Herd Protection and Herd Amplification in Cholera

Recent analysis of results of the 1985 vaccine trial in Bangladesh showed that a killed oral cholera vaccine could provide herd protection (1), and this finding sheds new light on the potential utility of this vaccine and other oral cholera vaccines. Although there may be several mechanisms for herd protection, this finding of herd protection was somewhat unexpected. The nature of the herd protection with cholera vaccine is unlike that with live oral polio vaccine which can be excreted and can infect others, thereby immunizing per-sons who did not receive vaccine directly. By contrast, the cholera vaccine used in this study was inactivated, making it impossible for non-immunized persons to be immunized inadvertently. Another type of herd protection is seen with vaccine for Haemophilus influenzae type b in which the vaccination reduces respiratory carriage of the pathogen, thereby eradicating the reservoir and reducing transmission. Another example is that of measles vaccination which essentially stops transmission when the density of susceptible subjects is reduced below that needed to sustain transmission. Since cholera is transmitted directly from contaminated food or water, the finding of herd immunity seemed not entirely expected. This editorial reviews the evidence for herd protection and introduces new findings from the environmental studies on cholera to suggest a more complete understanding of the mechanisms for herd protection with cholera vaccine. Hopefully, by combining the observations of 'herd protection' with some newer concepts of 'herd amplification'coming from recent environmental studies, we may develop a better understanding of the most efficient ways to control cholera

Resolution and Resurgence of Schistosoma haematobium—induced Pathology After Community-based Chemotherapy in Ghana, as Detected by Ultrasound

Community-based treatment is recommended for endemic populations with urinary schistosomiasis; however, the optimal target group for treatment and retreatment interval have not been established. Using ultrasound, this study identified subpopulations whose lesions were most likely to respond to treatment and characterized resurgence of pathology. Ultrasound examination of 1202 infected patients was followed by chemotherapy with praziquantel. A sample of 698 patients was followed for 18 months after treatment. Nearly all types of bladder pathologies resolved after treatment, regardless of patient's age or intensity of initial infection. However, many patients' upper urinary tract pathologies (62.5%) did not resolve. During the 18-month follow-up period, reappearance of severe bladder pathologies was rare, and < 10% of persons had resurgence of mild bladder pathologies. For this population, re-treatment is not needed annually but might be cost effective if given several years later. Confirmation from other areas is required before general policies can be forme

Individual-specific changes in the human gut microbiota after challenge with enterotoxigenic Escherichia coli and subsequent ciprofloxacin treatment

Acknowledgements The authors wish to thank Mark Stares, Richard Rance, and other members of the Wellcome Trust Sanger Institute’s 454 sequencing team for generating the 16S rRNA gene data. Lili Fox Vélez provided editorial support. Funding IA, JNP, and MP were partly supported by the NIH, grants R01-AI-100947 to MP, and R21-GM-107683 to Matthias Chung, subcontract to MP. JNP was partly supported by an NSF graduate fellowship number DGE750616. IA, JNP, BRL, OCS and MP were supported in part by the Bill and Melinda Gates Foundation, award number 42917 to OCS. JP and AWW received core funding support from The Wellcome Trust (grant number 098051). AWW, and the Rowett Institute of Nutrition and Health, University of Aberdeen, receive core funding support from the Scottish Government Rural and Environmental Science and Analysis Service (RESAS).Peer reviewedPublisher PD

Utilización de placas de ELISA de alta y de baja avidez en la determinación de anticuerpos contra la toxina de cólera

Sera from an immunogenicity study of killed oral cholera vaccine was tested in high and low binding Elisa plates. High binding plates yielded 5 to 7-fold higher prevaccination IgG antitoxin titres and about 3-fold higher post-vaccine antitoxin titres, but lower cero-conversion rates (39% for high and 68% for low binding plates) when they were compared with low binding plates, because the pre-vaccine titres were relatively higher than the post-vaccine titres. The high titre serum, being used as a standard control serum in each ELISA plate, did not detect the problem. We suggest using lowbinding plates when carryng out ELlSA assays for cholera antitoxin antibodies.Los sueros de un estudio de inmunogenicidad de una vacuna oral de células enteras de Vibrio cholerae 01 más la subunidad B recombinante de la toxina (CEIsBr) fueron procesados para la determinación de anticuerpos antitoxina de cólera en placas de ELlSA de alta y de baja avidez. Los títulos de anticuerpos antitoxina, de la clase IgG, de los sueros prevacunales estuvieron incrementados de 5 a 7 veces, en las placas de alta avidez, comparados con los títulos obtenidos en las placas de baja avidez. Igualmente, los títulos de los sueros post vacunales fueron 3 veces superiores cuando se realizó la misma comparación de placas. Por consiguiente, la tasa de seroconversión medida en las placas de alta avidez fue de 39%, comparada con 68% al utilizar las placas de baja avidez. El suero control de alto título de anticuerpos no detectó el problema. Se sugiere utilizar placas de baja avidez al determinar anticuerpos contra la toxina de cólera por la técnica de ELISA

Multilocus sequence typing (MLST) analysis of Vibrio cholerae O1 El Tor isolates from Mozambique that harbour the classical CTX prophage.

Vibrio cholerae O1 isolates belonging to the Ogawa serotype, El Tor biotype, harbouring the classical CTX prophage were first isolated in Mozambique in 2004. Multilocus sequence typing (MLST) analysis using nine genetic loci showed that the Mozambique isolates have the same sequence type (ST) as O1 El Tor N16961, a representative of the current seventh cholera pandemic. Analysis of the CTX prophage in the Mozambique isolates indicated that there is one type of rstR in these isolates: the classical CTX prophage. It was also found that the ctxB-rstR-rstA-rstB-phs-cep fragment was PCR-amplified from these isolates, which indicates the presence of a tandem repeat of the classical CTX prophage in the genome of the Mozambique isolates. The possible origin of these isolates and the presence of the tandem repeat of the classical prophage in them implicate the presence of the classical CTX phage