New test detects PEDV antibodies in pigs

New test detects PEDV antibodies in pigs

VETERINARY researchers at Iowa State University have developed a new test to detect antibodies against porcine epidemic diarrhea virus (PEDV).

Previously, the virus could be detected only in acute cases while it was still reproducing and infecting a host pig. In such cases, the virus could be identified through the use of a polymerase chain reaction assay. However, Iowa State said those tests could give a false negative if the pig had stopped shedding the disease or if shedding had become intermittent.

The new test — called an immunofluorescence antibody assay or indirect fluorescent antibody assay — is conducted using blood samples from pigs and will allow veterinarians and producers to know if a pig has ever had PEDV in the past, regardless if the animal is shedding the virus or not. It's the first test available to the U.S. veterinary community that can detect PEDV antibodies, Iowa State said.

"The new test gives practitioners and their clients a historical perspective," said Dr. John Johnson, a clinician in veterinary diagnostic and production animal medicine. "It'll help them to understand if a particular animal has been exposed to the virus before. This tool, coupled with polymerase chain reaction results, will provide additional crucial information as veterinarians and their clientele assess the risk of moving a group of animals into a PEDV-negative population."

Dr. Kyoung-Jin Yoon, a professor of veterinary diagnostic and production animal medicine at Iowa State, led the effort to develop the new test.

The screening works by detecting the presence of PEDV antibodies in a blood sample. If the antibodies are present, then the pig in question has been exposed to the virus before, Yoon said.

The screening test, available through the Iowa State Veterinary Diagnostic Laboratory, costs $5.50 per sample and can be requested by local veterinarians.

"In order for this test to function, we must first have an isolated virus on hand," Yoon said. "For a long time, it has been difficult to isolate the virus in a cell culture, so there are a lot of tricks and manipulation we have to do to make this virus propagate in cell culture."

The test will be especially helpful to pork producers who are looking for replacement breeding stock, Johnson said. By performing the test, producers can know if an animal has been exposed to the virus in the past before they bring PEDV onto their farms.

The Iowa State Veterinary Diagnostic Laboratory identified the first U.S. cases of PEDV in early May. Since then, the diagnostic laboratory has helped confirm cases of the disease in 17 states, including Iowa, Yoon said.

The virus was first diagnosed in 1971 in the U.K., and Europe has experienced sporadic outbreaks in the years since, while the disease has become prevalent among pigs in Asia since 1982.

The primary symptom of PEDV, which is spread through fecal matter, is severe diarrhea in pigs of all ages, with high mortality in neonatal piglets. The most common sources of infectious feces are infected pigs and contaminated trucks, boots and clothing, making biosecurity measures on farms especially important for containing the spread of the disease, Iowa State said.

 

Biosecurity guidelines

The National Pork Board reiterated that manure is a primary way PEDV spreads from pig to pig and from farm to farm and announced a new set of biosecurity guidelines for producers and commercial manure haulers.

"We know this virus is easily spread to uninfected pigs and clean farms by infected manure," said Dr. Paul Sundberg, vice president of science and technology for the pork checkoff. "As we enter the fall manure application season, it's a particularly critical time to follow a strict set of steps to help prevent the spread of this costly virus."

The new guidelines, available at www.pork.org/pedv, are specifically offered for producers and commercial or other manure haulers who travel from one farm to the next and during land application of manure. The guidelines were developed by veterinarians and university experts working with the pork checkoff, the National Pork Producers Council and the American Association of Swine Veterinarians.

Both producers and haulers should know where the transport crew has been prior to coming onto a new farm. In addition, farms should have a clearly defined entrance and exit strategy to minimize cross-contamination with other farm traffic and maintain a distinct "line of separation" among haulers, their equipment and the animals and workers on the farm site (Feedstuffs, Sept. 16).

Sundberg added that separating manure hauling equipment and personnel from animals and farm workers — as well as limiting on-farm movement patterns — have proved to be critical in avoiding potential PEDV transmission via manure to an uninfected farm.

"The cornerstone of the new manure handling guidelines is communication between the manure hauling crew and farm managers and workers," Sundberg said. "If we are to be successful in reducing the spread of PEDV, all workers must follow biosecurity procedures by respecting this line of separation."

 

Sow lameness

Decreasing sow lameness helps improve herd productivity and profitability through improved reproductive performance and longevity, according an announcement from the Feet First Team, an international collaboration of researchers, veterinarians and nutritionists focused on swine welfare and helping improve the efficiency of pork production through the identification and prevention of lameness.

Sows that are better able to move through the facility on a structurally sound set of feet and legs have a greater opportunity to reach their full potential. Producers can help prevent sow lameness by monitoring and treating lame sows and preventing problems before they occur, the team said.

Sow lameness is a prevalent issue in the U.S. swine industry. In fact, lameness and its effect on swine reproduction are responsible for the culling of more gilts and first-parity sows — up to 50% of the sow herd, according to some estimates — than all other production factors combined.

In addition to higher culling rates, lameness can affect joint, muscle and skeletal development, and its stress on the sow is shown to influence reproduction through longer wean-to-estrus intervals, more non-productive sow days, a smaller litter size, fewer pigs weaned and poor fertility, the announcement said. Decreased feed consumption caused by lameness can also lead to issues due to decreased body condition scores.

"Recognizing and understanding the factors contributing to sow lameness is the first step to deal with this growing problem," Dr. Mark Wilson, a reproductive physiologist at Zinpro Corp., said. "Sow lameness affects all aspects of swine production, including gilt development schemes, parity distribution and nutritional requirements."

Early cases of lameness may be illustrated through: shortened stride, uneven steps and stiff joints; obvious head bobbing while walking; swaggering of the hindquarters; arched back while walking; reduced weight bearing on affected limbs, and/or reluctance to move.

Claw lesions are commonly found on 15-40% of developing gilts. Inflammatory lesions cause pain and stress, directly affecting the animal's performance. The Feet First Team has a "Feet First Claw Lesion Scoring Guide" available at http://bit.ly/1aX1wY8 to determine the type of claw lesion that may be affecting a sow or gilt.

Although there are treatment options, preventing sow lameness before it occurs is a producer's best bet, the announcement said. Wilson said gilt and sow nutrition plays a large role in a lameness prevention program.

"Research has demonstrated that feeding amino acid complexes helps to improve horn quality, decrease claw lesions and prevent a decline in reproductive response among young sows," he said. "Feeding the combination of zinc, manganese and copper as amino acid complexes helps optimize the foot health and reproductive performance of gilts and sows."

Wilson explained that the trace minerals zinc, manganese and copper each play a role in keeping sows' feet healthy. Zinc is responsible for corium health, wound healing and sole, heel and wall horn strength and elasticity. Manganese strengthens the density of joints, tendons and bones. Copper is important for connective tissue, white line health and sole, heel and wall horn strength and elasticity.

 

Feed enzymes

Multi-enzyme dosing, whether achieved using a single fermentation product with multiple activities or a blend of single activities produced separately, does not necessarily increase animal performance, according to AB Vista research manager Dr. Helen Masey O'Neill.

"Individual feed enzyme characteristics and dose have a far greater impact on improving feed conversion ratio and cost savings than the number of enzymes present," she said. "The effects of combining multiple feed enzymes are not additive or necessarily worthwhile."

The interactions that result from multi-enzyme dosing are extremely complex, with the outcome affected by the feed ingredients used, differing enzyme characteristics, substrate availability and enzyme activity end products.

"As a result, even in the limited number of studies where complete comparisons have been made, the best single-enzyme products usually match and sometimes outperform those with multiple activities," Masey O'Neill said. "It's also much harder to get multi-enzyme products to perform consistently across all diet types or achieve required levels of thermostability for all constituent enzymes."

Very little published information has shown the survivability of each component of a multi-enzyme following feed manufacture, AB Vista pointed out. Often, only key activities of the product are described, yet it is known that each constituent probably differs in thermostability.

Volume:85 Issue:39

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