Introduction:

Over the years, humane and effective desire for controlling the population of dogs and cats has led to research into non-surgical sterilization methods (Spehar, 2015). Different methods have been studied using chemical sterilizers, vaccines, and gene-editing techniques. However, it cannot be said that we have found the holy grail of non-surgical sterilization methods. Recently, scientists in Iran, India and the United States have succeeded in making great strides in the field of research of non-surgical sterilization for dogs and cats.

Contraceptive vaccine, named GonaCon, has been created in Iran to target hormones associated with the fertility in dogs and cats. The drug operates via influencing the immune system to form antibodies against GnRH which is an important hormone of reproductive functioning (Smith, 2016). Through GnRH receptors blocking, GonaCon offers to animals regardless of gender a non- surgical fertility suppression. Another striking advantage of GonaCon relates to its long duration of effect, in this case the same dose supplies protection against pregnancy for a period of many years. It means that it will become a good option for controlling stray animals under the urban and rural areas where condition to surgical sterilization is impractical or excessively expensive. Furthermore, addition and GonaCon also turns out to be safe and reversible, which makes it a flexible option for the animal welfare organizations and the local authorities (Fagerstone et al., 2010).

Indian researchers have succeeded in taking contraception via chemical compound called calcium chloride dihydrate-non surgical route. This compound when injected into the testes or ovaries of cats and dogs causes local inflammatory response which is optimum for long term infertility. The procedure, known as intratesticular or intraovarian injection of calcium chloride, is yet quite simple, cheap and can be done by any trained veterinarian in a veterinary setting or in the field as well. The CaCl2 dihydrate as an injectable contraceptive has increasingly been adopted in India as a cost-effective measure inhibiting stray animals’ breeding, thus opening avenue for mass sterilization campaigns. There is also a need to focus on a particular dosage and method of applying calcium chloride and initial studies show that it is safe and effective, as well as contraceptive for the long term (Kutzler, 2015). By employing both the GonaCon vaccine in Iran, and the calcium chloride injection in India, innovative sterilization methods devoid of the need for surgery are demonstrated as to have the capacity to transform animal control strategies, globally. This innovation has a humane and non-depletable solution to dilemma of overpopulation on animal welfare organizations hence improving the health of stray animals in communities across the world.

Zeuterine:

In Iran, researches have been putting their efforts that Zeutrine for non-surgical sterilization of stray animals. Zeutrine which is a combination of zinc gluconate and arginine was incubated to aid in the prevention of surgical sterilization. Preliminary experiments gave good results, and Zeutrine was shown to be able to sterilize animals effectively without the second operation. They regarded this approach as a groundbreaking method in the field of animal welfare, an economically conscious and humane solution to stray animals’ overpopulation problem (Rafatmah et al., 2019). Likewise, in India, postsurgical sterilization methods for stray animals have been developed and researched. Zeutrine was one of the entities demonstrating the effectiveness that this direction can bring into our production processes. Injections of the drug were formulated to ensure there would be a convenient, less invasive approach compared to the traditional surgical sterilization methods. The most appealing factor about zeaturnine is its ability to be used on widespread scale thus an animal’s scale is obstructed through a few and efficient sterilization process (Woodward et al., 2017).

However, the future of the company was somewhat problematic due to the rise of its challenges that ultimately led to the discontinuation. The challenge the researchers faced was the limited scope of the current technology to alter or improve the compound’s formula, dosage, and delivery to the target cells.

Promising drugs:

Zinc gluconate, when injected into testis or ovaries becomes immortal by way of endometriosis and scarring. Although this method is quite effective, it requires careful administration and it can prove to be hard to implement it in large scale. Some compounds like calcium chloride and glycerin have also shown some ably encouraging results at this earlier stage of the research (Kutzler, 2015). Suprelorin is approved for administration to male dogs in Australia as well and Europe; in the latter region, vets must pay US$100 for a single 9.4-mg implant (M. Brash, personal communication). Progestins, estrogens, and androgens are examples of steroid hormones that have been used to suppress reproduction in canines, animals at zoos, and some wild species. Since blocking ovulation and exhibiting behavioral symptoms of estrus requires higher dosages of these hormones than contraception, it is feasible that animals who would not normally be able to conceive experience ovulation and exhibit estrus-related behaviors (Massei and Miller, 2013). Levonorgestrel, melanogaster acetate (MGA), and megestrol acetate (MA) are examples of synthetic progestins. When MA was given orally for eight days, beginning at a very particular period of the estrous cycle (proestrus), it prevented estrus in 92% of bitches. It was used for dogs and cats for many decades under numerous brand names.

Investment in this area:

One prominent organization in this field is the Alliance for Contraception in Cats & Dogs (ACC&D). ACC&D is dedicated to advancing non-surgical sterilization methods for dogs and cats. They collaborate with various research institutions, pharmaceutical companies, and government agencies to fund and support research in this area. Before 2008, researchers had very little access to competitive research grants from organizations or the federal government to study technology for reliable and efficient contraception in dogs and cats. The Found Animals Foundation was founded in 2008 by orthopedic physician Gary Michelson, MD, of Los Angeles, with the goal of reducing or doing away with the country’s practice of euthanizing cats and dogs at shelters. In addition to providing $50 million for Research Grants in Reproductive Biology (www.michelsonprizeandgrants.org), he also financed a $25 million Michelson Prize in Reproductive Biology.

The goal of the prize and funding is to find a single-dose, non-surgical, safe, affordable sterilant that works for both male and female cats and dogs and lasts for their 10- to 20-year lifespan. Additionally, the sterilant needs to be able to be administered in a field setting, have a pathway to US Food and Drug Administration (FDA) regulatory approval as a veterinary prescription product, and ablate the presence or action of sex steroids (thereby preventing both sexual behaviors and mating). It is preferable if the sterilant is an injectable (SC, IM, or IV). Although the Foundation’s primary goal is to decrease the number of animals put to death in shelters, it also hopes that a successful product will be made accessible to organizations that control feral and community- owned cat and dog populations both domestically and abroad (Johnston and Rhodes, 2015).

Conclusion:

Although a lot has been achieved, there is also a number of issues that still need to be addressed. Maintaining the effectiveness of any chemical sterilizing agent is the highest priority of the research, along with the development of an administrational strategy for mass deliverance of this product. The ethical issue of the potential after-effects of these biotech tools on the long- term animal welfare and the environment should be addressed as well. Although the search for a miracle pill still ongoing, a holistic approach that mixes several techniques of population control may be right for effective dog and cat homelessness population control.

References:

Spehar, D.D., 2015. Unowned Cat Management in the State of Ohio: Elements of Best Practice in Public-Private Collaborative Efforts.

Smith, G.P., 2016. Immunocontraceptive vaccines against brucellosis and population growth in feral swine (Doctoral dissertation, Virginia Tech).

Fagerstone, K.A., Miller, L.A., Killian, G. and Yoder, C.A., 2010. Review of issues concerning the use of reproductive inhibitors, with particular emphasis on resolving human‐wildlife conflicts in North America. Integrative Zoology, 5(1), pp.15-30.

Kutzler, M.A., 2015. Intratesticular and intraepididymal injections to sterilize male cats: From calcium chloride to zinc gluconate and beyond. Journal of feline medicine and surgery, 17(9), pp.772-776.

Rafatmah, D., Mogheiseh, A., & Eshghi, D. (2019). Chemical sterilization with intratesticular administration of zinc gluconate in adult dogs: a preliminary report. Basic and clinical andrology, 29, 12. https://doi.org/10.1186/s12610-019-0092-8

Woodward, K.N., Keesler, R.I., Reader, J.R. and Christe, K.L., 2017. Evaluation of a zinc gluconate neutralized with arginine product as a nonsurgical method for sterilization of Rhesus Macaques (Macaca mulatta). Journal of the American Association for Laboratory Animal Science, 56(5), pp.520-526.

Johnston, S. and Rhodes, L., 2015. No surgery required: the future of feline sterilization: an overview of the Michelson Prize & Grants in Reproductive Biology. Journal of feline medicine and surgery, 17(9), pp.777-782.

Massei, G. and Miller, L.A., 2013. Nonsurgical fertility control for managing free-roaming dog populations: a review of products and criteria for field applications. Theriogenology, 80(8), pp.829-838.