Do natural catastrophic events and exceptional climatic conditions also affect parasites?

Parasites and parasitologists have always lived together in good and bad luck in a sort of forced marriage. In recent times bad luck certainly prevailed, because of increasing man-made emergencies such as wars, chemical disasters, but also because of natural disasters, amplified by climate change, that condition more and more parasite–host equilibrium. The symposium at the National Congress of the Italian Society for Parasitology, was a first occasion for Italian parasitologists to reason about ‘disaster parasitology’ and researchers’ responsibilities. Extreme weather events and their impacts on parasites’ epidemiology are illustrated, comparing disasters that recently occurred in Italy with literature data. In particular, the Sardinian Island was hit subsequently by fires and floods exacerbating the effects on ecosystems and parasite–host-relationships. Examples of Cryptosporidium outbreaks in man and Fasciola hepatica infections in various hosts after heavy rains are reviewed and effects of droughts on pasture borne parasites, such as gastro-intestinal nematodes of ruminants are discussed. Heavy rains may also cause dissemination of toxic substances released accidentally from chemical plants as happened e.g. in Milan province (IT) after the dioxin hazard. The overlapping effects of strictly man-made disasters with climate change dependent extreme weather events is further challenging the understanding of what are the consequences of disasters on ecosystems and parasite epidemiology.GIS applications combined with AI programs may help to face the complex challenges, allowing the collection and analysis of spatial/temporal data at whatever level desired. Examples illustrated in the article suggest their employment also in a more systematic, prevention-oriented manner.

Synthesis and biological evaluation of benzhydryl-based antiplasmodial agents possessing Plasmodium falciparum chloroquine resistance transporter (PfCRT) inhibitory activity

Due to the surge in resistance to common therapies, malaria remains a significant concern to human health worldwide. In chloroquine (CQ)-resistant (CQ-R) strains of Plasmodium falciparum, CQ and related drugs are effluxed from the parasite's digestive vacuole (DV). This process is mediated by mutant isoforms of a protein called CQ resistance transporter (PfCRT). CQ-R strains can be partially re-sensitized to CQ by verapamil (VP), primaquine (PQ) and other compounds, and this has been shown to be due to the ability of these molecules to inhibit drug transport via PfCRT. We have previously developed a series of clotrimazole (CLT)-based antimalarial agents that possess inhibitory activity against PfCRT (4a,b). In our endeavor to develop novel PfCRT inhibitors, and to perform a structure-activity relationship analysis, we synthesized a new library of analogues. When the benzhydryl system was linked to a 4-aminoquinoline group (5a-f) the resulting compounds exhibited good cytotoxicity against both CQ-R and CQ-S strains of P. falciparum. The most potent inhibitory activity against the PfCRT-mediated transport of CQ was obtained with compound 5k. When compared to the reference compound, benzhydryl analogues of PQ (5i,j) showed a similar activity against blood-stage parasites, and a stronger in vitro potency against liver-stage parasites. Unfortunately, in the in vivo transmission blocking assays, 5i,j were inactive against gametocytes.

Plasmodium stage-selective antimalarials from Lophira lanceolata stem bark

Targeting the transmissible stages of the Plasmodium parasite that develop in the human and mosquito host is a crucial strategy for malaria control and elimination. Medicinal plants offer a prolific source for the discovery of new antimalarial compounds. The recent identification of the gametocytocidal activity of lophirone E, obtained from the African plant Lophira lanceolata (Ochnaceae), inspired the evaluation of the plant also against early sporogonic stages of the parasite development. The bioassay-guided phytochemical study led to the isolation of two known lanceolins and of a new glycosylated bichalcone, named glucolophirone C. Its stereostructure, including absolute configuration of the bichalcone moiety, was elucidated by means of NMR, HRMS, ECD and computational calculations. Lanceolin B proved to be a potent inhibitor of the development of Plasmodium early sporogonic stages indicating that the plant produces two different stage-specific antimalarial agents acting on transmissible stages in the human and mosquito host.

In vitro Multistage Malaria Transmission Blocking Activity of Selected Malaria Box Compounds

Purpose

Continuous efforts into the discovery and development of new antimalarials are required to face the emerging resistance of the parasite to available treatments. Thus, new effective drugs, ideally able to inhibit the Plasmodium life-cycle stages that cause the disease as well as those responsible for its transmission, are needed. Eight compounds from the Medicines for Malaria Venture (MMV) Malaria Box, potentially interfering with the parasite polyamine biosynthesis were selected and assessed in vitro for activity against malaria transmissible stages, namely mature gametocytes and early sporogonic stages.

Methods

Compound activity against asexual blood stages of chloroquine-sensitive 3D7 and chloroquine-resistant W2 strains of Plasmodium falciparum was tested measuring the parasite lactate dehydrogenase activity. The gametocytocidal effect was determined against the P. falciparum 3D7elo1-pfs16-CBG99 strain with a luminescent method. The murine P. berghei CTRP.GFP strain was employed to assess compounds activities against early sporogonic stage development in an in vitro assay simulating mosquito midgut conditions.

Results

Among the eight tested molecules, MMV000642, MMV000662 and MMV006429, containing a 1,2,3,4-tetrahydroisoquinoline-4-carboxamide chemical skeleton substituted at N-2, C-3 and C-4, displayed multi-stage activity. Activity against asexual blood stages of both strains was confirmed with values of IC₅₀ (50% inhibitory concentration) in the range of 0.07–0.13 µM. They were also active against mature stage V gametocytes with IC₅₀ values below 5 µM (range: 3.43–4.42 µM). These molecules exhibited moderate effects on early sporogonic stage development, displaying IC₅₀ values between 20 and 40 µM.

Conclusion

Given the multi-stage, transmission-blocking profiles of MMV000642, MMV000662, MMV006429, and their chemical characteristics, these compounds can be considered worthy for further optimisation toward a TCP5 or TCP6 target product profile proposed by MMV for transmission-blocking antimalarials.

A murine malaria protocol for characterizing transmission blocking benefits of antimalarial drug combinations

BACKGROUND

Current efforts towards malaria elimination include the discovery of new transmission blocking (TB) drugs and identification of compounds suitable to replace primaquine, recommended as transmission blocking post treatment after artemisinin combination therapy (ACT). High through put screening of compound libraries has allowed to identify numerous compounds active in vitro against gametocytes and insect early sporogonic stages, but few studies have been performed to characterize TB compounds in vivo. Here we propose a double TB drug Direct Feeding Assay (2TB-DFA), suitable to assess the combined effects of TB compounds.

MATERIALS AND METHODS

Plasmodium berghei GFPcon (PbGFPcon), BALB/c mice and Anopheles stephensi mosquitoes were used. Artemisinin (ART) and artesunate (AS) served as examples of artemisinins, NeemAzal® (NA), as a known TB-product with sporontocidal activity. DFA experiments were performed to assess the appropriate time point of administration before mosquito feeding and estimate suitable sub-optimal doses of the three compounds that allow combination effects to be appreciated.

RESULTS

Suboptimal dosages, that reduce about 50% of oocyst development, were recorded with ART in the range of 16-30 mg/ kg, AS 14-28 mg/kg and NA 31-38mg/kg. Ten hours before mosquito feeding (corresponding to 3.5 days after mouse infection) was determined as a suitable time point for mouse treatment with ART and AS and 1 hour for post-treatment with NA. ART given at 35 mg/kg in combination with NA at 40 mg/kg reduced oocyst density by 94% and prevalence of infection by 59%. Similarly, the combination of ART at 25 mg/kg plus NA at 35 mg/kg decreased oocyst density by 95% and prevalence of infection by 34%. In the 2TB-DFA, conducted with AS (20 mg/kg) and NA (35 mg/kg) the combination treatment reduced oocyst density by 71% and did not affect prevalence of infection. Applying 'Highest Single Agent' analysis and considering as readout oocyst density and prevalence of infection, cooperative effects of the combination treatments, compared with the single compound treatments emerged.

CONCLUSION

This study suggests the 2TB-DFA to be suitable for the profiling of new TB candidates that could substitute primaquine as a post-treatment to ACT courses.

A formative study of disposal and re-use of old mosquito nets by communities in Malindi, Kenya

BACKGROUND

About 30 million insecticide treated mosquito nets have been distributed in Kenya since 2001 and ownership is approaching full coverage. As a consequence of this achievement, Kenya is faced with the challenge of disposing old mosquito nets that are no longer in use. The study aimed at investigating ways of disposal and re-use of old and torn nets by end users.

MATERIALS AND METHODS

A formative study was conducted in the former Malindi District, which is comprised of Malindi and Magarini sub-counties of Kilifi County in Coastal Kenya. A total of 6 Focus Group Discussions, 10 Key Informant Interviews and 9 transect walks/drives were undertaken. Data from the different sources were analysed separately and triangulated for similarities and differences.

RESULTS

There were variations in disposal and re-use of old nets between urban and rural or peri-urban residents. In all settings, people adopted innovative and beneficial ways of re-using old, expired nets, and those that were damaged beyond repair. Common causes of damage were fire, children, domestic animals sharing the sleeping room and friction from the bed poles while hanging or tacking it in under a sleeping mat. Re-use was most prominent in farming activities (78%) and less to for use in mosquito control, like window screening (15%). The remaining 8% was related to making ropes, swings, footballs, goal posts and fishing nets. Advantageous texture and nature of the netting material, perceived economic benefit and lack of guidelines for disposal were the main reasons cited by residents for re-using old nets.

CONCLUSIONS

It is important that re-use and disposal of old mosquito nets is distinguished from misuse of newly distributed mosquito nets. Alternative uses of old nets as opposed to misuse of new nets was found to be common in our study.

Exploring communities' and health workers' perceptions of indicators and drivers of malaria decline in Malindi, Kenya

BACKGROUND

Since 2000, a decrease in malaria burden has been observed in most endemic countries. Declining infection rates and disease burden and reduction in asymptomatic carriers are the outcome of improved quality of care and related health system factors. These include improved case management through better diagnosis, implementation of highly effective antimalarial drugs and increased use of bednets. We studied communities' and health workers' perceptions of indicators and drivers in the context of decreasing malaria transmission in Malindi, Kenya.

MATERIALS AND METHODS

A variety of qualitative methods that included participatory rural appraisal (PRA) tools such as community river of life and trend lines, focus group discussions (FGDs) and key informant interviews were used. Studies took place between November 2013 and April 2014.

RESULTS

Providing residents with bednets contributed to malaria reduction, and increasing community awareness on the causes and symptoms of malaria and improved malaria treatment were also perceived to contribute to the decline of malaria. The study identified three perceived drivers to the reported decline in malaria: a) community health workers' enhanced awareness creation towards household owners regarding malaria-related activities through visitations and awareness sessions, b) Women involvement in Savings Internal Lending Community was perceived to have increased their financial base, thereby improving their decision-making power towards the care of their sick child(ren), c) Non Governmental Organizations (NGOs) and partners played a promoter part in health and general economic development initiatives.

CONCLUSIONS

To achieve the goal of malaria elimination, collaboration between governmental and NGOs will be crucial when improving the financial base of women and enhancing participation of community health workers.

Daucovirgolides I-L, four congeners of the antimalarial daucovirgolide G from Daucus virgatus

Repeated chromatographic purifications of aerial parts of the Tunisian plant Daucus virgatus led to the isolation of four new germacranolides, named daucovirgolides I-L (2-5), along with the Plasmodium transmission-blocking agent daucovirgolide G. The chemical structures of the new compounds were defined as mono- or di-angeloylated germacrane-type sesquiterpenoids by spectroscopic (mainly 1D and 2D NMR) and spectrometric methods (ESIMS). The low potency exhibited by daucovirgolides I-L further supports the observation that strict structural requirements do exist for the Plasmodium transmission blocking activity in the daucovirgolide series. In particular, the endocyclic double bond system seems to be crucial for bioactivity.

Effects of Azadirachta indica seed kernel extracts on early erythrocytic schizogony of Plasmodium berghei and pro-inflammatory response in inbred mice

Background

Medicinal plant research may contribute to develop new pharmacological control tools for vector borne diseases, such as malaria.

Methods

The effects of methanol extracts (ME) obtained from seed kernel of ripe and unripe Azadirachta indica fruits were studied on erythrocytic proliferation of the rodent malaria parasite Plasmodium berghei strain ANKA and on mice pro-inflammatory response, as evaluated by measuring the matrix-metalloproteinase-9 (MMP-9) and tumour necrosis factor (TNF) plasma levels, in two mouse strains (C57BL/6 and BALB/c) which are considered as prototypical of Th1 and Th2 immune response, respectively.

Results

ME obtained from seed kernel of unripe Azadirachta indica fruits decreased by about 30% the proportion of erythrocytes infected with the malaria parasite in C57BL/6 mice in the 4 days suppressive test. In this treatment group, MMP-9 and TNF levels were notably higher than those measured in the same mouse strain treated with the anti-malarial drug artesunate, Azadirachta indica kernel extracts from ripe fruits or solvent. In BALB/c mice, treatment with kernel extracts did not influence parasitaemia. MMP-9 and TNF levels measured in this mouse strain were notably lower than those recorded in C57BL/6 mice and did not vary among treatment groups.

Conclusions

The effects of the ME on the parasite-host interactions appeared to be mouse strain-dependent, but also related to the ripening stage of the neem fruits, as only the unripe fruit seed kernel extracts displayed appreciable bioactivity.

Electronic supplementary material

The online version of this article (10.1186/s12936-019-2671-8) contains supplementary material, which is available to authorized users.

Adenosine Triphosphate-Binding Cassette Transporters Are Not Involved In the Detoxification of Azadirachta indica Extracts In Anopheles stephensi Larvae

Detoxifying pathways of mosquitoes against the neem (Azadirachta indica) extracts are still unclear. The aim of the present study was to investigate the role of adenosine triphosphate-binding cassette (ABC) transporters in this process in Anopheles stephensi, one of the main malaria vectors in southern Asia. Third-stage larvae of An. stephensi were fed with fish food alone or in combination with neem extract at 0.5%, 1%, 5%, and 10%. Six ABC-transporter genes from 3 different subfamilies (B, C, and G) were analyzed to assess their relative expression compared with controls. A bioassay was also performed to assess larval mortality rate at different concentrations and in combination with verapamil, an ABC-transporter inhibitor. No significant variation in the expression levels of any transporter belonging to the B, C, and G subfamilies was detected. Furthermore, the use of verapamil did not induce an increase in mortality at any of the tested neem extract concentrations, indicating that ABC transporters are not involved in the detoxification of neem extracts in An. stephensi larvae.

Angeloylated Germacranolides from Daucus virgatus and Their Plasmodium Transmission Blocking Activity

Phytochemical investigation of the aerial parts of the Tunisian plant Daucus virgatus led to the isolation of eight new germacranolides named daucovirgolides A-H (1-8). The stereostructures of these sesquiterpene lactones, decorated by either one or two angeloyl groups, have been determined by a combination of MS, NMR spectroscopy, chemical derivatization, and comparison of experimental electronic circular dichroism curves with TDDFT-predicted data. Daucovirgolide G (7) proved to be the single member of this family to possess a marked inhibitory activity (92% at 50 μg/mL) on the development of Plasmodium early sporogonic stages, the nonpathogenic transmissible stages of malaria parasites, devoid of general cytotoxicity. The selective activity of daucovirgolide G points to the existence of strict structural requirements for this transmission-blocking activity and therefore of a well-defined, although yet unidentified, biological target.

In vitro and ex vivo activity of an Azadirachta indica A.Juss. seed kernel extract on early sporogonic development of Plasmodium in comparison with azadirachtin A, its most abundant constituent

BACKGROUND

NeemAzal^® (NA) is a quantified extract from seed kernels of neem, Azadirachta indica A.Juss. (Meliaceae), with a wide spectrum of biological properties, classically ascribed to its limonoid content. NA contains several azadirachtins (A to L), azadirachtin A (AzaA) being its main constituent. AzaA has been shown to inhibit microgamete formation of the rodent malaria parasite Plasmodium berghei, and NA was found to completely inhibit the transmission of Plasmodium berghei to Anopheles stephensi mosquitoes when administered to gametocytemic mice at a corresponding AzaA dose of 50mg/kg before exposure to mosquitoes.

PURPOSE

The present study was aimed at i) assessing the pharmacodynamics and duration of action of NA and AzaA against P. berghei exflagellation in systemic circulation in mice and ii) elucidating the transmission blocking activity (TBA) of the main NA constituents.

STUDY DESIGN

The NA and AzaA pharmacodynamics on exflagellation were assessed through ex vivo exflagellation assays, while TBA of NA constituents was evaluated through in vitro ookinete development assay.

METHODS

Pharmacodynamics experiments: Peripheral blood from P. berghei infected BALB/c mice with circulating mature gametocytes, were treated i.p. with 50mg/kg and 100mg/kg pure AzaA and with NeemAzal^® (Trifolio-M GmbH) at the corresponding AzaA concentrations. The effect magnitude and duration of action of compounds was estimated by counting exflagellation centers, formed by microgametocytes in process of releasing flagellated gametes, at various time points after treatment in ex vivo exflagellation tests. Ookinete Development Assay: The direct effects of NeemAzal^® and AzaA on ookinete development were measured by fluorescence microscopy after incubation of gametocytemic blood with various concentrations of test substances in microplates for 24h.

RESULTS

The exflagellation tests revealed an half-life of NA anti-plasmodial compounds of up to 7h at a NA dose corresponding to 100mg/kg equivalent dose of AzaA. The ookinete development assay showed an increased activity of NA against early sporogonic stages compared to that of AzaA. The IC₅₀ value determined for NA was 6.8µg/ml (CI₉₅: 5.95-7.86), about half of the AzaA IC₅₀ (12.4µg/ml; CI₉₅: 11.0-14.04).

CONCLUSION

The stronger activity of NA, when compared to AzaA, could not be explained by an additive or synergistic effect by other azadirachtins (B, D and I) present in NA. In fact, the addition of these compounds at 50µM concentration to AzaA did not evidence any decrease of the IC₅₀ against early sporogonic stages to that obtained with AzaA alone. It is likely that other non-limonoid compounds present in NA may contribute to AzaA activity and enhanced pharmacodynamics against exflagellation both in vitro and in vivo.

Novel metalloantimalarials: Transmission blocking effects of water soluble Cu(I), Ag(I) and Au(I) phosphane complexes on the murine malaria parasite Plasmodium berghei

The water soluble phosphane complexes [M(L)₄]PF₆ (M=Cu(I), Ag(I)) and [Au(L)₄]Cl (L=thp (tris(hydroxymethyl)phosphane) or PTA (1,3,5-triaza-7-phosphaadamantane)) showed notable in vitro activity against Plasmodium early sporogonic stages, the sexual forms of the malaria parasite that are responsible for infection of the mosquito vector. Effects varied according to both, the type of metal and phosphane ligands. [Ag(thp)₄]PF₆ was the best performing complex exhibiting a half inhibitory concentration (IC₅₀) value in the low micromolar range (0.3-15.6μM). The silver complex [Ag(thp)₄]PF₆ was characterized by X-ray crystallography revealing that the structure comprises the cationic complex [Ag(thp)₄]⁺, the PF₆^- anion, and a water molecule of crystallization. Our results revealed that Cu(I), Ag(I) and Au(I) phosphanes complexes elicited similar activity profiles showing potential for the development of antimalarial, transmission blocking compounds. Molecules targeting the sexual parasite stages in the human and/or mosquito host are urgently needed to complement current artemisinin based treatments and next generation antimalarials in a vision not only to cure the disease but to interrupt its transmission.

Transmission blocking effects of neem (Azadirachta indica) seed kernel limonoids on Plasmodium berghei early sporogonic development

Azadirachta indica, known as neem tree and traditionally called "nature's drug store" makes part of several African pharmacopeias and is widely used for the preparation of homemade remedies and commercial preparations against various illnesses, including malaria. Employing a bio-guided fractionation approach, molecules obtained from A. indica ripe and green fruit kernels were tested for activity against early sporogonic stages of Plasmodium berghei, the parasite stages that develop in the mosquito mid gut after an infective blood meal. The limonoid deacetylnimbin (3) was identified as one the most active compounds of the extract, with a considerably higher activity compared to that of the close analogue nimbin (2). Pure deacetylnimbin (3) appeared to interfere with transmissible Plasmodium stages at a similar potency as azadirachtin A. Considering its higher thermal and chemical stability, deacetylnimbin could represent a suitable alternative to azadirachtin A for the preparation of transmission blocking antimalarials.

Neemazal ® as a possible alternative control tool for malaria and African trypanosomiasis?

BACKGROUND

Research efforts to identify possible alternative control tools for malaria and African trypanosomiasis are needed. One promising approach relies on the use of traditional plant remedies with insecticidal activities.

METHODS

In this study, we assessed the effect of blood treated with different doses of NeemAzal ® (NA, neem seed extract) on mosquitoes (Anopheles coluzzii) and tsetse flies (Glossina palpalis gambiensis) (i) avidity to feed on the treated blood, (ii) longevity, and (iii) behavioural responses to human and calf odours in dual-choice tests. We also gauged NeemAzal ® toxicity in mice.

RESULTS

In An. coluzzii, the ingestion of NA in bloodmeals offered by membrane feeding resulted in (i) primary antifeedancy; (ii) decreased longevity; and (iii) reduced response to host odours. In G. palpalis gambiensis, NA caused (i) a knock-down effect; (ii) decreased or increased longevity depending on the dose; and (iii) reduced response to host stimuli. In both cases, NA did not affect the anthropophilic rate of activated insects. Overall, the most significant effects were observed with NA treated bloodmeals at a dose of 2000 μg/ml for mosquitoes and 50 μg/ml for tsetse flies. Although no mortality in mice was observed after 14 days of follow-up at oral doses of 3.8, 5.6, 8.4 and 12.7 g/kg, behavioural alterations were noticed at doses above 8 g/kg.

CONCLUSION

This study revealed promising activity of NA on A. coluzzii and G. palpalis gambiensis but additional research is needed to assess field efficacy of neem products to be possibly integrated in vector control programmes.

Plasmodium transmission blocking activities of Vernonia amygdalina extracts and isolated compounds

Background

Medicinal plants are a validated source for discovery of new leads and standardized herbal medicines. The aim of this study was to assess the activity of Vernoniaamygdalina leaf extracts and isolated compounds against gametocytes and sporogonic stages of Plasmodiumberghei and to validate the findings on field isolates of Plasmodium falciparum.

Methods

Aqueous (Ver-H₂O) and ethanolic (Ver-EtOH) leaf extracts were tested in vivo for activity against sexual and asexual blood stage P. berghei parasites. In vivo transmission blocking effects of Ver-EtOH and Ver-H₂O were estimated by assessing P. berghei oocyst prevalence and density in Anopheles stephensi mosquitoes. Activity targeting early sporogonic stages (ESS), namely gametes, zygotes and ookinetes was assessed in vitro using P. berghei CTRP_p.GFP strain. Bioassay guided fractionation was performed to characterize V.amygdalina fractions and molecules for anti-ESS activity. Fractions active against ESS of the murine parasite were tested for ex vivo transmission blocking activity on P.falciparum field isolates. Cytotoxic effects of extracts and isolated compounds vernolide and vernodalol were evaluated on the human cell lines HCT116 and EA.hy926.

Results

Ver-H₂O reduced the P. berghei macrogametocyte density in mice by about 50% and Ver-EtOH reduced P. berghei oocyst prevalence and density by 27 and 90%, respectively, in An.stephensi mosquitoes. Ver-EtOH inhibited almost completely (>90%) ESS development in vitro at 50 μg/mL. At this concentration, four fractions obtained from the ethylacetate phase of the methanol extract displayed inhibitory activity >90% against ESS. Three tested fractions were also found active against field isolates of the human parasite P. falciparum, reducing oocyst prevalence in Anopheles coluzzii mosquitoes to one-half and oocyst density to one-fourth of controls. The molecules and fractions displayed considerable cytotoxicity on the two tested cell-lines.

Conclusions

Vernonia amygdalina leaves contain molecules affecting multiple stages of Plasmodium, evidencing its potential for drug discovery. Chemical modification of the identified hit molecules, in particular vernodalol, could generate a library of druggable sesquiterpene lactones. The development of a multistage phytomedicine designed as preventive treatment to complement existing malaria control tools appears a challenging but feasible goal.

Electronic supplementary material

The online version of this article (doi:10.1186/s12936-015-0812-2) contains supplementary material, which is available to authorized users.

Poly-Electrophilic Sesquiterpene Lactones from Vernonia amygdalina: New Members and Differences in Their Mechanism of Thiol Trapping and in Bioactivity

In addition to known compounds, the leaves of Vernonia amygdalina afforded the new sesquiterpene lactones 14-O-methylvernolide (2), 3'-deoxyvernodalol (6), and vernomygdalin (8). These and related compounds were evaluated for modulation of a series of thiol trapping-sensitive transcription factors (NF-κB, STAT3, and Nrf2), involved in the maintenance of the chronic inflammatory condition typical of human degenerative diseases. Vernolide (1) emerged as a potent inhibitor of STAT3 and NF-κB and showed cytostatic activity toward the prostate cancer cell line DU45, arresting the cell cycle at the S phase. The exomethylene lactones are characterized by multiple Michael acceptor sites, as exemplified by vernolide (1) and vernodalol (5). By using the nuclear magnetic resonance-based cysteamine assay, the most reactive thiophilic site could be identified in both compounds, and competitive experiments qualified vernolide (1) as being more thiophilic than vernodalol (5), in agreement with the results of the pharmacological assays.

Impact of repeated NeemAzal-treated blood meals on the fitness of Anopheles stephensi mosquitoes

BACKGROUND

Herbal remedies are widely used in many malaria endemic countries to treat patients, in particular in the absence of anti-malarial drugs and in some settings to prevent the disease. Herbal medicines may be specifically designed for prophylaxis and/or for blocking malaria transmission to benefit both, the individual consumer and the community at large. Neem represents a good candidate for this purpose due to its inhibitory effects on the parasite stages that cause the clinical manifestations of malaria and on those responsible for infection in the vector. Furthermore, neem secondary metabolites have been shown to interfere with various physiological processes in insect vectors. This study was undertaken to assess the impact of the standardised neem extract NeemAzal on the fitness of the malaria vector Anopheles stephensi following repeated exposure to the product through consecutive blood meals on treated mice.

METHODS

Batches of An. stephensi mosquitoes were offered 5 consecutive blood meals on female BALB/c mice treated with NeemAzal at an azadirachtin A concentration of 60, 105 or 150 mg/kg. The blood feeding capacity was estimated by measuring the haematin content of the rectal fluid excreted by the mosquitoes during feeding. The number of eggs laid was estimated by image analysis and their hatchability assessed by direct observations.

RESULTS

A dose and frequency dependent impact of NeemAzal treatment on the mosquito feeding capacity, oviposition and egg hatchability was demonstrated. In the 150 mg/kg treatment group, the mosquito feeding capacity was reduced by 50% already at the second blood meal and by 50 to 80% in all treatment groups at the fifth blood meal. Consequently, a 50 - 65% reduction in the number of eggs laid per female mosquito was observed after the fifth blood meal in all treatment groups. Similarly, after the fifth treated blood meal exposure, hatchability was found to be reduced by 62% and 70% in the 105 and 150 mg/kg group respectively.

CONCLUSIONS

The findings of this study, taken together with the accumulated knowledge on neem open the challenging prospects of designing neem-based formulations as multi-target phytomedicines exhibiting preventive, parasite transmission-blocking as well as anti-vectorial properties.

Synthetic spirocyclic endoperoxides: new antimalarial scaffolds

Design, synthesis and molecular docking calculation studies led to the identification of novel spirocyclic peroxides with in vitro and in vivo antimalarial activity.

Enabling factors facilitating the use of neem-based remedies for the management of malaria in the Lower Shire District of Chikwawa, Malawi

Background

Malaria remains a major public health threat in Malawi, affecting mostly children under five and pregnant women. Despite the availability of chemotherapy and chemoprophylaxis, resistance to sulfadoxine pyrimethamine and the high cost and complicated regimen of artemether-lumefantrine have accelerated the use of home-based remedies for the management of malaria in Chikwawa district, Malawi. This study aimed to determine factors that facilitate the use of herbal remedies within communities in the management of malaria in the presence of free health care services, with the intention of assessing the feasibility of developing improved herbal products as anti-malarial prophylaxis.

Materials and Methods

Data on factors driving the use of neem-based preparations commonly used in the management of malaria were collected through qualitative interviews and focus group discussions. Qualitative data were analysed drawing on the Framework Analysis approach.

Results

Neem and moringa were identified as the principal plants used for the management of malaria, with neem being the most frequently used. Factors favouring the communal use of neem-based remedies included the habit of resorting to herbal remedies as first aid treatment, lack of drugs and proper medical care in modern health facilities, and the need for preventive anti-malarial remedies during the high-transmission season. The perceived effectiveness of neem-based herbal remedies was based on their fast action against the symptoms of malaria, thereby providing immediate relief to the patient, which might explain their wide-scale use for malaria treatment.

Conclusions

Local communities prefer to use neem and/or moringa remedies for their primary healthcare needs in the management of malaria because of their ease of access, preparation and administration without frequent adverse events, as opposed to ACTs. These remedies are already being used as prophylaxis in unimproved/non-standardised formulation. This suggests that standardised herbal preparations would be culturally acceptable at community level. Evidence-based research is required to validate parasitological and clinical efficacy and determine safety of these anti-malarial herbs.

A retrospective evaluation of the quality of malaria case management at twelve health facilities in four districts in Zambia

OBJECTIVE

To establish the appropriateness of malaria case management at health facility level in four districts in Zambia.

METHODS

This study was a retrospective evaluation of the quality of malaria case management at health facilities in four districts conveniently sampled to represent both urban and rural settings in different epidemiological zones and health facility coverage. The review period was from January to December 2008. The sample included twelve lower level health facilities from four districts. The Pearson Chi-square test was used to identify characteristics which affected the quality of case management.

RESULTS

Out of 4 891 suspected malaria cases recorded at the 12 health facilities, more than 80% of the patients had a temperature taken to establish their fever status. About 67% (CI 95 66.1-68.7) were tested for parasitemia by either rapid diagnostic test or microscopy, whereas the remaining 22.5% (CI 95 21.3.1-23.7) were not subjected to any malaria test. Of the 2 247 malaria cases reported (complicated and uncomplicated), 71% were parasitologically confirmed while 29% were clinically diagnosed (unconfirmed). About 56% (CI 95 53.9-58.1) of the malaria cases reported were treated with artemether-lumefantrine (AL), 35% (CI 95 33.1-37.0) with sulphadoxine-pyrimethamine, 8% (CI 95 6.9-9.2) with quinine and 1% did not receive any anti-malarial. Approximately 30% of patients WHO were found negative for malaria parasites were still prescribed an anti-malarial, contrary to the guidelines. There were marked inter-district variations in the proportion of patients in WHOm a diagnostic tool was used, and in the choice of anti-malarials for the treatment of malaria confirmed cases. Association between health worker characteristics and quality of case malaria management showed that nurses performed better than environmental health technicians and clinical officers on the decision whether to use the rapid diagnostic test or not. Gender, in service training on malaria, years of residence in the district and length of service of the health worker at the facility were not associated with diagnostic and treatment choices.

CONCLUSIONS

Malaria case management was characterised by poor adherence to treatment guidelines. The non-adherence was mainly in terms of: inconsistent use of confirmatory tests (rapid diagnostic test or microscopy) for malaria; prescribing anti-malarials which are not recommended (e.g. sulphadoxine-pyrimethamine) and prescribing anti-malarials to cases testing negative. Innovative approaches are required to improve health worker adherence to diagnosis and treatment guidelines.

A user friendly method to assess Anopheles stephensi (Diptera: Culicidae) vector fitness: fecundity

Fecundity, bloodmeal size, and survival are among the most important parameters in the overall fitness of mosquitoes. Impact of an intervention that affects fecundity can be assessed by directly counting the eggs laid by exposed mosquitoes, which is usually done manually. We have developed a macroinstruction, which can be used to count thousands of Anopheles stephensi Liston eggs in a few minutes, to provide an alternative and adaptable method to egg counting as a measure of fecundity. The macro was developed using a scanner and a computer running AxioVision Rel. 4.8 software, a freely accessible software compatible with Windows XP/7/Vista. Using this semiautomated method, it is possible to reduce time, avoid human error and bias, and obtain improved consistency in studies measuring mosquito fecundity.

Efficacy of sunlight-activatable porphyrin formulates on larvae of Anopheles gambiae M and S molecular forms and An. arabiensis: a potential novel biolarvicide for integrated malaria vector control

Biolarvicides, such as microbial formulations based on Bacillus thuringiensis and B. sphaericus, have been found to be highly effective against mosquito larvae and are currently employed as eco-friendly alternatives to synthetic chemical insecticides for vector control. Recently, a porphyrin of natural origin has been suggested as a sunlight-activatable larvicide against the dengue vector Aedes aegypti. In order to validate the approach for the control of the malaria vector, we tested the photo-larvicidal activity of a novel porphyrin, namely meso-tri(N-methyl-pyridyl), mono(N-dodecyl-pyridyl)porphine, C12, associated with two specifically selected carriers, against Anopheles gambiae s.s. and An. arabiensis larvae, both laboratory reared and collected from malaria endemic sites in Burkina Faso. Both C12-porphyrin formulates, when administered to larvae at a 50μM porphyrin dose, were accumulated in the alimentary canal. Subsequent exposure of the porphyrin-loaded larvae to sunlight for short times (0.5-3h) led to a complete mortality. The high efficacy exhibited by a "foodstuff" porphyrin formulate also in the presence of typical larval food particles opens promising perspectives for the development of an effective photocidal larvicide.

Antimalarial plant remedies from Burkina Faso: their potential for prophylactic use

ETHNOPHARMACOLOGICAL RELEVANCE

Saye, a combination remedy prepared from Cochlospermum planchonii Hook.f. (Cochlospermaceae), Cassia alata L. (Fabaceae) and Phyllanthus amarus Schumach. et Thonn. (Euphorbiaceae), N'Dribala, a Cochlospermum planchonii root decoction, and a fruit preparation of Azadirachta indica A. Juss. (Meliaceae) are plant remedies of the folk medicine in Burkina Faso and are commonly used by traditional healers for the treatment of malaria.

AIM OF THE STUDY

This study aimed at validating the antiplasmodial activity of the preparations and at estimating their potential for prophylaxis, using the murine malaria system Plasmodium berghei/Anopheles stephensi.

MATERIALS AND METHODS

Aqueous extracts were orally administered to mice (6 animals per treatment group) at a daily dose of 200mg/kg body weight for nine days, applying protocols that mimic as much as possible traditional recipes and treatment schemes.

RESULTS

Saye, N'Dribala and Azadirachta indica preparations revealed prophylactic activity, reducing parasitaemia in treated mice, with respect to controls, by 52.0% (CI(95) 46.1-57.9), 45.5% (CI(95) 44.5-46.5) and 45.0% (CI(95) 41.1-48.9), respectively. No evidence of transmission blocking effects was detected with any of the tested remedies.

CONCLUSIONS

This study confirms, in the murine malaria system, the antiplasmodial properties of the examined remedies on the Plasmodium stages developing in the vertebrate host, thus encouraging studies aiming at identifying the active fractions and compounds responsible for the described activity and to develop standardized prophylactic remedies.

Effects of a new photoactivatable cationic porphyrin on ciliated protozoa and branchiopod crustaceans, potential components of freshwater ecosystems polluted by pathogenic agents and their vectors

The increasing use of photosensitized processes for disinfection of microbiologically polluted waters requires a precise definition of the factors controlling the degree of photosensitivity in target and non-target organisms. In this regard, tests with protozoa and invertebrates which have a natural habitat in such waters may be used as first screening methods for the assessment of possible hazards for the ecosystem. A new cationic porphyrin, namely meso-tri(N-methyl-pyridyl)mono(N-dodecyl-pyridyl)porphine (C12), is tested in this work on the protozoan Ciliophora Colpoda inflata and Tetrahymena thermophila and the Crustacea Branchiopoda Artemia franciscana and Daphnia magna. The protocol involved 1 h incubation with porphyrin doses in the 0.1-10.0 μM range and subsequent irradiation with visible light at a fluence rate of 10 mW cm(-2). The results indicate that C12 porphyrin has a significant affinity for C. inflata and T. thermophila; this is also shown by fluorescence microscopic analyses. C. inflata cysts were resistant to the phototreatment up to a porphyrin dose of 0.6 μM. The effects of C12 on cysts have been evaluated at 3 and 24 h after the end of the phototreatment; a delay in the excystment process was observed. T. thermophila was fairly resistant to the phototreatment with C12 porphyrin. The data obtained with the two crustaceans indicated that the effects of dark- and photo-treatment with C12 need to be closely examined for every organism. A. franciscana is more resistant, probably owing to its ability to adapt to extreme conditions, while the high level of photosensitivity displayed by Daphnia magna represents a potential drawback, as this organism is often selected as a reference standard for assessing the environmental safety. Thus, while C12 photosensitisation can represent a useful tool for inducing a microbicidal or larvicidal action on polluted waters, the irradiation protocols must be carefully tailored to the nature of the specific water basin, and in particular to its biotic characteristics.

Potential of a Khaya ivorensis -Alstonia boonei extract combination as antimalarial prophylactic remedy

ETHNOPHARMACOLOGICAL RELEVANCE

The decoction of the combined stem barks of Khaya ivorensis A. Chev. (Meliaceae) and Alstonia boonei De Wild (Apocynaceae) has a history of use in traditional medicine of central Cameroon for malaria treatment but also for the prevention of the disease.

AIM OF THE STUDY

The purpose of this investigation was to determine the antiplasmodial activity of Khaya ivorensis (K) and Alstonia boonei (A) preparations in the murine malaria model Plasmodium berghei/Anopheles stephensi, to estimate their prophylactic potential and to assess acute and sub-acute toxicity of the formulations prepared according to the traditional recipes.

MATERIALS AND METHODS

Aqueous extracts from the stem-bark of the two plants were prepared and tested separately and in combination. BALB/c mice were treated for 9 days and challenged on day 3 by exposure to mosquitoes infected with Plasmodium berghei. Treatment doses ranged between 200 and 400mg/kg/day, corresponding approximately to the dosage applied by traditional healers to cure malaria patients or prevent the disease. Parasitemia reduction in treated animals was calculated from Giemsa smear counts, of two replicate experiments. To estimate acute toxicity in terms of median lethal dose (LD50), geometrically increasing doses were administered to mice. Sub-acute toxicity of the herbal combination (KA) was investigated by administering the same doses as in the antiplasmodial activity test for a period of 14 days, followed by 14 days of recovery observation. Locomotor activity (Open Field Test), body weight, liver and kidney morphology were monitored.

RESULTS

The combination KA was found to exhibit antiplasmodial activity in the murine malaria model. In mice treated with the combination remedy at a dosage of 200mg/kg/day, parasitemia values of 6.2% ± 1.7 and 6.5% ± 0.8 were recorded, compared to 10.8% ± 1.3 and 12.0% ± 4.0 in controls (p<0.01). Doubling the dosage of the extracts did not significantly increase parasite suppression. When extracts of K and A were administered separately at a dosage of 400mg/kg, a reduction in parasitemia was still obtained, but it did not reach statistical significance. Toxicity studies yielded comforting results: the LD50 was estimated to be greater than 2779.5mg/kg. Moreover, mice exposed to the fourteen-day repeated-dose toxicity test (sub-acute toxicity test) did not display weight loss, liver or kidney morphological modifications, significant alterations in locomotor activity or any other sign of illness.

CONCLUSION

The antiplasmodial activity and the wide dose interval between the therapeutic dosage and the toxic dosage exhibited by the KA herbal combination in the murine malaria model argue in favor of its use as an antimalarial prophylactic remedy. It remains to be demonstrated by human clinical trials whether the combination remedy, when taken by inhabitants during malaria transmission season, can reduce parasite density and lead to a reduction of malaria episodes in the community.

Antiplasmodial triterpenoids from the fruits of neem, Azadirachta indica

Eight known and two new triterpenoid derivatives, neemfruitins A (9) and B (10), have been isolated from the fruits of neem, Azadirachta indica, a traditional antimalarial plant used by Asian and African populations. In vitro antiplasmodial tests evidenced a significant activity of the known gedunin and azadirone and the new neemfruitin A and provided useful information about the structure-antimalarial activity relationships in the limonoid class.

Transmission blocking activity of a standardized neem (Azadirachta indica) seed extract on the rodent malaria parasite Plasmodium berghei in its vector Anopheles stephensi

Background

The wide use of gametocytocidal artemisinin-based combination therapy (ACT) lead to a reduction of Plasmodium falciparum transmission in several African endemic settings. An increased impact on malaria burden may be achieved through the development of improved transmission-blocking formulations, including molecules complementing the gametocytocidal effects of artemisinin derivatives and/or acting on Plasmodium stages developing in the vector. Azadirachtin, a limonoid (tetranortriterpenoid) abundant in neem (Azadirachta indica, Meliaceae) seeds, is a promising candidate, inhibiting Plasmodium exflagellation in vitro at low concentrations. This work aimed at assessing the transmission-blocking potential of NeemAzal^®, an azadirachtin-enriched extract of neem seeds, using the rodent malaria in vivo model Plasmodium berghei/Anopheles stephensi.

Methods

Anopheles stephensi females were offered a blood-meal on P. berghei infected, gametocytaemic BALB/c mice, treated intraperitoneally with NeemAzal, one hour before feeding. The transmission-blocking activity of the product was evaluated by assessing oocyst prevalence, oocyst density and capacity to infect healthy mice. To characterize the anti-plasmodial effects of NeemAzal^® on early midgut stages, i.e. zygotes and ookinetes, Giemsa-stained mosquito midgut smears were examined.

Results

NeemAzal^® completely blocked P. berghei development in the vector, at an azadirachtin dose of 50 mg/kg mouse body weight. The totally 138 examined, treated mosquitoes (three experimental replications) did not reveal any oocyst and none of the healthy mice exposed to their bites developed parasitaemia. The examination of midgut content smears revealed a reduced number of zygotes and post-zygotic forms and the absence of mature ookinetes in treated mosquitoes. Post-zygotic forms showed several morphological alterations, compatible with the hypothesis of an azadirachtin interference with the functionality of the microtubule organizing centres and with the assembly of cytoskeletal microtubules, which are both fundamental processes in Plasmodium gametogenesis and ookinete formation.

Conclusions

This work demonstrated in vivo transmission blocking activity of an azadirachtin-enriched neem seed extract at an azadirachtin dose compatible with 'druggability' requisites. These results and evidence of anti-plasmodial activity of neem products accumulated over the last years encourage to convey neem compounds into the drug discovery & development pipeline and to evaluate their potential for the design of novel or improved transmission-blocking remedies.

Antiplasmodial activity of Punica granatum L. fruit rind

AIM OF THE STUDY

Sun-dried rind of the immature fruit of Punica granatum L. (Punicaceae) (Pg) is presently used as a herbal formulation (OMARIA) in Orissa, India, for the therapy and prophylaxis of malaria. The aims of this study were (i) to assess in vitro the antiplasmodial activity of the methanolic extract, of a tannin enriched fraction and of compounds/metabolites of the antimalarial plant, (ii) to estimate the curative efficacy of the Pg extracts and (iii) to explore the mechanism of action of the antiplasmodial compounds. Urolithins, the ellagitannin metabolites, were also investigated for antiplasmodial activity.

MATERIALS AND METHODS

Chloroquine-susceptible (D10) and -resistant (W2) strains of Pf were used for in vitro studies and the rodent malaria model Plasmodium berghei-BALB/c mice was used for in vivo assessments. Recombinant plasmepsins 2 and 4 were used to investigate the interference of Pg compounds with the metabolism of haemoglobin by malaria parasites.

RESULTS

The Pg methanolic extract (Pg-MeOH) inhibited parasite growth in vitro with a IC(50) of 4.5 and 2.8 microg/ml, for D10 and W2 strain, respectively. The activity was found to be associated to the fraction enriched with tannins (Pg-FET, IC(50) 2.9 and 1.5 microg/ml) in which punicalagins (29.1%), punicalins, ellagic acid (13.4%) and its glycoside could be identified. Plasmepsin 2 was inhibited by Pg-MeOH extract and by Pg-FET (IC(50) 7.3 and 3.0 microg/ml), which could partly explain the antiparasitic effect. On the contrary, urolithins were inactive. Both Pg-MeOH extract and Pg-FET did not show any in vivo efficacy in the murine model.

CONCLUSIONS

The in vitro studies support the use of Pg as antimalarial remedy. Possible explanations for the negative in vivo results are discussed.

Old and new targets for innovative antimalarial compounds: the different strategies of the Italian Malaria Network

Clinical treatment-failures to affordable drugs encouraged new investigation for discovery and development of new prophylactic and therapeutic interventions against malaria. The Drug Discovery Cluster (DDcl) of the Italian Malaria Network gathers several highly integrated and complementary laboratories from different Italian Institutions to identify, synthesise, screen in vitro and in vivo new antimalarial molecules directed against the intraerythrocytic stage of P. falciparum parasites and/or with transmission blocking activity to select lead compounds for further development. Complementary research activities, both in vitro and in the clinics, aim at investigating the pathogenetic mechanisms of severe malaria anaemia and the different manifestations of the disease in malaria-HIV co-infected patients to identify new therapies and improve survival.

Impact of the botanical insecticide Neem Azal on survival and reproduction of the biting louse Damalinia limbata on angora goats

Secondary metabolites present in the neem tree (Azadirachta indica A. Juss, Meliaceae), exhibit a wide range of biological activities in insects. However, few studies have been undertaken to assess the potential of neem products as insecticides for the control of ectoparasites of domestic animals. This study was undertaken to estimate the efficacy of Neem Azal, an azadirachtin-rich extract of neem seeds, in controlling Damalinia limbata (Phthiraptera) louse infestation of angora goats. The study was conducted on a fibre animal farm situated in Central Italy. Groups of 11-12 goats were treated with Neem Azal at an azadirachtin concentration of 650ppm or 125ppm, with Neguvon or were left untreated. Their louse burden was assessed fortnightly to monthly for 22 weeks. A reduction in louse densities of 76-96% was observed from week 2 to week 18 after treatment with the neem solution containing azadirachtin at a concentration of 650ppm. At the lower test concentration (125ppm) a reduction of 60-92% could be recorded from week 2 to week 14. Neem Azal was found to reduce the survival of both adult and nymph stages of D. limbata and to interfere with oviposition and oogenesis of female lice. A decrease in oviposition was observed in neem exposed female lice and the examination of their ovaries revealed morphological alterations in both vitellogenic and previtellogenic ovarioles at the follicular and germinal level. Since neem compounds target different life stages and physiological processes of D. limbata, the development of insecticide resistance by biting lice exposed to neem-based insecticides appears unlikely. For this reason and for its prolonged activity, which in principle allows angora goats to be protected for a large part of the mohair production cycle, neem-based insecticides may have a potential interest for mohair producing breeders.

Effects of a neem extract on blood feeding, oviposition and oocyte ultrastructure in Anopheles stephensi Liston (Diptera: Culicidae)

Secondary metabolites of the neem tree (Azadirachta indica A. Juss., Meliaceae) exhibit a wide range of biological activities in insects. However, few studies have addressed the effects of neem extracts or compounds in arthropods of medical importance. In this study, a laboratory strain of Anopheles stephensi was used to assess the effects of a commercial formulation (Neem Azal) (NA)), containing azadirachtin A at 34%, on blood feeding, oviposition and oocyte ultrastructure. Oral administration of Neem Azal) to A. stephensi females through artificial blood meals did impair blood intake and oviposition in a concentration dependent manner. Similar results were obtained on females, which had consumed Neem Azal) in sucrose solution before taking a blood meal of plain blood. Neem treated females displayed a delay in oocyte development in both the phase of vitellogenesis and the phase of choriogenesis. The ultrastructural studies on ovaries from Neem Azal) treated females revealed distinct structural modifications indicative of: (i) a complete block of oogenesis, (ii) impairment of vitellogenesis and vitelline envelope formation, (iii) a severe degeneration of follicle cells. In agreement with results obtained in other insects, this study indicates that Neem Azal) impairs hormone control of oogenesis and exerts a cytotoxic effect on both follicular cells and oocytes of the Asian malaria vector A. stephensi.

Host preferences of phlebotomine sand flies at a hypoendemic focus of canine leishmaniasis in central Italy

A survey was carried out on phlebotomine sand flies and their feeding habits at a hypoendemic focus of Leishmania infantum in Macerata province, central Italy. During two consecutive years (2000-2001), 1465 sand fly specimens (42.5% of which were males) were collected from a variety of diurnal resting sites in the municipality of Camerino. The most prevalent species was Phlebotomus perniciosus (76.6%), followed by P. papatasi (10.4%), Sergentomyia minuta (9.1%), Phlebotomus perfiliewi (3.3%) and P. mascittii (0.5%). Among the 842 females collected, 578 (68.6%) were blood-fed. Based on the results of blood meal analyses, P. perniciosus fed on man, dogs, equines, sheep and birds; P. perfiliewi on dogs, equines, sheep and birds; P. papatasi on dogs, equines and birds. Two specimens of P. mascittii fed on equines. Forage ratios (FRs) and host selectivity indices gave different results for the large domestic animals. More than 95% of the specimens collected inside a stable, dog kennel, sheep pen and chicken house were found to have fed on the animals housed in the respective shelters. In addition, at one collecting site where almost all the hosts mentioned above were present simultaneously, both P. perniciosus and P. perfiliewi were found to have fed on all five species, indicating that host choice was probably related to its availability (i.e. number and size) rather than specific attractiveness. The feeding habits of the two Leishmania vectors may have implications for the epidemiology of leishmaniasis in urban and peri-urban areas, where sand fly females deprived of other vertebrate hosts (particularly the larger species) may begin to bite humans and dogs more frequently.

An estimation of Toxocara canis prevalence in dogs, environmental egg contamination and risk of human infection in the Marche region of Italy

The human risk of infection with larvae of Toxocara canis was estimated in people from the Marche region of Italy. This region includes both urban and rural areas and its inhabitants frequently keep dogs for company, hunting, as guardians or shepherds. T. canis infection was diagnosed in 33.6% out of 295 dogs examined. Nearly half of the dogs (48.4%) living in rural areas were found T. canis positive, compared to about one-quarter of the dogs (26.2%) from urban areas. Analysis by provenance and role revealed the highest infection rate in rural hunting dogs (64.7%) and the lowest in urban companion dogs (22.1%). According to questionnaire data, the peridomestic environment, i.e. gardens and dog pens, is the most important defecation site in both rural and urban areas. Since over 40% of the dogs who defecate in dog pens are infected and 24% of urban and 47% of rural dogs who leave their droppings in the house surroundings harbour the parasite, it is clear that these environments may constitute sites of zoonotic risk. Our analysis of soil samples from 60 farms confirmed the high contamination level, revealing positive soil samples in more than half of the farms. Substantial egg contamination was also found in urban areas, as 3/6 parks examined were Toxocara spp. positive. Finally, our serological findings indicate that human infection actually occurs in the area: 7 out of 428 adults examined (1.6%) had very high levels of antibodies to T. canis antigen, suggesting a previous contact with the Larva migrans of the nematode.

Insecticide-treated materials, mosquito adaptation and mass effect: entomological observations after five years of vector control in Burkina Faso

Insecticide-treated bednets and curtains have been shown to be successful in reducing malaria transmission and child mortality in Africa over periods of up to 2 years. A major concern relating to this approach is that, in time, it will be compromised by the selection of mosquito genotypes that are resistant at the biochemical or behavioural level. We report entomological data from a large area in Burkina Faso where insecticide-treated curtains have been in use for up to 5 years. Longitudinal indoor and outdoor CDC light-trap catches were performed in 4 sentinel villages. In addition cross-sectional surveys using indoor spray catches and outdoor CDC light-trap catches were performed each September in a larger number of villages, including 8 located outside the intervention area. We found no evidence of the selection of mosquito phenotypes that might compromise the intervention. Indoor and outdoor vector densities remained very low after 5 years of intervention, both compared with pre-intervention levels and with concurrent levels outside the intervention area. We found no evidence of a switch to outdoor rather than indoor biting. The proportion of blood meals taken on humans may have decreased but our data are inconclusive on this point. We observed higher vector densities and sporozoite rates at the periphery of the intervention zone than at the centre, which may reflect re-invasion of peripheral villages by mosquitoes from outside the intervention area. In 'real life' programmes, with perhaps patchy, less than optimal coverage, the protection against malaria transmission provided to individuals using insecticide-treated materials may be less than that achieved in the randomized controlled trials which demonstrated an impact of insecticide-treated materials on child mortality.

Wide-scale installation of insecticide-treated curtains confers high levels of protection against malaria transmission in a hyperendemic area of Burkina Faso

In a region of Sudanese savannah in Burkina Faso, insecticide-treated curtains were installed in 8 out of 16 zones, each covering an area of about 50 km2. Longitudinal entomological monitoring using CDC light traps was performed in 4 villages (2 intervention, 2 control) over a period of 3 years (including 1 year prior to intervention). In the 3rd year a cross-sectional entomological survey using spray catches was performed in 84 villages (40 intervention). Indoor vector densities in protected houses showed large reductions (P = 0.01). The available data were also consistent with an impact on outdoor and unprotected indoor densities. The proportion of mosquitoes carrying sporozoites was 4.1% in protected villages compared with 11.5% in unprotected villages (P = 0.07). Entomological inoculation rates fell substantially (P = 0.01), reflecting these reductions. The impact of this intervention on mosquito survival appears to have been greater than those in similar trials conducted in the Gambia, Ghana and Kenya in which the intervention was applied over smaller areas.

Widespread distribution of insecticide-impregnated curtains reduces child mortality, prevalence and intensity of malaria infection, and malaria transmission in rural Burkina Faso

The results of the first two years of implementation of a large scale trial of insecticide-treated curtains in Burkina Faso are summarised in this presentation. The trial was conducted in a highly malarious area and involved a population of slightly less than 100,000, distributed in 158 villages over an area of almost 1000 km2. A remarkable impact on entomological parameters (Anopheles density, sporozoite rate, entomological inoculation rate) was accompanied by a relatively modest reduction of parasitological indices (prevalence and density of Plasmodium falciparum). All-cause mortality in children 0.5 to 5 year old showed over two years a 15% decline. The authors believe that the wide surface of the protected zone and the almost total coverage achieved in the intervention villages were the major determinants of the observed reduction of transmission. A conclusive interpretation of the mortality results requires a further follow-up of the study population.

Insecticide-treated curtains reduce the prevalence and intensity of malaria infection in Burkina Faso

A large, randomized controlled trial to investigate the impact of insecticide-treated curtains (ITC) on child mortality was conducted in an area of seasonal, holoendemic malaria in Burkina Faso. 158 communities totalling some 90,000 people were censused and grouped into 16 geographical clusters, 8 of which were randomly selected to receive ITC in June-July 1994, just prior to the rainy season. In September-October 1995, at the peak period of malaria transmission, a cross-sectional survey was conducted in 84 of the villages. A random sample of 905 children aged 6-59 months was identified and visited. 763 children (84%) were present at the time of the visit and recruited into the study. Mothers were asked about fever in the past 24 h, the child's temperature was taken, and a sample of blood collected to identify and quantify malaria infections and to measure haemoglobin (Hb) levels. Children protected by ITC were less likely to be infected with Plasmodium falciparum (risk ratio = 0.92; 95% CI 0.86, 0.98) or P. malariae (risk ratio = 0.42, 95% CI 0.19, 0.95). The mean intensity of P. falciparum infections was lower among children protected by ITC (899 vs. 1583 trophozoites/microliter; P < 0.001), while the mean Hb level was 0.4 g/dl higher (P < 0.001). While we found no evidence that ITC had an impact on the prevalence of malaria-associated fever episodes, the confidence intervals around our estimates of the impact of ITC on malaria morbidity were wide. We conclude that widespread implementation of ITC in this area of high malaria transmission led to a modest reduction in the prevalence of malaria infection and to a more substantial reduction in the intensity of these infections which caused increased Hb levels. We were unable to demonstrate any impact of ITC on malaria morbidity, but the wide confidence intervals around our point estimates do not preclude the possibility of a substantial impact.

Do insecticide-treated curtains reduce all-cause child mortality in Burkina Faso?

To evaluate whether insecticide-treated netting (ITN) reduces child mortality in different epidemiological settings, 4 large, randomized, controlled trials were conducted in Africa. Here we report the findings from the trial in Burkina Faso, in an area of hyperendemic and markedly seasonal malaria transmission. The trial involved 158 villages, with a total population of some 90,000, grouped into 16 geographical clusters. Ascertainment of mortality among children aged 6-59 months began in early 1993. In June/July 1994, 8 of the clusters, randomly selected, received permethrin-treated curtains. Follow-up of children and ascertainment of mortality continued until May 1996. A 15% reduction in all-cause mortality among children aged 6-59 months was observed over the 2-year period following the installation of the curtains (95% c.i. -4% to 30%). In the first year, post-intervention mortality was substantially lower in the clusters receiving curtains compared with the control clusters (rate ratio = 0.74; 95% c.i. 0.57, 0.95) but in the second year, there was no difference between mortality in the two groups (rate ratio = 0.99). The overall two-year impact of the intervention is consistent with the impacts observed in other trials which have demonstrated reductions in child mortality of from 17% to 33%. However, the year-by-year analysis raises some concerns about the long-term effect of ITN. Further follow-up of this population is warranted.

Comparison of two methods for assessing child mortality in areas without comprehensive registration systems

We compared the effectiveness of 2 approaches to assessing child deaths in a rural area of Burkina Faso, West Africa. Censuses, repeated yearly, identified 410 child deaths in the age range 6-59 months. Surveillance using community informants identified only 319 deaths. The estimated sensitivities of the 2 systems were 97% and 76%, respectively. Both systems appeared less effective at detecting child deaths before 6 months of age (sensitivities 74% and 57%). Most of the deaths missed by the census were of children born since the previous census. The cost of one year's surveillance was twice that of a single census. The marginal cost of the surveillance system per additional child death identified between 6 and 59 months was about US$ 1500. Thorough annual censuses may be sufficient to ascertain almost all child deaths over 6 months of age. In studies wishing to identify child deaths before 6 months of age, such an approach is unlikely to be adequate. In such situations, our data indicated that the use of unpaid community informants can improve assessment of deaths. Where accurate assessment of early infant death rate is required, regular visits to each household by members of the study team are likely to be the only reliable approach.

Localization of HLA-A2.1-restricted T cell epitopes in the circumsporozoite protein of Plasmodium falciparum

Localization of human MHC class I-restricted T cell epitopes in the circumsporozoite (CS) protein of the human parasite Plasmodium falciparum is an important objective in the development of antimalarial vaccines. To this purpose, we synthesized a series of overlapping synthetic 20-mer peptides, spanning the entire sequence of the 7G8 CS molecule except for the central repeat B cell domain. The P.f.CS peptides were first tested for their ability to bind to the human MHC class I HLA-A2.1 molecule on T2, a human cell line. Subsequently, the use of a series of shorter peptide analogues allowed us to determine the optimal A2.1 binding sequence present in several of the 20-mers. Binding P.f.CS peptides were further tested for their capacity to activate PBL from HLA-A2.1+ immune donors living in a malaria-endemic area. Specific IFN-gamma production was detected in the supernatant of cultures of PBL from exposed individuals. Cytotoxic T cell lines and clones were derived from the PBL of one responder, and their activity was shown to be HLA-A2.1-restricted and specific for the peptide 334-342 of the CS protein. In addition, double transgenic HLA-A2.1 x human beta 2-microglobulin mice were immunized with peptide 1-10 of the CS protein. T cells derived from immune lymph nodes displayed a peptide-specific HLA-A2.1-restricted cytolytic activity after one in vitro stimulation.

Localization of HLA-A2.1-restricted T cell epitopes in the circumsporozoite protein of Plasmodium falciparum

Localization of human MHC class I-restricted T cell epitopes in the circumsporozoite (CS) protein of the human parasite Plasmodium falciparum is an important objective in the development of antimalarial vaccines. To this purpose, we synthesized a series of overlapping synthetic 20-mer peptides, spanning the entire sequence of the 7G8 CS molecule except for the central repeat B cell domain. The P.f.CS peptides were first tested for their ability to bind to the human MHC class I HLA-A2.1 molecule on T2, a human cell line. Subsequently, the use of a series of shorter peptide analogues allowed us to determine the optimal A2.1 binding sequence present in several of the 20-mers. Binding P.f.CS peptides were further tested for their capacity to activate PBL from HLA-A2.1+ immune donors living in a malaria-endemic area. Specific IFN-gamma production was detected in the supernatant of cultures of PBL from exposed individuals. Cytotoxic T cell lines and clones were derived from the PBL of one responder, and their activity was shown to be HLA-A2.1-restricted and specific for the peptide 334-342 of the CS protein. In addition, double transgenic HLA-A2.1 x human beta 2-microglobulin mice were immunized with peptide 1-10 of the CS protein. T cells derived from immune lymph nodes displayed a peptide-specific HLA-A2.1-restricted cytolytic activity after one in vitro stimulation.

In vitro immune recognition of synthetic peptides from the Plasmodium falciparum CS protein by individuals naturally exposed to different sporozoite challenge

The impact of duration and intensity of sporozoite challenge on the in vitro cell immune response to synthetic peptides of the circumsporozoite (CS) protein of Plasmodium falciparum was investigated in residents of a malaria endemic area in Burkina Faso (West Africa). Lymphocyte proliferation and interferon-gamma (IFN-gamma) production were used to assess immune recognition of synthetic peptides corresponding to the polymorphic Th2R and Th3R regions, to the conserved CS.T3 sequence and to NANP and degenerate NVDP repeats. Immune responses were measured in adults and children from a village where they received more than 100 sporozoite inoculations per year and in adults living in a town, exposed to a 10-100 times lower challenge. A lifetime intense exposure apparently increased the ability to proliferate in response to most peptides in the rural adults, who all produced antibodies to NANP repeats. Surprisingly, cell cultures from these subjects seldom contained appreciable levels of IFN-gamma. In the urban adults, possibly due to the moderate challenge they are exposed to, significant differences in the proliferative potentials of the peptides could be detected. The highest stimulation indices were obtained with the genetically unrestricted CS.T3 peptide. Remarkably, proliferative responses to Th2R and Th3R appeared to be correlated with the humoral response to the CS protein, indicating a T helper significance of the epitopes. The differing proliferative potential of the polymorphic epitopes in the urban adults suggests that polymorphism might delay the development of immune responsiveness under conditions of sporadic transmission. The children from the highly malarious village displayed the lowest proliferative scores, accompanied by a high prevalence of antibodies to NANP repeats. On the basis of these findings, the hypothesis is proposed that a pure B cell reactivity to NANP repeats could ontogenetically precede the mounting of a conventional T-B cooperative immune response.

Detecting malaria sporozoites in live, field-collected mosquitoes

A method is described for identifying malaria-infected mosquitoes, without killing them or hampering their fitness. Individual mosquitoes were induced to salivate on coverslips, and sporozoites, deposited on the glass surface, were visualized by Giemsa staining. Of 21 mosquitoes found to contain sporozoites by salivary gland dissection, 13 had delivered sporozoites on coverslips. A positive correlation was found between the amount of saliva expelled and ejection of sporozoites, indicating that the sensitivity of the method may be increased by improving the probing behaviour of the mosquitoes. The procedure described may be suitable for selecting infected mosquitoes which are able to eject sporozoites during probing. Being applicable to wild Anopheles and to large numbers of mosquitoes, the method lends itself for use in field studies on malaria.

Multiple antigen peptides for specific detection of antibodies to a malaria antigen in human sera

Multiple antigen peptides (MAP), consisting of a number of peptide copies synthesized on a branching lysyl core, offer a novel approach for rendering small peptides immunoreactive in solid-phase immunoassays. An octameric MAP, carrying 6 repeats of the sequence -N-A-A-G-, tandem repeated in the immunodominant region of the circumsporozoite (CS) protein of Plasmodium malariae, was used as a model to evaluate the suitability of the MAP system in an indirect enzyme-linked immunosorbent assay (ELISA) for detecting antibodies against a parasite antigen in individuals exposed to natural infection. The reaction of endemic sera in ELISA on MAP8-(NAAG)6 was related to that obtained in immunofluorescence on sporozoites, indicating the specificity of the antibody-MAP interaction. The reactivity of immune sera was found to be directed only against the (NAAG)6 moiety of the MAP and not against the lysyl core, since antibody binding to MAP8-(NAAG)6 was completely inhibited by (NAAG)6-NA monomer, but remained uninfluenced when lysyl core was used as competing ligand. The levels of antibodies to MAP8-(NAAG)6, in two groups of individuals naturally exposed to malaria infection, appeared to be related to their respective exposure to the parasite.

Waiting for the vaccine: sporozoite vaccine research entails important progress in malaria epidemiology

The research efforts aimed at developing a vaccine against malaria, although failing thus far in their main objective, have produced molecular tools of great utility for epidemiological studies. For example, monoclonal antibodies directed against the repeats of Plasmodium circumsporozoite (CS) protein allowed the 2-site assay for detecting sporozoites in mosquitoes to be established. This immunoassay is advantageous compared with the conventional method of salivary gland dissection and microscopic examination, for it makes the identification of the sporozoite species possible, thanks to species-specific aminoacid sequences of the CS repeats. Other examples of vaccine research-derived tools are synthetic peptides reproducing the repetitive part of the CS protein, which allow antibodies to sporozoites, in individuals exposed to malaria, to be detected. Antibodies to the CS repeats of Plasmodium (Laverania) falciparum proved to be a reliable indicator of the intensity of malaria transmission and, therefore, were suitable for monitoring the impact of malaria control programmes. Finally, a project is outlined that, relying on the application of these tools, will aim at characterizing the transmission of Plasmodium (Plasmodium) malariae and at unveiling the possible relationship among different species thriving in the same distribution area, an issue which may become of relevance in view of the likely introduction of a vaccine directed against a single species.

Permethrin-impregnated curtains in malaria control

The impact of permethrin-impregnated curtains on the incidence of malaria episodes, parasitaemia and splenomegaly was assessed during a 22 month period in 2 groups of children aged 0.5-6 years. One group lived in houses where permethrin-impregnated curtains had been installed, the other group lived in houses without curtains. A significant reduction of incidence of malaria episodes, mean parasite density, parasite prevalence and splenomegaly was consistently observed in the intervention group towards the end of the period of moderate transmission, whereas no clear-cut impact could be demonstrated during the high transmission period. The influence of malaria pressure and community utilization on the protective efficiency of curtains is discussed. Because of their acceptability and the ease of reimpregnation, curtains proved to be a suitable technique for integration into primary health care.

Intraerythrocytic administration of a synthetic Plasmodium antigen elicits antibody response in mice, without carrier molecules or adjuvants

The synthetic peptide (NANP)40, reproducing the tandem-repeated epitope of the circumsporozoite protein of Plasmodium (Laverania) falciparum, was entrapped into murine, autologous erythrocytes by a hypotonic dialysis method. Mice immunized intravenously with minute amounts of encapsulated peptide produced considerable antibody titres. This result indicates that intraerythrocytic antigen administration may have a potential as an immunization system for humans, since it dispenses with adjuvants and carrier molecules.