Cats differ from mink and ferrets in their response to commercial vaccines: a histologic comparison of early vaccine reactions

Feline Injection-Site Sarcoma and Other Adverse Reactions to Vaccination in Cats

Vaccine-associated adverse events (VAAEs), including feline injection-site sarcomas (FISSs), occur only rarely but can be severe. Understanding potential VAAEs is an important part of informed owner consent for vaccination. In this review, the European Advisory Board on Cat Diseases (ABCD), a scientifically independent board of feline medicine experts, presents the current knowledge on VAAEs in cats, summarizing the literature and filling the gaps where scientific studies are missing with expert opinion to assist veterinarians in adopting the best vaccination practice. VAAEs are caused by an aberrant innate or adaptive immune reaction, excessive local reactions at the inoculation site, an error in administration, or failure in the manufacturing process. FISS, the most severe VAAE, can develop after vaccinations or injection of other substances. Although the most widely accepted hypothesis is that chronic inflammation triggers malignant transformation, the pathogenesis of FISS is not yet fully understood. No injectable vaccine is risk-free, and therefore, vaccination should be performed as often as necessary, but as infrequently as possible. Vaccines should be brought to room temperature prior to administration and injected at sites in which FISS surgery would likely be curative; the interscapular region should be avoided. Post-vaccinal monitoring is essential.

Feline injection-site sarcoma

Overview:

In cats, the most serious of adverse effects following vaccination is the occurrence of invasive sarcomas (mostly fibrosarcomas): so-called ‘feline injection-site sarcomas’ (FISSs). These develop at sites of previous vaccination or injection. They have characteristics that are distinct from those of fibrosarcomas in other areas and behave more aggressively. The rate of metastasis ranges from 10–28%.

Pathogenesis:

The pathogenesis of these sarcomas is not yet definitively explained. However, chronic inflammatory reactions are considered the trigger for subsequent malignant transformation. Injections of long-acting drugs (such as glucocorticoids, and others) have been associated with sarcoma formation. Adjuvanted vaccines induce intense local inflammation and seem therefore to be particularly linked to the development of FISS. The risk is lower for modified-live and recombinant vaccines, but no vaccine is risk-free.

Treatment and prevention:

Aggressive, radical excision is required to avoid tumour recurrence. The prognosis improves if additional radiotherapy and/or immunotherapy (such as recombinant feline IL-2) are used. For prevention, administration of any irritating substance should be avoided. Vaccination should be performed as often as necessary, but as infrequently as possible. Non-adjuvanted, modified-live or recombinant vaccines should be selected in preference to adjuvanted vaccines. Injections should be given at sites at which surgery would likely lead to a complete cure; the interscapular region should generally be avoided. Post-vaccination monitoring should be performed.

Identification of blue staining vaccine-derived material in inflammatory lesions using cultured canine macrophages

BACKGROUND

Vaccine reactions are described in cytology textbooks as having eosinophilic to magenta colored globules within and admixed with inflammatory cells. Recently, we have seen increased numbers of inflammatory lesions containing blue to blue-gray globular material, with historical information suggesting an association with rabies vaccination.

OBJECTIVES

The purpose of the study was to confirm the blue-gray and the eosinophilic material observed microscopically in some inflammatory lesions as being vaccine-derived.

METHODS

Three different vaccines were cytocentrifuged and Wright stained. Vaccine aliquots were also added to the culture media of canine-derived macrophages for 24 hours and the cells subsequently harvested, cytocentrifuged, and Wright stained. The globular material present in both preparations was compared to that observed in vaccine-induced inflammatory lesions. Morin staining was used to identify metal within vaccine material in both in vitro- and in vivo-derived cytology samples.

RESULTS

Vaccine-derived material has a characteristic color and appearance. Appearance of the material was consistent in cytologic samples, in cells incubated with the vaccine, and in cytocentrifuged preparations of the vaccine vial contents. The blue-gray globules stained positively for Morin stain, while the eosinophilic material did not stain.

CONCLUSIONS

Vaccine-induced inflammatory lesions may contain blue to blue-gray or magenta stained globular material. Blue-gray material was associated with administration of rabies vaccine Imrab 3 TF and the observed material may be metal-containing adjuvant. Magenta material was associated with other vaccines and negative for Morin stain, suggesting a metal-free adjuvant.

Origins of injection-site sarcomas in cats: the possible role of chronic inflammation-a review

The etiology of feline injection-site sarcomas remains obscure. Sarcomas and other tumors are known to be associated with viral infections in humans and other animals, including cats. However, the available evidence suggests that this is not the case with feline injection-site sarcomas. These tumors have more in common with sarcomas noted in experimental studies with laboratory animals where foreign materials such as glass, plastics, and metal are the causal agent. Tumors arising with these agents are associated with chronic inflammation at the injection or implantation sites. Similar tumors have been observed, albeit infrequently, at microchip implantation sites, and these also are associated with chronic inflammation. It is suggested that injection-site sarcomas in cats may arise at the administration site as a result of chronic inflammation, possibly provoked by adjuvant materials, with subsequent DNA damage, cellular transformation, and clonal expansion. However, more fundamental research is required to elucidate the mechanisms involved.

Orbital extraskeletal osteosarcoma following enucleation in a cat: a case report

OBJECTIVE

We present a unique case of a feline orbital extraskeletal osteosarcoma that developed 5 years post-enucleation.

HISTORY

In 2002, an ophthalmologist enucleated the left eye of a 2-year-old neutered male DSH and submitted it to the Comparative Ocular Pathology Laboratory of Wisconsin (COPLOW). COPLOW diagnosed the left eye with feline diffuse iris melanoma. In June 2007, the cat presented to another veterinarian for moderate swelling of the enucleation site. Palpation suggested a firm mass along the lateral orbital rim and an exploratory orbitotomy revealed a cyst with a mass adhered to it and the ventrolateral orbital rim. The cyst and mass were excised by the veterinarian and submitted to COPLOW. COPLOW diagnosed the tissue as an orbital conjunctival inclusion cyst and an acquired orbital osteosarcoma.

CONCLUSIONS

Following the enucleation, retained conjunctival epithelium became embedded in the connective tissue of the orbit and caused a cyst to develop. The cyst wall consisted of a myofibroblastic collagen-rich matrix and acted as a nidus of chronic irritation and tumor growth. This orbital osteosarcoma resembles feline vaccine-associated sarcomas (VAS), feline post-traumatic ocular sarcomas, and microchip-associated sarcomas in terms of it histopathology and its hypothesized pathogenesis related to exposure to antigenic material such as implanted epithelium, lens protein, vaccine components, and microchips as foreign bodies.

Adverse events after vaccine administration in cats: 2,560 cases (2002–2005)

OBJECTIVE

To determine the incidence of vaccine-associated adverse events (VAAEs) diagnosed within 30 days of vaccination in cats and characterize risk factors for their occurrence.

DESIGN

Retrospective cohort study.

ANIMALS

496,189 cats vaccinated at 329 hospitals.

PROCEDURES

Electronic records were searched for VAAEs that occurred after vaccine administration classified by practitioners as nonspecific vaccine reaction, allergic reaction, urticaria, shock, or anaphylaxis. Clinical signs and treatments were reviewed. The association between potential risk factors and a VAAE occurrence was estimated via multivariate logistic regression.

RESULTS

2,560 VAAEs were associated with administration of 1,258,712 doses of vaccine to 496,189 cats (51.6 VAAEs/10,000 cats vaccinated). The risk of a VAAE significantly increased as the number of vaccines administered per office visit increased. Risk was greatest for cats approximately 1 year old; overall risk was greater for neutered versus sexually intact cats. Lethargy with or without fever was the most commonly diagnosed VAAE. No localized reactions recorded in the 30-day period were subsequently diagnosed as neoplasia when followed for 1 to 2 years.

CONCLUSIONS AND CLINICAL RELEVANCE

Although overall VAAE rates were low, young adult neutered cats that received multiple vaccines per office visit were at the greatest risk of a VAAE within 30 days after vaccination. Veterinarians should incorporate these findings into risk communications and limit the number of vaccinations administered concurrently to cats.

Vaccine safety in the neonatal period

Administration of two doses of multicomponent vaccine to pups and kittens between 8 and 16 weeks of age has become a standard and important part of veterinary healthcare for this susceptible neonatal population. Currently available vaccine formulations conform to high standards of quality, safety and efficacy, but there remains a very small risk of adverse effect following vaccination. Quantifying this risk is extremely difficult and there are few meaningful data available. It would seem, however, that there is a higher prevalence of suspected adverse reactions (SARs) following vaccination in the neonatal period than in adult animals. The range of reported adverse reactions in neonates is broad, and includes: suspected lack of efficacy, mild non-specific and transient illness post-vaccination, and the development of hypersensitivity or autoimmune reactions. The most common reactions in both species are the various clinical manifestations of type I hypersensitivity. These events might relate to the induction of IgE antibody specific for extraneous protein incorporated within vaccines, in particular bovine serum albumin. That such reactions are most prevalent in small breed dogs, that also make the highest serological responses to vaccination, suggests a case for the formulation of low-dose products for miniature breeds. At least a proportion of neonatal vaccine SARs are related to the use of potent immunological adjuvants in certain products. A recent study in neonatal kittens has confirmed that non-adjuvanted vaccine induces significantly less local vaccine site inflammation than comparable adjuvanted products. The low risk of vaccine SARs in early life may therefore be further reduced by formulating non-adjuvanted vaccines with reduced content of extraneous protein, and by carefully considering the optimum vaccination protocol for any individual animal.

A kinetic study of histopathological changes in the subcutis of cats injected with non-adjuvanted and adjuvanted multi-component vaccines

The aim of this study was to investigate the subcutaneous tissue response to administration of a single dose of multi-component vaccine in the cat. Three groups of 15 cats were injected with one of three vaccine products with saline as a negative control. Cats in group A received non-adjuvanted vaccine; cats in group B received vaccine with a lipid-based adjuvant; whilst those in group C were vaccinated with a product adjuvanted with an alum-Quil A mixture. The vaccine and saline injection sites were sampled on days 7, 21 and 62 post-vaccination. Biopsies of these vaccine sites were examined qualitatively and scored semi-quantitatively for a series of parameters related to aspects of the inflammatory and tissue repair responses. These data were analysed statistically, including by principal component analysis. At all three time points of the experiment, there was significantly less inflammation associated with administration of non-adjuvanted vaccine (p=0.000). Although there was evidence of tissue repair by day 62 in all groups, those cats receiving adjuvanted vaccines had evidence of residual adjuvant material accumulated within macrophages at this late time point. The severity of tissue reactions may vary significantly in response to vaccines which include adjuvants or are non-adjuvanted.

Viral diseases of ferrets

Distemper and rabies vaccination are highly recommended because of the almost invariable fatal outcome of these conditions. Vaccination should constitute an important part of a ferret's preventative medicine program. With the current and anticipated development and licensing of new vaccines, practitioners are invited to gain awareness of the latest vaccine information. Establishment of a practice vaccination protocol with regards to the site of administration of rabies and distemper vaccines is paramount to document any future abnormal tissue reactions. Influenza is the most common zoonotic disease that is seen in ferrets. Although it generally is benign in most ferrets, veterinarians must take this condition seriously. The characteristic continuous antigenic variation of this virus may lead to more virulent strains; the recent emergence of avian influenza virus outbreaks; and the increased susceptibility of elderly, young, and immunosuppressed individuals.

Feline injection site sarcomas

Injection site sarcomas in cats have been the topic of more than 40 articles and over 20 scientific abstracts as well as multiple letters to veterinary journals, articles in the popular press, and Internet-based web sites. With the level of discussion that has surrounded this tumor entity, one might expect that great strides have been made in determining the etiology, epidemiology, and preferred treatment options for this disease. Nearly half of the publications on this subject are review articles, however, and that alone indicates both the high level of interest and the lack of information in this situation. This article summarizes the development of our current understanding of this tumor with regard to areas of research into the cause of injection site sarcomas, epidemiology, and the current standard of care for treatment of this iatrogenic disease.

Postinflammatory sarcoma in cats

Histological examination of 38 nodular formations extirpated from the site of vaccine administration to cats disclosed 25 cases of sarcoma and 13 of granuloma. Average age of the cats bearing sarcoma was 8.75 years whereas granuloma occurred at average age of 1.9 year. This age-relationship of the lesions, as well as their similar morphologic features indicated a progression of chronic inflammatory changes to tumors. Similar tumors were diagnosed in one cat with "posttraumatic ocular sarcoma" and in the uterus of female-cat with long-standing pyometra. These two cats were 15 and 8 years old, respectively. Experimental study of local reaction 21 days after administration of commercial, lipid-adjuvanted vaccine revealed in young cats (age 9 months) a reaction to immunogen, whereas in old animals (age 10 to 15 years) there was a reaction to foreign material. The data suggest that chronic inflammation and age-related immunodeficiency are instrumental in pathogenesis of the vaccine-associated sarcoma.