A word that means that a germ or disease can affect a species

I swear I've read a sentence like "Mosquitoes don't die of the diseases they transmit because those germs are not _____ to mosquitoes" or "Dragons' mouths aren't really clean, but they're generally not harmful to humans because the germs in a dragon's mouth are not _____ to humans".

Does this word exist?

pathogen - any disease-producing agent, especially a virus, bacterium, or other microorganism _{^{(dictionary.com)}}

pathogenic - capable of producing disease _{^{(thefreedictionary.com)}}

And an example usage approximating OP's context...

Seventeen different species of Yersinia genus have so far been reported, of which three have been shown to be pathogenic to humans and animals.

You might be thinking of susceptible and it is a term used in virology also.

with of or to: Capable of being physically affected by; esp. liable to take, subject to (a disease or other affection). OED

However, it is usually used as susceptible to < disease name/cause > thus you have to turn your sentences around.

...mosquitoes are not susceptible to those germs.

Here is an example from a scientific publication:

Such a mechanism is urgently needed by those working to reduce the impact of malaria by releasing strains of Anopheles, the vector of the disease, that are not susceptible to malaria parasites.

_{http://www.ncbi.nlm.nih.gov/pubmed/11527447}

_{(emphasis mine)}