skip to primary navigationskip to content
 

2013

Fruit bat population covering central Africa is carrier of two deadly viruses

last modified May 27, 2016 12:05 PM
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.

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. Read more..

 

Sustainable livestock production is possible

last modified May 27, 2016 12:50 PM
New research advocates use of pastures with shrubs and trees as it is more sustainable, improving animal welfare and increasing biodiversity.

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. Read more..

New research reveals how cat dander triggers allergic responses

last modified May 27, 2016 12:09 PM
Immune system’s extreme reaction to cat allergen previously poorly understood; study could lead to new treatments for those with cat and dog allergies

New research reveals how the most common cause of severe allergic reactions to cats, the Fel d 1 protein which is found in cat dander, triggers an allergic response.

Scientists have discovered that when the cat protein Fel d 1 is in the presence of very low doses of the ubiquitous environmental bacterial toxin, lipopolysaccharide (LPS), it activates the pathogen recognition receptor Toll-like receptor 4. Until now, it was not understood how Fel d 1 generated such a large inflammatory response in the immune system.

Allergic reactions are the result of the immune system overreacting to a perceived danger. Instead of identifying and responding to a harmful virus or bacteria, it misidentifies different allergens, including dander (microscopic pieces of animal skin often accompanied by dried saliva from grooming), as dangerous and mounts an immune response.

In order to find out how Fel d 1 triggers these allergic reactions, the researchers exposed human cells to cat and dog dander proteins in the presence or absence of low levels of LPS. The researchers found that when the bacterial toxin LPS is present, it increases the signalling to the body’s immune system, intensifying the body’s inflammatory response to the cat protein Fel d 1.

They also discovered that the part of the immune system that recognises the LPS contaminated Fel d 1  is the pathogen recognition receptor Toll-like receptor 4 (TLR4). (TLR4 also plays a role in a heightened immune response, and subsequent allergic reaction, to dust mite allergens and as well as the metal nickel.) The researchers then used a drug which inhibits the TLR4 response and found that it blocks the effects of the cat dander protein on human cells, thereby preventing an inflammatory response.

Dr Clare Bryant, lead author of the research from the University of Cambridge’s Department of Veterinary Medicine, said: “How cat dander causes such a severe allergic reaction in some people has long been a mystery. Not only did we find out that LPS exacerbates the immune response’s reaction to cat dander, we identified the part of immune system that recognises it, the receptor TLR4.”

Read more..

African Horse Sickness: mapping how a deadly disease might spread in the UK

last modified May 27, 2016 12:11 PM
A disease lethal to horses, until now confined to hot countries, could arrive in the UK. New research creates a picture of its possible spread and pinpoints the area that would be worse hit.

As its name suggests, African Horse Sickness (AHS) is associated with the continent of Africa, where it is feared as a deadly disease. It has long been assumed by British veterinarians and horse-owners that the disease, which is carried by midges, could not spread to cooler northern climates.

But researchers now think that its arrival in northern Europe could be only a matter of time – and perhaps more importantly, that it could spread if it did arrive.

A study undertaken by scientists at the University of Cambridge Department of Veterinary Medicine, in collaboration with the Animal Health Trust and The Pirbright Institute, shows how dangerous it could be for the horse and pony population if AHS was introduced into the UK. The research also identified which regions would be worst hit at different times of the year. 

This information could be vital to strategies for coping with an outbreak if it arrived. The study also emphasises the importance of the continued exclusion of the disease.

The research was led by Dr Gianni Lo Iacono, a multidisciplinary scientist whose expertise lies in the mathematical modelling of a range of problems related to the interface between biology and physics. He worked with a team of colleagues from complementary fields including Professor James Wood, a renowned specialist in infectious diseases.

Most strikingly, East Anglia emerges from the study as the region that is most vulnerable to AHS spread which could occur if the disease was not identified early enough for action to be taken to contain it.

Read more.. 

New study shows how Salmonella colonises the gut

last modified May 27, 2016 12:13 PM
Researchers plan to use data collected to develop vaccines to control Salmonella in animals and humans

Salmonella is a major cause of human diarrhoeal infections and is frequently acquired from chickens, pigs and cattle, or their products. Around 94 million such infections occur in people worldwide each year, with approximately 50,000 cases in the UK per annum.

In a BBSRC-funded collaboration between the University of Cambridge’s Department of Veterinary Medicine, the University of Edinburgh’s Roslin Institute and the Wellcome Trust Sanger Institute, scientists have studied how Salmonella colonises the intestines of food-producing animals. This is relevant both to the welfare of the animal hosts and to contamination of the food chain and farm environment.

To unravel how Salmonella persists in farm animals, the scientists studied the role of thousands of its genes. Using a novel DNA-sequencing method the team screened 10,000 mutants of Salmonella for their ability to colonise the guts of chickens, pigs and cattle.  This was achieved by using a novel technique based on high-throughput DNA sequencing which enabled the screening of 475 mutants of the bacteria per single animal. In the process, they assigned roles in infection to over 2700 Salmonella genes in each of the farm animal hosts. This has yielded roles for over half the genetic instructions of the bacterium and is by far the most comprehensive survey for any pathogen in its natural hosts to date.

Professor Duncan Maskell at the University of Cambridge said, “We found that hundreds of genes are important for colonisation; this provides vital new data for the design of strategies to control Salmonella in animals and reduce transmission to humans. Our data indicate that Salmonella contains a core set of genes that is important when it infects all three hosts, but that there are smaller sets of genes that are required for infection of each individual host species.”

Professor Mark Stevens at The Roslin Institute added, “We are always trying to develop new ways of reducing the number of animals used in experiments. The methods we applied allowed us to survey the fate of hundreds of bacterial mutants simultaneously in one animal, rather than us having to test them one-by-one. This represents a significant advance in the study of microbial diseases, and can be applied to other pathogens and host animals.”

The team now plans to use the data it has collected to design vaccines or treatments to reduce the burden of salmonellosis in animals and humans.

Read more..

New research suggests animal-to-human transmission of MRSA

last modified May 27, 2016 12:14 PM
Using whole genome sequencing, scientists have found two independent human cases of infection have been linked to livestock.

Cambridge scientists have linked two human cases of infection with the antibiotic- resistant superbug MRSA to farms in Denmark. The results of the study, published today in the journal EMBO Molecular Medicine, suggest the methicillin-resistant Staphylococcus aureus (MRSA) bacteria was transmitted from the livestock to the farmers.

The type of MRSA which was found in both of the human cases was only discovered two years ago by Dr Mark Holmes and his colleagues from the University of Cambridge. The new strain’s genetic makeup differs greatly from previous strains, which means that the ‘gold standard’ molecular tests currently used to identify MRSA - a polymerase chain reaction technique (PCR) and slide agglutination testing - do not detect it.

For this study, the scientists used whole genome sequencing to investigate two cases of the new MRSA where the patients lived on farms to see if the same strain could be found in the animals on the farm.

Dr Holmes, from Cambridge’s Department of Veterinary Medicine and the senior author on the paper, said: “Having found this new MRSA in both people and animals on the same farm it was likely that it is being transmitted between animals and people.

“By looking at the single differences in nucleotides, or SNPs, in the DNA sequences of each isolate, it became obvious that in both farms we looked at the human and animal MRSA were almost identical. In one case, the results also clearly showed that the most likely direction of transmission was from animal to human.”

The study raises questions about whether cows could be a reservoir for new strains of MRSA. It was previously not clear whether MRSA was transmitted to cows from humans or to humans from cows, but the new research indicates that the livestock is the likely source of these new strains.

“Our findings demonstrate that the MRSA strains we studied are capable of transmission between animals and humans, which highlights the role of livestock as a potential reservoir of antibiotic resistant bacteria,” remarked Dr Ewan Harrison, a post-doctoral research associate at the University of Cambridge’s Department of Veterinary Medicine and co-author of the paper.

Read more..

March of the superbugs

last modified May 27, 2016 12:17 PM
Scientists who recently discovered a new strain of superbug have now tracked its transmission between animals and humans.

Every so often, research laboratories and hospitals testing patients for the superbug methicillin-resistant Staphylococcus aureus (MRSA) have come across an oddity: a strain that appeared to be MRSA because it was resistant to antibiotics but one that tested negative with the ‘gold standard’ molecular test. The quirky cases were so infrequent that they were usually filed away for future analysis or disregarded. Until, that is, PhD student Laura Garcia-Alvarez from Cambridge’s Department of Veterinary Medicine had the tenacity to look a little further at a bacterial strain she had spotted in cows’ milk.

MRSA first appeared in 1961 and epidemic strains of this difficult-to-treat bacterium have since spread worldwide in hospitals and the community. In the farming world, MRSA causes bovine mastitis – an infection of cows’ udders – affecting both animal welfare and milk yields.

Garcia-Alvarez was working with Dr Mark Holmes on bovine mastitis when she came across one of the ‘curious anomalies’. The strain was resistant to antibiotics but in the standard molecular test was negative for the presence of mecA – the gene responsible for methicillin resistance. She had the isolates retested and then sequenced at the Wellcome Trust Sanger Institute.

It turned out that she had discovered a new strain of MRSA. Its antibiotic resistance is carried not by mecA but by mecC, a gene that is so genetically dissimilar to mecA that it can’t be picked up by the standard molecular test used to define MRSA but only by DNA sequencing.

As Holmes and Garcia-Alvarez began to spread the information to colleagues around Europe, it soon became clear that this phenomenon was not confined to cows: others had found the unusual samples in humans. “We started to get calls from hospitals and research groups who had come across a small number of human MRSA strains that behaved differently,” said Holmes. “Within a few weeks, we had a further 50 isolates. This meant that what we were looking at was a human problem too.”

Garcia-Alvarez, who at the time was a student on the Department’s postgraduate training in infectious disease dynamics programme, described how finding the same new strain in both humans and cows was worrying, although no cause for immediate alarm: “Pasteurisation of milk will prevent any risk of infection via the food chain. In the wider UK community, less than 3% of individuals carry MRSA – typically in their noses – without becoming ill.”

“Nonetheless,” added Holmes, “MRSA presents a major challenge to the control of infectious diseases. Finding a new strain – studying its prevalence, how it confers antibiotic resistance and how it’s transmitted – can tell us enormous amounts about the origins and evolution of antibiotic resistance.”

Read more..