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Avian botulism strikes early

August 01, 2001|By MARIO RENTERÍA, Staff Writer

An unexpected early outbreak of avian botulism type C has already claimed more than 200 endangered California brown pelicans and 15 American white pelicans at the Sonny Bono Salton Sea National Wildlife Refuge.

A press release from the U.S. Department of Fish and Wildlife Service states although outbreaks occur annually they don't usually start until late July, continuing until the weather cools in September.

"Last year we were taken by surprise when birds began to show signs of infection two weeks earlier than normal, but this year we began to see ill birds in early June," said Sylvia Pelizza, law enforcement project leader with the Salton Sea Authority.

Avian botulism occurs yearly at the Salton Sea after temperatures reach the low 100s for several weeks. Several weeks at more than 100 degrees trigger a massive growth of algae that robs fish of oxygen in the water.


The fish most commonly affected are tilapia, an exotic, stocked species that is the pelicans' preferred food.

When pelicans eat tilapia affected by the algae, the birds are "poisoned."

It is suspected the type C botulism resides in the guts of tilapia and environmental conditions trigger the disease pathogen.

Tilapia are easy targets for juvenile pelicans because the fish become sluggish when deprived of oxygen. That explains why many of the affected birds are young.

Birds that contract avian botulism lose involuntary muscle control, including eyelid function, have clenched feet and can't hold up their heads.

The disease is not fatal if treated in the early stages but pelicans are not easily captured until they start showing these symptoms and are seriously ill.

Dead and dying birds are removed quickly to prevent other birds from feeding on their bodies and spreading the disease.

This year, high temperatures started during a two-week period in May, triggering the outbreak, according to the press release.

Fluctuating temperatures since have kept bird deaths low, with an average of 20 sick birds and five to 10 dead ones being picked up from the sea weekly.

Biologists expect several hundred more pelicans to succumb to the disease once temperatures reach into the mid-100s, stated the press release.

The 2000 outbreak was the longest botulism season on record. It began June 26 and lasted through the end of November. It claimed more than 784 birds, including 557 brown pelicans.

Staff from the U.S. Fish and Wildlife Service, California Department of Fish and Game and the Salton Sea Authority are patrolling the sea daily, picking up sick and dead birds to keep the disease from spreading further.

"We are working with our partners to do everything we can to quickly retrieve and treat sick birds," said Pelizza.

Sick birds are immediately taken to the refuge's field hospital, where they spend up to 24 hours and are given fluids and antibiotics. They are cared for prior to being transported to one of five certified off-site care centers in Indio, Irvine, Huntington Beach, San Pedro or San Diego.

Biologists have treated 117 sick birds this year, stated the press release.

Of more than 110 ill brown pelicans retrieved from the Salton Sea, 50 have been treated and released on the coast near the Fish and Wildlife Service's Tijuana Slough and Seal Beach national wildlife refuges.

The Fish and Wildlife Service plans on combating the disease when its peaks with 16 employees who will work in 12-hour shifts to care for the sick birds.

Two airboats patrol the sea all day, three to five times a week, to round up sick birds and ferry them to the rehabilitation center.

The California Department of Fish and Game already has purchased an airboat and hired additional personnel to assist with disease response efforts.

Staff Writer Mario Rentería can be reached at 337-3435.

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