sick seahorse

Dear Michael:

I’m sorry to hear that your female is still having problems. The air bubbles you noticed on her tail are known as subcutaneous emphysema, a form of Gas Bubble Syndrome (GBS), which is an entirely different problem than the ulcers and tissue erosion you have been treating with antibiotics. The two disease problems — external GBS (or subcutaneous emphysema) and bacterial infection resulting in tail erosion — have completely different causes but are often associated with one another. It’s not uncommon for the open ulcers to develop as a secondary infection to subcutaneous emphysema, and it also works the way around. The stress of an active bacterial infection can sometimes cause gas bubble syndrome to develop.

You will need a different medication (Diamox, the tablet form of acetazolamide) to treat the gas bubbles than the antibiotics you have been using for the tail infection, but Diamox can be combined with antibiotic therapy so you can treat both condition simultaneously.

Diamox is a prescription med so you’ll have to get it from your Vet or perhaps your family doctor (it often used to treat glaucoma, altitude sickness and a number of other conditions in humans). Veterinarians are often unfamiliar with Diamox — it’s very much a people med and unless you find a Vet that works with fish regularly, he or she will probably never have heard of gas bubble disease or treating it with carbonic anhydrase inhibitors. Many pet owners are on very good terms with their Vets, who are accustomed to prescribing medications for animals, so it’s often best to approach your Vet first about obtaining Diamox despite the fact they may never have heard of it until you brought it to their attention. Your family doctor, of course, will be familiar with such medications but it can sometimes be difficult to get your MD to jump that final hurdle and prescribe it for a pet.

Go ahead and try your family doctor. If you can get him (or a local Veterinarian) to look at the information on GBD below it should make perfect sense to them and, hopefully, persuade them to prescribe it for you. If not, there are other options we can pursue.

Here is some information on GBD in seahorses that you can print out for your Vet or family physician that explains why carbon anhydrase inhibitors such as Diamox are useful in treating gas disease:

Gas Bubble Disease (GBD)

Your seahorse is suffering from a form of external Gas Bubble Disease known as subcutaneous emphysema. As discussed in greater detail below, these blisterlike bubbles tend to form on the most distal portion of the tail first because that is where seahorses store their fat reserves (the gas emboli that cause GBD form more readily in adipose tissue) and that is where oxygen tension is the lowest (low oxygen tension drives the following reaction to the right):

HbO2 —> Hb + O2.

Subcutaneous emphysema, or tail bubbles as they are sometimes called, can also occur on other parts of the seahorse’s body, and are fairly common on the head, especially around the eyes and on the snout. Like the other areas where GBD is prone to occur, the head is well endowed with major vessels is order to keep the vital sensory organs and above all, the brain, well supplied with oxygenated blood.

Gas Bubble Disease (GBD) is thus believed to be caused by gas emboli forming within the tissue of heavily vascularized portions of the seahorse’s anatomy — the brood pouch of males, the eye, the muscular prehensile tail — and it can take several different forms depending on where the bubbles or emboli occur. When it occurs in the brood pouch of the male, chronic pouch emphysema or bloated pouch results, leading to positive buoyancy, and this is by far the most common form of GBD. When it occurs in the capillary network behind the eye (choroid rete), Exopthalmus or Popeye results, and the eye(s) can become enormously swollen. When it affects the capillary network of the gas bladder (the rete mirabile), hyperinflation of the gas bladder occurs, resulting in positive buoyancy. When it affects the tail or snout, external gas bubbles form just beneath the skin and look like raised blisters. When intravascular emboli occur deep within the tissue and occlude blood flow, generalized edema results in the affected area. Or extravascular emboli may cause gas to build up within the coelom, often resulting in positive buoyancy and swelling or bloating of the abdominal cavity (internal GBD). If untreated, the gas bubbles worsen and the condition is fatal.

The prehensile tail of the seahorse is often affected when conditions are favorable for the formation of such gas emboli because it has a rich blood supply via the dorsal aorta and caudal vein (hence plenty of carbonic anhydrase to induce the formation of intravascular gas bubbles) and because the tail is the site where seahorses tend to store their limited fat reserves (extravascular seed nuclei or emboli that trigger GBD form most readily in adipose tissue due to the higher solubility of certain gases in lipids than in aqueous tissues)..Intravascular bubbles are seen in both the arterial and venous circulation, with vastly greater numbers detected in venous flows (venous gas emboli). The far more numerous venous bubbles are believed to first form in lipid tissues draining the veins. Lipid tissue sites possess very few nerve endings, possibly masking critical insults at first, and veins, which are thinner than arteries, appear more susceptible to extravascular gas penetration.

In seahorses, oxygenated blood is delivered to the tail via the dorsal aorta, a major artery running the length of the body below the spine, and CO2-laden water is returned via the caudal vein which runs along the inside of the tail. In your case, Michael, venous bubbles appear to have have formed in the affected area of your seahorse’s tail and led to the growth and development of extravascular gas bubbles in the adjacent tissue, producing the air bubbles (i.e., subcutaneous emphysema) you noticed around the wound.

The etiology of GBD is still poorly understood, and there are many theories as to what causes the gas emboli or micronuclei in the first place. Nitrogen gas supersaturation of the water, the unique physiology of the male’s brood pouch, inefficient degassing of CO2 in small closed-system-aquaria, low pH in the aquarium resulting in acidosis of the blood, malfunctions of the pseudobranch or the gas gland of the swimbladder, stress-related changes in blood chemistry that affect the oxygen-carrying capacity of hemoglobin, infection with gas-producing bacteria — all have been advanced as mechanisms that could trigger the formation of the gas emboli. Very likely GBD has multiple causes, but most experts now believe it is due to physical conditions in the seahorse tank rather than a pathogen.

In other words, despite its name, GBD is not a disease seahorses contract. Seahorses do not arrive with GBD, but they often develop the condition when kept in a system that exposes them to gas supersaturation, inefficient degassing of carbon dioxide, stress (especially if due to poor water quality and/or low pH), inadequate water circulation, a bacteria-laden substrate or other environmental factors conducive to the formation of gas embolisms. Not too long ago there was really not much a hobbyist could do for seahorses with GBD, but now, for the first time, there is a very promising new cure hobbyists can easily administer.

In all its various forms, Gas Bubble Syndrome is probably the most common affliction among seahorses. Public aquaria, labs, and big institutions that display Syngnathids or work with seahorses are accustomed to dealing with it and have developed several cures for GBD over the years. This includes submerging the affected seahorses at depths great enough to recompress them (> 10 feet) and cause the gas to go back into solution; using hyperbaric chambers to accomplish the same thing (the same treatment used for divers with the bends); surgical removal of the pseudobranch; and injections with carbonic anhydrase inhibitors such as Acetazolamide and Ceftazadine. Note: carbonic anhydrase is simply a zinc-containing enzyme that catalyzes the following reversible reaction, which helps change carbon dioxide into bicarbonate ion, a form of CO2 that is more easily carried in the bloodstream, or vice versa:

CO2 + H2O <—–> H2CO3 <—–> HCO3- + H+
carbon dioxide….carbonic acid…. bicarbonate ion

As long as the body’s normal equilibrium is maintained, all is well, but when imbalances drive this reaction too far in either direction, gas emboli can result. For instance, an excess of CO2 in the system will drive this reaction to the right, resulting in the accumulation of carbonic acid. When the carbonic acid builds up sufficiently, it disrupts the body’s acid-base balance and lowers the pH of the blood, producing acidosis.

The decrease in blood pH reduces the oxygen carrying capacity of certain types of hemoglobin, resulting in the release of oxygen in the blood, which eventually causes gas emboli to form in the most vascular parts of the seahorse’s body. Low pH in the aquarium can also result in acidosis, with the same outcome. And chronic stress or prolonged exertion can also cause a decrease in the blood pH, producing emboli via the same mechanism.

Likewise, imbalances which favor the exchange of bicarbonate for carbonic acid can drive this reaction too far to the left, triggering physiologic processes which liberate C02, again causing gas emboli to form in the most vascular parts of the seahorse’s body which are richest in carbon anhydrase. In either case, inhibiting this enzyme seems to prevent the formation of such gas emboli and allows the body to restore its normal equilibrium.

Unfortunately, none of the methods developed by the professionals for treating GBD are available to the average hobbyist. But it has recently been found that Diamox, the tablet form of Acetazolamide, a potent carbonic anhydrase inhibitor, is nearly as effective as the injections for treating GBD, making it the first practical cure for hobbyists to combat this dread affliction.

The Diamox is used in different ways to treat the different forms of GBD. For instance, Diamox pouch flushes are effective for treating chronic recurring pouch emphysema. On the other hand, a series of Diamox baths works better for treating external GBD (tail bubbles), and Popeye. And administering the Diamox orally is often most effective for treating internal GBD or hyperinflation of the gas bladder.

Such baths offer a safe, noninvasive treatment that has proven to be effective in numerous cases like yours. Diamox is the tablet form of the acetazolamide professionals administer to seahorses with GBD via injections. Diamox is commonly used to treat glaucoma, altitude sickness and hydrocephaly in humans, and all you need is a handful of 250 mg tablets for the treatment regimen. It’s a prescription drug, but since you only need a few tablets, you can sometimes beg a free sample from your local pharmacist or Vet; once you explain what you need it for, they are generally happy to oblige. If not, just show your Vet a copy of this letter and describe your seahorse’s symptoms, and he should be happy to write you a prescription for the Diamox.

Providing you begin the treatments early, while the seahorse is still eating, the prognosis for complete recovery is very good, especially when dealing with external bubbles. Subcutaneous emphysema is the easiest form of GBD to cure and generally responds very well to Diamox. Here are detailed instructions for the Diamox treatments developed by Tracy Warland for external GBD (tail bubbles):
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Acetazolamide Baths

The acetazolamide treatments are extremely effective in the treatment of external gas bubble disease and GBS-induced Popeye, and are helpful in treating internal GBS and hyperinflation of the swim bladder as well, especially when the affected seahorse has stopped eating. In such cases, instead of a pouch flush, a series of acetazolamide baths is used to administer the medication (Warland, 2002).

The baths should be administered in a hospital ward or quarantine tank. Acetazolamide does not appear to adversely affect biofiltration, but it should not be used in the main tank because it could be harmful to inhibit the enzymatic activity of healthy fishes. Treatments involving acetazolamide tablets are still fairly new to the hobby and the most effective dosages and methods for administering the medication are still in the process of being worked out and adjusted, largely by trail and error.

The appropriate amount of the medication to use varies with the size of the seahorse. Also, please note that the dosages given for the acetazolamide baths are correct for a treatment tank containing 8 gallons (30 liters) of saltwater. If you are using a smaller hospital tank, be sure to scale down the dosage to suit the smaller volume of water you are dealing with.

Using the tablet form of acetazolamide (250 mg), crush the required amount to a very fine powder and dissolve it thoroughly in a cup or two of saltwater. There will usually be a slight residue that will not dissolve in saltwater at the normal alkaline pH (8.0-8.4) of seawater (Warland, 2002). That’s perfectly normal. Just add the solution to your isolation tank, minus the residue, of course, at Tracy’s recommended dosage:

RECOMMENDED DOSAGE

Type of Seahorse _____Size of Seahorse ____Acetazolamide (250-mg)
Mini……………………….up to 3 inches……………1/16 tablet per bath
Small species…………. 3 to 5 inches…………….1/8 tablet per bath
Medium species………..5 to 8 inches…………….1/4 tablet per bath
Large species……………> 8 inches……………….1/2 tablet per bath

As you can see, the usual starting dosage for a seahorse size of your 8 inchers is 1/4 of a 250 mg tablet per 8 gallons of water, but treatments with Diamox have since become much more refined, and most people now find that a considerably larger starting dose is more effective in relieving gas bubble disease. For example, most people now recommend one full 250 mg tablet of Diamox for 8 gallons when bathing a seahorse the size of yours, and that’s the dosage I suggest you use in this case.

Place the affected seahorse in the treatment tank as soon as first dose of medication has been added. After 24 hours, perform a 100% water change in the hospital tank using premixed water that you’ve carefully aerated and adjusted to be same temperature, pH and salinity. Add a second dose of newly mixed acetazolamide and reintroduce the ailing seahorse to the treatment tank. After a further 24 hours, do another 100% water change and repeat the entire procedure until a total of three treatments have been given. About 24 hours after the third and final dose of acetazolamide has been added to the newly changed saltwater, the medication will have lost its effectiveness and the patient can be returned directly to the main seahorse tank to speed its recovery along.

The same 3-day regimen of acetazolamide baths is the preferred treatment for eternal GBS, and Popeye or Exophthalmia as well as internal GBS and hyperinflation of the gas bladder when the seahorse is no longer eating in the medication cannot be given orally..

However, in the case of external GBS or subcutaneous emphysema, also often referred to as tail bubbles, it is usually recommended that the external blisterlike bubbles be lanced prior to the first of the baths (Warland, 2002). This is not strictly necessary and should not be done when the bubbles are located on the head or snout. The bubbles (subcutaneous emphysema) will gradually deflate and disappear on their own as the medication takes affect. Lancing the bubbles does hasten the healing process, and it is important to release the air from any bubbles when they are so large and/or extensive that they cause buoyancy problems or otherwise interfere with the seahorse’s mobility.

Use a fine sterile needle for this and approach each bubble from the side at a very shallow angle, taking extreme care to pierce only the surface of the bubble, not the underlying skin of the tail (Warland, 2002). Once the bubble surface has been pierced, apply gentle pressure to the bubble to deflate it and release any air or fluid inside.

As with pouch flushes, one of the side affects of acetazolamide baths is loss of appetite. Try to keep the affected seahorse eating by plying it with its favorite live foods during and after treatment, until it has fully recovered.

This 3-day regimen of baths is extremely effective in curing external GBS. They also work fairly well in clearing up Popeye. (Exopthalmia can be result from several different causes, and acetazolamide is only effective when GBS is the cause). Internal GBS is generally more difficult to cure, particularly if the seahorse has stopped eating and the acetazolamide cannot be administered orally. I believe this is because internal GBS is difficult to diagnosis until it is well advanced and emboli have already done serious organ damage.

In stubborn cases, the regimen of acetazolamide baths may have to be repeated a second time. Don’t hesitate to increase the dosage if necessary to clear up the symptoms.

Best of luck resolving your female’s tale problems, Michael.

Respectfully,
Pete Giwojna