Submitted to: Journal of Parasitology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 20, 2009
Publication Date: October 1, 2009
Citation: Miska, K.B., Jenkins, M.C., Trout, J.M., Santin, M., Fayer, R. 2009. Detection and comparison of giardiavirus (GLV) from different assemblages of giardiia duodenalis. Journal of Parasitology. 95(5):1197-2000.
Interpretive Summary: Giardia duodenalis is a protozoan parasite that is an important human pathogen that causes digestive disorders in people. Often a treatment of antibiotics is necessary to clear the infection which if left untreated can last up to several weeks. Giardia can be divided into seven distinct assemblages that infect different hosts. Because some but not all of these are infectious to humans it is important to be able to discern the type of assemblage present in a given host. In the present study we attempted to use a giardia virus protein (GLV) sequence to type Giardia derived from several different hosts. The giardia virus, is an RNA virus that has been shown to infect Giardia. We were able to recover virus sequence from some samples but were unable to recover them reliably from all samples. Additionally we found multiple virus sequences from a single assemblage, suggesting that more than one virion can simultaneously infect a single field sample. Altogether, it is unlikely that giardia virus sequences can be used to distinguish Giardia assemblages, because the virus may be absent, or multiple virions can be present.
Five assemblages of Giardia were identified from cysts in cattle, dog, cat, sheep, and reindeer feces using ribosomal DNA (rDNA) sequencing. Assemblage A was present in cattle and reindeer feces, Assemblages C and D were present in dog feces, Assemblage E was present in cattle and sheep feces, and Assemblage F was present in cat feces. Giardia virus, originally referred to as Giardia lamblia virus (GLV), is a double-stranded RNA virus. Primers designed for the GLV capsid protein gene identified GLV sequences in Giardia from a reindeer (Assemblage A) and from a dog (Assemblage C). Two distinct GLV sequences were identified in the dog specimen and one sequence was identified in the reindeer specimen. None of these GLV sequences were identical with previously published GLV sequences. It appears that GLVs are genetically diverse, and more than one virion can be present in a single sample. Because many of the specimens that contained cysts were found negative for GLV it appears that this test for capsid protein is of limited value for the purposes of detecting Giardia.