Intricate balance of dually-localized catalase modulates infectivity of Leptomonas seymouri (Kinetoplastea: Trypanosomatidae).

Nearly all aerobic organisms are equipped with catalases, powerful enzymes scavenging hydrogen peroxide and facilitating defense against harmful reactive oxygen species. In trypanosomatids, this enzyme was not present in the common ancestor, yet it had been independently acquired by different lineages of monoxenous trypanosomatids from different bacteria at least three times. This observation posited an obvious question: why was catalase so "sought after" if many trypanosomatid groups do just fine without it? In this work, we analyzed subcellular localization and function of catalase in Leptomonas seymouri. We demonstrated that this enzyme is present in the cytoplasm and a subset of glycosomes, and that its cytoplasmic retention is H2O2-dependent. The ablation of catalase in this parasite is not detrimental in vivo, while its overexpression resulted in a substantially higher parasite load in the experimental infection of Dysdercus peruvianus. We propose that the capacity of studied flagellates to modulate the catalase activity in the midgut of its insect host facilitates their development and protects them from oxidative damage at elevated temperatures.

First record of Brachymeria amenocles (Hymenoptera: Chalcididae) associated with larvae of Peckia (Peckia) chrysostoma (Diptera: Sarcophagidae) in Brazil.

In this work, we report for the first time the occurrence of the parasitoid wasp Brachymeria amenocles (Walker, 1846) (Hymenoptera: Chalcididae) associated with the larvae of the flesh fly, Peckia (Peckia) chrysostoma (Wiedemann, 1830) (Diptera: Sarcophagidae), in Brazil. This parasitoid species was collected together with the species Brachymeria podagrica (Fabricius, 1787), in the municipality of Rio de Janeiro, geographically located in the Southeast region of Brazil, in larvae of the same host species reared in the same attraction substrate, behaving as solitary parasitoids. A trap containing putrefying sardine was exposed for 48 h, in the upper part of a house, located in Vila Isabel, an urban area. The larvae collected were reared in the laboratory without control of environmental conditions. A total of three adult parasitoid wasps of the species B. podagrica, and nine adult parasitoid wasps of the species B. amenocles emerged from 12 host pupae, resulting in a prevalence of parasitoidism of 4.8% and 14.5%, respectively. Developing parasitoids at the pupal phase were observed in another 34 host pupae dissected.

Aphaereta pallipes (Hymenoptera: Braconidae) and Dirhinus anthracia (Hymenoptera: Chalcididae) associated with Peckia (Euboettcheria) collusor (Diptera: Sarcophagidae) in Brazil.

Flies of the Sarcophagidae family are widely distributed in the world, occupying different habitats. Some species have a high degree of synanthropy and are therefore often found in households in the urban environment. In Brazil, there is still little information related to the natural enemies of these insects in the urban environment, where population control is strictly chemical. Therefore, larvae and pupae of Peckia (Euboettcheria) collusor (Curran and Walley) (Diptera: Sarcophagidae) species were exposed in an urbanized location, and the presence and prevalence of parasitoids in the natural control of these immature stages was evaluated. We report for the first time the species Aphaereta pallipes (Say) (Hymenoptera: Braconidae) and Dirhinus anthracia Walker (Hymenoptera: Chalcididae), associated with P. (E.) collusor, highlighting the importance of these parasitoids in natural control in the urban environment, in addition to expanding the list of hosts for both parasitoid species and the distribution of this parasitoid-host interaction for Brazil and the Neotropical region.

Ecdysone modulates both ultrastructural arrangement of hindgut and attachment of Trypanosoma cruzi DM 28c to the rectum cuticle of Rhodnius prolixus fifth-instar nymph.

Studies on the effects of azadirachtin treatment, ecdysone supplementation and ecdysone therapy on both the ultrastructural organization of the rectum in 5th-instar nymph of Rhodnius prolixus and the ex vivo attachment behavior of Trypanosoma cruzi under these experimental conditions were carried out. Control insects had a typical and significant organization of the rectum cuticle consisted of four main layers (procuticle, inner epicuticle, outer epicuticle, and wax layer) during the entire period of the experiment. Both azadirachtin treatment and ecdysone supplementation avoid the development of both outer epicuticle and wax layer. Oral therapy with ecdysone partially reversed the altered organization and induce the development of the four main rectal cuticle layers. In the same way, the ex vivo attachment of T. cruzi to rectal cuticle was blocked by azadirachtin treatment but ecdysone therapy also partially recovered the parasite adhesion rates to almost those detected in control insects. These results point out that ecdysone may be a factor responsible - directly or indirectly - by the modulation of rectum ultrastructural arrangement providing a superficial wax layer to the attachment followed by metacyclogenesis of T. cruzi in the rectum of its invertebrate hosts.

Action of Metarhizium brunneum (Hypocreales: Clavicipitaceae) Against Organophosphate- and Pyrethroid-Resistant Aedes aegypti (Diptera: Culicidae) and the Synergistic Effects of Phenylthiourea.

Dengue, yellow fever, Zika, and chikungunya arboviruses are endemic in tropical countries and are transmitted by Aedes aegypti. Resistant populations of this mosquito against chemical insecticides are spreading worldwide. This study aimed to evaluate the biological effects of exposure of pesticide-sensitive Ae. aegypti larvae (Rockefeller) to conidia of the entomopathogen, Metarhizium brunneum, laboratory strains ARSEF 4556 and V275, and any synergistic activity of phenylthiourea (PTU). In addition, to investigate the nature of any cross-resistance mechanisms, these M. brunneum strains were tested against the Rockefeller larvae and two temephos- and deltamethrin-resistant wild mosquito populations from Rio de Janeiro. Treatment of Rockefeller larvae with 106 conidia/ml of ARSEF 4556 and V275 fungal strains resulted in significant decreased survival rates to 40 and 53.33%, respectively (P < 0.0001), compared with untreated controls. In contrast, exposure to 104 or 105 conidia/ml showed no such significant survival differences. However, the addition of PTU to the conidia in the bioassays significantly increased mortalities in all groups and induced a molt block. Experiments also showed no differences in Ae. aegypti mortalities between the fungal treated, wild pesticide-resistant populations and the Rockefeller sensitive strain. The results show the efficacy of M. brunneum in controlling Ae. aegypti larvae and the synergistic role of PTU in this process. Importantly, there was no indication of any cross-resistance mechanisms between Ae. aegypti sensitive or resistant to pesticides following treatment with the fungi. These results further support using M. brunneum as an alternative biological control agent against mosquito populations resistant to chemical insecticides.

Exploring the Insecticide and Acaricide Potential of Development Regulators obtained from Restinga vegetation from Brazil.

As a part of our continuing search for insect and arthropod development regulators from Brazilian restinga vegetation of the Rio de Janeiro State, crude extracts, purified fractions and essential oils were submitted to screening tests seeking for biological activities on the development of the insects Rhodnius prolixus, Dysdercus peruvianus, Oncopeltus fasciatus and Rhipicephalus (Boophilus) microplus. Up to now, 102 secondary metabolites have been detected in the fractions, among them monoterpenes, sesquiterpenes and two triterpenes which were obtained from the species, Eugenia sulcata, Pilocarpus spicatus, Manilkara subsericea, Myrciaria floribunda and Zanthoxylum caribaeum. These secondary plant metabolites are considered of interest for the use of studies related to arthropod endocrinology, vector-parasite interaction system, and population control of vector insect and agricultural pest. The observed biological activities were surprisingly high, involving increased mortality, molting and metamorphosis inhibition, paralysis, corporeal deformities, apparition of permanent nymphs, of adultoids and juvenoids, partial or total inhibition of oviposition and egg hatching. These compounds are now being studied further to determine if they may or may not be useful in controlling insect populations and/or interfere with the life cycle and vector transmission of parasites to animal and human populations.

Lipoproteins from vertebrate host blood plasma are involved in Trypanosoma cruzi epimastigote agglutination and participate in interaction with the vector insect, Rhodnius prolixus.

Chagas disease, infecting ca. 8 million people in Central and South America, is mediated by the protozoan parasite, Trypanosoma cruzi. The parasite is transmitted by the bite of blood sucking triatomine insects, such as Rhodnius prolixus, that had previously fed on parasite-infected vertebrate blood and voided their contaminated feces and urine into the wound. The stages of the parasite life cycle in both the insect vector and human host are well-known, but determinants of infection in the insect gut are complex and enigmatic. This paper examines the possible role of the R. prolixus gut agglutinins in the parasite life cycle. The results, derived from gut extracts made from R. prolixus fed on various diets with different vertebrate blood components, and cross adsorption experiments, showed for the first time that R. prolixus has two distinct gut agglutinins originating from their vertebrate blood meal, one for T. cruzi (the parasite agglutinin, PA) and the other for the erythrocytes (the hemagglutinin, HA). Again, uniquely, the results also demonstrate that these two agglutinins are derived, respectively, from the plasma and erythrocyte components of the vertebrate blood. Subsequent experiments, examining in more detail the nature of the plasma components forming the T. cruzi PA, used fractionated extracts of the vertebrate plasma (high density lipoprotein, HDL; low density lipoprotein, LDL, and delipidated plasma) in agglutination assays. The results confirmed the identity of the PA as a high density lipoprotein (HDL) in the plasma of the vertebrate blood meal which agglutinates parasites in the R. prolixus gut. In addition, the use of single or double labeled HDL in fluorescence and confocal microscopy showed the interaction of the labeled HDL with the parasite surface and its internalization at later times. Finally, results of T. cruzi parasitization of R. prolixus, incorporating various vertebrate blood components, resulted in highly significant increases in infectivity in the presence of HDL from the 2nd day of infection, thus confirming the important role of this molecule in T. cruzi infection of R. prolixus.

Laboratory evaluation of Clusia fluminensis extracts and their isolated compounds against Dysdercus peruvianus and Oncopeltus fasciatus

ABSTRACT The effects of the hexanic extracts of the fruits and flowers of Clusia fluminensis Planch. & Triana, Clusiaceae, as well as their main constituents, the triterpene lanosterol and the benzophenone clusianone, were evaluated on hemipterans Dysdercus peruvianus and Oncopeltus fasciatus. The topical treatments of insects with the hexanic extracts significantly affected the survival of O. fasciatus, but not that of D. peruvianus. Concomitantly, extracts delayed the development of both hemipterans. Moreover, isolated lanosterol significantly reduced both the survival and development of O. fasciatus and D. peruvianus, while clusianone only reduce the survival of D. peruvianus and marginally inhibited the development of both insects. The results show the specific activity of lanosterol and clusianone against the two evaluated insect species and indicate the potential of compounds derived from C. fluminensis for the development of specific biopesticides for the control of agricultural pests. Subsequent work will examine the mode of action of lanosterol and clusianone isolates from C. fluminensis.

Triflumuron Effects on the Physiology and Reproduction of Rhodnius prolixus Adult Females.

We evaluated the efficacy of the growth regulator triflumuron (TFM) in inducing mortality and disrupting both oviposition and egg hatching in Rhodnius prolixus adult females. TFM was administered via feeding, topically or by continuous contact with impregnated surfaces. Feeding resulted in mild biological effects compared with topical and impregnated surfaces. One day after treatment, the highest mortality levels were observed with topical surface and 30 days later both topical and impregnated surfaces induced higher mortalities than feeding. Oral treatment inhibited oviposition even at lower doses, and hatching of eggs deposited by treated females was similarly affected by the three delivery modes. Topical treatment of eggs deposited by nontreated females significantly reduced hatching. However, treatment per contact of eggs oviposited by untreated females did not disrupt eclosion. Additionally, oral treatment increased the number of immature oocytes per female, and topical treatment reduced the mean size of oocytes. TFM also affected carcass chitin content, diuresis, and innate immunity of treated insects. These results suggest that TFM acts as a potent growth inhibitor of R. prolixus adult females and has the potential to be used in integrated vector control programs against hematophagous triatomine species.

Humoral and cellular immune responses induced by the urease-derived peptide Jaburetox in the model organism Rhodnius prolixus.

BACKGROUND: Although the entomotoxicity of plant ureases has been reported almost 20 years ago, their insecticidal mechanism of action is still not well understood. Jaburetox is a recombinant peptide derived from one of the isoforms of Canavalia ensiformis (Jack Bean) urease that presents biotechnological interest since it is toxic to insects of different orders. Previous studies of our group using the Chagas disease vector and model insect Rhodnius prolixus showed that the treatment with Jack Bean Urease (JBU) led to hemocyte aggregation and hemolymph darkening, among other effects. In this work, we employed cell biology and biochemical approaches to investigate whether Jaburetox would induce not only cellular but also humoral immune responses in this species. RESULTS: The findings indicated that nanomolar doses of Jaburetox triggered cation-dependent, in vitro aggregation of hemocytes of fifth-instar nymphs and adults. The use of specific eicosanoid synthesis inhibitors revealed that the cellular immune response required cyclooxygenase products since indomethacin prevented the Jaburetox-dependent aggregation whereas baicalein and esculetin (inhibitors of the lipoxygenases pathway) did not. Cultured hemocytes incubated with Jaburetox for 24 h showed cytoskeleton disorganization, chromatin condensation and were positive for activated caspase 3, an apoptosis marker, although their phagocytic activity remained unchanged. Finally, in vivo treatments by injection of Jaburetox induced both a cellular response, as observed by hemocyte aggregation, and a humoral response, as seen by the increase of spontaneous phenoloxidase activity, a key enzyme involved in melanization and defense. On the other hand, the humoral response elicited by Jaburetox injections did not lead to an increment of antibacterial or lysozyme activities. Jaburetox injections also impaired the clearance of the pathogenic bacteria Staphylococcus aureus from the hemolymph leading to increased mortality, indicating a possible immunosuppression induced by treatment with the peptide. CONCLUSIONS: In our experimental conditions and as part of its toxic action, Jaburetox activates some responses of the immune system of R. prolixus both in vivo and in vitro, although this induction does not protect the insects against posterior bacterial infections. Taken together, these findings contribute to the general knowledge of insect immunity and shed light on Jaburetox's mechanism of action.

Biocontrol evaluation of extracts and a major component, clusianone, from Clusia fluminensisPlanch. & Triana againstAedes aegypti

Studies evaluated the effects of hexanic extracts from the fruits and flowers ofClusia fluminensis and the main component of the flower extract, a purified benzophenone (clusianone), against Aedes aegypti. The treatment of larvae with the crude fruit or flower extracts from C. fluminensis did not affect the survival ofAe. aegypti (50 mg/L), however, the flower extracts significantly delayed development of Ae. aegypti. In contrast, the clusianone (50 mg/L) isolate from the flower extract, representing 54.85% of this sample composition, showed a highly significant inhibition of survival, killing 93.3% of the larvae and completely blocking development of Ae. aegypti. The results showed, for the first time, high activity of clusianone against Ae. aegypti that both killed and inhibited mosquito development. Therefore, clusianone has potential for development as a biopesticide for controlling insect vectors of tropical diseases. Future work will elucidate the mode of action of clusianone isolated from C. fluminensis.

Biocontrol evaluation of extracts and a major component, clusianone, from Clusia fluminensis Planch. & Triana against Aedes aegypti.

Studies evaluated the effects of hexanic extracts from the fruits and flowers of Clusia fluminensis and the main component of the flower extract, a purified benzophenone (clusianone), against Aedes aegypti. The treatment of larvae with the crude fruit or flower extracts from C. fluminensis did not affect the survival ofAe. aegypti (50 mg/L), however, the flower extracts significantly delayed development of Ae. aegypti. In contrast, the clusianone (50 mg/L) isolate from the flower extract, representing 54.85% of this sample composition, showed a highly significant inhibition of survival, killing 93.3% of the larvae and completely blocking development of Ae. aegypti. The results showed, for the first time, high activity of clusianone against Ae. aegypti that both killed and inhibited mosquito development. Therefore, clusianone has potential for development as a biopesticide for controlling insect vectors of tropical diseases. Future work will elucidate the mode of action of clusianone isolated from C. fluminensis.

Effects of essential oil from leaves of Eugenia sulcata on the development of agricultural pest insects

Essential oils are known for their insect control potential, which is mainly attributed to the presence of terpenes that interfere with hormonal and physiological processes of arthropods. The aim of the present study was to evaluate the effects of essential oil from the leaves of Eugenia sulcata Spring ex Mart., Myrtaceae, on the development of two species of agricultural pest insects, Dysdercus peruvianus and Oncopeltus fasciatus. Results showed that the essential oil induced mortality, and reduced numbers of adults. Topical treatment of Oncopeltus fasciatus using pure essential oil caused significant mortality rates (96.67%), while Dysdercus peruvianus had a higher tolerance, with 80% mortality at the end of the experiments. Results suggest that essential oil from the leaves of Eugenia sulcata may be used in agriculture for insect pest control.

Development of an insecticidal nanoemulsion with Manilkara subsericea (Sapotaceae) extract.

BACKGROUND: Plants have been recognized as a good source of insecticidal agents, since they are able to produce their own defensives to insect attack. Moreover, there is a growing concern worldwide to develop pesticides with low impact to environment and non-target organisms. Hexane-soluble fraction from ethanolic crude extract from fruits of Manilkara subsericea and its triterpenes were considered active against a cotton pest (Dysdercus peruvianus). Several natural products with insecticidal activity have poor water solubility, including triterpenes, and nanotechnology has emerged as a good alternative to solve this main problem. On this context, the aim of the present study was to develop an insecticidal nanoemulsion containing apolar fraction from fruits of Manilkara subsericea. RESULTS: It was obtained a formulation constituted by 5% of oil (octyldodecyl myristate), 5% of surfactants (sorbitan monooleate/polysorbate 80), 5% of apolar fraction from M. subsericea and 85% of water. Analysis of mean droplet diameter (155.2 ± 3.8 nm) confirmed this formulation as a nanoemulsion. It was able to induce mortality in D. peruvianus. It was observed no effect against acetylcholinesterase or mortality in mice induced by the formulation, suggesting the safety of this nanoemulsion for non-target organisms. CONCLUSIONS: The present study suggests that the obtained O/A nanoemulsion may be useful to enhance water solubility of poor water soluble natural products with insecticidal activity, including the hexane-soluble fraction from ethanolic crude extract from fruits of Manilkara subsericea.

Laboratory evaluation of the effects of essential oil of Myrciaria floribunda leaves on the development of Dysdercus peruvianus and Oncopeltus fasciatus

Myrciaria floribunda (H. West ex Willd.) O. Berg, Myrtaceae, is popularly known as "camboim-amarelo" and was collected at Restinga de Jurubatiba (RJ, Brazil). Leaves from this species were submitted to hydrodistillation to extract its essential oil. Monoterpenes were the main compounds found (53.9%), and 1,8-cineole was the major constituent (38.4%). Studies were carried out to evaluate the effects of this essential oil on the development of two species of agricultural pests (Oncopeltus fasciatus and Dysdercus peruvianus). The essential oil was considered effective against D. peruvianus and O. fasciatus, causing mortality in both insects. The LD50 values (µg/insect) observed were 112.44 µg/insect (O. fasciatus) and 309.64 µg/insect (D. peruvianus) after one day of treatment, and 72.18 µg/insect (O. fasciatus) and 94.42 µg/insect (D. peruvianus) after 22 days of treatment. The present study reports for the first time the bioinsecticidal activity of essential oil of Myrciaria floribunda leaves, and provides important data regarding the use of essential oils in complementary programs for pest control.

Isolation and molecular characterization of a major hemolymph serpin from the triatomine, Panstrongylus megistus.

BACKGROUND: Chagas disease kills 2.5 thousand people per year of 15 million persons infected in Latin America. The disease is caused by the protozoan, Trypanosome cruzi, and vectored by triatomine insects, including Panstrongylus megistus, an important vector in Brazil. Medicines treating Chagas disease have unpleasant side effects and may be ineffective, therefore, alternative control techniques are required. Knowledge of the T. cruzi interactions with the triatomine host needs extending and new targets/strategies for control identified. Serine and cysteine peptidases play vital roles in protozoan life cycles including invasion and entry of T. cruzi into host cells. Peptidase inhibitors are, therefore, promising targets for disease control. METHODS: SDS PAGE and chromatograpy detected and isolated a P. megistus serpin which was peptide sequenced by mass spectrometry. A full amino acid sequence was obtained from the cDNA and compared with other insect serpins. Reverse transcription PCR analysis measured serpin transcripts of P. megistus tissues with and without T. cruzi infection. Serpin homology modeling used the Swiss Model and Swiss-PDB viewer programmes. RESULTS: The P. megistus serpin (PMSRP1) has a ca. 40 kDa molecular mass with 404 amino acid residues. A reactive site loop contains a highly conserved hinge region but, based on sequence alignment, the normal cleavage site for serine proteases at P1-P1' was translocated to the putative position P4'-P5'. A small peptide obtained corresponded to the C-terminal 40 amino acid region. The secondary structure of PMSRP1 indicated nine α-helices and three ß-sheets, similar to other serpins. PMSRP1 transcripts occurred in all tested tissues but were highest in the fat body and hemocytes. Levels of mRNA encoding PMSRP1 were significantly modulated in the hemocytes and stomach by T. cruzi infection indicating a role for PMSRP1 in the parasite interactions with P. megistus. CONCLUSIONS: For the first time, a constitutively expressed serpin has been characterized from the hemolymph of a triatomine. This opens up new research avenues into the roles of serine peptidases in the T. cruzi/P. megistus association. Initial experiments indicate a role for PMSRP1 in T. cruzi interactions with P. megistus and will lead to further functional studies of this molecule.

Laboratory evaluation of the effects of Manilkara subsericea (Mart.) Dubard extracts and triterpenes on the development of Dysdercus peruvianus and Oncopeltus fasciatus.

BACKGROUND: Studies were carried out to evaluate the effects of Manilkara subsericea extracts and triterpenes on the development of two species of agricultural pest insects, Oncopelus fasciatus and Dysdercus peruvianus. RESULTS: All treatments of insects with M. subsericea extracts induced mortality, delayed development and inhibited moulting. Some extracts assayed (FH, FB and FD in D. peruvianus, and FH, FB and FEA in O. fasciatus) also produced body deformities in the few adults that emerged. Other extracts (FH, FEA, FB, FD and LET in both insects), however, induced either permanent (overaged) or extranumerary nymphs, both of which were unable to achieve the adult stage and reproductive status. The insects were also treated with triterpenes (α- and ß-amyrin acetates) which showed high lethality at 30 days after treatment and delayed the intermoult period so that overaged nymphs were detected. CONCLUSION: The results indicate that extracts and triterpenes from Manilkara subsericea act as potent growth inhibitors of phytophagous hemipteran nymphs. It is also concluded that the mixture of several different molecules in the extracts used produces synergic effects that do not occur after using the triterpenes (PFT) alone. These secondary metabolites in the M. subsericea extracts can potentially be used in integrated control programmes against crop pests.

Studying nanotoxic effects of CdTe quantum dots in Trypanosoma cruzi.

Semiconductor nanoparticles, such as quantum dots (QDs), were used to carry out experiments in vivo and ex vivo with Trypanosoma cruzi. However, questions have been raised regarding the nanotoxicity of QDs in living cells, microorganisms, tissues and whole animals. The objective of this paper was to conduct a QD nanotoxicity study on living T. cruzi protozoa using analytical methods. This was accomplished using in vitro experiments to test the interference of the QDs on parasite development, morphology and viability. Our results show that after 72 h, a 200 µM cadmium telluride (CdTe) QD solution induced important morphological alterations in T. cruzi, such as DNA damage, plasma membrane blebbing and mitochondrial swelling. Flow cytometry assays showed no damage to the plasma membrane when incubated with 200 µM CdTe QDs for up to 72 h (propidium iodide cells), giving no evidence of classical necrosis. Parasites incubated with 2 µM CdTe QDs still proliferated after seven days. In summary, a low concentration of CdTe QDs (2 µM) is optimal for bioimaging, whereas a high concentration (200 µM CdTe) could be toxic to cells. Taken together, our data indicate that 2 µM QD can be used for the successful long-term study of the parasite-vector interaction in real time.

Studying nanotoxic effects of CdTe quantum dots in Trypanosoma cruzi

Semiconductor nanoparticles, such as quantum dots (QDs), were used to carry out experiments in vivo and ex vivo with Trypanosoma cruzi. However, questions have been raised regarding the nanotoxicity of QDs in living cells, microorganisms, tissues and whole animals. The objective of this paper was to conduct a QD nanotoxicity study on living T. cruzi protozoa using analytical methods. This was accomplished using in vitro experiments to test the interference of the QDs on parasite development, morphology and viability. Our results show that after 72 h, a 200 μM cadmium telluride (CdTe) QD solution induced important morphological alterations in T. cruzi, such as DNA damage, plasma membrane blebbing and mitochondrial swelling. Flow cytometry assays showed no damage to the plasma membrane when incubated with 200 μM CdTe QDs for up to 72 h (propidium iodide cells), giving no evidence of classical necrosis. Parasites incubated with 2 μM CdTe QDs still proliferated after seven days. In summary, a low concentration of CdTe QDs (2 μM) is optimal for bioimaging, whereas a high concentration (200 μM CdTe) could be toxic to cells. Taken together, our data indicate that 2 μM QD can be used for the successful long-term study of the parasite-vector interaction in real time.