From my inbox, courtesy of the Spartanburg Humane Society in SC:

$10 heartworm clinic:

4/8 – 1:30 – 4:30 pm

Heartworm tests and brief exams for dog & puppies 8 weeks and up for the low price of $10. Inexpensive heartworm preventative & flea/tick products will be available.  All dogs must be on a leash.  No appointments necessary. First come, first served.

The Spartanburg Humane Society

150 Dexter Road

Spartanburg, SC 29303

Additional info here.  There is another clinic scheduled for April 24.

I’ve posted on heartworm dosages for dogs here.