Introduction

Humans have lived with dogs and cats for thousands of years; this represents a global phenomenon, and constitutes one of the closest and most intense interspecies bond. The intensity of this relationship has important consequences on the health of people and animals (Fortaleza 2006), and an impact on the sustainability of the ecosystem as a whole. Humans and pets together originate a social system (Faraco, 2008), and dogs and cats are considered valuable family members (Unger 1992, Beck & Katcher 1996, Cohen, 2002), thus they represent much more than potential sources of infection or other problems to towns or cities (Serpell 1996). Inadequate rearing and handling of such animals bring risks to human health, environmental deterioration, consequences to human welfare (Nassar & Fluke 1991), and demand actions to achieve their population control, which are fundamental to preserve human, environmental and animal health. In order to do so, it is necessary to characterize and understand these populations through descriptive studies that reveal the details of the human, dog and cat bonds. Such studies have been performed by other researchers with the goal of promoting population and zoonotic disease control in other regions and countries (Beran 1982, Beran & Frith 1988, Dias 2001, Dias et al. 2004, Grisi-Filho et al. 2008, Idespo & Wspa 2003, Kitala et al. 2001, Larrieu et al 1992, Lima Junior 1999, Nunes et al. 1997, Orihuela & Solano 1995, Paranhos 2002, Patronek et al. 1997, Wandeler et al. 1988, Who 1987, Who 1988). The present work describes regional data on human, canine and feline density, from September to December 2005, to improve knowledge of such populations and thus support actions for dog and cat population control. This research is part of a project on the evaluation of actions for dog and cat population control and the ecology of their populations, occurring from September 2005 to November 2008, subsidized by the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES), Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP), Center for the Study of Dog and Cat Populations (Centro de Estudos de Populações de Cães e Gatos--CEP) and Epidemiology and Bioestatistics Laboratory (Laboratório de Epidemiologia e Bioestatística--LEB) of the Veterinary Medicine and Animal Science Faculty of the Universidade de São Paulo, Technical Institute of Education and Animal Control (Instituto Técnico de Educação e Controle Animal--ITEC), Sociedade Beneficente Quintal de São Francisco and World Society for the Protection of Animals (WSPA); with support from the Associação Condomínio Habitacional de Vargem Grande (ACHAVE), São Paulo City Hall (Parelheiros Subdivision and Green and Environment Secretary), Partners Microchip and WorkPro Processamento de Dados.

Material and Methods

The suburb of Condomínio Vargem Grande, South of the city of São Paulo, was selected due to its natural delimitation, by the Atlantic Florest, and restricted road access, which make dog and cat migration more difficult. With an estimated human population of 35,000 people, 7,000 families and 5,000 dogs and cats (Achave 2005), and an area of three square kilometers. Data collection was done through individual house visits, from September to December 2005, employing two types of closed questionnaires, one per house and the other for each animal. Questionnaires were structured according to recommendations from the World Health Organization Guidelines for Dog Rabies Control (WHO, 1987), Guidelines for Dog Population Management (WHO & WSPA, 1990) and World Organization for Animal Health (OIE, 2006). Interviews were conducted by Health Agents from the local Health Basic Unity, veterinary students and veterinarians. The answers were verified for inconsistencies, which were than clarified with a second visit when needed. For statistical analysis, the program SPSS 9.0 was employed.

Results

We studied 2,599 houses, which encompassed 2,566 animals, dogs and/or cats (0.99 animal/house); 57.21% (n = 1487) houses maintained animals, 54.79% (n = 1424) maintained dogs, 9. 73% (n = 253) cats, 47.48% only dogs, 2.42% only cats, and 7.31% of all houses maintained dogs and cats; 65.7% (n = 935) maintaining dogs kept only one animal; 23.8% (n = 339) two, 6.1% (n = 87) three, and 4.3% (n = 61) maintained four or more dogs. In relation to cats, 69.6% (n = 176) of all houses maintained only one cat; 19.8% (n = 50) two; 5.1% (n = 13) three; 5.5% (n = 14) four or more cats. At houses with one inhabitant, the presence of dogs and cats was less frequent. We observed 2,519 (92.8%) castrated dogs and cats, being 2,144 (85.11%) dogs and 360 (14.29%) cats. Proportion dog: house was 1:1.2 and cat: house 1:7.2. From the 2,599 studied houses, total human inhabitants was 9,370. Dog: human proportion was 1:4.37 and 1:26 for cats. From the allotments with dogs (n = 1,424), in 81.6% (n = 1,162) there was only one house and in 11.5% (n = 164) there were two; 91.2% (n = 1,298) of the houses were home to one family. In relation to the acquisition of dogs within the period from November 2004 to October 2005, 66.55% (n = 1,339) did not acquire any animal; from those who did (n = 673), 71.92% (n = 484) acquired one dog. For cats, 90.01% (n = 1,639) did not acquire any cat; from those who did (n = 182), 68.13% (n = 124) acquired one animal. Total number of acquired animals was 1,009 dogs (1 dog per 9.3 inhabitants or 1 dog per each 2.6 houses) and 290 cats (1 cat per 32.3 inhabitants or 8.9 houses). In relation to the motivation for animal acquisition, 81.6% of the owners chose male dogs for company or because they enjoyed them and 14% for allotment security; for bitches, 85.5% were acquired for company or because they enjoyed them and 9.1% for allotment security. For cats, 92.3% of males and 93.4% of queens were acquired for company or because the owners enjoyed them. In relation to animal destiny during the twelve months before the interview (October 2004 to September 2005), 91.24% (n = 1,406) of the dogs remained in the houses; from those absent (n = 121), 47.11% (n = 57) became sick and died, 19.01% (n = 23) were donated to other people, 16.53% (n = 20) were killed by people.

Discussion

Paranhos (2002), in the city of São Paulo, and Nunes et al. (1997), in Aracatuba, observed lower percentages of houses with animals (43.30% of the houses with dogs or cats, 39.65% with dogs, and 6.25% with cats in São Paulo; 55.2% with either dogs or cats in Aracatuba); higher proportions were observed in Costa Rica, 62.5% of the houses with dogs (Idepo & Wspa 2003), and in the United States, 76% of the houses with dogs and 52.2% with cats (Patroneck et al. 1997). Patroneck et al. 1997 observed in St. Joseph County, United States, similar values for the presence of dogs only, 48%, an almost ten times higher percentage of houses with only cats, 23.9%, and more than three times the value reported here for houses with dogs and cats, 28.1% (1.4 dog per house with dogs and 1.8 cat per house with cats). In relation to the number of animals per house, similar values were observed in Costa Rica, 61% with one dog and 25% with two (Idepo & WSPA, 2003); Patroneck et al. 1997 observed higher values for houses with one dog (72%) and lower values for houses with two (21.7%), three (4.3%) or four or more dogs (2.0%). The frequence of houses with four or more dogs in our work was more than double the value observed by Patroneck et al. 1997 (4.3%). In relation to cats, Patroneck et al. 1997 observed lower values for houses with one cat (57.4%) and higher values for houses with two (28.4%), three (7,3%) and four or more cats (6.9%). In our results, there is 0.83 dog per house (1 dog:1,2 house) and one dog per 4.37 inhabitants (1:4.37). Paranhos (2000) encontrou menor densidade canina, 1:7; other work in São Paulo Metropolitan Region observed 0.84 dogs per house and 1:5.14 (dog: human) in Taboão da Serra (Dias et al., 2004) and 1:5.5 in Guarulhos (Dias, 2001). Nunes et al. (1997) observed 1:3.6 in Aracatuba; in Recife, Pernambuco, 1:9.1 (Lima Junior 1999); in other countries of Latin America, 1:2.6 in Argentina (Larrieu 1992), 1:4.5 in México (Orihuela et al. 1995), 1:1.56 and 1:1.65 in Costa Rica (Idepo & WSPA 2003). Kitala et al. 2001 observed in Quenia 1:8 e 1.4 dog per house. In relation to cats, we observed 0.14 cats per house (1 cat:7,2 houses) and the cat: human ratio was 1:26. Paranhos 2000, also working in the city of São Paulo, observed lower cat density, 1:46; other work in São Paulo Metropolitan Region observer the same frequence of cats per house, 0,14 cat, and 1 cat:24,3 humans in Guarulhos (Dias 2001), and 1:30.57 in Taboão da Serra (Dias et al. 2004); in Recife, 1: 13.5 (Lima Junior 1999). The variation in reported values reflect the need for regional investigation of canine and feline populations for action planning in population and zoonosis control. In this aspect, Grisi-Filho et al. (2008) suggested the development of a study to estimate dog:human and cat:human ratios per administrative unity in the city of São Paulo. There is also a need for studies on the human-animal bond for a better understanding of this relationship, on the degree of responsible pet ownership and prevention of abandonment reasons and lack of animal control, since there are different beliefs, attitudes and behavior toward animals, even between regions of the same city. The motivation to live with animals in this study was mainly for companionship, which is different from Quenia, 99% for security reasons (Kitala et al. 2001), and from Costa Rica, 42.9% for company, 40.6% for house protection and 15.4% for company and protection (Idep & Wspa 2003). Regarding the destiny of the animals, the donation of animals for other families might be considered as a form of bond break-up and abandonment. A high percentage of animals killed by people was observed; although the causes are not known, such result might reflect the violence in this community. A high proportion of animals became sick and died. In this region, there was no veterinary service available. For action planning in dog and cat population control, as well as in the control of their zoonotic diseases control, it is necessary to estimate the number of animals per region, due to the high variation in animal density. Qualitative evaluations are needed to improve knowledge on human and animal demography and human-pet animal interactions to guide public health programs, especially the educational initiatives. The percentage of 57.21% houses with dogs and/or cats expresses a trend of humans to associate to pet animals which is similar to other countries. Obviously, such co-habitation is determined by social, cultural and biological factors. Bringing this result together with the data on animal owning motivation (enjoyment), there is a sign for the presence of a potential affective involvement.

Conclusion

Dog and cat densities vary regionally within the same city. In the region studied, the presence of dogs and cats was less frequent in houses with one inhabitant; most of the houses with two, three and four humans maintained dogs; 1,299 new dogs and cats were brought to the community within 12 months. Most of the families had dogs and cats for company. For the animals that were absent from their houses after 12 months, the major reason was sickness followed by death. The results obtained emphasize the relevance of periodical monitoring and attachment to context in question for health strategic planning. This kind of reflexion, based on the recognition of the complex and interactive character of the multiple realities within which we strive for animal population and zoonosis control, might be helpful in overcoming the endemic difficulties faced by public services in incorporating the many natural variables in the theoretical models proposed and, with such change, and in improving the efficiency of resources and results.

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