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Will an immunocontraceptive work to control the burro population?

According to Marybeth Devlin, the burro immunocontraceptive may not work as the BLM predicts.

BLM photo

According to Marybeth Devlin, the burro immunocontraceptive may not work as the BLM predicts.

KINGMAN – From her home in Miami, Florida, Marybeth Devlin champions wild horses and burros roaming public lands, working independently and voluntarily as an advocate for the animals found mostly in the West.

She monitors news feeds and reports, which is how she came across a Feb. 8 Daily Miner story about the BLM vaccinating females with an immunocontraceptive called PZP to reduce the burro population in the Black Mountain Herd Management Area.

Devlin sent a 23-page report on her research of studies on the BLM’s fertility management pilot program using porcine zona pellucida, or PZP, also known as ZonaStat-H, an EPA-registered pesticide that induces infertility.

“PZP has many adverse effects as well as unintended consequences,” Devlin said in her report. “PZP is a dangerous pesticide whose use is antithetical to the spirit and intent of the wild and Free-Roaming Horses and Burros Act.”

The Black Mountain area is not overpopulated with burros, Devlin contends, citing a comment from Grace Kahler of the Humane Society of the United States.

The BLM uses population estimates that far exceed the actual number, she said. The estimate for the Black Mountain herd is around 1,800.

“Why would you subject them to such treatment if they’re not overpopulated?” Devlin asked during a telephone interview with the Daily Miner.

“They are America’s wild horses and burros. They belong to all of us, and they’ve become so oppressed and suppressed. Their habitat has been slashed in half and continues to be slashed.”

Devlin’s report delves into conflicts of interest between the Bureau of Land Management and Humane Society of the United States, false premises and fraudulent numbers, and additional concerns about the health effects of the PZP vaccine.

Kahler of HSUS said side effects are minimal with a small percentage of the female burros, known as “jennies,” having a reaction to the vaccine injection with small abscesses that usually resolves itself quickly.

Independent research shows otherwise, Devlin said. The hypothesis that PCP blocks sperm from attaching to an egg cell has “pretty much been debunked,” she said.

When researchers examined tissues and ovaries, they found the ovaries to be inflamed. PZP is used to induce inflamed ovaries.

Because PZP stimulates the immune system, it ironically works best – or sterilizes faster – in mares that have strong immune function. Those mares respond to the contraceptive vaccine and produce quantities of PZP antibodies that destroy their ovaries.

Conversely, PZP may not work at all in mares whose immune system is weak or depressed. They fail to respond to the vaccine and keep getting pregnant and producing foals who suffer from weak immune systems.

“If her immune system is weak, she won’t develop immune function. So generally over time, you’re selecting animals with weak immunity,” Devlin said. “They’re more susceptible to dying off if a disease swept through the herd.”

“It’s very frustrating to see them not being given a fair shake,” she said. “They need enough population for genetic viability.”