Dr. CheMyong Jay Ko, a reproductive endocrinologist, joined the faculty of the University of Illinois College of Veterinary Medicine in 2011, having spent the previous 10 years as a faculty member at the University of Kentucky College of Medicine. While he continued studying human reproductive physiology and the effects of environmental chemicals on gonadal and brain development at Illinois, he quickly found a veterinary research focus: development of a practical nonsurgical sterilant.
Why Nonsurgical Spays and Castrations?
Surgical sterilization for pets and male food animals has long been practiced to control overpopulation, eliminate unwanted behaviors, and improve meat quality. Yet there are drawbacks.
In pets, surgical sterilization uses up veterinary time and other resources, raises ethical questions about removing healthy organs, and has associated health risks for pets at the time of surgery and later in life. Piglets are routinely castrated at a very young age in the US by hand without administering local analgesia or general anesthesia.
Developing a New Way
Building on a study1 showing that daily doses of estradiol benzoate, a synthetic form of the reproductive hormone estrogen, inhibited the development of reproductive organs in newborn female rats, Dr. Ko began exploring a better way to sterilize animals.
“In newborn female mammals, the reproductive system is not yet functional,” says Dr. Ko. “The estrogen level in the body remains very low until specialized neuronal cells, called Kisspeptin neurons, develop in the hypothalamus, setting off a cascade of events that result in making the reproductive organs mature and functional.”
Dr. Ko’s team found a way to introduce estrogen into the body during the early, low-estrogen phase.2 The ill-timed rise of this hormone acts like an “off” switch to the development of reproductive organs.
Their process involves a single injection of pellets or microspheres that are designed to slowly release estrogen. Products that are formulated for females are called iSpay and those for males are name iNeuter. The product for piglets contains androgen in addition to estrogen and is delivered via biodegradable pellets.
Dr. Ko discusses research with a graduate student in his lab.
Citation: American Journal of Veterinary Research 85, 11; 10.2460/ajvr.24.09.0258
Moving Toward Commercialization
Both these methods have been patented for use in dogs, cats, and boars in the US and Europe through Dr. Ko’s biotech startup company, Epivara. Products are being developed also for cattle and goats.
“In all the species treated with this nonsurgical method, the animals mature normally except for their reproductive organs,” says Dr. Ko. Without functioning testes and ovaries, the animals have no sex drive, which eliminates negative behaviors in both domestic pets and pigs raised for meat.
As these nonsurgical sterilants move toward obtaining FDA and USDA approval, Dr. Ko believes that these products will have a positive impact on the careers of veterinarians and improve the well-being of animals.
References
- 1.↑
Minabe S, Ieda N, Watanabe Y, et al. Long-term neonatal estrogen exposure causes irreversible inhibition of LH pulses by suppressing arcuate kisspeptin expression via estrogen receptors α and β in female rodents. Endocrinology. 2017;158:2918–2929.
- 2.↑
Park CJ, Minabe S, Hess RA, et al. Single neonatal estrogen implant sterilizes female animals by decreasing hypothalamic KISS1 expression. Scientific Reports. 2023;13:9627.
