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Structural basis for the high specificity of a <i>Trypanosoma congolense</i> immunoassay targeting glycosomal aldolase

15 September 2017 - 9:00pm

by Joar Pinto, Steven Odongo, Felicity Lee, Vaiva Gaspariunaite, Serge Muyldermans, Stefan Magez, Yann G.-J. Sterckx

Background

Animal African trypanosomosis (AAT) is a neglected tropical disease which imposes a heavy burden on the livestock industry in Sub-Saharan Africa. Its causative agents are Trypanosoma parasites, with T. congolense and T. vivax being responsible for the majority of the cases. Recently, we identified a Nanobody (Nb474) that was employed to develop a homologous sandwich ELISA targeting T. congolense fructose-1,6-bisphosphate aldolase (TcoALD). Despite the high sequence identity between trypanosomatid aldolases, the Nb474-based immunoassay is highly specific for T. congolense detection. The results presented in this paper yield insights into the molecular principles underlying the assay’s high specificity.

Methodology/Principal findings

The structure of the Nb474-TcoALD complex was determined via X-ray crystallography. Together with analytical gel filtration, the structure reveals that a single TcoALD tetramer contains four binding sites for Nb474. Through a comparison with the crystal structures of two other trypanosomatid aldolases, TcoALD residues Ala77 and Leu106 were identified as hot spots for specificity. Via ELISA and surface plasmon resonance (SPR), we demonstrate that mutation of these residues does not abolish TcoALD recognition by Nb474, but does lead to a lack of detection in the Nb474-based homologous sandwich immunoassay.

Conclusions/Significance

The results show that the high specificity of the Nb474-based immunoassay is not determined by the initial recognition event between Nb474 and TcoALD, but rather by its homologous sandwich design. This (i) provides insights into the optimal set-up of the assay, (ii) may be of great significance for field applications as it could explain the potential detection escape of certain T. congolense strains, and (iii) may be of general interest to those developing similar assays.

Scrambled eggs: A highly sensitive molecular diagnostic workflow for <i>Fasciola</i> species specific detection from faecal samples

15 September 2017 - 9:00pm

by Nichola Eliza Davies Calvani, Peter Andrew Windsor, Russell David Bush, Jan Šlapeta

Background

Fasciolosis, due to Fasciola hepatica and Fasciola gigantica, is a re-emerging zoonotic parasitic disease of worldwide importance. Human and animal infections are commonly diagnosed by the traditional sedimentation and faecal egg-counting technique. However, this technique is time-consuming and prone to sensitivity errors when a large number of samples must be processed or if the operator lacks sufficient experience. Additionally, diagnosis can only be made once the 12-week pre-patent period has passed. Recently, a commercially available coprological antigen ELISA has enabled detection of F. hepatica prior to the completion of the pre-patent period, providing earlier diagnosis and increased throughput, although species differentiation is not possible in areas of parasite sympatry. Real-time PCR offers the combined benefits of highly sensitive species differentiation for medium to large sample sizes. However, no molecular diagnostic workflow currently exists for the identification of Fasciola spp. in faecal samples.

Methodology/Principal findings

A new molecular diagnostic workflow for the highly-sensitive detection and quantification of Fasciola spp. in faecal samples was developed. The technique involves sedimenting and pelleting the samples prior to DNA isolation in order to concentrate the eggs, followed by disruption by bead-beating in a benchtop homogeniser to ensure access to DNA. Although both the new molecular workflow and the traditional sedimentation technique were sensitive and specific, the new molecular workflow enabled faster sample throughput in medium to large epidemiological studies, and provided the additional benefit of speciation. Further, good correlation (R2 = 0.74–0.76) was observed between the real-time PCR values and the faecal egg count (FEC) using the new molecular workflow for all herds and sampling periods. Finally, no effect of storage in 70% ethanol was detected on sedimentation and DNA isolation outcomes; enabling transport of samples from endemic to non-endemic countries without the requirement of a complete cold chain. The commercially-available ELISA displayed poorer sensitivity, even after adjustment of the positive threshold (65–88%), compared to the sensitivity (91–100%) of the new molecular diagnostic workflow.

Conclusions/Significance

Species-specific assays for sensitive detection of Fasciola spp. enable ante-mortem diagnosis in both human and animal settings. This includes Southeast Asia where there are potentially many undocumented human cases and where post-mortem examination of production animals can be difficult. The new molecular workflow provides a sensitive and quantitative diagnostic approach for the rapid testing of medium to large sample sizes, potentially superseding the traditional sedimentation and FEC technique and enabling surveillance programs in locations where animal and human health funding is limited.

Trends and correlates of cystic echinococcosis in Chile: 2001–2012

15 September 2017 - 9:00pm

by Soledad Colombe, Eri Togami, Fkadu Gelaw, Marina Antillon, Rodrigo Fuentes, Daniel Martin Weinberger

Echinococcosis is a neglected zoonotic disease affecting over 1 million people worldwide at any given time. It is the leading cause of hospital admissions for parasitic diseases in Chile. We conducted a retrospective investigation of hospitalized cases to describe the epidemiological trends of echinococcosis in Chile. We also examined the potential environmental risk factors for echinococcosis hospitalization rates. Through nation-wide hospital discharge data, a total of 11,516 hospitalized patients with cystic echinococcosis were identified between January 2001 and December 2012. The mean age of hospitalization was 40 years, with notable gender difference in pediatric patients. The hospitalization rate was found to be overall steadily decreasing from 2001 (7.02 per 100,000) to 2012 (4.53 per 100,000) with a 5% decrease per year (rate ratio = 0.95 [95% CI: 0.94, 0.96]). The hospitalization rate was higher in the south of Chile compared to the north. Goat density and intermediate precipitation were found to be significantly positively associated with the hospitalization rate while annual average temperature was found to be significantly negatively associated with the hospitalization rate. Findings of this study indicate that echinococcosis is still an important public health burden in Chile related to interaction with livestock and climate. Efforts should be placed on targeted prevention measures for farmers and raising awareness of echinococcosis among health care workers.

The single cyclic nucleotide-specific phosphodiesterase of the intestinal parasite <i>Giardia lamblia</i> represents a potential drug target

15 September 2017 - 9:00pm

by Stefan Kunz, Vreni Balmer, Geert Jan Sterk, Michael P. Pollastri, Rob Leurs, Norbert Müller, Andrew Hemphill, Cornelia Spycher

Background

Giardiasis is an intestinal infection correlated with poverty and poor drinking water quality, and treatment options are limited. According to the Center for Disease Control and Prevention, Giardia infections afflict nearly 33% of people in developing countries, and 2% of the adult population in the developed world. This study describes the single cyclic nucleotide-specific phosphodiesterase (PDE) of G. lamblia and assesses PDE inhibitors as a new generation of anti-giardial drugs.

Methods

An extensive search of the Giardia genome database identified a single gene coding for a class I PDE, GlPDE. The predicted protein sequence was analyzed in-silico to characterize its domain structure and catalytic domain. Enzymatic activity of GlPDE was established by complementation of a PDE-deficient Saccharomyces cerevisiae strain, and enzyme kinetics were characterized in soluble yeast lysates. The potency of known PDE inhibitors was tested against the activity of recombinant GlPDE expressed in yeast and against proliferating Giardia trophozoites. Finally, the localization of epitope-tagged and ectopically expressed GlPDE in Giardia cells was investigated.

Results

Giardia encodes a class I PDE. Catalytically important residues are fully conserved between GlPDE and human PDEs, but sequence differences between their catalytic domains suggest that designing Giardia-specific inhibitors is feasible. Recombinant GlPDE hydrolyzes cAMP with a Km of 408 μM, and cGMP is not accepted as a substrate. A number of drugs exhibit a high degree of correlation between their potency against the recombinant enzyme and their inhibition of trophozoite proliferation in culture. Epitope-tagged GlPDE localizes as dots in a pattern reminiscent of mitosomes and to the perinuclear region in Giardia.

Conclusions

Our data strongly suggest that inhibition of G. lamblia PDE activity leads to a profound inhibition of parasite proliferation and that GlPDE is a promising target for developing novel anti-giardial drugs.

Phylogeographic, genomic, and meropenem susceptibility analysis of <i>Burkholderia ubonensis</i>

14 September 2017 - 9:00pm

by Erin P. Price, Derek S. Sarovich, Jessica R. Webb, Carina M. Hall, Sierra A. Jaramillo, Jason W. Sahl, Mirjam Kaestli, Mark Mayo, Glenda Harrington, Anthony L. Baker, Lindsay C. Sidak-Loftis, Erik W. Settles, Madeline Lummis, James M. Schupp, John D. Gillece, Apichai Tuanyok, Jeffrey Warner, Joseph D. Busch, Paul Keim, Bart J. Currie, David M. Wagner

The bacterium Burkholderia ubonensis is commonly co-isolated from environmental specimens harbouring the melioidosis pathogen, Burkholderia pseudomallei. B. ubonensis has been reported in northern Australia and Thailand but not North America, suggesting similar geographic distribution to B. pseudomallei. Unlike most other Burkholderia cepacia complex (Bcc) species, B. ubonensis is considered non-pathogenic, although its virulence potential has not been tested. Antibiotic resistance in B. ubonensis, particularly towards drugs used to treat the most severe B. pseudomallei infections, has also been poorly characterised. This study examined the population biology of B. ubonensis, and includes the first reported isolates from the Caribbean. Phylogenomic analysis of 264 B. ubonensis genomes identified distinct clades that corresponded with geographic origin, similar to B. pseudomallei. A small proportion (4%) of strains lacked the 920kb chromosome III replicon, with discordance of presence/absence amongst genetically highly related strains, demonstrating that the third chromosome of B. ubonensis, like other Bcc species, probably encodes for a nonessential pC3 megaplasmid. Multilocus sequence typing using the B. pseudomallei scheme revealed that one-third of strains lack the “housekeeping” narK locus. In comparison, all strains could be genotyped using the Bcc scheme. Several strains possessed high-level meropenem resistance (≥32 μg/mL), a concern due to potential transmission of this phenotype to B. pseudomallei. In silico analysis uncovered a high degree of heterogeneity among the lipopolysaccharide O-antigen cluster loci, with at least 35 different variants identified. Finally, we show that Asian B. ubonensis isolate RF23-BP41 is avirulent in the BALB/c mouse model via a subcutaneous route of infection. Our results provide several new insights into the biology of this understudied species.

Host outdoor exposure variability affects the transmission and spread of Zika virus: Insights for epidemic control

14 September 2017 - 9:00pm

by Marco Ajelli, Imelda K. Moise, Tricia Caroline S. G. Hutchings, Scott C. Brown, Naresh Kumar, Neil F. Johnson, John C. Beier

Background

Zika virus transmission dynamics in urban environments follow a complex spatiotemporal pattern that appears unpredictable and barely related to high mosquito density areas. In this context, human activity patterns likely have a major role in Zika transmission dynamics. This paper examines the effect of host variability in the amount of time spent outdoors on Zika epidemiology in an urban environment.

Methodology/Principal findings

First, we performed a survey on time spent outdoors by residents of Miami-Dade County, Florida. Second, we analyzed both the survey and previously published national data on outdoors time in the U.S. to provide estimates of the distribution of the time spent outdoors. Third, we performed a computational modeling evaluation of Zika transmission dynamics, based on the time spent outdoors by each person. Our analysis reveals a strong heterogeneity of the host population in terms of time spent outdoors–data are well captured by skewed gamma distributions. Our model-based evaluation shows that in a heterogeneous population, Zika would cause a lower number of infections than in a more homogenous host population (up to 4-fold differences), but, at the same time, the epidemic would spread much faster. We estimated that in highly heterogeneous host populations the timing of the implementation of vector control measures is the major factor for limiting the number of Zika infections.

Conclusions/Significance

Our findings highlight the need of considering host variability in exposure time for managing mosquito-borne infections and call for the revision of the triggers for vector control strategies, which should integrate mosquito density data and human outdoor activity patterns in specific areas.

Access to benznidazole for Chagas disease in the United States—Cautious optimism?

14 September 2017 - 9:00pm

by Jonathan D. Alpern, Rogelio Lopez-Velez, William M. Stauffer

Drugs for neglected tropical diseases (NTD) are being excessively priced in the United States. Benznidazole, the first-line drug for Chagas disease, may become approved by the Food and Drug Administration (FDA) and manufactured by a private company in the US, thus placing it at risk of similar pricing. Chagas disease is an NTD caused by Trypanosoma cruzi; it is endemic to Latin America, infecting 8 million individuals. Human migration has changed the epidemiology causing nonendemic countries to face increased challenges in diagnosing and managing patients with Chagas disease. Only 2 drugs exist with proven efficacy: benznidazole and nifurtimox. Benznidazole has historically faced supply problems and drug shortages, limiting accessibility. In the US, it is currently only available under an investigational new drug (IND) protocol from the CDC and is provided free of charge to patients. However, 2 companies have stated that they intend to submit a New Drug Application (NDA) for FDA approval. Based on recent history of companies acquiring licensing rights for NTD drugs in the US with limited availability, it is likely that benznidazole will become excessively priced by the manufacturer—paradoxically making it less accessible. However, if the companies can be taken at their word, there may be reason for optimism.

Global health policy and neglected tropical diseases: Then, now, and in the years to come

14 September 2017 - 9:00pm

by Thomas Fürst, Paola Salari, Laura Monzón Llamas, Peter Steinmann, Christopher Fitzpatrick, Fabrizio Tediosi

Melioidosis in lower provincial Cambodia: A case series from a prospective study of sepsis in Takeo Province

13 September 2017 - 9:00pm

by Kevin L. Schully, Catherine M. Berjohn, Angela M. Prouty, Amitha Fitkariwala, Tin Som, Darith Sieng, Michael J. Gregory, Andrew Vaughn, Sim Kheng, Vantha Te, Christopher A. Duplessis, James V. Lawler, Danielle V. Clark

Melioidosis is a severe infectious disease caused by the gram-negative soil bacterium Burkholderia pseudomallei. Melioidosis is well known to be a major cause of morbidity and mortality in Southeast Asia, particularly in Thailand. However, melioidosis remains underreported in surrounding areas such as Cambodia. We report a case series of melioidosis in seven patients from Takeo Province, Cambodia. The patients, aged 24–65 years, were enrolled from May 2014 to May 2015 during a one year prospective study of sepsis at Takeo Provincial Hospital. They presented with fever, rigors, dyspnea, fatigue, diaphoresis, productive cough, and skin abscesses. Six of the seven patients were also hyponatremic. B. pseudomallei was cultured from the blood of six patients and the sputum of one patient. In this manuscript, we provide a detailed description of the clinical presentation, case management and laboratory confirmation of B. pseudomallei, as well as discuss the difficulties of identifying and treating melioidosis in low resource settings.

First insights in the variability of <i>Borrelia recurrentis</i> genomes

13 September 2017 - 9:00pm

by Durdica Marosevic, Gabriele Margos, Reinhard Wallich, Andreas Wieser, Andreas Sing, Volker Fingerle

Background

Borrelia recurrentis is the causative agent of louse-borne relapsing fever, endemic to the Horn of Africa. New attention was raised in Europe, with the highest number of cases (n = 45) reported among migrants in 2015 in Germany and sporadically from other European countries. So far only one genome was sequenced, hindering the development of specific molecular diagnostic and typing tools. Here we report on modified culture conditions for B. recurrentis and the intraspecies genome variability of six isolates isolated and cultured in different years in order to explore the possibility to identify new targets for typing and examine the molecular epidemiology of the pathogen.

Methodology/Principal findings

Two historical isolates from Ethiopia and four isolates from migrants from Somalia (n = 3) and Ethiopia (n = 1) obtained in 2015 were cultured in MPK-medium supplemented with 50% foetal calf serum. Whole DNA was sequenced using Illumina MiSeq technology and analysed using the CLC Genomics Workbench and SPAdes de novo assembler. Compared to the reference B. recurrentis A1 29–38 SNPs were identified in the genome distributed on the chromosome and plasmids. In addition to that, plasmids of differing length, compared to the available reference genome were identified.

Conclusions/Significance

The observed low genetic variability of B. recurrentis isolates is possibly due to the adaptation to a very conserved vector-host (louse-human) cycle, or influenced by the fastidious nature of the pathogen and their resistance to in vitro growth. Nevertheless, isolates obtained in 2015 were bearing the same chromosomal SNPs and could be distinguished from the historical isolates by means of whole genome sequencing, but not hitherto used typing methods. This is the first study examining the molecular epidemiology of B. recurrentis and provides the necessary background for the development of better diagnostic tools.

Clinical and epidemiologic characteristics of dengue and other etiologic agents among patients with acute febrile illness, Puerto Rico, 2012–2015

13 September 2017 - 9:00pm

by Kay M. Tomashek, Olga D. Lorenzi, Doris A. Andújar-Pérez, Brenda C. Torres-Velásquez, Elizabeth A. Hunsperger, Jorge Luis Munoz-Jordan, Janice Perez-Padilla, Aidsa Rivera, Gladys E. Gonzalez-Zeno, Tyler M. Sharp, Renee L. Galloway, Mindy Glass Elrod, Demetrius L. Mathis, M. Steven Oberste, W. Allan Nix, Elizabeth Henderson, Jennifer McQuiston, Joseph Singleton, Cecilia Kato, Carlos García Gubern, William Santiago-Rivera, Jesús Cruz-Correa, Robert Muns-Sosa, Juan D. Ortiz-Rivera, Gerson Jiménez, Ivonne E. Galarza, Kalanthe Horiuchi, Harold S. Margolis, Luisa I. Alvarado

Identifying etiologies of acute febrile illnesses (AFI) is challenging due to non-specific presentation and limited availability of diagnostics. Prospective AFI studies provide a methodology to describe the syndrome by age and etiology, findings that can be used to develop case definitions and multiplexed diagnostics to optimize management. We conducted a 3-year prospective AFI study in Puerto Rico. Patients with fever ≤7 days were offered enrollment, and clinical data and specimens were collected at enrollment and upon discharge or follow-up. Blood and oro-nasopharyngeal specimens were tested by RT-PCR and immunodiagnostic methods for infection with dengue viruses (DENV) 1–4, chikungunya virus (CHIKV), influenza A and B viruses (FLU A/B), 12 other respiratory viruses (ORV), enterovirus, Leptospira spp., and Burkholderia pseudomallei. Clinical presentation and laboratory findings of participants infected with DENV were compared to those infected with CHIKV, FLU A/B, and ORV. Clinical predictors of laboratory-positive dengue compared to all other AFI etiologies were determined by age and day post-illness onset (DPO) at presentation. Of 8,996 participants enrolled from May 7, 2012 through May 6, 2015, more than half (54.8%, 4,930) had a pathogen detected. Pathogens most frequently detected were CHIKV (1,635, 18.2%), FLU A/B (1,074, 11.9%), DENV 1–4 (970, 10.8%), and ORV (904, 10.3%). Participants with DENV infection presented later and a higher proportion were hospitalized than those with other diagnoses (46.7% versus 27.3% with ORV, 18.8% with FLU A/B, and 11.2% with CHIKV). Predictors of dengue in participants presenting <3 DPO included leukopenia, thrombocytopenia, headache, eye pain, nausea, and dizziness, while negative predictors were irritability and rhinorrhea. Predictors of dengue in participants presenting 3–5 DPO were leukopenia, thrombocytopenia, facial/neck erythema, nausea, eye pain, signs of poor circulation, and diarrhea; presence of rhinorrhea, cough, and red conjunctiva predicted non-dengue AFI. By enrolling febrile patients at clinical presentation, we identified unbiased predictors of laboratory-positive dengue as compared to other common causes of AFI. These findings can be used to assist in early identification of dengue patients, as well as direct anticipatory guidance and timely initiation of correct clinical management.

Prevalence of signs of trachoma, ocular <i>Chlamydia trachomatis</i> infection and antibodies to Pgp3 in residents of Kiritimati Island, Kiribati

12 September 2017 - 9:00pm

by Anaseini Cama, Andreas Müller, Raebwebwe Taoaba, Robert M. R. Butcher, Iakoba Itibita, Stephanie J. Migchelsen, Tokoriri Kiauea, Harry Pickering, Rebecca Willis, Chrissy H. Roberts, Ana Bakhtiari, Richard T. Le Mesurier, Neal D. E. Alexander, Diana L. Martin, Rabebe Tekeraoi, Anthony W. Solomon, for the Global Trachoma Mapping Project

Objective

In some Pacific Island countries, such as Solomon Islands and Fiji, active trachoma is common, but ocular Chlamydia trachomatis (Ct) infection and trachomatous trichiasis (TT) are rare. On Tarawa, the most populous Kiribati island, both the active trachoma sign “trachomatous inflammation—follicular” (TF) and TT are present at prevalences warranting intervention. We sought to estimate prevalences of TF, TT, ocular Ct infection, and anti-Ct antibodies on Kiritimati Island, Kiribati, to assess local relationships between these parameters, and to help determine the need for interventions against trachoma on Kiribati islands other than Tarawa.

Methods

As part of the Global Trachoma Mapping Project (GTMP), on Kiritimati, we examined 406 children aged 1–9 years for active trachoma. We collected conjunctival swabs (for droplet digital PCR against Ct plasmid targets) from 1–9-year-olds with active trachoma, and a systematic selection of 1–9-year-olds without active trachoma. We collected dried blood spots (for anti-Pgp3 ELISA) from all 1–9-year-old children. We also examined 416 adults aged ≥15 years for TT. Prevalence of TF and TT was adjusted for age (TF) or age and gender (TT) in five-year age bands.

Results

The age-adjusted prevalence of TF in 1–9-year-olds was 28% (95% confidence interval [CI]: 24–35). The age- and gender-adjusted prevalence of TT in those aged ≥15 years was 0.2% (95% CI: 0.1–0.3%). Twenty-six (13.5%) of 193 swabs from children without active trachoma, and 58 (49.2%) of 118 swabs from children with active trachoma were positive for Ct DNA. Two hundred and ten (53%) of 397 children had anti-Pgp3 antibodies. Both infection (p<0.0001) and seropositivity (p<0.0001) were strongly associated with active trachoma. In 1–9-year-olds, the prevalence of anti-Pgp3 antibodies rose steeply with age.

Conclusion

Trachoma presents a public health problem on Kiritimati, where the high prevalence of ocular Ct infection and rapid increase in seropositivity with age suggest intense Ct transmission amongst young children. Interventions are required here to prevent future blindness.

Effectiveness and economic assessment of routine larviciding for prevention of chikungunya and dengue in temperate urban settings in Europe

11 September 2017 - 9:00pm

by Giorgio Guzzetta, Filippo Trentini, Piero Poletti, Frederic Alexandre Baldacchino, Fabrizio Montarsi, Gioia Capelli, Annapaola Rizzoli, Roberto Rosà, Stefano Merler, Alessia Melegaro

In the last decades, several European countries where arboviral infections are not endemic have faced outbreaks of diseases such as chikungunya and dengue, initially introduced by infectious travellers from tropical endemic areas and then spread locally via mosquito bites. To keep in check the epidemiological risk, interventions targeted to control vector abundance can be implemented by local authorities. We assessed the epidemiological effectiveness and economic costs and benefits of routine larviciding in European towns with temperate climate, using a mathematical model of Aedes albopictus populations and viral transmission, calibrated on entomological surveillance data collected from ten municipalities in Northern Italy during 2014 and 2015.We found that routine larviciding of public catch basins can limit both the risk of autochthonous transmission and the size of potential epidemics. Ideal larvicide interventions should be timed in such a way to cover the month of July. Optimally timed larviciding can reduce locally transmitted cases of chikungunya by 20% - 33% for a single application (dengue: 18–22%) and up to 43% - 65% if treatment is repeated four times throughout the season (dengue: 31–51%). In larger municipalities (>35,000 inhabitants), the cost of comprehensive larviciding over the whole urban area overcomes potential health benefits related to preventing cases of disease, suggesting the adoption of more localized interventions. Small/medium sized towns with high mosquito abundance will likely have a positive cost-benefit balance. Involvement of private citizens in routine larviciding activities further reduces transmission risks but with disproportionate costs of intervention. International travels and the incidence of mosquito-borne diseases are increasing worldwide, exposing a growing number of European citizens to higher risks of potential outbreaks. Results from this study may support the planning and timing of interventions aimed to reduce the probability of autochthonous transmission as well as the nuisance for local populations living in temperate areas of Europe.

Induction of allopurinol resistance in <i>Leishmania infantum</i> isolated from dogs

11 September 2017 - 9:00pm

by Daniel Yasur-Landau, Charles L. Jaffe, Adi Doron-Faigenboim, Lior David, Gad Baneth

Resistance to allopurinol in zoonotic canine leishmaniasis has been recently shown to be associated with disease relapse in naturally-infected dogs. However, information regarding the formation of resistance and its dynamics is lacking. This study describes the successful in-vitro induction of allopurinol resistance in Leishmania infantum cultured under increasing drug pressure. Allopurinol susceptibility and growth rate of induced parasites were monitored over 23 weeks and parasite clones were tested at selected time points and compared to their parental lines, both as promastigotes and as amastigotes. Allopurinol resistance was formed in strains from two parasite stocks producing a 20-fold rise in IC50 along three distinct growth phases. In addition, characteristic differential clustering of single nucleotide polymorphisms (SNP) was found in drug sensitive and resistant parasite clones. Results confirm that genetic polymorphism, as well as clonal heterogeneity, contribute to in-vitro resistance to allopurinol, which is likely to occur in natural infection.

Knowledge and attitude towards Ebola and Marburg virus diseases in Uganda using quantitative and participatory epidemiology techniques

11 September 2017 - 9:00pm

by Luke Nyakarahuka, Eystein Skjerve, Daisy Nabadda, Doreen Chilolo Sitali, Chisoni Mumba, Frank N. Mwiine, Julius J. Lutwama, Stephen Balinandi, Trevor Shoemaker, Clovice Kankya

Background

Uganda has reported five (5) Ebola virus disease outbreaks and three (3) Marburg virus disease outbreaks from 2000 to 2016. Peoples’ knowledge and attitude towards Ebola and Marburg virus disease impact on control and prevention measures especially during outbreaks. We describe knowledge and attitude towards Ebola and Marburg virus outbreaks in two affected communities in Uganda to inform future outbreak responses and help in the design of health education and communication messages.

Methods

The study was a community survey done in Luweero, Ibanda and Kamwenge districts that have experienced outbreaks of Ebola and Marburg virus diseases. Quantitative data were collected using a structured questionnaire and triangulated with qualitative participatory epidemiology techniques to gain a communities’ knowledge and attitude towards Ebola and Marburg virus disease.

Results

Out of 740 respondents, 48.5% (359/740) were categorized as being knowledgeable about Ebola and Marburg virus diseases, whereas 60.5% (448/740) were having a positive attitude towards control and prevention of Ebola and Marburg virus diseases. The mean knowledge and attitude percentage scores were 54.3 (SD = 23.5, 95%CI = 52.6–56.0) and 69.9 (SD = 16.9, 95%CI = 68.9–71.1) respectively. People educated beyond primary school were more likely to be knowledgeable about Ebola and Marburg virus disease than those who did not attain any formal education (OR = 3.6, 95%CI = 2.1–6.1). Qualitative data revealed that communities describe Ebola and Marburg virus diseases as very severe diseases with no cure and they believe the diseases spread so fast. Respondents reported fear and stigma suffered by survivors, their families and the broader community due to these diseases.

Conclusion

Communities in Uganda affected by filovirus outbreaks have moderate knowledge about these diseases and have a positive attitude towards practices to prevent and control Ebola and Marburg viral diseases. The public health sector should enhance this community knowledge gap to empower them more by supplying educational materials for epidemic preparedness in future using appropriate communication channels as proposed by the communities.

Cost-effectiveness of a national enterovirus 71 vaccination program in China

11 September 2017 - 9:00pm

by Wenjun Wang, Jianwen Song, Jingjing Wang, Yaping Li, Huiling Deng, Mei Li, Ning Gao, Song Zhai, Shuangsuo Dang, Xin Zhang, Xiaoli Jia

Background and aims

Enterovirus 71 (EV71) has caused great morbidity, mortality, and use of health service in children younger than five years in China. Vaccines against EV71 have been proved effective and safe by recent phase 3 trials and are now available in China. The purpose of this study was to evaluate the health impact and cost-effectiveness of a national EV71 vaccination program in China.

Methods

Using Microsoft Excel, a decision model was built to calculate the net clinical and economic outcomes of EV71 vaccination compared with no EV71 vaccination in a birth cohort of 1,000,000 Chinese children followed for five years. Model parameters came from published epidemiology, clinical and cost data.

Results

In the base-case, vaccination would annually avert 37,872 cases of hand, foot and mouth disease (HFMD), 2,629 herpangina cases, 72,900 outpatient visits, 6,363 admissions to hospital, 29 deaths, and 945 disability adjusted life years. The break-even price of the vaccine was $5.2/dose. When the price was less than $8.3 or $14.6/dose, the vaccination program would be highly cost-effective or cost-effective, respectively (incremental cost-effectiveness ratio less than or between one to three times China GDP per capita, respectively). In one-way sensitivity analyses, the HFMD incidence was the only influential parameter at the price of $5/dose.

Conclusions

Within the price range of current routine vaccines paid by the government, a national EV71 vaccination program would be cost-saving or highly cost-effective to prevent EV71 related morbidity, mortality, and use of health service among children younger than five years in China. Policy makers should consider including EV71 vaccination as part of China’s routine childhood immunization schedule.

Naturally acquired antibody responses to more than 300 <i>Plasmodium vivax</i> proteins in three geographic regions

11 September 2017 - 9:00pm

by Rhea J. Longley, Michael T. White, Eizo Takashima, Masayuki Morita, Bernard N. Kanoi, Connie S. N. Li Wai Suen, Inoni Betuela, Andrea Kuehn, Piyarat Sripoorote, Camila T. Franca, Peter Siba, Leanne J. Robinson, Marcus Lacerda, Jetsumon Sattabongkot, Takafumi Tsuboi, Ivo Mueller

Plasmodium vivax remains an important cause of malaria in South America and the Asia-Pacific. Naturally acquired antibody responses against multiple P. vivax proteins have been described in numerous countries, however, direct comparison of these responses has been difficult with different methodologies employed. We measured antibody responses against 307 P. vivax proteins at the time of P. vivax infection, and at 2–3 later time-points in three countries. We observed that seropositivity rates at the time of infection were highest in Thailand, followed by Brazil then PNG, reflecting the level of antigenic input. The majority of sero-reactive antigens in all sites induced short-lived antibody responses with estimated half-lives of less than 6 months, although there was a trend towards longer-lived responses in PNG children. Despite these differences, IgG seropositivity rates, magnitude and longevity were highly and significantly rank-correlated between the different regions, suggesting such features are reflective of the individual protein.

Quality control methods for <i>Aedes albopictus</i> sterile male production

11 September 2017 - 9:00pm

by Fabrizio Balestrino, Arianna Puggioli, Marco Carrieri, Jérémy Bouyer, Romeo Bellini

The capacity of the released sterile males to survive, disperse, compete with wild males and inseminate wild females is an essential prerequisite to be evaluated in any area-wide integrated pest management (AW-IPM) programs including a sterile insect release method. Adequate quality control tests supported by standardized procedures need to be developed to measure these parameters and to identify and correct potential inappropriate rearing or handling methods affecting the overall male quality. In this study, we report results on the creation and validation of the first quality control devices designed to infer the survival and mating capacity of radio-sterilized Aedes albopictus males through the observation of their flight capacity under restricted conditions (flight organ device) and after stress treatment (aspirator device). Results obtained consistently indicate comparable flight capacity and quality parameters between untreated and 35 Gy irradiated males while a negative impact was observed with higher radiation doses at all observation time performed. The male flight capacity registered with the proposed quality control devices can be successfully employed, with different predictive capacities and response time, to infer the adult male quality. These simple and cost-effective tools provide a valuable method to detect and amend potentially sub-standard procedures in the sterile male production line and hence contribute to maintaining optimal quality and field performance of the mosquitoes being released.

Target product profiles for the diagnosis of <i>Taenia solium</i> taeniasis, neurocysticercosis and porcine cysticercosis

11 September 2017 - 9:00pm

by Meritxell Donadeu, Anna S. Fahrion, Piero L. Olliaro, Bernadette Abela-Ridder

Target Product Profiles (TPPs) are process tools providing product requirements to guide researchers, developers and manufacturers in their efforts to develop effective and useful products such as biologicals, drugs or diagnostics. During a WHO Stakeholders Meeting on Taenia solium diagnostics, several TPPs were initiated to address diagnostic needs for different stages in the parasite’s transmission (taeniasis, human and porcine cysticercosis). Following the meeting, draft TPPs were completed and distributed for consultation to 100 people/organizations, including experts in parasitology, human and pig cysticercosis, diagnostic researchers and manufacturers, international organizations working with neglected or zoonotic diseases, Ministries of Health and Ministries of Livestock in some of the endemic countries, WHO regional offices and other interested parties. There were 53 respondents. All comments and feedback received were considered and discussions were held with different experts according to their area of expertise. The comments were consolidated and final TPPs are presented here. They are considered to be live documents which are likely to undergo review and updating in the future when new knowledge and technologies become available.

Enhancing case definitions for surveillance of human monkeypox in the Democratic Republic of Congo

11 September 2017 - 9:00pm

by Lynda Osadebe, Christine M. Hughes, Robert Shongo Lushima, Joelle Kabamba, Beatrice Nguete, Jean Malekani, Elisabeth Pukuta, Stomy Karhemere, Jean-Jacques Muyembe Tamfum, Emile Wemakoy Okitolonda, Mary G. Reynolds, Andrea M. McCollum

Background

Human monkeypox (MPX) occurs at appreciable rates in the Democratic Republic of Congo (DRC). Infection with varicella zoster virus (VZV) has a similar presentation to that of MPX, and in areas where MPX is endemic these two illnesses are commonly mistaken. This study evaluated the diagnostic utility of two surveillance case definitions for MPX and specific clinical characteristics associated with laboratory-confirmed MPX cases.

Methodology/Principal findings

Data from a cohort of suspect MPX cases (identified by surveillance over the course of a 42 month period during 2009–2014) from DRC were used; real-time PCR diagnostic test results were used to establish MPX and VZV diagnoses. A total of 333 laboratory-confirmed MPX cases, 383 laboratory-confirmed VZV cases, and 36 cases that were determined to not be either MPX or VZV were included in the analyses. Significant (p<0.05) differences between laboratory-confirmed MPX and VZV cases were noted for several signs/symptoms including key rash characteristics. Both surveillance case definitions had high sensitivity and low specificities for individuals that had suspected MPX virus infections. Using 12 signs/symptoms with high sensitivity and/or specificity values, a receiver operator characteristic analysis showed that models for MPX cases that had the presence of ‘fever before rash’ plus at least 7 or 8 of the 12 signs/symptoms demonstrated a more balanced performance between sensitivity and specificity.

Conclusions

Laboratory-confirmed MPX and VZV cases presented with many of the same signs and symptoms, and the analysis here emphasized the utility of including 12 specific signs/symptoms when investigating MPX cases. In order to document and detect endemic human MPX cases, a surveillance case definition with more specificity is needed for accurate case detection. In the absence of a more specific case definition, continued emphasis on confirmatory laboratory-based diagnostics is warranted.

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