It does not affect encysted larvae. It is very difficult to prevent mother to puppy transmission and routine deworming is not adequate. Once back in the intestine, the larvae complete their maturation and begin to mate. The first eggs are laid about one week after the fourth stage larvae have arrived in the intestine and about 4-5 weeks after infection has first occurred. From here the cycle repeats.
Roundworm infection can have numerous negative effects.
It is a common cause of diarrhea in young animals and can cause vomiting as well. Sometimes the worms themselves are vomited up which can be alarming as they can be quite large which females reaching lengths of up to seven inches. Very heavy infections can lead to pneumonia as the worms migrate and, if there are enough worms, the intestine can actually become obstructed. It is important to minimize the contamination of environmental soil with the feces of infected animals so as to reduce the exposure hazard to both humans and other animals. You may not know and this is one of the arguments in favor of regular deworming.