The evolutionary history of <i>Shigella flexneri</i> serotype 6 in Asia

Shigella flexneri serotype 6 is an understudied cause of diarrhoeal diseases in developing countries, and has been proposed as one of the major targets for vaccine development against shigellosis. Despite being named as S. flexneri, Shigella flexneri serotype 6 is phylogenetically distinct from other S. flexneri serotypes and more closely related to S. boydii. This unique phylogenetic relationship and its low sampling frequency have hampered genomic research on this pathogen. Herein, by utilizing whole genome sequencing (WGS) and analyses of Shigella flexneri serotype 6 collected from epidemiological studies (1987-2013) in four Asian countries, we revealed its population structure and evolutionary history in the region. Phylogenetic analyses supported the delineation of Asian Shigella flexneri serotype 6 into two phylogenetic groups (PG-1 and -2). Notably, temporal phylogenetic approaches showed that extant Asian S. flexneri serotype 6 could be traced back to an inferred common ancestor arising in the 18th century. The dominant lineage PG-1 likely emerged in the 1970s, which coincided with the times to most recent common ancestors (tMRCAs) inferred from other major Southeast Asian S. flexneri serotypes. Similar to other S. flexneri serotypes in the same period in Asia, genomic analyses showed that resistance to first-generation antimicrobials was widespread, while resistance to more recent first-line antimicrobials was rare. These data also showed a number of gene inactivation and gene loss events, particularly on genes related to metabolism and synthesis of cellular appendages, emphasizing the continuing role of reductive evolution in the adaptation of the pathogen to an intracellular lifestyle. Together, our findings reveal insights into the genomic evolution of the understudied Shigella flexneri serotype 6, providing a new piece in the puzzle of Shigella epidemiology and evolution.</p

Vanishing wildlife corridors and options for restoration: a case study from Tanzania

Conserving wildlife corridors is increasingly important for maintaining ecological and genetic connectivity in times of unprecedented habitat fragmentation. Documenting connectivity loss, assessing root causes, and exploring restoration options are therefore priority conservation goals. A 2009 nationwide assessment in Tanzania documented 31 major remaining corridors, the majority of which were described as threatened. The corridor between the Udzungwa Mountains and the Selous Game Reserve in south-central Tanzania, a major link between western and southern wildlife communities, especially for the African elephant Loxodonta africana, provides an illuminating case study. A preliminary assessment in 2005 found that connectivity was barely persisting via two remaining routes. Here we present assessments of these two corridors conducted from 2007-2010, using a combination of dung surveys, habitat mapping and questionnaires. We found that both corridor routes have become closed over the last five years. Increased farming and livestock keeping, associated with both local immigration and population growth, were the main reasons for corridor blockage. However, continued attempts by elephants to cross by both routes suggest that connectivity can be restored. This entails a process of harmonizing differing land owners and uses towards a common goal. We provide recommendations for restoring lost connectivity and discuss the prospects for preventing further loss of corridors across the country

Threats of Zika virus transmission for Asia and its Hindu-Kush Himalayan region

This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.No specific funding was received for this research. However, the work of RM, UK and DAG was funded by the Federal Ministry of Education and Research of Germany (BMBF) under the project AECO (number 01Kl1717) as part of the National Research Network on Zoonotic Infectious Diseases of Germany

A descriptive analysis of clinico-demographic features and microbiological results of typhoid fever suspected patients in four large hospitals of Bhutan

Introduction: Bhutan reports about 2000 typhoid fever cases annually. We aimed at understanding the clinico-demographic features and microbiological results of patients with suspected typhoid fever. Methods: A yearlong (2012) study of typhoid fever suspects was conducted to describe and analyse associations of demographic and clinical features with laboratory findings. Results: A total of 457 patients were enrolled. Most patients were from Phuntsholing General Hospital (n=181; 39.6%) followed by Jigme Dorji Wangchuck National Referral Hospital (n=170; 37.2%), Eastern Regional Referral Hospital (n=56; 12.3%) and Central Regional Referral Hospital (n=50; 10.9%). Fever (n=420; 91.9 %) and headache (n=397; 86.9 %) were the commonest symptoms reported by the patients. Only 30% (n=137) and 11.2% (n=51) had diarrhoea and constipation respectively. Mean duration of illness was 11.2 days. Among the 457 Widal tests performed, 76.1% (n=348) were negative, 12.3 % (n=56) positive for O antigen, 8.5% (n=39) for H antigen and 3.1% (n=14) for both. Only 2 of the 109 (1.8%) patients with a positive Widal test had a positive blood culture. Widal test showed a sensitivity of 33.3% and specificity of 76.3%. There was no association of any symptoms to antibody titres. There were three peaks when suspected cases reported to hospitals. More than 97% (n=447) of blood were sterile and Salmonella Typhi was isolated only in 1.3% (n=6). Only one isolate showed resistance to amoxicillin and nalidixic acid. Conclusion: Typhoid fever was not being diagnosed satisfactorily but over-diagnosed and treated clinically. Widal test should be replaced by more sensitive and specific tests or used cautiously with well-defined cut-off titres. </p