Hypervitaminosis A (HVA) is a condition that affects approximately 1% of the population. The term “hyper” refers to vitamin A deficiency, while “a” means excess. HVA occurs when there are not enough dietary sources of vitamin A or other nutrients required for proper growth and development. Vitamin A deficiencies may occur due to inadequate intake from food alone, but they can also result from exposure to sunlight during childhood and adolescence.
The most common symptom of HVA is a pale appearance of the skin. Other symptoms include loss of appetite, fatigue, muscle weakness, hair loss, poor wound healing and impaired vision. These effects are often severe enough to cause death if left untreated.
There have been no reported cases where HVA has caused any sort of permanent damage. However, it is possible that some individuals with this condition will develop cancer later in life.
There are two types of hypervitaminosis A: primary and secondary. Primary hypervitaminosis A (PHA) results from insufficient dietary intake of vitamin A. Secondary hypervitaminosis A (SHVA) results from excessive sun exposure resulting in increased production of vitamin A in the body.
Both conditions are very rare, occurring at a rate less than one person per million people worldwide. Sources of excessive dietary A include:
retinol, retinyl acetate, retinoic acid, and dietary supplements containing vitamin A.
retinyl palmitate contained in many cosmetic products.
The best way to prevent HVA is to eat a well-balanced diet that contains a wide variety of foods. In some cases, people with poor diets may need to take supplements. Excessive sun exposure should be avoided at all times, especially during childhood and adolescence.
It’s important to maintain a healthy lifestyle in general.
Vitamin A is vital to good health. But too much can be toxic. The minimum lethal dose is approximately 100,000 IU per day for adults.
However, the symptoms of HVA usually occur at lower dosages, although it varies from person to person. Ingesting between 15,000 to 20,000 IU per kilogram of body weight over a period of several months can lead to HVA in children and adolescents.
The best treatment for HVA is discontinuation of the offending agent along with supportive care to reduce the effects of vitamin A overdose. In many cases, hospitalization is required. The patient may be given fluids or forced to vomit if overdosed on pills.
If retinol acetate was ingested, then it may be diluted by drinking lots of water followed by a process known as chelation to prevent further damage. Some of the effects of HVA may be irreversible.
Below you can read about hypervitaminosis a in dogs from wikipedia.org. If you have any questions or would like to know more, feel free to ask us.
A canine transmissible venereal tumor is a common term for a rare form of cancer that affects dogs. It is classified as a soft tissue sarcoma, and specifically a multi- cellular transitional cell carcinoma. It is also referred to as an epitheliotropic systemic sarcoma.
The disease is not contagious, but rather is a mutation of the canine DNA. The cancer cells are contained within the cells and do not invade other organs or systems within the dog’s body. This type of cancer can be found in many parts of a dog’s body, but most commonly occurs in the genitals and mouth.
The canine transmissible venereal tumor is not a common occurrence, and has an incubation period of up to 10 years. The cancer is transferred from dog to dog during mating. It is believed to be spread through fluid that comes in contact with the tumor.
The disease can be transferred either internally or externally through this fluid. The cells mutate to other parts of the body and grow rapidly, creating the tumor. There is no known treatment or cure for this disease.
The tumor itself can be hard to detect in dogs that have a very fast growing type of the disease. The external tumor found on the genitals could be confused with another type of cancer or a type of infection. In most cases, however, the cells are slow growing and can be caught before they spread throughout the dog’s body.
Also, when caught early, the disease is easily treated and not life-threatening.
The disease has been extensively researched and is very common among dogs that have a large number of offspring. The more offspring a dog has, the higher the chance that one will contract the disease. It is thought that this disease is very similar to the soft tissue sarcomas that afflict humans.
Because this type of cancer is so rare in humans, it is still being researched.
The most common locations in which this disease is found are the genitals and the mouth. The tumor that occurs in the mouth is usually located on the tongue. This form of the cancer can be easily confused with other types of tumors or growths.
The best way to diagnose this type of cancer is through a biopsy. Because this disease is so rare, many veterinarians may not have seen it before and may misdiagnose it.
The disease can be transferred from dog to dog through mating. Once the cells mutate and grow, the cells begin to spread throughout the dog’s body. The tumor in the genitals is usually a hard lump that can be felt and seen by an owner.
Other than a cancerous tumor, there are other reasons why a dog would have a lump on or in the genitals. It is important to have a veterinarian examine your dog to determine if the lump is a cancerous tumor.
A lump in the genitals isn’t the only place where the disease can occur. The tumor in the mouth is usually a gray or black mass on the tongue or on the inside of the cheek. An owner may notice that their dog is not eating because food is falling out of their mouth.
This type of tumor is usually large and can be seen by an owner, but many times it is misdiagnosed as an infection.
The disease can be treated and cured if caught in time. The cells are very quick to reproduce, however, so it is important to catch the disease early. Chemotherapy, radiation therapy and surgery are all treatment methods that can be used to combat this type of cancer.
Keeping the animal healthy and stress-free is very important for fighting this disease.
If you find a lump or mass in your dog’s genitals or mouth, you should take him to the veterinarian immediately. If you wait too long, the disease could spread and treatment would become more difficult. It is important to find out if the tumor is cancerous right away.
Once the veterinarian has determined that your dog has this type of tumor, he will begin treatment immediately. The sooner treatment begins, the better chance your dog has for survival.
The external genital or mouth tumors are very similar to each other and are both very rare in comparison to other types of tumors. They are also both slow growing, which gives the owner more time to take the dog to the veterinarian before symptoms get worse.
The treatment for either disease is similar, however the tumor in the mouth can be much easier to treat because a majority of it can be seen. With a dog with genital tumors, a veterinarian may not even be able to determine what needs to be cut out until after surgery.
The gray and black masses in the mouth can be removed using radiation therapy or chemotherapy if the tumor is small enough. These treatments can kill the cancerous cells while keeping the rest of the cells alive. Radiation can work on the tumor, but would not be recommended since it could damage nearby cells and tissues as well.
Chemotherapy is the treatment of choice for this type of disease. The chemicals can travel through the dog’s body and kill the cancerous cells. Since the cells are close to the surface in the mouth, this can be a very effective treatment.
Surgery is usually the treatment of choice for genital tumors. The veterinarian must remove as much of the tumor as possible while keeping as much of the genitals intact. It can be difficult to remove some of these tumors without damaging any of the organs and tissues in that area.
Some of these tumors can be seen and removed, while others are hidden inside other tissues.
The cells in the genital or mouth tumors are close to the surface, which makes them more accessible to radiation and chemotherapy. These treatments will kill the cancerous cells, but could damage some of the healthy cells as well. Surgery can remove most, if not all of the cancer, but there is a greater risk of damaging surrounding tissues.
The important thing to remember is that if you suspect your dog has either of these types of tumors you should have him seen by a veterinarian immediately. Early detection is very important in the treatment and prognosis for this disease. If treatment is successful, the dog should have a normal life span.
Some dogs will have a recurrence of this disease after treatment. This will depend on many factors include type of cell, type of medication or therapy and methodology used to treat the disease. Even if a recurrence happens you can still treat your dog using the same or different methods of treatment.
Your veterinarian will talk to you about these options if they become necessary.
While not a common problem, some dogs can develop canine nasal tumor. These tumors are fairly rare in comparison to the more common forms of canine cancer. Most veterinarians will go through their career without ever seeing a case of this disease.
The reason for this is that the genetic factors that lead to this type of cancer are not yet fully understood. There are multiple factors that are believed to lead to the development of this disease.
One of the factors could possibly be a response to a viral infection. This is based on the fact that many of these tumors are found near the mucosal tissues of the nose and mouth. In people, this type of tumor is also believed to be caused by a HPV infection.
The tumor in people is also linked to smoking and tobacco use. It is possible that a correlation exists between these factors and this cancer in dogs.
The tumors themselves begin in the mucosal cells. These are the cells that line the inside of the nose and mouth. The signs that a dog has this type of tumor are generally mucosal bleeding, which is generally blood coming from the nose.
Owners will generally believe that their pet has been scuffling with another animal. In reality, it is just the tumor causing bleeding.
There are other nasal tumors that occur in dogs and they are generally fibrous tumors. These are not believed to be related to the mouth or HPV.
Treatment for this type of tumor is generally surgery. The veterinarian must remove as much of the tumor as possible. In some cases, it might be necessary to remove part of the dog’s nose.
After the surgery, your dog will be worn a cone-shaped collar to prevent him from biting or rubbing his nose. The wound will also need to be kept clean and dry to give it the best chance of healing properly.
The prognosis for recovery is generally good if the entire tumor can be removed. There is also a chance of a recurrence, although this is fairly uncommon. Some dogs will require more than one surgery to remove all of the cancerous tissue.
The risk of damage to the normal tissues is always present as well.
There is a vaccine available for this disease, but it is not widely used because of the low occurrence and the need for yearly boosters. It is generally recommended that dogs that are at high risk of getting this type of cancer should be vaccinated. This includes larger breeds such as Boxers, Mastiffs, Newfoundlands and similar sized dogs.
Research is ongoing in an attempt to better understand and treat this disease. The long-term goal of this research effort is the development of a preventative vaccine against this cancer.
Sources & references used in this article:
Hypervitaminosis A by T Moore, YL Wang – Biochemical Journal, 1945 – portlandpress.com
Hypervitaminosis A induced teratogenesis by JAG Geelen, PWJ Peters – CRC critical reviews in toxicology, 1979 – Taylor & Francis
Hypervitaminosis A and bone by N Binkley, D Krueger – Nutrition reviews, 2000 – academic.oup.com
Hypercalcemia and skeletal effects in chronic hypervitaminosis A by BOY FRAME, CE JACKSON… – Annals of Internal …, 1974 – acpjournals.org
Hypervitaminosis D associated with drinking milk by CH Jacobus, MF Holick, Q Shao… – … England Journal of …, 1992 – Mass Medical Soc
Hepatic injury from chronic hypervitaminosis A resulting in portal hypertension and ascites by RM Russell, JL Boyer, SA Bagheri… – New England Journal of …, 1974 – Mass Medical Soc
Hypervitaminosis A and carotenemia by HW Josephs – American Journal of Diseases of Children, 1944 – jamanetwork.com