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Evaluating the role of surgical sterilisation in canine rabies control: A systematic review of impact and outcomes

PLoS Neglected Tropical Diseases News - 26 August 2020 - 9:00pm

by Abi Collinson, Malcolm Bennett, Marnie L. Brennan, Rachel S. Dean, Jenny Stavisky

Current recommendations for the elimination of canine-mediated human rabies focus on mass dog vaccination as the most feasible and cost-effective strategy. However, attempts to control rabies are often combined with canine surgical sterilisation programmes. The added value of sterilisation is widely debated. A systematic review was undertaken to compare the outcomes and impact of vaccination and sterilisation programmes with vaccination only programmes. A systematic search of three electronic databases (CAB Abstracts, Medline and Global Health) and grey literature was performed. From 8696 abstracts found, 5554 unique studies were identified, and 16 studies met the inclusion criteria. Eight described vaccination only programmes and eight described vaccination and sterilisation programmes. Indicators of impact measured were dog bites and/or doses of post-exposure prophylaxis administered; numbers of dog and/or human rabies cases; dog population demographic changes; changes in health and welfare of dogs, and indicators related to human behaviour change. The studies were contextually very diverse, programmes being implemented were complex, and there was variation in measurement and reporting of key indicators. Therefore, it was difficult to compare the two types of intervention, and impossible to make an evaluation of the role of sterilisation, using this evidence. Given the large number of vaccination and sterilisation programmes conducted globally, the lack of studies available for review highlights a gap in data collection or reporting, essential for impact assessment. There are several knowledge gaps concerning the impact of the sterilisation component alone, as well as subsequent effects on rabies transmission and control. Prospective studies comparing the outcomes and impact of the two interventions would be required in order to establish any additional contribution of sterilisation, as well as the underlying mechanisms driving any changes. In the absence of such evidence, the priority for rabies control objectives should be implementation of mass vaccination, as currently recommended by the World Health Organisation.

Emerging <i>Cryptococcus gattii</i> species complex infections in Guangxi, southern China

PLoS Neglected Tropical Diseases News - 26 August 2020 - 9:00pm

by Chunyang Huang, Clement K. M. Tsui, Min Chen, Kaisu Pan, Xiuying Li, Linqi Wang, Meini Chen, Yanqing Zheng, Dongyan Zheng, Xingchun Chen, Li Jiang, Lili Wei, Wanqing Liao, Cunwei Cao

The emergence and spread of cryptococcosis caused by the Cryptococcus gattii species complex has become a major public concern worldwide. C. deuterogattii (VGIIa) outbreaks in the Pacific Northwest region demonstrate the expansion of this fungal infection to temperate climate regions. However, infections due to the C. gattii species complex in China have rarely been reported. In this study, we studied eleven clinical strains of the C. gattii species complex isolated from Guangxi, southern China. The genetic identity and variability of these isolates were analyzed via multi-locus sequence typing (MLST), and the phylogenetic relationships among these isolates and global isolates were evaluated. The mating type, physiological features and antifungal susceptibilities of these isolates were also characterized. Among the eleven isolates, six belonged to C. deuterogattii, while five belonged to C. gattii sensu stricto. The C. deuterogattii strains from Guangxi, southern China were genetically variable and clustered with different clinical isolates from Brazil. All strains were MATα, and three C. deuterogattii isolates (GX0104, GX0105 and GX0147) were able to undergo sexual reproduction. Moreover, most strains had capsule and were capable of melanin production when compared to the outbreak strain from Canada. Most isolates were susceptible to antifungal drugs; yet one of eleven immunocompetent patients died of cryptococcal meningitis caused by C. deuterogattii (GX0147). Our study indicated that the highly pathogenic C. deuterogattii may be emerging in southern China, and effective nationwide surveillance of C. gattii species complex infection is necessary.

Multilocus sequence typing reveals diverse known and novel genotypes of <i>Leptospira</i> spp. circulating in Sri Lanka

PLoS Neglected Tropical Diseases News - 25 August 2020 - 9:00pm

by Lilani Karunanayake, Chandika D. Gamage, Chandima P. Gunasekara, Sajiv De Silva, Hidemasa Izumiya, Masatomo Morita, Devinda S. Muthusinghe, Kumiko Yoshimatsu, Roshan Niloofa, Panduka Karunanayake, Wimalasiri Uluwattage, Makoto Ohnishi, Nobuo Koizumi

Background

Leptospirosis has gained much attention in Sri Lanka since its large outbreak in 2008. However, most of the cases were clinically diagnosed and information on Leptospira genotypes and serotypes currently prevailing in the country is lacking.

Methodology/Principal findings

We retrospectively analyzed 24 Leptospira strains from human patients as well as isolated and characterized three Leptospira strains from black rats using the microscopic agglutination test with antisera for 19 serovars and multilocus sequence typing. The isolates were identified as Leptospira borgpetersenii sequence types (STs) 143 and 144; L. interrogans STs 30, 34, 43, 44, 74, 75, 80, 308, 313, 314, 316, and 317; and L. kirschneri ST318. Six of the 15 STs were identified for the first time in this study. Five serogroups such as Autumnalis, Grippotyphosa, Hebdomadis, Javanica, and Pyrogenes were detected among the isolates. Contrary to previous studies, various genotypes including novel STs were isolated during an outbreak in Southern Province. L. borgpetersenii serogroup Javanica ST143 was isolated both from a human and black rat.

Conclusions/Significance

This study revealed that genetically diverse Leptospira strains currently circulate in Sri Lanka: some genotypes have been circulating and others have emerged recently, which may explain the recent surge of leptospirosis patients with varying clinical manifestations and frequent outbreaks of leptospirosis. Black rats were identified as the source of infection for humans, but reservoir animals for other genotypes remain unknown.

A prospective cohort study of Cutaneous Leishmaniasis due to <i>Leishmania major</i>: Dynamics of the Leishmanin skin test and its predictive value for protection against infection and disease

PLoS Neglected Tropical Diseases News - 25 August 2020 - 9:00pm

by Jihène Bettaieb, Amine Toumi, Wissem Ghawar, Sadok Chlif, Mariem Nouira, Nabil Belhaj-Hamida, Adel Gharbi, Nissaf Ben-Alaya, Dhafer Laouini, Hechmi Louzir, Koussay Dellagi, Afif Ben Salah

Background

Leishmanin Skin Test (LST) is considered as a useful indicator of past infection by Leishmania parasites. However, the temporal dynamics of a positive LST under different epidemiologic scenarios and whether it relates to the protection against the recurrence of an overt disease are not fully documented.

Methodology/Principal findings

We report here on a population based prospective study conducted on 2686 individuals living in two foci located in Central Tunisia, to assess over a one-year epidemiologic season, the incidence of Leishmania (L.) major infection and disease and changes in LST reactivity. The two foci were both endemic for Cutaneous Leishmaniasis (CL) due to L. major, but contrasted in their history for this disease (ie: an old focus versus a recent focus).We found that most infections occurred in the new focus (290/1000; 95% CI: 265–315 person-years) with an incidence rate of CL lesions 2.4 times higher than in the old focus. Likewise, the rates of LST reactivity reversion and loss, in the new focus, were 99/1000[38–116] person-years and 14/1000[8–21] person-years, respectively. Loss of LST reactivity was not noticed in the old focus. Interestingly, the incidence rates of symptomatic infection did not differ significantly according to the LST status at enrolment (negative versus positive) between the combined foci and the new one.

Conclusions/Significance

Our findings confirm LST as a good tool for assessing L. major cryptic infection. However, the instability of the LST positivity in new foci should be considered as an important confounder of the outcome of this infection when developing a research protocol for vaccine trial.

Integration of animal health and public health surveillance sources to exhaustively inform the risk of zoonosis: An application to echinococcosis in Rio Negro, Argentina

PLoS Neglected Tropical Diseases News - 25 August 2020 - 9:00pm

by Andrew Lawson, R Boaz III, A. Corberán-Vallet, Marcos Arezo, Edmundo Larrieu, Marco A. Vigilato, Victor J. Del Rio Vilas

The analysis of zoonotic disease risk requires tshe consideration of both human and animal geo-referenced disease incidence data. Here we show an application of joint Bayesian analyses to the study of echinococcosis granulosus (EG) in the province of Rio Negro, Argentina. We focus on merging passive and active surveillance data sources of animal and human EG cases using joint Bayesian spatial and spatio-temporal models. While similar spatial clustering and temporal trending was apparent, there appears to be limited lagged dependence between animal and human outcomes. Beyond the data quality issues relating to missingness at different times, we were able to identify relations between dog and human data and the highest ‘at risk’ areas for echinococcosis within the province.

Clinical, parasitological and molecular profiles of Cutaneous Leishmaniasis and its associated factors among clinically suspected patients attending Borumeda Hospital, North-East Ethiopia

PLoS Neglected Tropical Diseases News - 25 August 2020 - 9:00pm

by Habtye Bisetegn, Ayalew Jejaw Zeleke, Endalamaw Gadisa, Girma Shumie, Demekech Damte, Tiruework Fenta, Sinkinesh Behaksra, Abebe Genetu Bayih

Background

Cutaneous leishmaniasis is one of the most neglected tropical diseases increasing in its public health importance. In Ethiopia over 28 million people are living at risk of infection.

Method

Institution based cross-sectional study was conducted at Borumeda Hospital from February to May 2019. A total 205 leishmaniasis suspected patients were included by systematic random sampling technique. Socio demographic characteristics were collected using pre-tested questionnaires. Parasitological investigation was done from skin slit sample by using Geimsa staining method. Species identification was done by PCR-RFLP. Data were entered in to EpiData version 3.1 and analyzed using SPSS version 20 software. P-value of ≤ 0.05 was considered as statistically significant.

Result

A total of 205 participants consisting 59% male and 41% female included in this study. The mean age (±SD) of the study participants was 31.9 (±14.29). The overall prevalence of cutaneous leishmaniasis was 22.4% (46/205). The prevalence in males (13.7%) was higher than in females (8.8%). It was more prevalent in the age group 16-45years old (15.6%). Clinically, 60% of patients’ hade single lesion with 1.55 average number of lesions. About 30.7% of patients’ had indurated plaque type of lesion. Most of the lesions were found on head and face (59%). House near to farmland, presence of hyrax in the village and presence of other cutaneous leishmaniasis cases in the neighborhood were independent predicator of cutaneous leishmaniasis prevalence. L.aethopica was found to be the etiologic agent of cutaneous leishmaniasis in the study participants.

Conclusion

The prevalence of cutaneous leishmaniasis was 22.4%, this alerts the need of intervention. It is statistically associated with house near to farm land, presence of other cutaneous leishmaniasis cases in the neighborhood and presence of hyrax in village. Head and face were the most common sites of lesion.

Comparison of clinico-epidemiological and radiological features in paracoccidioidomycosis patients regarding serological classification using antigens from <i>Paracoccidioides brasiliensis</i> complex and <i>Paracoccidioides lutzii</i>

PLoS Neglected Tropical Diseases News - 25 August 2020 - 9:00pm

by Edy F. Pereira, Gregory Gegembauer, Marilene R. Chang, Zoilo P. de Camargo, Thiago F. Nunes, Sergio M. Ribeiro, Lídia R. de Carvalho, Bianca M. Maldonado, Rinaldo P. Mendes, Anamaria M. M. Paniago

Genotyping of the genus Paracoccidioides showed its diversity and geographical distribution. Four species constituting the Paracoccidioides brasiliensis complex and Paracoccidioides lutzii are etiological agents of paracoccidioidomycosis (PCM). However, there are no studies comparing the clinical and epidemiological aspects between PCM caused by the P. brasiliensis complex and by P. lutzii. Demographic and clinical data from 81 patients with PCM—confirmed by mycological and/or histopathological examination—from Mato Grosso do Sul state (Brazil) were studied. All patients underwent serology by immunodiffusion with antigens obtained from the P. brasiliensis complex (ExoPb and gp43) and Cell Free Antigens obtained from P.lutzii (CFAPl).The cases were classified regarding their serological profile into three groups: G1: PCM patients seropositive to ExoPb and/or gp43 and seronegative to CFAPl (n = 51), assumed to have PCM caused by P. brasiliensis complex; G2: PCM patients seronegative to gp43 and seropositive to CFAPl (n = 16), with PCM caused by P. lutzii; and G3: PCM patients seropositive to ExoPb or gp43 and seropositive to CFAPl (n = 14), with undetermined serological profile, was excluded from the analyses. The Fisher's exact test or the Mann-Whitney U test, and cluster analysis according to Ward’s method and Euclidean distance were used to analyze the results. Patients with serological profile suggestive of P. lutzii lived predominantly in municipalities in the Central and Southern regions of the state, while those with serological profile indicative of the P. brasiliensis complex were distributed throughout the state. No differences were found between the two groups regarding gender, age, schooling, rural work, clinical form, severity, organs involved, intensity of pulmonary involvement, degree of anemia, erythrocyte sedimentation rate values, and therapeutic response. PCM patients with serological profile suggestive of P. lutzii and PCM patients with serological profile indicative of P. brasiliensis complex showed the same clinical and radiological presentations.

Prevalence and risk factors of <i>Schistosoma mansoni</i> infection among children under two years of age in Mbita, Western Kenya

PLoS Neglected Tropical Diseases News - 25 August 2020 - 9:00pm

by Miho Sassa, Evans A. Chadeka, Ngetich B. Cheruiyot, Mio Tanaka, Taeko Moriyasu, Satoshi Kaneko, Sammy M. Njenga, Sharon E. Cox, Shinjiro Hamano

Despite growing evidence that infants and very young children can be infected with schistosomes, the epidemiological features and risk factors are not well described in this age group. We aimed to assess the prevalence of S. mansoni infection in children under two years of age from a population with a known high burden of infection in school-aged children and adults and thus inform the need for interventions in this potentially vulnerable age group. In a cross-sectional study in Mbita Sub-county, along the east coast of Lake Victoria, Western Kenya, we enrolled 361 children aged 6–23 months. The prevalence of S. mansoni infection was detected using the Kato-Katz stool examination and a point-of-care test for urinary circulating cathodic antigen (POC-CCA) (Rapid Medical Diagnostics, Pretoria, South Africa). Three-hundred and five (305) children had complete data of whom 276 (90.5%, 95%CI: 86.6–93.5) children were positive for S. mansoni by the POC-CCA test, while 11 (3.6%, 95%CI: 1.8–6.4) were positive by the Kato-Katz method. All Kato-Katz positive cases were also positive by the POC-CCA test. In multivariable analysis, only geographical area, Rusinga West (AOR = 7.1, 95%CI: 1.4–35.2, P = 0.02), was associated with S. mansoni infection using Kato-Katz test. Independent associations for POC-CCA positivity included age, (12–17 months vs 6–11 months; AOR = 7.8, 95%CI: 1.8–32.6, P = 0.002) and breastfeeding in the previous 24 hours (AOR = 3.4, 95%CI: 1.3–9.0, P = 0.009). We found a potentially very high prevalence of S. mansoni infection among children under two years of age based on POC-CCA test results in Mbita Sub-county, Kenya, which if confirmed strongly supports the need to include infants in public health strategies providing universal prophylactic treatment in high burden settings. Further research is required to determine the accuracy of diagnostic tools to detect light infection among very young children and possible long-term health impacts.

Assessing the effect of insecticide-treated cattle on tsetse abundance and trypanosome transmission at the wildlife-livestock interface in Serengeti, Tanzania

PLoS Neglected Tropical Diseases News - 25 August 2020 - 9:00pm

by Jennifer S. Lord, Rachel S. Lea, Fiona K. Allan, Mechtilda Byamungu, David R. Hall, Jessica Lingley, Furaha Mramba, Edith Paxton, Glyn A. Vale, John W. Hargrove, Liam J. Morrison, Stephen J. Torr, Harriet K. Auty

In the absence of national control programmes against Rhodesian human African trypanosomiasis, farmer-led treatment of cattle with pyrethroid-based insecticides may be an effective strategy for foci at the edges of wildlife areas, but there is limited evidence to support this. We combined data on insecticide use by farmers, tsetse abundance and trypanosome prevalence, with mathematical models, to quantify the likely impact of insecticide-treated cattle. Sixteen percent of farmers reported treating cattle with a pyrethroid, and chemical analysis indicated 18% of individual cattle had been treated, in the previous week. Treatment of cattle was estimated to increase daily mortality of tsetse by 5–14%. Trypanosome prevalence in tsetse, predominantly from wildlife areas, was 1.25% for T. brucei s.l. and 0.03% for T. b. rhodesiense. For 750 cattle sampled from 48 herds, 2.3% were PCR positive for T. brucei s.l. and none for T. b. rhodesiense. Using mathematical models, we estimated there was 8–29% increase in mortality of tsetse in farming areas and this increase can explain the relatively low prevalence of T. brucei s.l. in cattle. Farmer-led treatment of cattle with pyrethroids is likely, in part, to be limiting the spill-over of human-infective trypanosomes from wildlife areas.

One-year descriptive analysis of patients treated at an anti-rabies clinic—A retrospective study from Kashmir

PLoS Neglected Tropical Diseases News - 25 August 2020 - 9:00pm

by Khalid Bashir, Inaamul Haq, S. Muhammad Salim Khan, Mariya Amin Qurieshi

Dog bites in humans are a major public health problem in India in general and Kashmir in particular. Canine rabies is almost non-existent in developed countries and exists mainly in the poorer, low socioeconomic strata of society in the developing world. The objective of this study was to determine the characteristics, pattern, and burden of dog bite injuries in the Kashmir valley. Data from Anti-Rabies Clinic of a tertiary care hospital in Srinagar, the summer capital of the state of Jammu & Kashmir, was collated and analyzed. Analysis of records of all the patients who had reported between April 2016 and March 2017 was done. A total of 6172 patients had reported to the Anti-Rabies Clinic for management of animal bites from 1st April 2016 to 31st March 2017. Most of the patients were young males. Almost half (47.7%) of the patients were bitten in the afternoon. Lower limbs were the most common site of bite (71.7%). Most of the bites were of Category III (57.6%) followed by Category II (42.3%); only one case of Category I was recorded. Almost all (98.0%) cases reported being bitten by dogs. Conclusions: Category III dog bites on lower limbs were the most common type of animal bites presenting to the Anti-Rabies Clinic of a tertiary care hospital. Children have more chances of a bite on head and neck region. Serious and workable efforts have to be made to reduce the incidence and consequences of animal bites.

<i>Schistosoma haematobium</i> infection and environmental factors in Southwestern Tanzania: A cross-sectional, population-based study

PLoS Neglected Tropical Diseases News - 24 August 2020 - 9:00pm

by Kirsi M. Manz, Inge Kroidl, Petra Clowes, Martina Gerhardt, Wilbrod Nyembe, Lucas Maganga, Weston Assisya, Nyanda E. Ntinginya, Ursula Berger, Michael Hoelscher, Elmar Saathoff

Schistosomiasis is a leading cause of morbidity in Africa. Understanding the disease ecology and environmental factors that influence its distribution is important to guide control efforts. Geographic information systems have increasingly been used in the field of schistosomiasis environmental epidemiology. This study reports prevalences of Schistosoma haematobium infection and uses remotely sensed and questionnaire data from over 17000 participants to identify environmental and socio-demographic factors that are associated with this parasitic infection. Data regarding socio-demographic status and S. haematobium infection were obtained between May 2006 and May 2007 from 17280 participants (53% females, median age = 17 years) in the Mbeya Region, Tanzania. Combined with remotely sensed environmental data (vegetation cover, altitude, rainfall etc.) this data was analyzed to identify environmental and socio-demographic factors associated with S. haematobium infection, using mixed effects logistic regression and geostatistical modelling. The overall prevalence of S. haematobium infection was 5.3% (95% confidence interval (CI): 5.0–5.6%). Multivariable analysis revealed increased odds of infection for school-aged children (5–15 years, odds ratio (OR) = 7.8, CI: 5.9–10.4) and the age groups 15–25 and 25–35 years (15–25 years: OR = 5.8, CI: 4.3–8.0, 25–35 years: OR = 1.6, CI: 1.1–2.4) compared to persons above 35 years of age, for increasing distance to water courses (OR = 1.4, CI: 1.2–1.6 per km) and for proximity to Lake Nyasa (<1 km, OR = 4.5, CI: 1.8–11.4; 1–2 km, OR = 3.5, CI: 1.7–7.5; 2–4 km; OR = 3.3, CI: 1.7–6.6), when compared to distances >4 km. Odds of infection decreased with higher altitude (OR = 0.7, CI: 0.6–0.8 per 100 m increase) and with increasing enhanced vegetation index EVI (OR = 0.2, CI: 0.1–0.4 per 0.1 units). When additionally adjusting for spatial correlation population density became a significant predictor of schistosomiasis infection (OR = 1.3, CI: 1.1–1.5 per 1000 persons/km2) and altitude turned non-significant. We found highly focal geographical patterns of S. haematobium infection in Mbeya Region in Southwestern Tanzania. Despite low overall prevalence our spatially heterogeneous results show that some of the study sites suffer from a considerable burden of S. haematobium infection, which is related to various socio-demographic and environmental factors. Our results could help to design more effective control strategies in the future, especially targeting school-aged children living in low altitude sites and/or crowded areas as the persons at highest need for preventive chemotherapy.

Positive impact of preventative chemotherapy during a national helminth control program: Perception and KAP

PLoS Neglected Tropical Diseases News - 24 August 2020 - 9:00pm

by Francisca Mutapi, Paradzayi Tagwireyi, Rivka Lim, Blessing Mangwanda, Charmaine Fourier, Takafira Mduluza

Helminth control at the national level is currently based on mass drug administration (MDA) programs. Perception of the MDA programs for helminth control by the affected populations influences compliance and future designs of the programs. We determined the perception of Zimbabwe’s National Helminth Control Program (2012–2017) with a specific focus on schistosomiasis in the school children treated with praziquantel, schoolteachers and village health workers (VHW). The study enrolled 409 children from Grades 6 and 7 who had the full benefit of the 6 years of MDA from 2012 to 2017. Thirty-six schoolteachers and 22 VHW serving the schools were also recruited. A structured questionnaire developed in English, translated into the local language Shona, and validated prior to the study was administered to the children and the adults. The questions focused on the perceived impact on health, school attendance and performance and Knowledge Attitudes and Practice (KAP) among the school children. Data were captured electronically on android platforms using the Open Data Kit. Overall, 84% of the children responded that their awareness of schistosomiasis (transmission, disease, treatment and infection avoidance) had improved because of participating in the MDAs. Of the 151 children self-diagnosed with schistosomiasis, 74% reported that their health had improved following treatment with praziquantel. This included resolution of haematuria, painful urination, sore stomach, tiredness and falling asleep during class lessons. The children and teachers reported improvements in both pupil school attendance and performance at school while the VHW and teachers reported an increase in health-seeking behaviour amongst the school children for schistosomiasis treatment in-between MDAs. The majority of VHW (96%) reported improvement in handwashing behaviour, schistosomiasis awareness (96%) and treatment uptake (91%) within the communities where the school children belonged. However, only 59% of the VHW reported improvement in toilet use while only 50% of the VHW reported improvement in clean water use within their communities. This study indicated that the surveyed children perceived the MDA program had improved their health, school attendance, school performance and awareness of schistosomiasis. The VHW also perceived that the MDA program had improved the community KAP.

Correction: Genus-wide <i>Leptospira</i> core genome multilocus sequence typing for strain taxonomy and global surveillance

PLoS Neglected Tropical Diseases News - 21 August 2020 - 9:00pm

by Julien Guglielmini, Pascale Bourhy, Olivier Schiettekatte, Farida Zinini, Sylvain Brisse, Mathieu Picardeau

Chlorination of <i>Schistosoma mansoni</i> cercariae

PLoS Neglected Tropical Diseases News - 21 August 2020 - 9:00pm

by Laura Braun, Yasinta Daniel Sylivester, Meseret Dessalegne Zerefa, Muluwork Maru, Fiona Allan, Feleke Zewge, Aidan M. Emery, Safari Kinung’hi, Michael R. Templeton

Background

Schistosomiasis is a water-based disease acquired through contact with cercaria-infested water. Communities living in endemic regions often rely on parasite-contaminated freshwater bodies for their daily water contact activities, resulting in recurring schistosomiasis infection. In such instances, water treatment can provide safe water on a household or community scale. However, to-date there are no water treatment guidelines that provide information on how to treat water containing schistosome cercariae. Here, we rigorously test the effectiveness of chlorine against Schistosoma mansoni cercariae.

Method

S. mansoni cercariae were chlorinated using sodium hypochlorite under lab and field condition. The water pH was controlled at 6.5, 7.0 or 7.5, the water temperature at 20°C or 27°C, and the chlorine dose at 1, 2 or 3 mg/l. Experiments were conducted up to contact times of 45 minutes. 100 cercariae were used per experiment, thereby achieving up to 2-log10 inactivations of cercariae. Experiments were replicated under field conditions at Lake Victoria, Tanzania.

Conclusion

A CT (residual chlorine concentration x chlorine contact time) value of 26±4 mg·min/l is required to achieve a 2-log10 inactivation of S. mansoni cercariae under the most conservative condition tested (pH 7.5, 20°C). Field and lab-cultivated cercariae show similar chlorine sensitivities. A CT value of 30 mg·min/l is therefore recommended to disinfect cercaria-infested water, though safety factors may be required, depending on water quality and operating conditions. This CT value can be achieved with a chlorine residual of 1 mg/l after a contact time of 30 minutes, for example. This recommendation can be used to provide safe water for household and recreational water activities in communities that lack safe alternative water sources.

Duplex real-time PCR for sexing <i>Schistosoma japonicum</i> cercariae based on W chromosome-specific genes and its applications

PLoS Neglected Tropical Diseases News - 21 August 2020 - 9:00pm

by Shuai Liu, Xianyu Piao, Nan Hou, Pengfei Cai, Yu Ma, Qijun Chen

As a unique feature among otherwise hermaphroditic trematodes, Schistosoma species are gonochoric parasites whose sex is genetically determined (ZZ for males and ZW for females). However, schistosome larvae are morphologically identical, and sex can only be discriminated by molecular methods. Here, we integrated published Schistosoma. japonicum transcriptome and genome data to identify W chromosome-specific genes as sex biomarkers. Three W chromosome-specific genes of S. japonicum were identified as sex biomarkers from a panel of 12 genes expressed only in females. An efficient duplex real-time PCR (qPCR) method for sexing cercariae was developed which could identify the sex of cercariae within 2 h without DNA extraction. Moreover, this method can be used to identify not only single-sex but also mixed-sex schistosome-infected snails. We observed a nearly equal proportion of single-male, single-female, and mixed-sex schistosome infections in artificially infected snails. Sex-known schistosome-infected snail models can be efficiently constructed with the aid of duplex qPCR. A field study revealed that single-sex schistosome infections were predominant among naturally infected snails. Finally, a schistosomiasis mouse model based on sex-known cercariae infection was shown to be more reliable than a model based on sex-unknown cercariae infection. The developed duplex qPCR method for sexing S. japonicum cercariae can be widely used for schistosomiasis modeling, genetic experiments, and field-based molecular epidemiological studies.

An analysis of preclinical efficacy testing of antivenoms for sub-Saharan Africa: Inadequate independent scrutiny and poor-quality reporting are barriers to improving snakebite treatment and management

PLoS Neglected Tropical Diseases News - 20 August 2020 - 9:00pm

by Stuart Ainsworth, Stefanie K. Menzies, Nicholas R. Casewell, Robert A. Harrison

Background

The World Health Organization’s strategy to halve snakebite mortality and morbidity by 2030 includes an emphasis on a risk-benefit process assessing the preclinical efficacy of antivenoms manufactured for sub-Saharan Africa. To assist this process, we systematically collected, standardised and analysed all publicly available data on the preclinical efficacy of antivenoms designed for sub-Saharan Africa.

Methodology/Principal findings

Using a systematic search of publication databases, we focused on publicly available preclinical reports of the efficacy of 16 antivenom products available in sub Saharan Africa. Publications since 1999 reporting the industry standard intravenous pre-incubation method of murine in vivo neutralisation of venom lethality (median effective dose [ED50]) were included. Eighteen publications met the criteria. To permit comparison of the several different reported ED50 values, it was necessary to standardise these to microlitre of antivenom resulting in 50% survival of mice challenged per milligram of venom (μl/mg). We were unable to identify publicly available preclinical data on four antivenoms, whilst data for six polyspecific antivenoms were restricted to a small number of venoms. Only four antivenoms were tested against a wide range of venoms. Examination of these studies for the reporting of key metrics required for interpreting antivenom ED50s were highly variable, as evidenced by eight different units being used for the described ED50 values.

Conclusions/Significance

There is a disturbing lack of (i) preclinical efficacy testing of antivenom for sub Saharan Africa, (ii) publicly available reports and (iii) independent scrutiny of this medically important data. Where reports do exist, the methods and metrics used are highly variable. This prevents comprehensive meta-analysis of antivenom preclinical efficacy, and severely reduces the utility of antivenom ED50 results in the decision making of physicians treating patients and of national and international health agencies. Here, we propose the use of a standardised result reporting checklist to resolve this issue. Implementation of these straightforward steps will deliver uniform evaluation of products across laboratories, facilitate meta-analyses, and contribute vital information for designing the clinical trials needed to achieve the WHO target of halving snakebite morbidity and mortality by 2030.

Accuracy of different diagnostic techniques for <i>Schistosoma haematobium</i> to estimate treatment needs in Zimbabwe: Application of a hierarchical Bayesian egg count model

PLoS Neglected Tropical Diseases News - 20 August 2020 - 9:00pm

by Nicholas Midzi, Oliver Bärenbold, Portia Manangazira, Isaac Phiri, Masceline J. Mutsaka-Makuvaza, Gibson Mhlanga, Jürg Utzinger, Penelope Vounatsou

Background

Treatment needs for Schistosoma haematobium are commonly evaluated using urine filtration with detection of parasite eggs under a microscope. A common symptom of S. haematobium is hematuria, the passing of blood in urine. Hence, the use of hematuria-based diagnostic techniques as a proxy for the assessment of treatment needs has been considered. This study evaluates data from a national survey in Zimbabwe, where three hematuria-based diagnostic techniques, that is microhematuria, macrohematuria, and an anamnestic questionnaire pertaining to self-reported blood in urine, have been included in addition to urine filtration in 280 schools across 70 districts.

Methodology

We developed an egg count model, which evaluates the infection intensity-dependent sensitivity and the specificity of each diagnostic technique without relying on a ‘gold’ standard. Subsequently, we determined prevalence thresholds for each diagnostic technique, equivalent to a 10% urine filtration-based prevalence and compared classification of districts according to treatment strategy based on the different diagnostic methods.

Principal findings

A 10% urine filtration prevalence threshold corresponded to a 17.9% and 13.3% prevalence based on questionnaire and microhematuria, respectively. Both the questionnaire and the microhematuria showed a sensitivity and specificity of more than 85% for estimating treatment needs at the above thresholds. For diagnosis at individual level, the questionnaire showed the highest sensitivity at (70.0%) followed by urine filtration (53.8%) and microhematuria (52.2%).

Conclusions/Significance

The high sensitivity and specificity of a simple questionnaire to estimate treatment needs of S. haematobium suggests that it can be used as a rapid, low-cost method to estimate district prevalence. Our modeling approach can be expanded to include setting-dependent specificity of the technique and should be assessed in relation to other diagnostic methods due to potential cross-reaction with other diseases.

Why is noma a neglected-neglected tropical disease?

PLoS Neglected Tropical Diseases News - 20 August 2020 - 9:00pm

by M. Leila Srour, Denise Baratti-Mayer

Noma is an orofacial gangrene affecting primarily children living in extreme poverty in remote parts of subtropical and tropical countries. Mortality and disability are high, and survivors often have physical and functional deformities resulting in stigma and isolation. Many healthcare professionals and primary healthcare workers where noma risk factors exist have no knowledge about noma and its implications. Public health measures to improve nutrition, immunizations, sanitation, and access to healthcare and measures to eliminate extreme poverty can lead to the eradication of noma. Research allocation has been insufficient to study the epidemiology, treatment, and prevention of noma. In a recent editorial by Hotez and colleagues in PLOS Neglected Tropical Diseases (NTDs), “What constitutes an NTD?” Noma is not included. The exclusion of noma from NTDs constitutes this preventable childhood disease as a neglected neglected disease. The purpose of this article is the inclusion of noma with the PLOS NTDs. Increased awareness and attention to noma can lead to the eradication of this disease affecting the world’s most vulnerable.

Challenges and prospects of snake antivenom supply in sub-Saharan Africa

PLoS Neglected Tropical Diseases News - 20 August 2020 - 9:00pm

by Abdulrazaq G. Habib, Baba M. Musa, Garba Iliyasu, Muhammad Hamza, Andreas Kuznik, Jean-Philippe Chippaux

Dengue in a crowded megacity: Lessons learnt from 2019 outbreak in Dhaka, Bangladesh

PLoS Neglected Tropical Diseases News - 20 August 2020 - 9:00pm

by Mohammad Sorowar Hossain, Mahbubul H. Siddiqee, Umme Ruman Siddiqi, Enayetur Raheem, Rokeya Akter, Wenbiao Hu

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