Chihuahua Facts

The Chihuahua Health Facts

Reverse Sneeze

Occasional bouts of sneezing, snorting, honking and wheezing are not unusual in chihuahuas, and is sometimes called a "reverse sneeze". This is usually caused by a elongated soft palate that is thought to become temporarily misaligned. It is a common trait in toy breeds. Pulling hard on a leash, drinking too fast or getting overly excited can lead to an episode of reverse sneezing. Reverse sneezing SHOULD NOT be confused with a different condition called "collapsed trachea".

Although reverse sneezing may appear to be scary, it only lasts a short time and can be ended by massaging the dog's neck and throat and encouraging the dog to swallow or lick. Another way to slow the reverse sneeze is to clap your hands to distract the dog, or pinch closed the dog's nostrils with your fingers, forcing it to breathe through its mouths and to swallow.

Luxation of the Patella

Luxation of the patella, or dislocation of the kneecap, is a common hereditary problem with chihuahuas and other small breeds. Patellar luxation can occur in varying degrees from minimal to debilitating. Very young dogs may be able to compensate for this deformity, but the condition tends to worsen over time. Most of the time the chihuahua is older before symptoms of patellar luxation are obvious.

The dislocation is most commonly found on the inner side of the patella. The attached ligaments become stretched over time until the patella is rarely where it is supposed to be, and may "pop" in and out of place very easily.

Recent studies have shown that immediate treatment is recommended, rather then waiting until the dislocation has crippled the dog. The reasoning is that, while the knee is dislocated, the entire body of the dog is compensating for it, causing deformations of many other skeletal areas.

Research has definitively shown that patellar luxation is an inherited trait, and dogs with this genetic problem should not be used in breeding programs.

Hypoglycemia

Hypoglycemia is a condition in which the chihuahua's blood sugar level drops to an extremely low level, causing "sugar shock." When levels of glucose in the blood drop rapidly, the dog's body and brain are deprived of essential nutrients. The results of hypoglycemia can be weakness, seizures, coma, and in severe cases, death.

Because chihuahuas are so small, they can be prone to hypoglycemia, especially when they are very young. Hypoglycemia is usually caused by stress, illness, lack of food, or by using up stored energy without it being replenished.

It is important to make sure that young puppies and very tiny chihuahuas eat regularly throughout the day. Another preventative for hypoglycemia is regular feeding of a high-calorie supplement called Nutrical, available from your veterinarian or your local pet store. If your not able to get the Nutrical you can also use Karo Syrup or some Honey.

If you suspect that your chihuahua is hypoglycemic, call your vet AT ONCE as this condition can be quickly fatal.

Megaesophagus

Vomiting versus Regurgitation

Most people do not realize that there is a difference between these two actions. Vomiting is an active process. There is gagging, heaving, and retching as the body actively expels stomach contents. Regurgitation is passive. For whatever reason, food is swallowed from the mouth but never really goes anywhere beyond that point. Food sits in the esophagus until it simply falls back out the mouth at some point. In the dog, megaesophagus is the most common cause of regurgitation.

What is Megaesophagus?

The esophagus is the tube connecting the throat to the stomach. When food is perceived in the esophagus, neurologic reflex causing muscle contraction and relaxation lead to rapid transport of the food into the stomach, like an elevator going down. Other reflexes prevent breathing during this swallowing process to protect the lungs from aspiration.

When these reflexes are interrupted such as by disease in the esophageal tissue or nerve disease, the esophagus loses its ability to transport food. Instead the esophagus loses all tone and dilates. Also, the reflex protecting the lung is disrupted and aspiration pneumonia commonly follows.

What Kind of Conditions Cause Megaesophagus?

Most cases involve young puppies. In these cases the condition is believed congenital though it often does not show up until the pup begins to try solid food. Congenital megaesophagus is believed to occur due to incomplete nerve development in the esophagus. The good news is that nerve development may improve as the pet matures. Prognosis is thus better for congenital megaesophagus than it is for megaesophagus acquired during adulthood.

Another congenital problem is the “Vascular Ring Anomaly.” This is a band of tissue constricting the esophagus. Such tissue bands are remnants of fetal blood vessels which are supposed to disappear before birth. They do not always do so. Improvement is obtained when the band is surgically cut but in 60% of cases some residual regurgitation persists.

In adult dogs, diseases that cause nerve damage can lead to Megaesophagus. Myasthenia gravis would be a common cause and very important to rule in or out. Myasthenia gravis is a condition whereby the nerve/muscle junction is destroyed. Signals from the nervous system sent to coordinate esophageal muscle contractions simply cannot be received by the muscle. Megaesophagus is one of its classical signs though general skeletal muscle weakness is frequently associated. This condition is treatable but special testing is needed to confirm it.

Scarring in the esophagus (as would occur after a foreign body episode or with damage to the esophagus from protracted vomiting) may be sufficient to interrupt neurologic transmissions or even narrow the esophagus so that food cannot pass through it. (Such a narrowing is called a “stricture.”) Technically, this is not a true megaesophagus as the muscles are working normally; there is simply an obstruction present. Special balloons can be inserted in the esophagus to dilate the narrowed area but some residual regurgitation is likely to persist. Tumors of the esophagus may have similar effects in that they, too, can cause obstruction.

The Diagnostic Plan

First, the megaesophagus must be diagnosed. This is done radiographically. If megaesophagus is not obvious on plain films, it is better not to use contrast (Barium) studies if possible. This is because megaesophagus patients have the tendency to inhale or "aspirate" food contents that back up in their throats. This is dangerous enough when the material is simply food but if barium is present and becomes inhaled, the body has great difficulty removing it from the lungs. Still, sometimes this is the only way to see the megaesophagus.

Treatment

Aspiration pneumonia is treated with fluids and antibiotics as is any other bacterial pneumonia, though these individuals may re-aspirate at any time and require treatment all over again. Hospitalization may be required.

Megaesophagus is a difficult condition to manage. Treatment requires dedication and commitment and still may produce poor results. Be sure your veterinarian has answered all your questions about this condition.

Demonstration of a Healthy Dog
(no megaesophagus)
(requires the Director Shockwave Plug-in; otherwise you will see a still picture)
Directions:
Click inside the dog’s food dish to drag out a piece of food. If you drag it near the dog’s mouth, he will open his mouth; place the food on his tongue and he will swallow it. You will then see the normal digestive process for a dog without megaesophagus.

Demonstration of a Dog with Megaesophagus
(requires the Director Shockwave Plug-in; otherwise you will see a still picture))
Directions:
Same as before, Click inside the dog’s food dish to drag out a piece of food. If you drag it near the dog’s mouth, he will open his mouth; place the food on his tongue and he will swallow it. You will then see the digestive process for a dog that is afflicted with megaesophagus.

(If your dog or puppy is having any signs or symptoms of Megaesophagus or would like more information on the subject contact your vet right away.)

The Chihuahuas Molera
Sponsored by The Chihuahua Club of America

Historically, the Chihuahua as developed in Mexico and the United States has displayed a "soft spot" on the top of the head. In the Chihuahua, this spot, or fontanel, is know as a MOLERA, and is the same as that found in human babies. In the past, this molera was accepted as a mark of purity in the breed, and it is still mentioned in most Chihuahua breed standards the world over.

It is important to note that while many Chihuahua puppies are born without the molera, there are probably just as many born with one, and its presence is nothing to become alarmed over. The molera in a Chihuahua will occur on the top of the head and may vary in shape and size when present.

Unfortunately, many lay people (and some Veterinarians not familiar with the Chihuahua) have tried to link the mere presence of a molera with the condition known as hydrocephalus. This has caused many new comers to the breed serious concern and undo worry. The truth is that a domed head with a molera present does not predispose the Chihuahua to this condition.

Along with the observations of devoted breeders over the years, there is adequate medical evidence to support this statement:

* In "Diseases of the Brain"(1989), Green & Braund stated that many clinically normal toy breeds may have open fontanelles without associated hydrocephalus.

* Drs. Walters and Rivers, Veterinarians at the University of Minnesota, concluded that there did not appear to be any relationship between the presence or size of a fontanelle and the condition of hydrocephalus.

* Dr. Alexander de Lahunta of Cornell University in New York, one of the top neurologist in this country, stated that it would be wrong to conclude that any opening is abnormal.

While it would be impossible to list all the medical documentation in this paper, these few included here are perfectly clear: the presence of a molera does not mean the dog has a medical problem.

The Chihuahua is a little dog! They belong in the house, at their owner's side, returning all the love they deserve to receive. With or without a molera, the healthy Chihuahua that is loved and given proper Veterinary care will live well into its teens as an irresistible member of the family.

Hydrocephalus

The presence of a molera in a chihuahua DOES NOT make the dog any more or less susceptible to brain injury, seizures or hydrocephalus.

The molera should not usually be any larger than the size of your thumb print, and there should be no swelling, bulging or throbbing. Check carefully on the sides of the head for normal bone there as well; make sure there is no more then one molera, on the top of the head only, as more than a single molera is not normal.

Hydrocephalus is the accumulation of excess cerebrospinal fluid in the brain and is not normal for any breed, nor is it curable. Hydrocephalus is also known as "water on the brain" or "hydro". When fluid accumulates in the brain, it compresses the brain against the skull. A puppy can be born with this disorder, or it can be caused by a brain infection or head injury later in life. Chihuahuas born with "hydro" do not generally live more than a few months, and they do not grow normally, often staying extremely tiny.

Signs of hydro include wide-set or protruding eyeballs (often with a lot of "white" showing at the corners), blindness, abnormal behavior, walking in circles, slowness (mental and physical), seizures, abnormally slow growth and lack of coordination.

Concerns about chihuahua moleras and/or hydro should be addressed to a licensed veterinarian. Be aware, however, that many veterinarians not familiar with chihuahuas have WRONGLY told owners that thier puppy is unhealthy and/or hydrocephalic just because of the presence of a normal molera. Diagnosis is based on the signs in conjunction with techniques to image the brain. In dogs with a molera, ultrasound can be performed by scanning through the molera to detect the excessive accumulation of fluid within the brain.

Unfortunately, there is no cure for hydrocephalus. Mild cases can be treated with steroids and diuretics to reduce pressure, or with a surgically inserted shunt to divert fluid from the brain to the abdomen.

The Genetics of the Chihuahua

THE GENETICS OF CANINE SIZE

I'm sure at least some of you have wondered at the amazing variation in size when looking at Chihuahuas. How is it that two normal sized, or even quite large parents produce a tiny offspring?

It's pure genetics.

The gene that controls chihuahua size has six parts, or alleles, and each parent passes on three of theirs to the offspring. Size alleles can be best described as having a value of either + (positive) or - (negative). The six "values" of the alleles are combined for a total, which determines size.

For example: +,+,+,-,-,-, = 6 alleles, or 3 positive and 3 negative. Think of + as "up 1", and - as "down 1." The first three positives cancel out the next three negatives (+1+1+1-1-1-1 = 0), so we end up with 0, or your proverbial "average".

Another example: +,-,+,-,-,-. Added together, we get 2 up and 4 down, with an end result of -2, "2 down", or below average size. (+1+1-1-1-1-1 = -2)

One more. +,+,+,+,-,-. 4 up and 2 down = +2, or "2 up".
(+1+1+1+1-1-1 = 2) In other words, a bigger than average pup.

Are you starting to get the idea? Ok, let's start passing things on to the kids.

Take two, average sized parents: Dad = +,+,+,-,-,- and Mom = +,+,+,-,-,-. Let's give them a litter of 3.

Pup #1: Take (at random) 2 minuses and 1 plus from Dad and 1 minus and 2 pluses from Mom. So, Pup #1 is -1,-1,+1,-1,+1,+1. The total is 0, or average size... an average size pup from 2 average sized parents. Not surprising.

Pup #2: Take (again, at random) 3 minuses from Dad and three minuses from Mom. What size pup do we get? Pup #2 is -1,-1,-1,-1,-1,-1. The total is -6, or one very tiny puppy.

Pup #3: Let's have all the pluses that both Mom and Dad can give (this combination can also happen randomly). That's +1,+1,+1,+1,+1,+1 = 6, and results in a chihuahua much larger than either parent.

When you see how size is inherited, it all starts to make sense doesn't it? But genetics is only part of the story with regard to size.

It has been well documented that the human race is getting bigger and taller with each generation. When you look through museum reproductions of early settler's cottages, the height of doorways and the length of beds stand out as being quite small by today's standards.

This gradual, but steady increase in the size of humans has been attributed by scientists to improvements in diet and health care over the years. Diet is just one factor in what is generally referred to as "environment", and environment plays a major role in the size of chihuahuas as well. Proper nutrition, maternal care, warmth and exercise all contribute to growth in a puppy.

The last variable in determining size is a congenital factor affecting growth. New research from the Canine Genome Project has shown a link between size and thyroid development. What is not clear yet is whether size is effecting the development of the thyroid or the development of the thyroid is effecting size. It is well documented, however, that the very tiny examples of our breed have more frequent and serious health problems than normal sized chihuahuas.

THE GENETICS OF CHIHUAHUA COAT LENGTH

The length of a chihuahua's coat is determined by two genes. The smooth coat gene is DOMINANT (indicated by capital letters), and the long coat gene is RECESSIVE (indicated by lower case letters).

The dominant smooth coat gene, if present, will completely hide the recessive long coat gene. So, a dog can be a smooth coat (the dominant gene is expressed, or seen), and have a hidden long coat gene, which it can pass on to the offspring.

The Chihuahua Is A Chihuahua!

Sponsored by The Chihuahua Club of America

The official A.K.C. Breed Standard describes the Chihuahua as a small dog that comes in two varieties or coat types. The difference in coat type (the Long Coat or the Smooth Coat) is the only official description used to identify a difference within this breed. Our Standard does not categorize the Chihuahua by size.

For the purpose of showing and record keeping, the American Kennel Club includes the Chihuahua (along with 16 other breeds) in the Toy Group. Therefore, irrespective of their weight or physical stature, ALL Chihuahuas registered with A.K.C. are considered to be a toy breed of dog.

As with all living things, there will be a size variance between individual dogs within this breed. Within the human family, brothers and sisters will differ in height and in weight, as well as other physical attributes. They are described as humans, male or female, and there is seldom if ever a need to break the description down further. The same holds true in regard to the Chihuahua; they are Chihuahuas-Long Coat/Smooth Coat, Male/Female.

Unfortunately, the additional adjectives used to describe the size difference and physical appearances are many; and have been misused for so long they now seem legitimate. Tea-cup, Pocket Size, Tiny Toy, Miniature or Standard - are just a few of the many tags and labels that have been attached to this breed over the years. The Chihuahua Club of America is concerned that these terms may be used to entice perspective buyers into thinking that puppies described in this way are of greater monetary value. They are not; and the use of these terms is incorrect and misleading.

Occasionally, within a litter, there may be a puppy that is unusually small. That puppy is a small Chihuahua and any other breakdown in description is not correct. To attach any of these additional labels to a particular pup is to misrepresent that animal as something that is rare or exceptional and causes a great deal of confusion among those fanciers who are looking for a Chihuahua.

The Chihuahua Club of America does not endorse or condone the use of any of these terms and would caution the perspective puppy buyer not to be misled by them.

We recognize that many Chihuahua fanciers do want the very small puppy. While they are adorable and can be perfectly healthy, the buyer should be cautioned as to the extra care that may be required with regard to their general health and well-being.

This site was last updated 04/28/08