SEIZURES, CONVULSIONS AND TREMORS IN REPTILES
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SEIZURES, CONVULSIONS AND TREMORS IN REPTILES

by
Edward M. Craft

Seizures, convulsions and tremors are symptoms of a very serious underlying illness or traumatic injury. In some cases the underlying condition may be corrected, while in others the condition may be terminal. For this reason it is vital that an owner understand the importance of seeking proper diagnosis and treatment when any of these symptoms are presented in a reptile. The first step is to understand the differences between seizures, convulsions and tremors. While there is little that an owner can do to determine the underlying cause of any one of these symptom and while all may appear to be generally the same, there are subtle differences and by knowing which one that your reptile is having you may help to aid in the proper and timely diagnosis of the underlying illness. This article will attempt to address and identify the differences between a seizure, convulsion and tremors while discussing some of the potential causes for them. This article will also briefly discuss the proper methods for diagnosing the cause of these symptoms, but the actual diagnosis should be left up to a veterinarian who has experience in working with reptiles so we will not go into any great detail on diagnosis here in this article. The purpose of this article is to provide the reptile owner with a better understanding of these symptoms and their causes in order to learn ways of preventing some of these condition in their own animals. When it comes to caring for your reptile(s) health it is best to approach illness and injuries from the standpoint of a warrior, "knowing your enemy is the key to defeating him". Thus knowing the cause, or causes, of an illness or injury is the key to preventing it.

There is little that is truly known and understood about any of these symptoms in any species, much less in reptiles, however what is known is there are differences in the symptoms themselves. Seizures are the most complicated of the three symptoms. A seizure simply involves a loss of consciousness and results from abnormally excessive synchronous electrical discharges from a group of neurons in the brain. This type of seizure is known as "Nonconvulsive". This means that there is a problem in the wiring within the brain. For one reason or another the electrical activity in the brain is malfunctioning leading to a loss of consciousness. This may be caused by a genetic disorder, as the result of a traumatic injury or as a side effect of an illness that is interfering with the brains ability to function normally. When most of us hear the term seizure the first word that pops into our head is epilepsy. This is a term that is attributed to a seizure when they become recurrent and is not an illness in and of itself, but rather a label for this particular type of seizure. In most cases the underlying cause of these recurrent seizures is never determined and rather than say that a cause for the seizure cannot be determined they are labeled as epileptic. A common mistake that is often made by less than experienced individuals and veterinarians is the "playing dead" behavior of the hognosed snakes (Heterodon. spp.). This behavior is sometimes mistaken by an inexperienced individual as a seizure, when in reality it is normal healthy behavior for this species. Inclusion Body Disease Virus (IBDV), commonly known as "Star Gazerís Disease", has been identified as one cause of seizures and other neurologic involvement in some species. It is NOT an actual disease by itself and as the name suggests it is suspected that is viral in nature. This disorder is often confused with other conditions, like parasitic, fungal or bacterial infections that effect the nervous system. All of these conditions may present with symptoms that resemble those of IBDV. These symptoms include, but are not limited to seizures, paralysis, head tremors, disorientation, and inability to right itself and regurgitation. The species that appears to be most effected by this condition are Red-tailed boas (Boa c. constrictor). Despite the fact that Red-tailed boas are the most commonly effected species it does occur in many other species as well, in fact up until the mid 80's this disease was primarily seen in Burmese Pythons (Python mourus bivittatus). This increase in the presence of the disease in Red-tailed boas may be a result of the increased popularity of the species in captivity.

It has been suspected that the snake mite, (Ophionyssus natricis), may be the method of transmission for this virus. The exact route of transmission is currently unknown, but studies are currently underway to isolate this virus and discover both the route of transmission and effect a treatment. Diagnosis of this disorder is extremely difficult since little is known about it and more research is required, it is most often diagnosis after death. The only thing that is a given when this condition is present is that the prognosis is always guarded at best and more than likely grave as a result of the fact that there does not exist a recommended treatment and any attempt to treat an animal with these symptoms is antidotal.

Convulsions are a particular type of seizure. It is these convulsions that most of us associate with seizures. Convulsions are a seizure (loss of consciousness) with accompanying involuntary motor activity. Convulsions are often an indicator of a more complex illness or injury. These types of seizures are best known as grand mal seizures and usually effect both sides of the brain. This type of seizure in a reptile often indicates an extremely serious condition. Convulsive seizures may often occur as the result of exposure to a toxic substance, such as ingesting harmful vapors or plants. This type of seizure is commonly seen in iguanas and other herbivorous lizards that are housed in enclosures with live plants that an owner assumes are harmless. This is just one more reason for an owner to keep accurate records as to housing and husbandry of their animals and for a veterinarian to obtain a complete history on a reptile, to include housing and husbandry information. As is the case with any type of seizure they may be the result of a traumatic injury in which damage to the brain has occurred. Retroviruses can often result in an encephalitis or meningitis which may have an effect on the brain, causing this type of seizure.

Tremors are an entirely different type of symptom altogether. Tremors are often commonly called "twitching" and are regular rhythmic movements of any part, or parts, of the body. Tremors are often associated with the cerebellum of the brain in most vertebrates, but extremely little is know about the reptile brain and it is only assumed that tremors are associated with this part of the reptile brain. This is based on the assumption that the reptile brain is similar to that of other vertebrates. In most cases involving reptiles, tremors have most often been associated with a metabolic disorder, such as hypocalcemia and primarily involve the muscles rather than the brain. If diagnosed and treated early the chances of recovery with these types of tremors are improved. Treatment of any underlying metabolic disorder will also include a correction of the animalís diet. Once the diet has been corrected and the disorder has been treated the tremors should cease. If the tremors continue, than they are more than likely related to some type of neurological involvement and not the result of a metabolic disorder. This is one area where experience can play a key role in determining whether tremors are muscular or neurological in nature. When these tremors are neurological in nature the animal will more than likely exhibit seizures as well. When they are muscular in nature the animal will most likely exhibit signs of some type of metabolic disorder, such as a soft lower jaw and diarrhea. Other causes of muscular tremors in reptiles include deficiencies of glucose, thiamin and biotin. All of these causes are not associated with neurological tremors, but are usually muscular in nature and have the best chance for a successful treatment. Proper diagnosis is vital to determining whether tremors are muscular or neurologic in nature and require blood testing. If there are no evident nutritional deficiencies it may be assumed that the tremors are neurologic and nature and further diagnosis will be required to attempt to determine the underlying cause.

Throughout this article I have attempted to stress the importance of proper veterinary diagnosis and treatment. The importance of this should become evident here because one of the most commonly seen causes of seizures in reptiles is related to intoxication due to improperly administered medications, such as ivermectin. This often occurs when an owner or an inexperienced veterinarian attempts to deworm a reptile with the immiticide called ivermectin. The use of this drug in reptiles has increased over the last five years and along with this increase has come an increase in the number of intoxication related cases of seizures in reptiles. The use of ivermectin in reptiles is a very sensitive subject and has often come under fire by some members of the herpetological and veterinary communities, however its full effects on all species is not yet known. It is, however known that it may be very useful as a deworming agent when administered properly and in the proper dose. The correct dose for a particular reptile varies greatly among the various species and a ball python dose may not be the same as it is for a green iguana. When seizures are present in a particular reptile, a history of any medications administered by an owner should be provided to the veterinarian.

Another type of toxic related seizure is that caused by substances within the reptiles water supply. It may never be proved that a particular animalís seizures are directly related to these substances, but it would be wise of any owner to always consider any and/or all possibilities when attempting to identify the cause of such a vague symptom as seizures. Water quality is a consideration for all species, not just aquatic and semi-aquatic species. Water may contain many different mineral and chemicals that may or may not effect the reptile's overall health. For instance, some water sources contain Fluoride in place of sodium salts. Its effects on mammals are known to be dangerous if improperly dosed, but its effects on reptiles are currently undetermined. Hard water contains bicarbonates, calcium and magnesium, all of which are safe in reptiles. In soft water the calcium and magnesium are replaced by sodium. This is not a problem for most reptiles, but may present a problem for reptiles that are adversely effected by excess salts. One other consideration is the possible toxic effects caused by the metals in water that has passed through rusted or old pipes. It is a known fact that metals can have a toxic effect on any animal and has been suspected of being related to toxic related seizures of reptiles in some cases.

The bottom line concerning seizures, convulsions and tremors in reptiles is that very little is truly known about them and in most cases the outcome for the effected animal is usually very grave. For this reason it is vital that any neurologic symptom be identified by an owner as soon as possible. The owner should also make note of whether the seizure acute and sudden, such as following an accident or injury, or has it been chronic and progressed slowly, such as the result of a previous or pre-existing illness. The owner should also pay close attention to their pet and maintain good notes regarding feeding, the animalís environment, and any medications administered by the owner, regardless of whether they were prescribed by a veterinarian or bought over the counter by the owner. Knowing these facts may save you and your reptile a lot of trouble and expense in attempting to diagnose the underlying cause of these types of neurologic symptoms.

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All rights reserved by Edward M. Craft. Printed in the United States of America. Original Edition 1997