After sustained pressure from animal rights groups and a member of Congress, the Army has agreed to stop injecting monkeys with high doses of a nerve-blocking drug meant to simulate a nerve gas attack.

The practice, carried out at Aberdeen Proving Ground in Harford County, Md., is designed to train Army medical personnel to respond to chemical attacks on troops.

Last month, Aberdeen received a shipment of 20 male African green monkeys from a Florida company, Worldwide Primates, for the tests, which the Army has been carrying out since at least 2005. Army documents show the monkeys were to be anaesthetized, injected with a nerve-blocking agent, physostigmine, and observed by Army medical personnel before receiving an antidote.

Worldwide Primates obtained the monkeys from the Caribbean island of St. Kitts, according to Army documents.

Army spokesman Michael Elliott confirmed Thursday that the Army Medical Research Institute of Chemical Defense at Aberdeen will “phase out” the nerve tests on the primates, also known as vervet monkeys, although he did not provide a timeline.

Screengrab from a video of the tests conducted by the U.S. Army. (COURTESY OF PHYSICIANS COMMITTEE FOR RESPONSIBLE MEDICINE)

However, Rep. Roscoe G. Bartlett (R.-Md.), who pushed the Army to end the testing, said in a telephone interview that he met last month with two generals who indicated that they would halt the testing by the end of the year.

Instead, the Army will switch to trained actors, computer programs and high-tech, mannequinlike patient simulators.

“The Army is committed to providing its health care providers with the best possible training while reducing reliance” on animals, Elliott said in a statement.

In 2008, the Army sought 48 of the small monkeys for the tests, according to documents obtained via the Freedom of Information Act by the Physicians Committee for Responsible Medicine, an animal rights group.

An Army video also obtained by the group shows a vervet monkey spasming after a physostigmine injection. The drug can cause seizures at high doses.

Physostigmine is used infrequently in humans to treat the nerve disease myasthenia gravis, but only in doses 30 to 60 times lower than those received by the Army monkeys.

In August, PCRM formally petitioned the Defense Department to end the tests, saying that they were inhumane and a poor training tool.

“Using African green monkeys to try to demonstrate effects of nerve gas exposure on humans is not accurate. The physiology is not accurate,” said John J. Pippin, a physician with PCRM. “Many of the first signs in humans — sweating, dilation of pupils — can’t be assessed. Also, participants in the course don’t actually do anything except hold a bag to help the monkey breathe.”

An independent expert agreed that patient simulators, which can be programmed to show symptoms of a nerve gas attack, would provide better training.

“It would be a little bit hard to look at a monkey with these symptoms and learn something about what a human would look like,” said Eric Toner, an emergency physician and senior associate at the Center for Biosecurity, part of the University of Pittsburgh Medical Center. “The purpose of training like this is to have first-hand experience. I imagine it would be more effective to use patient simulators. They’re getting more and more sophisticated all the time.”

Other animal rights groups, including the People for the Ethical Treatment of Animals and the Humane Society International, had also protested the practice. The issue gained celebrity traction last month when actor Woody Harrelson wrote the Defense Department asking for an end to the monkey tests.

“I have a lot of respect for the U.S. Army,” Harrelson wrote in an e-mail sent via his agent. “They’re some of the bravest, most selfless people I’ve met, so it’s gratifying to me to see them take this humane course of action.”

Maj. Gen. James K. Gillman of the Army Medical Research and Materiel Command and Maj. Gen. Nick Justice of the Army Research, Development and Engineering Command disclosed the decision in a meeting with Bartlett in September.

“I’m very pleased they’re phasing it out,” Bartlett said. “If you want to see the reaction a live animal has, you can show a film of it. You don’t have to repeat it over and over. There are lots of technologies they can use instead.”

Before Bartlett joined Congress, he worked at the Navy’s School of Aviation Medicine and performed medical tests on a squirrel monkey named Baker that was shot into space.

In the years since, Bartlett has argued against medical tests on non-human primates, except in limited circumstances.

Elliott, the Army spokesman, said the decision did not apply to any other military animal tests.

The military has a long history of testing drugs — and weapons — on animals. From 1998 to 2006, at least 11,000 military animal experiments were conducted, according to PETA, which found the information in an Army database.