A vaccine-associated sarcoma (VAS) or feline injection-site sarcoma (FISS) is a type of malignant tumor found in cats (and, often, dogs and ferrets) which has been linked to certain vaccines. VAS has become a concern for veterinarians and cat owners alike and has resulted in changes in recommended vaccine protocols. These sarcomas have been most commonly associated with rabies and feline leukemia virus vaccines, but other vaccines and injected medications have also been implicated. [1]
VAS was first recognized at the University of Pennsylvania School of Veterinary Medicine in 1991. [2] An association between highly aggressive fibrosarcomas and typical vaccine location (between the shoulder blades) was made. Two possible factors for the increase of VAS at this time were the introduction in 1985 of vaccines for rabies and feline leukemia virus (FeLV) that contained aluminum adjuvant, and a law in 1987 requiring rabies vaccination in cats in Pennsylvania. [3] In 1993, a causal relationship between VAS and administration of aluminium adjuvanted rabies and FeLV vaccines was established through epidemiologic methods, and in 1996 the Vaccine-Associated Feline Sarcoma Task Force was formed to address the problem and promote research. [4]
In 2003, a study of ferret fibrosarcoma indicated that this species also may develop VAS. Several of the tumors were located in common injection sites and had similar histologic features to VAS in cats. [5] Also in 2003, a study in Italy compared fibrosarcoma in dogs from injection sites and non-injection sites to VAS in cats, and found distinct similarities between the injection site tumors in dogs and VAS in cats. This suggests that VAS may occur in dogs. [6]
Inflammation in the subcutis following vaccination is considered to be a risk factor in the development of VAS, and vaccines containing aluminum were found to produce more inflammation. [7] Furthermore, particles of aluminum adjuvant have been discovered in tumor macrophages. [8] In addition, individual genetic characteristics can also contribute to these injection-site sarcomas. [9] The incidence of VAS is between 1 in 1,000 to 1 in 10,000 vaccinated cats and has been found to be dose-dependent. [1] The time from vaccination to tumor formation varies from three months to eleven years. [10] Fibrosarcoma is the most common VAS; other types include rhabdomyosarcoma, myxosarcoma, chondrosarcoma, malignant fibrous histiocytoma, and undifferentiated sarcoma. [11]
Similar examples of sarcomas developing secondary to inflammation include tumors associated with metallic implants and foreign body material in humans, and sarcomas of the esophagus associated with Spirocerca lupi infection in dogs and ocular sarcomas in cats following trauma. Cats may be the predominant species to develop VAS because they have an increased susceptibility to oxidative injury, as evidenced also by an increased risk of Heinz body anemia and acetaminophen toxicity. [10]
VAS appears as a rapidly growing firm mass in and under the skin. The mass is often quite large when first detected and can become ulcerated or infected. It often contains fluid-filled cavities, probably because of its rapid growth. [12] Diagnosis of VAS is through a biopsy. The biopsy will show the presence of a sarcoma, but information like location and the presence of inflammation or necrosis will increase the suspicion of VAS. It is possible for cats to have a granuloma form after vaccination, so it is important to differentiate between the two before radical surgery is performed. One guideline for biopsy is if a growth is present three months after surgery, if a growth is greater than two centimeters, or if a growth is becoming larger one month after vaccination. [1]
X-rays are taken prior to surgery because about one in five cases of VAS will develop metastasis, usually to the lungs but possibly to the lymph nodes or skin. [8]
Treatment of VAS is through aggressive surgery. As soon as the tumor is recognized, it should be removed with very wide margins to ensure complete removal. Treatment may also include chemotherapy or radiation therapy. The most significant prognostic factor is initial surgical treatment. One study showed that cats with radical (extensive) initial surgery had a median time to recurrence of 325 days versus 79 days for cats with marginal initial excision. [3] The expression of a mutated form of p53, a tumor suppressor gene, is found commonly in VAS and indicates a poorer prognosis. [13]
New vaccine protocols have been put forth by the American Association of Feline Practitioners that limit the type and frequency of vaccinations given to cats. [14] Specifically, the vaccine for feline leukemia virus should only be given to kittens and high risk cats. Feline rhinotracheitis/panleukopenia/calicivirus vaccines should be given as kittens, a year later and then every three years. Also, vaccines should be given in areas making removal of VAS easier, [15] namely: as close as possible to the tip of the right rear paw for rabies, the tip of the left rear paw for feline leukemia (unless combined with rabies), and on the right shoulder—being careful to avoid the midline or interscapular space—for other vaccines (such as FVRCP). [16] There have been no specific associations between the development of VAS and vaccine brand or manufacturer, concurrent infections, history of trauma, or environment. [17]
Neutering, from the Latin neuter, is the removal of a non-human animal's reproductive organ, either all of it or a considerably large part. The male-specific term is castration, while spaying is usually reserved for female animals. Colloquially, both terms are often referred to as fixing. In male horses, castrating is referred to as gelding. An animal that has not been neutered is sometimes referred to as entire or intact.
Feline leukemia virus (FeLV) is a retrovirus that infects cats. FeLV can be transmitted from infected cats when the transfer of saliva or nasal secretions is involved. If not defeated by the animal's immune system, the virus weakens the cat's immune system, which can lead to diseases which can be lethal. Because FeLV is cat-to-cat contagious, FeLV+ cats should only live with other FeLV+ cats.
Onychectomy, popularly known as declawing, is an operation to remove an animal's claws surgically by means of the amputation of all or part of the distal phalanges, or end bones, of the animal's toes. Because the claw develops from germinal tissue within the third phalanx, amputation of the bone is necessary to fully remove the claw. The terms onychectomy and declawing imply mere claw removal, but a more appropriate description would be phalangectomy, excision of toe bone.
A mastocytoma or mast cell tumor is a type of round-cell tumor consisting of mast cells. It is found in humans and many animal species; it also can refer to an accumulation or nodule of mast cells that resembles a tumor.
Fibrosarcoma is a malignant mesenchymal tumour derived from fibrous connective tissue and characterized by the presence of immature proliferating fibroblasts or undifferentiated anaplastic spindle cells in a storiform pattern. Fibrosarcomas mainly arise in people between the ages of 25 and 79. It originates in fibrous tissues of the bone and invades long or flat bones such as the femur, tibia, and mandible. It also involves the periosteum and overlying muscle.
Carnivore protoparvovirus 1 is a species of parvovirus that infects carnivorans. It causes a highly contagious disease in both dogs and cats separately. The disease is generally divided into two major genogroups: FPV containing the classical feline panleukopenia virus (FPLV), and CPV-2 containing the canine parvovirus type 2 (CPV-2) which appeared in the 1970s.
The health of dogs is a well studied area in veterinary medicine.
Canine parvovirus is a contagious virus mainly affecting dogs and wolves. CPV is highly contagious and is spread from dog to dog by direct or indirect contact with their feces. Vaccines can prevent this infection, but mortality can reach 91% in untreated cases. Treatment often involves veterinary hospitalization. Canine parvovirus often infects other mammals including foxes, wolves, cats, and skunks. Felines (cats) are also susceptible to panleukopenia, a different strain of parvovirus.
Malignant histiocytosis is a rare hereditary disease found in the Bernese Mountain Dog and humans, characterized by histiocytic infiltration of the lungs and lymph nodes. The liver, spleen, and central nervous system can also be affected. Histiocytes are a component of the immune system that proliferate abnormally in this disease. In addition to its importance in veterinary medicine, the condition is also important in human pathology.
Phycomycosis is an uncommon condition of the gastrointestinal tract and skin most commonly found in dogs and horses. The condition is caused by a variety of molds and fungi, and individual forms include pythiosis, zygomycosis, and lagenidiosis. Pythiosis is the most common type and is caused by Pythium, a type of water mould. Zygomycosis can also be caused by two types of zygomycetes, Entomophthorales and Mucorales. The latter type of zygomycosis is also referred to as mucormycosis. Lagenidiosis is caused by a Lagenidium species, which like Pythium is a water mould. Since both pythiosis and lagenidiosis are caused by organisms from the class Oomycetes, they are sometimes collectively referred to as oomycosis.
Hypertrophic osteopathy is a bone disease secondary to cancer in the lungs.
A mammary tumor is a neoplasm originating in the mammary gland. It is a common finding in older female dogs and cats that are not spayed, but they are found in other animals as well. The mammary glands in dogs and cats are associated with their nipples and extend from the underside of the chest to the groin on both sides of the midline. There are many differences between mammary tumors in animals and breast cancer in humans, including tumor type, malignancy, and treatment options. The prevalence in dogs is about three times that of women. In dogs, mammary tumors are the second most common tumor over all and the most common tumor in female dogs with a reported incidence of 3.4%. Multiple studies have documented that spaying female dogs when young greatly decreases their risk of developing mammary neoplasia when aged. Compared with female dogs left intact, those spayed before puberty have 0.5% of the risk, those spayed after one estrous cycle have 8.0% of the risk, and dogs spayed after two estrous cycles have 26.0% of the risk of developing mammary neoplasia later in life. Overall, unspayed female dogs have a seven times greater risk of developing mammary neoplasia than do those that are spayed. While the benefit of spaying decreases with each estrous cycle, some benefit has been demonstrated in female dogs even up to 9 years of age. There is a much lower risk in male dogs and a risk in cats about half that of dogs.
An anal sac adenocarcinoma is an uncommon and aggressive malignant tumor found in dogs that arises from the apocrine glandular tissue of anal sac. The disease exists in cats as well, but is much less common in that species. They are the second most common cancerous cause of hypercalcaemia in dogs, following T-cell lymphoma.
A histiocytoma in the dog is a benign tumor. It is an abnormal growth in the skin of histiocytes (histiocytosis), a cell that is part of the immune system. A similar disease in humans, Hashimoto-Pritzker disease, is also a Langerhans cell histiocytosis. Dog breeds that may be more at risk for this tumor include Bulldogs, American Pit Bull Terriers, American Staffordshire Terriers, Scottish Terriers, Greyhounds, Boxers, and Boston Terriers. They also rarely occur in goats and cattle.
Feline viral rhinotracheitis (FVR) is an upper respiratory or pulmonary infection of cats caused by Felid alphaherpesvirus 1 (FeHV-1), of the family Herpesviridae. It is also commonly referred to as feline influenza, feline coryza, and feline pneumonia but, as these terms describe other very distinct collections of respiratory symptoms, they are misnomers for the condition. Viral respiratory diseases in cats can be serious, especially in catteries and kennels. Causing one-half of the respiratory diseases in cats, FVR is the most important of these diseases and is found worldwide. The other important cause of feline respiratory disease is feline calicivirus.
Vaccination of dogs is the practice of animal vaccination applied to dogs. Programs in this field have contributed both to the health of dogs and to the public health. In countries where routine rabies vaccination of dogs is practiced, for example, rabies in humans is reduced to a very rare event.
The health of domestic cats is a well studied area in veterinary medicine.
The rabies vaccine is a vaccine used to prevent rabies. There are several rabies vaccines available that are both safe and effective. Vaccinations must be administered prior to rabies virus exposure or within the latent period after exposure to prevent the disease. Transmission of rabies virus to humans typically occurs through a bite or scratch from an infectious animal, but exposure can occur through indirect contact with the saliva from an infectious individual.
Feline vaccination is animal vaccination applied to cats. Vaccination plays a vital role in protecting cats from infectious diseases, some of which are potentially fatal. They can be exposed to these diseases from their environment, other pets, or even humans.
A number of studies have studied adverse reactions in pets after administering vaccines to both dogs and cats. Vaccination guidelines regarding the recommended frequency and methods/locations take into consideration minimizing the risks of such events. The 2010 pet vaccination guidelines published by the WSAVA recommend the specific vaccines that pets should receive, and the cost-benefit analysis associated with the low risk of adverse effects leads researchers into adverse effects to still recommend vaccination.