The course of giardiasis in Mongolian gerbils and SCID mice infected with new strains of Giardia lamblia

The infectivity of Giardia isolates in Mongolian gerbils and in SCID mice inoculated with a newly established G. intestinalis strains of human origin (ISO/90/1, ISO/90/2) and a reference strain ATCC 30888 has been investigated. Inoculation of Mongolian gerbils with trophozoites resulted in an acute and reproducible pattern of infection. 36% of inoculated gerbils showed symptoms of infection after a first inoculation, whereas the second inoculation resulted in infection of 85% of the same gerbils. The group of SCID mice infected with ISO/90/2 failed to release cysts in the fecal material, while the second inoculated group infected with ISO/90/1 showed a low number of cysts at 13 days post inoculation. Cyst excretion was intermittent, mostly released during the second and the third week of infection. Mongolian gerbils are a useful animal model, whereas SCID mice are not, to assess viability and infectivity of parasites from various sources. Strain differences may contribute to the development of different pattern of infections, which lead to clinical consequences in the diagnosis of giardiasis.