Firstly, if you’re continuing to give penicillin shots, ask for a larger gauge needle — you should not have to go through clogs, on top of the stress of giving a rabbit a shot. I had a similar scenario where it kept clogging and it was nothing I could do to prevent it because it was a vet assistant’s mistake of giving me too small needles (that I had no idea was a thing; I thought I was just doing something wrong).

Was there any check of his teeth throughout this time? Fur loss around the mouth, in addition to what has already been checked/treated for, can also be a result of dental concerns. Essentially, a rabbit will start to drool/dribble a bit because their mouth begins producing excessive saliva to lubricate the mouth as it gets uncomfortable. Drooling leads to fur loss, irritation, etc..

There is a blood test to check for the antibodies which fight the syphilis infection. As with any test, it can come up as a false positive, but if you are unsure whether to proceed with pen-g, you can see if you can have that blood test done. Notably, the test won’t be reliable in telling you if the syphilis is treated, as the antibodies will stick around even if the infection isn’t there anymore.

Can you post pictures of these new spots you’re mentioning? It sounds like they are on the back, but I don’t think that was explicitly stated in your post. It is definitely possible to have scabs and irritation from shots. If they are wounds from his shots and they are irritated, it’s not the end of the world and they can be treated!

There is an oral medication called azithromycin which has been shown to treat syphilis in rabbits, so if you are weary/your rabbit is reacting poorly to shots, perhaps you can explore that avenue with your vet instead. My rabbit went through both pen-g shots and oral azithromycin for his syphilis (doing both at once is not standard; we had suspicions based on his past medical history that pen-g would not be enough/effective on his syphilis).

Also, at this point, does his chin seem to be irritated/scabbing to a degree that’s getting worse? It would not cure the scabs if they are syphilis-related, but silver sulfadizine, if applied conservatively, can help soothe and prevent infections from the scabbing going on. I say applied conservatively because it’s a lotion/cream, so if you get it all over the perimeter fur, it can gunk things up and make it seem more hectic in the area than it actually is.

Has the vet for sure ruled out ringworm?  The balding around the mouth looks a lot like ringworm to me. We also had a bun at the rescue with an upper respiratory infection that lead to baldness around the mouth that looked just like that. When I’ve seen syphillis, it looks more crusty and scabby, but maybe it looked like that before and has healed a bit?

And scabs around injection sites can happen with long term injections, esp if some of the injections were accidentally in between skin layers instead of under the skin.

Since there are lots of things it could be, I do think the vet is the best person to try to sort it out. If you aren’t confident in your vet it would be good to get a second opinion. All of the symptoms could be related, or you could be dealing with separate issues (or a main issue, with side effects from trying to treat the main issue), so a fresh set of eyes might help.

It’s important not to panic though! Sometimes treatment of these types of issues can take a long time with some hiccups in the process.

The pictures show a scab on his back. This is definitely from the repeated injections. As for around his mouth… I don’t see any scabs or flakes. Could it be that the injections are working and the scabs fell off? There won’t be any fur where the scabs fell off. It takes a while for the fur to grow back once the skin is healthy again.

The mouth/chin area does look healthy– the fur will take awhile to grow in, but it looks very promising! It reminds me exactly of what my Wick went through:

My rabbit had both ringworm and syphilis, so we did treat for both. At this time ^^^ we were only treating ringworm (did not think of syphilis at the time), so we did ringworm treatment effectively. That being said, if the fur loss is not expanding anymore, that’s a good sign.

Notably, my Wick originally had ringworm which we treated but then it kept “coming back”… that’s when we had suspicions that somewhere along the line, we were no longer treating ringworm, but syphilis.

The mouth-only-symptoms cases of syphilis are considered atypical. Wick’s vet at the time said they are increasing in prevalence, anecdotally. I imagine ringworm and this atypical form of syphilis can be highly conflated and related. For example, all the nastiness from fighting and having syphilis likely opens the way for ringworm to take root.

http://www.medirabbit.com/EN/Skin_diseases/Bacterial/Syphilis.htm

Medirabbit does a short mention of the atypical cases. They do not mention azithromycin as a treatment, but it was something one of Wick’s past vets went through, and there are studies comparing it to pen g: https://academic.oup.com/jac/article-abstract/25/suppl_A/91/697854 , https://journals.lww.com/stdjournal/fulltext/2002/08000/a_randomized,_comparative_pilot_study_of.10.aspx?casa_token=9xhBrr8gHTMAAAAA:PtkW3t1RwlRF2gGNT_ZwmqNnrwfcYp8I0N4II4t_uLOj3FJMn6Rl6vwW3Ghm4skV2Ud8t5Q0lnfi4SLobftdybs

Thank you very much for this report! This is so very helpful for other bun owners.

Fingers crossed he just need a couple of weeks more of PenG.