In the News: Vaccine Developed for Global Swine Disease

Newswise (07/10/06) — Researchers working in the Virginia-Maryland Regional College of Veterinary Medicine’s Center for Molecular Medicine and Infectious Diseases at Virginia Tech with funding support from Fort Dodge Animal Health Inc. have developed a vaccine to protect against Post-weaning Multi-systemic Wasting Syndrome (PMWS) in pigs, a major threat to the global swine industry.

The vaccine has been patented by Virginia Tech Intellectual Properties Inc. (VTIP) and is licensed and being marketed by Fort Dodge Animal Health Inc.

PMWS, caused by the Porcine Circovirus Type 2 (PCV2), has plagued the swine industry for almost ten years. By disrupting an animal’s immune system, the virus renders the pig susceptible to a range of clinical disorders and severely constrains weight gain and development.
The vaccine has been developed by Dr. X. J. Meng, a physician and virologist who is an associate professor in the VMRCVM’s Department of Biomedical Sciences and Pathology, and his former graduate student Dr. Martijn Fenaux who is now a postdoctoral associate at Stanford Medical School. Working in the college’s Center for Molecular Medicine and Infectious Diseases (CIMMID) for almost seven years in collaboration with scientists from Fort Dodge Animal Health Inc and colleagues at the Iowa State University, Meng and Fenaux have developed a vaccine that is expected to substantially reduce economic losses in the global swine industry.

“This new vaccine could save the United States and global swine industry millions of dollars in production losses caused by this virus, said Dr. Gerhardt Schurig, dean of the VMRCVM. “The invention of this vaccine is an excellent example of how our rapidly developing translational research programs can create rapid solutions for ‘real-world’ animal health problems.”

First identified in the early 1990’s, PMWS has been a major problem in Europe and Asia and recent outbreaks of PCV2-associated disease, with mortality rates as high as 30 percent, have been reported in the United States and Canada. The virus can cause significant disease in 30 to 50% of the animals it infects, causing major problems for production agriculture.

PMWS-associated mortality not only affects the health status of the herd, but also has a significant impact on an operation’s bottom line. For example, when mortality increases from 3 percent to 8 percent in a herd, the calculated losses are roughly $7.73 per pig, according to Fort Dodge Animal Health officials. When mortality increases to 30 percent, the losses are greater than $30 per pig.

The virus affects multiple organs in pigs, targets cells in the lymphoid tissues and causes the destruction of the pig’s immune system. “The hallmark pathological lesion is a depletion of lymphoid follicles,” said Meng. Because it disrupts the animal’s immune system, the virus is a co-factor in the development of other diseases known as Porcine Respiratory Diseases Complex, he said. Affected pigs have a history of wasting or poor performance, failure to thrive, respiratory disease and high mortality.

Because there are many unknowns about the transmission, pathogenesis, epidemiology and control of risk factors related to this disease, effective prevention is critical to the health and financial performance of the swine industry. The new vaccine offers swine producers a number of key advantages to aid in the prevention and control of these diseases.

“As an inactivated vaccine, there is no danger of reversion to virulence or potential for it to combine with field strains,” says Darrell Neuberger, DVM, Swine Technical Manager, Fort Dodge Animal Health Inc. “And with only one dose required for protection, Suvaxyn PCV2 One Dose is convenient and helps reduce labor costs. Single dosing also helps lessen the risk of reactions. During the field safety studies for this product, which included the vaccination of more than 1,100 pigs, no adverse events associated with the vaccine were reported by any of the four independent trial participants.”

Working in the Center for Molecular Medicine and Infectious Diseases, Meng and Fenaux utilized the genomic backbone of a non-pathogenic strain of a related virus known as PCV1 to produce a chimeric virus that expresses the immunogenic antigen of the disease-causing PCV2, thereby conferring immunity but not causing disease.

Meng subsequently collaborated with Iowa State University scientists Dr. Pat Halbur and Dr. Tanja Opriessnig to conduct the animal studies required to evaluate the pathogenicity, immunogenicity and vaccine efficacy of the chimeric virus. The studies revealed that the chimeric virus induces protective immunity against PCV2 infection in pigs, but retains the non-pathogenic nature of PCV1.

Meng said he is very pleased by the success of the vaccine. “As a scientist you conduct research and publish papers but usually you do not see the immediate impact of your research,” he said. “But I feel like with this vaccine I am really doing something to serve society.”

Meng, a physician and Ph.D. virologist, operates one of the world’s top laboratories in the investigation of Hepatitis E viruses. In addition to the extensive funding he has received from Fort Dodge Animal Health Inc, U.S. Department of Agriculture, and several other funding agencies to support the PCV2 and PMWS work and his research on several other viruses of veterinary and public health concern, he has been awarded approximately $2 million from the National Institutes of Health to study the Hepatitis E Virus, which is a major threat to people and animals.

Photo credit: David Beart