infects the host. The rat will eat the flea or their feces, and that’s how it will get the disease.

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Research

         Many researches have been done on this parasite because it was easy to grow it in rats in the laboratory, which made it easier for the researchers to maintain it and get the results. Ablastin, an antibody that arises during an infection in the host’s body, was a fascinating subject for the researchers. 

A research paper was also consistent with some other data. The paper suggested that the introduction of a trypanosoma lewisi to immunologically naïve murine hosts on the island around 1900 matches the data that is now known of reports that have caused complete extinction within the range of 1-9 years. This gives some more information of the first pathogen introduction to a species that have caused species extinction.

Pathology

• A metacyclic trypomastigote will infect a rat after eating fleas or their feces. • The parasite will then begin reproducing epimastigotes in the blood capillaries of the host. • After about five days trypanosomes are appearing in the peripheral blood of the host as if they were thick worms. • These parasites are then going to be killed by trypanocidal antibody. • Additionally, after a few weeks the host produces another trypanocidal antibody, which kills the remaining trypanosomes. • The infection is then cured.

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References:

December 25 - trypanosoma lewisi . (2010, December 25). Retrieved from http://dailyparasite.blogspot.com/2010/12/december-25-trypanosoma-lewisi.html

Roberts, L., Janovy, J., & Schmidt, G. (2009). Foundations of parasitology. (8th ed., pp. 76-77). New York : McGraw-Hill.

Dept. of Zoology, University of Manitoba. (2000). Trypanosoma lewisi . Retrieved from http://umanitoba.ca/science/zoology/faculty/dick/z346/tryphome.html)