Fast multiplex real-time PCR assay for simultaneous detection of dog and human blood and Leishmania parasites in sand flies

Evidence of Incomplete Feeding Behaviors among South Carolina Tick Populations

Dynamic environmental conditions, such as climate change and host availability, have greatly influenced the expansion of medically relevant tick vectors into new regions throughout the southeastern United States of America. As tick populations migrate into new areas, it has been suggested they can exhibit a phenomenon known as incomplete feeding. With this phenomenon, tick vectors feed on more than one host at each life stage, thus increasing the likelihood of pathogen transmission. Although this behavior is not well understood, it presents an important threat to human health. Here we present evidence of incomplete feeding behaviors in multiple tick species in South Carolina. Engorged, blood-fed female ticks were collected from feral dogs at animal shelters across South Carolina in 2022. All ticks were tested for human blood meals using rapid stain identification blood tests. Approximately one third (33.78%) of all ticks tested positive for a human blood meal, with various patterns seen across species, geographic location, and collection month. The results of this pilot study follow the current national trend of increasing rates of tick-borne disease incidence in the southeastern United States of America and warrant further investigation into the relationship between seasonality, geographic distribution, species, and incomplete feeding among tick populations in South Carolina.

Invasive Haemaphysalis longicornis (Acari: Ixodidae) investigation in South Carolina: new records of establishment, pathogen prevalence, and blood meal analyses

The first established population of the Asian longhorned tick Haemaphysalis longicornis (Neumann, Acari: Ixodidae) was discovered in a northern South Carolina county in June 2022. A coordinated investigation was launched to investigate the invasive tick's pathogen infection prevalence and blood meal preferences. Almost 2,000 Ha. longicornis ticks were collected from one cattle field. A majority of collected ticks had evidence of cattle and dog blood meals, and multiple samples were tested positive for Borrelia burgdorferi s.l. and Theileria orientalis-first reports for these pathogens in this tick species in South Carolina. This investigation was the direct result of a collaborative education campaign and tick surveillance program launched earlier in the year with multiple state partners.

Effective immuno-therapeutic treatment of Canine Leishmaniasis

BACKGROUND

Canine Leishmaniasis (CanL) caused by the L. infantum species is one of the biggest threats to the health of the South American canine population. Chemotherapeutics currently used for the treatment of CanL fail to induce a total parasite clearance while inducing numerous side effects. As CanL is an immunomodulated disease, the use of immuno-treatments should strengthen the deficient immune response of infected dogs. In this study, we evaluated a nasally administered immunotherapy in dogs naturally infected with L. infantum (stage 2), with both visceral and cutaneous manifestations. Noteworthy, some of them were also infected by other parasites (E. canis, D. immitis, A. platys), what worsen their chance of survival.

METHODOLOGY/PRINCIPAL FINDINGS

The treatment was based on 2 intranasal (IN.) administrations of a killed L. infantum parasite loaded into maltodextrin nanoparticles, which treatment was compared with the classical oral administration of Miltefosine (2 mg/kg) for 28 days, as well as a combination of these 2 treatments. The results showed that two IN administrations significantly reduced the serology, and were at least as efficient as the chemotherapy to reduce the skin and bone marrow parasite burden, as well as clinical scores, and that unlike Miltefosine treatments, this nasally administered nanoparticle vaccine was without side effects.

CONCLUSIONS

These results confirm the feasibility of a simple therapeutic immuno-treatment against L. infantum infected dogs, which is a promising tool for future developments.

Leishmania V. braziliensis infection in asymptomatic domestic animals within an endemic region in the Northeast of Brazil

Background:

American cutaneous leishmaniasis is a commonly neglected, vector-borne tropical parasitic disease that is a major public health concern in Brazil. Leishmania (Viannia) braziliensis is the main species associated with the disease. Accurate diagnosis is based on epidemiological surveillance, clinical assessment, and laboratory testing. Leishmania (V.) braziliensis has been detected in several wild and synanthropic mammals. Their epidemiological role has not been entirely elucidated. This study aimed to assess potential L. braziliensis infections in asymptomatic domestic animals, by molecular and serological testing in endemic areas, in the metropolitan region of Recife.

Methods:

Blood samples and conjunctival fluids were collected from 232 animals (canids, felids, equines, and caprines) for the detection of L. braziliensis using molecular tests (conventional and real-time polymerase chain reaction [PCR and qPCR]). For immunological detection, blood samples from 115 dogs were assessed using enzyme-linked immunosorbent assay.

Results:

Real-time quantitative PCR showed positive results for blood and conjunctival samples in all investigated species. The results of the blood and conjunctival samples were 68.2% and 26.9% in Canis familiaris, 100% and 41.7% in Felis catus, 77.3% and 30.8% in Equus caballus/Equus asinus, and 50% and 33.3% in Capra hircus samples, respectively.

Conclusions:

Results from this study adds valuable information to our understanding of the role of asymptomatic domestic animals, L. braziliensis life cycle, and American cutaneous leishmaniasis in Northeast Brazil.

Concurrent molecular characterization of sand flies and Leishmania parasites by amplicon-based next-generation sequencing

BACKGROUND

Phlebotomine sand flies are vectors of Leishmania parasites, which are the causative agents of leishmaniasis. Herein, we developed an amplicon-based next-generation sequencing (Amp-NGS) to characterize sand flies and Leishmania parasites simultaneously targeting partial fragments of 18S rDNA and ITS1 genes, respectively.

METHODS

Our assay was optimized using reference sand fly (n = 8) and Leishmania spp. (n = 9) samples and validated using wild-caught sand flies from Palestine. The assay was highly specific, and all DNA references were successfully identified to the species level.

RESULTS

Among the wild-caught sand flies (n = 187), Phlebotomus spp. represented 95% of the collected samples (177/187), including Ph. sergenti (147/187, 79%), Ph. papatasi (19/187, 10.2%), Ph. perfiliewi (3/187, 1.6%), Ph. tobbi (2/187, 1.2%) and Ph. syriacus (6/187, 3.2%). Sergentomyia spp. represented only 5% (10/187) of the collected samples and included S. dentata (n = 6), S. fallax (n = 2), S. schwetzi (n = 1) and S. ghesquiere (n = 1). The study observed strong positive correlation between sand fly identification results of the Amp-NGS and morphological identification method (r = 0.84, df = 185, P < 0.001). Some discrepancies between the two methods in the identification of closely related species (i.e. Ph. perfiliewi, Ph. tobbi and Ph. syriacus) were observed. Leishmania DNA was detected and identified as L. tropica in 14 samples (14/187, 7.5%).

CONCLUSIONS

Our assay was sensitive to detect (limit of detection was 0.0016 ng/reaction) and identify Leishmania DNA in sand flies, thus representing a new tool for studying sand flies and their associated Leishmania parasites in endemic areas.

Ornithodoros cf. mimon infected with a spotted fever group Rickettsia in Brazil

Ornithodoros mimon is an argasid tick primarily associated with bats that also infest other animals including birds, opossums and humans. In this paper, we report the finding of an argasid species resembling O. mimon, which similarly may be found in human dwellings and parasitize humans in Brazil. We also provide molecular evidence that this argasid tick species may carry a rickettsial organism, whose pathogenicity remains unknown. A total of 16 ticks (two females, two males and 12 nymphs) were collected in the bedroom and in the attic of a human house, where cases of "insect" bites have been recurrent. These ticks were identified morphologically and genetically as Ornithodoros cf. mimon. Upon PCR testing, four of these ticks (one female and three nymphs) were positive for human blood and for a bacterium closely related to "Candidatus Rickettsia paranaensis". In conclusion, we report for the first time in Brazil an argasid tick species morphologically and genetically related to O. mimon, which feeds on humans and carry a rickettsial organism belonging to the spotted fever group. Further studies are needed to formally assess the taxonomic status of this tick species and also to investigate the pathogenicity of its associated rickettsial organism.

Effects of Migonemyia migonei salivary gland homogenates on Leishmania (Viannia) braziliensis infection in BALB/c mice

Cutaneous leishmaniasis caused by Leishmania (Viannia) braziliensis is the most widespread clinical form of leishmaniasis in the Americas. Migonemyia migonei is a widely distributed phlebotomine sand fly species in Brazil and has been implicated as a vector for L. (V.) braziliensis. In the present study, we investigated the effects of salivary gland homogenates (SGH) of Mg. migonei on the course of L. (V.) braziliensis infection in BALB/c mice. Mice were separated into four groups (six mice per group): CTRL (uninfected mice); SGH (mice inoculated with Mg. migonei SGH); SGH+LEISH (mice inoculated with Mg. migonei SGH plus L. (V.) braziliensis promastigotes); LEISH (mice inoculated with L. (V.) braziliensis promastigotes). Mice were followed up for 8 weeks and the cellular immune response was evaluated by flow cytometry at the end of the experiment. Analysis of cytokine production by splenic cells stimulated with 0.5 SGH, 0.25 SGH of Mg. migonei or L. (V.) braziliensis soluble antigen stimulation (LSA) demonstrated that upon stimulation with SGH 0.25, the production of IL-17A and TNF was not sustained in the SGH group, with decreasing levels of these cytokines after 5 days compared to 3 days of incubation. Analyzing the production of cytokines after LSA stimulation, we observed lower levels of IL-17A in the SGH group after 5 days compared to 3 days. The same was observed for IFN-γ in the SGH group. Yet, the levels of TNF were significantly higher in the LEISH group after 5 days compared to 3 days. Among SGH+LEISH and LEISH mice, three animals in each group developed skin lesions on the tail, the mean lesion size was significantly higher in the LEISH group. Our study suggests that Mg. migonei SGH may modulate BALB/c immune response, as reflected by the low production or early decrease of pro-inflammatory cytokines in splenic cell cultures following stimulation with L. (V.) braziliensis antigen. Our data also suggest that Mg. migonei saliva may reduce the lesion size in BALB/c mice, but further research with a larger sample size is needed to confirm this hypothesis.

Beyond taxonomy: species complexes in New World phlebotomine sand flies

A species complex (= species group, species series) is an assemblage of species, which are related morphologically and phylogenetically. Recent research has revealed several arthropod vector species that were believed to be a single nominal species actually representing a group of closely related species, which are sometimes morphologically indistinguishable at one or more developmental stages. In some instances, differences in terms of vector competence, capacity, or both have been recorded. It highlights the importance of detecting and studying species complexes to improve our understanding of pathogen transmission patterns, which may be vectored more or less efficiently by different species within the complex. Considering more than 540 species, about one-third of the phlebotomine sand flies in the New World present males and/or females morphologically indistinguishable to one or more species. Remarkably, several of these species may act in transmission of pathogenic agents. In this article, we review recent research on species complexes in phlebotomine sand flies from the Americas. Possible practical implications of recently acquired knowledge and future research needs are also discussed.

No molecular evidence of SARS-CoV-2 infection in companion animals from Veracruz, Mexico

Active epidemiological surveillance of infectious agents represents a fundamental tool for understanding the transmission dynamics of pathogens and establishing public policies that can reduce or limit their expansion. Epidemiological surveillance of emerging agents, such as the recently recognized severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the cause of COVID-19, is essential to establish the risk of transmission between species. Recent studies reveal that companion animals are organisms susceptible to being infected by this pathogen due to the close contact they have with their owners. For this reason, the aim of the present work was to detect the presence of SARS-CoV-2 in dogs and cats in the state of Veracruz, Mexico, where there is active transmission of this microorganism in human populations. Oral and nasopharyngeal swab samples were collected from dogs and cats with a history of exposure to patients with COVID-19. Total RNA was extracted and detection of viral genes N1 and N2 was performed by reverse transcription polymerase chain reaction (RT-qPCR). All 130 samples of companion animals tested by RT-qPCR for SARS-CoV-2 were negative at the time they were collected. This study represents the second active surveillance of SARS-CoV-2 in populations of domestic dogs and cats in Latin America and the first approach in Mexico. Given that coronaviruses have shown a high capacity to be transmitted between species, it is imperative to establish measures to prevent this agent from entering and establishing in populations of companion animals.

Molecular diagnosis of infectious parasites in the post-COVID-19 era

The endemicity of several parasitic diseases across the globe and recent evidence of distress among COVID-19 patients with preexisting parasitic infections requires strengthening One Health framework and advanced strategies for parasitic detection. Owing to the greater sensitivity and accuracy, molecular technologies such as conventional polymerase chain reaction (PCR), reverse transcription (RT)-PCR, nested PCR, loop-mediated isothermal amplification (LAMP), and xMAP technology have been extensively studied for parasitic diagnosis. Varieties of genes have been targeted for primer development where 18S rRNA, internal transcribed spacer regions, and mitochondrial DNAs coding for cytochrome, and other enzymes have been widely used. More recent, low-cost sequencing and advances in big data management have resulted in a slow but steady rise of next-generation sequencing-based approaches for parasite diagnosis. However, except for few parasites of global concerns such as Plasmodium and Entamoeba, most of the molecular tools and technologies are yet to witness bench to bedside and field translations. This review looks into some of the advancements in the molecular diagnosis of parasites that have potential relevance to clinical purposes and may pave the way toward disease management in an efficient and timely manner.

Modernizing the Toolkit for Arthropod Bloodmeal Identification

Simple Summary

The ability to identify the source of vertebrate blood in mosquitoes, ticks, and other blood-feeding arthropod vectors greatly enhances our knowledge of how vector-borne pathogens are spread. The source of the bloodmeal is identified by analyzing the remnants of blood remaining in the arthropod at the time of capture, though this is often fraught with challenges. This review provides a roadmap and guide for those considering modern techniques for arthropod bloodmeal identification with a focus on progress made in the field over the past decade. We highlight genome regions that can be used to identify the vertebrate source of arthropod bloodmeals as well as technological advances made in other fields that have introduced innovative new ways to identify vertebrate meal source based on unique properties of the DNA sequence, protein signatures, or residual molecules present in the blood. Additionally, engineering progress in miniaturization has led to a number of field-deployable technologies that bring the laboratory directly to the arthropods at the site of collection. Although many of these advancements have helped to address the technical challenges of the past, the challenge of successfully analyzing degraded DNA in bloodmeals remains to be solved.

Abstract

Understanding vertebrate–vector interactions is vitally important for understanding the transmission dynamics of arthropod-vectored pathogens and depends on the ability to accurately identify the vertebrate source of blood-engorged arthropods in field collections using molecular methods. A decade ago, molecular techniques being applied to arthropod blood meal identification were thoroughly reviewed, but there have been significant advancements in the techniques and technologies available since that time. This review highlights the available diagnostic markers in mitochondrial and nuclear DNA and discusses their benefits and shortcomings for use in molecular identification assays. Advances in real-time PCR, high resolution melting analysis, digital PCR, next generation sequencing, microsphere assays, mass spectrometry, and stable isotope analysis each offer novel approaches and advantages to bloodmeal analysis that have gained traction in the field. New, field-forward technologies and platforms have also come into use that offer promising solutions for point-of-care and remote field deployment for rapid bloodmeal source identification. Some of the lessons learned over the last decade, particularly in the fields of DNA barcoding and sequence analysis, are discussed. Though many advancements have been made, technical challenges remain concerning the prevention of sample degradation both by the arthropod before the sample has been obtained and during storage. This review provides a roadmap and guide for those considering modern techniques for arthropod bloodmeal identification and reviews how advances in molecular technology over the past decade have been applied in this unique biomedical context.

Evaluation of different storage times and preservation methods on phlebotomine sand fly DNA concentration and purity

Background

Different methods have been used to preserve phlebotomine sand flies for research purposes, including for taxonomic studies and detection of Leishmania spp. Here, we evaluated the effect of various preservation methods at different storage times on phlebotomine sand fly DNA concentration and purity.

Methods

Field-collected phlebotomine sand flies were individually stored in 70% ethanol (G1) and 95% ethanol (G2) at room temperature, 70% ethanol (G3) and 95% ethanol (G4) at 8 °C or frozen dry (i.e. no preservation solution) at − 20 °C (G5). DNA concentration and purity were assessed at various storage times (T1, ≤ 12 h; T2, 3 months; T3, 6 months; T4, 9 months; and T5, 12 months). Fragments of the cytochrome c oxidase subunit 1 (cox1) and cacophony (CAC) genes of phlebotomine sand flies were also amplified.

Results

Mean DNA concentration (P = 0.178) and 260/280 purity ratios (P = 0.584) did not vary significantly among various preservation methods and storage times. Within each group, DNA concentration varied in G1 (Kruskal-Wallis H-test, P = 0.009) for T3 vs T4 (Dunn’s post-hoc, P < 0.05), and in G2 (Kruskal-Wallis H-test, P = 0.004) for T1 vs T2 and T1 vs T4 (Dunn’s post-hoc, P < 0.05). For 260/280 purity ratios, the only statistically significant difference was found for G5 (Kruskal-Wallis H-test, P = 0.020) between T1 vs T4 (Dunn’s post-hoc test, P < 0.05). The cox1 and CAC genes were successfully amplified, regardless of the preservation method and storage time; except in one sample from G2 at T1, for which the CAC gene failed to amplify.

Conclusions

The preservation methods and storage times herein evaluated did not affect the concentration and purity of DNA samples obtained from field-collected phlebotomine sand flies, for up to 12 months. Furthermore, these preservation methods did not interfere with PCR amplification of CAC and cox1 genes, being suitable for molecular analyses under the conditions studied herein.