Canine visceral leishmaniasis in Araçatuba, state of São Paulo, Brazil, and its relationship with characteristics of dogs and their owners: a cross-sectional and spatial analysis using a geostatistical approach

Global Distribution of Canine Visceral Leishmaniasis and the Role of the Dog in the Epidemiology of the Disease

Visceral leishmaniasis is a disease caused by protozoa of the species Leishmania (Leishmania) infantum (syn = Leishmania chagasi) and Leishmania (Leishmania) donovani, which are transmitted by hematophagous insects of the genera Lutzomyia and Phlebotomus. The domestic dog (Canis familiaris) is considered the main urban reservoir of the parasite due to the high parasite load on its skin, serving as a source of infection for sandfly vectors and, consequently, perpetuating the disease in the urban environment. Some factors are considered important in the perpetuation and spread of canine visceral leishmaniasis (CVL) in urban areas, such as stray dogs, with their errant behavior, and houses that have backyards with trees, shade, and organic materials, creating an attractive environment for sandfly vectors. CVL is found in approximately 50 countries, with the number of infected dogs reaching millions. However, due to the difficulty of controlling and diagnosing the disease, the number of infected animals could be even greater. In the four continents endemic for CVL, there are reports of disease expansion in endemic countries such as Brazil, Italy, Morocco, and Tunisia, as well as in areas where CVL is not endemic, for example, Uruguay. Socio-environmental factors, such as migration, drought, deforestation, and global warming, have been pointed out as reasons for the expansion into areas where it had been absent. Thus, the objective of this review is to address (i) the distribution of CVL in endemic areas, (ii) the role of the dog in the visceral leishmaniasis epidemiology and the factors that influence dog infection and the spread of the disease, and (iii) the challenges faced in the control of CVL.

The path of canine visceral leishmaniasis versus the path of Center for Zoonoses Control: contributions of spatial analysis to health

Visceral leishmaniasis (VL) is a public health problem in Brazilian municipalities. As much as there is a planning of public policies regards VL in São Paulo State, new cases have been reported and spread. This paper aims to discuss how the Center for Zoonoses Control conducts its actions spatially in endemic city of Presidente Prudente, São Paulo State. Data are from the Municipal Health Department of Presidente Prudente, Adolfo Lutz Institute, and Brazilian Institute of Geography and Statistics. We spatially estimated the dog population per census tract and used geoprocessing tools to perform choropleth maps, spatial trends, and spatial autocorrelation. We found a spatial pattern of higher prevalence in the city’s outskirt and a positive statistically significant spatial autocorrelation (I = 0.2, p-value < 0.000) with clusters of high-high relationships in the Northwest part of the city. Moreover, we identified a different direction in the path of the conducted serosurveys versus the canine VL trend, which stresses the fragility of the Center for Zoonoses Control actions to control the disease. The Center for Zoonoses Control always seems to chase the disease. The spatial analysis may be useful for rethinking how the service works and helps in public policies.

Impact of the dog population and household environment for the maintenance of natural foci of Leishmania infantum transmission to human and animal hosts in endemic areas for visceral leishmaniasis in Sao Paulo state, Brazil

When it comes to visceral leishmaniasis (VL) in Brazil, one of the main targets of public health policies of surveillance is the control of domestic canine reservoirs of Leishmania infantum. This paper aims to evaluate the effect of the dog population and household environment for the maintenance of natural foci in the transmission to human and animal hosts in an endemic city for VL, Bauru, in Brazil. We collected 6,578 blood samples of dogs living in 3,916 households from Nov.2019 to Mar.2020 and applied geospatial models to predict the disease risk based on the canine population. We used Kernel density estimation, cluster analysis, geostatistics, and Generalized Additive Models (GAM). To validate our models, we used cross-validation and created a receiver operating characteristic (ROC) curve. We found an overall canine VL (CVL) seroprevalence of 5.6% for the sampled dogs, while for the households, the positivity rate was 8.7%. Odds ratios (OR) for CVL increased progressively according to the number of canines for >2 dogs (OR 2.70); households that already had CVL in the past increased the chances for CVL currently (OR 2.73); and the cases of CVL increase the chances for human VL cases (OR 1.16). Our models were statistically significant and demonstrated a spatial association between canine and human disease cases, mainly in VL foci that remain endemic. Although the Kernel density ratio map had the best performance (AUC = 82), all the models showed high risk in the city's northwest area. Canine population dynamics must be considered in public policies, and geospatial methods may help target priority areas and planning VL surveillance in low and middle-income countries.

Socio-economic and environmental factors associated with the occurrence of canine infection by Leishmania infantum in Teresina, Brazil

American visceral leishmaniasis (AVL) is a zoonosis caused by protozoan parasites of the genus Leishmania. In Brazil, the disease is caused by Leishmania infantum and the main vector is the phlebotomine sandfly Lutzomyia longipalpis, found both in natural ecotopes and in the rural and urban environments, being very well adapted to the peridomestic environment. The domestic dog has been incriminated as the main reservoir of the parasite in the urban environment, but the control measures based on culling seropositive dogs have not shown to be effective to contain the spread of the disease throughout the country. Many studies evaluated risk factors for human visceral leishmaniasis but few focused on the socioeconomic and environmental factors associated with infection among dogs. Knowledge of these factors might help identify the conditions that contribute to the maintenance of transmission cycles in the urban environment and identify new targets for intervention. The objective of this study was to assess the association between socioeconomic and environmental factors and the occurrence of canine leishmaniasis at Teresina city, Brazil. This cross-sectional study was developed in ten districts of Teresina, involving 532 houses and 810 dogs. Peripheral blood samples were collected by vein punction using vacutainer tubes without anticoagulant for performing serological test (indirect immunofluorescence - IFI). Serum samples with IFI titers ≥1: 80 were considered positive. Owners of the selected dwellings were interviewed using a semi-structured questionnaire addressing socioeconomic and environment aspects. The association between variables and seropositivity was assessed through multilevel logistic regression models. Global seropositivity was 39%. There was no statistically significant difference between seropositivity and age and sex of animals, literacy of the household head, presence of other domestic animals or with household characteristic like water supply, inadequate sewage disposal system, type of floor and roof. Mixed-breed dogs and those living for a long time in houses with absence of masonry walls and presence of a kennel showed higher odds of seropositivity. These results suggest that some peridomestic characteristics, especially the absence of barriers that allow dogs to have free access to the street, in association with the presence of a kennel, might contribute to maintaining the infection cycle in urban areas. Intervention measures oriented to the management of the peridomestic environment and responsible dog possession could be useful tools for reducing disease burden in endemic area.

Molecular and Seroepidemiological Survey of Visceral Leishmaniasis in Owned Dogs (Canis familiaris) in New Foci of Rural Areas of Alborz Province, Central Part of Iran: A Cross-Sectional Study in 2017

Background:

Mediterranean form of visceral leishmaniasis (VL) is endemic among some provinces of Iran. The present study was designed to determine the prevalence of canine visceral leishmaniasis (CVL) in the owned dogs of the rural areas of Alborz Province near Tehran as the capital of Iran.

Methods:

This study conducted on 303 owned dogs that selected using a stratified random sampling method. The direct agglutination test (DAT) was used to determine the frequency of Vl. The spleen biopsy was taken from the serology-positive dogs for the confirmation of CVL in the suspected dogs. Nested PCR and sequencing methods were used to determine the type of Leishmania species in the dogs which were parasitological positive.

Results:

Overall, the DAT results of 9 dogs (2.97%, CI: 1.57–5.55) showed anti Leishmania antibodies at titers ≥ 1:320 indicating VL infection. One dog (0.33%, CI 95%: 0.06–1.85) showed clinical signs and symptoms of VL. There was a significant correlation between the positive cases of CVL and rural area (p< 0.001). The Leishmania was observed in the impression smears that were prepared from spleen biopsy of five the studied dogs. Leishmania infantum were confirmed in all them using nested–PCR assay. The sequence analysis of all five isolates was 95% similar to L. infantum.

Conclusion:

This study shows that domestic cycle of L. infantum has been established in rural areas of Alborz province where located near Tehran as capital city of Iran. It is necessary to increase the awareness and monitoring of the disease periodically.

[Control of canine visceral leishmaniasis by euthanasia: estimated effect based on a survey and mathematical modeling]

Visceral leishmaniasis is an emerging and neglected disease that is currently expanding to urban areas. The incidence of human disease is related to canine infection. Araçatuba and Birigui are municipalities (counties) in the state of São Paulo, Brazil, with 8-10% seroprevalence of canine infection and that employ control strategies targeting the canine reservoir, based on serological survey and culling of seropositive dogs. Using data from these control programs to parameterize mathematical models, this study assessed the efficacy of these activities. We estimated that current control is capable of reducing the incidence of canine visceral leishmaniasis (CVL) by approximately 20%. Assuming continuous control and three times the current serological survey activities in Araçatuba and Birigui, culling dogs with a positive CVL diagnosis would be effective for the control of canine infection. Although theoretically possible, in practice the control of CVL with the currently recommended strategies is insufficient, since it would require overcoming the difficulties in these activities, such as lack of material, human, and financial resources, besides associated ethical and legal issues.

Making Vector-Borne Disease Surveillance Work: New Opportunities From the SDG Perspectives

Surveillance of vector-borne diseases (VBDs) exemplifies a One Health approach, which entails coordinated, collaborative, multidisciplinary, and cross-sectoral approaches to address potential or existing health risks originating at the animal-human-ecosystem interface. However, at the intervention stage of the surveillance system, it is sometimes difficult or even impossible to act. The human dimension of VBD control makes them wicked problems requiring an interdisciplinary systems approach beyond the One Health domain. Here, we make a case that the agenda of the UN Sustainable Development Goals (SDGs) can offer new opportunities to address these issues. The health of the population is a concern to us all and is more or less related to all 17 SDGs. The SDGs can provide a common language by which the interests of various stakeholders can be matched and the challenges that society faces identified, studied, and alleviated. To illustrate, the control and prevention of two VBDs, dengue and Lyme borreliosis, were selected and related to specific SDGs. Further, we use the framework proposed by the International Council of Science to: (1) show synergies and trade-offs between the various SDGs; and (2) present SDG 3 to identify policy that can be related to prevention. Engaging in an integrated approach will confront stakeholders with various viewpoints and through these oppositions, innovation can be nurtured. By adhering to the SDG agenda, we present policy advice including new opportunities for vector-borne disease control to reach its own health goals, while simultaneously supporting other sustainable development goals.

Twice upon a time: The progression of canine visceral leishmaniasis in an Argentinean city

Canine Visceral Leishmaniasis (CVL) prevalence, spatial distribution and associated factors were assessed in four locations in Iguazú department in 2014 and in Puerto Iguazú city again in 2018. The city areas were divided into a grid of 400x400m cells. All cells were sampled in 2014 and a random subsampling was developed in 2018. In each cell, five dogs clustered in a 'critical scenario' (prone to have vectors) were sampled. A rapid immunochromatographic dipstick was used to detect antibodies against Leishmania infantum, confirming by lymph node smears observation and PCR. For Puerto Iguazú, Generalized Linear Models (GLMs) were constructed considering environmental, dog and clinical variables. Pearson's Chi square and Fisher's exact tests were employed to evaluate the association between CVL, dog clinical signs and infestation with other parasites. Cartographic outputs were made and Moran's I indices were calculated as spatial autocorrelation indicators. CVL prevalence rates were 26.18% in 2014 and 17.50% in 2018. No associations were established in environmental models, but dog age and repellent use were significant when running 2014 dog models. Clinical models showed significant associations between seropositive dogs and ophthalmological, dermal signs and onychogryphosis in 2014. In 2018, only adenomegaly was associated. The results of global Moran´s I were not significant but regarding local analysis, six sites in 2014 and one in 2018 presented autocorrelation with neighboring sites. The decrease in CVL prevalence may be associated to transmission stabilization, which could explain the lack of associations with dog-related variables. Further, spatial distribution of CVL is a poor evidence for design of transmission control measures but could be important in case of intensive parasite circulation or when the first autochthonous cases appear. For control success, sensitivity of diagnostic methods, political will and adequate material resources remain critical. Modeling of multiple variables will be required to identify factors that drive disease stabilization/destabilization.