Canine lymphoma: role of the environment

Author(s)

Katia Cristina Kimura

• Document type: Doctoral Thesis
• Press: São Paulo.
• Institution: Universidade de São Paulo (USP). Faculdade de Medicina Veterinária e Zootecnia (FMVZ/SBD)
• Defense date: 2012-08-08

Examining board members

Maria Lucia Zaidan Dagli; Bruno Cogliati; Julia Maria Matera; Gregory Mennecier; Lucas Campos de Sá Rodrigues

• Advisor: Maria Lucia Zaidan Dagli; Ricardo Augusto Dias

Abstract

Lymphoma is a malignant neoplasm of lymphoid tissue, recognized as a similar disease in dogs and humans. This study aimed to investigate whether environmental factors of the city of São Paulo could be associated with the development of lymphoma in dogs. For this, three studies were conducted. First we proceed to carry out a retrospective study covering the diagnosis and the immunophenotyping of lymphomas in dogs in Sao Paulo. We conducted a survey of lymphoma cases collected in the archives of the Pathology Service of the Department of Animal Pathology, Faculty of Veterinary Medicine at the University of Sao Paulo, from 1995 to 2009. The canine lymphomas were diagnosed morphologically according to the updated Kiel classification. Data as race, gender and age were collected. Lymphomas underwent immunophenotyping through immunohistochemistry, using primary antibodies anti-CD3 (T lymphocytes) and anti-CD79a (B lymphocytes). Mongrel dogs and with no predilection of gender were the most affected by lymphoma. In relation to the result of immunophenotyping, 55 (85%) lymphomas had T-cell origin and 10 (15%) come from B cells. A second study was an epidemiological questionnaire applied to 83 owners of dogs with lymphoma and to 84 controls. Multivariate analysis results suggested that dogs that live outdoors and close to busy highways or streets (more than 50 vehicles per minute within a radius of 100 meters) had a higher risk of developing lymphomas. The third study sought to compare the distribution of cases of canine lymphoma and human lymphomas in São Paulo. From 8804 cases of human non Hodgkin Lymphoma (NHL) recorded at the Cancer Registry of São Paulo, 629 cases were randomly selected between 1996 and 2006. In addition, 579 cases of NHL in dogs were obtained from five veterinary hospitals veterinary in the same period in Sao Paulo. All cases were geocoded according to the postal code. The Spearman correlation was highly significant between spatial distribution of human and canine lymphoma. The spatial overlap in cases of NHL suggests that dogs and humans may share common etiological factors, and possibly environmental factors may play a role in the etiology of NHL in both species. These results suggest a role of environmental pollutants in the risk of development of lymphoma in dogs. Future research should evaluate the components of air pollution that may be involved in the development of lymphoma. (AU)