It’s only a basic outline, and doesn’t cover all potential health problems. You will want to consult a general reference on snake health. Fortunately, there’s a good one out there. You should immediately go and buy a copy of What’s Wrong with My Snake? by John and Roxanne Rossi: you’ll learn how to avoid potential problems and when and when not to take your snake to a qualified veterinarian who has experience with reptiles.
Speaking of which, before we go on, a disclaimer: let me point out that I’m not a veterinarian; I’m just a snake keeper who’s encountered a lot of the problems set out here. I do my best to ensure everything on this page (and on this website) is accurate, but I can’t promise you that I’m not wrong. Not only that, but you may encounter something totally different from my experience that I’ve never seen before.
The most serious health problem faced by garter snakes is internal parasites. Because of their diet, garter snakes are more prone to internal parasites than other snakes are. Earthworms, fish and amphibians are all potential carriers, but wild-caught amphibians appear to be the worst. Live fish are also frequently the source of persistent parasitic infections.
Infections can involve microorganisms (protozoan, bacteria, viruses), but roundworms, tapeworms and pinworms are the most likely culprits; they’re devastating when they’ve burrowed into your snake’s lung. They can also be extremely difficult to detect, living — and growing — in your snake’s lung for years with no sign that anything is wrong.
Small lumps along the snake’s body that appear to be just under the skin may be evidence of a worm infestation. A veterinarian should be able to remove it by making an incision and pulling the worm out. Now that may sound serious, but there is a bright side: it means that the worm has migrated from the lung. A worm living in a snake’s lung is next to impossible to remove surgically without killing the snake. Deworming medication won’t help at that stage: the only thing worse than a worm living in a snake’s lung is a dead worm in that lung.
(This, at least, was what I was told when my vet found a one-foot worm living in the lung of my two-foot male Wandering Garter Snake. He didn’t make it.)
Other symptoms to look out for include a swelling around the lung (the lung is inflamed as a result of the worm’s presence) and a hollow popping sound as the snake breathes.
Unfortunately, sometimes there are no symptoms at all. Wild garter snakes frequently have a heavy parasite load and garters can endure a worm infestation for years with no sign that anything is wrong. The interval between the point of infection — a particularly bad batch of feeder fish — and the first sign that anything is wrong can be very long indeed, as I myself discovered when some of my garter snakes started dying several years after one such bad batch of fish.
Sometimes garter snakes suddenly die in captivity for no apparent reason, and some keepers have been calling that “sudden garter snake death syndrome.” While I haven’t been able to definitively confirm this, I’m fairly certain, based on my own experience, that these deaths were because of parasites.
So what can be done? De-worming medications — the same stuff used with other animals — have been used, though in my experience some infections have been resistant to even multiple treatments. The parasites just keep coming back. Some keepers de-worm their snakes prophylactically on a regular basis, just to be on the safe side.
But prevention is always better than treatment. Because freezing food for 30 days destroys parasites, frozen food is the best option, if your snake will take it. (Snakes that refuse to take anything but live food are therefore at much higher risk of infection.) This is another reason why frozen/thawed mice make such good snake food. But freezing would have the same benefits for fish and other food items, if your snake will accept them thawed instead of live.
Thiamin (Vitamin B1) Deficiency
Fish are risky for another reason. Some kinds of fish contain an enzyme called thiaminase, which breaks down thiamin (vitamin B1). Garter snakes fed an exclusive diet of these fish — such as some bait minnows, alewives, and other oily fish — can develop a thiamin deficiency. Symptoms include a loss of coordination and motor control as well as violent convulsions.
It’s fatal if nothing is done about it, but you’ll have plenty of warning, and it’s easily treatable.
First, get some thiamin into the snake. A vet can administer an injection, or you can feed (or force-feed) the snake a high-B1 diet (cod liver oil and strips of liver were recommended to me once). And second, change the diet to something that does not contain thiaminase. Mice certainly won’t have this problem, but there are lots of fish out there that don’t have thiaminase. I’ve personally encountered thiaminase with frozen bait minnows; on the other hand, commercially available saltwater whitefish (ocean perch is good, cheap, and available in grocery stores) and members of the salmonid family (salmon, trout, char) seem to be safe.
It does not matter whether the fish is live or frozen: freezing the fish does not create or destroy the thiaminase. Adding powdered vitamin B1 to fish with thiaminase doesn’t help either; the thiaminase will break that down, too.
A common misconception among beginning garter snake keepers is that their snakes should be kept in moist, if not outright semi-aquatic conditions. Garter snakes aren’t aquatic; it’s their prey that’s aquatic. They don’t need to swim; a water dish large enough for the snake to curl up in is enough. The cage needs to be kept dry.
Snakes kept in too-moist conditions can develop blister disease, which will look like white puffy sores on the snake’s body. Keep the snake in drier conditions (see Housing) and apply an antibiotic ointment, such as Neosporin or Polysporin, to the blisters.
Snakes sometimes have shedding problems, but garter snakes appear to suffer from this much less often than other species; it seems that their skins are somewhat thicker. Even so, shedding problems can occur, and the snake may have pieces of old skin stuck to it.
The biggest problem is when the eyecaps or tail tip is left unshed: this can lead to blindness in the case of eyecaps and a stubbed tail in the case of the tail tip if left untreated, especially over multiple sheds.
Sometimes shedding problems are a symptom of some other health problem: a sick snake doesn’t necessarily shed its skin very well. But most of the time this happens because the humidity is too low. One way to deal with it is to add a dampened cloth to the cage and let the snake curl up in it. This should help soften the skin. The snake should be able to shed normally after that. You can assist the snake yourself: merely restrain the old skin and let the snake crawl out of it. Tweezers should not be used to remove eyecaps with snakes this small; better to pull it off gently with your fingers, if you’re nimble enough. Be patient, and be very careful. It once took me 40 minutes to take an unshed eyecap from a water snake; it was worth it to make sure I didn’t hurt the snake.
If the problem persists, add a humidity box to the cage, or increase the room’s humidity with a humidifier or a vaporizer, and the problem should go away next time.
A nuisance regardless of the species kept, snake mites are the bane of almost every snake keeper. They can be extremely difficult to get rid of, especially if you have more than one or two snakes. The best advice I can give you is to read Melissa Kaplan’s excellent page on mites.