A couple of question about improving a monster

[Dr TPK]

Since dire rats are able to spread filth fever, I was thinking about monstrous mosquitoes that spread super ebola.
It's fairly straightforward, really: stirges with Int 0 and the vermin subtype and slimy doom (ex) special attack, spread through contact.

Two questions:
1. Should the disease attack increase the CR by 1 or 2?
2. The base CR is ½. Should the new CR be 1 (in case of increasing the CR by 1) or 2 (in case of increasing the CR by 2)?

[Bullet06320]

Plague Carrier (Template)

http://archive.wizards.com/dnd/article.asp?x=fr/pg20011219b

adds +1 to CR
for fractions usually round up, but this does seem to be an odd case for CR 1/2

[Dr TPK]

Plague Carrier (Template)

http://archive.wizards.com/dnd/article.asp?x=fr/pg20011219b

adds +1 to CR
for fractions usually round up, but this does seem to be an odd case for CR 1/2

Thank you so much, Bullet06320! Without you, I think I've never had found that template! Mostly because I'm jokingly "anti-Realms" DM/player, so I would've even looked that without your help.

[Bullet06320]

No prob, glad I could help. That particular template is buried deep in the archives, not one you can easily find anyways, but I'm a big realms fan and that's one of the gems I like. it actually took me a couple minutes to find the right article,lol