If you haven't jailbroken your iPad, you should feel safe and secure that your iPad is virus-clean and will likely remain so for the foreseeable future. There are no known iOS viruses that can infect an iPad or iPhone that has not been jailbroeken. Furthermore, Apple's app approval process also ensures that each app is checked for possible malware, granting an additional level of security.
The sandbox nature of mobile platforms makes operating systems like iOS and Android less vulnerable to viruses than traditional computers. Because each app runs in its own unique space and is very restricted on what device resources it can utilize, the mobile platform does tend to be safer than the desktop platform.
What about malware?
iOS did have a malware scare last year when an exploit was found that allowed PDFs to tunnel a hole through iOS's security. The PDF exploit required the user to open up a special PDF that utilized a bug in how the device handled TrueType fonts. This issue was cleared up with a subsequent patch, and no new malware threats have been leveled against the iPad or the iPhone.
Isn't there an anti-virus app for the iPad?
The iOS platform got its first official anti-virus program when VirusBarrier went on sale in the app store, but this anti-virus program is for checking files that may be uploaded to your Mac or PC. There are no known iOS viruses and no anti-virus apps targeted at the iPad or iPhone.