06/14/16

New Research on Early Neutered German Shepherds and Joint Disorders

New Research on Joint Disorders in German Shepherds

 

ResearchBlogging.orgIt’s very exciting how there is growing research on desexing in dogs, including age of neutering, and its implications on health. In the past, I have blogged on how desexing in German Shepherds is linked to reactivity. The latest study, published last month, looks at bone disorders, cancers, urinary incontinence, and pyometra in German Shepherds.

Many of the arguments for desexing dogs has been around population control instead of health matters – but obviously health does matter. We want dogs to be healthy.

This retrospective study looked at the health of 1170 German Shepherds. It included the analysis of vet records over 14.5 years (2000-2014). For each incidence of disease, the dogs’ records were followed for eight years, except in the case of mammary cancer, which was followed for eleven years. The data on the incidence of joint disorders and cancers in the German Shepherds was compared beside their sexes, and their neuter-age.

 

Joint Disorders

The biggest problem with early aged desexing in this breed, according to this study, is an increased risk of joint disorders. For example:

  • 6.6% of intact males had one or more joint disorders, but for dogs that were desexed before 6 months, 20.8% had one or more joint disorder. So joint disorder incidence was three times greater in dogs desexed before 6 months than intact dogs. For dogs that were desexed between 6-12 months, the incidence of at least one bone disorder was 16.4%.
  • Similarly, 5.1% of intact female had one or more joint disorders, but for bitches that were desexed before 6 months the incidence was 12.5%, and for bitches that were desexed at 6-11 months the incidence was 17%.
  • Of the joint disorders considered, Cranial Cruciate Ligament Tear was most highly correlated with early desexing. In entire dogs, hip dysplasia was most commonly seen.
  • For desexed dogs, rates of hip and elbow dyplasia was greater than entire dogs, but this difference was not statistically significant.
  • There was no difference between the body condition scores (i.e. fatness) between entire and neutered populations – so it’s not obesity that has caused these problems.

 

But why do German Shepherds have an increased incidence of joint disorders when they’re desexed before one year of age?

If a dog is desexed before one year of age, the growth plates of the dog are unlikely to have closed. (That is, the bones are still growing.) With the removal of hormone cues through the removal of gonads, the bones are likely to grow longer than they ‘should’, which disrupts joint alignment. This disruption leads to joint disorders such as those found in this and similar studies.

However, this research did not just look at bone disorders.

 

Cancer

Unlike previous studies on cancer in other breeds, there was no statistically significant differences between neutered and entire animals. However, in terms of mammary cancer (which was only considered in bitches), 4% of intact females got mammary cancer, but <1% got mammary cancer if desexed before one year of age. The paper notes that mammary cancer seems to be uncommon in German Shepherds and refers to a recent meta-analysis that found the protective factor of neutering in terms of mammary cancer to be weak.

In terms of other cancers there was no significant differences. (My own note though: This study found that only 14% of the entire bitches were used for breeding. Lactating is a protective factor against mammary cancer, so I would suspect that if more of these bitches were breeding bitches, the rate of mammary cancer may have been lower again.)

 

Bitch-Specific Conditions

Urinary incontinence was seen at a rate of 7% in neutered bitches, but was not seen at all with entire bitches. (Urinary incontinence was not considered in males.) The mean age of onset of urinary incontinence in early neutered females was 5.2 years.

Pyometra in intact females was seen as a rate of 2.5%.

How does this compare to other research?

It’s important to note that this new data adds to our growing understanding of desexing implications. This study references:

  • A 2014 study saw that Golden Retrievers and Labrador Retrivers were, generally, more likely to have a joint disorder the earlier they were desexed.
  • A 2013 study saw that Golden Retrievers that were early desexed had more hip dysplasia, cranial cruciate ligament tears, and lymphosarcoma. Desexing, regardless of time, increased the rate of at least one cancer by 3-4 times.
  • Another 2013 study found that, in Vizslas, the incidence of cancers was high in desexed dogs (except mammary cancer – where incidence was low).
  • Another 2013 study found that neutered male and female dogs were more likely to die of cancer than intact dogs.
  • A 2011 study that found that, in several breeds, the incidence of mast cell tumours was four times greater in spayed females as opposed to intact.
  • A 2008 study that saw that desexing before 12 months of age saw joint disorders (such as hip dysplasia, cranial cruciate ligament tears, and elbow dysplasia) occuring at 2-3 times higher rates than in intact dogs.
  • A 2007 study linked early desexing with risk factors for cranial cruciate ligament tears.
  • A 1999 study found that cardiac hemangiosarcoma was four times more common in spayed females than those intact.
  • A 1998 study, looking at several breeds, saw that osteosarcoma was two times more likely in neutered dog compared to intact dogs.
  • A 1988 study that found that splenic hemangiosarcoma was two times more likely in spayed females than intact.

The researchers involved with this study have been adding great data to the neutering/spaying discussion. They have previously published articles on Labrador vs Golden Retrievers and Golden Retrievers, and these articles had similar findings. (Though German Shepherds did not seem to be as cancer prone as the Golden Retrievers.) As all these studies are using vet clinic data, it is not known how similar or dissimilar the strains/lines are – so the sample could be genetically diverse despite being the same breed.

But it seems that, for German Shepherds, it is far better to wait until dogs are twelve months or older before desexing, if desexing is chosen at all. I’ll end on a quote from the paper:

As shown in this study, delaying neutering until the dog is at least a year of age appears to avoid the increase in risks of joint disorders is associated with neutering. This is a consideration for joint disease control that is immediately available.

 

Reference:
Hart, B., Hart, L., Thigpen, A., & Willits, N. (2016). Neutering of German Shepherd Dogs: associated joint disorders, cancers and urinary incontinence Veterinary Medicine and Science DOI: 10.1002/vms3.34

 

Further Reading:

Early Neutering Poses Health Risks for German Shepherd Dogs, Study Finds

A Link Between Desexing and Reactivity

Labs and Goldens: Goldens Get Cancer Better

Desexing: It’s bad for Vizslas, too

But Mammary Cancer!

Why would you NOT desex your dog?

06/24/15

My Say: Mandatory Desexing

(This is the last post in a four part series on dog and cat reforms in South Australia. See post one here, post two here, and post three here.)

Screen shot of the YourSAy website.The YourSay website invites submissions to a citizen’s jury. While we could discuss the validity of allowing (quote) “32 ordinary South Australians” to decide on whether various animal species should undergo the medical procedure of a gonadectomy… Unfortunately, this process has already been decided on, and hence we must make a submission according to this format.

When accessing the site, you will need to download a word document to make a submission. It is only on this document do we get the date that submissions are due in by: Friday 10th July 2015

This form also asks the question:

Last year in South Australia over 10,000 unwanted dogs and cats were put down.
The State Government recently announced some reforms to dog and cat laws.
What further measures can we introduce or trial to reduce the number of unwanted pets?

While the downloaded word document doesn’t explicitly mention desexing, the site does with the comment:

The government has also sought a specific verdict from the Jury on the matter of whether de-sexing should be mandatory.

The form also specifies that the your submission should not be more than two pages, and yet asks for examples to be provided… It’s an impossibility to provide ample compelling evidence in these narrow frames.

However, my response (which you are, as always, welcome to use in shaping your own) is below:

I am adamantly opposed to mandatory desexing. The reasons for this opposition are:

 

Mandatory desexing has not been shown to reduce the incidence of euthanasia in animal shelters. In areas where it has been implemented, often there is a subsequent increase in the number of animals entering the facility, as people are financially unable to desex their pets and, to avoid risk of prosecution, they choose to relinquish them. Internationally this affect has been seen Los Angeles and, more locally, in Western Australia. Mandatory desexing has actually been demonstrated to increase euthanasia, and therefore should not be an option for South Australia on this basis alone.

 

However, mandatory desexing is a move that is rejected by the Australasian Veterinary Association (AVA). The AVA represents veterinarians across Australia, and so it would be sensible for policy makers to develop legislation that corresponds with statements made by this peak body. Additionally, it is anticipated that veterinarians would be responsible for performing desexings (mandatory or otherwise), and so their support is crucial for successful implementation of mandatory desexing. Considering that veterinarians have significant financial gains to be made from such a policy, yet choose to reject it is, is an indicator of the lack-of-support for mandatory desexing.

 

Finally, and crucially, there is evidence that desexing in dogs can pose some health risks to animals. These risks include:

  • Increased incidence of some cancers (including mast cell tumours, hemangiosarcoma, lymphoma, osteosarcoma, and lymphosarcoma),
  • Higher incidence of joint disorders (including hip dysplasia and cranial crucial ligament tears), and
  • Increased incidence of behavioural problems (including reactivity, aggression, and anxiety, storm phobias).

Studies that indicate these problems have been published in peer-reviewed academic journals, illustrating that this is not ‘sensationalised’ content, but the results of real research on dog populations. Considering the available evidence, it seems immoral and contradictory to animal welfare goals to obligate pet owners to subject their animals to such risks.

 

As alternative means to reducing the number of unwanted pets, there are a number of approaches that could be trialled. The most obvious would be requiring improvements in reclaims. For many animals entering shelters, they have homes that want to get them home. Unfortunately, the large shelters in Australia are not proactive in listing impounded animals. This makes it difficult for owners to know where their pet is to bring them home. Further, if they do visit a facility to reclaim their pet, many times there are large fees that they are required to pay to get the impounded animal out. This is a barrier to individuals getting their pets home, while if they stay at the shelter they may be at risk of euthanasia. An additional barrier is poor opening times of this facility, meaning in many cases animals have to stay in the shelter longer due to their owner’s inability to access the facility. In summary, the procedure for individuals reclaiming animals needs to be improved by:

  • Impound facilities clearly listing all impounded animals online.
  • Legally enforceable guidelines regarding the scanning of microchips and the use of the information to find the owner.
  • Fees and charges for the release of impounded animals being reduced, waived, or available on a payment plan.
  • Impound facilities having opening times that make them highly accessible to the public.

 

Other changes that could be made at a shelter level to reduce euthanasia include:

  • Oreo’s Law – the requirement that animals are not euthanised if there is any individual or group who is willing to take them.
  • Mandated time for adoption – require facilities to offer all animals for adoption for a set period, perhaps 72 hours.

 

Finally, a big reason that animals end up in shelters is due to owner accommodation issues. This includes those who are renting, or fleeing their home due to violence.  If we deal with human issues, people will be more likely to retain their pets. Changes that encourage landlords to permit pets, and providing temporary accommodation that allow pets, are important to prevent animals being relinquished to shelters.

 

In summary, suggestions for reducing shelter euthanasia include:

  • Creating legislation that requires shelters to:
    • Do more to assist reclaims,
    • Allow adoptions for animals who have no choice but euthanasia, and
    • Allow all animals to be available for adoption for a minimum period of time.
  • And dealing with community issues surrounding owner accommodation issues.

 

Further reading:

“Just stop breeding until the pounds are empty”

Is desexing a cult?

Why would you NOT desex your dog???

Are you willing to be wrong about that?

 

 

 

02/18/15

But Mammary Cancer!

ResearchBlogging.org

A common justification for early neutering of bitches is that it protects against mammary neoplasia. However, many frequently cited references are over 40 years old, and this evidence has not been scrutinised with the benefit of recent developments in epidemiological methods and knowledge of potential confounders of the association between mammary masses and neutering, such as age, breed and treatment with synthetic derivatives of ovarian steroids.

One of the most frequently presented arguments for desexing is ‘mammary cancer’. It is commonly stated that desexing bitches reduces the risk of mammary cancer.

But as always, we must ask: What does the research say?

I love to answer questions like this, and so I have read quite a bit of research on mammary cancers in bitches. However, despite doing lots of reading, none of these research papers have made their way to my blog.

The reason? The research is very old and I am not compelled to review or examine such ancient research.

Why does old research matter? It’s easy to say that ‘biology doesn’t change’, and if it was so in the 1970s, then it must be so now. While that’s the case, our understanding on research methods and limitations is continuing to improve.

Regardless, even if we say that the research from the 1970s is as accurate as ever, compelling results are those that are replicated. While it’s nice to get one study that shows a link between mammary cancer and sex hormones, we need multiple studies with large sample sizes to prove this without doubt.

Using the studies considered in Beauvais et al’s 2012 systematic review, since the 1960s, there has been approximately fifteen (15) studies on mammary cancer in the bitch. That is, the last fifty-five (55) years, there has been one study on mammary cancer in dogs in ever four yearsThere are very few papers on mammary cancer, and those that do exist do not replicate past results.

So how old is the mammary cancer research? 

Beauvais et al.'s references in their systematic review on mammary tumours in bitches as affected by spaying.

Beauvais et al.’s references in their systematic review on mammary tumours in bitches as affected by spaying.

Again, if we use the studies considered in Beauvais et al’s 2012 systematic review, there were fifteen studies in all considered. Of those studies, only one (1) of those studies was completed in the last ten years. Further, eighty-six percent (86%) of the studies are more than fifteen (15) years old. So, basically: the research is old!

Nothing excites me like a review on literature. (You can imagine what I’m like at parties.) When I noticed a systematic review by Beauvais et al. on mammary cancer in dogs (published in 2012), I was excited as I hoped I would find some more recent studies. The study did not fulfil my hopes, and so I am left believing that more recent research simply doesn’t exist.

Interestingly, the researchers made comment that a systematic review (like they produced) had seemingly not been covered before. A systematic review is used to evaluate the strength of evidence and to consider bias. This type of research is common in medical literature, but not so much in veterinary.

The researchers considered the quality of the research for thirteen reports and found “Nine were judged to have a high risk of bias. The remaining four were classified as having a moderate risk of bias.” Indeed, some studies made claims (e.g. that neutering had a ‘protective effect’) but then failed to back up these claims with evidence.

Considering that only one study found an association between neutering and reduced risk of mammary tumours, and two studies found no evidence, there is not strong evidence that desexing reduces the risk of mammary tumours.

Check out the mammaries! My girl, Myrtle, is due to whelp in a week's time.

Check out the mammaries! My girl, Myrtle, is due to whelp in a week’s time.

What does the evidence say? 

Our results suggest that there is some evidence in one study that neutering is associated with a reduction in the risk of malignant mammary tumours (approximately 10-fold), amongst dogs from which samples and been submitted for histopathology, although there was no evidence that neutering after 2.5 years of age is associated with any change in the risk of malignant mammary tumours.

Basically, they concluded that there is weak evidence and there is “not a sound basis for firm recommendations“. There is some evidence that desexing before 2-5 years of age is beneficial, and also evidence that desexing before their first season may be beneficial.

The biggest faults in the existing research identified by Beauvais et al. included:

  • Research failed to control for age or breed.
  • No indication of age at neutering.
  • Little numerical data provided in publications (which limited this retrospective study).
  • Lack of consideration to bitches treated with ovarian steroids (and the effects this may have on research.)

When it comes to spaying bitches, it is important to recognise that the implications of a gonadecmomy on many aspects of the bitch. Not only does desexing affect the health and temperament of that bitch, there may be wider implications on the general population.

At the moment, vets vary in their opinion and recommendations, especially by country. I encourage owners to do their own research when making decisions for their pets.

 

 
Further Reading:Beauvais, W., Cardwell, J., & Brodbelt, D. (2012). The effect of neutering on the risk of mammary tumours in dogs – a systematic review Journal of Small Animal Practice, 53 (6), 314-322 DOI: 10.1111/j.1748-5827.2011.01220.x

09/3/14

A Link Between Desexing and Reactivity

ResearchBlogging.orgWhile desexing bitches is a common surgery, I was pleased to see Kim et al. take note that “the side effects of the operation, particularly any changes in behaviour, have been quantified in only few studies”.

That is to say, despite us commissioning vets to take the ovaries and uterus out of a great many bitches, we don’t really have much research about it. It’s a pretty scary state of play.

This particular study took 14 healthy German Shepherd bitches, between 5 and 10 months old. Half of these dogs were spayed, and the other half left entire. (The bitches were assigned to each group randomly, except for litter sisters, which were assigned opposite groups.)

After the spay, and having been given 4-5 months to recover from the surgery, the bitches were filmed in their kennel as a stranger and a dog approached. This footage was then scored based on how reactive the bitch was. A score of ’3′ indicated severe reactivity, and a score of ’0′ indicated no reactivity. The scorer was unaware of whether the bitch was spayed or not.

Photo courtesy of Rachel Willis.

Photo courtesy of Rachel Willis.

The reactivity of each bitch was recorded several times, and the reactivity of each bitch declined over the study. It’s likely that the bitches habituated to the novel stimuli. However, despite this affect, bitches in the ovary-hysterectomy group scored higher throughout the study.

Before generalising these results, there are some matters to consider:

  • Reactivity was only measured in a kennel setting, and how these dogs react in the ‘real world’ may be different. We can’t suppose that our pet dogs are going to respond in the same way as kennel dogs.
     
  • The reactivity of these dogs was not measured at the start of the study. While it is unlikely, perhaps more reactive dogs happened to fall into the treatment group by chance. Without a ‘before desexing’ score, we cannot be sure of this.
     
  • The authors make note that these results are for German Shepherd bitches aged 5-10 months old. We can’t assume dogs of all breeds and ages would respond this way to spays.
     
  • Further, the bitches in this study are working lined German Shepherds, which may be more reactive than the typical pet dog.

 

However, this study notes that other studies on bitch spays have shown that as a group spayed bitches are:

  • More likely to gain weight
  • More aggressive than prior to spay (if they were aggressive prior to spay)
  • More active
  • More likely to have urinary incontinence
  • More likely to be reactive after surgery

 

The authors recommend:

[V]eterinary practitioners should inform owners that a bitch may become more reactive after spaying either because they have lost the calming effects of progesterone or because elevated gonadotropins stimulate release of adrenal androgens.

 
Source:
Kim HH, Yeon SC, Houpt KA, Lee HC, Chang HH, & Lee HJ (2006). Effects of ovariohysterectomy on reactivity in German Shepherd dogs. Veterinary journal (London, England : 1997), 172 (1), 154-9 PMID: 16772140

Further reading:
Desexing: It’s bad for Vizslas too
Is desexing a cult?
Desexed dogs – 2.6 times less likely to bite!
Why would you NOT desex your dog??
Golden Retrievers: Cancer if you do, cancer if you don’t

07/1/14

Desexed dogs – 2.6 times less likely to bite!

Australian Veterinary Association makes this claim, in its PDF “Dangerous Dogs – a sensible solution“:

Entire (undesexed) dogs are 2.6 times more likely to bite than those that are spayed or neutered (desexed)

Are undesexed dogs really that risky?

I decided to read the three studies referenced individually.

 

avadesexing

 

 

Messam, LL, Kass, PH, Chomel, BB, Hart, LA 2008, ‘The human-canine environment: a risk factor for non-play bites?’, Veterinary Journal, 177(2); 205-15.

This study used data from 2003 (11 years ago) collected in Kingston, Jamaica and San Fransico, USA. Participants were recruited from vet clinic waiting rooms where they were presented with a questionnaire, set to determine the nature of their dog’s biting behaviour (and differentiating it from play biting).

When it came to comparing entire and gonadectomised dogs, this research suggests:

  • Intact dogs are more likely to bite than desexed dogs
  • Intact males are 1.68 times more likely to bite than desexed males
  • Intact males were 0.8 times more likely to bite than intact females
  • Spayed females were the ‘least bitey’

 

Guy, NC, Luescher, UA, Dohoo, Se, Spangler, E, Miller, JB, Dohoo, IR and Bate, LA 2001, ‘Demographic and aggressive characteristics of dogs in general veterinary caseload’, Applied Animal Behaviour Science, vol 74, iss 1. 

This research is based on data collected in Cannada in 1996 (18 years ago), targeting owners with a questionnaire waiting for vet appointments in three Canadian provinces. Their results indicate:

  • The lowest level of aggression (biting and growling) was reported in intact female dogs
  • Intact male dogs were twice as likely to have bitten as intact female dogs
  • Intact male dogs and neutered females incidents of biting was reported at a similar level

And to quote:

“Relative to intact female dogs, neutered male dogs of at least 1 year of age were at the highest risk for having previously shown biting behaviour, followed by neutered female dogs, and intact males… [O]ur results indicate that the behavioural outcomes of [neutering] are worthy of further investigation.”

 

Gershman, KA, Sacks, JJ & Wright, JC 1994, ‘Which dogs bite? A case-control study of risk factors’, Pediatrics, 93 (6 pt 1), 913-7. 

This study used data from 1991 (23 years ago) using 178 dog bites requiring medical treatment of a non-household-member in Denver, USA. Data was only used for dogs that had not bitten before. The study itself recognises this is a small sample size.

Their data concludes:

  • not-neutered dogs were 2.6 times more likely to bite
  • chained dogs were 2.8 times more likely to bite
  • dogs living with a baby were 3.5 times more likely to bite
  • male dogs were 6.2 times more likely to bite

 

So, are entire dogs 2.6 times more likely to bite?

If you are looking at the study in Denver, USA, in 1991 (23 years ago!) then, yes, their conclusions indicate that intact dogs are 2.6 times more likely to bite than desexed dogs.

But the other evidence referenced by the AVA does not make the exact same conclusions. The study conducted in 2003, using data from Jamaica and the USA, found that intact males were 1.68 times more likely to bite than castrated males, and 0.8 times as likely to bite as intact females. (This study is also old, with the data being collected 11 years ago.)

And that other article, with data from Canada in 1996 (18 years ago) makes pretty much the opposite conclusion. They found that neutered male dogs were the riskiest in terms of bites.

 

Questions to ask…

Why are we relying on data over a decade (or two decades) old? If aggression in entire dogs was a common phenomenon, surely we would have countless studies showing this problem.

Where is the Australian data-set?

Where is the study that controls for factors such as selectionsocialisation, and socio-economic factors?

 

What the AVA should really be saying is:

According to one study conducted in Denver, USA, 23 years ago, entire dogs were found to be 2.6 times more likely to deliver a bite (that required medical treatment) to a stranger than desexed dogs.