Micromechanics of the growth of a craze fibril in glassy polymers

The primary objective of this work is to model the growth and eventual failure of a craze fibril in a classy polymer, starting from a primitive fibril. Experimental investigations have shown that properties like the entanglement density of a polymer play a pivotal role in determining whether macroscopic failure of a polymer occurs through crazing or shear yielding. Failure is seen to be related to the formation of a soft 'active zone' at the craze-bulk interface. through disentanglement. The present work aims at explaining some of the experimental findings about fibril growth and failure in glassy polymers on the basis of a continuum model of a craze with a constitutive model that accounts for yield, network hardening and disentanglement. The results show that this approach is capable of providing explanations for experimentally observed facts such as the propensity to crazing in polymers with low entanglement density and the linearity between the stretch in a fibril and the maximum stretch of a molecular strand in the fibril. (c) 2005 Elsevier Ltd. All rights reserved

Mapping the increasing risk of human alveolar echinococcosis in Limburg, The Netherlands

The parasite Echinococcus multilocularis was first detected in The Netherlands in 1996 and repeated studies have shown that the parasite subsequently spread in the local population of foxes in the province of Limburg. It was not possible to quantify the human risk of alveolar echinococcosis because no relationship between the amount of parasite eggs in the environment and the probability of infection in humans was known. Here, we used the spread of the parasite in The Netherlands as a predictor, together with recently published historical records of the epidemiology of alveolar echinococcosis in Switzerland, to achieve a relative quantification of the risk. Based on these analyses, the human risk in Limburg was simulated and up to three human cases are predicted by 2018. We conclude that the epidemiology of alveolar echinococcosis in The Netherlands might have changed from a period of negligible risk in the past to a period of increasing risk in the forthcoming year

Swine Trichinella Infection and Geographic Information System Tools

Pastured pigs are vulnerable to Trichinella spiralis infection through exposure to wild reservoir hosts. To evaluate the potential impact of the expanding production of pork from pasture-raised pigs, we mapped locations of T. spiralis occurrence and pastured-pig farms in the United States. Twenty-eight farms were located within 50 km of previous infection

Zoonotic Diseases Report 2013

De Staat van zoönosen 2013 geeft een overzicht van de mate waarin zoönosen in Nederland voorkomen en ontwikkelingen daarin op de lange termijn. Zoönosen zijn infectieziekten die van dier op mens overgaan. Net als in voorgaande jaren waren er in 2013 geen uitgesproken veranderingen te zien in de mate waarin zoönosen in Nederland voorkomen. Zoals ieder jaar deden zich ook in 2013 enkele opmerkelijke voorvallen voor, zoals een geval van hazenpest. In deze jaarlijkse uitgave van het RIVM en de NVWA is het thema 'huis-, tuin- en keukenzoönosen': zoönosen die mensen kunnen oplopen in en om het huis. Opmerkelijke voorvallen Bij een haas afkomstig uit Noord-Limburg werd in mei 2013 hazenpest (tularemie) vastgesteld. Vervolgens werd ook bij een jongeman tularemie vastgesteld, die de infectie waarschijnlijk via een dazenbeet in een natuurgebied in Limburg had opgelopen. In 2011 is er mogelijk ook een in Nederland opgelopen geval van tularemie geweest, terwijl in de jaren daarvoor alleen sporadisch gevallen gemeld werden die in het buitenland waren opgelopen. Een andere opmerkelijke gebeurtenis betrof een uitbraak van Campylobacter onder bezoekers van een pluimveeslachthuis die waarschijnlijk via de lucht aan de ziekteverwekker waren blootgesteld. Negen mensen werden ziek. Ook blijkt uit een onderzoek naar de vossenlintworm (Echinococcus multilocularis) onder vossen en honden, dat deze lintworm bij vossen in Zuid-Limburg veel vaker voorkomt dan in voorgaande jaren. Thema: huis-, tuin- en keukenzoönosen Juist in en om het huis kunnen mensen worden blootgesteld aan allerlei zoönoseverwekkers. Duizenden mensen krijgen jaarlijks via hun huisdieren ringworm, een schimmelinfectie. Ook kunnen zoönosen afkomstig zijn van huisdieren of dieren die hun behoefte doen in de tuin. Verder komen voedselgerelateerde zoönosen aan de orde, waarbij aandacht is voor het feit dat zoönosen ook via groenten kunnen worden opgelopen.The Zoonotic Diseases Report is an annual publication of the Dutch National Institute for Public Health and the Environment (RIVM) and the Netherlands Food and Consumer Product Safety Authority (NVWA). The report provides an overview of the incidence of zoonotic diseases in the Netherlands, as well as the associated long-term trends. Zoonotic diseases or zoonoses are infectious diseases that can be transmitted from animals to humans. As in previous years, no marked changes were observed in 2013 in the incidence of zoonotic diseases in the Netherlands. Every year a number of notable incidents occurres. In 2013 this included a case of rabbit fever (tularemia). This year's edition of the Zoonotic Diseases Report focuses in particular on 'zoonoses close to home', i.e. the risk of contracting a zoonotic disease in or around the house. Notable incidents In May 2013, rabbit fever (tularemia) was discovered in a hare originating from the north of the province of Limburg. Tularemia was later also diagnosed in a young man, who had probably contracted the infection after having been bitten by a horse fly in a nature reserve in Limburg. Another person possibly contracted tularemia in the Netherlands in 2011. In previous years only incidental cases were reported, with the disease being contracted abroad. Another notable incident concerned an outbreak of Campylobacter infection among visitors to a poultry slaughterhouse who had probably been exposed to airborne pathogens. Nine people fell ill as a result of this outbreak. An investigation into the incidence of Echinococcus multilocularis in foxes and dogs showed that this tapeworm was much more common in foxes in the south of Limburg province than in previous years. 'Zoonoses close to home' Humans can be exposed to various zoonotic disease pathogens in or around the house. Every year, thousands of people contract dermatophytosis (a fungal infection commonly known in the Netherlands as 'ringworm') from their pets. Zoonotic diseases can also be contracted from pets or from animals defecating in the garden. The report also devotes attention to food-related zoonotic diseases, with a particular focus on the risk of contracting zoonoses through the consumption or handling of vegetables.NVW

An experimental <i>Toxoplasma gondii </i>dose response challenge model to study therapeutic or vaccine efficacy in cats

High numbers of Toxoplasma gondii oocysts in the environment are a risk factor to humans. The environmental contamination might be reduced by vaccinating the definitive host, cats. An experimental challenge model is necessary to quantitatively assess the efficacy of a vaccine or drug treatment. Previous studies have indicated that bradyzoites are highly infectious for cats. To infect cats, tissue cysts were isolated from the brains of mice infected with oocysts of T. gondii M4 strain, and bradyzoites were released by pepsin digestion. Free bradyzoites were counted and graded doses (1000, 100, 50, 10), and 250 intact tissue cysts were inoculated orally into three cats each. Oocysts shed by these five groups of cats were collected from faeces by flotation techniques, counted microscopically and estimated by real time PCR. Additionally, the number of T. gondii in heart, tongue and brains were estimated, and serology for anti T. gondii antibodies was performed. A Beta-Poisson dose-response model was used to estimate the infectivity of single bradyzoites and linear regression was used to determine the relation between inoculated dose and numbers of oocyst shed. We found that real time PCR was more sensitive than microscopic detection of oocysts, and oocysts were detected by PCR in faeces of cats fed 10 bradyzoites but by microscopic examination. Real time PCR may only detect fragments of T. gondii DNA without the presence of oocysts in low doses. Prevalence of tissue cysts of T. gondii in tongue, heart and brains, and anti T. gondii antibody concentrations were all found to depend on the inoculated bradyzoite dose. The combination of the experimental challenge model and the dose response analysis provides a suitable reference for quantifying the potential reduction in human health risk due to a treatment of domestic cats by vaccination or by therapeutic drug application

Zoonotic Diseases Report 2014

De Staat van zoönosen geeft jaarlijks een overzicht van infectieziekten die overgaan van dier op mens, de zogenoemde zoönosen. Het gaat om de mate waarin meldingsplichtige zoönosen voorkomen en de ontwikkelingen daarvan op de lange termijn. Hierbij betreft het zowel het aantal ziektegevallen bij mensen als het voorkomen van deze ziekteverwekkers bij dieren. Ook worden elk jaar opmerkelijke voorvallen uitgelicht en wordt een thema behandeld. Voor de meeste zoönosen zijn in 2014 geen uitgesproken veranderingen waargenomen. Wel is het aantal mensen met leptospirose (waarvan de bekendste vorm de ziekte van Weil is) aanmerkelijk hoger dan het vorige jaar, van gemiddeld 30 gevallen in de afgelopen jaren naar 97 in 2014. Ook steeg het aantal Hantavirusinfecties (van gemiddeld 13 in de voorgaande jaren naar 36 in 2014). UItgelicht Een opmerkelijke gebeurtenis in 2014 is dat twee patiënten in een ziekenhuis zijn opgenomen met een ernstige longontsteking na een infectie met Chlamydia caviae. Beide patiënten bleken thuis cavia's te houden die een luchtweginfectie hadden doorgemaakt. Verder was er sinds 2003 weer een uitbraak van vogelgriep bij pluimveebedrijven veroorzaakt door een hoogpathogeen virus. Hierbij zijn vier van de vijf besmette bedrijven onafhankelijk van elkaar besmet geraakt. Het virus was vermoedelijk afkomstig van trekkende watervogels. Het is onbekend of dit virustype overdraagbaar is op de mens; wereldwijd zijn daar geen gevallen van bekend. Vogels Het thema van dit jaar is 'Onze gevleugelde vrienden' en gaat over zoönosen die via vogels kunnen worden overgebracht, zoals de papegaaienziekte. Hierbij wordt onder andere beschreven op welke vliegroutes van trekvogels gezamenlijke broed- en voederplaatsen liggen waar ze elkaar kunnen treffen en zoönoseverwekkers aan elkaar zouden kunnen overdragen.The Zoonotic Diseases Report provides an annual overview of infectious diseases transmitted from animals to humans, so-called zoonotic diseases or zoonoses. It focuses on the degree to which notifiable zoonoses occur and how they develop over the long term. Specifically, this concerns both the number of human cases and the occurrence of these pathogens in animals. Noteworthy incidents of zoonoses are also highlighted each year and a particular theme is discussed. For most zoonoses, no pronounced changes were observed in 2014. Nonetheless, the number of people with leptospirosis (of which the most well-known form is Weil's disease) was considerably higher than in the previous year, rising from an average of 30 cases in recent years to 97 cases in 2014. The number of Hantavirus infections also rose (from an average of 13 cases in the previous years to 36 cases in 2014). A closer look A notable event in 2014 is the admission of two patients to hospital with serious lung infections after being infected with Chlamydia caviae. Both patients kept guinea pigs at home that suffered from respiratory infections. There was also the first outbreak of highly pathogenic avian influenza since 2003 affecting five poultry farms. Four of the five farms became contaminated independently of each other. It is thought that the virus was transmitted from waterfowls. It is not known whether the particular virus strain can be transmitted to humans; worldwide no cases of such transmission have been reported. Birds This year's theme is 'Our winged friends'. It focuses on zoonoses that can be transmitted by birds, such as psittacosis (parrot fever). The migratory routes that coincide with shared breeding and feeding locations where migratory birds can come into contact with one another and thereby possibly transmit zoonotic pathogens to each other are also described.NVW

Anti-Malaria Drug Mefloquine Induces Motor Learning Deficits in Humans

Mefloquine (a marketed anti-malaria drug) prophylaxis has a high risk of causing adverse events. Interestingly, animal studies have shown that mefloquine imposes a major deficit in motor learning skills by affecting the connexin 36 gap junctions of the inferior olive. We were therefore interested in assessing whether mefloquine might induce similar effects in humans. The main aim of this study was to investigate the effect of mefloquine on olivary-related motor performance and motor learning tasks in humans. We subjected nine participants to voluntary motor timing (dart throwing task), perceptual timing (rhythm perceptual task) and reflex timing tasks (eye-blink task) before and 24 h after the intake of mefloquine. The influence of mefloquine on motor learning was assessed by subjecting participants with and without mefloquine intake (controls: n = 11 vs mefloquine: n = 8) to an eye-blink conditioning task. Voluntary motor performance, perceptual timing, and reflex blinking were not affected by mefloquine use. However, the influence of mefloquine on motor learning was substantial; both learning speed as well as learning capacity was impaired by mefloquine use. Our data suggest that mefloquine disturbs motor learning skills. This adverse effect can have clinical as well as social clinical implications for mefloquine users. Therefore, this side-effect of mefloquine should be further investigated and recognized by clinicians