Medium-sized dogs have a higher risk of developing cancer than the very largest or smallest breeds, according to a UC Riverside study. 

The study, published in the Royal Society Open Science, set out to test a model of how cancer begins. This model, called the multistage model, predicts that size is a risk factor for cancer. As it turns out, it is, but only when considering size variation within a single species. 

It is common for cells to acquire errors or mutations as they divide and form copies of themselves. Bigger animals, and those that live longer, have more cells and a longer lifespan during which those cells divide.  According to the multistage model, that means they have more opportunities to acquire mutations that eventually become cancer.

“The question that arises is why, then, don’t we get more cancer than a mouse? We don’t. There is no increase in cancer risk as animals increase in size from species to species,” said UC Riverside evolutionary biologist and study author Leonard Nunney. 

However, this isn’t true for animals of the same species. “Studies on humans show that tall people get more cancer than short people. It’s about a 10% increase over the baseline risk for every 10 centimeters in height,” Nunney said.

For more insight into these risk factors, Nunney required a species with a bigger difference between the smallest and biggest individuals. 

“Testing this in dogs is even better because you can compare a tiny chihuahua to a great Dane. That’s a 35-fold difference in size, and people can’t come close to that,” Nunney said. 

Surveying their mortality rates with three different data sets, Nunney found the smallest dogs, including Pomeranians, miniature pinschers, shih tzus and chihuahuas have about a 10% chance of dying from cancer. 

By comparison, many relatively large dogs, such as Burmese mountain dogs, have more than a 40% chance of death from cancer.   

There were some outliers in the study. Flat-coated retrievers had the highest mortality from cancer, getting a type of sarcoma with higher frequency than they should have for their size. Scottish terriers seemed to get more cancer than other small dog breeds. “Terriers in general get more cancer than expected for their size,” Nunney said. In general, however, the study supports the idea that size is a major risk factor for cancer. 

However, the very largest breeds, such as great Danes, have less cancer than medium-sized breeds. That is because of a well-known but as yet unexplained phenomenon: the life expectancy of dogs gets shorter with size. 

“For every pound increase in typical breed size you lose about two weeks of life. A very big dog, you’re lucky if they live past nine years, whereas small dogs can go about 14,” Nunney said.  Cancer is predominantly a disease of old age so by having a reduced lifespan the largest dogs have a reduced cancer risk.

According to the study, dog breeds are a clear fit with the multistage model of cancer acquisition that says larger size and longer lives offer more opportunities for cells to mutate. “I was surprised how well dogs fit the model,” Nunney said. “But that doesn’t happen when you compare a mouse to an elephant or a human to a whale. So, does that undermine the model in some way?” 

Nunney believes that an animal’s ability to avoid cancer increases with the size of the species. “My argument is that preventing cancer is an evolving trait, so a whale will have more ways of preventing cancer than a mouse does,” he said. 

While data are limited about the occurrences of cancer in whales, there is more information about rates in elephants, because they are kept in zoos. 

“Elephants don’t get much cancer. Their ancestors, long before mastodons, were much smaller, so how, en route to today’s size, did they avoid cancer?” he wondered. “The secret to preventing cancer could lie within the biology of larger animals.”

A study published in the journal Animal-Human Interactions reveals that emotional turmoil experienced by dog owners after their pet has been stolen is like that of losing a loved one such as a caregiver losing their child.

The findings empirically support the notions that the ‘owner’ or guardian roles and relationships equate to familial relationships and, when faced with the theft of their pet, owners feel a similar sense of disenfranchised grief and ambiguous loss.

In the study, some participants felt the loss was more intense than the death of a friend or relative owing to the closeness of the human-animal bond they had with their pet that in some cases, they did not have with some family members.

Akaanksha Venkatramanan and Dr Lindsey Roberts suggest sadness/sorrow, despair and hopelessness, and emotional pain and/or numbness, coupled with anxiety was consistently reported in the study; the same emotional reactions evident at the death of human loved ones but that the emotions were distinct owing to the difference in how society views the death of people versus our beloved companion animals or ‘pets.’

The psychological distress experienced was often made worse by a lack of understanding of how much an animal companion can mean to someone, and that dog theft laws often only consider dogs as stolen property in the same way as having a material possession such as bicycle stolen, because of this the Police are limited in the support they can offer too.

The situation can be made worse by the manner the dog was stolen too – either through physical force or entering someone’s own home or property without consent.

The researchers say that given the evidence of similar grief and coping markers to the loss of loved ones and children, dog owners are susceptible to developing challenges and delays processing their grief such as Post Traumatic Stress Disorder and Post Grief Disorder, as there is a real risk of having no closure from the event, particularly if the dog is never returned home or found deceased.

The researchers said the study also demonstrates that dog owners cope just as they would when missing a human family member has gone missing or passed but propose social media as a way of continuing the search for their pet, adapting to the new situation by reaching out to those in a similar situation, retaining hope, and/or attempting to cope with their grief and adjust to new circumstances without their dog.

Psychological research, the researchers say, should aim to inform best-practice resources providing suitable help managing grief, social disenfranchisement, and other psychological or physiological consequences of this trauma.

Ms Venkatramanan, an Assistant Psychologist, Berkshire Healthcare NHS Foundation Trust, said, “This study explored the experiences and needs of dog-guardians when faced with dog theft and the results validated an overlap of characteristics between human and non-human relationships.

“It provides evidence of the intense love of dogs and the parental accountability of guardians. A consequent overlap of emotional distress at the loss of this relationship is also shown, providing empirical evidence to formulate psychological and legal support to this, currently disenfranchised, grief experience.”

In the UK alone, there are 13 million dog owners. Having a pet has been found to improve physiological and psychological wellbeing – correlating to reduced cardiovascular mortality, depression, and stress levels. Dogs are a source of comfort to many, particularly for those who without them, would experience significant loneliness.

The researchers highlight how having a dog buffered against the negative impact of loneliness experienced during the COVID-19 lockdowns in the UK as dogs give people a reason to leave the house for walks, exercise and spend time in nature.

Sadly, the upshot of many more people raising dogs in this time resulted in a spike in breeding, a rise in the cost of puppies for sale and theft during the pandemic. While 3.2 million pets were bought during lockdown, there were also over 2,000 reports of dogs stolen – a rise in dog theft by 250% pre-Covid.

Four years since the onset of COVID-19, puppies and kittens adopted during the pandemic are now entering adulthood and pets adopted as adults are approaching their senior years. As a partner in complete pet care, Petco Health and Wellness Company Inc. is sharing veterinarian-recommended tips for supporting pets through life stage transitions.

“Just like humans, pets’ needs evolve throughout their lives and Petco offers the expertise, products and services essential to caring for their total wellness as they age,” said Petco’s Chief Veterinarian, Dr. Whitney Miller, DVM, MBA, DACVPM. “Across nutrition, activity level, veterinary care and more, puppies and kittens have very different needs from adult pets, and their needs change again as they become seniors. It’s critically important that pet parents understand the varying life stages and how they can help their pets live their healthiest, happiest lives at each milestone.”

Dr. Miller’s top tips include:

Vaccinations

Vaccines are an essential part of every pet’s whole health. Puppies and kittens will need extra attention in this area, but adult and senior dogs and cats still require regular vaccines to protect them from contagious diseases.

Regular Checkups

Schedule regular veterinary visits, at minimum once per year, to help prevent and identify conditions early. As pets enter their senior years, a trusted veterinarian can diagnose and treat issues to help pets live longer, healthier lives.

Nutrition

Pets’ nutritional needs change as they age. Puppies and kittens can benefit from unique calcium and phosphorous and specific formulations that help support their rapid growth and development. Adult pets may have new dietary sensitivities or needs and require a switch to a weight management or limited-ingredient food. As pets settle into their senior years, joint and fatty acid supplements can help ensure they are supporting mobility and skin and coat health. Petco offers a range of nutritional products to support every diet, budget and life stage.

Training

Training is a lifelong practice for pets, and pet parents should not stop at puppyhood. Behavioral issues can arise at any life stage, and it’s never too late to learn new skills. With patience and dedication, pet parents can help their pets adjust to new routines, especially if the past four years have increased their pet’s separation and social anxiety.

Grooming

A regular grooming routine is essential to maintaining a pet’s health & wellness. Not only will regular appointments keep pets looking their best throughout their lifetime but also targeted grooming packages can help address issues such as fleas, shedding and itching.

Home Integration

From puppy gates to a ramp for senior pets, it’s important to consider implementing simple adaptations at home to best support pets at each life stage. As dogs and cats age, they may get stiff laying on their old bed and feel more comfortable on an orthopedic bed. Both puppies and older dogs may need to have potty pads on hand, while adult dogs can benefit from engaging toys that help release their energy and strengthen cognition.

Safety Measures

One in three pets goes missing in their lifetime. Be sure to microchip pets, in addition to using an identification tag, for their safety. Also, register pets with a free national lost and found database that uses patented image-recognition technology to help reunite lost pets with their families. As more pet parents register their pets, this can help curb the increase in stray and lost pets coming into shelters across the country.