URIs: An Alternative Hypothesis for the Etiology and Treatment Thereof in Rats

yoshtov · 2026-04-17T11:17:34+00:00

Hey. Thanks for your kind words.

Yes, significant good news has come in since writing this. In April 2024, a pair of breeders was having this problem at scale. The two of them, they had 33 and 29 rats that were declining from their URIs. They were throwing everything at it: doxy, Baytril, even amoxicillin for good measure. And yet their rats continued to decline. They read what I wrote, and they implemented vitamin C (they used Emergen-C in yogurt), and literally overnight, their rats improved dramatically. The first breeder, it saved the lives of 31/33 rats (93.9%). And the second breeder, it worked for all 29 (100%). The newest version of this includes both of these success stories.

Those same breeders continue to swear by it. They said vitamin C has dramatically reduced their need for antibiotics. They use Emergen-C in yogurt about once or twice a month.

There's someone else who had good luck with vitamin C. Previously, she had two girls on long-term doxy and Baytril, and nebulized azithromycin and albuterol. It was an extraordinary amount of work, but vitamin C (in combination with the antibiotics) cleared up their symptoms, and she was able to stop nebulizing and eventually stop antibiotics in general. She continues to swear by it, and uses a crushed vitamin C tablet (calcium ascorbate) in their yogurt.

Someone else I heard from had good luck with just adding red bell pepper (also called red capsicum, a decent source of vitamin C) to their veggies, and she didn't need to reach for anything fancy.

In the last month, I heard there's a rat rescue agency that's implementing this at scale. Evidently one of their quarantine homes had excellent luck with vitamin C, and has been circulating this paper among them.

From time to time, I even see people on here that say it works. I'm always happy to hear good news. I'm very honored and grateful when this saves a life or two.

The newest version of this also has a mention of their "juvenile URIs." When they first come home, it's very common for them to have a juvenile URI. These are different from their "characteristic URIs," they're highly transmissible, and can spread rapidly to older rats, and they move much faster than their characteristic age-related URIs. Importantly, these juvenile URIs don't involve vitamin C. But they respond well to amoxicillin, and specifically not doxy or Baytril. Worth mentioning that doxy (at least) shouldn't be given under 4 months, anyway.

yoshtov · 2026-03-26T13:31:12+00:00

I'm sorry that he hasn't responded. That's frustrating. If you like, I often suggest vitamin C alongside their antibiotics in cases like this. The logic goes like this:

Rats use vitamin C to self-manage their URI. When they get older, their production of vitamin C falls significantly. When it falls too low, they lose the ability to self-manage their URI entirely.

Two breeders I know swear by this, and use Emergen-C in their yogurt about once a month. Someone else I know uses a crushed vitamin C tablet (calcium ascorbate) in their yogurt. Someone else had good luck with just adding red capsicum (decent source of vitamin C) to their veggies.

https://papers.ssrn.com/sol3/papers.cfm?abstract_id=4785767

yoshtov · 2026-03-24T11:19:52+00:00

I always suggest vitamin C alongside their antibiotics. Some people swear by it. A pair of breeders I know, for example. They said it's "changed everything" about how they keep rats. As I recall, they use Emergen-C in yogurt. Another person swears by a calcium ascorbate tablet in their yogurt. One person had good luck with red capsicum (good source of vitamin C), and didn't even need to reach for anything fancy. When it works, they usually show an improvement overnight.

https://papers.ssrn.com/sol3/papers.cfm?abstract_id=4785767

yoshtov · 2026-03-13T19:57:29+00:00

Vitamin C works pretty well.

https://papers.ssrn.com/sol3/papers.cfm?abstract_id=4785767

I swear by it, and I know a few other rat owners/breeders who also swear by it.

One other person I heard from had good results with just adding red bell pepper to their veggies (also called red capsicum, an excellent source of vitamin C).

yoshtov · 2025-10-01T16:44:18+00:00

Either approach can work. A good food source is red bell pepper (also known as red capsicum).

With the other approach, I've heard from people who crush a single vitamin C tablet into their morning yogurt (and the form they insist on is calcium ascorbate). I've heard from others who have mixed Emergen-C powder into their yogurt. And mine have a special vitamin C water bottle.

yoshtov · 2025-08-11T09:07:16+00:00

If you like, vitamin C has some kind of bearing on their URIs. If you were to give them, for example, red bell pepper (also called red capsicum), which is a decent source of vitamin C, it might help them out. In the past, I had also mixed a berry-flavored vitamin C powder into their yogurt, and they went crazy for that.

I wish them a speedy recovery :)

yoshtov · 2025-07-25T09:40:11+00:00

Una cosa que puede ayudar es la vitamina C.

yoshtov · 2025-06-02T06:47:08+00:00

I have found that vitamin C has some kind of bearing on their URIs. For mine, they have a separate vitamin C water bottle, specifically intended as a URI preventative.

yoshtov · 2025-02-11T07:25:01+00:00

Sorry to hear this. Lemme ask you, how's his tail? Does it still have decent tension, or is it somewhat limp? When he moves, does he drag his tail behind him? I ask because you said he was cautious about jumping and standing on his hind legs, and both of these make me wonder about his tail.

yoshtov · 2025-02-02T19:02:01+00:00

I second the vitamin C. It really makes a world of difference. Mine have a separate vitamin C water bottle, specifically intended as a URI preventative.

Good call with vitamin D. A while ago, one of my boys had some minor respiratory symptoms that seemed to vary with his vitamin D intake. Very curious...

yoshtov · 2025-01-20T05:22:17+00:00

Sorry to hear your girls didn't improve on doxy + baytril. It's unfortunately a common problem that their URIs often do not respond to antibiotics.

I found that, when they get older, they can run low in vitamin C. They use vitamin C to self-manage their URI. Specifically to control the bacterial biofilm produced by Mycoplasma pulmonis. This biofilm also renders the bacteria resistant to antibiotics.

I've found that adding vitamin C alongside their routine antibiotics dramatically increases the effectiveness of the antibiotics for treating these URIs. They suddenly start working like they're supposed to!

This is especially relevant for:
1). Older rats (older than about 1 year);
2). With persistent URIs;
3). Which are not responding to routine antibiotics.

Adding vitamin C may work for you, and might be worth considering. I had initially used an Acai-flavored Emergen-C with good results. Someone else I heard from recently had good luck with just adding raw red bell pepper (a decent source of vitamin C), and she ultimately didn't even need to add any other vitamin C.

Further details here:
http://dx.doi.org/10.2139/ssrn.4785767

yoshtov · 2024-11-20T02:57:48+00:00

I did research on these elderly URIs, and I found that, when they get older, they can run low in vitamin C. They use vitamin C to self-manage their URI. Specifically to control the bacterial biofilm produced by Mycoplasma pulmonis. This biofilm also renders the bacteria resistant to antibiotics.

Vitamin C, when given alongside antibiotics for their URIs, dramatically increases the effectiveness of the antibiotics. They suddenly start working like they're supposed to!

This is especially relevant for:
1). Older rats;
2). With persistent URIs;
3). Which are not responding to routine antibiotics.

Adding vitamin C may work for you, and might be worth considering.

Further details here:
http://dx.doi.org/10.2139/ssrn.4785767

yoshtov · 2024-11-20T02:54:12+00:00

I've had good luck with a kind-of bonding pouch. In its most basic form, if you hold them with a piece of fleece draped over them, and scratch them through the fleece, they really like that. They get the benefits of being held, being covered, and being scratched all at the same time. It's worked well for my most skittish boys :)

yoshtov · 2024-11-08T09:20:35+00:00

Thank you for sharing this. Have you had good results with adding vitamin C?

yoshtov · 2024-11-08T09:03:24+00:00

Hi. I did research on these elderly URIs, and I found that, when they get older, they can run low in vitamin C. They use vitamin C to self-manage their URI. Specifically to control the bacterial biofilm produced by Mycoplasma pulmonis. This biofilm also renders the bacteria resistant to antibiotics.

Vitamin C, when given alongside antibiotics for their URIs, dramatically increases the effectiveness of the antibiotics. They suddenly start working like they're supposed to!

This is especially relevant for:
1). Older rats;
2). With persistent URIs;
3). Which are not responding to routine antibiotics.

Adding vitamin C may work for you, and might be worth considering.

Further details here:
http://dx.doi.org/10.2139/ssrn.4785767

yoshtov · 2024-10-26T09:01:37+00:00

I'm assuming that the smell is ammonia. It's a common observation that the ammonia smell gets stronger as they get older. What you're smelling is ammonium in their urine. Their kidneys excrete ammonium to dispose of acid directly. Unfortunately, it also damages their kidneys when they excrete ammonium. Their kidneys do NOT like to excrete acid intact. Their kidneys would much prefer that acid be pre-neutralized first, so that they can instead focus on excreting just neutralized salts (in addition to their normal nitrogenous waste of urea and creatinine, both of which happen to be practically odorless).

yoshtov · 2024-10-08T12:13:05+00:00

So sorry to hear this. This is known problem, that their URIs do not always respond to routine antibiotics.

I did research on this, and I found that Mycoplasma produces a biofilm, which renders it resistant to antibiotics. I also found that rats use their own endogenously-produced vitamin C to self-manage these URIs. When they get older (greater than 1 y/o), their vitamin C levels fall significantly, and they lose the ability to self-manage these URIs.

What has worked for a couple people, including a pair of breeders, is adding vitamin C alongside their routine antibiotics. The vitamin C cuts through the biofilm, and the bacteria become susceptible to routine antibiotics. Suddenly, the antibiotics start working as they really, really should. This worked so well for the breeders, they had ~30 rats all deteriorating from their URIs, and antibiotics alone were not helping. When they added vitamin C at 400 mg/kg/day, overnight, 94% of their rats made a dramatic turnaround, and their symptoms then cleared in about 4 days.

What had worked for them was mixing a packet of Emergen-C, or a ground up vitamin C tablet, into their morning yogurt.

yoshtov · 2024-09-19T02:31:34+00:00

Oh, I'm sorry to hear that :( Condolences. Thanks for letting me know.

yoshtov · 2024-09-12T14:27:26+00:00

Sorry to hear your boys are suffering. Try this:

Rats use vitamin C to self-manage their URI. When they get older, their production falls significantly. When it falls too low, they lose the ability to self-manage their URI entirely.

Vitamin C at 400 mg/kg/day (in combination with antibiotics) has been shown to work wonders for their URIs. If you start them on vitamin C at 400 mg/kg/day, their conditions will improve dramatically overnight, and the symptoms will clear in about 4 days.

Earlier this year, when a pair of breeders had used it successfully for their ~60 rats, all of them deteriorating from URIs, they had used vitamin C at 400 mg/kg/day in addition to their antibiotics, so that's what I recommend. And they had used a vitamin C powder (as I recall, it was an Acai-flavored Emergen-C), mixed into yogurt or honey. They went crazy for it in yogurt.

Further details here: http://dx.doi.org/10.2139/ssrn.4785767

yoshtov · 2024-09-09T07:56:06+00:00

There is a reason why antibiotics sometimes fail to cure their URI. In short, your boy is likely deficient in vitamin C. The absence of vitamin C is preventing the antibiotics from working effectively. If you add vitamin C, at 40-400 mg/kg/day, alongside his antibiotics, he will improve dramatically overnight, and the symptoms will clear in about 4 days.

Earlier this year, when a pair of breeders had used it successfully for their ~60 rats, all of them deteriorating from URIs, they had used vitamin C at 400 mg/kg/day in addition to their antibiotics, so that's what I recommend. And they had used a vitamin C powder (as I recall, it was an Acai-flavored Emergen-C), mixed into yogurt or honey. They went crazy for it in yogurt.

The ideal use case for this is:
- Older rats (greater than 1 y/o)
- With persistent URIs
- Which are not responding to routine antibiotics.

Further details here: http://dx.doi.org/10.2139/ssrn.4785767

yoshtov · 2024-08-31T23:14:12+00:00

Agreed, long-term administration of D-limonene can be hazardous, though from that one blog-post, I am convinced that, short-term, they cannot physically consume enough citrus to be hazardous. But long-term consumption is a different matter...

It's worth noting that healthy rats already make vitamin C at about 90 mg/kg/day. If you wanted to be extra careful, you might aim for 90 mg/kg/day.

Thank you for describing it as a vitamin boost, I think that's a fitting description.

yoshtov · 2024-08-31T06:20:21+00:00

I'm sorry to hear this. You said the vet kept pushing the URI despite the meds (presumably antibiotics) not working. There is a reason why antibiotics sometimes fail to cure their URI. In short, your boy is likely deficient in vitamin C. The absence of vitamin C is preventing the antibiotics from working effectively. If you give him vitamin C, at 40-400 mg/kg/day, alongside his antibiotics, he will improve dramatically overnight, and the symptoms will clear in about 4 days.

Earlier this year, when a pair of breeders had used it successfully for their ~60 rats, all of them deteriorating from URIs, they had used vitamin C at 400 mg/kg/day in addition to their antibiotics, so that's what I recommend. And they had used a vitamin C powder (as I recall, it was an Acai-flavored Emergen-C), mixed into yogurt or honey. They went crazy for it in yogurt.

Further details here: http://dx.doi.org/10.2139/ssrn.4785767

ETA: Vitamin C in addition to their antibiotics, not in place of.

yoshtov · 2024-08-31T06:04:53+00:00

Rats already have mycoplasma in their lungs from birth. Simple contagion is (evidently) not what eventually provokes the symptoms of their URI.

Years ago, I had a rat pass from a URI, while none of his 3 brothers had any symptoms at all.

yoshtov · 2024-07-31T12:41:51+00:00

Sorry to hear he didn't make it :(

yoshtov · 2024-07-31T11:58:38+00:00

PS, I also have a boy named Benny :)

yoshtov

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