Effectiveness of Reversible Contraception in Dog Population Management

Oswaldo Santos Baquero, Ana Pérola Drulla Brandão, Marcos Amaku, Fernando Ferreira

Abstract


Background: Dog fertility depends on human-influenced factors such as sterilization. Uncontrolled fertility can result in unwanted births and overpopulation, which causes problems of public health and animal welfare. Surgical sterilization has been the traditional means of reproduction control but its cost and time can be prohibitive for mass sterilization programs. Non-surgical sterilization alternatives exist, but most of them are reversible and their effectiveness as a population management tool is unknown. To better understand the consequences of reversible contraception, the fertility dynamics was modeled in a hypothetical dog population in a steady-state condition.

Materials, Methods & Results: The effect of reversible contraception was simulated using a coupled system of ordinary differential equations. A hypothetical steady-state population of 1000 animals was considered. It was formed by two compartments, one of fertile dogs and the other of infertile dogs. Natality compensated for a fraction of mortality, and the immigration rate compensated for the remaining fraction. The group of immigrant dogs was composed of fertile and infgertile dogs. The dog flow between compartments was given by both the contraception and fertility recovery rate. It was assumed that fertility reversibility in animals of the immigrant group was equal to that of animals already present in the population. Global sensitivities were calculated to assess the uncertainties of fertility dynamics associated with estimation of parameters. In addition, the local sensitivities were calculated to assess the influence of each parameter on fertility dynamics. The treatment effectiveness were expressed in terms of the total number of dogs treated for 20 years by taking a given irreversible contraception rate divided by the total number of dogs treated during the same period, and using the corresponding reversible contraception rate. The global sensitivity analysis consistently indicated a reduction in the number of fertile dogs. The local sensitivity analysis indicated that contraception rate was the most influential parameter, followed by the fertility recovery rate. The fraction of mortality compensated by natality was more influential than the fraction of infertile immigrants. Simulated scenarios indicated that the higher the contraception rate, the greater the difference between the effects of different fertility recovery rates. Variations in the proportion of infertile immigrants minimally changed the number of fertile dogs and the accumulated number of treated dogs. The increase in the fertility recovery rate caused effectiveness to decrease, especially when contraception rates were higher.

Discussion: In certain scenarios, reversible contraception can be a viable option for reproduction control. Evaluation of effectiveness of the reversible contraception showed both the importance of duration of the contraceptive effect and the interaction between the contraception and fertility recovery rates. Although the contraception rate is the main determinant of population fertility dynamics, the fertility recovery rate modulates the effect of contraception and determines its viability. Reversible contraception is a viable alternative when loss in effectiveness is compensated by a reduction in costs and ease of application of contraceptive treatments. The lower the contraception rate, the higher the similarity between the effects of reversible and irreversible contraception.


Keywords


sterilization; pets; reproduction control.

Full Text:

PDF

References


Amaku M., Dias R.A. & Ferreira F. 2010. Dynamics and Control of Stray Dog Populations. Mathematical Population Studies. 17(2): 69-78.

Baquero O.S., Amaku M. & Ferreira F. 2015. capm: an R package for Companion Animal Population Management. URL http://oswaldosantos.github.io/capm.

Baquero O.S., Akamine L.A., Amaku M. & Ferreira F. 2016. Defining priorities for dog population management through mathematical modeling. Preventive Veterinary Medicine. (123): 121-127.

Brun R., Reichert P. & Künsch H.R. 2001. Practical identifiability analysis of large environmental simulation models. Water Resources Research. 37(4): 1015-1030.

Eilts B.E. 2002. Pregnancy termination in the bitch and queen. Clinical Techniques in Small Animal Practice. 17(3): 116-123.

Ferreira F. 2009. Efeito da esterilização no controle de populações de cães. 38f. São Paulo, SP. Tese (Livre Docência) - Faculdade de Medicina Veterinária e Zootecnia, Universidade de São Paulo.

Garcia R., Calderón N. & Ferreira F. 2012. Consolidação de diretrizes internacionais de manejo de populações caninas em áreas urbanas e proposta de indicadores para seu gerenciamento. Revista Panamericana de Salud Publica. 32(2): 140-144.

Gershman K.A., Sacks J.J. & Wright J.C. 1994. Which dogs bite? A case-control study of risk factors. Pediatrics. 93(6): 913-917.

Kutzler M. & Wood A. 2006. Non-surgical methods of contraception and sterilization. Theriogenology. 66(3): 514-525.

Looney A., Bohling M.W., Bushby P.A., Howe L.M., Griffin B., Levy J.K., Eddlestone S.M., Weedon J.R., Appel L.D., Rigdon-Brestle K., Ferguson N.J., Sweeney D.J., Tyson K.A., Voors A.H., White S.C., Wilford C.L., Farrell K.A., Jefferson E.P., Moyer M.R., Newbury S.P., Saxton M.A & Scarlett J.M. 2008. The Association of Shelter Veterinarians veterinary medical care guidelines for spay-neuter programs. Journal of the American Veterinary Medical Association. 233(1): 74-86.

Marston L.C., Bennett P.C. & Coleman G.J. 2004. What happens to shelter dogs? An analysis of data for 1 year from three Australian shelters. Journal of Applied Animal Welfare Science. 7(1): 27-47.

Messam L.L.M., Kass P.H., Chomel B.B. & Hart L.A. 2008. The human-canine environment: a risk factor for nonplay bites? The Veterinary Journal. 177(2): 205-215.

Neilson J., Eckstein R. & Hart B. 1997. Effects of castration on problem behaviors in male dogs with reference to age and duration of behavior. Journal of the American Veterinary Medical Association. 211(2): 180-182.

Oliveira E.C.S., Moura M.R.P., de Sá M.J., Silva V.A., Kastelic J.P., Douglas R.H. & Marques A.P. 2012. Permanent contraception of dogs induced with intratesticular injection of a Zinc Gluconate-based solution. Theriogenology. 77(6): 1056-1063.

Patronek G.J., Glickman L.T., Beck A.M., McCabe G.P. & Ecker C. 1996. Risk factors for relinquishment of dogs to an animal shelter. Journal of the American Veterinary Medical Association. 209(3): 572-581.

R Core Team. 2015. R: A Language and Environment for Statistical Computing. R Foundation for Statistical Computing, Vienna, Austria. URL http://www.R-project.org/. [Accessed online July 2015].

Slater M.R. 2001. The role of veterinary epidemiology in the study of free-roaming dogs and cats. Preventive Veterinary Medicine. 48(4): 273-286.

Soetaert K. & Petzoldt T. 2010. Inverse modelling, sensitivity and Monte Carlo analysis in R using package FME. Journal of Statistical Software. 33: 1-28.

World Organization for Animal Health. 2010. Stray dog population control. Terrestrial Animal Health Code. Paris: OIE. Disponível em: . [Accessed online August 2015].




DOI: https://doi.org/10.22456/1679-9216.81175

Copyright (c) 2018 Oswaldo Santos Baquero, Ana Pérola Drulla Brandão, Marcos Amaku, Fernando Ferreira

Creative Commons License
This work is licensed under a Creative Commons Attribution 4.0 International License.