Yeah, that's kinda the point.

The stuff doesn't have instructions on the side of the box for what the human doses would be, so if you do the math wrong you're easily going to overdose yourself. Since we can assume that there isn't a regular doctor visit scheduled to check up on the patient, there is less chance that there is somebody who will be paying attention to enough vital stats to know when to stop treatment.

And its not like we know how many people are using horse paste instead of getting the vaccine, so if somebody has just been steadily dosing themselves for long periods of time the stuff is going to build up the system. Its why it causes liver problems.

When given to livestock, you only give like one or two doses and wait for the parasite poison to do its thing. You watch the animal to see if it starts gaining weight, if its poop is filled with dead worms, if the animal is acting like it has more energy.

Since that won't happen with people trying to treat cold/flu symptoms, I'd imagine that its really easy to just take horse paste in the same way I take cough syrup and antihistamines when I get a cold, I'm not surprised if people are overdosing themselves on Ivermectin.