By Peter Bowes in Los Angeles

Americans and visitors to the United States are being warned to take extra care to avoid snakebites this summer.

Hospitals throughout the country are suffering from an acute shortage of the medicine needed to treat potentially lethal injuries caused by rattlesnakes.

"It's a pretty scary situation," says Jzenica Pierson, who lives on a ranch in Canyon Country, California.

"We have dogs and 50 horses and a two-year-old son. Our main concern is our child."

In California, the situation appears to be more threatening since, based on anecdotal evidence, snakes are being discovered in greater numbers around homes and out-buildings.

Russ Smith says people are often bitten while trying to catch snakes

While no statistical proof exists - and some experts suggest there has been no actual growth in snake populations - it is thought that the recent extremely dry winter may account for the increased number of sightings.

Over the past year, some areas of Southern California have suffered their lowest rainfall levels on record.

Russ Smith, curator of reptiles at the Los Angeles Zoo, says the snakes are simply hungry.

"What's happening is their food supply, the rodents, rats and ground squirrels, which need the moisture, are coming down to find water and all these predators follow."

Antivenin shortage

Around 8,000 people suffer venomous bites every year in the US. Nine to 15 victims die.

Around cities such as Los Angeles and San Diego species like the Southern Pacific Rattlesnake are prevalent in rural areas and on walking trails.

"We've been finding a couple a day," said Jzenica Pierson. "We've really been trying to teach our son the difference between a good snake and a bad snake but when they're little it's pretty hard to tell and children are pretty impetuous."

Experts advise against trying to kill rattlesnakes

Worldwide, there are only two manufacturers of the necessary snake antivenin, which is sometimes referred to as antivenom.

A British company, Protherics, produces the CroFab serum. The product has recently taken over as the principle form of treatment in the US for snakebites. A recent glitch in the manufacturing process led to the shortage in supplies.

The problem has been resolved and, according to Stuart Heard, executive director of the California Poison Control System, 3,000 vials of the antivenin were recently shipped to the US.

However, he warns: "There has been such a substantial shortage throughout the country that we believe those 3,000 vials will quickly be dispersed and there will still be a shortage for a time to come."

No guarantees

To try to alleviate the situation in California, a state-wide agreement was reached this week to encourage hospitals to share information about the available stocks of antivenin.

However, as Jzenica Pierson discovered, supplies remain perilously low.

"We've already called two hospitals in our area to confirm that they have antivenom.

"One stated that they did and another stated that they did on that day but they wouldn't guarantee that they would on another day."

Experts agree that the best way to escape a potentially life-threatening situation, is to avoid being bitten in the first place.

Natural pest control

"A large percentage of those bitten are young males who've been consuming alcohol," says Stuart Heard. "It's something for people to remember if you're out picnicking or hiking or fishing."

"Leave it alone," adds, Russ Smith. "Most people that are bitten by a snake are trying to catch or kill it."

While killing the snake is not the recommended course of action, it remains the instinctive response of some people faced with the danger.

In fact, there is much to be said in the rattlesnake's favour.

"You hate to see population decline in anything," says Russ. "All snakes do a lot of good as far as rodent control is concerned."