I meant to reply to this when I first read it but was in the middle of something and forgot until now... I am quite surprised they diagnosed Toxoplasma- was it sent to the lab or diagnosed in house? In house diagnositics very rarely are able to diagnose Toxoplasma as both serological tests and fecal exam usually do not show the parasite. The eggs are extremely small and are generally indistinguishable from other parasitic eggs when viewed under a microscope. So, if they did in house tests, I'd be questioning their diagnosis for sure and would definitely get a second opinion. If the chin was in fact infected with Toxoplasma, it would be exhibiting more neurological signs than just diarrhea.
How is the chin doing? What medication did they give you? Even in dogs and cats, there are no 'approved' treatments for Toxoplasma infection.