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Within the past 2 years, a putative causal relationship has been reported between vaccination against rabies and the development of fibrosarcomas at injection sites in cats. A retrospective study was undertaken, involving 345 cats with fibrosarcomas diagnosed between January 1991 and May 1992, to assess the causal hypothesis. Cats with fibrosarcomas developing at body locations where vaccines are typically administered (n = 185) were compared with controls (n = 160) having fibrosarcomas at locations not typically used for vaccination. In cats receiving FeLV vaccination within 2 years of tumorigenesis, the time between vaccination and tumor development was significantly (P = 0.005) shorter for tumors developing at sites where vaccines are typically administered than for tumors at other sites. Univariate analysis, adjusted for age, revealed associations between FeLV vaccination (odds ratio [OR] = 2.82; 95% confidence interval [CI] = 1.54 to 5.15), rabies vaccination at the cervical/interscapular region (OR = 2.09; 95% CI = 1.01 to 4.31), and rabies vaccination at the femoral region (OR = 1.83; 95% CI = 0.65 to 5.10) with fibrosarcoma development at the vaccination site within 1 year of vaccination. Multivariate analysis, adjusted for age and other vaccines, also revealed increased risks after FeLV (OR = 5.49; 95% CI = 1.98 to 15.24) and rabies (OR = 1.99; 95% CI = 0.72 to 5.54) vaccination.(ABSTRACT TRUNCATED AT 250 WORDS)

Retrospective data on the type and prevalence of splenic disease in cats were evaluated in a large number of feline splenic tissues (n = 455) submitted as surgical and necropsy specimens from private veterinary hospitals in California during a period of approximately 5.5 years. Primary and metastatic neoplasia accounted for 37% of all feline splenic lesions. Mastocytoma, lymphosarcoma, myeloproliferative disease, and hemangiosarcoma, in that order, accounted for the bulk of neoplasia. Submission of accessory splenic tissue from either the omentum or pancreas accounted for 4% (17/455), whereas hyperplastic nodules, hematomas, and the combination of these changes in the spleen accounted for 4% (19/455). Splenitis was found in 2% (8/455) of submissions. Thromboembolism with regional splenic infarction accounted for 1% (4/455) of splenic lesions in cats. The remaining splenic lesions each accounted for less than 1% of total splenic submissions, and as such, were considered incidental and of questionable clinical importance.

The prevalence data of splenic diseases from 3 sources were studied. Group 1 consisted of a general diagnostic survey of accessions submitted from private veterinary hospitals in California during a period of approximately 4 years and included 1,372 submissions of canine splenic tissue. Group 2 consisted of surgical splenectomy specimens from 92 dogs; the specimens were submitted to the laboratory for gross and histologic evaluation prior to fixation, and a questionnaire was subsequently sent to determine the outcome of the disease. Group 3 was made up of specimens of 105 splenic lesions derived from a large colony of Beagles with complete medical records and records of pathologic findings. In this study, splenic hematoma and hyperplastic nodule, not hemangiosarcoma, made up the bulk of splenic lesions. Hemangiosarcoma was the most frequent neoplasm of the canine spleen, but the combined prevalence of all other splenic neoplasms was similar to that of hemangiosarcoma alone. Splenic hematoma and hemangiosarcoma were grossly indistinguishable in most cases. Hyperplastic lymphoid nodules and hematomas of the spleen appeared to represent a continuum. If that finding was correlated with microscopic splenic blood flow, specific causal relationship could be suggested. Prognostically, the live/dead ratio and mean survival of dogs with various splenic lesions differed significantly.