Toxoplasma gondii can infect almost all mammals and form cysts in the muscles and nervous system of the host. The host can be infected T. gondii two or more times depending on the amount of infection and the virulence . The method of isolate T. gondii in the world is used, which was biological separation of cats and mice.
How to guarantee that there is only one type of T.gondii strain isolated, and whether the genotype found by RFLP-PCR is related to the isolates? Additionally, if Neospora and T. gondii are separated at the same time, how do you get their own strains and what technology is used?
Mixed infection are quite uncommon.
Performing bioassay from sample of different organs or different parts of organ can be useful to increase the probability of detecting mixed infections (see erma SK, Sweeny AR, Lovallo MJ, Calero-Bernal R, Kwok OC, Jiang T, Su C, Grigg ME, Dubey JP. Seroprevalence, isolation and co-infection of multiple Toxoplasma gondii strains in individual bobcats (Lynx rufus) from Mississippi, USA. Int J Parasitol. 2017)
Microsatellite genotyping can be useful in this case due to its high resolution power and its ability to discriminate strains of the same lineage.
The problem is that if you conduct bioassay in mice with a sample containing more than one strain, one strain can multiply better than the other in the mice tissue. In this case, only one strain will be in sufficient amount in mice body to be successfully genotyped.
Another scenario is that one strain is virulent for mice and the other not virulent. In this case, mice will die of acute infection caused by the virulent strain; the virulent strain will be easly gentyping by puncturing ascitis or by peritoneal lavage. However, the non virulent strain will not be detected. Trying microsatellite genotyping on tissue pellet (digestate) may be useful to eventually detect the other strain but parasite burden is often low.
