Continuity mistake: The fence at the start of the movie changes as Cujo chases the rabbit. In the shot as they run towards it, there is just one straight plank running across the bottom. When they reach it, there is now an askew, diagonal plank attached to the straight one. (00:02:00)
Continuity mistake: When the phone begins to ring, Cujo goes mad and starts bashing the side of the car in. He then shatters the passenger window of the car. In the very next shot it can be seen intact again and then alternates from shattered to intact from thereon. (01:01:15)
Continuity mistake: After Steve pushes Donna, the milk and eggs fall to the floor, and spill. In the next shot the size and the shape of the milk spillage is different than it was in the previous shot, and the position of the cracked eggs changes as well. (00:31:55)
Continuity mistake: When Cujo first attacks the car, he leaps and bounds all over it, smearing dirt and making muddy pawprints all over the windows and sides. In following shots, the muddy smears differ in shape and size, and then vanish. (00:48:30)
Continuity mistake: After shutting his closet door, Tad runs over to his lightswitch. In this shot the lamp on the desk, beside the lightswitch, is standing high up. In the next closeup of Tad reaching the switch, the lamp is in a different position, then switches back. (00:04:25)
Continuity mistake: When Cujo tries to get through Gary's netted door, it rips the netting and damages the wooden poles in the frame. In subsequent shots the amount of damage done to the poles and netting differs. (00:41:55)
Continuity mistake: When Donna takes Tad into the house, she pushes some items off of the table, and lays Tad down on the table. In following shots, items around the floor and on the table change position. Most noticeably is the milk carton beside Tad's head. (01:23:30)
Continuity mistake: The books, papers and toys by Tad's lamp, on the desk underneath the lightswitch, change arrangement, and some extra items appear, from when he turns off the light, to when his parents come in after he screams. (00:04:25 - 00:05:30)
Continuity mistake: Donna unrolls the car windows for some air becuase they're stuck in the car in a heatwave. Then her window is rolled up again in the shot where she tries to start the engine for Tad. She then rolls it down again after this. (00:57:35)
Continuity mistake: After shutting his closet door, and running over to his lightswitch, we get views of Tad's room at mulitple angles. The toys on Tad's large white fluffy area carpet change position a few times, between the wide and close shots. (00:04:30)
Continuity mistake: The position of the white chair, knocked over by Gary in the hallway, changes from when he initially pushes it over, when searching for a gun to kill Cujo, to after Cujo gets through the netted door, and a wideshot of the hall is shown. (00:41:50)
Continuity mistake: The position of the book on top of the TV keeps changing, as Tad watches Scooby-Doo whilst eating his breakfast at the table, and as the conversation between Donna, Vic, Tad and Steve continues through the scene. (00:08:15)
Continuity mistake: When Vic picks Tad up at his camp, we see Tad dip his finger in paint and begin finger painting. He then sees his dad and runs to him and gives him a hug and there is no paint on either of his hands or his dad's suit. (00:29:50)
Answer: Not really. Rabies has a wide range of behavioural symptoms, and it's rare for a rabid dog to display what's called "furious rabies," whereby they become more aggressive. And even then, they wouldn't become single-mindedly determined to terrorise two people in a car. It's much more common for a rabid dog to get slower/lethargic as paralysis sets in, eventually leading to coma and death. You can find more info here: https://vcahospitals.com/know-your-pet/rabies-in-dogs.