Can't enable ServerSideIncludes - a2enmod not found

I have configured httpd.conf to enable server side includes on my Bitnami LAMP stack with virtual hosts. I'm reading the instructions for Ubuntu instances here,

https://help.ubuntu.com/community/ServerSideIncludes

and I have found where I need to add "Includes" and the two lines to enable in httpd.conf:

...
    Options FollowSymLinks MultiViews Includes
...
AddType text/html .shtml
AddOutputFilter INCLUDES .shtml

The very first instruction for enabling includes won't work:

sudo a2enmod include

This post references a particular module that must be loaded: http://answers.bitnami.com/questions/13067/wordpress-multisite-stack-how-to-use-a2enmod-to-enable-an-apache2-module

.. specifically: LoadModule expires_module modules/mod_expires.so

I checked my httpd.conf, and that line IS enabled.

So I don't know why SSI is not working; can you advise?

Toolie