Three key take-aways from the 5th International Symposium on Non-Surgical Contraceptive Methods of Pet Population Control, held last weekend in Portland, OR.

Dogs in the Lead

As the Alliance for Contraception in Cats and Dogs explains on the organization’s website, this meeting “[took] place at a critical juncture in development and use of permanent, non-surgical options for canines and felines.” Indeed, Zeuterin,* a formulation of zinc gluconate and arginine—and the “first FDA-approved non-surgical sterilant for male dogs—is scheduled to be launched commercially in the U.S. in mid-2013.”

A single testicular injection—which can be done without sedation—provides permanent sterility, and saves both time and money compared to traditional (i.e., surgical) castration. In addition, the procedure may appeal to people who want their dogs to retain an “intact” appearance.

Unfortunately, there are no non-surgical sterilants currently approved for use in domestic cats.**

But that’s not to say interesting work isn’t underway.

Julie Levy, Professor of Shelter Medicine and director of Maddie’s Shelter Medicine Program at the University of Florida, for example, discussed her research** examining the effectiveness of GonaCon in cats. Unlike Zeuterin, GonaCon—which was developed by the U.S. Department of Agriculture for use in white-tailed deer, and is now available through the agency’s Animal and Plant Health Inspection Service—uses an animal’s immune system to “tie up” gonadotropin-releasing hormone (GnRH), thereby “knocking out” all hormones downstream.

Among the challenges: (1) both the onset and duration of each cat’s immune response has proven highly unpredictable; and (2) injection site reactions in some cats that, while not painful, may suggest tumors. (It’s important, too, to point out that this work was done with a formulation of GonaCon that was not necessarily intended for use in domestic cats.)

Other researchers, supported by the Parsemus Foundation, are investigating the effectiveness of calcium chloride as “a low-cost nonsurgical sterilant for male dogs, cats, and other animals” with some promising preliminary results. Although ACC&D warns (PDF) that “published reports on the efficacy of intratesticular calcium chloride injections for inducing sterility in a variety of species are conflicting and incomplete, leaving many key questions unanswered,” the organization also acknowledges that “recent studies (and studies underway) have attempted to define and validate a single formulation, dosage, and administration protocol.”

For now, though, calcium chloride remains experimental—and lacks the FDA approval necessary for general use in pets (more on that below).

Drug Approval and Politics

“The regulatory authority for contraceptives for wildlife and feral animals,” explains APHIS on the agency’s website,  “was moved from the U.S. Food and Drug Administration to the U.S. Environmental Protection Agency (EPA)” in 2006. Considering how lengthy and costly the FDA approval process is, this will no doubt sound like good news to some.

The benefits of going the EPA route, however, are more than offset by the potential downsides. If free-roaming cats are considered “wildlife,” doesn’t that open up the possibility for legal hunting?

(Sound far-fetched? Not really. In 2005, the Wisconsin Conservation Congress put forward just such a proposal. “The statewide Conservation Congress caucuses ratified the proposal, 6,830 (57 percent) in favor, 5,201 (43 percent) against,” reported Animal People. In the end, though “the proposal died due to the threat of a gubernatorial veto.”)

I wasn’t the only one with this concern, either. Another attendee, who was very familiar with the regulation process its implications (having been either employed by EPA, or engaged as a consultant to the agency—I’m not sure which), asked during the Q&A session whether registration through the EPA—which oversees pesticide use—would effectively classify domestic cats as pests. A possibility with which he “was not comfortable.”

The bottom line: beyond all the biology, anatomy, and physiology, there is—as is often the case— politics.

Super (Population) Models

Having seen a preview of the simulation modeling work being undertaken by Philip Miller, senior program officer for the Conservation Breeding Specialist Group, and John Boone, senior biologist for the Great Basin Bird Observatory, just six months ago at The Outdoor Cat: Science and Policy from a Global Perspective, theirs were, for me, the two most highly anticipated presentations of the symposium.

I was not disappointed.

First, a brief description of the population model: what Miller and Boone have developed employs an unprecedented (to my knowledge, anyhow) level of sophistication, accounting for a variety of key inputs (e.g., age-based demographics, such as mean litter size, and survival rate; different spatial configurations, such as large and small urban areas, as well as less densely inhabited rural areas, etc.), some of which are typically ignored (e.g., abandonment of litters from owned cats, etc.). The “treatments” examined thus far include: (1) removal of any kind, (2) TNR, (3) a fictitious three-year contraceptive, and (4) a fictitious contraceptive of indeterminate duration.

Interesting as the model itself is, it was the results that we were all waiting to see. Again, I was not disappointed.

A few of the more striking findings: (1) as expected, removal is more effective than TNR at quickly reducing the number of cats in a given area, but (2) the difference between the two approaches was surprisingly small**** when it comes to the effort necessary to halt the population growth rate (i.e., moving 20 percent every six months vs. sterilizing/returning 30 percent every six months). If and when the model is able to account for cats removed for adoptions as part of a TNR program (common practice, of course), this gap should close further.

Also on the horizon (to be revealed, I hope, in November at the National Council on Pet Population/SAWA Research Day Symposium) is the inclusion of various cost factors, which ought to make the whole package enormously valuable to a range of stakeholders (e.g., animal control agencies, policymakers, etc.) interested in carefully evaluating their options for managing community cats.

I’ll be very surprised if traditional trap-and-kill comes out the winner.

•     •     •

Anybody interested in the topic is encouraged to download the recently updated version of Contraception and Fertility Control in Dogs and Cats, a free 154-page report available on the ACC&D website.

* Originally introduced in the U.S. as Neutersol, and known outside the U.S. today as Esterilsol.
** Two additional factors that must be considered for community cats: (1) surgical castration of male cats can be done very quickly, thus negating much of the benefit of an injectable like Zeuterin, and (2) unless and until an alternative to ear-tipping is developed, community cats will need to be anesthetized regardless of which sterilization technique is used—again, negating a key benefit of non-surgical sterilization.
*** All cats are adopted following their involvement with each study.
**** The surprise here wasn’t the relative difference but the absolute difference in control efforts. (A previous modeling effort “predicted effective cat population control by use of annual euthanasia of ≥50 percent of the population or by annual neutering of >75 percent of the fertile population.” [1])

Literature Cited

1. Andersen, M.C., Martin, B.J., and Roemer, G.W., “Use of matrix population models to estimate the efficacy of euthanasia versus trap-neuter-return for management of free-roaming cats.” Journal of the American Veterinary Medical Association. 2004. 225(12): p. 1871–1876. http://www.ncbi.nlm.nih.gov/pubmed/15643836