Key Findings
Researchers conducted seven rounds of capturing and recapturing free-roaming dogs in the same neighborhoods in Divinópolis to determine the prevalence of visceral leishmaniasis (VL) among the dog population.
Dogs that tested positive were euthanized immediately following government guidelines. The results showed a declining trend in VL prevalence over the seven trials; however, the disease was not completely eliminated during the 14-month research period.
Given the controversies surrounding euthanasia, researchers advocate for promoting responsible pet ownership to reduce the influx of free-roaming dogs, which are often susceptible to VL.
Summary
Visceral leishmaniasis (VL) is a major public health issue, particularly in Brazil, where dogs act as the main domestic reservoir for Leishmania infantum, the pathogen responsible for VL. The disease is transmitted to humans via the bites of infected sandflies, making the control of VL in dogs critical to reducing human cases. Brazil has responded by implementing a policy of euthanizing infected dogs to curb the disease’s spread. Free-roaming dogs, which are more frequently exposed to sandfly bites and exhibit erratic roaming behaviors in urban areas, complicate this control strategy. Despite the significance of this issue, there are limited studies on the effectiveness of euthanizing free-roaming dogs, and the exact spatial distribution of canine VL remains largely unknown, making targeted control measures challenging.
The study, titled “Prevalence of Visceral Leishmaniasis in a Population of Free-Roaming Dogs as Determined by Multiple Sampling Efforts: A Longitudinal Study Analyzing the Effectiveness of Euthanasia,” had three primary aims:
- To determine the prevalence of VL in a population of free-roaming dogs through serological testing conducted in seven sampling efforts in an endemic region of Brazil.
- To establish the spatial distribution of the captured and infected dogs.
- To evaluate the effectiveness of euthanizing seropositive free-roaming dogs in controlling the disease.
The study took place in Divinópolis, the largest city in the center-west of the State of Minas Gerais, Brazil, with an estimated population of 234,937 inhabitants. Between 2009 and 2017, there were twenty-seven confirmed cases of human VL in this area. The researchers focused on eight neighborhoods within the city, home to approximately 8,000 residents.
Data collection involved capturing free-roaming dogs every two months over a 14-month period between 2012 and 2014. Each captured dog underwent serological testing for VL using the Enzyme-Linked Immunosorbent Assay (ELISA) and the Immunofluorescent Antibody Test (IFAT). Dogs that tested positive by both assays were considered infected and were euthanized, following the recommendations of the Brazilian Ministry of Health. At the end of the seven capture efforts, previously stored serum samples were also evaluated using the Dual-Path Platform (DPP) as a third test..
A total of 328 dogs were captured and recaptured, representing 41.4% of the total population. In total, 583 assays were performed, with 255 conducted on dogs during their second or subsequent capture. The overall prevalence of infected dogs was 7.6% (25 out of 328) by ELISA and IFAT, and 8.2% (27 out of 328) by DPP and ELISA, with strong alignment identified between these testing methods.
The prevalence of infected dogs generally declined over the seven sampling efforts, except for efforts #4 and #7, where an increase was observed compared to previous efforts. This decline suggests that the euthanasia policy has some effectiveness in reducing VL prevalence. However, the persistence of infected dogs in all seven capture efforts underscores the difficulty of achieving complete elimination through euthanasia alone. It is likely that the removal of infected dogs through euthanasia is counteracted by the constant influx of new, potentially susceptible dogs into the population. This influx is often due to abandonment or natural population growth, highlighting a critical gap in the current control strategy.
Given this gap, the authors advocated for promoting responsible pet ownership instead of relying on euthanasia. Responsible ownership is less controversial and can help manage overpopulation while controlling the spread of VL and other zoonotic diseases.
The spatial distribution of free-roaming dogs in the study area was found to be heterogeneous, with a higher concentration in commercial areas and streets with significant human activity. These areas typically provide food sources, either through waste from food stores and restaurants or direct feeding by community members. The study suggests prioritizing commercial areas for future interventions due to the higher likelihood of dog congregation. However, it also emphasizes the need for community education on the responsibilities of interacting with free-roaming dogs. Proper care, including adequate food, water, shelter, and healthcare, is essential to prevent harm and control the spread of diseases like VL.
In summary, the study highlights the limitations of euthanasia as a standalone strategy for controlling VL among free-roaming dogs. A more comprehensive approach, including community engagement and responsible pet ownership, is necessary to effectively manage and reduce the transmission of VL.
Miscellaneous
Data From Study:
Dog Population Management / Case Studies / Divinópolis Free-Roaming Dog VL Euthanasia
Year of Publication:
2018
External Link:
Saulo N. Melo, Rafael G. Teixeira-Neto, Guilherme L. Werneck, Claudio J. Struchiner, Renata A.N. Ribeiro, Lorena R. Sousa, Marcella O.G. de Melo, Clóvis G. Carvalho Júnior, Klauber M. Penaforte, Marianna N. Manhani, Vanessa V. Aquino, Eduardo S. Silva, Vinícius S. Belo, Prevalence of visceral leishmaniasis in A population of free-roaming dogs as determined by multiple sampling efforts: A longitudinal study analyzing the effectiveness of euthanasia, Preventive Veterinary Medicine, Volume 161, 2018, Pages 19-24, ISSN 0167-5877,
https://doi.org/10.1016/j.prevetmed.2018.10.010