My female chicken was born on June last year, and she was a free range chicken during her first 5 to 6 weeks of life. She was the most active, and one of the biggest chick in the clutch during her first few days of life. Five to six days after she hatch, I noticed that she have a slightly hard time swallowing food and water, but after those days, she ate and drink normally. When she was about 4 weeks old, she is about half the size of her brothers and sisters, and I noticed her stretching her neck and opening her mouth several times every minute, even at night time. There are no other symptoms, such as blood on the mouth. I researched about it, and I thought, that she have gapeworm. About 1 day after she first showed the symptoms, I wormed her with a drug, that contains praziquantel and oxfendazole. However, 4 days after her first dose, she doesn't appear to be improving. So, I decided to deworm her with noromectin( generic brand of ivermectin). About 68 hours after receiving her first ivermectin dosage, she doesn't show those symptoms anymore. I actually tried to deworm her with praziquantel and oxfendazole for 4 days consecutively and 2 consecutive days of ivermectin, before she doesn't show the symptoms. I continued to worm her with ivermectin 7 times within 10 day period. She slept on the ground with her siblings, when she showed those symptoms, but all of them didn't have those symptoms, and neither all of my chickens, even though, they continued to sleep on the same spot about 3-4weeks after she showed those symptoms. Today, she is about 20% smaller than her tallest sister, and she is about the same size as her other sisters. I wormed her with albendazole, 4 days ago for 3 days consecutively and I change the newspaper under her cage 2 times a week. Should I let her associate with the main flock? Gapeworms have indirect and direct lifecycle. Also, I want to know how efficient is ivermectin and albendazole on controlling gapeworms, Please provide a link.