Effectiveness of Insecticide Spraying and Culling of Dogs on the Incidence of Leishmania infantum Infection in Humans: A Cluster Randomized Trial in Teresina, Brazil

Background: To evaluate the effect of insecticide spraying for vector control and elimination of infected dogs on the incidence of human infection with L. infantum, a randomized community intervention trial was carried out in the city of Teresina, Brazil. Methods/Principal Findings Within each of ten localities in the city, four blocks were selected and randomized to 4 interventions: 1) spraying houses and animal pens with insecticide; 2) eliminating infected dogs; 3) combination of spraying and eliminating dogs, and 4) nothing. The main outcome is the incidence of infection assessed by the conversion of the Montenegro skin test (MST) after 18 months of follow-up in residents aged ≥1 year with no previous history of visceral leishmaniasis (VL). Reactions were measured at 48–72 h, induration of ≥5 mm considered positive. Interventions were executed after the baseline interview and repeated 6 and 12 months later. The effects of each type of intervention scheme on the incidence of infection were assessed by calculating relative risks and 95% confidence intervals using Poisson population-averaged regression models with robust variance. Among the 1105 participants, 408 (37%) were MST positive at baseline. Of the 697 negatives, only 423 (61%) were reexamined at the end of the follow-up; 151 (36%) of them converted to a positive MST. Only dog culling had some statistically significant effect on reducing the incidence of infection, with estimates of effectiveness varying between 27% and 52%, depending on the type of analysis performed. Conclusions/Significance: In light of the continuous spread of VL in Brazil despite the large scale deployment of insecticide spraying and dog culling, the relatively low to moderate effectiveness of dog culling and the non-significant effect of insecticide spraying on the incidence of human infection, we conclude that there is an urgent need for revision of the Brazilian VL control program

The performance of serological tests for Leishmania infantum infection screening in dogs depends on the prevalence of the disease

Dogs are considered the main reservoir of Leishmania infantum. This protozoan causes visceral leishmaniasis (VL), an uncontrolled urban zoonosis in Brazil. Serological tests and polymerase chain reaction (PCR) on peripheral blood were performed to identify infected dogs in scenarios of higher and lower prevalence of the disease (Teresina and Vitória). One-hundred infected and 57 non-infected animals from Teresina and 100 non-infected animals from Vitória were studied. Animal selection was not dependent on previous serology. The sensitivity (Teresina) and specificity (Teresina and Vitória) were as follows: indirect antibody fluorescence (IFAT) cut-off of 1:40 (IFAT 1:40): 96%, 18%, and 76%; IFAT 1:80: 90%, 33%, and 93%; direct agglutination test (DAT): 96%, 33%, and 98%; fast agglutination screening test (FAST): 93%, 68%, and 100%; immunochromatographic assay with a recombinant rK39 antigen (rK39): 88%, 74%, and 98%; enzyme linked immunosorbent assay (ELISA): 91%, 79%, and 98%; rapid dual-path platform test (TR DPP®): 98%, 60%, and 98%; and blood PCR: 29%, 93%, and 97%, respectively. In the high transmission area, none of the tests adequately discriminated L. infantum-infected from non-infected dogs. However, in the high transmission city, the area under the receiver operating characteristic (ROC) curve of FAST, DAT, ICrK39, ELISA and TR DPP® was high

Leishmaniose Visceral: há possibilidade de transmissão sexual e vertical entre cães?

A leishmaniose visceral (LV) é uma enfermidade cosmopolita, grave e de alta letalidade em seres humanos, sendo considerada uma zoonose negligenciada. Nas Américas, a sua ocorrência está diretamente ligada com a presença do inseto vetor, principalmente relacionada à fêmea da espécie de flebotomíneo Lutzomyia longipalpis. Entretanto, em alguns estudos foram observados casos da doença em humanos e cães, com ocorrências em locais livres do vetor, indicando para a possibilidade de outras formas de transmissão, como a sexual e a vertical. O objetivo desse trabalho foi realizar uma revisão de literatura com o intuito de descrever sobre os principais aspectos relacionados com a transmissão sexual e vertical entre cães, proporcionando, assim, uma melhor compreensão da epidemiologia da doença, principalmente em áreas endêmicas. Atualmente, a possibilidade de transmissão sexual e vertical nessa espécie animal vem sendo bastante explorada, em que as pesquisas visam buscar a presença do protozoário Leishmania (L.) infantum nos órgãos do sistema reprodutivo, tanto de fêmeas quanto de machos caninos, bem como a presença do DNA do parasito no esmegma e sêmen. Dessa forma, a literatura aponta que essas formas de transmissão na LV provavelmente ocorrem em cães

Improving the serodiagnosis of canine Leishmania infantum infection in geographical areas of Brazil with different disease prevalence

Serodiagnosis of Leishmania infantum infection in dogs relies on the detection of antibodies against leishmanial crude extracts or parasitic defined antigens. The expansion of canine leishmaniasis from geographical areas of Brazil in which the infection is endemic to regions in which the disease is emerging is occurring. This fact makes necessary the analysis of the serodiagnostic capabilities of different leishmanial preparations in distinct geographical locations. In this article sera from dogs infected with Leishmania and showing the clinical form of the disease, were collected in three distinct Brazilian States and were tested against soluble leishmanial antigens or seven parasite individual antigens produced as recombinant proteins. We show that the recognition of soluble leishmanial antigens by sera from these animals was influenced by the geographical location of the infected dogs. Efficacy of the diagnosis based on this crude parasite preparation was higher in newly endemic regions when compared with areas of high disease endemicity. We also show that the use of three of the recombinant proteins, namely parasite surface kinetoplastid membrane protein of 11 kDa (KMP-11), and two members of the P protein family (P2a and P0), can improve the degree of sensitivity without adversely affecting the specificity of the diagnostic assays for canine leishmaniasis, independently of the geographical area of residence. In addition, sera from dogs clinically healthy but infected were also assayed with some of the antigen preparations. We demonstrate that the use of these proteins can help to the serodiagnosis of Leishmania infected animals with subclinical infections. Finally, we propose a diagnostic protocol using a combination of KMP-11, P2a y P0, together with total leishmanial extractsThis work was supported by the Conselho Nacional de Desenvolvimento Científico e Tecnológico (Brazil) within the call“CNPq/MS/SCTIE/DECIT N° 32/2014 - Pesquisas sobre Leishmanioses”grant number reference 467389/2014-4. Institutional grants from the Fundación Ramón Areces and Banco de Santander to the CBMSO are also acknowledged. TC received scholarship from Fundação de Amparo a Pesquisa do Estado de Santa Catarina–FAPES

Impact of 4% Deltamethrin-Impregnated Dog Collars on the Incidence of Human Visceral Leishmaniasis: A Community Intervention Trial in Brazil

Background: In Brazil, human visceral leishmaniasis (HVL) is caused by the protozoan parasite Leishmania infantum, primarily transmitted by the sand fly Lutzomyia longipalpis, with dogs acting as the main urban reservoir. This study aims to evaluate the effectiveness of 4% deltamethrin-impregnated dog collars (DMC) on HVL incidence. Methods: This is a community intervention study carried out from 2012 to 2015 in the municipalities of Araguaína, State of Tocantins, and Montes Claros, State of Minas Gerais, Brazil. Two areas in each were randomly allocated to either (1) culling seropositive dogs + residual insecticide spraying (control area—CA) or (2) culling seropositive dogs + residual insecticide spraying + DMC fitted to dogs every six months for two years (intervention area—IA). Cases of HVL (n = 1202) occurring from 2008 to 2020 were identified from the Brazilian Reportable Diseases Information System and georeferenced to the control and intervention areas. The HVL cases from 2008 to 2012 were considered as occurring in the “pre-intervention” period. Those cases from 2013 to 2016 and from 2017 to 2020 were regarded as occurring in the “intervention” and “post-intervention” periods, respectively. We used a mixed-effects Poisson regression model to estimate the effectiveness of the intervention, comparing the changes from the pre-intervention period to the intervention and post-intervention periods in the control and intervention areas. Results: In Araguaína, there was a statistically significant reduction in the incidence of HVL in both the control and intervention areas, comparing both the intervention and post-intervention periods with the pre-intervention period. The intervention with DMC was significantly associated with a reduction in HVL when comparing the intervention and pre-intervention periods, yielding an effectiveness estimate of the DMC of 27% (IC95% 1–46%, p = 0.045). No differences were observed when comparing the pre- and post-intervention periods (p = 0.827). In Montes Claros, cases reduced in both the control and intervention areas from the pre-intervention period to the intervention period (p = 0.913). In the post-intervention period, the incidence increased in the control area, while cases continued to decrease in the DMC area (p = 0.188). Conclusions: The use of DMC was associated with a reduction of 27% in the incidence of HVL during the period of DMC delivery, indicating that DMC is effective as an additional strategy for controlling visceral leishmaniasis in Brazil. However, no significant reduction associated with DMC was detected after the intervention period, suggesting that a control program based on the large-scale deployment of DMC might have to be maintained for more extended periods without interruption

Cellular immune response in popliteal lymph nodes and liver of dogs with visceral leishmaniasis

Canine visceral leishmaniasis (CVL) is a zoonosis caused by Leishmania (Leishmania) infantum chagasi in the American continent. There are few studies detailing the immunopathological characteristics in lymph nodes and liver in infected dogs in endemic area from Teresina city, Piauí State, Brazil. Thus, we have evaluated histopathological changes and the presence of CD4+ and CD8+ T cells in popliteal lymph nodes and liver of nine dogs with clinical manifestation (G1) and seven dogs without clinical manifestation (G2) naturally infected with L. (L.) infantum chagasi. Histopathological and immunohistochemical analysis were performed on samples liver and lymph nodes tissues. The important clinical changes were lymphadenopathy (80%) and skin lesions (70%). Histopathological analysis of the popliteal lymph node revealed higher depletion cell of the paracortical region. The number of CD4+ and CD8+ T cells was no significant between the groups but there was positive correlation between CD4+ and CD8+ T cells in G1 and G2. In the liver, the inflammatory infiltrate was focal consisting of mononuclear cell in the periportal and intralobular regions, in both groups. Inflammatory infiltrate of mononuclear cells showed positive staining for CD4 and CD8 T cells but there was no significant difference between groups. However, there was a positive correlation between CD4+ and CD8+ T cells in the G1. Immunoperoxidase analysis also revealed more amastigotes and antigen of Leishmania in G1 in liver and lymph nodes than in G2. The role of CD4+ and CD8+ T cells seems is not related to the clinical status of dogs with CVL.Leishmaniose visceral canina (LVC) é uma zoonose causada por Leishmania (Leishmania) infantum chagasi no continente Americano. Poucos estudos demonstraram as características imunopatológicas em linfonodo poplíteo e fígado de cães infectados em área endêmica de Teresina, Piauí, Brasil. Assim, nós avaliamos as alterações histopatológicas e a presença de células T CD4+ e CD8+ em linfonodo poplíteo e fígado de nove cães com manifestações clínicas (G1) e sete cães sem manifestações clínicas (G2) naturalmente infectados com L. (L.) infantum chagasi. Fragmentos de linfonodo poplíteo e fígado foram obtidos para análise histopatológica e imunoistoquímica. As principais manifestações clínicas foram linfadenopatia (80%) e lesões de pele (70%). Na análise histopatológica do linfonodo foi observada uma depleção de células da região cortical. Não havia diferença significante entre os grupos entre células T CD4+ e CD8+ mas havia uma correlação positiva entre essas células em G1 e G2. No fígado, o infiltrado inflamatório era focal consistindo de células mononucleares nas regiões periportal e intralobular, em ambos os grupos. O infiltrado inflamatório era positivo na imunomarcação para células T CD4 e CD8, mas sem diferença significante entre os grupos. Entretanto, havia uma correlação positiva entre as células T CD4+ e CD8+ no G1. Na análise da imunomarcação também mostrou mais amastigotas e antígenos de Leishmania no fígado e linfonodo poplíteo em G1 em relação ao G2. O papel das células T CD4+ e CD8+ parece não estar relacionada ao estado clínico dos cães com LVC