Utility of the microculture method for Leishmania detection in non-invasive samples obtained from a blood bank

The immune response in canine and human leishmaniasis and how this influences the diagnosis- a review and assessment of recent research

Leishmaniasis is a widespread but still underdiagnosed parasitic disease that affects both humans and animals. There are at least 20 pathogenic species of Leishmania, most of them being zoonotic. The diagnosis of leishmaniasis remains a major challenge, with an important role being played by the species of parasites involved, the genetic background, the immunocompetence of the host. This paper brings to the fore the sensitivity of the balance in canine and human leishmaniasis and addresses the importance of the host's immune response in establishing a correct diagnosis, especially in certain cases of asymptomatic leishmaniasis, or in the situation the host is immunosuppressed or acquired leishmaniasis through vertical transmission. The methods considered as a reference in the diagnosis of leishmaniasis no longer present certainty, the diagnosis being influenced mostly by the immune response of the host, which differs according to the presence of other associated diseases or even according to the breed in dogs. Consequently, the diagnosis and surveillance of leishmaniasis cases remains an open topic, requiring new diagnostic methods adapted to the immunological state of the host.

Asymptomatic Leishmania infection in humans: A systematic review

BACKGROUND

Leishmaniasis is a highly prevalent neglected tropical disease. It mainly presents as two forms: cutaneous and visceral leishmaniasis, the latter being the most severe form. However, asymptomatic cases of Leishmania infection result in an increase in the underreporting and transmission of the protozoan OBJECTIVES: In this study, articles on the incidence of asymptomatic Leishmania infection were systematically reviewed.

METHODS

The publications identified in the Medline/PubMed and Science Direct databases included 4568 articles. Inclusion, exclusion, and eligibility criterion analysis resulted in 83 articles being retained. These studies were mostly performed in Brazil (n = 26) and India (n = 15).

RESULTS

Several detection techniques have been used for diagnosis. Among the species found were L. infantum and L. donovani, which result in visceral leishmaniasis, and L. amazonensis, L. braziliensis, and L. panamensis. The incidence rates varied between the analyzed locations, largely due to sampling and the presence or absence of endemism in the regions. The largest populations analyzed were in two studies performed in India and Nepal. One of these studies evaluated 32,529 people and the incidence rate was 8.3% (n = 2702), while the other study evaluated 21,267 people and the incidence rate was 1.76% (n = 375). Only 14.28% of the studies investigated leishmaniasis in blood donors. Preexisting diseases have also been reported.

CONCLUSION

The findings of this systematic review present the incidence of cases of asymptomatic Leishmania infection worldwide, in addition to detailing the studies and offering information for researchers and health authorities to seek alternatives to reduce the number of leishmaniasis cases.

A Convenient and Sensitive kDNA-PCR for Screening of Leishmania infantum Latent Infection Among Blood Donors in a Highly Endemic Focus, Northwestern Iran

BACKGROUND

Recent global evidences showed that asymptomatic blood donor carriers of Leishmania infection will appear as a threat for blood transfusions recipients in endemic areas. As yet, there is no appropriate diagnostic procedure for detecting infection of blood donors in blood banks.

SUBJECTS AND METHODS

The present study was aimed to apply various current diagnostic tests among blood donors in an endemic area of visceral leishmaniasis (VL), Ardabil Province, northwestern Iran. Blood samples were gathered from 860 blood donors in endemic areas of the province between 2017 and 2018, at eight blood donation centers. These samples was assessed using microculture, serological (DAT and rK39-ICT) and molecular based (conventional kDNA-PCR and HRM-PCR) tests.

RESULTS

Of 860 eligible donors, 24 (2.8%) were seropositive for VL by DAT, and 388 (45%) were positive by kDNA-PCR. Moreover, 19 (19/860) were positive for both of them. Out of 19 subjects, 5.3% (1/19) was positive by rK39-ICT, 10.5% (2/19), and 79% (15/19) were detected positive in microculture and HRM-PCR methods, respectively. Nineteen donors were followed up for 2 years, of which 16 (84.2%) had a serological conversion, and 4 (21%) were positive by kDNA-PCR. The sensitivity of kDNA-PCR, and HRM-PCR procedures in detecting Leishmania parasite was found to be 98.7%, and 79%, respectively.

CONCLUSIONS

Our findings justify the use of kDNA-PCR as a convenient and sensitive tool for screening subjects with leishmanial latent infection in blood banks at least in endemic regions. In these areas, however, a PCR-based test should be used to validate Leishmania infection among seropositive donors.

The current epidemiology of leishmaniasis in Turkey, Azerbaijan and Georgia and implications for disease emergence in European countries

Leishmania spp. are sand fly-borne protozoan parasites causing leishmaniasis in humans and animals. The aim of the study was to analyse the epidemiology of leishmaniasis in Turkey, Azerbaijan and Georgia from 2005 to 2020 and evaluate the associated risk for disease emergence in European countries. It is based on an analysis of WHO and OIE reported cases between 2005 and 2020, a review of scientific articles published in SCOPUS between 2009 and 2020 and a questionnaire survey to public health and veterinary authorities in these countries. Endemic Leishmania spp. include L. infantum in the three countries, L. major in Azerbaijan and Turkey and L. tropica and L. donovani in Turkey. Leishmaniasis is reported in humans, animals and sand flies and incidence is spatially and temporarily variable. In the southern Caucasus and particularly in Georgia, reported incidence of human visceral leishmaniasis by L. infantum remains high. However, whilst Georgia experienced a gradual decrease from >4.0 cases per 100,000 population in 2005-09 to 1.13 cases per 100,000 population in 2020, the period with highest incidence in Azerbaijan, which ranged between 0.40 and 0.61 cases per 100,000 population, was 2016-2019, and no cases have so far been reported for 2020. Visceral leishmaniasis in the Southern Caucasus affects mostly young children from deprived urban areas and its closely associated to canine leishmaniasis. Turkey reported cases of visceral leishmaniasis between 2005 and 2012 and in 2016 only, and incidence ranged between 0.02 and 0.05 per 100,000 population. In contrast, the reported annual incidence of cutaneous leishmaniasis in Turkey was much greater and peaked at 7.02 cases per 100,000 population in 2013, associated to imported cases from cutaneous leishmaniasis endemic Syria. Leishmaniasis by L. infantum in Azerbaijan and Georgia represents a regional public and animal health challenge that requires support to improve diagnosis, treatment and control. The unprecedented rise of cutaneous leishmaniasis and the spread of L. tropica and L. donovani in Turkey is an important risk factor for their emergence in Europe, especially in Mediterranean countries where competent vectors are widespread.

Identification of asymptomatic Leishmania infections: a scoping review

BACKGROUND

Asymptomatic Leishmania infection may play an important role in the transmission of the parasite in endemic areas. At present there is no consensus on the definition of asymptomatic Leishmania infection, nor is there a safe and accessible gold standard test for its identification.

METHODS

This paper presents a scoping review to summarize definitions of asymptomatic Leishmania infection found in the literature, as well as to detail the approach (molecular, serological, cellular, and/or parasitological tests) used by researchers to identify this asymptomatic population. A scoping review of published and gray literature related to asymptomatic Leishmania infection was conducted; retrieved citations were screened based on predefined eligibility criteria, and relevant data items were extracted from eligible articles. The analysis is descriptive and is presented using tables, figures, and thematic narrative synthesis.

RESULTS

We conducted a screening of 3008 articles, of which 175 were selected for the full review. Of these articles, we selected 106 that met the inclusion criteria. These articles were published between 1991 and 2021, and in the last 5 years, up to 38 articles were reported. Most of the studies were conducted in Brazil (26%), Spain (14%), India (12%), Bangladesh (10%), and Ethiopia (7%). Of the studies, 84.9% were conducted in the immunocompetent population, while 15.1% were conducted in the immunosuppressed population (HIV, immunosuppressive drugs, and organ transplantation population). We report 14 different techniques and 10 strategies employed by researchers to define asymptomatic Leishmania infection in an endemic area.

CONCLUSIONS

The definition of asymptomatic Leishmania infection is not unified across the literature, but often includes the following criteria: residence (or extended stay) in a Leishmania-endemic area, no reported signs/symptoms compatible with leishmaniasis, and positive on a combination of serological, molecular, cellular, and/or parasitological tests. Caution is recommended when comparing results of different studies on the subject of asymptomatic infections, as the reported prevalence cannot be confidently compared between areas due to the wide variety of tests employed by research groups. More research on the importance of asymptomatic immunosuppressed and immunocompetent Leishmania-positive populations in leishmaniasis epidemiology is required.

Leishmaniasis Diagnosis via Metagenomic Next-Generation Sequencing

Leishmaniasis is a vector-borne disease caused by Leishmania. Although the incidence of leishmaniasis in China is currently low, it has not been completely eradicated. In 2019, visceral leishmaniasis was diagnosed in three patients using bone marrow microscopic examination and metagenomic next-generation sequencing (mNGS). The bone marrow mNGS results from the three patients indicated that 99.9, 99.6, and 30.3% of non-human reads matched the Leishmania genome, and plasma mNGS results from one of the patients revealed that 46.2% of non-human reads matched the Leishmania genome. In the second patient's plasma, no Leishmania sequences were detected by plasma mNGS, and the third patient's plasma was unavailable. The pathogen in all three patients was identified as Leishmania infantum. Leishmania amastigotes were observed by microscopic examination of bone marrow smears in all three patients, but were not found in peripheral blood smears. This indicates that the sensitivity of mNGS is higher than that of smear microscopy and that mNGS can be used to identify Leishmania at the species level. All three patients were elderly male farmers, two from Shanxi and one from Beijing. All three patients had splenomegaly and pancytopenia. Originally, these patients were misdiagnosed and treated for extended periods in other hospitals. Diagnoses of visceral leishmaniasis took place 6, 2, and 2 months after the onset of symptoms in the three patients. In conclusion, this study confirms that bone marrow mNGS can be used to quickly and accurately confirm a diagnosis in patients with suspected leishmaniasis.

Global status of visceral leishmanial infection among blood donors: A systematic review and meta-analysis

INTRODUCTION

Transmission of Leishmania through transfusion has been reported from various Visceral leishmaniasis (VL) endemic areas of the world. The true burden of Leishmania infection in blood donors remains generally unknown. Thus, the present systematic review attempted to determine the global prevalence of Leishmania infection among blood donors.

METHODS

Data were extracted through five English and five Persian databases during the period from 1997 to 2016. Overall, 16 articles fulfilled the inclusion criteria and were used for data extraction in this systematic review.

RESULTS

In total, 13,743 blood donors from different regions of world were examined. The prevalence rate of Leishmania infection according to seropositivity obtained 7% (95%CI: 5%, 8%). The lowest and the highest prevalence were related to Bangladesh 0.25% (95%CI: 0.0%, 1.0%) and Brazil, 16% (95%CI: 12%, 19%). Seroprevalence rate of leishmaniasis among females was more (4.60%) than males. Of 15 studies included in the meta-analysis, the pooled prevalence rate of molecular tests was obtained 2% (95%CI: 1%, 3%) in which Iran and Spain had the lowest and the highest prevalence, 0.05% and 7%, respectively. Our analysis showed that L. infantum was more common than L. donovani as etiological agent of VL among all donors.

CONCLUSION

Our data confirms the presence of asymptomatic carriers of VL in endemic areas and supplies as an attentive to the likelihood of these carriers acting as blood donors. Moreover, we conclude that molecular tests for screening in asymptomatic blood donor provide an accurate estimate of the rate of infection over serological tests.

A new approach for development of vaccine against visceral leishmaniasis: Lipophosphoglycan and polyacrylic acid conjugates

OBJECTIVE

To determine the antileishmanial vaccine effectiveness of lipophosphoglycan (LPG) and polyacrylic acids (PAA) conjugates on in vivo mice models.

METHODS

LPG molecule was isolated and purified from large-scale Leishmania donovani parasite culture. Protection efficacies of LPG alone, in combination with Freund's adjuvant, in a physical mixture and in conjugate (consisting of various LPG concentrations) with PAA, were comparatively determined by various techniques, such as cultivation with the micro-culture method, assessment of in vitro infection rates of peritoneal macrophages, determination of parasite load in liver with Leishman-Donovan Units, and detection of cytokine responses.

RESULTS

Obtained results demonstrated that the highest vaccine-mediated immune protection was provided by LPG-PAA conjugate due to all parameters investigated. According to the Leishman-Donovan Units results, the sharpest decline in parasite load was seen with a ratio of 81.17% when 35 μg LPG containing conjugate was applied. This value was 44.93% for the control group immunized only with LPG. Moreover, decreases in parasite load were 53.37%, 55.2% and 65.8% for the groups immunized with 10 μg LPG containing LPG-PAA conjugate, a physical mixture of the LPG-PAA, and a mixture of LPG + Freund's adjuvant, respectively. Furthermore, cytokine results supported that Th1 mediated protection occurred when mice were immunized with LPG-PAA conjugate.

CONCLUSIONS

It has been demonstrated in this study that conjugate of LPG and PAA has an antileishmanial vaccine effect against visceral leishmaniasis. In this respect, the present study may lead to new vaccine approaches based on high immunogenic LPG molecule and adjuvant polymers in fighting against Leishmania infection.

Asymptomatic human blood donors carriers of Leishmania infantum: Potential reservoirs for visceral leishmaniasis in northwestern Iran

BACKGROUND

Little is known regarding transfusion-transmitted leishmaniasis (TTL) and the real global incidence of visceral leishmaniasis (VL) among blood donors as carriers of Leishmania spp. in endemic VL foci including Iran. Recent epidemiological evidences indicate that blood donor may be harbor of Leishmania infantum (L. infantum) infection in Iran.

METHODS

The aim of the present study was to determine the prevalence of Leishmania infection among blood donors in a main endemic focus of VL in Iran using DAT and polymerase chain reaction (PCR) based methods Between July-September 2016, blood samples were collected from 600 apparently healthy blood donors from six blood donation centers and blood donation mobile unit in Ardabil Province, where VL cases had been recorded. Each of these samples was tested for anti-Leishmania antibodies, in direct agglutination test (DAT), and for L. infantum kDNA, the PCR-based assay.

RESULTS

Of 600 blood donors, which were examined, 23 (3.8%) blood donors were seropositive by DAT and of 23 seropositive subjects, 82.6% (19/23) were positive by PCR. All the seropositive cases were males except one of them was female.

CONCLUSIONS

Our findings showed that many asymptomatic human carriers of L. infantum live in the endemic regions of northwestern Iran and potentially act as reservoirs of infection; those must be considered carefully by arrangement VL control strategies in the country.

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.

A screen-and-treat strategy targeting visceral leishmaniasis in HIV-infected individuals in endemic East African countries: the way forward?

In the wake of the HIV epidemic, visceral leishmaniasis (VL), a disseminated protozoan infection caused by the Leishmania donovani complex, has been re-emerging, particularly in North Ethiopia where up to 40% of patients with VL are co-infected with HIV. Management of VL in HIV co-infection is complicated by increased drug toxicity, and high treatment failure and relapse rates with all currently available drugs, despite initiation of antiretroviral treatment. Tackling L. donovani infection before disease onset would thus be a logical approach. A screen-and-treat approach targeting latent or the early stage of infection has successfully been implemented in other HIV-associated opportunistic infections. While conceptually attractive in the context of VL-HIV, the basic understanding and evidence underpinning such an approach is currently lacking. Prospective cohort studies will have to be conducted to quantify the risk of VL in different risk groups and across CD4 cell count levels. This will allow developing clinical prognostic tools, integrating clinical, HIV and Leishmania infection markers. Interventional studies will be needed to evaluate prophylactic or pre-emptive treatment strategies for those at risk, ideally relying on an oral (combination) regimen. Issues like tolerability, emergence of resistance and drug interactions will require due attention. The need for maintenance therapy will have to be assessed. Based on the risk-benefit data, VL risk cut-offs will have to be identified to target treatment to those most likely to benefit. Such a strategy should be complemented with early initiation of antiretroviral treatment and other strategies to prevent HIV and Leishmania infection.