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Studies of Gastrointestinal and Other Parasitic Diseases


Research on various aspects of Giardia lamblia and Leishmania species are limited. Most studies are collaborative in nature.

Giardia lamblia (syn Giardia intestinalis, Giardia duodenalis) is the most common pathogenic intestinal parasite of humans worldwide and is a frequent cause of endemic and epidemic diarrhea and gastrointestinal upset. G. lamblia infects a wide range of mammals and humans but humans are almost always infected with genotypes A and B. G. lamblia isolates are composed of a group of related organisms or genotypes but little is known how they differ or the extent of their diversity and genomic coding differences.

We recently reported the genomic sequences of isolates GS( genotype B) and DH
( genotype A2) and compared them to a published draft sequence of GS and to the full sequence of isolate WB. The results show that GS is very different from WB and DH and strongly suggests it is a different species. Comparison of sequences of Giardia found in humans worldwide are being compared and analyzed under a collaborative study headed by Dr. Michael Grigg.

An increasing number of species of Leishmania cause primarily cutaneous, mucocutaneous, or visceral disease in humans. There is an imperfect correlation of the species, strain and isolate with the biology and response to treatment that is due to imperfect knowledge of genetic differences amongst different leishmania. Organisms and/or DNA that have been harvested from human lesions are being compared using multiple genetic loci and full genome sequencing in order to explain why these organisms differ. These studies are headed by Dr. Michael Grigg.

National Institute of Allergy and Infectious Disease
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