Visceral Leishmaniasis Endemic Areas Research Articles

In vitro Infectivity of Strains Isolated From Dogs Naturally Infected With Leishmania infantum Present a Distinct Pathogenic Profile in Hamsters.

Visceral leishmaniasis (VL) is a severe disease caused by Leishmania infantum. Dogs are the parasite's main reservoir, favoring its transmission in the urban environment. The analysis of L. infantum from infected dogs contributes to the identification of more virulent parasites, thereby supporting basic and applied studies such as vaccinal and therapeutic strategies. We proposed the in vitro and in vivo characterization of L. infantum strains from naturally infected dogs from a VL endemic area based on an infectivity and pathogenicity analysis. DH82 canine macrophages were infected in vitro with different strains for infectivity analysis, showing distinct infectivity profiles. The strains that showed greater and lesser infectivity using in vitro analyses (616 and 614, respectively) were used to infect hamsters for pathogenicity analysis. The group infected with strain 616 showed 100% survival while the group infected with strain 614 showed 50% after seven months of follow up. Furthermore, the 614 strain induced more noticeable clinicopathological changes and biochemical abnormalities in liver function, along with high inflammation and parasite load in the liver and spleen. We confirmed high variability of infectivity and pathogenicity in L. infantum strains from infected dogs. The results support the belief that screening for L. infantum infectivity using in vitro experiments is inadequate when it comes to selecting the most pathogenic strain.

Conversion of asymptomatic infection to symptomatic visceral leishmaniasis: Astudy of possible immunological markers.

IntroductionPresence of asymptomatic individuals in endemic areas is common. The possible biomarkers in asymptomatic individuals once they get exposed to infection as well as following conversion to symptomatic disease are yet to be identified.We identified asymptomatic Visceral leishmaniasis (VL) infection amongst rK39+sorted direct agglutination test positive (DAT+) endemic healthy population and confirmed it by quantitative PCR(qPCR).The immunological determinants such as Adenosine deaminase (ADA), Interferon gamma (IFN-γ), Tumour Necrosis Factor alpha (TNF-α) and Interleukin 10 (IL-10)were examined to predict probable biomarkers for conversion to symptomatic VL.MethodsSample size was 5794 healthy individuals from VL endemic region. Antibody tests(DAT &rK39) were performed and later a qPCR assay was employed using kDNA specific primers and probes. Immunological biomarkers examined were ADA level by ADA–MTP kit and quantitative cytokines(IFN-γ, IL-10 and TNF-α) by ELISA.Results120 asymptomatic individuals of 308 rK39 sero-positives were DAT positive comprising of 56 with previous history and 64 with no history of VL. RT-PCR confirmed asymptomatic VL in 42 sero-positives. These were followed up through repeated qPCR and evaluation of immunological determinants. We observed10 symptomatic cases converted from a total of 42 asymptomatic individuals identified at base-line. The level of ADA, IL-10 and IFN-γ remained consistently high in asymptomatic cases and amongst these, ADA and IL-10 but not IFN-γ remained higher at the development of clinical symptoms into active VL. On the contrary, there was no significant change in the mean concentration of TNF-α at both stages of the disease.DiscussionWe surmise from our data that considerable proportion of asymptomatic cases can be a reservoir and may play a crucial role in transmission of visceral leishmaniasis in endemic areas.The data also suggests that ADA and IL-10 can serve as a potential biomarker during the conversion of asymptomatic into symptomatic VL.

Immunity to vector saliva is compromised by short sand fly seasons in endemic regions with temperate climates

Individuals exposed to sand fly bites develop humoral and cellular immune responses to sand fly salivary proteins. Moreover, cellular immunity to saliva or distinct salivary proteins protects against leishmaniasis in various animal models. In Tbilisi, Georgia, an endemic area for visceral leishmaniasis (VL), sand flies are abundant for a short period of ≤3 months. Here, we demonstrate that humans and dogs residing in Tbilisi have little immunological memory to saliva of P. kandelakii, the principal vector of VL. Only 30% of humans and 50% of dogs displayed a weak antibody response to saliva after the end of the sand fly season. Likewise, their peripheral blood mononuclear cells mounted a negligible cellular immune response after stimulation with saliva. RNA seq analysis of wild-caught P. kandelakii salivary glands established the presence of a typical salivary repertoire that included proteins commonly found in other sand fly species such as the yellow, SP15 and apyrase protein families. This indicates that the absence of immunity to P. kandelakii saliva in humans and dogs from Tbilisi is probably caused by insufficient exposure to sand fly bites. This absence of immunity to vector saliva will influence the dynamics of VL transmission in Tbilisi and other endemic areas with brief sand fly seasons.

Leishmaniasis and Tuberculosis Concurrent Infection in Humans and Animals in Kala-azar Endemic Areas of Bangladesh

Introduction: Co-infection of parasitic disease and pulmonary tuberculosis are increasing public health problem especially in developing countries like Bangladesh. More than 81% of cases and deaths from TB are in developing countries and is aggravated by concurrency with parasitic diseases, where in Bangladesh suffer a substantial no of Kala-azar cases in each year. Cattle are found to have bovine tuberculosis but at the same areas of Kala-azar endemicity, whether this animal found to be positive.
 Objectives: To findout the concurrent infection in humans and animals in Kala-azar endemic areas of Bangladesh.
 Materials and Methods: This study was conducted at Surya Kanto Hospital, Mymensingh and four Kala-azar endemic Upazilla of Mymensingh, Tangail and Pabna District. A total of 300 highly suspected tuberculosis patients reported from Kala-azar endemic areas and 170 cattle’s blood sample, 110 cattle spleen samples were included in this study. Cattle blood and spleen samples were investigated for both TB and Kalaazar and all the TB cases were investigated for Kala-azar. Buffy coat from venous blood was taken for ELISA and PCR. Spleen samples were sonicated and then were examined by PCR. All patients’ blood was tested with ICT (rK39) for Visceral Leishmaniasis. ICT positive patient’s splenic aspiration was examined by smear microscopy with 10x 100 magnifications. After that, all these samples were tested by ELISA and PCR.
 Results: Out of total 300 patients 162(54%) were found positive for TB. Blood sample of 180 patients was tested with ICT rK39 and 12(7%) patients were found positive for leishmaniasis who suffered from Tuberculosis. These 12(7%) patient’s splenic smear were examined of which 11(92%) of them were found positive for leishmania. But using ELISA all 12(100%) patient smears were found positive. Out of 170 cattle blood 12(7.1%) were ICT positive indicating prevalence of bovine tuberculosis and of these 170 cattle blood 20(11.8%) were found positive for antileishmania antibody. With PCR of these 20, no one was found positive for Leishmania.
 Conclusion: Visceral leishmaniasis and tuberculosis coinfection have drawn attention clinically. This study found the presence of leishmaniasis and tuberculosis concurrently in humans in Kala-azar endemic areas, wherein bTB antibody was detected in cattle. Though concurrently leishmania antibody was found in cattle but was not proved by PCR which requires further studies.
 Journal of Armed Forces Medical College Bangladesh Vol.14 (2) 2018: 91-96

Seasonal variation of sand fly populations in Kala-azar endemic areas of the Malda district, West Bengal, India

Vector control is one of the main aspects to reach the target of eliminating visceral leishmaniasis from Indian sub-continent as set by the World Health Organisation. Data on different aspects of vector like ecology, behaviour, population dynamics and their association with environmental factors are very important for formulating an effective vector control strategy. The present work was designed to study the species abundance and impact of environmental factors on population dynamics of vector P. argentipes in a visceral leishmaniasis endemic area of Malda district, West Bengal. Adult sand flies were collected using light traps and mouth aspirators from twelve kala-azar affected villages of Habibpur block of Malda district, on a monthly basis from January to December, 2018. Morphological and molecular methods were used for species identification. Population dynamics were assessed by man hour density and per night per trap collection. Data were analysed using SPSS software to determine the impact of environmental factors on vector population P. argentipes was found to the predominant species and prevalent throughout the year. A significantly higher number of sand flies were collected from cattle sheds than human dwellings and peri-domestic vegetation. A portion of the P. argentipes population was exophilic and exophagic as evidenced by their collection from peri-domestic vegetation. The highest population density was recorded during April to September. Population dynamics were mostly influenced by average temperature along humidity and rain fall. Resting behaviour of sand flies was not restricted to the lower portion of the wall but equally distributed throughout the wall and ceiling. Programme officials should consider management of outdoor populations of the sand flies and timings of indoor residual spray for chemical control purpose.

An epidemiological study of visceral leishmaniasis in North East Ethiopia using serological and leishmanin skin tests.

BackgroundIn Ethiopia, visceral leishmaniasis (VL) is caused by Leishmania donovani. The estimated country-wide incidence of VL in Ethiopia is 3700–7400 cases/year. The balance between anthroponotic and zoonotic transmission is still unknown even though most authors believe that visceral leishmaniasis in East Africa is anthroponotic. Asymptomatic leishmania infections occur more frequently than clinically apparent visceral leishmaniasis cases. The aim of this study was to determine the prevalence of asymptomatic VL infection and assess the degree of exposure among residents in Raya Azebo Woreda villages where cases of VL were recently reported.MethodsA community based cross-sectional survey was conducted in 2013 between 1st of May and 25th of July. A total of 1099 individuals living in 314 households were included in the study. Socio-demographic and clinical data were collected from each of the participants and venous blood was also collected for the detection of antibodies to visceral leishmaniasis using Direct Agglutination Test. Leishmanin skin test was performed to detect the exposure to the parasite. Data was entered into excel and exported to SPSS version 17 for statistical analysis. Chi-square and the corresponding p-values were used to determine the statistical significance of the proportions/ratios obtained from the cross tabulated data. A p-value < 0.05 was considered statistically significant.ResultA total of 1099 study subjects comprising 401 males and 698 females were included in the study. The overall positive leishmanian skin test and sero-prevalence rates respectively were 9.08% and 0.87%. The difference in LST positivity by age group and sero-prevalence by sex were statistically significant (P <0.01 and P<0.05 respectively). Out of the 9 sero-positive individuals, 7 had no history of travel to visceral leishmaniasis endemic areas out of Raya Azebo.ConclusionIn general our results suggest occurrence of VL in the study area is, very low. Our survey also indicates that due to the low incidence of the disease, and lack of awareness, some patients remain under diagnosed.

Sandflies in an endemic area for Visceral Leishmaniasis in Northeastern Brazil.

Phlebotomines of the genus Lutzomyia are important vector for species of Leishmania, the etiological agent of leishmaniasis. The aim of this study was to assess the diversity of sandflies in an endemic area for Visceral Leishmaniasis (VL). Sampling was performed in four localities on the coast of the municipality of Goiana, state of Pernambuco, Northeastern Brazil. Specimens were collected monthly on three consecutive nights, from November 2017 to October 2018. CDC light traps were installed at a height of 1.5 m above the ground, in two ecotypes (i.e. tree and animal facility), both in peridomestic areas. A total of 5,205 sandflies were collected, among which the species Lutzomyia longipalpis (99.85%; 5,197/5,205) was the most common, followed by Lutzomyia evandroi (0.13%; 07/5,205) and Lutzomyia whitmani (0.02%; 01/5,205). Specimens of L. longipalpis were collected throughout the study period and most of them were found near to the animal facilities. The findings from this research indicate that vectors for Leishmania infantum are present in the study area throughout the year, along with occurrences of vectors relating to Cutaneous Leishmaniasis (CL). Preventive vector control measures need to be implemented in Goiana to reduce the risk of infection for the human and animal populations.

Natural infection by Leishmania infantum in the Lutzomyia longipalpis population of an endemic coastal area to visceral leishmaniasis in Brazil is not associated with bioclimatic factors.

Visceral leishmaniasis (VL) is a zoonosis caused by the protozoan Leishmania infantum and in Brazil is transmitted mainly by the bite of Lutzomuyia longipalpis sand flies. Data about the presence, distribution, natural infection rate, seasonal and monthly dynamics of the vector population are important for optimizing the measures to control VL in endemic areas. This study aimed to identify sand fly fauna in an endemic area for VL to detect the prevalence of L. infantum infection in the Lu. longipalpis population and to elucidate the influence of bioclimatic factors on the monthly fluctuations of this vector. HP light traps were monthly set in the intradomicile and peridomicile of residences located in the central and beachfront areas of Camaçari, a VL endemic area. The sand fly collection was conducted in two periods: i) period 1—between December 2011 and November 2012 and ii) period 2—August 2014 and July 2015. Sand fly species were identified and detection of L. infantum infection by qPCR was performed in pools of female Lu. longipalpis. For the first time, the parasite load of positive pools was correlated with the number of Lu. longipalpis captured per month in both periods. Correlation analyses between the monthly fluctuation of the sand fly population and bioclimatic indices of the municipality in both collection periods were also performed. In both evaluated periods, more than 98% of the collected sand flies were Lu. longipalpis, confirming the predominance of this species in the region. It was captured mostly in the beachfront area in all months evaluated (99%). For the period 1, Leishmania DNA was detected in 81% of tested pools representing a minimal infection rate of 9.6%. In the period 2, 40% of the pools were positive with a minimal infection rate of 10.2%. Infected sand flies were only detected in the beachfront area in both periods. The parasite load was low and did not vary in the evaluated months despite the number of collected sand flies. No correlation was observed for climatic factors in both areas of Camaçari. These findings emphasize the high risk of Leishmania transmission in Camaçari regardless of the season and that other factors, aside from bioclimatic elements, are influencing the sand fly population monthly fluctuation.

Comparison of KAtex, Bone Marrow Aspiration and DAT for the Diagnosis of Visceral Leishmaniasis

Background: Newly developed KAtex test can be used as a non invasive tool for diagnosis of Kala-azar.&#x0D; Objectives: The aim of the present study was to compare KAtex, Bone marrow aspiration and DAT to diagnose VL.&#x0D; Methodology: This cross-sectional study was carried out in the Department of Microbiology at Dhaka Medical College, Dhaka, Bangladesh in collaboration with the Department of Parasitology, Institute of Epidemiology, Disease Control and Research (IEDCR), Dhaka, Bangladesh for a period of one year. Clinically suspected Kala-azar (VL) cases of different age and sex attending IEDCR, Dhaka from different Kala-azar endemic areas of Bangladesh were selected for this study. Patients having fever for more than 2 weeks, with or without splenomegaly, having history of loss of body weight following onset of fever were clinically suspected as Kala-azar cases. Microscopy and culture was performed in bone marrow (BM). KAtex was performed with urine sample. Agglutination of sensitized latex indicated presence of Leishmania donovani antigen in urine and thereby visceral leishmaniasis. No agglutination indicates absence of antigen in urine. DAT was done with serums of all cases.&#x0D; Result: Among 130 clinically suspected VL cases, 70 (53.85%) cases were BM positive and 60(46.15%) cases were BM negative. All the 70 BM positive cases were positive by KAtex and DAT. Among 60 BM negative cases, 15 were positive by KAtex and 23 were positive by DAT. The sensitivity of KAtex was 100.0% and specificity was 75.0%. The sensitivity of DAT was 100.0% and specificity is 61.6%.&#x0D; Conclusion: In conclusion, KAtex test is a good diagnostic tool for the detection of VL in comparison with DAT.&#x0D; Bangladesh Journal of Infectious Diseases, June 2019;6(1):12-15

Surveillance of phlebotomine fauna and Didelphis marsupialis (Didelphimorphia: Didelphidae) infection in an area highly endemic for visceral leishmaniasis in Colombia.

The study of the interaction between the parasite, the vector and the mammalian hosts, including man, allows to understand the behavior of the leishmaniases. To determine the presence of Lutzomyia species and to detect the Leishmania infection in Didelphis marsupialis in an endemic area for visceral leishmaniasis. Phlebotomine fauna and individuals of D. marsupialis were collected with CDC and Tomahawk™ traps, respectively. The species of Lutzomyia were identified using the Young and Duncan key (1994). Ear and tail biopsies and blood samples from D. marsupialis were taken to identify the Leishmania species by amplifying a fragment of the gene associated with the 70 kD heat shock protein. Seven Lutzomyia species were identified: Lu. evansi, Lu. gomezi, Lu. panamensis, Lu. dubitans, Lu. cayennensis cayennensis, Lu. rangeliana and Lu. trinidadensis. The first three species have epidemiological importance in Colombia because of their implications in the transmission of the Leishmania parasite. Sixty-five tissue samples from 19 D. marsupialis individuals were negative for Leishmania spp. The presence of the Lutzomyia species that have been identified as vectors for Leishmania inside and around houses in the village of El Bledo, in El Carmen de Bolívar represents a risk of infection. Furthermore, the presence of Lu. panamensis is reported for first time in El Carmen de Bolívar in Colombia. Although the lack of detection of Leishmania spp. in D. marsupialis samples may suggest that D. marsupialis does not play an important role in the transmission cycle of Leishmania in this region, it is necessary to carry out further longitudinal studies to confirm this hypothesis.

Observation on growth and reproduction of various Leishmania isolates in different culture media

To compare the growth and reproduction of the promastigotes of Leishmania isolates from various endemic areas of visceral leishmaniasis in China in various culture media, so as to provide experimental evidence for selecting an appropriate medium for the culture of Leishmania. A total of 3 × 105 promastigotes of KS-2, Cy and JIASHI-5 Leishmania isolates were inoculated into 1 mL NNN medium, 1 mL M199 medium supplemented with 20% fetal bovine serum medium, 1 mL M199 medium supplemented with 20% horse serum medium, and 1 mL brain heart infusion medium containing heme, respectively. All media were placed at 22 ℃ under a sterile condition, and the number of promastigotes was counted continuously for 8 days under a microscope. The growth curve was plotted for the three Leishmania isolates. The promastigotes of KS-2, Cy and JIASHI-5 Leishmania isolates all grew and reproduced in the NNN medium, the M199 medium supplemented with 20% fetal bovine serum medium, and the M199 medium supplemented with 20% horse serum medium. The number of promastigotes of KS-2, Cy and JIASHI-5 Leishmania isolates was all significantly higher in the NNN medium than in the M199 medium supplemented with 20% fetal bovine serum medium, and the M199 medium supplemented with 20% horse serum medium at various time points of culture (all P values < 0.05), and the number of promastigotes of the KS-2 isolate was all significantly greater than that of the Cy and JIASHI-5 isolates in the NNN medium, the M199 medium supplemented with 20% fetal bovine serum medium, and the M199 medium supplemented with 20% horse serum medium at various time points of culture (all P values < 0.05). In ad dition, the promastigotes of KS-2, Cy and JIASHI-5 Leishmania isolates failed to grow and reproduce in the brain heart infusion medium. The growth and reproduction of the promastigotes of various Leishmania isolates from various endemic areas of visceral leishmaniasis in China vary in the same culture medium, and the growth and reproduction of a Leishmania isolate vary in different culture media. The NNN medium best fits for the culture of Leishmania isolates in the endemic areas of visceral leishmaniasis in China.

Disorganization of spleen compartments and dermatitis in canine visceral leishmaniasis

Canine visceral leishmaniasis is associated with splenic changes that may interfere with the surveillance of blood borne antigens. Dogs with terminal visceral leishmaniasis present with a variety of skin lesions that may reflect a failure of the immune system to cope with infection. In this study, we compare the frequency of dermatitis in dogs from an endemic area of visceral leishmaniasis and take account of the following parameters: presence/absence of laboratory markers of infection and susceptibility to visceral leishmaniasis, and presence/absence of splenic structural changes associated with severe forms of the disease. Dermatitis was present in 48 of 64 (75%) of the animals. Dermatitis was more frequent in animals with positive splenic culture and negative leishmanin skin test (14/15, 93%) than in non-infected controls (P = 0.01). Diffuse dermatitis was present only in animals with evidence of Leishmania infection. Diffuse dermatitis was also more frequent in animals with positive (9/27, 33%) as opposed to negative (3/34, 9%) serology against Leishmania (P = 0.01). Presence of dermatitis correlated with both perisplenitis (P = 0.03) and with an increase in plasma cell density in the splenic tissue (P = 0.02). Diffuse dermatitis also correlated with splenic lymphoid tissue disorganization (P = 0.03) and germinal center atrophy (P < 0.01). The relationship between chronic dermatitis and spleen disorganization suggests an impairment of immune response to deal with skin aggressions in dogs with severe forms of visceral leishmaniasis. It also suggest that skin biopsy can be used in a model to define severity of canine visceral leishmaniasis.

Nucleoside Hydrolase NH 36: A Vital Enzyme for the Leishmania Genus in the Development of T-Cell Epitope Cross-Protective Vaccines.

NH36 is a vital enzyme of the DNA metabolism and a specific target for anti-Leishmania chemotherapy. We developed second-generation vaccines composed of the FML complex or its main native antigen, the NH36 nucleoside hydrolase of Leishmania (L.) donovani and saponin, and a DNA vaccine containing the NH36 gene. All these vaccines were effective in prophylaxis and treatment of mice and dog visceral leishmaniasis (VL). The FML-saponin vaccine became the first licensed veterinary vaccine against leishmaniasis (Leishmune®) which reduced the incidence of human and canine VL in endemic areas. The NH36, DNA or recombinant protein vaccines induced a Th1 CD4+IFN-γ+ mediated protection in mice. Efficacy against VL was mediated by a CD4+TNF-α T lymphocyte response against the NH36-F3 domain, while against tegumentary leishmaniasis (TL) a CD8+ T lymphocyte response to F1 was also required. These domains were 36–41 % more protective than NH36, and a recombinant F1F3 chimera was 21% stronger than the domains, promoting a 99.8% reduction of the parasite load. We also identified the most immunogenic NH36 domains and epitopes for PBMC of active human VL, cured or asymptomatic and DTH+ patients. Currently, the NH36 subunit recombinant vaccine is turning into a multi-epitope T cell synthetic vaccine against VL and TL.

Modulation of the immune response and infection pattern to Leishmania donovani in visceral leishmaniasis due to arsenic exposure: An in vitro study.

The arsenic contamination of ground water in visceral leishmaniasis (VL) endemic areas in Bihar, India leads to human exposure through drinking water. Possibly, the consumed arsenic (As) accumulates in the tissues of VL patients, who subsequently internalize intracellular amastigotes to confer resistance against chemotherapy to the parasite, leading to modulation in the host’s immune response. This hypothesis appears to be consistent with the in vitro findings that in arsenic-exposed parasites, the mitochondrial membrane potential became depolarized, whereas the reduced thiol and lactate production was overexpressed with enhanced glucose consumption; therefore, the reduced thiol possibly supports an immunosuppressive state in the host cells. This observation was well supported by the down-regulated expression of pro-inflammatory cytokines (IL-2, IL-12, IFN-γ, and TNF-α) with a suppressed anti-leishmanial function of macrophage (NO, ROS). In contrast, the pathophysiological mechanism of VL has received ample support by the promotion of Th2 cytokines (IL-4 and IL-10) in the presence of arsenic-exposed Leishmania parasites (LdAS). Dysfunction of mitochondria and the overexpression of lactate production raise the possibility of the Warburg effect being operative through the up-regulation of glucose consumption by parasites to enhance the energy production, possibly augmenting virulence. Therefore, we surmise from our data that arsenic exposure to Leishmania donovani modulates the immune response and infection pattern by impairing parasite function, which may affect the anti-leishmanial effect in VL.

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.

Visceral leishmaniasis: Spatiotemporal heterogeneity and drivers underlying the hotspots in Muzaffarpur, Bihar, India.

BackgroundDespite the overall decrease in visceral leishmaniasis (VL) incidence on the Indian subcontinent, there remain spatiotemporal clusters or ‘hotspots’ of new cases. The characteristics of these hotspots, underlying transmission dynamics, and their importance for shaping control strategies are not yet fully understood and are investigated in this study for a VL endemic area of ~100,000 inhabitants in Bihar, India between 2007–2015.Methodology/Principal findingsVL incidence (cases/10,000/year) dropped from 12.3 in 2007 to 0.9 in 2015, which is just below the World Health Organizations’ threshold for elimination as a public health problem. Clustering of VL was assessed between subvillages (hamlets), using multiple geospatial and (spatio)temporal autocorrelation and hotspot analyses. One to three hotspots were identified each year, often persisting for 1–5 successive years with a modal radius of ~500m. The relative risk of having VL was 5–86 times higher for inhabitants of hotspots, compared to those living outside hotspots. Hotspots harbour significantly more households from the two lowest asset quintiles (as proxy for socio-economic status). Overall, children and young adelescents (5–14 years) have the highest risk for VL, but within hotspots and at the start of outbreaks, older age groups (35+ years) show a comparable high risk.Conclusions/SignificanceThis study demonstrates significant spatiotemporal heterogeneity in VL incidence at subdistrict level. The association between poverty and hotspots confirms that VL is a disease of ‘the poorest of the poor’ and age patterns suggest a potential role of waning immunity as underlying driver of hotspots. The recommended insecticide spraying radius of 500m around detected VL cases corresponds to the modal hotspot radius found in this study. Additional data on immunity and asymptomatic infection, and the development of spatiotemporally explicit transmission models that simulate hotspot dynamics and predict the impact of interventions at the smaller geographical scale will be crucial tools in sustaining elimination.

Epidemiological survey of sheep as potential hosts for Leishmania in China

BackgroundLeishmania parasites cause visceral leishmaniasis (VL), an important infectious disease that is endemic to large parts of the world and often leads to epidemics. Sand flies are the primary transmission vector for the parasite in endemic regions. We hypothesized that sheep might serve as an overlooked reservoir for Leishmania transmission to humans due to the asymptomatic nature of infection in many species. As a preliminary test of this hypothesis, the aim of the present study was to investigate sheep in an area of China that is endemic for the desert sub-type of zoonotic VL and establish if they are potential carriers of Leishmania.ResultsSheep tissue samples were collected from abattoirs in VL endemic areas of Jiashi County, China during the non-transmission season. rK39 immunochromatographic tests were performed to detect the presence of the parasite in blood samples. In addition, DNA was extracted from the blood, and used for detection of the Leishmania-specific internal transcribed spacer-1 (ITS-1) genomic region using a nested polymerase chain reaction (PCR) approach. PCR products were further analyzed to identify restriction fragment-length polymorphism patterns and representative sequences of each pattern were selected for phylogenetic analysis. The rK-39 and nested PCR data indicated positive detection rates for Leishmania in sheep of 26.32 and 54.39%, respectively. The phylogenetic analysis revealed that all of the samples belonged to the species L. infantum and were closely related to strains isolated from human infections in the same area.ConclusionsSheep could be a potential host for Leishmania in VL endemic areas in China and may be an overlooked reservoir of human VL transmission in this region. To further confirm livestock as a potential host, further verification is required using a sand fly biting experiment.

Asymptomatic Visceral Leishmania infantum Infection in US Soldiers Deployed to Iraq.

Visceral leishmaniasis (VL), due to Leishmania infantum, is a persistent intracellular parasitic infection transmitted by the bite of infected sand flies. Symptomatic VL has been reported in U.S. soldiers with Iraq deployment. Untreated symptomatic VL can be fatal; asymptomatic VL (AVL) may establish a lifelong risk of reactivation. We report prevalence and AVL risk factors in Operation Iraqi Freedom (OIF) deployers during 2002-11. Healthy soldiers exposed to VL endemic areas in Iraq and 50 controls who never traveled to endemic regions were recruited through military healthcare facilities (2015-17). Responses to a risk factor survey and blood samples were obtained. Leishmania research diagnostics utilized included enzyme-linked immunosorbent assay (ELISA), rk39 test strips, quantitative polymerase chain reaction (PCR), and interferon gamma release (IGRA) assays. Statistical analyses included Fisher exact test, Pearson χ2 test, Mann-Whitney U test, and logistic regression. 200 deployed subjects were enrolled, mostly males (84.0%), of white ethnicity (79.0%), and median age 41 (range 24-61) years. 64% were seropositive for Phlebotomus alexandri saliva antibodies. Prevalence of AVL (any positive test result) was 39/200 (19.5%, 95% confidence interval 14.4%-25.8%). Two (1.0%) PCR, 10 (5%) ELISA, and 28 (14%) IGRA samples were positive. Travel to Ninewa governorate increased risk for AVL (P = .01). AVL was identified in 19.5% of OIF deployers; travel to northwest Iraq correlated with infection. Further studies are needed to inform risk for reactivation VL in US veterans and to target additional blood safety and surveillance measures.

Validity of Katex Test for Diagnosis of Visceral Leishmaniasis

Background: Newly developed KAtex test can be used as a non invasive tool for diagnosis of Kala-azar.Objectives: The aim of the present study was to validate the KAtex method to diagnose VL.Methodology: This was a cross-sectional study carried out in the Department of Microbiology at Dhaka Medical College, Dhaka, Bangladesh in collaboration with the department of Parasitology at Institute of Epidemiology, Disease control and Research (IEDCR), Dhaka, Bangladesh for a period of one year. Clinically suspected Kala- azar (VL) cases of different age and sex attending IEDCR from different Kala-azar endemic areas of Bangladesh were selected for this study. Microscopy and culture was performed with Bone marrow (BM). KAtex was performed with urine sample. Urine samples taken from cases were pretreated to inactivate heat labile materials which might cause a false positive reaction. Antigen which is detected by KAtex is heat stable carbohydrate antigen. Latex sensitized with antibodies raised against Leishmania donovani antigen was mixed with the urine sample on a glass slide. No agglutination indicates absence of antigen in urine.Result: Cases were 130. Among 130 clinically suspected VL cases, 70 (53.85%) cases were BM positive and 60 (46.15%) cases were BM negative. All the 70 BM positive cases were positive by KAtex. Among 60 BM negative cases, 15 were positive by KAtex. The sensitivity of KAtex is 100% and specificity is 75%. Highest percentage (52.86%) of bone marrow positive cases were below 10 years of age group.Conclusion: In conclusion, KAtex test is a good diagnostic tool for the detection of VL.Bangladesh Journal of Infectious Diseases, December 2017;4(2):45-47

Molecular Diagnosis of Visceral Leishmaniasis.

Visceral leishmaniasis (VL), a deadly parasitic disease, is a major public health concern globally. Countries affected by VL have signed the London Declaration on Neglected Tropical Diseases and committed to eliminate VL as a public health problem by 2020. To achieve and sustain VL elimination, it will become progressively important not to miss any remaining cases in the community who can maintain transmission. This requires accurate identification of symptomatic and asymptomatic carriers using highly sensitive diagnostic tools at theprimary health service setting. The rK39 rapid diagnostic test (RDT) is the most widely used tool and with its good sensitivity and specificity is the first choice for decentralized diagnosis of VL in endemic areas. However, this test cannot discriminate between current, subclinical, or past infections and is useless for diagnosis of relapses and as a prognostic (cure) test. Importantly, as the goal of elimination of VL as a public health problem is approaching, the number of people susceptible to infection will increase. Therefore, correct diagnosis using a highly sensitive diagnostic test is crucial for applying appropriate treatment and management of cases. Recent advances in molecular techniques have improved Leishmania detection and quantification, and therefore this technology has become increasingly relevant due to its possible application in a variety of clinical sample types. Most importantly, given current problems in identifying asymptomatic individuals because of poor correlation between the main methods of detection, molecular tests are valuable for VL elimination programs, especially to monitor changes in burden of infection in specific communities. This review provides a comprehensive overview of the available VL diagnostics and discusses the usefulness of molecular methods in the diagnosis, quantification, and species differentiation as well as their clinical applications.