Parasites & Vectors would like to thank the following for their assistance with peer review of manuscripts for the journal in 2012.
The suppression of indoor malaria transmission requires additional interventions that complement the use of insecticide treated nets (ITNs) and indoor residual spraying (IRS). Previous studies have examined the impact of house structure on malaria transmission in areas of low transmission. This study was conducted in a high transmission setting and presents further evidence about the association between specific house characteristics and the abundance of endophilic malaria vectors.
Mosquitoes were sampled using CDC light traps from 72 randomly selected houses in two villages on a monthly basis from 2008 to 2011 in rural Southern Tanzania. Generalized linear models using Poisson distributions were used to analyze the association of house characteristics (eave gaps, wall types, roof types, number of windows, rooms and doors, window screens, house size), number of occupants and ITN usage with mean catches of malaria vectors (An.gambiae s.l. and An. funestus).
A total of 36490 female An. gambiae s.l. were collected in Namwawala village and 21266 in Idete village. As for An. funestus females, 2268 were collected in Namwawala and 3398 in Idete. Individually, each house factor had a statistically significant impact (p < 0.05) on the mean catches for An. gambiae s.l. but not An. funestus. A multivariate analysis indicated that the combined absence or presence of eaves, treated or untreated bed-nets, the number of house occupants, house size, netting over windows, and roof type were significantly related (p < 0.05) to An.gambiae s.l. and An. funestus house entry in both villages.
Despite significant reductions in vector density and malaria transmission caused by high coverage of ITNs, high numbers of host-seeking malaria vectors are still found indoors due to house designs that favour mosquito entry. In addition to ITNs and IRS, significant efforts should focus on improving house design to prevent mosquito entry and eliminate indoor malaria transmission.
House risk factors; Anopheles gambiae s.l.; Anopheles funestus; ITNs; Malaria
The occurrence of infections by Dirofilaria immitis in canine and human populations depends on several factors linked to both the definitive and intermediate hosts. Little data are available on the risk of human and dog exposure to D. immitis in endemic areas. Data collected on dog- and human-bait traps in endemic areas of north-eastern Italy were used to estimate the likelihood of a receptive host coming into contact with an infected vector.
From 1997 to 1999, mosquitoes were collected from three sampling sites of north-eastern Italy on D. immitis microfilaraemic dogs and on human baits. The bite/night/host rates were determined based on the number of feeding and probing mosquitoes on dogs and humans, respectively. The survival/mortality rates of different species of mosquitoes following the blood meal, and the rate of natural Dirofilaria infection in unfed specimens were estimated. The risk of exposure of dogs and humans to infected mosquito species was determined by combining the bite/host/night and the mosquito infection rates.
A total of 1,165 mosquitoes were collected on human (n = 815) and dog (n = 350) baits with varying species composition (i.e., Culex pipiens, 87.3% and Ochlerotatus caspius, 11.6%). Overall, dogs were more attractive to Cx pipiens than humans (feeding rate 70.2% vs probing rate 25.9%). The highest bite/night/host rate was 84.0 for dogs and 26.5 for humans. Cx pipiens displayed a mortality rate of 76.3% within 13 days and Oc. caspius of 100% within two days following the infective blood meal. In addition, D. immitis DNA was detected in unfed Cx pipiens (infection rate of 0.26%-2.07%). The infection rate adjusted for mosquito mortality was 0.38%. Based on data collected, the contact between an infected mosquito and a host can occur as often as every four nights for D. immitis infected-mosquitoes in dogs and within two weeks for humans.
Cx pipiens was confirmed as the most efficient natural vector of D. immitis in the studied area. In endemic areas, the risk of transmission can be very high for dogs and relevant for humans. Despite the increased awareness of veterinarians and owners on canine dirofilarioses, dogs from rural areas still maintain the natural life cycle of Dirofilaria spp., therefore acting as a source of infection to humans through vector bites.
Dirofilaria immitis; Mosquito vectors; Dogs; Humans; Risk of exposure
Publications are often used as a measure of success of research work. Leishmaniasis is considered endemic in 98 countries, most of which are developing. This article describes a bibliometric review of the literature on leishmaniasis research indexed in PubMed during a 66-year period.
Medline was used via the PubMed online service of the US National Library of Medicine. The search strategy was Leishmania [MeSH] or leishmaniasis [MeSH] from 1 January 1945 until 31 December 2010. Neither language nor document type restrictions were employed.
A total of 20,780 references were retrieved. The number of publications increased steadily over time, with 3,380 publications from 1945-1980 to 8,267 from 2001-2010. Leishmaniasis documents were published in 1,846 scientific journals, and Transactions of the Royal Society of Tropical Medicine and Hygiene (4.9%) was the top one. The USA was the predominant country by considering the first author’s institutional address (16.8%), followed by Brazil (14.9%), and then India (9.0%), however Brazil leads the scientific output in 2001-2010 period (18.5%), followed by the USA (13.5%) and India (10%). The production ranking changed when the number of publications was normalised by population (Israel and Switzerland), by gross domestic product (Nepal and Tunisia), and by gross national income per capita (India and Ethiopia). For geographical area, Europe led (31.7%), followed by Latin America (24.5%).
We have found an increase in the number of publications in the field of leishmaniasis. The USA and Brazil led scientific production on leishmaniasis research.
Leishmaniasis; Leishmania; Bibliometry; Scientific production; Mapping; Leishmaniasis visceral; Leishmaniasis cutaneous; Leishmaniasis mucocutaneous; Diffuse cutaneous Leishmaniasis
Mosquito feeding behaviour plays a major role in determining malaria transmission intensity and the impact of specific prevention measures. Human Landing Catch (HLC) is currently the only method that can directly and consistently measure the biting rates of anthropophagic mosquitoes, both indoors and outdoors. However, this method exposes the participant to mosquito-borne pathogens, therefore new exposure-free methods are needed to replace it.
Commercially available electrocuting grids (EGs) were evaluated as an alternative to HLC using a Latin Square experimental design in Dar es Salaam, Tanzania. Both HLC and EGs were used to estimate the proportion of human exposure to mosquitoes occurring indoors (πi), as well as its two underlying parameters: the proportion of mosquitoes caught indoors (Pi) and the proportion of mosquitoes caught between the first and last hour when most people are indoors (Pfl).
HLC and EGs methods accounted for 69% and 31% of the total number of female mosquitoes caught respectively and both methods caught more mosquitoes outdoors than indoors. Results from the gold standard HLC suggest that An. gambiae s.s. in Dar es Salaam is neither exophagic nor endophagic (Pi ≈ 0.5), whereas An. arabiensis is exophagic (Pi < < 0.5). Both species prefer to feed after 10pm when most people are indoors (Pfl > > 0.5). EGs yielded estimates of Pi for An. gambiae s.s., An. arabiensis and An. coustani, that were approximately equivalent to those with HLC but significantly underestimated Pfl for An. gambiae s.s. and An. coustani. The relative sampling sensitivity of EGs declined over the course of the night (p ≤ 0.001) for all mosquito taxa except An. arabiensis.
Commercial EGs sample human-seeking mosquitoes with high sensitivity both indoors and outdoors and accurately measure the propensity of Anopheles malaria vectors to bite indoors rather than outdoors. However, further modifications are needed to stabilize sampling sensitivity over a full nocturnal cycle so that they can be used to survey patterns of human exposure to mosquitoes.
Electrocuting grids; Human landing collections; Mosquito; Malaria; Behaviour
Considering the increasing importance of small animals travel medicine and the spread of filariae with zoonotic potential to non-endemic European areas, routine filarial diagnosis in dogs is becoming important. Dirofilaria immitis, D. repens, Acanthocheilonema dracunculoides and A. reconditum are the most common canine filarial nematodes presenting blood circulating microfilariae (mf) which can be differentiated to species level by the acid phosphatase activity patterns or by PCR. Available data on the size of the mf vary considerably in the literature. The aim of this study was to validate morphometric criteria for filarial identification in blood samples of dogs after concentration of mf with the modified Knott’s technique.
Morphometric analysis of 10 mf from samples identified to species level by acid phosphatase activity and partially confirmed by PCR were performed with specimens from 377 dogs.
The mean length and width of D. immitis mf from 60 dogs were 301.77±6.29 μm and 6.30±0.26 μm, of D. repens mf from 171 dogs 369.44±10.76 μm 8.87±0.58 μm, of A. dracunculoides mf from 133 dogs 259.43±6.69 μm and 5.09±0.47 μm and of A. reconditum mf from 13 dogs 264.83±5.47 μm and 4.63±0.52 μm.
For a subset of 30 samples, morphometric analysis was repeated with identical results in two laboratories. Furthermore, the size of mf concentrated and fixed by the Knott’s technique was shown to be stable over 105 days.
The Knott’s test enables to clearly distinguish between D. immitis, D. repens and Acanthocheilonema spp. However, due to the overlapping size ranges of A. dracunculoides and A. reconditum, biochemical or molecular methods are required to distinguish these two species.
Canine blood microfilariae; Laboratory diagnosis; Size of microfilariae
Increasing incidence of DDT and pyrethroid resistance in Anopheles mosquitoes is seen as a limiting factor for malaria vector control. The current study aimed at an in-depth characterization of An. gambiae s.l. resistance to insecticides in Cameroon, in order to guide malaria vector control interventions.
Anopheles gambiae s.l. mosquitoes were collected as larvae and pupae from six localities spread throughout the four main biogeographical domains of Cameroon and reared to adults in insectaries. Standard WHO insecticide susceptibility tests were carried out with 4% DDT, 0.75% permethrin and 0.05% deltamethrin. Mortality rates and knockdown times (kdt50 and kdt95) were determined and the effect of pre-exposure to the synergists DEF, DEM and PBO was assessed. Tested mosquitoes were identified to species and molecular forms (M or S) using PCR-RFLP. The hot ligation method was used to depict kdr mutations and biochemical assays were conducted to assess detoxifying enzyme activities.
The An. arabiensis population from Pitoa was fully susceptible to DDT and permethrin (mortality rates > 98%) and showed reduced susceptibility to deltamethrin. Resistance to DDT was widespread in An. gambiae s.s. populations and heterogeneous levels of susceptibility to permethrin and deltamethrin were observed. In many cases, prior exposure to synergists partially restored insecticide knockdown effect and increased mortality rates, suggesting a role of detoxifying enzymes in increasing mosquito survival upon challenge by pyrethroids and, to a lower extent DDT. The distribution of kdr alleles suggested a major role of kdr-based resistance in the S form of An. gambiae. In biochemical tests, all but one mosquito population overexpressed P450 activity, whereas baseline GST activity was low and similar in all field mosquito populations and in the control.
In Cameroon, multiple resistance mechanisms segregate in the S form of An. gambiae resulting in heterogeneous resistance profiles, whereas in the M form and An. arabiensis insecticide tolerance seems to be essentially mediated by enzyme-based detoxification. Synergists partially restored susceptibility to pyrethroid insecticides, and might help mitigate the impact of vector resistance in the field. However, additional vector control tools are needed to further impact on malaria transmission in such settings.
Blastocystis has been described as the most common intestinal parasite in humans and has an increased impact on public health. However, the transmission of this parasite has not been conclusively determined.
To contribute to a better comprehension of the epidemiology of this infection, a cross-sectional survey aimed at providing the first documented data on the prevalence and risk factors associated with Blastocystis infection was carried out among three Orang Asli tribes (Proto-Malay, Negrito and Senoi) in selected villages at Negeri Sembilan, Perak and Pahang, Peninsular Malaysia. Faecal samples were examined by formalin-ether sedimentation and trichrome staining techniques.
Of 500 individuals, 20.4% (102) were detected positive for Blastocystis; 13.3% (20/150) of Proto-Malays, 21.6% (30/139) of Negritos and 24.7% (52/211) of Senois were positive for Blastocystis, respectively. The positive cases showed a decrease with increasing age and most of the positive cases were observed in individuals less than 15 years old. Multivariate analysis confirmed that drinking untreated water and the presence of other family members infected with Blastocystis were significant risk factors of infection among the three tribes and overall population studied.
Essentially, the findings highlighted that Blastocystis infection is prevalent among Orang Asli communities in Malaysia. Further studies using molecular approaches to distinguish the subtype of Blastocystis is needed. The present study also revealed that this infection may be transmitted through waterborne and human-to-human contact. Therefore, interventions with the provision of clean water supply for the communities and health education especially to the parents are urgently required.
Blastocystis; Waterborne; Human-to-human; Orang Asli; Malaysia
The Global Programme to Eliminate Lymphatic Filariasis (GPELF) was launched in 2000, and nearly all endemic countries in the Americas, Eastern Mediterranean and Asia-Pacific regions have now initiated the WHO recommended mass drug administration (MDA) campaign to interrupt transmission of the parasite. However, nearly 50% of the LF endemic countries in Africa are yet to implement the GPELF MDA strategy, which does not include vector control. Nevertheless, the recent scale up in insecticide treated /long lasting nets (ITNs/LLINs) and indoor residual spraying (IRS) for malaria control in Africa may significantly impact LF transmission because the parasite is transmitted mainly by Anopheles mosquitoes. This study examined the magnitude, geographical extent and potential impact of vector control in the 17 African countries that are yet to or have only recently started MDA.
National data on mosquito bed nets, ITNs/LLINs and IRS were obtained from published literature, national reports, surveys and datasets from public sources such as Demographic Health Surveys, Malaria Indicator Surveys, Multiple Indicator Cluster Surveys, Malaria Report, Roll Back Malaria and President’s Malaria Initiative websites. The type, number and distribution of interventions were summarised and mapped at sub-national level. and compared with known or potential LF distributions, and those which may be co-endemic with Loa loa and MDA is contraindicated.
Analyses found that vector control activities had increased significantly since 2005, with a three-fold increase in ITN ownership and IRS coverage. However, coverage varied dramatically across the 17 countries; some regions reported >70% ITNs ownership and regular IRS activity, while others had no coverage in remote rural populations where the risk of LF was potentially high and co-endemic with high risk L.loa.
Despite many African countries being slow to initiate MDA for LF, the continued commitment and global financial support for NTDs, and the concurrent expansion of vector control activities for malaria, is promising. It is not beyond the capacity of GPELF to reach its target of global LF elimination by 2020, but monitoring and evaluating the impact of these activities over the next decade will be critical to its success.
Lymphatic filariasis; Mass drug administration; Vector control; Long-lasting insecticidal nets; LLINs; Indoor residual spraying; IRS; Anopheles; Mosquitoes; Malaria
Anopheles merus, a sibling species of the Anopheles gambiae complex occurs along the East African coast but its biology and role in malaria transmission in this region is poorly understood. We evaluated the blood feeding pattern and the role of this species in malaria transmission in Malindi district, Coastal Kenya.
Adult mosquitoes were collected indoors by CDC light traps and Pyrethrum Spray Catch and outdoors by CDC light traps. Anopheles females were identified to species by morphological characteristics and sibling species of An. gambiae complex distinguished by rDNA polymerase chain reaction (PCR). Screening for host blood meal sources and presence or absence of Plasmodium falciparum circumsporozoite proteins was achieved by Enzyme Linked Immunosorbent Assays (ELISA).
Anopheles merus comprised 77.8% of the 387 Anopheles gambiae s.l adults that were collected. Other sibling species of Anopheles gambiae s.l identified in the study site included An. arabiensis(3.6%), and An. gambiae s.s. (8%). The human blood index for An. merus was 0.12, while the sporozoite rate was 0.3%.
These findings suggest that An. merus can play a minor role in malaria transmission along the Kenyan Coast and should be a target for vector control which in turn could be applied in designing and implementing mosquito control programmes targeting marsh-breeding mosquitoes; with the ultimate goal being to reduce the transmission of malaria associated with these vectors.
Current development efforts of subunit vaccines against Toxoplasma gondii, the etiological agent of toxoplasmosis, have been focused mainly on tachyzoite surface antigen 1 (SAG1). Since microparticles made from poly (lactide-co-glycolide) (PLG) polymers have been developed as safe, potent adjuvants or delivery systems, we aimed to encapsulate recombinant SAG1 (rSAG1) with the PLG polymers to prepare PLG-encapsulated rSAG1 (PLG-rSAG1) microparticles that would sustain rSAG1 release and generate long-lasting protective immunity against T. gondii in BALB/c mice.
In the present study, rSAG1 was encapsulated into PLG microparticles by the double emulsion method. PLG-rSAG1 microparticles were then intraperitoneally injected twice at a 14-day interval into BALB/c mice. We examined the ability of PLG-rSAG1 microparticles to induce and prolong effective anti-Toxoplasma immune responses, in comparison with rSAG1 formulated with a Vet L-10 adjuvant (rSAG1 (Vet L-10)). Eight weeks after the last immunization, protective activities were also evaluated after a lethal subcutaneous challenge of 1x104 live T. gondii tachyzoites.
PLG-rSAG1 microparticles, 4.25~6.58 micrometers in diameter, showed 69%~81% entrapment efficiency. The amount of released rSAG1 protein from microparticles increased gradually over a 35-day period and the protein still retained native SAG1 antigenicity. Intraperitoneal vaccination of mice with the microparticles resulted in enhanced SAG1-specific IgG titers as well as lymphocyte proliferation and, more importantly, these enhanced activities were maintained for 10 weeks. In addition, eight weeks after the last immunization, maximum production of gamma interferon was detected in mice immunized with PLG-rSAG1 microparticles. Furthermore, 80% (8/10) of mice immunized with PLG-rSAG1 microparticles survived at least 28 days after a lethal subcutaneous tachyzoite challenge.
Encapsulation of rSAG1 into PLG microparticles preserves the native SAG1 antigenicity and sustains the release of rSAG1 from microparticles. PLG-rSAG1 microparticles can effectively induce not only significant long-lasting SAG1-specific humoral and cell-mediated immune responses but also high protection against T. gondii tachyzoite infection. Our study provides a valuable basis for developing long-lasting vaccines against T. gondii for future use in humans and animals.
Toxoplasma gondii (T. gondii); Recombinant SAG1 (rSAG1); Poly (lactide-co-glycolide) (PLG); PLG-rSAG1 microparticles
Wolbachia are maternally inherited endosymbiotic bacteria that manipulate the reproductive success of their insect hosts. Uninfected females that mate with Wolbachia infected males do not reproduce due to cytoplasmic incompatibility (CI). CI results in the increased frequency of Wolbachia-infected individuals in populations. Recently, two Wolbachia strains, the benign wMel and virulent wMelPop have been artificially transinfected into the primary vector of dengue virus, the mosquito Ae. aegypti where they have formed stable infections. These Wolbachia infections are being developed for a biological control strategy against dengue virus transmission. While the effects of Wolbachia on female Ae. aegypti have been examined the effects on males are less well characterised. Here we ascertain and compare the effects of the two strains on male fitness in resource-limited environments that may better approximate the natural environment.
A series of population mating trials were conducted to examine the effect of Wolbachia infection status (with strains wMel and wMelPop) and male larval nutrition on insemination frequency, remating rates, the fecundity of females, the hatch rates of eggs and the wing length and fertility of males.
wMel and wMelPop infections reduce the fecundity of infected females and wMelPop reduces the viability of eggs. Low nutrition diets for males in the larval phase affects the fecundity of wMel-infected females. Neither strain of Wolbachia affected sperm quality or viability or the ability of males to successfully mate multiple females.
The benign strain of Wolbachia, wMel causes similar reductions in fecundity as the more virulent, wMelPop, and neither are too great that they should not still spread given the action of CI. The ability of Wolbachia-infected males to repeat mate as frequently as wildtype mosquitoes indicates that they will be very good agents of delivering CI in field release populations.
Mosquito; Fecundity; Symbiont; Multiple mating; Larval nutrition Wolbachia
Many parasites show an extraordinary degree of host specificity, even though a narrow range of host species reduces the likelihood of successful transmission. In this study, we evaluate the genetic basis of host specificity and transmission success of experimental F1 hybrids from two closely related tapeworm species (Schistocephalus solidus and S. pungitii), both highly specific to their respective vertebrate second intermediate hosts (three- and nine-spined sticklebacks, respectively).
We used an in vitro breeding system to hybridize Schistocephalus solidus and S. pungitii; hybridization rate was quantified using microsatellite markers. We measured several fitness relevant traits in pure lines of the parental parasite species as well as in their hybrids: hatching rates, infection rates in the copepod first host, and infection rates and growth in the two species of stickleback second hosts.
We show that the parasites can hybridize in the in vitro system, although the proportion of self-fertilized offspring was higher in the heterospecific breeding pairs than in the control pure parental species. Hybrids have a lower hatching rate, but do not show any disadvantages in infection of copepods. In fish, hybrids were able to infect both stickleback species with equal frequency, whereas the pure lines were only able to infect their normal host species.
Although not yet documented in nature, our study shows that hybridization in Schistocephalus spp. is in principle possible and that, in respect to their expanded host range, the hybrids are fitter. Further studies are needed to find the reason for the maintenance of the species boundaries in wild populations.
Leishmania species belong to the family Trypanosomatidae and cause leishmaniasis, a geographically widespread disease that infects humans and other vertebrates. This disease remains endemic in China. Due to the large geographic area and complex ecological environment, the taxonomic position and phylogenetic relationship of Chinese Leishmania isolates remain uncertain. A recent internal transcribed spacer 1 and cytochrome oxidase II phylogeny of Chinese Leishmania isolates has challenged some aspects of their traditional taxonomy as well as cladistics hypotheses of their phylogeny. The current study was designed to provide further disease background and sequence analysis.
We systematically analyzed 50 cytochrome b (cyt b) gene sequences of 19 isolates (16 from China, 3 from other countries) sequenced after polymerase chain reaction (PCR) using a special primer for cyt b as well as 31 sequences downloaded from GenBank. After alignment, the data were analyzed using the maximum parsimony, Bayesian and netwok methods.
Sequences of six haplotypes representing 10 Chinese isolates formed a monophyletic group and clustered with Leishmania tarentolae. The isolates GS1, GS7, XJ771 of this study from China clustered with other isolates of Leishmania donovani complex. The isolate JS1 was a sister to Leishmania tropica, which represented an L. tropica complex instead of clustering with L. donovani complex or with the other 10 Chinese isolates. The isolates KXG-2 and GS-GER20 formed a monophyletic group with Leishmania turanica from central Asia. In the different phylogenetic trees, all of the Chinese isolates occurred in at least four groups regardless of geographic distribution.
The undescribed Leishmania species of China, which are clearly causative agents of canine leishmaniasis and human visceral leishmaniasis and are related to Sauroleishmania, may have evolved from a common ancestral parasite that came from the Americas and may have split off earlier than the other old world Leishmania. Our results also suggest the following: the isolates GS7, GS1 and XJ771 occur as part of the L. donovani complex; the JS1 isolate is L. tropica; and the isolate GS-GER20 identified as Leishmania gerbilli is close to KXG-2 which is L. turanica.
Leishmania; Phylogeny; cyt b; China; Sauroleishmania
Indiscriminate use of synthetic insecticides to eradicate mosquitoes has caused physiological resistance. Plants provide a reservoir of biochemical compounds; among these compounds some have inhibitory effect on mosquitoes. In the present study the larvicidal, adulticidal and genotoxic activity of essential oil of Psoralea corylifolia Linn. against Culex quinquefasciatus Say was explored.
Essential oil was isolated from the seeds of P. corylifolia Linn. Larvicidal and adulticidal bioassay of Cx. quinquefasciatus was carried out by WHO method. Genotoxic activity of samples was determined by comet assay. Identification of different compounds was carried out by gas chromatography- mass spectrometry analysis.
LC50 and LC90 values of essential oil were 63.38±6.30 and 99.02±16.63 ppm, respectively against Cx. quinquefasciatus larvae. The LD50 and LD90 values were 0.057±0.007 and 0.109±0.014 mg/cm2 respectively against adult Cx. quinquefasciatus,. Genotoxicity of adults was determined at 0.034 and 0.069 mg/cm2. The mean comet tail length was 6.2548±0.754 μm and 8.47±0.931 μm and the respective DNA damage was significant i.e. 6.713% and 8.864% in comparison to controls. GCMS analysis of essential oil revealed 20 compounds. The major eight compounds were caryophyllene oxide (40.79%), phenol,4-(3,7-dimethyl-3-ethenylocta-1,6-dienyl) (20.78%), caryophyllene (17.84%), α-humulene (2.15%), (+)- aromadendrene (1.57%), naphthalene, 1,2,3,4-tetra hydro-1,6-dimethyle-4-(1-methyl)-, (1S-cis) (1.53%), trans- caryophyllene (0.75%), and methyl hexadecanoate (0.67%).
Essential oil obtained from the seeds of P. corylifolia showed potent toxicity against larvae and adult Cx. quinquefasciatus. The present work revealed that the essential oil of P. corylifolia could be used as environmentally sound larvicidal and adulticidal agent for mosquito control.
Larvicidal activity; Adulticidal activity; Genotoxicity; DNA damage; Essential oil; Psoralea corylifolia; Culex quinquefasciatus; GCMS
Millions of people and domestic animals around the world are affected by leishmaniasis, a disease caused by various species of flagellated protozoans in the genus Leishmania that are transmitted by several sand fly species. Insecticides are widely used for sand fly population control to try to reduce or interrupt Leishmania transmission. Zoonotic cutaneous leishmaniasis caused by L. major is vectored mainly by Phlebotomus papatasi (Scopoli) in Asia and Africa. Organophosphates comprise a class of insecticides used for sand fly control, which act through the inhibition of acetylcholinesterase (AChE) in the central nervous system. Point mutations producing an altered, insensitive AChE are a major mechanism of organophosphate resistance in insects and preliminary evidence for organophosphate-insensitive AChE has been reported in sand flies. This report describes the identification of complementary DNA for an AChE in P. papatasi and the biochemical characterization of recombinant P. papatasi AChE.
A P. papatasi Israeli strain laboratory colony was utilized to prepare total RNA utilized as template for RT-PCR amplification and sequencing of cDNA encoding acetylcholinesterase 1 using gene specific primers and 3’-5’-RACE. The cDNA was cloned into pBlueBac4.5/V5-His TOPO, and expressed by baculovirus in Sf21 insect cells in serum-free medium. Recombinant P. papatasi acetylcholinesterase was biochemically characterized using a modified Ellman’s assay in microplates.
A 2309 nucleotide sequence of PpAChE1 cDNA [GenBank: JQ922267] of P. papatasi from a laboratory colony susceptible to insecticides is reported with 73-83% nucleotide identity to acetylcholinesterase mRNA sequences of Culex tritaeniorhynchus and Lutzomyia longipalpis, respectively. The P. papatasi cDNA ORF encoded a 710-amino acid protein [GenBank: AFP20868] exhibiting 85% amino acid identity with acetylcholinesterases of Cx. pipiens, Aedes aegypti, and 92% amino acid identity for L. longipalpis. Recombinant P. papatasi AChE1 was expressed in the baculovirus system and characterized as an insect acetylcholinesterase with substrate preference for acetylthiocholine and inhibition at high substrate concentration. Enzyme activity was strongly inhibited by eserine, BW284c51, malaoxon, and paraoxon, and was insensitive to the butyrylcholinesterase inhibitors ethopropazine and iso-OMPA.
Results presented here enable the screening and identification of PpAChE mutations resulting in the genotype for insensitive PpAChE. Use of the recombinant P. papatasi AChE1 will facilitate rapid in vitro screening to identify novel PpAChE inhibitors, and comparative studies on biochemical kinetics of inhibition.
Sand fly; Acetylcholinesterase; P. papatasi; cDNA; AChE; JQ922267; AFP20868
Parasitological methods are widely used for the diagnosis of schistosomiasis. However, they are insensitive, particularly in areas of low endemicity, and labour-intensive. Immunoassays based on detection of anti-schistosome antibodies have the merit of high sensitivity and recently a rapid diagnostic test (RDT), incorporating Schistosoma mansoni cercarial transformation fluid (SmCTF) for detection of anti-schistosome antibodies in blood has been developed. Here, we assessed the diagnostic performance of the SmCTF-RDT for S. mansoni and S. haematobium infections by comparing it with microscopy for egg detection.
A cross-sectional survey was carried out in Azaguié, south Côte d’Ivoire. 118 pre-school-aged children submitted two stool and two urine samples, which were subjected to the Kato-Katz and urine filtration methods for the detection of S. mansoni and S. haematobium eggs, respectively. Urine was also subjected to a commercially available cassette test for S. mansoni, which detects circulating cathodic antigen. A finger-prick blood sample was used for the SmCTF-RDT for detection of anti-S. mansoni and anti-S. haematobium antibodies.
The prevalence of both anti-S. mansoni and anti-S. haematobium antibodies was more than three times higher than the prevalence of infection estimated by egg detection under a microscope. Using quadruplicate Kato-Katz as the reference standard for the diagnosis of S. mansoni infection, the sensitivity, negative predictive value (NPV), and positive predictive value (PPV) of the SmCTF-RDT was 75.0%, 84.2% and 22.5%, respectively. When two urine filtrations were considered as the reference standard for the diagnosis of S. haematobium infection, the sensitivity, NPV and PPV of SmCTF-RDT was 66.7%, 94.9% and 5.1%, respectively. The specificity of SmCTF-RDT, when using egg-detection as the reference standard, was estimated to be 34.4%. This low specificity may be a reflection of the relative insensitivity of the direct diagnostic approaches using microscopy.
The SmCTF-RDT is at least as sensitive as duplicate Kato-Katz and a single urine filtration for detection of S. mansoni and S. haematobium, respectively. Further investigations into the specificity of the test for anti-schistosome antibodies are necessary, but our results suggest that it may be a useful tool for mapping the prevalence of anti-schistosome antibodies in a given population pending intervention.
Schistosomiasis; Schistosoma haematobium; Schistosoma mansoni; Diagnosis; Antibodies; Cercariae; Sensitivity; Specificity; Positive predictive value; Negative predictive value; Côte d’Ivoire
Despite the continuous efforts to improve the quality of life of Orang Asli (Aborigines) communities, these communities are still plagued with a wide range of health problems including parasitic infections. The first part of this study aimed at determining the prevalence of soil-transmitted helminth (STH) infections and identifying their associated factors among rural Orang Asli children.
A cross-sectional study was carried out among 484 Orang Asli children aged ≤ 15 years (235 females and 249 males) belonging to 215 households from 13 villages in Lipis district, Pahang, Malaysia. Faecal samples were collected and examined by using formalin-ether sedimentation, Kato Katz and Harada Mori techniques. Demographic, socioeconomic, environmental and behavioural information were collected by using a pre-tested questionnaire.
Overall, 78.1% of the children were found to be infected with one or more STH species. The prevalence of trichuriasis, ascariasis and hookworm infections were 71.7%, 37.4% and 17.6%, respectively. Almost all, three quarters and one fifth of trichuriasis, ascariasis and hookworm infections, respectively, were of moderate-to-heavy intensities. Multiple logistic regression analysis showed that age of ≥ 6 years (school-age), using unsafe water supply as a source for drinking water, absence of a toilet in the house, large family size (≥ 7 members), not washing hands before eating, and not washing hands after defecation were the key factors significantly associated with STH among these children.
This study reveals an alarmingly high prevalence of STH among Orang Asli children and clearly brings out an urgent need to implement school-based de-worming programmes and other control measures like providing a proper sanitation, as well as a treated drinking water supply and proper health education regarding good personal hygiene practices. Such an integrated control program will help significantly in reducing the prevalence and intensity of STH in Orang Asli communities.
Soil-transmitted helminths; Ascaris; Trichuris; Hookworm; Orang Asli; Malaysia
In the first part of this study, we investigated the prevalence and associated key factors of soil-transmitted helminth (STH) infections among Orang Asli children in rural Malaysia; an alarming high prevalence and five key factors significantly associated with infections were reported. Part 2 of this study aims to evaluate the knowledge, attitude and practices (KAP) on STH infections among Orang Asli in Peninsular Malaysia.
A cross-sectional study was carried out among 215 households from 13 villages in Lipis district, Pahang, Malaysia. Demographic and socioeconomic information of the participants and their KAP on STH were collected by using a pre-tested questionnaire.
Overall, 61.4% of the participants had prior knowledge about intestinal helminths with a lack of knowledge on the transmission (28.8%), signs and symptoms (29.3%) as well as the prevention (16.3%). Half of the respondents considered STH as harmful, while their practices to prevent infections were still inadequate. Significant associations between the KAP and age, gender, educational and employment status, family size, and household monthly income were reported. Moreover, significantly lower prevalence of STH infections was reported among children of respondents who wear shoes/slippers when outside the house (72.8%; 95% CI= 62.6, 80.5 vs 87.0%; 95% CI= 81.4, 91.1), wash their hands before eating (32.4%; 95% CI= 24.3, 42.2 vs 51.4%; 95% CI= 44.7, 60.1), and wash their hands after defecation (47.8%; 95% CI= 35.7, 57.1 vs 69.2%; 95% CI= 63.7, 78.7) as compared to their counterparts. Multiple logistic regression analysis indicated that the educational level of the respondents was the most important factor significantly associated with the KAP on STH among this population.
This study reveals inadequate knowledge, attitude and practices on STH infections among Orang Asli in rural Malaysia. Hence, there is a great need for a proper health education programme and community mobilisation to enhance prevention and instil better knowledge on STH transmission and prevention. This is crucial for an effective and sustainable STH control programme to save the lives and future of the most vulnerable children in rural Malaysia.
Knowledge; Attitude; Practice; Soil-transmitted helminths; Malaysia
The brain is the most commonly affected organ during Neospora caninum infection but the mechanisms utilized by this protozoan parasite for traversal of the blood–brain barrier (BBB) are not yet understood. Herein, we investigate the cellular pathogenicity of N. caninum infection on bioenergetics of human brain microvascular endothelial cells (HBMECs), a fundamental component of the BBB.
We tracked the growth kinetics of N. caninum in HBMECs. Focusing on cell bioenergetics, oxygen consumption rate (OCR) was determined using Clark electrode system and mitochondrial membrane potential (ΔΨm) was evaluated using DePsipher staining by fluorescence microscopy in the presence and absence of infection.
HBMECs provided a receptive environment for parasite proliferation. N. caninum tachyzoites were able to invade and replicate within HBMECs without significantly altering cell proliferation rate, as measured with the MTT assay, up to 24 hr post infection (pi). The oxygen consumption rate (OCR) was significantly inhibited (p < 0.001) by 10 mM glucose [from −2.26±0.23 to −0.6±0.21 nmol 106 cell min-1 and from −0.29±0.09 to −0.16±0.1 nmol 106 cell min-1 for uninfected HBMECs and free N. Caninum tachyzoites, respectively]. After normalization for DNA content the basal OCR did not differ between two host cell types: HBMECs and K562. The OCR of HBMECs was significantly elevated 24 hr pi in the absence of substrate, in 10 mM glucose and in the presence of a tetramethyl-p-phenylenediamine (TMPD)/ascorbate redox shuttle. Although quantitatively similar results were observed for uninfected K562 cells, there was no effect on their OCR 24 hr pi with N. caninum under any of the above substrate conditions. 6mM azide abolished OCR in all situations. Mitochondrial staining with DePsipher indicated no change in their membrane potential (Δψm) up to 24 hr pi.
N. caninum is able to grow in HBMECs without markedly disrupting their normal proliferation or mitochondrial integrity. However, it is associated with an increase in infected cell respiration. Whether this increase reflects numeric addition of the parasites own respiration or results from an additional energy demand upon the host cell remains to be elucidated.
Adaptation; Blood–brain barrier; Trade-off; Mitochondrial respiratory chain; Oxygen consumption; Neospora caninum; Neuropathy
Lyme borreliosis is a tick-borne disease caused by Borrelia burgdorferi sensu lato. The variety of characteristic and non-specific clinical manifestations is partially explained by its genetic diversity. We investigated the ability of B. burgdorferi sl isolates to cause erythema migrans.
The genetic constellation of isolates from ticks was compared to isolates found in erythema migrans. PCR and sequence analysis was performed on the plasmid-encoded ospC and the chromosomal 5S-23S rDNA spacer region (IGS).
Seven different B. burgdorferi sl genospecies were identified in 152 borrelia isolates from ticks and erythema migrans biopsies. B afzelii (51%) and B. garinii (27%) were the most common in ticks. From the 44 sequences obtained from erythema migrans samples 42 were B. afzelii, one B. garinii and one B. bavariensis. Significant associations with erythema migrans formation were found for four IGS and two ospC types. Five from 45 ospC types were associated with more than one genospecies.
B. burgdorferi sl isolates differ in their propensity to cause erythema migrans. These differences were also found within genospecies. In other words, although B. afzelii was mostly associated with erythema migrans, some B. afzelii isolates had a low ability to cause erythema migrans. Our data further support the occurrence of plasmid exchange between borrelia genospecies under natural conditions.
Lyme borreliosis; Erythema migrans; Molecular epidemiology; Virulence marker
Adult and larval mosquitoes regulate food digestion in their gut with trypsin modulating oostatic factor (TMOF), a decapeptide hormone synthesized by the ovaries and the neuroendocrine system. TMOF is currently being developed as a mosquitocide, however, delivery of the peptide to the mosquito remains a significant challenge. Entomopathogenic fungi offer a means for targeting mosquitoes with TMOF.
The efficacy of wild type and transgenic Beauveria bassiana strains expressing Aedes aegypti TMOF (Bb-Aa1) were evaluated against larvae and sugar- and blood-fed adult Anopheles gambiae mosquitoes using insect bioassays. Bb-Aa1 displayed increased virulence against larvae, and sugar and blood fed adult A. gambiae when compared to the wild type parent strain. Median lethal dose (LD50) values decreased by ~20% for larvae, and ~40% for both sugar and blood-fed mosquitoes using Bb-Aa1 relative to the wild type parent. Median lethal time (LT50) values were lower for blood-fed compared to sugar-fed mosquitoes in infections with both wild type and Bb-Aa1. However, infection using Bb-Aa1 resulted in 15% to 25% reduction in LT50 values for sugar- and blood fed mosquitoes, and ~27% for larvae, respectively, relative to the wild type parent. In addition, infection with Bb-Aa1 resulted in a dramatic reduction in fecundity of the target mosquitoes.
B. bassiana expressing Ae. aegypti TMOF exhibited increased virulence against A. gambiae compared to the wild type strain. These data expand the range and utility of entomopathogenic fungi expressing mosquito-specific molecules to improve their biological control activities against mosquito vectors of disease.
Trypsin modulating oostatic factor; Biological control; Beauveria bassiana; Anopheles gambiae
When Plasmodium vivax tertian malaria was prevalent in The Netherlands, the use of therapeutic malaria for the treatment of neurosyphilis patients presented an opportunity for biological studies of the parasite’s behaviour, in healthy volunteers. One unexplained phenomenon was the long latency between natural exposure to a single infected mosquito and the appearance of clinical signs (average 8 months). Dutch studies with volunteers and syphilis patients, suggested that hundreds of sporozoites transmitted by several mosquito bites were enough to provoke an early attack, known from tropical vivax-malaria. Sporozoites appeared to be programmed either to delay their pre-erythrocytic development or to proceed to an early attack within three weeks. The number of infectious bites also determined the relapse rate and the number of relapses after a primary attack. Analyses of primary cases and relapses from the previous year were used to predict the incidence for the next year. These historic findings fit well with recent studies on genotyping of blood stages during primary attacks and relapses. External factors (i.e. the milieu inside the human host) may trigger hypnozoites to reactivate, but predetermined periods of latency should also be considered.
Plasmodium vivax; Experimental infection; Neurosyphilis; Long latency; Relapse
Metal uptake and accumulation in fish parasites largely depends on the parasite group with acanthocephalans showing the highest accumulation rates. Additionally, developmental stage (larvae or adult) as well as parasite location in the host are suggested to be decisive factors for metal bioconcentration in parasites. By using barbel (Barbus barbus) simultaneously infected with nematode larvae in the body cavity and adult acanthocephalans in the intestine, the relative importance of all of these factors was compared in the same host.
Eleven elements Arsenic (As), Cadmium (Cd), Cobalt (Co), Copper (Cu), Iron (Fe), Manganese (Mn), Lead (Pb), Selenium (Se), Tin (Sn), Vanadium (V) and Zinc (Zn) were analyzed in barbel tissues (muscle, intestine, liver) as well as in their acanthocephalan parasites Pomphorhynchus laevis and the larval nematode Eustrongylides sp. (L4) using inductively coupled plasma mass spectrometry (ICP-MS).
Nine elements were detected in significantly higher levels in the parasites compared to host tissues. The element composition among parasites was found to be strongly dependent on parasite taxa/developmental stage and localization within the host. Intestinal acanthocephalans accumulated mainly toxic elements (As, Cd, Pb), whereas the intraperitoneal nematodes bioconcentrated essential elements (Co, Cu, Fe, Se, Zn).
Our results suggest that in addition to acanthocephalans, nematodes such as Eustrongylides sp. can also be applied as bioindicators for metal pollution. Using both parasite taxa simultaneously levels of a wide variety of elements (essential and non essential) can easily be obtained. Therefore this host-parasite system can be suggested as an appropriate tool for future metal monitoring studies, if double infected fish hosts are available.
Pomphorhynchus laevis; Eustrongylides sp.; Heavy metals; Pollution; Bioindication