Lassa fever controls need to consider human to human transmission and the role of ‘super spreaders’, say researchers
By from News feed generator. Published on Jan 15, 2015.
Lassa fever is an acute viral haemorrhagic illness caused by Lassa virus. First identified in the village of Lassa, Nigeria, in 1969, the disease is thought to be transmitted to humans from contact with food or household items contaminated with rat urine or faeces. There have also been recorded cases of human-to-human transmission within hospital settings, but until now the risk – or mode – of transmission has not been clear. Understanding the different modes of transmission and how they are affected by factors such as people’s interaction with their environment is crucial for understanding the link between Lassa and changes in the ecosystem, and has important implications for public health strategies.
“Given the many competing health priorities in West Africa – exacerbated by the current Ebola epidemic – it is essential that we know the relative risk of human-to-human transmission of other potentially deadly diseases, such as Lassa fever,” says first author Dr Gianni Lo Iacono from the Department of Veterinary Medicine at the University of Cambridge. “That way, public health officials can decide where to focus their public health campaigns and how to prevent or respond to potential outbreaks.”
The researchers, part of the Dynamic Drivers of Disease in Africa Consortium, used mathematical modelling to analyse data from outbreaks known to be due to human-to-human chains of transmission, and calculated the ‘effective reproductive number’. This number represents the number of secondary infections from a typical infected individual – for an outbreak to take hold, this number needs to be greater than one. They compared data from hundreds of Lassa infected patients from Kenema Government Hospital, in Sierra Leone, who could have been infected either by rodents or humans, with the data from human-to-human chains. By considering the effective reproductive numbers, they inferred the proportion of patients infected by humans rather than rodents.
The researchers estimated that around one in five cases (20%) of infection is caused by human-to-human transmission. However, the study also highlighted the disproportionate number of infections that could be traced back to a small number of people, whom the researchers describe as ‘super-spreaders’ – rather than passing their infection on to just one other person (if at all), these individuals infected multiple others. It is not clear what makes them a super-spreader – their physiology, the environment in which they live, their social interactions or probably a combination of these factors.
Dr Donald Grant, chief physician at the Lassa ward in Kenema Government Hospital and co-author of the research, said: "Simple messages to the local people could change their perceptions of risk and hopefully make the difference. For example, making people aware that the virus can remain in urine for several weeks during the recovery period, could promote improved hygienic practices.
“What’s more, measures to target human-to-human spread of Lassa virus can be bundled in with prevention interventions for diseases with similar transmission routes, such as Ebola and even Hepatitis B.”
Professor James Wood, Head of the Department of Veterinary Medicine and senior author on the study, says: “The idea of super-spreaders in infectious diseases is not new. We’ve known about them since the notorious case of ‘Typhoid Mary’ in the early twentieth century and they’ve been documented for other diseases including TB, measles and SARS.
“Although we don’t understand what makes someone a ‘super-spreader’, it highlights the importance of strict hygiene measures in preventing infection. In the case of Lassa fever, we now know that whilst the chance of transmission between humans is much lower than it is from rodents, it is still a very real risk.”
Further progress has been hampered by the Ebola outbreak, which has resulted in the death of key collaborators in Kenema Government Hospital, which was used to nurse Ebola patients, in particular Dr Sheik Humarr Khan, who played such a key role in establishing and furthering the Lassa fever research programme.
The Dynamic Drivers of Disease in Africa Consortium, a multidisciplinary research project considering the linkages between zoonoses, ecosystems, health and wellbeing, is supported the UK Government through the Ecosystem for Poverty Alleviation (ESPA) research programme.
G. Lo Iacono, A. A. Cunningham, E. Fichet-Calvet, R. F. Garry, D. S. Grant, S. H. Khan, M. Leach, L. M. Moses, J. S. Schieffelin, J. G. Shaffer, C. T. Webb, J. L. N. Wood. Using modelling to disentangle the relative contributions of zoonotic and anthroponotic transmission: the case of Lassa fever. PLOS NTD; January 2015.
One in five cases of Lassa fever – a disease that kills around 5,000 people a year in West Africa – could be due to human-to-human transmission, with a large proportion of these cases caused by ‘super-spreaders’, according to research published today in the journal PLOS Neglected Tropical Diseases.
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Scientists ‘must not become complacent’ when assessing pandemic threat from flu viruses
By cjb250 from News feed generator. Published on Oct 15, 2014.
Influenza pandemics arise when a new virus strain – against which humans have yet to develop widespread immunity – spreads in the human population. There have been five such pandemics in the past 100 years, the worst of which – the 1918 Spanish Flu – cost 50 million lives worldwide. Of these pandemics, three are thought to have spread from birds and one from pigs. However, pandemic influenza strains represent only a tiny fraction of the total diversity of influenza viruses that exist in nature; the threats posed by the majority of these viruses are poorly understood. Assessing which viruses pose the greatest risk of causing the next human pandemic is an enormous challenge.
Steven Riley from Imperial College London, an author of the study, says: “There are too many strains of influenza viruses out there in non-human hosts to make it feasible to make preparations against each one. Instead, we need to get better at assessing the pandemic risks so that we know where best to focus our efforts. At the moment, this assessment is largely driven by a simple idea: animal viruses that cause sporadic human infections pose a greater risk than viruses that have not been documented to infect humans. But in fact, none of the viruses that caused the major pandemics of the last century were detected in humans before they emerged in their pandemic form.”
Writing in the journal eLife, the scientists set out the steps that they consider necessary to increase our ability to assess pandemic risk. As influenza virus genome sequencing becomes cheaper, faster and more readily available, the data it generates has the potential to transform the research community’s ability to predict the pandemic risk. However, it remains extremely difficult to predict just from a virus’s genome what symptoms it will elicit in its host – and hence how deadly the virus is. The researchers call for better integration of experimental data, computational methods and mathematical models, in conjunction with refinements to surveillance methodology.
However, they say that scientific insights into non‐human influenza viruses must not give way to complacency that the most substantial threats have been identified and characterized. They point out that several recent strains including the 2009 H1N1 “swine flu” pandemic virus and the recently emerged H7N9 viruses in China highlight the importance of remaining vigilant against as-yet unrecognized high risk viruses and the value of surveillance for influenza viruses in humans.
“No one can say with anything close to a hundred percent certainty when or where the next pandemic will start or which virus will cause it,” says Dr Colin Russell from the Department of Veterinary Medicine at the University of Cambridge. “We are getting much better at identifying and assessing potential threats, but we must be vigilant about surprises lurking around the corner.
“We need to be prepared for a swift response, with coordinated action, to help mitigate the spread of the next pandemic virus. Without developing this ability to respond, we will have spent billions building systems just for watching the next pandemic unfold.”
The research was supported in part by the Research and Policy for Infectious Disease Dynamics program of the US Department of Homeland Security and the National Institutes of Health.
Russell, CA et al. Improving pandemic influenza risk assessment. eLife; 15 Oct 2015
As our ability to assess the pandemic risk from strains of influenza virus increases with the latest scientific developments, we must not allow ourselves to become complacent that the most substantial threats have been identified, argue an international consortium of scientists.
The text in this work is licensed under a Creative Commons Licence. If you use this content on your site please link back to this page. For image rights, please see the credits associated with each individual image.
Understanding the bushmeat market: why do people risk infection from bat meat?
By cjb250 from News feed generator. Published on Oct 09, 2014.
The Straw-Coloured Fruit Bat, Eidolon helvum, is widely hunted and eaten in Ghana, but carries a risk of infection with ‘zoonotic’ pathogens – diseases transmitted from animal to man. Hunting, butchering and consuming wild animals for food can potentially transmit these infections through bites, scratches, bodily fluids, tissue and excrement. Bats in particular appear to host more zoonotic viruses per species than any other group of mammals, yet very little is known about how humans and bats interact, how people perceive bats and their accompanying disease risk, or who is most at risk.
Dr Olivier Restif from the Department of Veterinary Medicine at the University of Cambridge explains: “Knowing who eats bush meat and why, as well as how they perceive the risks, is important for informing both disease and conservation management plans. This requires a close-knit collaboration between epidemiologists, ecologists and social anthropologists. That is why we have teamed up with the Zoological Society of London and the University of Ghana to develop this research programme.”
Dr Alexandra Kamins, a Gates Cambridge scholar alumna working with Dr Restif, adds: “All too often, local community voices go unheard, despite representing those most at risk of spillover and often shouldering negative impacts arising from intervention measures. That is why it was important for us to listen to them.”
Dr Kamins and colleagues interviewed 577 people across southern Ghana, including hunters, vendors and consumers of bat meat. Of these, the majority (551) were interviewed using a general survey whilst the rest were interviewed in-depth through focus groups.
The researchers found that hunters used a variety of means to capture bats, including shooting, netting and scavenging, and that all of the hunters reported handling live bats, coming into contact with bat blood and getting scratched or bitten. None of the hunters reported using protective measures, such as gloves. Scavenged bats were collected alive, usually when a branch broke and bats fell to the ground, but this too carried risks: four interviewees explained how people would fight over the bats when a large branch fell, sometimes even lying down on top of bats to prevent others from taking them, often sustaining bites and scratches.
The bats were prepared and cooked in a number of ways, the most common methods being to smoke the bats before preparing food and using the bats in soup. At odds with reports from other countries, the survey in South East Ghana revealed few uses of bat bushmeat associated with traditional beliefs or medical practices. In Ghana, bat bushmeat seems to function as both subsistence and luxury food. The large number of hunters who hunt for themselves or who keep some of their catch suggests that bats provide a readily available source of animal protein. At the same time, high taste ratings among consumers and relatively high prices suggest that bat meat is seen as a ‘luxury food’ in Ghana.
Hunters, vendors and consumers of bat meat all tended to be older than those people with no connection to the practice - on average seven to ten years older. The researchers believe this could imply a number of scenarios, the most likely being a decrease in youth interest in bat bushmeat.
They found a strong association between gender and roles in the bat-bushmeat commodity chain, with hunters primarily being male and vendors female, consistent with the cultural norms of rural Ghanaian society. This could mean that disease risk was also different between the sexes. The researchers also found that those people living in urban environments and those who were more educated were less likely to participate in bat bushmeat activities. Although this suggests that increased urbanisation and improvements in education could reduce the use of bats as bushmeat, it is possible that increased household income could lead to increased bushmeat consumption, particularly as the meat appears to be seen as a luxury item.
Using focus groups, the researchers carried out more in-depth interviews to understand participants’ likely reactions to interventions regarding bat bushmeat. They found that regulations by themselves are not effective solutions: laws and fines alone are unlikely to induce change. While only some of our respondents would be willing to risk paying fines if they continued to earn enough from selling bat bushmeat, essentially no one knew of the existing hunting laws in Ghana, suggesting that enforcement is a major issue.
Possible health risks appeared to be more of a deterrent than fines; some respondents suggested that disease risk could motivate them to stop. However, the risk of disease from bat bushmeat was considered to be greatest by those who did not consume the meat and lowest by those who hunted or sold the bats. This finding supports previous research suggesting that people can readily perceive risk and even intellectually acknowledge desire to reduce that risk, but actual behaviour might not change.
Professor James Wood, who leads the research programme at the University of Cambridge, says: “Understanding both actual and perceived risk factors is vital. If a bat-borne zoonotic disease outbreak were to occur in Ghana, our information could prove invaluable in helping target those groups at greatest risk and in planning disease control measures.”
Dr Marcus Rowcliffe from ZSL adds: “Unfortunately, there may not be a simple way to minimise the risks of zoonotic spillover from bats. For example, bat hunting is a highly seasonal occupation and, like all bushmeat hunting, can be started and dropped at will, whereas rearing domestic animals – one possible sustainable solution for reducing bushmeat hunting – requires continuous activity throughout the year on a daily basis.
“Although many programmes suggest economic opportunity as the major motivation behind livelihood choices and success of alternatives, it may not be enough on its own. We found people in Ghana to be responsive to education pieces about the disease risk from bushmeat but also the ecological role of bats in pollination and seed dispersal. Working with local communities to help them find effective and sustainable solutions in line with their economic needs must be a long-term commitment.”
Kamins, AO et al. Characteristics and Risk Perceptions of Ghanaians Potentially Exposed to Bat-Borne Zoonoses through Bushmeat. Ecohealth; 30 Sept 2014
Ebola, as with many emerging infections, is likely to have arisen due to man’s interaction with wild animals – most likely the practice of hunting and eating wild meat known as ‘bushmeat’. A team of researchers led by the University of Cambridge and the Zoological Society of London (ZSL) has surveyed almost six hundred people across southern Ghana to find out what drives consumption of bat bushmeat – and how people perceive the risks associated with the practice.
The text in this work is licensed under a Creative Commons Licence. If you use this content on your site please link back to this page. For image rights, please see the credits associated with each individual image.
Why live vaccines may be most effective for preventing Salmonella infections
By cjb250 from News feed generator. Published on Sep 18, 2014.
The BBSRC-funded researchers used a new technique that they have developed where several populations of bacteria, each of which has been individually tagged with a unique DNA sequence, are administered to the same host (in this case, a mouse). This allows the researchers to track how each bacterial population replicates and spreads between organs or is killed by the immune system. Combined with mathematical modelling, this provides a powerful tool to study infections within the host. The findings are published today in the journal PLOS Pathogens.
“We effectively ‘barcode’ the bacteria so that we can see where in the body they go and how they fare against the immune system,” explains Dr Pietro Mastroeni from the Department of Veterinary Medicine at the University of Cambridge, who led the study. “This has provided us with some important insights into why some vaccines are more effective than others.”
The multidisciplinary research team led by Dr Mastroeni used the new technique to look at the effectiveness of vaccines against infection by the bacterium Salmonella enterica, which causes diseases including typhoid fever, non-typhoidal septicaemia and gastroenteritis in humans and animals world-wide. Current measures to control S. enterica infections are limited and the emergence of multi-drug resistant strains has reduced the usefulness of many antibiotics. Vaccination remains the most feasible means to counteract S. enterica infections.
There are two main classes of vaccine: live attenuated vaccines and non-living vaccines. Live attenuated vaccines use a weakened form of the bacteria or virus to stimulate an immune response – however, there are some concerns that the weakened pathogen may become more virulent when used in patients with compromised immune systems, for example people infected with HIV, malaria or TB. Non-living vaccines, on the other hand, are safer as they usually use inactive bacteria or viruses, or their fragments – but these vaccines are often less effective. Both vaccines work by stimulating the immune system to recognise a particular bacterium or virus and initiate the fight back in the event of future infection.
Using their new technique, Dr Mastroeni and colleagues showed that live Salmonella vaccines enhance the ability of the immune system to prevent the bacteria from replicating and spreading to other organs. They can also prevent the spread of the bacteria into the bloodstream, which causes a condition known as bacteraemia, a major killer of children in Africa.
They also found that the antibody response induced by live vaccines enhances the ability of immune cells known as phagocytes to kill bacteria in the very early stages of infection, but that a further type of immune cell known as the T-cell – again stimulated by the live vaccine – is subsequently necessary for control and clearance of the bacteria from the blood and tissues. The killed vaccine, whilst able to boost the phagocyte response via the production of antibodies, did not stimulate a protective form of T-cell immunity and was unable to prevent the subsequent bacterial growth in infected organs or the development of bacteraemia, and was unable to control the spread of the bacteria in the body.
Dr Chris Coward, first author on the study, says: "We have used a collaboration between experimental science and mathematical modelling to examine how vaccines help the immune system control infection. We found that, for Salmonella infections, the immune response induced by a killed vaccine initially kills a proportion of the invading bacteria but the surviving bacteria then replicate resulting in disease. The live vaccine appears superior because it induces a response that both kills the bacteria and restrains their growth, leading to elimination of the infection."
Dr Mastroeni adds: “There is a big push towards the use of non-living vaccines, which are safer, particularly in people with compromised immune systems – and many of the infections such as Salmonella are more prevalent and dangerous in countries blighted by diseases such as HIV, malaria and TB. But our research shows that non-living vaccines against Salmonella may be of limited use only and are not as effective as live vaccines. Therefore more efforts are needed to improve the formulation and delivery of non-living vaccines if these are to be broadly and effectively used to combat systemic bacterial infections. We have used Salmonella infections as a model, but our research approaches can be extended to many pathogens of humans and domestic animals.”
The research was carried out Dr Mastroeni, Dr Coward and colleagues Dr Andrew Grant, Dr Oliver Restif, Dr Richard Dybowski and Professor Duncan Maskell. It was funded by the Biotechnology and Biological Sciences Research Council, which has recently awarded Dr Mastroeni funding to extend this research to the study of how antibiotics work. The new research aims to optimise treatments and reduce the appearance of antibiotic resistance.
Professor Melanie Welham, BBSRC’s Science Director, said: "To protect our health and the health of animals we rely on, such as livestock, effective vaccines are needed against disease. This new technique provides unique insights that will help us compare vaccines produced in different ways to ensure the best disease prevention strategies."
Coward, C et al. The Effects of Vaccination and Immunity on Bacterial Infection Dynamics In Vivo. PLOS Pathogens; 18 Sept 2014
Vaccines against Salmonella that use a live, but weakened, form of the bacteria are more effective than those that use only dead fragments because of the particular way in which they stimulate the immune system, according to research from the University of Cambridge published today.
Global snapshot of infectious canine cancer shows how to control the disease
By cjb250 from News feed generator. Published on Sep 03, 2014.
The survey of veterinarians across the world confirmed that Canine Transmissible Venereal Tumour (CTVT) has a global reach. Researchers from the University of Cambridge found that the countries and areas with the lowest rates of the disease also had strong dog control policies. These include managing the number of street dogs; spay and neuter practices; and quarantine procedures for imported dogs.
CTVT first originated as a tumour in a single dog that lived thousands of years ago, and by becoming transmissible, this cancer has become the oldest, most widespread and prolific cancer known in nature. It causes tumours of the genitals, and is spread by the transfer of living cancer cells between dogs during sex. CTVT is one of only two known transmissible cancers – the other has ravaged the wild Tasmanian devil population.
Until now, no systematic global survey of the disease had been performed. To understand the global distribution and prevalence of the disease, the scientists sent a questionnaire to 645 veterinarians and animal health workers around the world. The replies showed that CTVT is endemic in dogs in at least 90 of 109 countries surveyed.
The researchers found that the only cases of CTVT reported in countries in Northern Europe, where free-roaming dogs are absent, were found in dogs that had been imported from abroad. There were no reports of CTVT in New Zealand, a country with strict dog quarantine policies. On the other hand, the disease was more likely to be present in countries or areas with free-roaming dog populations.
Andrea Strakova from the Department of Veterinary Medicine says: “Although CTVT can usually be effectively treated, lack of awareness of the disease and poor access to veterinary care mean it can go untreated and impact the welfare of dogs. Research and monitoring of this disease may lead to improved methods for disease prevention, detection and treatment.”
Dr Elizabeth Murchison adds: “Our study has suggested that free-roaming dogs are a reservoir for CTVT. Our review of the historical literature indicated that CTVT was eradicated in the UK during the twentieth century, probably as an unintentional result of the introduction of dog control policies. Careful management of free-roaming dog populations, as well as inclusion of CTVT in dog import/export quarantine policies, may help to control CTVT spread.”
The research also highlighted the importance of dog sterilisation programs in controlling CTVT spread. However, dog spaying and neutering may not always be protective against CTVT, possibly because the disease can also be spread by biting, licking or sniffing.
The research highlights the remarkable global spread of a single canine cancer which has continued to survive beyond the animal that first spawned it.
Adapted from a press release from BioMed Central.
Andrea Strakova and Elizabeth Murchison. The changing global distribution and prevalence of canine transmissible venereal tumour. BMC Veterinary Research; 3 Sept 2014
While countries with dog control policies have curbed an infectious and gruesome canine cancer, the disease is continuing to lurk in the majority of dog populations around the world, particularly in areas with many free-roaming dogs. This is according to research published in the open access journal BMC Veterinary Research.
First national model for bovine TB calls for greater focus on cattle
By cjb250 from News feed generator. Published on Jul 02, 2014.
The model, developed by researchers at the University of Warwick and University of Cambridge, suggests that improved testing, vaccination of cattle and culling of all cattle on infected farms would be the most effective strategies for controlling the disease. It found that whilst badgers – the subject of controversial culling plans to stem the spread of the disease – form part of the environmental reservoir, they only play a relatively minor role in the transmission of infection.
Based on a study of cattle and the causes of bovine TB in Great Britain, the model, published in the journal Nature, sought to ascertain how and why the epidemic has grown over the past 15 years. Using data from the Animal Health and Veterinary Laboratories Agency and the Department for the Environment, Food and Rural Affairs (Defra), the researchers developed a mathematical model that incorporated both within- and between-farm bovine TB transmission.
“Our model offers a dispassionate, unbiased view of the spread of bovine TB through the cattle industry of Great Britain,” says Professor Matthew Keeling, from the University of Warwick’s School of Life Sciences and Department of Mathematics. “The model is based on the recorded pattern of positive and negative tests and uses the known movement of cattle around the country. We aim for it to provide policy-makers with the best evidence possible from which to make decisions relating to bovine TB and to contribute to the ongoing discussions on this sensitive issue.”
The model allowed the researchers to tease apart how different routes involved in transmission interact and overlap.
Dr Ellen Brooks-Pollock from the Department of Veterinary Medicine at the University of Cambridge adds: “By using the most recent data, our model predicts that it is most likely that both cattle movements and the local environment are driving the front of the epidemic. Imperfect cattle skin tests contribute to the spread by delaying the time until infected herds are detected for the first time and incorrectly identifying herds as clear of infection.”
One of the key results from the model is the large variation in what happens to farms once they are infected.
“We found that the vast majority of infected farms don’t spread the infection to any other farms before they clear infection themselves. Only a small number of farms spread the infection, and they can cause the majority of new cases”, says Dr Brooks-Pollock.
The researchers argue that the findings are essential for improving the targeting of control measures. If infected farms can be identified and caught early then it might be possible to make substantial progress in tackling the epidemic.
“The model we are putting forward can be used to address several potential control methods – but there is no single panacea,” says Professor Keeling. “All controls have advantages and disadvantages. However, we find only three controls have the power to reverse the current increase in cases: more frequent or more accurate testing, vaccination of cattle and culling all cattle on infected farms.”
The control measures the researchers investigated were designed to be ‘idealised’ control options to understand what measures in theory could stop the increasing epidemic. The researchers did not consider the practicalities or economics of implementing control measures.
The research was funded by the Biotechnology and Biological Sciences Research Council, the Wellcome Trust and the Engineering and Physical Sciences Research Council.
Adapted from a press release from the University of Warwick.
The majority of outbreaks of bovine TB within cattle herds are caused by multiple transmissions routes – including failed cattle infection tests, cattle movement and reinfection from environmental reservoirs such as infected pastures and wildlife – according to the first national model of bovine TB spread, published today.
Winners of the first Odile Bain Memorial Prize announced
By pbh25 from News feed generator. Published on Jun 12, 2014.
University Senior Lecturer Dr Cinzia Cantacessi is one of two winners of the inaugural Odile Bain Memorial Prize for early career scientists who have made an outstanding contribution to the fields of medical and veterinary parasitology.
The Odile Bain prize is sponsored by the open access journal Parasites & Vectors and the animal health company Merial. It is awarded in memory of Odile Bain’s outstanding contribution to medical and veterinary parasitology and her actions in encouraging productive collaborations among biologists, veterinarians, physicians, and fundamental and applied parasitologists worldwide.
Dr Cinzia Cantacessi is the winner of the Veterinary Parasitology category. She is a Senior Lecturer at the University of Cambridge's Department of Veterinary Medicine and receives the prize in recognition of her significant advances to the application of bioinformatic methods in parasitology, across a wide span of organisms of great impact for veterinary and human health.
Domenico Otranto, chair of the prize evaluation committee and Parasites & Vectors Advisory Board member says: “Over almost half a Century, the research of Odile Bain had a major impact on the scientific community. Her charming personality, infectious enthusiasm for the research and her supportive attitude towards early career scientists inspired the establishment of this prestigious Award to perpetuate her name. Undoubtedly, Odile represents a role model for young generations of scientists.“
The prizes were formally awarded during the joint meeting of the Irish Society of Parasitology/British Association for Veterinary Parasitology/European Veterinary Parasitology College at University College Dublin this week.
Dr Cinzia Cantacessi says: “I feel extremely honoured and privileged to represent a generation of young parasitologists whose remarkable work keeps our discipline at the forefront of biomedical research. Truly dedicated mentors like Odile Bain have contributed to shape and inspire us all.”
The other scientist recognised was Dr Stefanie Knopp, winner of the Medical Parasitology category. She is a postdoctoral researcher at the Swiss Tropical and Public Health Institute in Basel, Switzerland and at the Natural History Museum in London.
11,000-year-old living dog cancer reveals its secrets
By fpjl2 from News feed generator. Published on Jan 23, 2014.
This cancer, which causes grotesque genital tumours in dogs around the world, first arose in a single dog that lived about 11,000 years ago. The cancer survived after the death of this dog by the transfer of its cancer cells to other dogs during mating.
The genome of this 11,000-year-old cancer carries about two million mutations – many more mutations than are found in most human cancers, the majority of which have between 1,000 and 5,000 mutations. The team used one type of mutation, known to accumulate steadily over time as a “molecular clock”, to estimate that the cancer first arose 11,000 years ago.
“The genome of this remarkable long-lived cancer has demonstrated that, given the right conditions, cancers can continue to survive for more than 10,000 years despite the accumulation of millions of mutations,” said Dr Elizabeth Murchison from Cambridge’s Department of Veterinary Medicine and the Wellcome Trust Sanger Institute, who is lead author on the study, published today in the journal Science.
The genome of the transmissible dog cancer still harbours the genetic variants of the individual dog that first gave rise to the cancer 11,000 years ago. Analysis of these genetic variants revealed that this dog may have resembled an Alaskan Malamute or Husky. It probably had a short, straight coat that was coloured either grey/brown or black. Its genetic sequence could not determine if this dog was a male or a female, but did indicate that it was a relatively inbred individual.
“We do not know why this particular individual gave rise to a transmissible cancer,” said Murchison, “But it is fascinating to look back in time and reconstruct the identity of this ancient dog whose genome is still alive today in the cells of the cancer that it spawned.”
Transmissible dog cancer is a common disease found in dogs around the world today. The genome sequence has helped scientists to further understand how this disease has spread.
“The patterns of genetic variants in tumours from different continents suggested that the cancer existed in one isolated population of dogs for most of its history,” says Dr Murchison. “It spread around the world within the last 500 years, possibly carried by dogs accompanying seafarers on their global explorations during the dawn of the age of exploration.”
Transmissible cancers are extremely rare in nature. Cancers, in humans and animals, arise when a single cell in the body acquires mutations that cause it to produce more copies of itself. Cancer cells often spread to different parts of the body in a process known as metastasis.
However, it is very rare for cancer cells to leave the bodies of their original hosts and to spread to other individuals. Apart from the dog transmissible cancer, the only other known naturally occurring transmissible cancer is an aggressive transmissible facial cancer in Tasmanian devils that is spread by biting.
“The genome of the transmissible dog cancer will help us to understand the processes that allow cancers to become transmissible,” said Professor Sir Mike Stratton, senior author and Director of the Sanger Institute.
“Although transmissible cancers are very rare, we should be prepared in case such a disease emerged in humans or other animals. Furthermore, studying the evolution of this ancient cancer can help us to understand factors driving cancer evolution more generally.”
Inset image: Elizabeth Murchison and Andrea Strakova, University of Cambridge and Genome Research Limited
Scientists have sequenced the genome of the world’s oldest continuously surviving cancer, a transmissible genital cancer that affects dogs.
Transmissible cancers in dogs and Tasmanian devils
Join Andrea Strakova for a talk which will reveal unexpected findings about two unique cancers which have adapted to transfer by the means of living cancer cells between their hosts – Tasmanian devils and domestic dogs. We will explore how a cancer can become transmissible, despite the fact that it is usually considered to be a malignant transformation of cells of your own body.
Fruit bat population covering central Africa is carrier of two deadly viruses
By sj387 from News feed generator. Published on Nov 19, 2013.
The study, conducted jointly by the University of Cambridge and the Zoological Society of London’s Institute of Zoology and published today in the journal Nature Communications, found that the “gregarious” bats span over 4,500 km of central Africa (around the distance from California to New York). The researchers also discovered that thirty-four per cent of the bats had been infected with Lagos bat virus, a disease similar to rabies, and 42 per cent had been infected with henipaviruses.
The African straw-coloured fruit bat (Eidolon helvum), which can live in roosts of over one million and often congregates near cities, was previously known to be a reservoir for these viruses, but it was not known to what extent.
For the study, the researchers tested over 2,000 bats in 12 different countries across Africa, measuring DNA from blood and tissue samples. They discovered that the bats were largely genetically similar, meaning that they travelled and mated across the continent without any evidence of population subgroups or specific migratory patterns – the largest example of this freely mixing population structure ever found in mammals. The species’ homogeneity and extensive movement means that the two viruses can be spread easily.
Professor James Wood, the study’s senior author from the University of Cambridge’s Department of Veterinary Medicine, said: “We now not only know how widespread viral infections are in this bat population, but we also know much more about its population structure. This new information indicates that the unique population of freely mixing bats across the entire continent facilitates the spread of the viruses. This has important implications for the monitoring of these viruses in order to prevent its spread to other animals, including humans.”
Fruit bats are often hunted for meat, a process which can result in a spill-over of these pathogens from animals to humans. Henipaviruses can also be spread through contact with urine and faeces. While no instances of either disease have been reported in humans in Africa, the viruses have previously been detected in pigs in Ghana. Henipaviruses have caused fatal disease in humans, pigs and horses in SE Asia and Australia.
Although potential human infection raises public health concerns, the study’s lead author, Dr Alison Peel, cautions restraint. She said: “Sometimes, a knee-jerk response can be to try and remove bats from urban areas via culling or dispersal. However, there is evidence to suggest that actions such as this can stress the bats and lead to a greater risk of spill-over. The most appropriate response is ongoing studies and public awareness to avoid handling bats, and to wash the wound thoroughly if you are bitten by a bat.”
A population of fruit bats which is found across much of continental Africa is widely infected with two deadly viruses that could spread to humans, new research reveals.
Sustainable livestock production is possible
By gm349 from News feed generator. Published on Sep 25, 2013.
Consumers are increasingly demanding higher standards for how their meat is sourced, with animal welfare and the impact on the environment factoring in many purchases. Unfortunately, many widely-used livestock production methods are currently unsustainable. However, new research out today from the University of Cambridge has identified what may be the future of sustainable livestock production: silvopastoral systems which include shrubs and trees with edible leaves or fruits as well as herbage.
Professor Donald Broom, from the University of Cambridge, who led the research said: “Consumers are now demanding more sustainable and ethically sourced food, including production without negative impacts on animal welfare, the environment and the livelihood of poor producers. Silvopastoral systems address all of these concerns with the added benefit of increased production in the long term.”
Current cattle production mostly occurs on cleared pastures with only herbaceous plants, such as grasses, grown as food for the cows. The effects on the local environment include the removal of trees and shrubs as well as the increased use of herbicides, all of which result in a dramatic decrease in biodiversity. Additionally, there is also contamination of soil and waterways by agricultural chemicals as well as carbon costs because of vehicles and artificial fertiliser necessary to maintain the pasture.
The researchers advocate that using a diverse group of edible plants such as that in a silvopastoral landscape promotes healthy soil with better water retention (and less runoff), encourages predators of harmful animals, minimizes greenhouse gas emissions, improves job satisfaction for farm workers, reduces injury and stress in animals, improves welfare and encourages biodiversity using native shrubs and trees.
Additionally, shrubs and trees with edible leaves and shoots, along with pasture plants, produce more food for animals per unit area of land than pasture plants alone. Trees and shrubs have the added benefit of providing shade from hot sun and shelter from rain. It also reduces stress by enabling the animals to hide from perceived danger.
“The planting as forage plants of both shrubs and trees whose leaves and small branches can be consumed by farmed animals can transform the prospects of obtaining sustainable animal production,” said Professor Broom. “Such planting of ‘fodder trees’ has already been successful in several countries, including the plant Chamaecytisus palmensis which is now widely used for cattle feed in Australia.”
Another success has been in Colombia where a mixed planting of the shrub Leucaena with a common pasture grass resulted in a 27% increase in dry matter for food and 64% increase of protein production.
When ruminants, such as cows, goats and sheep, are consuming the plants from a silvopastoral system, researchers have seen an increase in growth and milk production. Milk production in the tropical silvopastoral system mentioned above was 4.13 kg per cow when compared with 3.5 kg per day on pasture-only systems. As the numbers of animals per hectare was much greater, production of good quality milk per hectare was four to five times greater on the silvopastoral system.
One of the additional benefits of using the silvopastoral system is that it increases biodiversity. Biodiversity is declining across the globe, and the main culprit is farming – 33% of the total land surface of the world is used for livestock production. If farmers were to switch to sustainable livestock production methods, such as the silvopastoral system, the result would be much greater biodiversity with no increase in land use.
Professor Broom added: “It is clear that silvopastoral systems increase biodiversity, improve animal welfare and provide good working conditions while enabling a profitable farming business. The next step is to get farmers to adopt this proven, sustainable model.”
The paper ‘Sustainable, efficient livestock production with high biodiversity and good welfare for animals’ was published today, 25 September, in the journal Proceedings of the Royal Society B.
New research advocates use of pastures with shrubs and trees as it is more sustainable, improving animal welfare and increasing biodiversity.