Imprimir Republish


Strays under control

Software program estimates the population of abandoned dogs and cats and simulates strategies to improve animal and human health

FAPESP_223_ILU_CntrPop_AFElisa CarretoNo one really knows the size of the dog and cat populations in Brazil, and this holds true for both supervised animals—those that have an owner and live in homes—and those living in the streets. The demographic characterization of dogs and cats is an important step in mapping out strategies to manage the population of these animals, and in controlling zoonoses such as rabies and visceral leishmaniasis, which are responsible for 55,000 deaths and 500,000 cases worldwide, respectively. Seeking a better approach to this problem, a group of researchers at the São Paulo campus of the School of Veterinary Medicine and Animal Husbandry (FMVZ), University of São Paulo (USP), have created a software program that can very accurately estimate how many domesticated dogs and cats live in the cities of Brazil. This program will soon be freely available to agencies of the Ministry of Health and city governments. “It is essential to know the street population, which is the result of animal abandonment,” says veterinarian Fernando Ferreira, a professor who coordinates the FMVZ’s graduate program.

Brazil has the highest incidence of visceral leishmaniasis in Latin America, with about 3,000 cases per year—90% of the total for the entire continent. Although rabies can be controlled through immunization, cases still occur in Brazil. In 1990 there were 50 cases in humans—a situation that improved to zero to two cases between 2007 and 2013. Abandoned animals pose a public health problem, because they are the principal reservoirs and transmitters of these diseases. At the same time, these animals may be run over, or suffer cruelty or abuse.

The most reliable method of measuring and classifying the canine street population was created by the Pasteur Institute in 2002. According to this method, strays represent about 5% of animals that have an owner. “Therefore, knowing how many supervised dogs live in a given area, it is possible to estimate how many are living in the streets in that same place,” Ferreira says. “Since there is a direct correlation between these two populations, strategies for control of abandoned dogs begin with reproductive control of domesticated animals,” explains Ferreira, who collaborated on the project with Professor Marcos Amaku, also from the FMVZ.

The software program, called Companion Animal Population Management (CAPM), was developed by Oswaldo Santos Baquero, a doctoral student and FAPESP grant recipient. “In my research, I am assessing the validity of a complex sampling design to estimate the size of the population of domesticated dogs in Brazilian cities. I also designed a mathematical model of population dynamics to simulate scenarios and identify intervention priorities,” Baquero says. In his view, mathematical modeling makes it easier to understand, for example, that the principal desired effect of sterilization is a larger infertile population, rather than a smaller overall population. “Mathematical models for rabies transmission in China suggest that the best way to control the disease is to reduce the canine birth rate and increase immunization. These two combined actions proved more effective than euthanasia.”

The objective of the FMVZ group is for the free-use software to eventually be used by government agencies such as the municipal zoonosis control centers. According to Baquero, the population dynamics of these animals is influenced by many factors, and the available tools for modifying some of these factors include prevention of abandonment, promotion of adoption, reproductive control, and control of migratory flows. The first step in using the CAPM program is to input demographic data on the city of interest, obtained from the Brazilian Institute of Geography and Statistics (IBGE), and determine the number and location of households to be surveyed. Next, a questionnaire is used to ask about the number of dogs and cats in the home, the sex and age of those animals, how they were acquired and whether or not they are spayed or neutered. “The results enable us to model different scenarios of population dynamics and identify intervention priorities,” explains Ferreira, who is Baquero’s thesis advisor.

The CAPM software is written in a flexible, open source code language known as “R,” which focuses on statistical programming and graphics generation. “Anybody can use it free of charge and see all the details of programming the available functions,” Baquero says. The results of most of the tool’s functions can be exported for viewing in more-generic computer programs such as spreadsheets, Google Earth, or the like. “The software has already been tested in the city of Votorantim in Sao Paulo State and is ready for use. But there are still complexities that can cause some users to be denied access. We are working to refine the program,” Baquero notes.

1. Evaluation of the impact of sterilization and/or euthanasia in controlling dog populations, using a population growth matrix model (2007/56295-8); Grant mechanism Regular Line of Research Project Award; Principal investigator Fernando Ferreira (USP); Investment R$81,807.49 (FAPESP).
2. Dog and cat population management: quantitative methods to characterize populations, identify priorities and to establish indicators (2013/12076-1); Grant mechanism Scholarships in Brazil – Doctoral; Principal investigator Fernando Ferreira (USP); Grant recipient Oswaldo Santos Baquero (USP); Investment R$87,567.48 (FAPESP).