̽��ֱ�� of Cambridge - Andrea Strakova

Male dogs four times more likely to develop contagious cancer on nose or mouth than females

jg533 — Sun, 03 Jul 2022 23:01:00 +0000

A new study has found that male dogs are four to five times more likely than female dogs to be infected with the oro-nasal form of Canine Transmissible Venereal Tumour.

Researchers think this is because of behavioural differences between the sexes: male dogs spend more time sniffing and licking female dogs’ genitalia than vice versa.

Canine Transmissible Venereal Tumour, or CTVT, is an unusual cancer – it is infectious and can spread between dogs when they come into contact. ̽��ֱ��living cancer cells physically ‘transplant’ themselves from one animal to the other.

CTVT commonly affects dogs’ genitals and is usually transmitted during mating. But sometimes the cancer can affect other areas like the nose, mouth and skin.

In the study, the researchers reviewed a database of almost 2,000 cases of CTVT from around the globe and found that only 32 CTVT tumours affected the nose or mouth. Of these, 27 cases were in male dogs.

“We found that a very significant proportion of the nose or mouth tumours of canine transmissible cancer were in male dogs,” said Dr Andrea Strakova in the ̽��ֱ�� of Cambridge’s Department of Veterinary Medicine, first author of the paper. She performed this study with colleagues from the Transmissible Cancer Group, led by Professor Elizabeth Murchison.

Strakova added: “We think this is because male dogs may have a preference for sniffing or licking the female genitalia, compared to vice versa. ̽��ֱ��female genital tumours may also be more accessible for sniffing and licking, compared to the male genital tumours.”

̽��ֱ��findings are published today in the journal Veterinary Record.

CTVT first arose several thousand years ago from the cells of one individual dog; remarkably, the cancer survived beyond the death of this original dog by spreading to new dogs. This transmissible cancer is now found in dog populations worldwide, and is the oldest and most prolific cancer lineage known in nature.

CTVT isn’t common in the UK, although case numbers have risen in the past decade. This is thought to be linked to the import of dogs from abroad. ̽��ֱ��disease occurs worldwide but is mostly linked to countries with free-roaming dog populations.

“Although canine transmissible cancer can be diagnosed and treated fairly easily, veterinarians in the UK may not be familiar with the signs of the disease because it is very rare here,” said Strakova.

She added: “We think it’s important to consider CTVT as a possible diagnosis for oro-nasal tumours in dogs. Treatment is very effective, using single agent Vincristine chemotherapy, and the vast majority of dogs recover.”

̽��ֱ��most common symptoms of the oro-nasal form of the cancer are sneezing, snoring, difficulty breathing, nasal deformation or bloody and other discharge from the nose or mouth.

Genital cases of CTVT occur in roughly equal numbers of male and female dogs.

Transmissible cancers are also found in Tasmanian Devils, and in marine bivalves like mussels and clams. ̽��ֱ��researchers say that studying this unusual long-lived cancer could also be helpful in understanding how human cancers work.

̽��ֱ��research was funded by the Wellcome and International Canine Health Postgraduate Student Inspiration Awards from the Kennel Club Charitable Trust.

Reference

Strakova, A et al: ‘Sex disparity in oronasal presentations of canine transmissible venereal tumour.’ Veterinary Record, July 2022. DOI: 10.1002/vetr.1794

Sniffing or licking other dogs’ genitalia – the common site of Canine Transmissible Venereal Tumour – can spread this unusual cancer to the nose and mouth.

Although canine transmissible cancer can be diagnosed and treated fairly easily, vets in the UK may not be familiar with the signs of the disease because it is very rare here

Andrea Strakova

CTVT Oronasal Tumours Animation Credit Emma Werner

Jan Allen, AMRRIC

Free-roaming dog.

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A shaggy dog story: ̽��ֱ��contagious cancer that conquered the world

cjb250 — Mon, 16 May 2016 23:01:16 +0000

‘Canine transmissible venereal tumour’ (CTVT) is a cancer that spreads between dogs through the transfer of living cancer cells, primarily during mating. ̽��ֱ��disease usually manifests as genital tumours in both male and female domestic dogs. ̽��ֱ��cancer first arose approximately 11,000 years ago from the cells of one individual dog; remarkably, it survived beyond the death of this original dog by spreading to new dogs. ̽��ֱ��cancer is now found in dog populations worldwide, and is the oldest and most prolific cancer lineage known in nature.

In a study published today in the journal eLife, an international team led by researchers at the ̽��ֱ�� of Cambridge studied the DNA of mitochondria – the ‘batteries’ that provide cells with their energy – in 449 CTVT tumours from dogs in 39 countries across six continents. Previous research has shown that at occasional points in history, mitochondrial DNA has transferred from infected dogs to their tumours – and hence to tumour cells in subsequently-infected dogs.

In the new study, the researchers show that this process of swapping mitochondrial DNA has occurred at least five times since the original cancer arose. This discovery has allowed them to create an evolutionary ‘family tree’, showing how the tumours are related to each other. In addition, the unusual juxtaposition of different types of mitochondrial DNA within the same cell unexpectedly revealed that cancer cells can shuffle or ‘recombine’ DNA from different mitochondria.

“At five distinct time-points in its history, the cancer has ‘stolen’ mitochondrial DNA from its host, perhaps to help the tumour survive,” explains Andrea Strakova, from the Department of Veterinary Medicine at the ̽��ֱ�� of Cambridge, co-first author of the study. “This provides us with a set of unique genetic tags to trace how dogs have travelled the globe over the last few hundred years.”

In the evolutionary ‘family tree’, the five main branches are known as ‘clades’, each representing a point in history when mitochondria transferred between dog and tumour. By mapping tumours within these clades to the geographical location where they were found, the researchers were able to see how the cancers have spread across the globe. ̽��ֱ��distance and speed with which the clades have spread suggests that the dogs commonly travelled with human companions, often by sea.

One branch of the CTVT evolutionary tree appears to have spread from Russia or China around 1,000 years ago, but probably only came to the Americas within the last 500 years, suggesting that it was taken there by European colonialists. Conquistadors are known to have travelled with dogs – contemporary artworks have portrayed them both as attack dogs and as a source of food.

Image: 1598 fictional engraving by Theodor de Bry supposedly depicting a Spaniard feeding Indian children to his dogs. Wikipedia

̽��ֱ��disease probably arrived in Australia around the turn of the twentieth century, most likely imported inadvertently by dogs accompanying European settlers.

One of the most surprising findings from the study related to how mitochondrial DNA transfers – and mixes – between the tumour and the host. ̽��ֱ��researchers found that mitochondrial DNA molecules from host cells that have migrated into tumour cells occasionally fuse with the tumour’s own mitochondrial DNA, sharing host and tumour DNA in a process known as ‘recombination’. This is the first time this process has been observed in cancers.

Máire Ní Leathlobhair, the study’s co-first author, explains: “Mitochondrial DNA recombination could be happening on a much wider scale, including in human cancers, but it may usually be very difficult to detect. When recombination occurs in transmissible cancers, two potentially very different mitochondrial DNAs – one from the tumour, one from the host – are merging and so the result is more obvious. In human cancer, the tumour’s mitochondrial DNA is likely to be very similar to the mitochondrial DNA in the patient’s normal cells, so the result of recombination would be almost impossible to recognise.”

Although the significance of mitochondrial DNA recombination in cancer is not yet known, its discovery is now leading scientists to explore how this process may help cancer cells to survive – and if blocking it may stop cancer cells from growing.

Dr Elizabeth Murchison, senior author of the study, said: “ ̽��ֱ��genetic changes in CTVT have allowed us to reconstruct the global journeys taken by this cancer over two thousand years. It is remarkable that this unusual and long-lived cancer can teach us so much about the history of dogs, and also about the genetic and evolutionary processes that underlie cancer more generally.”

̽��ֱ��research was funded by the Wellcome Trust, the Leverhulme Trust and the Royal Society.

Reference
Strakova, A et al. Mitochondrial genetic diversity, selection and recombination in a canine transmissible cancer. eLife; 17 May 2016; DOI: 10.7554/eLife.14552

A contagious form of cancer that can spread between dogs during mating has highlighted the extent to which dogs accompanied human travellers throughout our seafaring history. But the tumours also provide surprising insights into how cancers evolve by ‘stealing’ DNA from their host.

It is remarkable that this unusual and long-lived cancer can teach us so much about the history of dogs, and also about the genetic and evolutionary processes that underlie cancer more generally

Elizabeth Murchison

Mitochondrial genetic diversity, selection and recombination in a canine transmissible cancer

̽��ֱ�� of Cambridge

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Global snapshot of infectious canine cancer shows how to control the disease

cjb250 — Wed, 03 Sep 2014 03:00:00 +0000

̽��ֱ��survey of veterinarians across the world confirmed that Canine Transmissible Venereal Tumour (CTVT) has a global reach. Researchers from the ̽��ֱ�� 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. ̽��ֱ��replies showed that CTVT is endemic in dogs in at least 90 of 109 countries surveyed.

̽��ֱ��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.”

̽��ֱ��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.

̽��ֱ��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.

Reference
Andrea Strakova and Elizabeth Murchison. ̽��ֱ��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.

̽��ֱ��disease was eradicated in the UK during the twentieth century, probably as an unintentional result of the introduction of dog control policies

Elizabeth Murchison

Jelly Dude

Nap Time

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