Can you get ivermectin pour-on 5 mg per ml from a cattle or pig feed store or online? Dosage for chickens is 0.1 ml for every 2 pounds of weight applied to the back of the neck between the shoulders on the spine. Repeat in 14 days. Since it is not approved for poultry due to a long egg withdrawal, I would discard the eggs for at least 7 days. Here is an article about egg withdrawal and brand names in the UK:
https://poultrykeeper.com/poultry-medication/ivermectin-for-worms-lice-mites/
https://poultrykeeper.com/poultry-medication/ivermectin-for-worms-lice-mites/