A number of Internet Web sites feature extensive information on conservation buffers. Among those sites listed in a recent issue of the Natural Resources and Conservation Service's Buffer Notes are:
The last Web site includes the full text of each issue of "BufferNotes," and most contain links to other sites.
The NRCS/USDA Web site includes worksheets for specific conservation buffer practices and guidance on how to select and size conservation buffers.
Cases of circovirus identified at the Iowa State University Diagnostic Laboratory have jumped more than 200-fold since the first case was diagnosed in 1996.
The virus, thought to cause the porcine multisystemic wasting syndrome, also may be a player in porcine respiratory disease complex, says Pat Halbur, Iowa State veterinary pathologist.
"Diseases involved in PRDC look similar based on clinical signs and gross lesions, so diagnostics need to go beyond that," he says. "We need to consider circovirus because it can look like porcine reproductive and respiratory syndrome, and its presence may explain why pigs fail to respond to treatment."
Some herds in the Southeast and Midwest are experiencing 8 percent to 12 percent mortality rates in finishing barns.
"We're finding severe Mycoplasma, PRRS, secondary bacteria and circovirus in many of the pigs coming to our laboratory for diagnostic investigation," says Halbur. "First, we look at compliance – whether pigs received the Mycoplasma vaccine properly. Then, we're concerned about the effect of other immunosuppressive viruses – PRRS and circovirus – on a Mycoplasma vaccine's ability to work."
In some cases, increased ulcers observed in PRDC cases also are being associated with circovirus infection, says Halbur. "We think this is caused by a combination of stress, pigs going on and off feed due to the disease and circovirus-associated vasculitis in the stomach wall."
Infection duration among herds will vary, but PMWS is often a single-batch problem, he explains. With all-in/all-out pig flow and proper sanitation, subsequent batches often do fine. However, in an increasing number of cases, PMWS has been detected in successive groups from a specific sow herd for two to four months or longer.
There are two types of circovirus. Type 1 is endemic in pigs and nonpathogenic. Type 2 circovirus is found consistently in PMWS lesions. Concurrent PRRS infection has been confirmed in more than 60 percent of PMWS cases submitted to Iowa State's diagnostic lab, but Halbur suspects it's even higher.
"Vaccination with a Mycoplasma vaccine administered at the proper time is the most effective strategy," he adds. "Strategically placed feed-grade antibiotics also are beneficial. Anytime you have the tools to eliminate or minimize one of the complex's major players you should. Mycoplasma and swine influenza virus are two primary players in PRDC, for which producers have excellent control tools."