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More producers accepting concept of biological prevention

Veterinarians, nutritionists and producers in China fill room at recent meeting to learn more about coccidiosis vaccination.

Coccidiosis is one of the most severe parasitical diseases of broilers and broiler breeders in China, often presenting with severe clinical signs, including red blood in the feces, poor flock uniformity and mortality.

The costly parasitic infection can cause subclinical disease, too, characterized by signs such as poor weight gain. Subclincal disease is more likely to occur when other conditions, particularly necrotic enteritis, are present.

"In the past, we mainly adopted three methods for control of coccidiosis," says Tai Youhua, DVM, director of the Animal Health Center for Zhucheng Foreign Trade Broiler Co. Ltd, the second- largest broiler integrator in China's Shandong Province.

"First we managed the rearing style, such as rearing birds on net. Second, we rotated and shuttled the anticoccidials in feed. Third, we administered various anticoccidial medicines, including diclazuril, or sulfa drugs," he says.

"But none of these methods generated the same efficacy as they had before. Due to resistance, in-feed anticoccidials such as ionophores and synthetic chemicals are no longer as efficacious as they once were, and it was time to adopt a new way of thinking in coccidiosis control by developing immunity through vaccination," Tai adds.

Medication problems

Besides resistance, he says, controlling coccidiosis with medications raises another problem: Residues. Sulfa drugs such as sulfaquinoxaline and sulfadimidine are highly efficacious in reducing mortality and controlling symptoms. As a result, sulfa drugs are frequently the product of choice in China when coccidiosis breaks out due to their efficacy and cheaper price.

"But there are restrictions on sulfa drug residues in poultry to be exported to Japan," Tai says. "It is difficult for us to monitor the choice of anticoccidial by contract growers, so residues are a big concern for poultry meat exporters."

In addition, there are restrictions on residues in exported broiler meat for medicines including clopidol and nicarbazine, which along with sulfaquinoxaline have been banned by the Ministry of Agriculture of China. It is likely that more in-feed anticoccidials will be banned in the future, he predicts.

The solution: vaccination

Because resistance and residue were serious concerns for export-oriented and "green" bird integrators, Zhucheng started vaccinating day-old chicks with Coccivac-B, which provides lifelong protection against four leading species of Eimeria that affect broilers. The birds are vaccinated in the hatchery with a specially designed spray cabinet that provides uniform dosing.

The result, according to Tai, has been good control of coccidiosis. There has been a significant reduction in the need for treatment and subsequent concern about residues. The vaccine also has replaced field-resistant oocysts with highly sensitive vaccine oocysts, he says.

Vaccinating for coccidiosis, Tai continues, also provides an excellent method of avoiding problems with resistance and residues. The oocyst species used to produce the vaccine were isolated before in-feed anticoccidials on the market were launched and are therefore highly sensitive to all approved ionophores and chemical treatments. That's why replacing resistant field strains with oocysts in the vaccine is beneficial, he says.

"Since the end of 2001, we have vaccinated about 25 million birds with Coccivac-B," reports Wang Chunming, chief veterinarian of the Animal Health Center. "In fact, we mandated that all birds reared on the floor must be vaccinated at day of age by Coccivac-B through spraying in the hatchery.

"Our growers have accepted the concept of vaccination, especially since they saw the results obtained with the first 1.3 million birds either vaccinated or medicated respectively," he adds.

Those results showed that vaccinated birds had an equal or better performance index than non-vaccinated birds. "As a result, growers no longer use anticoccidials in feed for prevention or in drinking water for treatment, except for the occasional use of diclazuril to control mild post-vaccination reactions. We are free of coccidiosis and residues in broilers," he says.

Technical service crucial

Because biological prevention against coccidiosis is a new concept for the broiler industry in China, successful implementation of coccidiosis vaccination required good technical service.

According to Tai, Schering-Plough Animal Health's technical personnel introduced the advantages of coccidiosis vaccination and created interest in Coccivac-B. They defined a trial protocol based on local conditions with clients and taking into account the location, number of birds, groupings and measurement index. The team of specialists also provided crucial supportduring the trial, including on-site visits at 7, 14 and 21 days post-vaccination. The trial enabled customers to realize the advantage of Coccivac-B and helped Schering-Plough Animal Health learn how to adapt Coccivac-B to local conditions.

"We have about 2,500 growers," adds Wang. "It is very difficult for us to teach all growers about using Coccivac- B in a short time."

As a result, Schering-Plough Animal Health's technical staff in China provided training to most of the growers, which are located in 75 villages within a 200 km radius. In addition, the company provided a concise and easily understood post-vaccination management list, which included information on feed, litter, moisture, necrotic enteritis and vaccination reaction control, he says.

The training, coupled with post-vaccination on-site visits and management tips, enabled growers to develop adequate skills and knowledge about Coccivac-B. "That eventually solved the problems of resistance and residues - both issues that perplexed our business before," Wang says.

Schering-Plough Animal Health's technical service specialist David Xuan agrees, adding, "The success of Coccivac-B depends on post-vaccination management, which must be customized to the local situation. Coccivac-B can become the best choice for coccidiosis control if a concrete and practical technical service plan is provided."

Source: CocciForum Issue No.7, Schering-Plough Animal Health.

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