Delusional parasitosis is a form of psychosis characterized by the false belief that one is infested with some sort of parasite. It can be triggered by a variety of brain diseases, including parasites themselves.
Avoiding meat and other animal products can certainly reduce our risk of becoming infested with parasites, but may place us at risk for vitamin B12 deficiency (see Vegan Epidemic), which can have its own dire cognitive consequences (see Inverted Rabbit Sign). See Safest Source of B12 for the best way to get this critical vitamin. For more on pork tapeworm brain invasion, check out Pork Tapeworms on the Brain, and Avoiding Epilepsy Through Diet. Be sure to check out my other videos on brain health, including Improving Mood Through Diet; and Constructing a Cognitive Portfolio.