From the box of horse paste Ivermectin;
IverCare (ivermectin paste) 1.87% may be used in horses of all ages, including mares at any stage of pregnancy. Stallions may be treated without adversely affecting their fertility.
Horse breeders would not be using ivermectin if it affected the fertility in their horses.
There are some species of animals that cannot handle ivermectin, including certain breeds of dogs. Could that include the animals they used for their testing? Never wormed a rabbit before... possibility.
A scientist from Merck teamed with Japan scientist Dr. Satoshi Omura who discovered the single sample of avermectin of which Ivermectin is a derivative. The two worked together to
develop the successful parasiticide Ivermectin and in 2015 shared the Nobel Prize for science and medicine. Over the years Ivermectin saved millions of lives from many parasitic diseases in second world countries. For this collaboration,
Merck needn't be painted with the Big Pharma is bad brush.
Is there a link to the article referenced? Can't be read as is.