Giardia fears

Two days ago, I was awaken early in the morning by Riley scratching at the bedroom door, asking to go out. Riley rarely gets up in the morning until I do, even though Jeffrey is already up. So this was an unusual event. But I figured he may have heard something downstairs and wanted to check it out. When I didn't get up, he came over to my side of the bed, sticking his nose up to the edge of the bed, and tried to wake me up politely with a few tail wags. I ignored him, turning over to catch the last 15 minutes of sleep. A few minutes later I awake to the sound of gutteral wretching. Oye! Poor guy was feeling ill and tried to tell me to open the door and let him out. Luckily, it was just a little yellow bile. I chocked it up to the canned cat food Jeffrey likes to give him now and then.
Then there was a little diarrhea here and there. Not horrible, so I don't worry too much. Again, I chock it up to something he may have picked up at the dog park, in the creek, or mud.
As I pull out of the driveway on my way to Lion Dance practice though, I see my neighbors with their Yorkie puppy. They tell me that little Doughnut has picked up a parasite, Giardia. Ah-ha! They think she may have picked it up at the dog park. It's definitely a possibility. All sorts of wildlife live at that reservation park.
So I'm now faced with the possibility of a stomach parasite that is potentially lethal. I decide against going to the allopathic vet for testing. They would need a fresh stool sample and I've already been fasting him to clean out his gut so no samples to give. Also, if he did test positive, the standard practice is to treat with Flagyl, which is an antibiotic.
Here's the info I dug up on Flagyl:
DRUG CLASS AND MECHANISM: Metronidazole is an antibiotic effective against anaerobic bacteria and certain parasites. Anaerobic bacteria are single-cell living organisms that thrive in low oxygen environments and can cause disease in the abdomen (bacterial peritonitis) liver (liver abscess), and pelvis ( abscess of the ovaries and the fallopian tubes). Giardia lamblia and ameba are parasites that can cause abdominal pain and chronic diarrhea in infected individuals. Metronidazole selectively blocks some of the cell functions in these microorganisms, resulting in their demise.
SIDE EFFECTS: Metronidazole is a valuable antibiotic, and is generally well tolerated with appropriate use. Serious side effects of metronidazole are rare; and include seizures and damage of nerves resulting in numbness and tingling of extremities (peripheral neuropathy). Metronidazole should be stopped if these symptoms appear. Minor side effects include nausea, headaches, loss of appetite, a metallic taste, and rarely a rash.

Kinda sounds like a lot of common drugs that doctors and vets prescribed to us. But I have just read a recent post on my Natural Berner yahoo list about someone's dog having a severe reaction to Flagyl. Plus, it really doesn't make any sense to me to treat a parasite with an antibiotic. But without my own plan in place to talk to the vet about, I decided to contact my holistic vet. She is out of town and I speak to the very knowledgeable receptionist for a few minutes. We decide to fast and make sure he stays hydrated. I will keep an eye on him tomorrow and decide if we want a definitive diagnosis. I am hoping that by starving the parasite, Riley's own immune system will fight this off.

In the meantime, some of my internet mentors send me some suggestions. Para-GARD, Panacur, and Sulfur. I have Sulfur at home and may try a dose of that tonight. Here's info on Panacur:
BACKGROUND
The care of animals has always included the management of internal parasites.  As technology has progressed, the medications developed have become more and more broad in the spectrum of parasites they can eradicate. Fenbendazole is a member of the benzimidizole group of anti-parasite medications which makes it a relatively broad spectrum product.
HOW THIS MEDICATION IS USED
Fenbendazole (often abbreviated “FBZ”) is used in both large and small animals. In dogs, it is useful against roundworms, hookworms, and the more difficult to treat whipworms. It is effective against the Taenia species of tapeworm but not against the Common tapeworm Dipylidium caninum. It is also effective against giardia, a protozoan and several species of lungworm and even some flukes.
Fenbendazole is rarely required for feline use but can certainly be used safely in the cat. Fenbendazole is not approved by the FDA for use in the cat, however.
SIDE EFFECTS
Some animals experience vomiting/nausea after deworming.
INTERACTIONS WITH OTHER DRUGS
There are no significant drug interactions in small animal use.
CONCERNS AND CAUTIONS
Fenbendazole is considered safe for use in pregnancy in all species.
Treatment is necessary for three consecutive days. Treatment may require a second course depending on which parasite is being treated.

And Para-GARD:
Para-GARD is a botanical supplement designed for gastrointestinal problems. Most of the ingredients in this formula have shown antimicrobial activity and antiparasitic properties. Some ingredients also dry excessive secretions, which help alleviate the symptoms of diarrhea. This combination of actions make Para-GARD® an excellent product for acute diarrhea, and some cases of chronic diarrhea.

I'm leaning towards Panacur. If we can make it to Monday without any major concern, then my holistic vet will let us know what to do. Hopefully, this will all be over by then...we'll see...I know, aren't you just thrilled to have learned all of this? Actually, I'd be pretty shocked if you've read this far. I even think this is boring!