Origin011

Trypanosoma and Darwin’s Disease

Trypanosoma is a genus of kinetoplastids (class Kinetoplastida), a group of unicellular parasitic flagellate protozoa. The name is derived from the Greek trypano (borer) and soma (body) because of their corkscrew-like motion. All trypanosomes are heteroxenous (requiring more than one obligatory host to complete life cycle) and are transmitted via a vector. The majority of species are transmitted by blood-feeding invertebrates, but there are different mechanisms among the varying species. When in the invertebrate host they are generally found in the intestine and, after transmission, they normally occupy the bloodstream or intracellular environment in the mammalian host.

Trypanosomes infect a variety of hosts and cause various diseases, including the fatal human diseases sleeping sickness, caused by Trypanosoma brucei, and Chagas disease, caused by Trypanosoma cruzi.

It has been hypothesized that Charles Darwin might have suffered from Chagas disease as a result of a bite of the so-called great black bug of the Pampas (vinchuca). The episode was reported by Darwin in his diaries of the Voyage of the Beagle as occurring in March 1835 to the east of the Andes near Mendoza. Darwin was young and generally in good health; though six months previously he had been ill for a month near Valparaiso. In 1837, however, and almost a year after he returned to England, he began to suffer intermittently from a strange group of symptoms, becoming incapacitated for much of the rest of his life.

Attempts to test Darwin’s remains at the Westminster Abbey by using modern PCR techniques were met with a refusal by the Abbey’s curator.

The Lab Model

An animal model is a living, non-human animal used during the research and investigation of human disease, for the purpose of better understanding the disease without the added risk of causing harm to an actual human being during the process. The animal chosen will usually meet a determined taxonomic equivalency to humans, so as to react to disease or its treatment in a way that resembles human physiology. Many drugs, treatments and cures for human diseases have been developed with the use of animal models. Many (but not all) laboratory strains are inbred, so as to make them genetically almost identical. The different strains are identified with specific letter-digit combinations; for example C57BL/6 and BALB/c.

Although some (but not all) of us might be comfortable with the use of rats and mice for this purpose, I felt that the idea of visually transposing this concept – through the use of a little modified colouring – onto my own pet Labrador might be worthy of investigation.