Growth and development of Gnathostoma spinigerum (Nematoda: Gnathostomatidae) larvae in Mesocyclops aspericornis (Cyclopoida: Cyclopidae)

<p>Abstract</p> <p>Background</p> <p><it>Gnathostoma spinigerum </it>larva is pathogenic, causing gnathostomiasis in humans and certain animals, and is prevalent mainly in Asia. Growth and development of <it>Gnathostoma spinigerum </it>larvae in the cyclopoid copepod <it>Mesocyclops aspericornis</it>, the first intermediate host, were examined.</p> <p>Results</p> <p>When newly hatched, ensheathed second-stage larvae (L2) were ingested by <it>M. aspericornis</it>, they immediately appeared exsheathed in the stomach of <it>M. aspericornis</it>. They then penetrated the stomach wall and entered the body cavity, where they immediately metamorphosed to a stunted form with the body length/width ratio equal to the early third-stage larvae (EL3) up to 2 h after being ingested. During metamorphosis, the anterior spine-like structure of L2 transformed into unequal transparent lips. The larvae moulted into EL3 in the body cavity of the copepod at around day 5-7 post-infection. Minute cuticular striations were seen on the whole body, with prominent single-pointed spines on the anterior part of the body. The head bulb had four rows of hooklets and two lateral trilobed lips. The size of EL3 in copepods continuously increased towards day 12 and showed a negative correlation to their density per copepod (R = -0.881, <it>P </it>< 0.05 for body length, and R = -0.906, <it>P </it>< 0.05 for body width).</p> <p>Conclusions</p> <p>The results revealed for the first time that <it>M. aspericornis</it>, one of the most abundant freshwater copepods in Thailand, is a suitable first intermediate host for <it>G. spinigerum</it>. High susceptibility of <it>M. aspericornis </it>suggests its importance for the maintenance of the life cycle of <it>G. spinigerum </it>in Thailand.</p

Development of a PCR assay and pyrosequencing for identification of important human fish-borne trematodes and its potential use for detection in fecal specimens

BACKGROUND: Small liver and minute intestinal flukes are highly prevalent in Southeast Asia. Definitive diagnosis of parasite infection is usually achieved parasitologically by finding the fluke eggs in feces. However, their eggs are difficult to differentiate morphologically in fecal samples, even for experienced technicians. The present study developed a PCR assay coupled with DNA pyrosequencing for identification of the fish-borne trematodes (FBT), Opisthorchis viverrini, Clonorchis sinensis, Haplorchis taichui, H. pumilio and Stellantchasmus falcatus, and to evaluate potential detection in fecal specimens, and identification and differentiation of cercarial and metacercarial stages. METHODS: Primers targeting the partial 28S large subunit ribosomal RNA gene were designed and about 46–47 nucleotides were selected as the target region for species identification by a PCR assay coupled with a pyrosequencing technique. RESULTS: The nucleotide variations at 24 positions, which is sufficient for the identification of the five species of FBT were selected. The method could identify O. viverrini and C. sinensis eggs in feces, cercarial and metacercarial stages of O. viverrini, and metacercarial stage of H. pumilio and H. taichui. The detection limit was as little as a single O. viverrini or C. sinensis egg artificially inoculated in 100 mg of non-infected fecal sample (equivalent to 10 eggs per gram), indicating highly sensitivity. The method was found to be superior to the traditional microscopy method and was more rapid than Sanger DNA sequencing. CONCLUSIONS: DNA pyrosequencing-based identification is a valuable tool for differentiating O. viverrini and other Opisthorchis-like eggs, and can be applied to epidemiological studies and for molecular taxonomic investigation of FBT in endemic areas

The mitochondrial genome of Angiostrongylus mackerrasae as a basis for molecular, epidemiological and population genetic studies

BACKGROUND: Angiostrongylus mackerrasae is a metastrongyloid nematode endemic to Australia, where it infects the native bush rat, Rattus fuscipes. This lungworm has an identical life cycle to that of Angiostrongylus cantonensis, a leading cause of eosinophilic meningitis in humans. The ability of A. mackerrasae to infect non-rodent hosts, specifically the black flying fox, raises concerns as to its zoonotic potential. To date, data on the taxonomy, epidemiology and population genetics of A. mackerrasae are unknown. Here, we describe the mitochondrial (mt) genome of A. mackerrasae with the aim of starting to address these knowledge gaps. METHODS: The complete mitochondrial (mt) genome of A. mackerrasae was amplified from a single morphologically identified adult worm, by long-PCR in two overlapping amplicons (8 kb and 10 kb). The amplicons were sequenced using the MiSeq Illumina platform and annotated using an in-house pipeline. Amino acid sequences inferred from individual protein coding genes of the mt genomes were concatenated and then subjected to phylogenetic analysis using Bayesian inference. RESULTS: The mt genome of A. mackerrasae is 13,640 bp in size and contains 12 protein coding genes (cox1-3, nad1-6, nad4L, atp6 and cob), and two ribosomal RNA (rRNA) and 22 transfer RNA (tRNA) genes. CONCLUSIONS: The mt genome of A. mackerrasae has similar characteristics to those of other Angiostrongylus species. Sequence comparisons reveal that A. mackerrasae is closely related to A. cantonensis and the two sibling species may have recently diverged compared with all other species in the genus with a highly specific host selection. This mt genome will provide a source of genetic markers for explorations of the epidemiology, biology and population genetics of A. mackerrasae

Specificity of immunoblotting analyses in eosinophilic meningitis

Angiostrongylus cantonensis and Gnathostoma spinigerum are the two most common causative parasites of eosinophilic meningitis (EOM). Serological tests are helpful tools for confirming the identity of the pathogen. Recent reports determined the specificity of such tests by using normal healthy controls. There have been limited studies done to rule out the cross-reactivity between these two causative parasites of EOM. This study aims to assess the specificity of the serological test in EOM by using each condition as a control for the other. Thirty-three patients with a diagnosis of EOM were enrolled. Sera from 22 patients with a positive 29-kDa antigenic diagnostic band of A. cantonensis were tested for the 21 and 24-kDa antigenic bands of G. spinigerum. Similarly, sera of 11 gnathostomiasis patients were tested for the 29-kDa diagnostic band for A. cantonensis. Only one patient in the angiostrongyliasis group had a positive result for the 21 and 24-kDa antigenic bands of G. spinigerum, while no gnathostomiasis patients showed a positive result for the 29-kDa antigenic band of A. cantonensis. The specificity of the 21 and 24-kDa antigenic bands for gnathostomiasis and the 29-kDa antigenic band for A. cantonensis was 95.5% and 100%, respectively. The antigenic bands for the diagnosis of gnathostomiasis and angiostrongyliasis in EOM were highly specific

Localized instabilities of the Wigner equation as a model for the emergence of Rogue Waves

In this paper, we model Rogue Waves as localized instabilities emerging from homogeneous and stationary background wavefields, under NLS dynamics. This is achieved in two steps: given any background Fourier spectrum P(k), we use the Wigner transform and Penrose’s method to recover spatially periodic unstable modes, which we call unstable Penrose modes. These can be seen as generalized Benjamin–Feir modes, and their parameters are obtained by resolving the Penrose condition, a system of nonlinear equations involving P(k). Moreover, we show how the superposition of unstable Penrose modes can result in the appearance of localized unstable modes. By interpreting the appearance of an unstable mode localized in an area not larger than a reference wavelength λ0 as the emergence of a Rogue Wave, a criterion for the emergence of Rogue Waves is formulated. Our methodology is applied to δ spectra, where the standard Benjamin–Feir instability is recovered, and to more general spectra. In that context, we present a scheme for the numerical resolution of the Penrose condition and estimate the sharpest possible localization of unstable modes. Keywords: Rogue Waves; Wigner equation; Nonlinear Schrodinger equation; Penrose modes; Penrose conditio

Low Efficacy of Single-Dose Albendazole and Mebendazole against Hookworm and Effect on Concomitant Helminth Infection in Lao PDR

Parasitic worms remain a public health problem in developing countries. Regular deworming with the drugs albendazole and mebendazole is the current global control strategy. We assessed the efficacies of a single tablet of albendazole (400 mg) and mebendazole (500 mg) against hookworm in children of southern Lao PDR. From each child, two stool samples were examined for the presence and number of hookworm eggs. Two hundred children were found to be infected. They were randomly assigned to albendazole (n = 100) or mebendazole (n = 100) treatment. Three weeks later, another two stool samples were analyzed for hookworm eggs. Thirty-two children who were given albendazole had no hookworm eggs anymore in their stool, while only 15 children who received mebendazole were found egg-negative. The total number of hookworm eggs was reduced by 85.3% in the albendazole and 74.5% in the mebendazole group. About one third of the children who were co-infected with the Asian liver fluke Opisthorchis viverrini were cleared from this infection following albendazole treatment and about one forth in the mebendazole group. Concluding, both albendazole and mebendazole showed disappointingly low cure rates against hookworm, with albendazole performing somewhat better. The effect of these two drugs against O. viverrini should be studied in greater detail

Is a HIV vaccine a viable option and at what price? An economic evaluation of adding HIV vaccination into existing prevention programs in Thailand

<p>Abstract</p> <p>Background</p> <p>This study aims to determine the maximum price at which HIV vaccination is cost-effective in the Thai healthcare setting. It also aims to identify the relative importance of vaccine characteristics and risk behavior changes among vaccine recipients to determine how they affect this cost-effectiveness.</p> <p>Methods</p> <p>A semi-Markov model was developed to estimate the costs and health outcomes of HIV prevention programs combined with HIV vaccination in comparison to the existing HIV prevention programs without vaccination. The estimation was based on a lifetime horizon period (99 years) and used the government perspective. The analysis focused on both the general population and specific high-risk population groups. The maximum price of cost-effective vaccination was defined by using threshold analysis; one-way and probabilistic sensitivity analyses were performed. The study employed an expected value of perfect information (EVPI) analysis to determine the relative importance of parameters and to prioritize future studies.</p> <p>Results</p> <p>The most expensive HIV vaccination which is cost-effective when given to the general population was 12,000 Thai baht (US$1 = 34 Thai baht in 2009). This vaccination came with 70% vaccine efficacy and lifetime protection as long as risk behavior was unchanged post-vaccination. The vaccine would be considered cost-ineffective at any price if it demonstrated low efficacy (30%) and if post-vaccination risk behavior increased by 10% or more, especially among the high-risk population groups. The incremental cost-effectiveness ratios were the most sensitive to change in post-vaccination risk behavior, followed by vaccine efficacy and duration of protection. The EVPI indicated the need to quantify vaccine efficacy, changed post-vaccination risk behavior, and the costs of vaccination programs.</p> <p>Conclusions</p> <p>The approach used in this study differentiated it from other economic evaluations and can be applied for the economic evaluation of other health interventions not available in healthcare systems. This study is important not only for researchers conducting future HIV vaccine research but also for policy decision makers who, in the future, will consider vaccine adoption.</p