What preventive measures will be helpful to protect against this hazard [the interlopers doctoring dairy products with chronic viruses that cause cancer, autoimmune disorders, dementia, etc]?

Avoiding dairy products is the safest course of action. In addition, prayer work and repeat healing requests with the Lightworker Healing Protocol and Deep Subconscious Mind Reset can be used as prophylactic measures, as it will not be possible, always, to avoid ingestion as milk and dairy products are present in so many forms of food as ingredients. Cooking is not necessarily a guarantee of preventing infection with some of the agents being added by the interlopers. We understand this is a bombshell revelation considering its implications, its dark nature, and seemingly outlandish conspiracy theory makeup, but that can't be helped. Your world is a conspiracy from top to bottom because everything is corrupted and never far removed from the work of the interlopers, directly or indirectly.