PLoS Neglected Tropical Diseases News

Subscribe to PLoS Neglected Tropical Diseases News feed PLoS Neglected Tropical Diseases News
A Peer-Reviewed Open-Access Journal
Updated: 5 hours 24 min ago

An innovative approach to screening and chemoprophylaxis among contacts of leprosy patients in low endemic settings: experiences from Cambodia

28 March 2019 - 9:00pm

by Arielle Cavaliero, Helena Greter, Thomas Fürst, Sambath Lay, Sarady Sao Ay, Jan Robijn, Peter Steinmann

The landscape of enteric pathogen exposure of young children in public domains of low-income, urban Kenya: The influence of exposure pathway and spatial range of play on multi-pathogen exposure risks

27 March 2019 - 9:00pm

by Danielle Medgyesi, Daniel Sewell, Reid Senesac, Oliver Cumming, Jane Mumma, Kelly K. Baker

Young children are infected by a diverse variety of enteric pathogens in low-income, high-burden countries. Little is known about which conditions pose the greatest risk for enteric pathogen exposure and infection. Young children frequently play in residential public areas around their household, including areas contaminated by human and animal feces, suggesting these exposures are particularly hazardous. The objective of this study was to examine how the dose of six types of common enteric pathogens, and the probability of exposure to one or multiple enteric pathogens for young children playing at public play areas in Kisumu, Kenya is influenced by the type and frequency of child play behaviors that result in ingestion of soil or surface water. Additionally, we examine how pathogen doses and multi-pathogen exposure are modified by spatial variability in the number of public areas children are exposed to in their neighborhood. A Bayesian framework was employed to obtain the posterior distribution of pathogen doses for a certain number of contacts. First, a multivariate mixed effects tobit model was used to obtain the posterior distribution of pathogen concentrations, and their interdependencies, in soil and surface water, based upon empirical data of enteric pathogen contamination in three neighborhoods of Kisumu. Then, exposure doses were estimated using behavioral contact parameters from previous studies and contrasted under different exposure conditions. Pathogen presence and concentration in soil varied widely across local (< 25 meter radius area) and neighborhood-level scales, but pathogens were correlated among distinct surface water samples collected near to each other. Multi-pathogen exposure of children at public play areas was common. Pathogen doses and the probability of multi-pathogen ingestion increased with: higher frequency of environmental contact, especially for surface water; larger volume of soil or water ingested; and with play at multiple sites in the neighborhood versus single site play. Child contact with surface water and soil at public play areas in their neighborhood is an important cause of exposure to enteric pathogens in Kisumu, and behavioral, environmental, and spatial conditions are determinants of exposure.

Determinants for progression from asymptomatic infection to symptomatic visceral leishmaniasis: A cohort study

27 March 2019 - 9:00pm

by Jaya Chakravarty, Epco Hasker, Sangeeta Kansal, Om Prakash Singh, Paritosh Malaviya, Abhishek Kumar Singh, Ankita Chourasia, Toolika Singh, Medhavi Sudarshan, Akhil Pratap Singh, Bhawana Singh, Rudra Pratap Singh, Bart Ostyn, Michaela Fakiola, Albert Picado, Joris Menten, Jenefer M. Blackwell, Mary E. Wilson, David Sacks, Marleen Boelaert, Shyam Sundar

Background

Asymptomatic Leishmania donovani infections outnumber clinical presentations, however the predictors for development of active disease are not well known. We aimed to identify serological, immunological and genetic markers for progression from L. donovani infection to clinical Visceral Leishmaniasis (VL).

Methods

We enrolled all residents >2 years of age in 27 VL endemic villages in Bihar (India). Blood samples collected on filter paper on two occasions 6–12 months apart, were tested for antibodies against L. donovani with rK39-ELISA and DAT. Sero converters, (negative for both tests in the first round but positive on either of the two during the second round) and controls (negative on both tests on both occasions) were followed for three years. At the start of follow-up venous blood was collected for the following tests: DAT, rK39- ELISA, Quantiferon assay, SNP/HLA genotyping and L.donovani specific quantitative PCR.

Results

Among 1,606 subjects enrolled,17 (8/476 seroconverters and 9/1,130 controls) developed VL (OR 3.1; 95% CI 1.1–8.3). High DAT and rK39 ELISA antibody titers as well as positive qPCR were strongly and significantly associated with progression from seroconversion to VL with odds ratios of 19.1, 30.3 and 20.9 respectively. Most VL cases arose early (median 5 months) during follow-up.

Conclusion

We confirmed the strong association between high DAT and/or rK39 titers and progression to disease among asymptomatic subjects and identified qPCR as an additional predictor. Low predictive values do not warrant prophylactic treatment but as most progressed to VL early during follow-up, careful oberservation of these subjects for at least 6 months is indicated.

Correction: Alternative strategies for mosquito-borne arbovirus control

26 March 2019 - 9:00pm

by Nicole L. Achee, John P. Grieco, Hassan Vatandoost, Gonçalo Seixas, Joao Pinto, Lee Ching-NG, Ademir J. Martins, Waraporn Juntarajumnong, Vincent Corbel, Clement Gouagna, Jean-Philippe David, James G. Logan, James Orsborne, Eric Marois, Gregor J. Devine, John Vontas

Status and influencing factors of farmers’ private investment in the prevention and control of sheep brucellosis in China: A cross-sectional study

25 March 2019 - 9:00pm

by Heng Zeng, YouMing Wang, XiangDong Sun, Ping Liu, QuanGang Xu, Duan Huang, Lu Gao, ShiBing You, BaoXu Huang

Background

Brucellosis is one of the most common zoonoses worldwide, causing direct losses to the livestock industry and threatening human health. Little is known about the status and factors affecting farmers’ private investment in the prevention and control of sheep brucellosis in China.

Methodology/Principal findings

From April to October 2017, a cross-sectional, house-based study was conducted in 7 Chinese provinces. A total of 1037 households included in the study were analyzed. The average amount of private investment in the prevention and control of brucellosis was $0.73±0.54 per sheep. Multivariable analysis showed that factors facilitating private investment included older age of householder (OR = 1.07, 95%CI: 1.03–1.11), herd size >100 (OR = 2.49, 95%CI: 1.38–4.51), a higher percentage of income from sheep farming comparing to the total household income (OR = 1.14, 95%CI: 1.11–1.16), higher score of brucellosis knowledge (OR = 3.85, 95%CI: 1.40–10.51), actively learning related knowledge (OR = 2.98, 95%CI: 1.55–5.74), actively participating in related training courses (OR = 3.07, 95%CI: 1.52–6.18), care about other people’s attitudes (OR = 1.75, 95%CI: 1.35–2.28), concern about the health of neighbors’ livestock (OR = 1.75, 95%CI: 1.23–2.51). The analysis found a discouraging factor for private investment, supporting culling policy (OR = 0.67, 95%CI: 0.49–0.91).

Conclusions/Significance

In addition to providing interventions related to farmers’ knowledge, attitudes and practices, guidance must be offered to help farmers understanding the importance of private investment in the prevention and control of brucellosis.

Association between <i>IL1</i> gene polymorphism and human African trypanosomiasis in populations of sleeping sickness foci of southern Cameroon

25 March 2019 - 9:00pm

by Elvis Ofon, Harry Noyes, Vincent Ebo’o Eyanga, Flobert Njiokou, Mathurin Koffi, Pythagore Fogue, Christiane Hertz-Fowler, Annette MacLeod, Enock Matovu, Gustave Simo, for the TrypanoGEN Research Group, as members of The H3Africa Consortium

Background

Human African Trypanosomiasis (HAT) is a neglected tropical disease caused by infections due to Trypanosoma brucei subspecies. In addition to the well-established environmental and behavioural risks of becoming infected, there is evidence for a genetic component to the response to trypanosome infection. We undertook a candidate gene case-control study to investigate genetic associations further.

Methodology

We genotyped one polymorphism in each of seven genes (IL1A, IL1RN, IL4RN, IL6, HP, HPR, and HLA-G) in 73 cases and 250 controls collected from 19 ethno-linguistic subgroups stratified into three major ethno-linguistic groups, 2 pooled ethno-linguistic groups and 11 ethno-linguistic subgroups from three Cameroonian HAT foci. The seven polymorphic loci tested consisted of three SNPs, three variable numbers of tandem repeat (VNTR) and one INDEL.

Results

We found that the genotype (TT) and minor allele (T) of IL1A gene as well as the genotype 1A3A of IL1RN were associated with an increased risk of getting Trypanosoma brucei gambiense and develop HAT when all data were analysed together and also when stratified by the three major ethno-linguistic groups, 2 pooled ethno-linguistic subgroups and 11 ethno-linguistic subgroups.

Conclusion

This study revealed that one SNP rs1800794 of IL1A and one VNTR rs2234663 of IL1RN were associated with the increased risk to be infected by Trypanosoma brucei gambiense and develop sleeping sickness in southern Cameroon. The minor allele T and the genotype TT of SNP rs1800794 in IL1A as well as the genotype 1A3A of IL1RN rs2234663 VNTR seem to increase the risk of getting Trypanosoma brucei gambiense infections and develop sleeping sickness in southern Cameroon.

Using intervention mapping to design and implement quality improvement strategies towards elimination of lymphatic filariasis in Northern Ghana

25 March 2019 - 9:00pm

by Alfred Kwesi Manyeh, Latifat Ibisomi, Frank Baiden, Tobias Chirwa, Rohit Ramaswamy

Introduction

The Global Strategy to Eliminate Lymphatic Filiariasis (GFELF) through Mass Drug Administration (MDA) has been implemented in Ghana since the year 2000 and transmission has been interrupted in 76 of 98 endemic districts. To improve the MDA in the remaining districts with microfilaria (MF) prevalence above the 1% threshold for the interruption of transmission, there is a need to identify and implement appropriate quality improvement (QI) strategies. This paper describes the use of intervention mapping to select QI strategies to improve an existing evidence-based MDA program in Northern Ghana.

Methods

Due to the complexities associated with implementing evidence-based programs (EBP) such as the lymphatic filariasis MDA and variability in the context, an initial assessment to identify implementation bottlenecks associated with the quality of implementation of lymphatic filariasis MDA in the Bole District of Ghana was conducted using a mixed methods approach. Based on the findings of the initial assessment, a context specific QI strategy was designed and operationalized using intervention mapping strategy in terms of seven domains: actor, the action, action targets, temporality, dose, implementation outcomes addressed, and theoretical justification.

Results

The initial needs assessment shows that the persistent transmission of lymphatic filariasis in the Bole District is characterized by high levels of refusal to ingest the drug, high levels of reported adverse drug reactions, low MDA coverage at community level, poor adherence to the MDA protocol and non-participants’ responsiveness.

Conclusion

This study has shown that it is feasible to develop a context specific QI strategy for an existing evidence-based intervention based on an initial needs assessment through stakeholder participation using the IM approach. However, working (towards) QI requires more time than is usually available in public health service. Sufficient theoretical knowledge of implementation research and experience with technical IM experts must be available.

Oral activity of the antimalarial endoperoxide 6-(1,2,6,7-tetraoxaspiro[7.11]nonadec-4-yl)hexan-1-ol (N-251) against <i>Leishmania donovani</i> complex

25 March 2019 - 9:00pm

by Kofi Dadzie Kwofie, Kai Sato, Chizu Sanjoba, Akina Hino, Rieko Shimogawara, Michael Amoa-Bosompem, Irene Ayi, Daniel A. Boakye, Abraham K. Anang, Kyung-Soo Chang, Mitsuko Ohashi, Hye-Sook Kim, Nobuo Ohta, Yoshitsugu Matsumoto, Shiroh Iwanaga

Visceral leishmaniasis (VL) is a major problem worldwide and causes significant morbidity and mortality. Existing drugs against VL have limitations, including their invasive means of administration long duration of treatment regimens. There are also concerns regarding increasing treatment relapses as well as the identification of resistant clinical strains with the use of miltefosine, the sole oral drug for VL. There is, therefore, an urgent need for new alternative oral drugs for VL. In the present study, we show the leishmanicidal effect of a novel, oral antimalarial endoperoxide N-251. In our In vitro studies, N-251 selectively and specifically killed Leishmania donovani D10 amastigotes with no accompanying toxicity toward the host cells. In addition, N-251 exhibited comparable activities against promastigotes of L. donovani D10, as well as other L. donovani complex parasites, suggesting a wide spectrum of activity. Furthermore, even after a progressive infection was established in mice, N-251 significantly eliminated amastigotes when administered orally. Finally, N-251 suppressed granuloma formation in mice liver through parasite death. These findings indicate the therapeutic effect of N-251 as an oral drug, hence suggest N-251 to be a promising lead compound for the development of a new oral chemotherapy against VL.

Development of a SNP barcode to genotype <i>Babesia microti</i> infections

25 March 2019 - 9:00pm

by Mary Lynn Baniecki, Jade Moon, Kian Sani, Jacob E. Lemieux, Stephen F. Schaffner, Pardis C. Sabeti

Babesia microti is tick-borne disease that is an emerging threat to public health due to increasing prevalence and expanding geographic range. Detection and constant surveillance of babesiosis is imperative for predicting pathogen expansion. Leveraging our whole genome sequence (WGS) analyses of B. microti, we developed a single nucleotide polymorphism (SNP)-based high resolution melt (HRM) surveillance tool. We developed our HRM assay using available sequence data and identified 775 SNPs. From these candidate SNPs, we developed a 32-SNP barcode that is robust and differentiates geographically distinct populations; it contains SNPs that are putatively neutral, located in nuclear, mitochondrial, and apicoplastal regions. The assays are reproducible and robust, requiring a small quantity of DNA (limit of detection as low as 10 pg.). We analyzed the performance of our HRM assay using 26 B. microti clinical samples used in our WGS study from babesiosis endemic regions in the United States. We identified a minimal barcode consisting of 25 SNPs that differentiate geographically distinct populations across all clinical samples evaluated (average minor allele frequency > 0.22). Supporting our previous WGS findings, our 25-SNP barcode identified distinct barcode signatures that segregate B. microti into two lineages: Northeast and Midwest, with the Northeast having three subpopulations: Connecticut/Rhode Island, Nantucket, and the R1 reference group. Our 25-SNP HRM barcode provides a robust means genetic marker set that will aid in tracking the increasing incidence and expanding geographic range of B. microti infections.

Safety and efficacy of three trypanocides in confirmed field cases of trypanosomiasis in working equines in The Gambia: a prospective, randomised, non-inferiority trial

22 March 2019 - 9:00pm

by Alexandra G. Raftery, Saloum Jallow, Jean Rodgers, David G. M. Sutton

Background

Globally, working equines have a continued and growing socioeconomic role in supporting the livelihoods of between 300–600 million people in low income countries which is rarely recognised at a national or international level. Infectious diseases have significant impact on welfare and productivity in this population and equine trypanosomiasis is a priority disease due to its severity and prevalence. Strategies are required to improve the prevention, diagnosis, management and treatment of trypanosomiasis in equines and more data are required on the efficacy and safety of current trypanocidal drugs.

Methods

A prospective randomised, open-label non-inferiority trial was performed in The Gambia on horses and donkeys that fulfilled 2/5 clinical inclusion criteria (anaemia, poor body condition, pyrexia, history of abortion, oedema). Following randomised trypanocidal treatment (diminazene diaceturate, melarsomine dihydrochloride or isometamidium chloride), animals were observed for immediate adverse drug reactions and follow-up assessment was performed at 1 and 2 weeks. Blood samples underwent PCR analysis with specific Trypanosoma sp. primers. Treatment efficacy was assessed by measuring changes in clinical parameters, clinicopathological results and PCR-status post-treatment after evaluating for bias. Using PCR status as the outcome variable, non-inferiority of isometamidium treatment was determined if the upper bound limit of a 2-sided 95% CI was less than 10%.

Results

There was a significant beneficial effect upon the Trypanosoma sp. PCR positive population following trypanocidal treatment for all groups. The findings of clinical evaluation and PCR status supported a superior treatment effect for isometamidium. Melarsomine dihydrochloride efficacy was inferior to isometamidium. There were immediate, self-limiting side effects to isometamidium in donkeys (26%). Diminazene had the longest duration of action as judged by PCR status.

Conclusions

The data support the continued use of isometamidium following careful dose titration in donkeys and diminazene for trypanosomiasis in equines using the doses and routes of administration reported.

Helminth mediated modulation of the systemic and mycobacterial antigen – stimulated cytokine profiles in extra-pulmonary tuberculosis

21 March 2019 - 9:00pm

by Gokul Raj Kathamuthu, Saravanan Munisankar, Rathinam Sridhar, Dhanaraj Baskaran, Subash Babu

Background

Helminth infections are known to regulate cytokine responses in both pulmonary and latent tuberculosis infection. Whether helminth infections also modulate cytokine responses in extra-pulmonary tuberculosis, specifically tuberculous lymphadenitis (TBL), has not been examined thus far.

Methodology

Hence, to determine the cytokine profile in helminth-TBL coinfection, we measured the systemic and mycobacterial (TB)–antigen stimulated levels of Type 1, Type 2, Type 17, regulatory and pro-inflammatory cytokines in TBL individuals coinfected with or without Strongyloides stercoralis (Ss) infection.

Significant findings

TBL-Ss+ individuals have significantly higher bacterial burdens in the affected lymph nodes in comparison to TBL-Ss- individuals. TBL-Ss+ individuals exhibit significantly enhanced plasma levels of Type 2 (IL-5 and IL-13), Type 17 (IL-17 and IL-22) and regulatory (IL-10) cytokines in comparison to TBL-Ss- individuals. In contrast, TBL-Ss+ individuals exhibit significantly diminished plasma levels of pro-inflammatory cytokines (IL-1α and GM-CSF) in comparison to TBL-Ss- individuals. TBL-Ss+ individuals also exhibit significantly diminished unstimulated or mycobacterial—antigen stimulated levels of Type 1, Type 17 or IL-1 family cytokines in comparison to TBL-Ss- individuals but no differences in mitogen stimulated cytokine levels.

Conclusion

Therefore, our data reveal a profound influence of Ss infection on the bacteriological profile of TBL and suggesting that the underlying modulation of cytokine responses might be a mechanism by which this helminth infection could impart a detrimental effect on the pathogenesis of TBL disease.

Aurora kinase protein family in <i>Trypanosoma cruzi</i>: Novel role of an AUK-B homologue in kinetoplast replication

21 March 2019 - 9:00pm

by Matías Fassolari, Guillermo D. Alonso

Aurora kinases constitute a family of enzymes that play a key role during metazoan cells division, being involved in events like centrosome maturation and division, chromatin condensation, mitotic spindle assembly, control of kinetochore-microtubule attachments, and cytokinesis initiation. In this work, three Aurora kinase homologues were identified in Trypanosoma cruzi (TcAUK1, -2 and -3), a protozoan parasite of the Kinetoplastida Class. The genomic organization of these enzymes was fully analyzed, demonstrating that TcAUK1 is a single-copy gene, TcAUK2 coding sequence is present in two different forms (short and long) and TcAUK3 is a multi-copy gene. The three TcAUK genes are actively expressed in the different life cycle forms of T. cruzi (amastigotes, trypomastigotes and epimastigotes). TcAUK1 showed a changing localization along the cell cycle of the proliferating epimastigote form: at interphase it is located at the extremes of the kinetoplast while in mitosis it is detected at the cell nucleus, in close association with the mitotic spindle. Overexpression of TcAUK1 in epimastigotes leaded to a delay in the G2/M phases of the cell cycle due a retarded beginning of kinetoplast duplication. By immunofluorescence, we found that when it was overexpressed TcAUK1 lost its localization at the extremes of the kinetoplast during interphase, being observed inside the cell nucleus throughout the entire cell cycle. In summary, TcAUK1 appears to be a functional homologue of human Aurora B kinase, as it is related to mitotic spindle assembling and chromosome segregation. Moreover, TcAUK1 also seems to play a role during the initiation of kinetoplast duplication, a novel role described for this protein.

The prevalence and antifolate drug resistance profiles of <i>Plasmodium falciparum</i> in study participants randomized to discontinue or continue cotrimoxazole prophylaxis

21 March 2019 - 9:00pm

by Dennis W. Juma, Peninah Muiruri, Krista Yuhas, Grace John-Stewart, Ronald Ottichilo, John Waitumbi, Benson Singa, Christina Polyak, Edwin Kamau

Objective

Cotrimoxazole prevents opportunistic infections including falciparum malaria in HIV-infected individuals but there are concerns of cross-resistance to other antifolate drugs such as sulphadoxine-pyrimethamine (SP). In this study, we investigated the prevalence of antifolate-resistance mutations in Plasmodium falciparum that are associated with SP resistance in HIV-infected individuals on antiretroviral treatment randomized to discontinue (STOP-CTX), or continue (CTX) cotrimoxazole in Western Kenya.

Design

Samples were obtained from an unblinded, non-inferiority randomized controlled trial where participants were recruited on a rolling basis for the first six months of the study, then followed-up for 12 months with samples collected at enrollment, quarterly, and during sick visits.

Method

Plasmodium DNA was extracted from blood specimens. Initial screening to determine the presence of Plasmodium spp. was performed by quantitative reverse transcriptase real-time PCR, followed by genotyping for the presence of SP-resistance associated mutations by Sanger sequencing.

Results

The prevalence of mutant haplotypes associated with SP-resistant parasites in pfdhfr (51I/59R/108N) and pfdhps (437G/540E) genes were significantly higher (P = 0.0006 and P = 0.027, respectively) in STOP-CTX compared to CTX arm. The prevalence of quintuple haplotype (51I/59R/108N/437G/540E) was 51.8% in STOP-CTX vs. 6.3% (P = 0.0007) in CTX arm. There was a steady increase in mutant haplotypes in both genes in STOP-CTX arm overtime through the study period, reaching statistical significance (P < 0.0001).

Conclusion

The frequencies of mutations in pfdhfr and pfdhps genes were higher in STOP-CTX arm compared to CTX arm, suggesting cotrimoxazole effectively controls and selects against SP-resistant parasites.

Trial registration

ClinicalTrials.gov NCT01425073

A major hurdle in the elimination of urogenital schistosomiasis revealed: Identifying key gaps in knowledge and understanding of female genital schistosomiasis within communities and local health workers

21 March 2019 - 9:00pm

by Vida Ami Kukula, Eleanor E. MacPherson, Irene Honam Tsey, J. Russell Stothard, Sally Theobald, Margaret Gyapong

Background

Urogenital schistosomiasis is endemic throughout Ghana with elevated infection levels in certain areas e.g. Lake Volta Region. While the primary focus of the national control program is on mass drug administration of praziquantel to school-aged children, Female Genital Schistosomiasis (FGS), a disease-specific affliction of girls and women, has been largely overlooked. To better focus future actions, our study investigated the perceptions, knowledge and understanding of FGS amongst community members and health providers.

Method/Principal findings

We used qualitative methods including 12 focus group discussions and 34 in-depth interviews. We purposively selected 16 communities along the Lake Volta in the Shai-Osudoku District. Participant selection was based on gender, age and occupation; providing an opportunity to explore community understanding of FGS through participants own words and perceptions. Awareness of schistosomiasis was reported and is commonly experienced among children (12–17 years) and younger adults (18–25 years) in the study communities but is typically considered a boy’s disease. Knowledge of FGS was lacking in women, girls and front-line health workers. There was a general misconception that FGS may be the result of sexual promiscuity. Adolescent girls reporting vaginal discharge and itching were often stigmatized by health workers and treated for sexually transmitted infections. Limited alternatives to the river as key source of water meant that all members of the community faced the regular risk of schistosomiasis.

Conclusion/Significance

There is a clear imperative for the national control program to better engage on FGS and implement interventions to meet girls and women’s needs. The key consideration is to integrate more adequately preventive services with sexual and reproductive primary health care with future training of health workers for improved management of FGS cases. More broadly, harmonizing the portfolio of all actions on FGS is needed, especially with a call for improved access to safe water and sanitation for all those at current or future risk.

Calculating the prevalence of soil-transmitted helminth infection through pooling of stool samples: Choosing and optimizing the pooling strategy

21 March 2019 - 9:00pm

by James E. Truscott, Julia C. Dunn, Marina Papaiakovou, Fabian Schaer, Marleen Werkman, D. Timothy J. Littlewood, Judd L. Walson, Roy M. Anderson

Prevalence is a common epidemiological measure for assessing soil-transmitted helminth burden and forms the basis for much public-health decision-making. Standard diagnostic techniques are based on egg detection in stool samples through microscopy and these techniques are known to have poor sensitivity for individuals with low infection intensity, leading to poor sensitivity in low prevalence populations. PCR diagnostic techniques offer very high sensitivities even at low prevalence, but at a greater cost for each diagnostic test in terms of equipment needed and technician time and training. Pooling of samples can allow prevalence to be estimated while minimizing the number of tests performed. We develop a model of the relative cost of pooling to estimate prevalence, compared to the direct approach of testing all samples individually. Analysis shows how expected relative cost depends on both the underlying prevalence in the population and the size of the pools constructed. A critical prevalence level (approx. 31%) above which pooling is never cost effective, independent of pool size. When no prevalence information is available, there is no basis on which to choose between pooling and testing all samples individually. We recast our model of relative cost in a Bayesian framework in order to investigate how prior information about prevalence in a given population can be used to inform the decision to choose either pooling or full testing. Results suggest that if prevalence is below 10%, a relatively small exploratory prevalence survey (10–15 samples) can be sufficient to give a high degree of certainty that pooling may be relatively cost effective.

A comparative genome analysis of Rift Valley Fever virus isolates from foci of the disease outbreak in South Africa in 2008-2010

21 March 2019 - 9:00pm

by Moabi R. Maluleke, Maanda Phosiwa, Antoinette van Schalkwyk, George Michuki, Baratang A. Lubisi, Phemelo S. Kegakilwe, Steve J. Kemp, Phelix A. O. Majiwa

Rift Valley fever (RVF) is a re-emerging zoonotic disease responsible for major losses in livestock production, with negative impact on the livelihoods of both commercial and resource-poor farmers in sub-Sahara African countries. The disease remains a threat in countries where its mosquito vector thrives. Outbreaks of RVF usually follow weather conditions which favour increase in mosquito populations. Such outbreaks are usually cyclical, occurring every 10–15 years. Recent outbreaks of the disease in South Africa have occurred unpredictably and with increased frequency. In 2008, outbreaks were reported in Mpumalanga, Limpopo and Gauteng provinces, followed by 2009 outbreaks in KwaZulu-Natal, Mpumalanga and Northern Cape provinces and in 2010 in the Eastern Cape, Northern Cape, Western Cape, North West, Free State and Mpumalanga provinces. By August 2010, 232 confirmed infections had been reported in humans, with 26 confirmed deaths.To investigate the evolutionary dynamics of RVF viruses (RVFVs) circulating in South Africa, we undertook complete genome sequence analysis of isolates from animals at discrete foci of the 2008–2010 outbreaks. The genome sequences of these viruses were compared with those of the viruses from earlier outbreaks in South Africa and in other countries. The data indicate that one 2009 and all the 2008 isolates from South Africa and Madagascar (M49/08) cluster in Lineage C or Kenya-1. The remaining of the 2009 and 2010 isolates cluster within Lineage H, except isolate M259_RSA_09, which is a probable segment M reassortant. This information will be useful to agencies involved in the control and management of Rift Valley fever in South Africa and the neighbouring countries.

A protocol to count <i>Cryptosporidium</i> oocysts by flow cytometry without antibody staining

20 March 2019 - 9:00pm

by Karine Sonzogni-Desautels, Thomas Z. Di Lenardo, Axel E. Renteria, Marc-André Gascon, Timothy G. Geary, Momar Ndao

Cryptosporidiosis caused by the protozoan parasites Cryptosporidium hominis and C. parvum, threatens the lives of young children in developing countries. In veterinary medicine, C. parvum causes life-threatening diarrhea and dehydration in newborn dairy calves. Protocols to detect Cryptosporidium spp. oocysts using flow cytometry have been reported; however, these protocols use antibodies against the parasite and typically focus on detection of oocysts, not quantification. These techniques are not well-suited for studies that generate large variations in oocyst burdens because the amount of antibody required is proportional to the number of oocysts expected in samples. Also, oocysts are lost in washes in the staining protocol, reducing accuracy of oocyst counts. Moreover, these protocols require costly fluorochrome-conjugated monoclonal antibodies and are not optimal for studies involving large numbers of samples. Here we present an optimized protocol for purifying oocysts from mouse stool and intestine samples combined with a reliable method to quantify oocysts in a relatively pure population without the need for antibody staining. We used morphology (SSC-A vs FSC-A) and the innate characteristics of C. parvum oocysts compared to fecal and intestinal contaminants to develop a two-step gating strategy that can differentiate oocysts from debris. This method is a fast, reliable, and high-throughput technique to promote research projects on C. parvum infections in mice and potentially other animal hosts.

The influence of raw milk exposures on Rift Valley fever virus transmission

20 March 2019 - 9:00pm

by Elysse N. Grossi-Soyster, Justin Lee, Charles H. King, A. Desiree LaBeaud

Rift Valley fever virus (RVFV) is a zoonotic phlebovirus that can be transmitted to humans or livestock by mosquitoes or through direct contact with contaminated bodily fluids and tissues. Exposure to bodily fluids and tissues varies by types of behaviors engaged for occupational tasks, homestead responsibilities, or use in dietary or therapeutic capacities. While previous studies have included milk exposures in their analyses, their primary focus on livestock exposures has been on animal handling, breeding, and slaughter. We analyzed data from multiple field surveys in Kenya with the aim of associating RVFV infection to raw milk exposures from common animal species. Of those with evidence of prior RVFV infection by serology (n = 267), 77.2% engaged in milking livestock compared to 32.0% for 3,956 co-local seronegative individuals (p < 0.001), and 86.5% of seropositive individuals consumed raw milk compared to 33.4% seronegative individuals (p < 0.001). Individuals who milked and also consumed raw milk had greater odds of RVFV exposure than individuals whose only contact to raw milk was through milking. Increased risks were associated with exposure to milk sourced from cows (p < 0.001), sheep (p < 0.001), and goats (p < 0.001), but not camels (p = 0.98 for consuming, p = 0.21 for milking). Our data suggest that exposure to raw milk may contribute to a significant number of cases of RVFV, especially during outbreaks and in endemic areas, and that some animal species may be associated with a higher risk for RVFV exposure. Livestock trade is regulated to limit RVFV spread from endemic areas, yet further interventions designed to fully understand the risk of RVFV exposure from raw milk are imperative.

<i>Wolbachia</i> endosymbionts subvert the endoplasmic reticulum to acquire host membranes without triggering ER stress

20 March 2019 - 9:00pm

by Nour Fattouh, Chantal Cazevieille, Frédéric Landmann

The reproductive parasites Wolbachia are the most common endosymbionts on earth, present in a plethora of arthropod species. They have been introduced into mosquitos to successfully prevent the spread of vector-borne diseases, yet the strategies of host cell subversion underlying their obligate intracellular lifestyle remain to be explored in depth in order to gain insights into the mechanisms of pathogen-blocking. Like some other intracellular bacteria, Wolbachia reside in a host-derived vacuole in order to replicate and escape the immune surveillance. Using here the pathogen-blocking Wolbachia strain from Drosophila melanogaster, introduced into two different Drosophila cell lines, we show that Wolbachia subvert the endoplasmic reticulum to acquire their vacuolar membrane and colonize the host cell at high density. Wolbachia redistribute the endoplasmic reticulum, and time lapse experiments reveal tight coupled dynamics suggesting important signalling events or nutrient uptake. Wolbachia infection however does not affect the tubular or cisternal morphologies. A fraction of endoplasmic reticulum becomes clustered, allowing the endosymbionts to reside in between the endoplasmic reticulum and the Golgi apparatus, possibly modulating the traffic between these two organelles. Gene expression analyses and immunostaining studies suggest that Wolbachia achieve persistent infections at very high titers without triggering endoplasmic reticulum stress or enhanced ERAD-driven proteolysis, suggesting that amino acid salvage is achieved through modulation of other signalling pathways.

Pages