Abstract
BackgroundGiardia spp. are flagellated protozoan parasites that infect humans and many other vertebrates worldwide. Currently seven species of Giardia are considered valid.ResultsHere, we report a new species, Giardia cricetidarum n. sp. in hamsters. Trophozoites of G. cricetidarum n. sp. are pear-shaped with four pairs of flagella and measure on average 14 μm (range 12–18 μm) in length and 10 μm (range 8–12 μm) in width. The trophozoites of the new species are generally larger and stouter than those of most of the other Giardia spp. and exhibit the lowest length/width ratio (c.1.40) of all recognized Giardia species. Cysts of G. cricetidarum n. sp. are ovoid and measure on average 11 μm (range 9–12 μm) in length and 10 μm (range 8–10 μm) in width and are indistinguishable from the cysts of other Giardia species. Molecular phylogenetic analyses based on beta-giardin, small subunit rRNA, and elongation factor-1 alpha loci all demonstrated that G. cricetidarum n. sp. is genetically distinct from all currently accepted Giardia spp. Investigation of the host range indicated that the new species was only found in hamsters (including Phodopus sungorus, P. campbelli and Mesocricetus auratus), while all the other described mammal-parasitizing species (G. muris, G. microti and G. intestinalis) each infect multiple hosts. Cross-transmission studies further demonstrated the apparent host specificity of G. cricetidarum n. sp. as it only infected hamsters. Trophozoites were found in high numbers in hamster intestines (5 × 105 – 5 × 106) and was rarely detected co-infecting with other Giardia spp. in the common hamster, suggesting it has some advantages in parasitizing hamsters.ConclusionsThis study has identified a new species of Giardia, which appears to be specific to hamsters, and together with the three other mammal-parasitizing Giardia species with different host ranges, may be able to be used as a model system for the study of evolutionary divergence of host parasitism strategies in Giardia.
Highlights
Giardia spp. are flagellated protozoan parasites that infect humans and many other vertebrates worldwide
Sequence analysis at multiple loci is essential for the identification and classification of Giardia, and the following genes are most widely used: the glutamate dehydrogenase, beta-giardin, elongation factor-1 alpha, triose phosphate isomerase and small subunit small subunit ribosomal RNA (rRNA) (SSU rRNA) [5]
Collection and purification of trophozoites and cysts Giardia trophozoites were collected from hamsters (Phodopus sungorus, Kunming, China) which were bought from pet markets
Summary
Giardia spp. are flagellated protozoan parasites that infect humans and many other vertebrates worldwide. Since Antony van Leeuwenhoek first observed and recorded Diplomonadida in 1681, the flagellated protozoan intestinal parasite, Giardia Künstler, 1882, has attracted the attention of scientists for many reasons in the past 300 years [1]. Giardia spp. are the most common intestinal protozoan parasites of humans and many other vertebrates worldwide; infection can cause giardiasis, the symptoms of which include acute or chronic diarrhea, The taxonomy of Giardia spp. is usually based on morphological characters of the trophozoites and cysts [3]. Lyu et al Parasites & Vectors (2018) 11:202 the most common characters used for describing and identifying Giardia spp. Within G. intestinalis, genetic analysis has identified eight assemblages, A-H: assemblages A and B in humans and other mammals; assemblages C and D in dogs and other canids; assemblage E mainly in ungulates, assemblage F mainly in cats; assemblage G in rats and mice; and assemblage H in marine mammals [6, 7].
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