I just spent the last 7 months fighting bordetella in my guinea pig, so I have become a bit of an expert. While it can technically jump between species, it is very very unlikely that it will jump from dog to guinea pig. Usually, guinea pigs only contract it from rabbits or other piggies.
Definitely keep an eye on their weight, but the first symptom for me was coughing. It was just one cough, very sporadically. I took him to the vet, but they couldn't find anything wrong with him. It was months before the cough became bad enough that they actually started treatment, because they kept telling me it was allergies. Turns out my cavvy savvy vet wasn't very savvy, so he was receiving the wrong dose of medication until I switched to a new vet. By that time, the infection became very persistent.
It took us 7 months, thousands of dollars, countless antibiotics before we finally beat the infection. We ended up having to build him a chamber to nebulize an antibiotic penetrate the pneumonia he developed. So, my advice to you is if you hear ONE cough, take them in. But, like I said, it is very very uncommon for bordetella to jump from dogs to piggies so you are probably ok. I've had 2 cats in the house with my sick pig, and they are totally healthy.
