How effective is dog culling in controlling zoonotic visceral leishmaniasis? a critical evaluation of the science, politics and ethics behind this public health policy

Transmission-Blocking Vaccines for Canine Visceral Leishmaniasis: New Progress and Yet New Challenges

Dogs with visceral leishmaniasis play a key role in the transmission cycle of Leishmania infantum to humans in the urban environment. There is a consensus regarding the importance of developing a vaccine to control this disease. Despite many efforts to develop a protective vaccine against CVL, the ones currently available, Leish-tec® and LetiFend®, have limited effectiveness. This is due, in part, to the complexity of the immune response of the naturally infected dogs against the parasite and the complexity of the parasite transmission cycle. Thus, strategies, such as the development of a transmission-blocking vaccines (TBVs) already being applied to other vector-borne diseases like malaria and dengue, would be an attractive alternative to control leishmaniasis. TBVs induce the production of antibodies in the vertebrate host, which can inhibit parasite development in the vector and/or interfere with aspects of vector biology, leading to an interruption of parasite transmission. To date, there are few TBV studies for CVL and other leishmaniasis forms. However, the few studies that exist show promising results, thus justifying the further development of this approach.

The Program for the Control of Visceral Leishmaniasis in Brazil: The Effect of the Systematic Euthanasia of Seropositive Dogs as a Single Control Action in Porteirinha, a Brazilian City with an Intense Transmission of Visceral Leishmaniasis

BACKGROUND

Porteirinha is endemic for visceral leishmaniasis (VL), with intense disease transmission of the disease. We evaluated the impact of canine euthanasia as a single control measure on the incidence of VL in humans and canines.

METHODS

A prospective observational cohort study was carried out over four years (1998-2002) in 8 of the 12 neighborhoods of the city. The dynamics of canine visceral leishmaniasis (CVL) transmission were evaluated for 2 years, before beginning the screening-culling intervention. The comparative morbidity index (CMI) was used to stratify areas with the greatest risk of CVL, and the spatial distribution of human and canine VL cases was compared using univariate and bivariate K-functions.

RESULTS

Human cases conglomerated in three neighborhoods. Spatial clusters were detected for CVL in 1998, 2000, and 2001, but not in 1999, when greater spatial dispersion occurred. The screening and culling intervention reduced the number of human VL cases and decreased the incidence of CVL, mainly in neighborhoods with a high CMI.

CONCLUSIONS

The systematic euthanasia of seropositive dogs was shown to be an effective control action of the Program for Control of Visceral Leishmaniasis (PCLV) in Brazil. The fundamental role of domestic dogs in the epidemiological chain of VL was reaffirmed.

Evidence map of diagnosis, treatment, prognosis, prevention, and control in visceral leishmaniasis

Objective.

To develop an evidence map on visceral leishmaniasis prevention, control, diagnosis, treatment, and prognosis.

Methods.

Systematic reviews on visceral leishmaniasis were searched using MEDLINE/PubMed and Virtual Health Library. After selection, each included systematic review was assessed, characterized, and categorized by intervention type and by outcomes, according to the methodology offered by the PAHO/WHO Latin American and Caribbean Center on Health Sciences Information (BIREME). The methodological quality was assessed using the AMSTAR2 tool to determine the confidence level of the evidence obtained.

Results.

Among the prevention and control interventions, insecticide spraying, bednets, dog collars, and dog culling were the most assessed, emphasizing that insecticidal dog collars can reduce visceral leishmaniasis incidence in dogs. Regarding diagnosis, polymerase chain reaction (PCR), rK39 immunochromatographic test (rK39 ICT), and direct agglutination test (DAT) presented high sensitivity and specificity. As for treatment, pentavalent antimonials and amphotericin B were the most analyzed drugs and showed therapeutic success; however, serious adverse events can occur due to their use. The prognostic factors identified were anemia, edema, bleeding, jaundice, age, and HIV coinfection.

Conclusions.

The evidence map developed shows rK39 ICT and DAT as promising diagnostic alternatives and reinforces the efficacy of liposomal amphotericin B and pentavalent antimonials. Insecticide-impregnated dog collars appear as a promising measure for the control of visceral leishmaniasis, but there is also a need for future studies and reviews with higher methodological quality, especially on prevention and control interventions.

Antileishmanial Drug Discovery and Development: Time to Reset the Model?

Leishmaniasis is a vector-borne parasitic disease caused by Leishmania species. The disease affects humans and animals, particularly dogs, provoking cutaneous, mucocutaneous, or visceral processes depending on the Leishmania sp. and the host immune response. No vaccine for humans is available, and the control relies mainly on chemotherapy. However, currently used drugs are old, some are toxic, and the safer presentations are largely unaffordable by the most severely affected human populations. Moreover, its efficacy has shortcomings, and it has been challenged by the growing reports of resistance and therapeutic failure. This manuscript presents an overview of the currently used drugs, the prevailing model to develop new antileishmanial drugs and its low efficiency, and the impact of deconstruction of the drug pipeline on the high failure rate of potential drugs. To improve the predictive value of preclinical research in the chemotherapy of leishmaniasis, several proposals are presented to circumvent critical hurdles-namely, lack of common goals of collaborative research, particularly in public-private partnership; fragmented efforts; use of inadequate surrogate models, especially for in vivo trials; shortcomings of target product profile (TPP) guides.

FML/QuilA-Vaccinated Dogs Naturally Infected with Leishmania infantum: Serum Cytokines, Clinicopathological Profile, and Parasitological Parameters

Dogs are the main reservoir of Leishmania infantum in endemic regions. Canine leishmaniasis, caused by L. infantum, can progress to a chronic disease resulting in death. Vaccines have been developed with a certain degree of success. The pathogenesis of this disease is not completely understood, especially in previously vaccinated dogs. We herein described clinical data, parasite load, serum levels of cytokines, and the reservoir potential in vdogs vaccinated with the fucose-mannose ligand (FML)/QuilA saponin vaccine (Leishmune™) naturally infected (Vi) and compared to vaccinated not infected dogs (Vn). Thirty-four dogs from private owners were divided into two groups: vaccinated/infected and vaccinated/uninfected. Clinical evaluation, hematological and biochemical parameters, and serum levels of cytokines were measured by conventional methods. The parasite burden in the bone marrow was measured by quantitative real-time PCR, and the transmissibility of parasites to sand flies was assessed by xenodiagnosis. Clinical, biochemical, and hematological parameters of vaccinated infected dogs were mostly normal. Vi dogs developed mild disease with low clinical scores. Serum levels of IL-10 were higher in Vi dogs, and a strong correlation was observed in IL-4 levels and the A/G ratio in Vi dogs. These results suggest a role of TH2 response in Vi dogs, although more data is needed to better understand the disease in vaccinated dogs.

A chimeric vaccine combined with adjuvant system induces immunogenicity and protection against visceral leishmaniasis in BALB/c mice

In Brazil, canine visceral leishmaniasis is an important public health problem due to its alarming growth. The high prevalence of infected dogs reinforces the need for a vaccine for use in prophylactic vaccination campaigns. In the present study, we evaluate the immunogenicity and protection of the best dose of Chimera A selected through the screening of cytokines production important in disease. BALB/c mice were vaccinated subcutaneously with three doses and challenged intravenously with 1 × 10⁷L. infantum promastigotes. Spleen samples were collected to assess the intracellular cytokine profile production, T cell proliferation and parasite load. At first, three different doses of Chimera A (5 μg, 10 μg and 20 μg) were evaluated through the production of IFN-γ and IL-10 cytokines. Since the dose of 20 μg showed the best results, it was chosen to continue the study. Secondarily, Chimera A at dose of 20 μg was formulated with Saponin plus Monophosphoryl lipid A. Vaccination with Chimera A alone and formulated with SM adjuvant system was able to increase the percentage of the proliferation of specific T lymphocytes and stimulated a Th1 response with increased levels of IFN-γ, TNF-α and IL-2, and decreased of IL-4 and IL-10. The vaccine efficacy through real-time PCR demonstrated a reduction in the splenic parasite load in animals that received Chimera A formulated with the SM adjuvant system (92%). Additionally, we observed increased levels of nitric oxide in stimulated-culture supernatants. The Chimera A formulated with the SM adjuvant system was potentially immunogenic, being able to induce immunoprotective mechanisms and reduce parasite load. Therefore, the use of T-cell multi-epitope vaccine is promising against visceral leishmaniasis.

The efficacy of recombinant protein lbk39 for the diagnosis of leishmaniosis in dogs

Visceral leishmaniosis is one of the most important zoonotic diseases on the planet and dogs are the main reservoir of canine visceral leishmaniosis (CVL) in endemic areas. They play an important role in human infection because in dogs the disease appears long time after infection, and they can move uncontrollably, contributing to disperse the parasite. To take the decision to treat the animals or for euthanasia, in an elimination programme, in order to reduce the parasitic load, it is necessary to diagnose correctly, having more effective tools. Our group has developed a new recombinant antigen-based kinesin-related gene of Leishmania braziliensis (Lbk39), which shows 59% amino acid identity to the L. infantum homologue. The Lbk39 gene was synthesized, inserted into the pLEXSY-sat2 vector and transfected into L. tarentolae cells by electroporation. The recombinant protein was secreted in the culture with a C-terminal histidine marker, purified, generating a product at 337.68 μg mL-1. A total of 152 sera from dog's endemic and non-endemic areas were used, being 78 positives and 75 negatives. The antigen Lbk39 showed 100% sensitivity and 96.1% specificity. We compared this antigen with other antigens such as total extract of the parasite, TRDPP, and our data indicate that Lbk39 has potential application in the diagnosis of CVL through antibody detection.

Immunoprophylactic Potential of a New Recombinant Leishmania infantum Antigen for Canine Visceral Leishmaniasis: An In Vitro Finding

The development and application of safe and effective immunoprophylactic/immunotherapeutic agents against canine visceral leishmaniasis (CanL) have been pointed out as the only means for the real control of the disease. Thus, this study aimed to evaluate the in vitro cellular immune response of dogs, elicited by the new recombinant proteins of Leishmania infantum, Lci10 and Lci13, in order to investigate their potential for vaccinology. Twenty-four dogs were submitted to clinical, parasitological, serological and molecular tests, and then separated into two study groups: 12 infected (InD) and 12 non-infected dogs (NInD), and six of each group were directed for Lci10 and Lci13 evaluation. Peripheral blood mononuclear cells (PBMC) were cultured and stimulated with Lci10 (10 μg/ml) or Lci13 (5 μg/ml), and with L. infantum soluble antigen (LSA) (25 μg/ml) or no stimulus (NS) as controls. Afterwards, the mRNA levels of different cytokines were quantified through qPCR, and Nitric Oxide (NO) production was assessed in the culture supernatants. Significant differences were considered when p ≤ 0.05. The comparative analysis revealed that, in the NInD group, Lci13 promoted a significant increase in the expression of IFN-γ in relation to LSA (p = 0.0362), and the expression of this cytokine in NInD was significantly higher than that presented in the InD (p = 0.0028). A negative expression for TGF-β was obtained in both groups. Lci13 also induced a greater production of NO in relation to the NS sample in the NInD group. No significant differences were observed after stimulation with Lci10. In conclusion, the results suggest a protective role of Lci13 for uninfected animals, thus with a potential for immunoprophylaxis. The results will help to direct the antigen Lci13 for further studies (pre-clinical trials), in order to determine its immunogenicity and reactogenicity effects, as a way to consolidate its real applicability for vaccinology against CanL.

Insecticide-impregnated netting: A surface treatment for killing Lutzomyia longipalpis (Diptera: Psychodidae), the vector of Leishmania infantum

The sand fly Lutzomyia longipalpis is the main vector of Leishmania infantum in Brazil. Synthetic male-produced sex/aggregation pheromone co-located with micro-encapsulated λ-cyhalothrin in chicken sheds can significantly reduce canine infection and sand fly densities in a lure-and-kill strategy. In this study, we determined if insecticide-impregnated netting (IN) could replace insecticide residual spraying (IRS). We compared numbers of Lu. longipalpis attracted and killed in experimental and real chicken sheds baited with pheromone and treated with a 1 m² area of either insecticide spray or netting. First, we compared both treatments in experimental sheds to control mortality established from light trap captures. We then compared the long-term killing effect of insecticide spray and netting, without renewal, in experimental sheds over a period of 16 weeks. Finally, a longitudinal intervention study in real chicken sheds compared the numbers and proportions of Lu. longipalpis collected and killed before and after application of both treatments. In Experiment 1, a higher proportion of males and females captured in IRS- and IN-treated sheds were dead at 24 h compared to controls (P < 0.05). No difference was found in the proportion of females killed in sheds treated with IN or IRS (P = 0.15). A slightly higher proportion of males were killed by IRS (100%) compared to IN (98.6%; P < 0.05). In Experiment 2, IN- and IRS-treated traps were equally effective at killing females (P = 0.21) and males (P = 0.08). However, IRS killed a significantly higher proportion of females and males after 8 (P < 0.05) and 16 (P < 0.05) weeks. In Experiment 3, there was no significant difference between treatments in the proportion of females killed before (P = 0.88) or after (P = 0.29) or males killed before (P = 0.76) or after (P = 0.73) intervention. Overall, initially the IN was as effective as IRS at killing female and male Lu. longipalpis in both experimental and real chicken sheds. However, the relative lethal effect of the IN deteriorated over time when stored under prevailing environmental conditions.

•

Chicken sheds treated with netting or spray insecticide killed Lutzomyia longipalpis.

•

Same effect was seen in experimental and real chicken sheds.

•

Netting was as effective as spraying insecticide initially.

•

Sprayed insecticide killed a higher proportion of both sexes after 8 and 16 weeks.

•

The relative lethal effect of the netting deteriorated over time.

Level of Knowledge and Risk Factors for Visceral Leishmaniasis in a Mining Area of Minas Gerais State, Brazil

Aiming to optimize and adjust leishmaniasis prevention and control measures for the resident population of Pains, state of Minas Gerais, Brazil, a structured questionnaire containing conceptual questions and questions about household characteristics was used to evaluate knowledge level and exposure risk. A total of 396 individuals were interviewed revealing unscientific and fragmented knowledge about the subject for most of the studied population. The female population was found to have 1.68 times more chance of knowing about the disease than the male population, while highly educated individuals were found to have 2.92 times more chances of knowing about leishmaniasis compared to basic educated individuals. All of the respondents reported the presence of, at least, one risk factor, while ages ≥40 years were considered a protective factor compared to younger ages, indicating that older individuals are more likely to recognize risks and protect themselves against leishmaniasis. These results will contribute to the production of didactic materials for the population with respect to their previous knowledge and will provide a basis for control and prophylactic measures.

Impact of different Leishmania reservoirs on sand fly transmission: Perspectives from xenodiagnosis and other one health observations

Leishmania has biologically adapted to specific phlebotomine sand flies through long co-evolution. The ability of Leishmania spp. to bind to sand fly midgut allows each Leishmania species to propagate and differentiate into infectious promastigotes and be transmitted. Sand fly feeding upon a mammalian host is the first step towards being infected and a host of Leishmania. Once deposited into the skin, host susceptibility to infection vs. ability to mount a sterilizing immune response predicts which hosts could be reservoirs of different Leishmania spp. Materials, in addition to parasites, are expelled during sand fly during feeding, including salivary antigens and other factors that promote local inflammatory responses. These factors aid visceralization of infection increasing the likelihood that systemic infection is established. Any environmental factor that increases sand fly biting of a particular host increases that host's role in Leishmania transmission. First descriptions of reservoir species were based on association with local human disease and ability to observe infected leukocytes on cytology. This approach was one pathogen for one reservoir host. Advances in sensitive molecular tools greatly increased the breadth of mammals found to host Leishmania infection. Visceralizing species of Leishmania, particularly L. infantum, are now known to have multiple mammalian hosts. L. donovani, long been described as an anthroponotic parasite, was recently identified through molecular and serologic surveys to have additional mammalian hosts. The epidemiological role of these animals as a source of parasites to additional hosts via vector transmission is not known. Current evidence suggests that dogs and other domestic animals either control infection or do not have sufficient skin parasitemia to be a source of L. donovani to P. argentipes. Further xenodiagnosis and characterization of skin parasitemia in these different hosts is required to more broadly understand which Leishmania spp. hosts can be a source of parasites to sand flies and which ones are dead-end hosts.

Canine visceral leishmaniasis in area with recent Leishmania transmission: prevalence, diagnosis, and molecular identification of the infecting species

INTRODUCTION:

Canine visceral leishmaniasis (CVL) is an endemic disease in Brazil, and integrated control actions have been adopted by the Brazilian Ministry of Health to control its spread. However, the transmission profile is unknown in areas with recent CVL cases, including Itaúna, located in the Brazilian state of Minas Gerais, where the present study was carried out.

METHODS:

A total of 2,302 dogs from 12 neighborhoods were serologically tested for canine VL using the current diagnostic protocol adopted by the Brazilian Ministry of Health. Test positivity rate (TPR) and CVL prevalence were determined for each neighborhood. The presence of Leishmania was assessed in 60 seropositive dogs which had been recommended for euthanasia. Twenty-two of them (37%) were asymptomatic, and 38 (63%) were symptomatic for CVL. Parasitological (myeloculture and smear/imprint) and molecular (PCR) methods were employed for Leishmania detection in bone marrow, spleen, mesenteric lymph nodes, and ear skin. The infecting Leishmania species was identified by DNA sequencing.

RESULTS:

CVL prevalence (per 1,000 dogs) varied from 0.0-166.67, depending on the neighborhood, with a mean of 68.96 (SD 51.38). Leishmania DNA was detected in at least one tissue from all seropositive dogs, with comparable TPR among tissues. Leishmania parasites were identified in most (54/60) seropositive dogs, and the infecting parasite was identified as Leishmania infantum in all of these.

CONCLUSIONS:

Prevalence of CVL is a contributor to the spread of visceral leishmaniasis in Itaúna.

Tanatopolítica e biossegurança: dois regimes de governo da vida para a leishmaniose visceral canina no Brasil

Resumo Apesar de ter sua legitimidade contestada nas últimas décadas por defensores de animais, juristas e veterinários que defendem o direito à vida e ao tratamento, assim como por pesquisadores da área da saúde que duvidam de sua eficácia, a “eutanásia profilática” massiva de cães testados como soropositivos para leishmaniose visceral mantém-se firme como política sanitária no Brasil. A partir da análise de documentos oficiais, revisão da literatura, comentários sobre processos judiciais colhidos na imprensa e da etnografia dos impactos do surto de leishmaniose visceral em Porto Alegre, este artigo visa compreender o que está em jogo nessa controvérsia, considerando seus aspectos discursivos na construção de moralidades e práticas biopolíticas. Sugere-se a existência de dois regimes de governo da vida na gestão dos reservatórios caninos da leishmaniose visceral: um tanatopolítico, ligado ao poder público; o outro, um dispositivo emergente de biossegurança, ligado ao mercado farmacêutico e acessível apenas para tratamento privado.

Effectiveness of insecticide-impregnated collars for the control of canine visceral leishmaniasis

Visceral leishmaniasis is a neglected tropical disease widely distributed worldwide. In Brazil, the control measures adopted in the last decades have not been able to prevent the spread of the disease. This study aimed to evaluate the effectiveness of a population-based intervention using 4% deltamethrin-impregnated dog collars on the incidence of canine visceral leishmaniasis. A community intervention study was carried out in two areas of the city of Montes Claros, State of Minas Gerais, Brazil. In the control area, the preventive measures recommended by the Brazilian Program for Surveillance and Control of Visceral Leishmaniasis were implemented (culling of infected dogs and vector control with residual insecticides). In the intervention area, deltamethrin-impregnated collars were fit to domiciled dogs, in addition to the above mentioned preventive measures. At the beginning of the study, a census survey was carried out among domiciled dogs to detect the prevalence of L. infantum infection. Dogs found seronegative at recruitment were longitudinally followed-up to evaluate the incidence of infection. Monitoring of canine infection (control and intervention areas) and replacement of collars (intervention area) occurred through sequential surveys at 12, 18, and 24 months after the initial survey. At each survey, dogs were tested, and the owner answered a questionnaire about the general characteristics of the animal. Multilevel logistic regression models were used to test the effect of collars on the risk of canine infection, with households considered as aggregation units. Associations were expressed as odds ratios (OR) and respective 95% confidence intervals (95%CI). The prevalence of infection in the initial survey was 9.7% and 9.9% in the intervention and control areas, respectively (p = 0.732). Among a total of 20,477 dogs participating in the study, 9,770 were seronegative at recruitment. The cumulative incidence of infection was 4.1% in the intervention area and 7.9% in the control area (p < 0.001). In the multivariable analysis, the risk of infection was 52% lower in the intervention area as compared to the control area (OR = 0.48, 95%CI:0.39-0.59), after adjusting for the number of dogs in the house, period of recruitment, time of dog ownership, and age, sex, length of fur and breed. The use of 4% deltamethrin-impregnated dog collars was effective in reducing the incidence of canine leishmaniasis. Cost-effectiveness studies are recommended before the incorporation of collars in the arsenal of control measures of the Brazilian Program for Surveillance and Control of Visceral Leishmaniasis.

Canine serological survey and dog culling ant its relationship with human visceral leishmaniasis in an endemic urban area

BACKGROUND

Visceral leishmaniasis is an important but neglected disease that is spreading and is highly lethal when left untreated. This study sought to measure the Leishmania infantum seroprevalence in dogs, the coverage of its control activities (identification of the canine reservoir by serological survey, dog culling and insecticide spraying) and to evaluate its relationship with the occurrence of the disease in humans in the municipalities of Araçatuba and Birigui, state of São Paulo, Brazil.

METHODS

Information from 2006 to 2015 was georeferenced for each municipality and modeling was performed for the two municipalities together. To do this, latent Gaussian Bayesian models with the incorporation of a spatio-temporal structure and Poisson distribution were used. The Besag-York-Mollie models were applied for random spatial effects, as also were autoregressive models of order 1 for random temporal effects. The modeling was performed using the INLA (Integrated Nested Laplace Approximations) deterministic approach, considering both the numbers of cases as well as the coverage paired year by year and lagged at one and two years.

RESULTS

Control activity coverage was observed to be generally low. The behavior of the temporal tendency in the human disease presented distinct patterns in the two municipalities, however, in both the tendency was to decline. The canine serological survey presented as a protective factor only in the two-year lag model.

CONCLUSIONS

The canine serological coverage, even at low intensity, carried out jointly with the culling of the positive dogs, suggested a decreasing effect on the occurrence of the disease in humans, whose effects would be seen two years after it was carried out.

Canine Leishmaniasis Control in the Context of One Health

Dogs are the main reservoir of Leishmania infantum and in some countries have been regularly culled as part of government policy to control visceral leishmaniasis. At the 13th Symposium of the Companion Vector-Borne Diseases World Forum in Windsor, UK, March 19–22, 2018, we consolidated a consensus statement regarding the usefulness of dog culling as a means of controlling visceral leishmaniasis. The statement highlighted the futility of culling infected dogs, whether healthy or sick, as a measure to control the domestic reservoir of L. infantum and reduce the risk for visceral leishmaniasis.

Canine vector-borne pathogens from dogs and ticks from Tamil Nadu, India

Canine vector-borne diseases (CVBDs) pose a major health problem in dogs globally, with the potential to cause zoonoses, in particular in developing countries where scientific knowledge on the topic is minimal. Blood samples and ticks were collected from stray dogs in Tamil Nadu, South India to assess the prevalence of CVBD-causing pathogens (Anaplasma spp., Babesia spp., Ehrlichia spp., Hepatozoon spp., filarioids and Leishmania spp.). Of the 230 dogs examined, 229 (99.6%) were infested by ticks (mean intensity, 5.65) with Rhipicephalus sanguineus sensu lato and Rhipicephalus haemaphysaloides being morphologically identified in the 98.3% and 1.7% of the infested dogs, respectively. Overall, the 67.8% (n = 156) of dogs was positive for at least one pathogen with Hepatozoon canis being the most prevalent (37.8%) followed by Anaplasma platys (22.6%), Ehrlichia canis (16.1%) Babesia vogeli (10%), Anaplasma phagocytophilum (0.4%) and Babesia gibsoni (0.4%). Two filarioids (Dirofilaria sp. "hongkongensis" and Brugia malayi, 0.4%) were diagnosed in sampled animals. Co-infection with H. canis and A. platys was the most prevalent (8.3%, P = 0.00001), whilst all animals scored negative for Leishmania spp.. Out of 295 ticks analysed, 215 R. sanguineus s.l. (75.4%) and 8 R. haemaphysaloides (88.9%) were positive for at least one pathogen with H. canis as the predominant species (42.5%), followed by A. platys (33.8%), E. canis (16.9%), B. vogeli (3.8%) and A. phagocytophilum (0.3%). Fifty-six dogs (35.9%) harboured the same pathogen as the respective tick specimens, while 29 dogs (18.6%) had a different pathogen. Thirteen sequence types (STs) were identified for H. canis, with ST2 (49.4%) as the most representative in dogs and ST1 (73.5%) in ticks. Similarly, seven STs were found for Anaplasma spp. (i.e., five for A. platys, one for A. phagocytophilum and one for Anaplasma sp.), with ST2 as the most representative in dogs (70.6%) and ST3 (52.5%) in ticks for A. platys. Only one ST was identified for B. vogeli, B. gibsoni, E. canis, D. sp. "hongkongensis" and B. malayi. Regular surveillance and adoption of adequate treatment and control measures are needed to reduce the risk of disease-causing pathogens in stray dogs and of pathogens with zoonotic potential.

Dogs with divergent serology for visceral leishmaniasis as sources of Leishmania infection for Lutzomyia longipalpis phlebotomine sand flies - an observational study in an endemic area in Brazil

Visceral leishmaniasis (VL) is a neglected tropical disease, caused by Leishmania (Kinetoplastida, Trypanosomatidae) species. In Brazil, the transmission of this parasite essentially occurs through the bite of Lutzomyia longipalpis (Diptera: Psychodidae: Phlebotominae) previously infected with Leishmania infantum. Aiming at preventing VL expansion over the country, integrated control actions have been implemented through a Visceral Leishmaniasis Surveillance and Control Program (VLSCP). Among the actions currently adopted by the program, the screening-culling of seropositive dogs for canine VL (CVL) is particularly polemic. Dogs with negative or divergent serology for CVL remain in their owner’s domicile and are monitored by public health agents. In the present study, we determined the prevalence of CVL and analyzed the implementation of the VLSCP screening-culling action, in an area in Brazil where there has been a recent expansion of VL. Canine census surveys were conducted semiannually for two years (Aug/2015 to Feb/2017). Serological diagnosis of CVL was performed in accordance with current VLSCP protocol: immunochromatography (TR-DPP) followed by enzyme-linked immunosorbent assay (ELISA EIE). 6,667 dogs were serologically screened for CVL, of which 567 (8.5%) were positive in both tests and 641 (9.6%) had divergent results. A variable percentage (6.3% to 65.4%) of the dogs in the latter group became positive within nine months from the first result. Xenodiagnosis was conducted in canine samples belonging to any of the three possible serological statuses for CVL–positive, divergent or negative. Leishmania spp. DNA was detected in Lu. longipalpis that fed on 50.0% (5/10) of dogs with positive serology and on 29.4% (5/17) of dogs with divergent serological status for CVL. Therefore, dogs with divergent serology for CVL may be as Leishmania-infective to Lu. longipalpis as seropositive ones. Even with the adoption of euthanasia for seropositive dogs, part of the canine population will continue to serve as a source of Leishmania infection for phlebotomine sand flies.

Visceral leishmaniasis (VL) is a neglected tropical disease caused by a protozoan of the genus Leishmania. In Brazil, the parasites are mainly transmitted through the bite of female Lutzomyia longipalpis sand flies that have been previously infected with Leishmania infantum. Dogs are the main domestic reservoirs of Leishmania. The Brazilian Ministry of Health has implemented euthanasia of VL-seropositive dogs as a measure to prevent VL expansion in the country, using the Dual-Path Platform Immunochromatographic Rapid Test (TR-DPP) as the screening method and the enzyme-linked immunoassay (ELISA EIE) as the confirmatory test for diagnosis. Dogs with positive results in both tests are considered seropositive and recommended for euthanasia. Dogs with divergent serology between these tests remain at their owners’ home and part of them become seropositive within months. Therefore, even adopting euthanasia of seropositive dogs, part of the canine population will continue to serve as a source of Leishmania infection for sand flies, causing new canine and / or human cases of the disease. Difficulties and limitations to implement the screening-culling policy are also discussed.

Recombinant Leishmania eukaryotic elongation factor-1 beta protein: A potential diagnostic antigen to detect tegumentary and visceral leishmaniasis in dogs and humans

The laboratorial diagnosis of leishmaniasis is based on parasitological methods, which are invasive, present high cost, require laboratorial infrastructure and/or trained professionals; as well as by immunological methods, which usually present variable sensitivity and/or specificity, such as when they are applied to identify asymptomatic cases and/or mammalian hosts presenting low levels of antileishmanial antibodies. As consequence, new studies aiming to identify more refined antigens to diagnose visceral (VL) and tegumentary (TL) leishmaniasis are urgently necessary. In the present work, the Leishmania eukaryotic elongation factor-1 beta (EF1b) protein, which was identified in L. infantum protein extracts by antibodies in VL patients' sera, was cloned and its recombinant version (rEF1b) was expressed, purified and tested as a diagnostic marker for VL and TL. The post-therapeutic serological follow-up was also evaluated in treated and untreated VL and TL patients, when anti-rEF1b antibody levels were measured before and after treatment. Results showed that rEF1b was highly sensitive and specific to diagnose symptomatic and asymptomatic canine VL, as well as human TL and VL. In addition, low cross-reactivity was observed when sera from healthy subjects or leishmaniasis-related diseases patients were tested. The serological follow-up showed also that rEF1b-specific antibodies declined significantly after treatment, suggesting that this protein could be also evaluated as a prognostic marker for human leishmaniasis.

Leishmania infantum-derived lipophosphoglycan as an antigen in the accurate serodiagnosis of canine leishmaniasis

Lipophosphoglycan (LPG) is the major surface glycoconjugate of Leishmania protozoan and has an important biological role in host-parasite interactions both in the midgut epithelium of the sand fly vector and in the vertebrate macrophages. Canine leishmaniasis (CanL) is a chronic infectious disease predominantly caused by Leishmania infantum. An early and accurate immunodiagnosis of the disease is crucial for veterinary clinical practice and for disease control. In this work, we evaluated L. infantum LPG as an antigen in an indirect enzyme-linked immunosorbent assay (ELISA) for CanL immunodiagnosis (LPG-ELISA) by testing serum samples from 97 naturally infected dogs with diverse clinical presentations ranging from subclinical infection to severe disease, as evaluated by veterinarian infectologists. Serum samples from healthy dogs from non-endemic areas (n = 68) and from dogs with other infectious diseases (n = 64) were used as controls for assay validation. The performance of the LPG-ELISA was compared with that of an ELISA using the soluble fraction of L. infantum total lysate antigen (TLA). LPG-ELISA presented a superior performance in comparison to TLA-ELISA, with 91.5% sensitivity, 98.5% specificity and 99.7% accuracy. A distinguishing feature of the LPG-ELISA compared to the TLA-ELISA was its higher ability to identify subclinical infection in clinically healthy dogs, in addition to the absence of cross-reactivity with other canine infectious diseases. Finally, LPG-ELISA was compared to TR DPP visceral canine leishmaniasis test, the immunochromatographic test recommended by the Brazilian Ministry of Agriculture. LPG-ELISA exhibited higher values of specificity (98.5% versus 93.1%) and sensitivity (91.5% versus 90.6%) compared to TR DPP. In conclusion, L. infantum-derived LPG was recognized by antibodies elicited during CanL in different infection stages and was shown to be a suitable antigen for specific clinical settings of veterinary diagnosis and for public health usage.

Canine leishmaniasis (CanL) caused by Leishmania infantum is a zoonotic disease with high importance for the public health of several countries. L. infantum-infected dogs can be a domestic reservoir of the protozoan parasite for sand flies, which transmit it from dogs to humans during their blood meals. It is important to diagnose and treat infected dogs as early as possible, so the dissemination of CanL and the transmission to humans can be controlled. The currently commercially available assays present problems, such as cross-reaction with other canine diseases and lack of sensitivity in the detection of dogs that do not present clinical signs of disease. In this work, we tested lipophosphoglycan (LPG), a molecule abundantly found in the protozoan´s surface, as an antigen in an immunodiagnostic platform. We were able to see that the assay using LPG is highly sensitive and specific, showed no cross-reaction with other canine infectious diseases and successfully identified infected dogs with no signs of disease.

Multiplex flow cytometry serology to diagnosis of canine visceral leishmaniasis

An accurate diagnosis of visceral leishmaniasis is an essential tool for control of the disease. While serologic methods are very useful, these conventional methodologies still present limitations in terms of sensitivity and specificity. The use of flow cytometry is a worldwide trend in the development of high-performance diagnostic methods. Herein, we describe a new flow cytometry serology test, characterized by the employment of the Cytometric Bead Array microspheres A4 and E4 coated with the recombinant antigens rLci1A and rLci2B respectively, to improve the serodiagnosis of canine visceral leishmaniasis. The tests were conducted in a wide variety of sera groups (n = 140), where the diagnostics development would be optimized accounting not just the ability to identify infected dogs with different clinical status, but also to exclude cross-reaction and differentiate vaccinated dogs from dogs infected. Serological testing of the antigenic system A4-rLci1A showed a sensitivity of 90.0% and specificity of 75%, while the E4-rLci2B testing demonstrated a sensitivity of 95.0% and specificity of 82.5%. The use of a multiplex assay of A4-rLci1A and E4-rLci2B, resulted in a diagnostic improvement, with a sensitivity of 95.0% and specificity of 91.2%. Our results show that this novel flow cytometry serology test is a viable tool for sensitive and specific serodiagnosis. Notably, the combination of distinct antigenic systems allows us to test for antibodies to multiple recombinant antigens from a single serum sample. This benefit emphasizes the importance of this methodology as an alternative in the serological diagnosis.

Failure of the dog culling strategy in controlling human visceral leishmaniasis in Brazil: A screening coverage issue?

In the present study, we assessed the annual screening coverage (i.e., the percentage of dogs that are screened for anti-Leishmania antibodies annually) in the municipality of Sobral, Ceará state, Brazil. Data on the number of dogs screened during 2008−2017 (except 2010) were obtained from the Centre for Zoonoses Control of Sobral. The annual screening coverage during 2012−2017 was calculated. Data on human visceral leishmaniasis (VL) cases during 2008−2017 were compiled from the National Disease Notification System. Correlation analyses were performed to assess the correlation between canine and human data. During 2008−2017, 73,964 dogs (range, 0 to 13,980 dogs/year) were serologically screened and 2,833 (3.8%) were positive. The annual screening coverage during 2012−2017 ranged from 11.1% to 45.7%. There were no significant correlations between the number of dogs culled and the number of human VL cases, canine positivity and human VL incidence, number of dogs culled and human VL incidence, or between canine positivity and number of human VL cases. An inconsistent and relatively low annual screening coverage was found in the study area, with no dog being screened in 2010 due to the lack of serological tests. Our results highlight that many dogs potentially infected with Leishmania infantum have been virtually overlooked by public health workers in the study area, perhaps with a negative, yet underestimated, impact on the control of canine and human VL. Hence, the failure of the dog culling strategy in controlling human VL in Brazil may be due to the low screening coverage and low percentage of culled dogs, rather than the absence of associations between canine and human infections.

The euthanasia of Leishmania-seropositive dogs has been recommended for controlling human visceral leishmaniasis (VL) in some countries where this zoonosis is endemic. We assessed the annual screening coverage (i.e., the percentage of dogs living in a given area that are screened for anti-Leishmania antibodies annually) in the municipality of Sobral, Ceará state, one of the main foci of human VL in Brazil. From 2008 to 2017, nearly 74,000 dogs were screened and 3.8% of them were positive for anti-Leishmania antibodies. No statistically significant correlation was found between the number of dogs culled annually and the incidence of human VL. The annual screening coverage ranged from 11.1% to 45.7%. Our results highlight an inconsistent and relatively low annual screening coverage, indicating that dogs potentially infected with L. infantum have been virtually overlooked by public health workers in the study area.

Spatiotemporal analysis and environmental risk factors of visceral leishmaniasis in an urban setting in São Paulo State, Brazil

Background

In Latin America, Brazil harbors the most cases of human visceral leishmaniasis (HVL). Since the early 1980s, the disease has spread to the urban centers of the north, and now the south and west of Brazil; it reached São Paulo state in the southeast in 1996, and Presidente Prudente in the western region in 2010. Our aim was to describe the spatiotemporal analysis and environmental risk factors associated with the dispersion of VL in Presidente Prudente, an urban setting with recent transmission.

Methods

An entomological survey was carried out from 2009 to 2015. A canine visceral leishmaniasis (CVL) serosurvey was performed from 2010 to 2015 using enzyme-linked immunosorbent assays (ELISA), a dual-path platform CVL rapid test, and indirect fluorescent antibodies (IFAT). Data from HVL cases were obtained from the Municipal Surveillance Epidemiology Center from 2013 to 2017. Data on water drainage and forest fragments were obtained from public platforms and irregular solid-waste deposits were determined by monthly inspections of the urban area. Kernel density maps of the distribution of CVL were constructed.

Results

From 2009 to 2015, Lutzomyia longipalpis sand flies were found in all seven areas of Presidente Prudente. From 2010 to 2015, 40,309 dogs were serologically screened and 638 showed positive results, i.e. a prevalence rate of 1.6%. From 2013 to 2017, six human cases were diagnosed with a mortality rate of 33.3%. In 2015, 56 points of irregular solid-waste deposits were identified, predominantly in the neighborhoods. Three different hotspots of CVL showed an increased distribution of vectors, seropositive dogs, irregular solid-waste deposits, forest fragments and water drainage.

Conclusions

The use of tools that analyze the spatial distribution of vectors, canine and human VL as environmental risk factors were essential to identifying the areas most vulnerable to the spread or maintenance of VL. The results may help public health authorities in planning prevention and control measures to avoid expansion and future outbreaks.

Current status and management of canine leishmaniasis in Latin America

Latin America encompasses diverse geographical, cultural and socio-economic conditions, which are reflected in the challenges for infectious disease control in the region. One of the most significant regional infectious diseases for humans and domestic dogs is leishmaniasis, occurring as visceral leishmaniasis (VL) caused by Leishmania infantum (syn. L. chagasi) transmitted by sand flies (Lutzomyia longipalpis) and with a canine reservoir, and the more common cutaneous leishmaniasis (CL) involving multiple Leishmania spp. (particularly L. braziliensis), sand fly vectors and reservoir hosts. VL is spreading within Latin America for reasons related to mass migration of human and canine populations, with incursion into novel environments (e.g. related to deforestation) coupled with a background of poverty and poor public health infrastructure. The challenges for control of VL also include: (1) the accurate identification of infected dogs (particularly subclinically infected dogs) with the current reliance on serological rather than molecular diagnostic methods, (2) controversy surrounding the ethics and efficacy of culling of seropositive dogs, (3) the limited efficacy of currently available canine vaccines and their potential to interfere with interpretation of serological testing, (4) the expense associated with distribution of insecticidal dog collars, which may prove to be the most valuable control method, and (5) the cost and therefore accessibility of licensed medical treatment for canine leishmaniasis by the general population. Resolution of these isssues will necessitate a 'One Health' approach to co-ordination of resources between human and veterinary healthcare.

PREVALÊNCIA DA LEISHMANIOSE VISCERAL CANINA E COINFECÇÕES EM REGIÃO PERIURBANA NO DISTRITO FEDERAL – BRASIL

Resumo Objetivou-se verificar a prevalência da leishmaniose visceral canina (LVC) em área periurbana com foco de transmissão no Distrito Federal (DF) e também avaliar a prevalência de coinfecções como dirofilariose, anaplasmose, erliquiose e doença de Lyme em cães sororreagentes para LVC. Inicialmente, amostras de soros dos cães da área de estudo foram testadas à reação imunocromatográfica que contém dois antígenos recombinantes ̶ rK39 e rK26 − (DPP) para Leishmania sp. O soro dos animais reagentes ao teste de DPP foi confirmado para LVC com ELISA. As amostras reagentes a ambos os testes foram analisadas para possíveis coinfecções através do teste de SNAP (IDEXX 4Dx Plus). Foram avaliados 240 cães, dos quais 132 (55%) obtiveram resultados reagentes para DPP e para ELISA concomitantemente, sendo diagnosticados com LVC. Destes, 26 (20%) foram reagentes para Ehrlichia canis ou E. ewangii, 9 (7%) apresentaram positividade para Anaplasma phagocytophilum ou A. platys e, nessas amostras que se apresentaram reagentes, observou-se a ocorrência de coinfecção de anaplasmose, erliquiose e leishmaniose em 3 (2,3%) animais. Verificou-se alta prevalência da LVC na região periurbana do DF, destacando-se a necessidade de diagnóstico mais preciso quanto a coinfecções que possivelmente podem influenciar no prognóstico e manifestação do quadro clínico desses pacientes.

Culling Dogs for Zoonotic Visceral Leishmaniasis Control: The Wind of Change

Visceral leishmaniasis, caused by Leishmania infantum, is a zoonosis, and culling seropositive dogs has been recommended to control the disease in some endemic countries. However, no scientific evidence supports the effectiveness of this strategy to reduce the incidence of visceral leishmaniasis. Economic and ethical issues concerning dog culling are discussed.

Effectiveness of deltamethrin-impregnated dog collars on the incidence of canine infection by Leishmania infantum: A large scale intervention study in an endemic area in Brazil

To reduce morbidity and mortality caused by visceral leishmaniasis (VL), the Brazilian Visceral Leishmaniasis Control and Surveillance Program promotes the diagnosis and treatment of cases, vector control, euthanasia of seropositive dogs, and health education. Nevertheless, the effectiveness of these measures is questionable as they lead to little reduction in the transmission of the disease. Thus, the effectiveness of strategies such as insecticide-impregnated collars, spot-on insecticides, and immunization of dogs should be assessed. Herein, we evaluated the effectiveness of deltamethrin-impregnated collars on reducing the incidence of Leishmania infantum infection in dogs living in an endemic area of VL. An intervention study was conducted and a total 5,850 dogs were analyzed in baseline. Of these 3,742 seronegative dogs were divided into two groups: collared and uncollared (control). Dogs were followed for 12 months and three interventions were performed. The Cox regression model was used to evaluate the effectiveness of the collar. All analyzes were performed by Intention-to-treat and per-protocol. By intention-to-treat, the incidence rates of L. infantum infection were 7.5 and 7.9 in the collar group, and 6.5 and 13.2 per 1,000 dogs-months in the control group after 6 and 12 months, respectively. In the per-protocol analysis, the incidence rates in the control group were similar to those observed in the intention-to-treat analysis. In the collar group, the incidence rate was 5.1/1,000 dogs-months after 6 and 12 months. The effectiveness by intention-to-treat after adjustment by the multivariate Cox model was 48%. In the analysis per-protocol, the effectiveness increased to 63%. Although collar use was effective when it was evaluated by intention-to-treat, higher effectiveness was found in the per-protocol analysis after one year of follow-up. The data emphasize the importance of the uninterrupted use of deltamethrin-impregnated collars to increase protection against canine VL.

Effectiveness of the Brazilian Visceral Leishmaniasis Surveillance and Control Programme in reducing the prevalence and incidence of Leishmania infantum infection

Background

Control strategies adopted by the Brazilian Visceral Leishmaniasis Surveillance and Control Programme (VLSCP) include identifying and culling seropositive infected dogs, early diagnosis and treatment of human cases, chemical control of the vector and population awareness. This study evaluated the effectiveness of the VLSCP on the prevalence and incidence rates of Leishmania infantum in children residing in areas under different VLSCP intervention times.

Methods

A quasi-experimental epidemiological study with a panel (two cross-sectional) and a concurrent cohort was performed in three areas of Belo Horizonte, southeast Brazil. The first cross-sectional study (I) was carried out with 1875 children, 478 of which were enrolled in the cohort study. In the second cross-sectional study (II), 413 additional children were included, totalizing 891 children. Laboratory diagnosis was performed by ELISA-rK39. Analyses included multilevel logistic and Poisson regression models.

Results

The incidence rates of L. infantum infection were: 14.4% in the area where VLSCP intervention was initiated in 2006 (AI2006); 21.1% in the area where intervention was initiated in 2008 (AI2008); and 11.6% in the area where intervention was initiated in 2010 (AI2010 - control area). A follow-up period of 24 months showed that the persons-time incidence rates in AI2006, AI2008, and AI2010 were: 6.2/100, 10/100, and 5.6/100 persons/24 months, respectively. The final prevalence rates of infection (cross-sectional II - in 2012), compared to the initial rates (cross-sectional I - in 2010), increased 83.7% in AI2006, 74.1% in AI2008, and decreased 5% in AI2010. Analysis of the effectiveness revealed that children residing in AI2008 are more likely to be infected (OR = 1.84; 95% CI: 1.06-3.23) and present a higher risk of infection (IRR = 1.76; 95% CI: 1.05-2.95) compared to those in AI2010. No statistically significant differences were observed in asymptomatic infection (OR and IRR) in AI2006 compared to AI2010.

Conclusions

The VLSCP was not effective at controlling L. infantum infection in areas where interventions had respectively been carried out for six and four years. However, it is unclear what the consequences in terms of human infection and diseases would be in the absence of the VLSCP. Efforts to improve the effectiveness of control measures remain a necessary priority.

Electronic supplementary material

The online version of this article (10.1186/s13071-018-3166-0) contains supplementary material, which is available to authorized users.

Relação humano-animal e leishmaniose: repercussões no cotidiano de indivíduos inseridos em região endêmica

Resumo No contexto das zoonoses, a premissa de que o cão é considerado pelos órgãos de saúde pública como um dos componentes da complexa cadeia de transmissão das leishmanioses (sendo recomendada sua eutanásia e, a partir de 2016, o tratamento com medicação específica se os cães forem diagnosticados com essa enfermidade), está permeada de conflitos, especialmente devido ao espaço que tais animais gradativamente ocupam na vida dos seres humanos, sendo até considerados como substitutos de filhos e constituindo o que vem sendo denominado de “família multiespécie”. Neste artigo analisamos a relação humano-animal no bairro de maior soroprevalência canina de leishmaniose em município endêmico, bem como as repercussões sociais percebidas pelos humanos envolvidos no processo. Por meio de entrevistas, identificamos os diversos benefícios decorrentes da convivência humano-animal, especialmente ao proporcionarem um alento à solidão e os impasses envolvidos na entrega do animal para eutanásia pelo serviço de controle de zoonoses.

[Public policies of zoonoses in Colombia, 1975-2014. An approach from Political Science and Public Health]

OBJECTIVE

To analyze public policies regarding zoonoses in Colombia, in terms of responsiveness, decision-making, processes and results, approaching their impact in the period between 1975 and 2014.

METHODS

An analysis and assessment of public policies were carried out using a mixed design. Some zoonoses were selected based on their importance for public health, epidemiology, policy and availability of consecutive information. Secondary documentary sources and primary sources were used through an annotated survey. An interpretive, historical and structural framework was built from an economic, epidemiological and political point of view. For policy analysis, the sequential approach was used and, in a complementary manner, the institutional development approach. A trend analysis of selected zoonoses was carried out.

RESULTS

The interpretive framework addressed the macro context and the key processes in two periods: 1975-1990 and 1990-2014. The analysis of public policies in zoonoses was conducted according to their decision level and the vertical and horizontal relationships between them. A trend analysis of zoonoses in the long term, as well as an assessment of the impact of the policies, was obtained.

CONCLUSIONS

Policy diversification and instrumental depth suggest that they have approached the understanding and management capacity of the complex problems of zoonoses. However, the trend analysis suggests that the impact of public policies on zoonoses is still limited.

IgG avidity index and complete blood count as biomarkers of clinical disease in naturally infected dogs with Leishmania infantum

Canine visceral leishmaniosis (CVL), a parasitic disease caused by Leishmania infantum, may evolve to a chronic condition and lead to death. Evaluation of infected dogs is important to establish the clinical and laboratory parameters involved in the evolution of the disease. The objectives of the present study were to discriminate a canine population (n = 52) into sub-clinical and clinically affected dogs based on signs and scores, to evaluate the hematological, biochemical, histopathological and parasitological parameters of the two dog groups, and to analyze the results by multivariate regression analysis with the aim of establishing biomarkers of CVL clinical disease. The most common signs observed in the clinically affected dogs (n = 29) were hyperkeratosis, weight loss, onychogryphosis, pale mucosa and lymphadenomegaly. In the multivariate analysis, animals presenting high IgG avidity index and low red blood, lymphocyte and eosinophil counts, and low serum urea concentration had an increased probability of being classified as clinically affected (p <  0.05). All five parameters were considered to be strong biomarkers for monitoring the clinical disease, while IgG avidity percentage was strongly correlated with the number of clinical signs and could function as an indicator of the duration of infection. This is the first report on the application of IgG avidity and of multivariate regression analysis in establishing associations between the clinical signs of CVL and host biomarkers. Since avidity index (AI) percentages were strongly correlated with the number of clinical signs, it could be useful in clinical practice for auxiliary diagnosis of CVL and monitoring disease progression. A limitation of this study is the lack of information on co-infections by Anaplasma platys, Babesia canis vogeli, Ehrlichia canis and Hepatozoon canis. Therefore future studies should evaluate the influence of such co-infections on the associations studied using multivariate methods with larger samples.

Variables associated with the prevalence of anti-Leishmania spp. antibodies in dogs on the tri-border of Foz do Iguaçu, Paraná, Brazil

The aim of this study was to investigate the occurrence of anti-Leishmania spp. antibodies in dogs from localities in the city of Foz do Iguaçu, Paraná state, Brazil, on the border with Argentina and Paraguay. Blood samples dogs were collected to perform the following serologic tests: immunochromatographic DPP® rapid test, indirect immunoenzymatic assay (ELISA) and indirect immunofluorescence assay (IFA). In 2012, 285 dogs were analyzed on Argentina border, and in 2013, serum samples from 396 dogs on the border of Paraguay were collected. Using ELISA for screening and IFA for the confirmatory test, the results showed that the antibody prevalence was 1.8% (5/285) on the border of Argentina and 3.0% (12/396) on Paraguay border. When using the DPP® for screening and ELISA as a confirmatory analysis, we observed a seroreagent prevalence in dogs of 2.5% (7/285) on Argentina border and 5.1% (20/396) on Paraguay border. The non-public collection of domestic waste (p= 0.0004) was shown to be associated with leishmaniasis. This study shows the presence of leishmaniasis and suggest the emergence of canine visceral leishmaniasis in state of Paraná due to the confirmed occurrence of seroreactive dogs on Argentina and Paraguay border, which has environmental and geographical characteristics that favor the spread of the parasite.

Canine Leishmaniasis: An Overview of the Current Status and Strategies for Control

Canine leishmaniasis (CanL) is a vector-borne disease caused by Leishmania infantum and is transmitted by female phlebotomine sand flies primarily between animals and secondarily to humans. The course of infection may be different from one individual dog to another, ranging from spontaneous cure to acute evolution that leads to death, if proper management and therapy are not adopted. A parasitological cure is rarely achieved and clinical recurrences in CanL are frequent. Vaccination associated with the use of topical insecticides is undoubtedly the most effective form of prevention and control of the disease. In order to integrate the most important scientific knowledge of the literature in one objective publication, this review proposes a short overview of the main points of CanL.

Safety Analysis of Leishmania Vaccine Used in a Randomized Canine Vaccine/Immunotherapy Trial

In Leishmania infantum-endemic countries, controlling infection within dogs, the domestic reservoir, is critical to public health. There is a need for safe vaccines that prevent canine progression with disease and transmission to others. Protective vaccination against Leishmania requires mounting a strong, inflammatory, Type 1 response. Three commercially available canine vaccines on the global veterinary market use saponin or inflammatory antigen components (Letifend) as a strong pro-inflammatory adjuvant. There is very little information detailing safety of saponin as an adjuvant in field trials. Safety analyses for the use of vaccine as an immunotherapeutic in asymptomatically infected animals are completely lacking. Leishmania infantum, the causative agent of canine leishmaniasis, is enzootic within U.S. hunting hounds. We assessed the safety of LeishTec^® after use in dogs from two different clinical states: 1) without clinical signs and tested negative on polymerase chain reaction and serology or 2) without clinical signs and positive for at least one Leishmania diagnostic test. Vaccine safety was assessed after all three vaccinations to quantify the number and severity of adverse events. Vaccinated animals had an adverse event rate of 3.09%, whereas placebo animals had 0.68%. Receiving vaccine was correlated with the occurrence of mild, site-specific, reactions. Occurrence of severe adverse events was not associated with having received vaccine. Infected, asymptomatic animals did not have a higher rate of adverse events. Use of vaccination is, therefore, likely to be safe in infected, asymptomatic animals.

Políticas de zoonosis en Colombia: del Código Sanitario a la salud ambiental

Objetivo Analizar las políticas públicas de zoonosis en Colombia, en el período de 1975 a 2014, como respuestas estatales.Metodología Se utilizó el enfoque de análisis de ciclo de política o enfoque secuencial. Este análisis se llevó a cabo por medio de los siguientes aspectos: contenidos, procesos, actores y relaciones verticales y horizontales entre las políticas.Resultados Las políticas de zoonosis son muy diversas en su alcance, contenidos y formas, y hacen parte de una historia de éxitos y fracasos, que sólo han logrado transformar de manera parcial el panorama general y regional de las zoonosis.Conclusiones La implementación de las decisiones que tienen alcance operacional es relativamente lenta y dispersa en las zonas de zoonosis del país. Ha sido un logro importante el viraje desde las políticas individualizadas a la gran política de salud ambiental-PISA.

Serological tests fail to discriminate dogs with visceral leishmaniasis that transmit Leishmania infantum to the vector Lutzomyia longipalpis

INTRODUCTION

The control of reservoirs for Leishmania infantum -induced zoonotic visceral leishmaniasis requires the identification of dogs posing a population risk. Here, we assessed the performance of several assays to identify Lutzomyia longipalpis infectious dogs.

METHODS

We evaluated 99 dogs that were positive for visceral leishmaniasis based on parasite identification. Serological analyses were performed using an enzyme-linked immunosorbent assay, immunofluorescence antibody tests in 1:40 and 1:80 dilutions, rapid dual path platform tests, immunochromatographic assay with a recombinant rK39 antigen, fast agglutination screening tests, and direct agglutination tests. We also performed PCR to analyze peripheral blood and xenodiagnosis.

RESULTS

Forty-six dogs infected at least one L. longipalpis specimen. Although the serological test sensitivities were above 85% for detecting L. longipalpis infectious dogs, none showed a satisfactory performance, as both specificity (0.06 to 13%) and the area under the receiver operating characteristic curve (45 to 53%) were low. The PCR results were also weak, with a sensitivity of 30%, specificity of 72%, and an area under the receiver operating characteristic curve of 51%. The infected L. longipalpis proportion was higher among asymptomatic dogs than symptomatic dogs. Among the symptomatic dogs, those with ulceration-free skin diseases were more infectious, with an odds ratio of 9.3 (confidence interval of 1.10 - 428.5). The larger the number of insects fed, the greater the detected infectiousness.

CONCLUSIONS

Our study supports the imperative to develop novel technologies for identifying the infectious dogs that transmit L. infantum for the benefit of public health.

Efficacies of prevention and control measures applied during an outbreak in Southwest Madrid, Spain

Leishmaniasis is a vector-borne disease of worldwide distribution, currently present in 98 countries. Since late 2010, an unusual increase of human visceral and cutaneous leishmaniasis cases has been observed in the south-western Madrid region, totaling more than 600 cases until 2015. Some hosts, such as human, domestic dog and cat, rabbit (Oryctolagus cuniculus), and hare (Lepus granatensis), were found infected by the parasite of this disease in the area. Hares were described as the most important reservoir due to their higher prevalence, capacity to infect the vector, and presence of the same strains as in humans. Various measures were adopted to prevent and control the disease, and since 2013 there was a slight decline in the human sickness. We used a mathematical model to evaluate the efficacy of each measure in reducing the number of infected hosts. We identified in the present model that culling both hares and rabbits, without immediate reposition of the animals, was the best measure adopted, decreasing the proportion of all infected hosts. Particularly, culling hares was more efficacious than culling rabbits to reduce the proportion of infected individuals of all hosts. Likewise, lowering vector contact with hares highly influenced the reduction of the proportion of infected hosts. The reduction of the vector density per host in the park decreased the leishmaniasis incidence of hosts in the park and the urban areas. On the other hand, the reduction of the vector density per host of the urban area (humans, dogs and cats) decreased only their affected population, albeit at a higher proportion. The use of insecticide-impregnated collar and vaccination in dogs affected only the infected dogs' population. The parameters related to the vector contact with dog, cat or human do not present a high impact on the other hosts infected by Leishmania. In conclusion, the efficacy of each control strategy was determined, in order to direct future actions in this and in other similar outbreaks. The present mathematical model was able to reproduce the leishmaniasis dynamics in the Madrid outbreak, providing theoretical support based on successful experiences, such as the reduction of human cases in Southwest Madrid, Spain.

Magalhães-Junior J, Souza BM, Franke CR, Veras PS, Larangeira DF, Barrouin-Melo SM. Avaliação da infectividade parasitária a Lutzomyia longipalpis por xenodiagnóstico em cães tratados para leishmaniose visceral naturalmente adquirida

RESUMO: O efeito de um protocolo quimioterápico multidrogas contra a leishmaniose visceral (LV) canina, sobre a capacidade de transmissão de Leishmania infantum ao vetor, foi analisado por meio de xenodiagnóstico. Trinta e cinco cães naturalmente infectados foram avaliados antes e durante o tratamento com a combinação de metronidazol, cetoconazol e alopurinol a cada três meses por até um ano. Em cada avaliação, os cães foram individualmente submetidos ao xenodiagnóstico e quantificação da carga parasitária por PCR quantitativa. O tratamento foi eficaz em bloquear a transmissibilidade parasitária do cão para o flebotomíneo (p= 0,011) nos cães avaliados. Houve significante correlação entre recuperação clínica e infectividade: cães com melhora clínica mais evidente apresentaram menores chances de transferir L. infantum ao Lutzomyia longipalpis via xenodiagnóstico (r=0,528, p= 0,002). Esses resultados demonstram que o tratamento canino com o protocolo proposto pode representar uma alternativa ao sacrifício de cães no Brasil como medida de controle da doença, uma vez que as drogas utilizadas não são aplicadas ao tratamento da LV humana em áreas endêmicas.

Novel Areas for Prevention and Control of Canine Leishmaniosis

There have been multiple recent advances regarding tools for the control and prevention of canine leishmaniosis (CanL), including new preventative vaccines. In this review, these advances are evaluated based on control targets, including vector and parasite. Leishvet recommendations are provided for control practices based on the dog's risk of infection. New topical insecticide formulations have proven to be effective in preventing sand fly bites, and subsequently infection. Parasite control occurs through chemotherapeutic or immunologic means, which decrease or prevent transmission to other animals, including humans. Leishmaniosis control programs that include a combination of coordinated measures, either in individuals or for prevention across reservoir populations, are required.

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.

[Difficulties in implementing the guidelines of the Brazilian Visceral Leishmaniasis Control Program in large cities]

The expansion of visceral leishmaniasis (VL) transmission areas in Brazil raises questions concerning the country's control strategies. The guidelines of the Brazilian Visceral Leishmaniasis Control Program (PVCLC) focus on decreases in morbidity and case-fatality, reservoir and vector control, and health education. This article assesses difficulties in implementing the measures recommended by the PVCLC, according to the program's coordinators in large cities with canine and/or human transmission (Campinas, Bauru, Goiânia, Campo Grande, Fortaleza, and Belo Horizonte). Semi-structured interviews identified the following main problems: discontinuity of control activities, resistance to canine euthanasia by dog owners, and low coverage of chemical vector control.

CONCLUSION

the interviews revealed numerous obstacles to implementation of the measures proposed by the PVCLC and a clear need to reassess Brazil's VL policy.

Scoring clinical signs can help diagnose canine visceral leishmaniasis in a highly endemic area in Brazil

Canine visceral leishmaniasis (CVL) diagnosis is still a challenge in endemic areas with limited diagnostic resources. This study proposes a score with the potential to distinguish positive CVL cases from negative ones. We studied 265 dogs that tested positive for CVL on ELISA and parasitological tests. A score ranging between 0 and 19 was recorded on the basis of clinical signs. Dogs with CVL had an overall higher positivity of the majority of clinical signs than did dogs without CVL or with ehrlichiosis. Clinical signs such as enlarged lymph nodes (83.93%), muzzle/ear lesions (55.36%), nutritional status (51.79%), bristle condition (57.14%), pale mucosal colour (48.21%), onychogryphosis (58.93%), skin lesion (39.28%), bleeding (12.50%), muzzle depigmentation (41.07%), alopecia (39.29%), blepharitis (21.43%), and keratoconjunctivitis (42.86%) were more frequent in dogs with CVL than in dogs with ehrlichiosis or without CVL. Moreover, the clinical score increased according to the positivity of all diagnostic tests (ELISA, p < 0.001; parasite culture, p = 0.0021; and smear, p = 0.0003). Onychogryphosis (long nails) [odds ratio (OR): 3.529; 95% confidence interval (CI): 1.832-6.796; p < 0.001], muzzle depigmentation (OR: 4.651; 95% CI: 2.218-9.750; p < 0.001), and keratoconjunctivitis (OR: 5.400; 95% CI: 2.549-11.441; p < 0.001) were highly associated with CVL. Interestingly, a score cut-off value ≥ 6 had an area under the curve of 0.717 (p < 0.0001), sensitivity of 60.71%, and specificity of 73.64% for CVL diagnosis. The clinical sign-based score for CVL diagnosis suggested herein can help veterinarians reliably identify dogs with CVL in endemic areas with limited diagnostic resources.

Association between Leishmania infantum DNA in the hair of dogs and their infectiousness to Lutzomyia longipalpis

Diagnosis of infection with Leishmania infantum by DNA detection in the hair has been recently demonstrated in dogs and wild animals. Our objective was to investigate if polymerase chain reaction (PCR) in hair might be used to identify infectious dogs. Thus, we assessed the infectiousness to Lutzomyia longipalpis by xenodiagnosis in comparison with the detection of L. infantum DNA by PCR in the hair, and with serology for anti-Leishmania IgG by ELISA in 15 positive dogs for L. infantum infection. Eight healthy dogs were included as negative controls. Among the 15 infected dogs, 13 were found positive in the ELISA (87%), 12 were PCR positive in the hair (80%), and 10 were positive in xenodiagnosis (67%). Positivity in the hair was associated with positivity in spleen (p=0.0003), seropositivity for antibodies (p=0.0006) and parasite transmission to L. longipalpis (p=0.0028). Considering the benefits to animal welfare and feasibility of hair sampling method, studies in larger and more diverse populations of naturally infected dogs from endemic areas should be conducted to evaluate the sensitivity, specificity, and predictive values of PCR using hair as a possible biomarker of infectiousness in dogs.

Progress in the Mathematical Modelling of Visceral Leishmaniasis

The leishmaniases comprise a complex of diseases characterized by clinical outcomes that range from self-limiting to chronic, and disfiguring and stigmatizing to life threatening. Diagnostic methods, treatments, and vector and reservoir control options exist, but deciding the most effective interventions requires a quantitative understanding of the population level infection and disease dynamics. The effectiveness of any set of interventions has to be determined within the context of operational conditions, including economic and political commitment. Mathematical models are the best available tools for studying quantitative systems crossing disciplinary spheres (biology, medicine, economics) within environmental and societal constraints. In 2005, the World Health Assembly and government health ministers of India, Nepal, and Bangladesh signed a Memorandum of Understanding to eliminate the life threatening form of leishmaniasis, visceral leishmaniasis (VL), on the Indian subcontinent by 2015 through a combination of early case detection, improved treatments, and vector control. The elimination target is <1 case/10,000 population at the district or subdistrict level compared to the current 20/10,000 in the regions of highest transmission. Towards this goal, this chapter focuses on mathematical models of VL, and the biology driving those models, to enable realistic predictions of the best combination of interventions. Several key issues will be discussed which have affected previous modelling of VL and the direction future modelling may take. Current understanding of the natural history of disease, immunity (and loss of immunity), and stages of infection and their durations are considered particularly for humans, and also for dogs. Asymptomatic and clinical infection are discussed in the context of their relative roles in Leishmania transmission, as well as key components of the parasite-sandfly-vector interaction and intervention strategies including diagnosis, treatment and vector control. Gaps in current biological knowledge and potential avenues to improve model structures and mathematical predictions are identified. Underpinning the marriage between biology and mathematical modelling, the content of this chapter represents the first step towards developing the next generation of models for VL.

Application of rapid in vitro co-culture system of macrophages and T-cell subsets to assess the immunogenicity of dogs vaccinated with live attenuated Leishmania donovani centrin deleted parasites (LdCen-/-)

BACKGROUND

Live attenuated Leishmania donovani parasites as LdCen(-/-) were shown to confer protective immunity against Leishmania infection in mice, hamsters, and dogs. Strong immunogenicity in dogs vaccinated with LdCen(-/-) has been previously reported, including increased antibody response favoring Th1 response lymphoproliferative responses, CD4(+) and CD8(+) T-cells activation, increased levels of Th1 and reduction of Th2 cytokines, in addition to a significant reduction in parasite burden after 18 and 24 months post virulent parasite challenge.

METHODS

Aimed at validating a new method using in vitro co-culture systems with macrophages and purified CD4(+) or CD8(+) or CD4(+):CD8(+) T-cells of immunized dogs with both LdCen(-/-) and Leishmune® to assess microbicide capacity of macrophages and the immune response profile as the production of IFN-γ, TNF-α, IL-12, IL-4 and IL-10 cytokines.

RESULTS AND DISCUSSION

Our data showed co-cultures of macrophages and purified T-cells from dogs immunized with LdCen(-/-) and challenged with L. infantum were able to identify high microbicidal activity, especially in the co-culture using CD4(+) T-cells, as compared to the Leishmune® group. Similarly, co-cultures with CD8(+) T-cells or CD4(+):CD8(+) T-cells in both experimental groups were able to detect a reduction in the parasite burden in L. infantum infected macrophages. Moreover, co-cultures using CD4(+) or CD8(+) or CD4(+):CD8(+) T-cells from immunized dogs with both LdCen(-/-) and Leishmune® were able to identify higher levels of IFN-γ and IL-12 cytokines, reduced levels of IL-4 and IL-10, and a higher IFN-γ/IL-10 ratio. While the highest IFN-γ levels and IFN-γ/IL-10 ratio were the hallmarks of LdCen(-/-) group in the co-culture using CD4(+) T-cells, resulting in strong reduction of parasitism, the Leishmune® immunization presented a differential production of TNF-α in the co-culture using CD4(+):CD8(+) T-cells.

CONCLUSION

The distinct conditions of co-culture systems were validated and able to detect the induction of immune protection. The method described in this study applied a new, more accurate approach and was able to yield laboratory parameters useful to test and monitor the immunogenicity and efficacy of Leishmania vaccines in dogs.

Xenodiagnosis on dogs with visceral leishmaniasis: Canine and sand fly aspects related to the parasite transmission

One of the main limitations for the effective control of canine leishmaniasis in endemic areas is the difficulty in identifying infectious dogs. The objective of this study was to determine factors, related to dogs and to parasite detection in sand flies, which are associated with the positive xenodiagnosis of Leishmania infantum using the vector Lutzomyia longipalpis. The xenodiagnosis was performed in 50 owned dogs residing in endemic areas, which were divided into three different groups: G1-26 dogs proved to be infected and classified by severity of VL clinical signs on physical examination; G2-15 dogs proved to be infected and classified by severity of clinical signs and intensity of laboratory abnormalities; G3-nine dogs that were seropositive for anti-Leishmania IgG in ELISA tests. Parasite search in the sand flies after having fed on dogs in the xenodiagnosis was performed by both methodologies, PCR and dissection followed by microscopy. In G1, 58% (15/26) of dogs were able to transmit Leishmania to the vector, when parasite detection in sand flies were performed by PCR technique, 5 days after blood meal, whereas in G2, 53% (8/15) transmitted the parasite to the vector, however, confirmation was performed by direct observation of parasite through optical miscroscopy held 10 days after blood meal. Rate of infectiousness of dogs to sand flies was positively associated to severity of disease (p=0.042 and p=0.040), regardless the method used for clinical classification or for parasite detection in sand flies after xenodiagnosis. In G1 30% (3/10) of dogs with subclinical infection were infectious to the vector, while 80% (12/16) of dogs with clinical disease were also infectious. Even more, 17% (1/6) of dogs that had moderate disease were infectious to the sand flies, while 78% (7/9) of dogs with severe disease were infectious in G2. Still in G2, the proportion of sand flies infected (grade of infectiousness) was significantly lower (p=0.0098) when they fed on dogs with moderate disease (1%) in comparison with dogs with severe disease (38%). The dogs from G3 presented a rate of infectiousness of 11% (1/9), demonstrating that the indirect ELISA is not a good indicator of infectiousness and, therefore, should not be used as a confirmatory test for the euthanasia of dogs, as it is currently done in Brazil.

Decentralized control of human visceral leishmaniasis in endemic urban areas of Brazil: a literature review

OBJECTIVES

Human migration and concomitant HIV infections are likely to bring about major changes in the epidemiology of some parasitic infections in Brazil. Human visceral leishmaniasis (HVL) control is particularly fraught with intricacies. It is against a backdrop of decentralized health care that the complex HVL control initiatives are brought to bear. This comprehensive review aims to explore the obstacles facing decentralized HVL control in urban endemic areas in Brazil.

METHOD

A literature search was carried out in December 2015 by means of three databases: MEDLINE, Google Scholar, and Web of Science.

RESULTS

Although there have been many strides that have been made in elucidating the eco-epidemiology of Leishmania infantum, which forms the underpinnings of the national control program, transmission risk factors for HVL are still insufficiently elucidated in urban settings. Decentralized HVL epidemiological surveillance and control for animal reservoirs and vectors may compromise sustainability. In addition, it may hamper timely human HVL case management. With the burgeoning of the HIV-HVL co-infection, the potential human transmission may be underestimated.

CONCLUSION

HVL is a disease with focal transmission at a critical juncture, which warrants that the bottlenecks facing the control program within contexts of decentralized healthcare systems be taken into account. In addition, HIV-driven HVL epidemics may substantially increase the transmission potential of the human reservoir. Calculating the basic reproductive number to fine-tune interventions will have to take into consideration the specific socio-economic development context.

GEOGRAPHICAL EXPANSION OF CANINE VISCERAL LEISHMANIASIS IN RIO DE JANEIRO STATE, BRAZIL

Visceral Leishmaniasis (VL) is a vector-borne disease that affects humans, and domestic and wild animals. It is caused by the protozoan Leishmania (Leishmania) infantum (syn = Leishmania chagasi). The domestic dog (Canis familiaris) is considered the main reservoir of the etiologic agent of VL in domestic and peridomestic environments. In the past three years, although control actions involving domestic dogs are routinely performed in endemic areas of the Rio de Janeiro State, new cases of canine visceral leishmaniasis (CVL) have been reported in several municipalities. The objective of this short communication was to describe the geographical expansion of CVL in the Rio de Janeiro State, Brazil, through its reports in the scientific literature and studies performed by our group. From 2010 to 2013, autochthonous and allochthonous cases of CVL were reported in the municipalities of Mangaratiba, Marica, Niteroi, Barra Mansa, Cachoeiras de Macacu, Volta Redonda, Resende and Rio de Janeiro. These reports demonstrate that CVL is in intense geographical expansion around the state; therefore, a joint effort by public agencies, veterinarians and researchers is needed in order to minimize and/or even prevent the dispersion of this disease.

Field randomized trial to evaluate the efficacy of the Leish-Tec® vaccine against canine visceral leishmaniasis in an endemic area of Brazil

BACKGROUND

A canine vaccine remains a promising approach for effective control of visceral leishmaniasis (VL), given its complex epidemiology in areas where zoonotic VL is prevalent. Leish-Tec(®) is a recombinant vaccine, based on the Leishmania A2 antigen, against canine VL (CVL). It is, since 2014, the single commercial vaccine licensed in Brazil. Here, Leish-Tec(®) efficacy was estimated through a randomized field trial (RFT), in a highly VL endemic area.

METHODS

The RFT was conducted from 2008 to 2010 in an endemic area of southeastern Brazil, presenting a CVL seroprevalence of 41.9%. Eight hundred forty-seven seronegative dogs were randomly selected to receive Leish-Tec(®) (n=429) or placebo (n=418). Animals were followed up by clinical, serological, and parasitological exams for 18 months. The CVL incidence in both groups was compared through proportion analysis.

RESULTS

A significant reduction in the number of cases of CVL was observed in the vaccine group, as compared with the placebo group, whether efficacy was estimated according to parasitological results (71.4%; 95% CI: 34.9-87.3%; p=0.001; risk ratio=0.287), by adding results of xenodiagnosis and parasitological exams (58.1%; 95% CI: 26.0-76.3%; p=0.002; risk ratio=0.419). Among the animals that converted to a positive anti-A2 serology, efficacy reached 80.8% (95% CI: 37.6-94.1%, p=0.001; risk ratio=0.192). Xenodiagnosis has detected a reduction of 46.6% (p=0.05) in transmission to sand flies from vaccinated animals presenting anti-A2 positive serology.

CONCLUSION

The Leish-Tec(®) vaccine proved significantly effective for prophylaxis of CVL, after natural challenge assured by transmission of Leishmania parasites, in a highly endemic area. Noteworthy, this report has unveiled the complexity of performing a RFT for anti-CVL vaccines in Brazil, which may be helpful for designing of future studies.

O uso de um instrumento de política de saúde pública controverso: a eutanásia de cães contaminados por leishmaniose no Brasil

Resumo A leishmaniose visceral é uma zoonose transmitida por vetor, de importância mundial, que envolve os cães como reservatórios. A "eliminação dos reserva tórios" está prevista expressamente como medida de controle no Manual de Vigilância e Controle da Leishmaniose Visceral elaborado pela Secretaria de Vigilância em Saúde, órgão do Ministério da Saúde. Contudo, a eliminação de cães soropositivos no Brasil, usada para controlar a leishmaniose vis ceral, tem sido pouco efetiva. Este trabalho levanta questionamentos sobre esse instrumento de política nacional de saúde pública com base em evidências científicas atuais e análises do ordenamento jurí dico brasileiro, realizadas a partir do princípio da precaução e do reconhecimento dos animais como seres sencientes. Conclui-se pela imediata suspen são e revisão da prática de extermínio animal em um Estado Constitucional de Direito, e a adoção de métodos preventivos e mais eficazes que garantam a saúde pública sem proporcionar elevados custos emocionais aos proprietários de cães e financeiros aos cofres públicos.