This section is for providing general information on various Health topics that are related to dogs.
The various subjects are not related to specific breed problems but we are including them to help you make your own informed decisions. We do not recommend products or specific treatments, those have to be discussed with your vet.
You can report an unexpected reaction to an animal medicine or microchip to the Veterinary Medicines Directorate (clik here to VMD). You can also report if an animal medicine hasn’t worked. This will help all dogs and owners.
Clicking on the brown links will bring you directly to the corresponding information
This section will be updated regularly based on the latest news on Health regulations, research,…
Current issues in small animal vaccinology
If vaccination has been so successful, then why is it necessary to continually re-evaluate vaccination practice? There is little doubt that, in most developed countries, some of the major infectious diseases of dogs and cats are considered at most uncommon in the pet population. However, even in those countries there remain geographical pockets of infection and sporadic outbreaks of disease may occur, and the situation regarding free-roaming or shelter populations is distinctly different from that in owned pet animals. In many developing countries these key infectious diseases remain as common as they once were in developed nations and a major cause of mortality in small animals. Although it is difficult to obtain accurate figures, even in developed countries it is estimated that only 30–50% of the pet animal population is vaccinated, and this is significantly less in developing nations. The global economic recession post-2008 has had further impact on the uptake of preventive healthcare by pet owners in developed countries and survey data suggests a recent decline in vaccination (Anon 2013a).
In small animal medicine, we have been slow to grasp the concept of ‘herd immunity’ – that vaccination of individual pet animals is important, not only to protect the individual, but to reduce the number of susceptible animals in the regional population, and thus the prevalence of disease. Herd immunity related to use of core vaccines that provide a long (many years) DOI is highly dependent on the percentage of animals in the population vaccinated and not the number of vaccinations that occur annually. Therefore, every effort should be made to vaccinate a higher percentage of cats and dogs with the core vaccines. It is simply not possible to induce ‘better’ immunity in an individual animal by giving repeated vaccinations, i.e. a dog receiving a core MLV vaccine every 3 years will be equally well protected compared with one receiving the same vaccine annually (Bohm et al. 2004, Mouzin et al. 2004, Mitchell et al. 2012) [EB1], but this may not necessarily be the case for feline core vaccines (see below).
In recent years the re-emerging concept of ‘One Health’ has also impacted on the field of vaccinology. The management of infectious diseases through the collaborative interaction of human medical, animal and environmental healthcare professionals provides a rational and cost-effective goal at a time when the majority of newly emergent human infectious diseases is proposed to derive from wild or domestic animal sources (Gibbs 2014). The WSAVA has embraced the One Health concept with establishment of a One Health Committee in 2010 (Day 2010), the work of which overlaps with that of the VGG when tackling the major small companion animal zoonoses of canine rabies and leishmaniosis.
A second major concept regarding vaccination of dogs and cats has been the recognition that we should aim to reduce the ‘vaccine load’ on individual animals in order to minimize the potential for adverse reactions to vaccine products and reduce the time and financial burden on clients and veterinarians of unjustified veterinary medical procedures. For these reasons we have seen the development of vaccination guidelines based on a rational analysis of the vaccine requirements for each pet, and the proposal that vaccines be considered ‘core’ and ‘non-core’ in nature. To an extent this categorization of products has been based on available scientific evidence and personal experience – but concerted effort to introduce effective companion animal disease surveillance on a global scale would provide a more definitive basis on which to recommend vaccine usage (Day et al. 2012). In parallel with the categorization of vaccines has been the push towards marketing products with extended DOI, to reduce the unnecessary administration of vaccines and thereby further improve vaccine safety. Both of these changes have necessitated a frame-shift in the mind-set of veterinary practitioners, which is now becoming the accepted norm in many countries.
Comprehensive Individual Care beyond Vaccination
In the past, veterinary practice has benefited from the annual administration of vaccines. By encouraging owners to bring their pets yearly for vaccination, veterinarians were able to recognize and treat disease earlier than might otherwise have been the case. In addition, the annual visit provided an opportunity to inform clients of important aspects of canine and feline health care.
Unfortunately, many clients have come to believe that vaccination is the most important reason for annual veterinary visits. Veterinarians have been concerned that a reduction in vaccination frequency will cause clients to forgo the annual visits and that the quality of care will diminish. It is therefore essential that veterinarians stress the importance of all aspects of a comprehensive individualized health care program. Emphasis should be placed on detailed history taking; thorough physical examination performed in the presence of the client, and individualized patient care. The importance of dental care, proper nutrition, appropriate diagnostic testing and the control of parasites and of zoonotic diseases should be addressed during evaluation of each pet. Behavioural concerns should be discussed, as well as the necessity for more frequent, tailored examination of young and geriatric animals and animals of particular breeds with well characterized disease predispositions. Discussion of vaccination is simply one part of the annual health check visit.
During regular (usually annual) health checks, clinicians should assess the need for core and non-core vaccines for that particular year. The practitioner should explain to the client the types of vaccines available, their potential benefits and risks, and their applicability to the particular animal, given its lifestyle and risk of exposure. While an animal might not receive core vaccination every year, most non-core vaccines require annual administration – so owners will continue to see their animal vaccinated annually. The regional incidence and risk factors for various infectious diseases should also be discussed. Ways to reduce the impact of acquired disease (e.g. avoiding overcrowding, improving nutrition, and restricting access to infected animals) should also be reviewed.
Vaccinations should be considered as only one component of a comprehensive preventive health care plan individualized based on the age, breed, health status, environment (potential exposure to harmful agents), lifestyle (contact with other animals) and travel habits of the pet.
Age has a significant effect on the preventive health care needs of any given individual. Puppy/kitten programs have traditionally focused on vaccinations, parasite control and neutering. Today, opportunity exists to incorporate behaviour counselling and zoonotic disease management. For the ageing pet, senior care programs are becoming increasingly popular. Nutritional, dental disease and parasite control assessment and counselling should take place on an individualized basis throughout the life of the pet. There is no evidence that older dogs and cats, which have been fully vaccinated as pups or kittens, require a specialized programme of core vaccination (Day 2010, Horzinek 2010, Schultz et al. 2010). Experimental evidence shows that older dogs and cats have persisting immunological memory to core vaccines, as detected by measurement of serum antibody, and that this may be readily boosted by administration of a single vaccine dose (Day 2010) [EB1]. In adult animals, decisions about revaccination with most core products (CDV, CAV and CPV and FPV) may be made via serological testing. Practitioners who offer this alternative to vaccination report that it is greatly appreciated by owners who may have concerns about vaccination frequency and offering this alternative acts as a ‘practice builder’. By contrast, aged animals may not be as efficient at mounting primary immune responses to novel antigens that they have not previously encountered (Day 2010) [EB1]. Studies of UK dogs and cats vaccinated for the first time against rabies for pet travel have clearly shown that more aged animals fail to achieve the legally required antibody titre (Kennedy et al. 2007) [EB1].
The environment in which a pet resides can profoundly affect its health status and should be assessed during annual health care visits in order to define risk factors and develop appropriate preventive measures.
By estimating the extent to which dogs and cats come into contact with other animals in unobserved circumstances, veterinarians can assess the need for non-core vaccinations. Dogs that visit kennels, grooming salons, common areas and wooded, tick-infested areas are potentially at greater risk from certain infectious diseases than dogs that do not frequent these areas.
Just as the human population has become more mobile, so has the pet population, resulting in potential exposure to infectious agents, parasites and environmental hazards not found where the animal normally lives. Determining past and anticipated future travel during each visit allows for greater individualization of preventive care and diagnostic testing plans.
Medical Record Documentation
At the time of vaccine administration, the following information should be recorded in the patient’s permanent medical record:
date of vaccine administration
identity (name, initials or code) of the person administering the vaccine
vaccine name, lot or serial number, expiry date and manufacturer
site and route of vaccine administration.
The use of peel-off vaccine labels and stamps that imprint the medical record with the outline of a pet facilitates this type of record keeping which is mandatory in some countries. Adverse events should be recorded in a manner that will alert all staff members during future visits. Informed consent should be documented in the medical record in order to demonstrate that relevant information was provided to the client and that the client authorized the procedure (e.g. ‘off-label’ use of products as discussed above). At the very least, this notation should indicate that a discussion of risks and benefits took place prior to vaccination.
VGG recommends that vaccination certificates be designed to include not just the dates on which vaccines were administered, but also a field for the veterinarian to state the date on which vaccination is next recommended. This will help diminish confusion in the minds of pet owners and kennel/cattery proprietors.
The major threat for pets coming from ticks is transmission of tick-borne diseases. Almost all tick species transmit one or more tick-borne diseases, e.g. anaplasmosis, babesiosis, borreliosis (=Lyme disease), ehrlichiosis, hepatozoonosis, meningoencephalitis, etc. But not all species transmit all the diseases. Which tick species transmit which disease is regionally different. Most veterinary doctors know which tick-borne diseases a particular tick species transmits in a specific region. These diseases affect mainly dogs, but cats in rural areas can also be affected.
Humans may be affected by some of these tick-borne diseases as well, but only if they are also bitten by ticks, not because the disease that affects the pet is contagious for humans (as e.g. influenza). As previously mentioned, it is also extremely unlikely that a tick that has bitten a pet will afterwards bite its owner and transmit the same disease.
The clinical symptoms of tick-borne disease are frequently unspecific and early diagnosis is not always easy. Unfortunately it is not rare that diagnosis is done too late. In the following the most relevant symptoms of tick-borne diseases are summarized.
A single tick can transmit the disease! But it is important to know that this does not always happen. Successful transmission of the disease occurs several hours after the tick has started biting, depending on the tick species and the disease. The longer the bite, the higher the risk of disease transmission. This is why it is important to find the ticks and to remove them as early as possible. Therefore, after a dog has been outdoors in a risky environment it should be thoroughly inspected, if possible not later than 12 hours after the walk. It is not recommended to inspect the pet immediately after the walk because unfed ticks are rather small and difficult to notice. About 12 hours later they have started to engorge and are easier to find.
The risk of becoming infected with a tick-borne disease depends strongly on the region and the season. The number of active ticks in a region varies along the season (winter versus summer, or humid versus dry). And not all ticks are infected with microbial pathogens. The infection rate of ticks varies considerably from one region to another one. By an infection rate of 10% only 1 in 10 ticks are infected with pathogens. But the pathogens can be more or less virulent in certain tick populations than in other ones. If the pathogen is only mildly virulent, many bitten and infected hosts will not develop the disease because it is neutralized by the host’s immune system. All this can result in a risk of <1% of developing the disease if bitten. But if the pathogen is highly virulent, many infected pets will develop the disease. This can result in chances of developing a disease of >10%. Unfortunately, it is impossible for a pet owner to estimate these risks. Therefore it is highly recommended to check and follow whatever local warnings and recommendations regarding tick-borne diseases.
spot-ons, tablets, collars, shampoos, soaps, powders, sprays
Nowadays, there are basically four types of veterinary products containing tickicides for pets:
- For external use:
- Spot-ons = squeeze-ons = drop-ons = pipettes: mostly for monthly administration
- Collars impregnated with tickicides
- The rest: shampoos, soaps, sprays, lotions, ointments, dusts, etc.: the low-cost alternatives
- For internal use:
- Tablets: for oral administration every 1 or 3 months
The vast majority of the active ingredients used in this products act by contact, i.e. they have no systemic mode of action (though the blood of the host). The most notable exceptions with a systemic mode of action are afoxolaner (NEXGARD, NEXGARD SPECTRA), fluralaner (BRAVECTO), sarolaner (SIMPARICA) and selamectin (STRONGHOLD = REVOLUTION).
So far there are no tickicides for pets in the form of injectables or drenches.
When using low-cost topical products (e.g. shampoos, soaps, sprays, lotions, dusts, ointments, etc) it is important to treat the whole body surface of the pet and not only those parts where you have seen ticks. The reason is that you may notice adult ticks, but not larvae or nymphs that are too small to be seen by the naked eye.
Many veterinary products have a broad spectrum of activity, i.e. they control not only ticks but also other pet parasites, e.g. fleas, mites, gastrointestinal roundworms, heartworms, tapeworms, etc. Since your pet may need treatment or protection against some of these other parasites as well, it can make sense to select a product based on its spectrum of activity.
Be aware that not all veterinary products with a claim for tick control are effective against all tick species. In fact, most pet tickicides, even the most expensive ones have been checked against the major tick species in Europe and the USA, the largest markets. These species are typically Ixodes (ricinus and scapularis), Dermacentor (reticulatus and variabilis), Amblyomma americanum and Rhipicephalus sanguineus. But they have not been tested against dozens of other tick species that are less frequent in Europe or North America but prevail in other regions of the world. They may work, or they may not work.
Fleas and ticks are the most common external parasites of dogs and cats, and consequently most ectoparasiticidal drugs target these parasites. Many of these drugs are also effective against lice, mites, mosquitoes and other less important parasites.
Based on their efficacy and reliability, there are two large groups of commercial products to control these parasites, “hard” products and “soft” products.
“Soft” products are mostly shampoos, soaps, sprays, powders and the like that kill or repel more or less quickly and effectively (70-80%) these parasites immediately after application, but offer no real protection against re-infestation (i.e. no residual effect). This may require frequent re-treatments during the parasite’s season. These “soft” products contain often the same pesticides than the “hard” products, but in less sophisticated formulations. They also contain more or less natural insecticides, often with a partial but sufficient efficacy. Registration of these products is often rather easy and most of them have not been thoroughly investigated regarding efficacy and safety. They are sold mostly over the counter. And there are thousands of brands and hundreds of manufacturers of these “soft” products.
“Hard” products are mainly:
- Spot-ons (pipettes, squeeze-ons) for topical administration
- Tablets (pills, chewables, capsules, etc) or suspensions for oral administration
- Insecticide-impregnated collars
- Injectables (very few)
All these “hard” products have in common that they are highly effective (usually >90%) against the parasites and offer at least about 1 month protection against re-infestation. In contrast with the soft products most of these products have been thoroughly investigated regarding efficacy and safety because registration requirements are rather strict in most countries. For this reason, most of the original products are marketed by large to medium pharmaceutical or agrochemical companies (e.g. BAYER, ELANCO, MERIAL, ZOETIS, etc.). Some of these products need a prescription and are sold only in pharmacies or veterinary clinics. Another common feature of these “hard” products is that they are often substantially more expensive than the “soft” ones.
Active ingredients used in flea + tick products
Very few active ingredients are effective against all external parasites and all their developmental stages. For these reason, numerous brands contain mixtures of active ingredients.
A typical mixture is adulticide + IGR (=Insect Growth Regulator). Most insecticides are adulticides, i.e. effective mainly or exclusively against the adult parasites, whereas IGRs are effective against immature stages, and not against the adults. Most common IGRs used in these products are methoprene and pyriproxyfen that are added to ensure that fleas that may survive the adulticide do not reproduce. These IGRs have no effect whatsoever on ticks or mites.
Another typical mixture is insecticide + tickicide. Several excellent flea killers (e.g. imidacloprid, indoxacarb, spinosad, etc.) are not effective against ticks. To add tick efficacy they are often mixed with a synthetic pyrethroid (e.g. permethrin, cyphenothrin, etofenprox, etc.) or with amitraz. But all these active ingredients are rather toxic to cats, and as a consequence most of these mixtures are only for dogs. Synthetic pyrethroids are often also effective against mosquitoes.
Flea and tick control in dogs and cats is the largest single Animal Health market worldwide, and a very profitable one. Consequently, all large and small companies have fought and are still fighting fiercely to get their share of it. This has resulted in numerous new active ingredients of different chemical classes fruit of massive investments in R&D by the large laboratories. And it has also resulted in numberless generic brands, once patent protection expired for the most successful active ingredients, particularly for fipronil.
This link includes the most popular “hard” products marketed in most English-speaking countries.
- Topical spot-ons
- with fipronil alone
- with fipronil + IGR
- with fipronil + tickicide
- with fipronil + IGR + tickicide
- with imidacloprid
- with other active ingredients
- Oral tablets or suspensions
- Collars impregnated with insecticides
Home-made traditional remedies against ticks on dog and cat
There are numerous home-made remedies against ticks, most of them based on traditional recipes using locally available herbs or other natural products. They are the result of centuries of efforts for finding relief against ticks when modern insecticides were not available.
The bottom line is that no such remedies are as effective as modern synthetic pesticides. They may bring partial relief for a few hours, maybe a few days, but certainly not week or month-long protection. Such products are usually substantially less effective against ticks than synthetic tickicides. Besides being less effective, many of them have a very short residual effect, i.e. they protect no more than a few hours to a few days against re-infestation. The reason is that they are easily washed away by water (rain, washing, swimming, etc.) or broken down by sunlight, or they simply evaporate very quickly.
There are numerous Internet sites with a lot of home-made remedies and recommendations, but almost none of them are supported by reliable investigations. Nevertheless, it may be worth trying them: usually they are not expensive and the risk of serious side effects is usually not too high. Many such remedies are based on do-it-yourself recipes based on plant extracts or products (citronella oil, neem, rosemary, lavender, lemon balm, etc.). Try them. If they work, fine. If they don’t, you will never know whether the recipe is useless or whether you did something wrong. But it doesn’t matter: just try another one.
It is good to know that in most countries products containing such “natural parasiticides” (e.g. plant extracts) are submitted to much less stringent regulations than veterinary parasiticides. This means that they don’t need to proof their efficacy against parasites, or their safety for the pets, users and the environment through such strict and thorough investigations as the products containing synthetic parasiticides. Many regulatory authorities seem to simply assume that being natural they are “safe enough”, or at least not harmful, and that users will find out themselves whether they are effective or not… Obviously, the cost and the know-how to develop and market such “natural products” are substantially lower than for veterinary medicines containing synthetic parasiticides. This low cost explains their proliferation. It is not possible to deal with such products here in detail.
BUT: when dealing with plant remedies, especially self-made ones, it is good to know that the active components in herbs are also chemicals, i.e. specific molecules that have a biological effect, in this case a tick killing or repelling effect. They have been naturally synthesized in the plants. But this says nothing about the safety of such chemicals. It is wrong and dangerous to believe that something is safe because it is natural! The most potent poisons known are often natural, i.e. of plant or animal origin. And by the way, many such “natural chemicals” are also manufactured industrially and used in numberless so-called “natural” or “biological” products”.
Canine Hip Dysplasia in Dogs
Hip dysplasia in Dogs is a disease of the hip in which the ball and socket joint is malformed. This malformation means that the ball portion and its socket don’t properly meet one another, resulting in a joint that rubs and grinds instead of sliding smoothly.
The hip joint is composed of the ball and the socket. The development of hip dysplasia is determined by an interaction of genetic and environmental factors, though there is a complicated pattern of inheritance for this disorder, with multiple genes involved. Hip dysplasia is the failure of the hip joints to develop normally (known as malformation), gradually deteriorating and leading to loss of function of the hip joints.
Hip dysplasia is one of the most common skeletal diseases seen in dogs. Gender does not seem to be a factor, but some breeds are more likely to have the genetic predisposition for hip dysplasia than other breeds. Large and giant breeds are most commonly affected, including the Great Dane, Saint Bernard, Labrador Retriever, and German Shepherd. Rarely, small breed dogs can also be affected, but are less likely to show clinical signs.
Hip dysplasia often begins while a dog is still young and physically immature. Early onset usually develops after four months of age. There are also cases of later onset, where hip dysplasia develops later due to osteoarthritis, a form of joint inflammation (arthritis) that is characterized by chronic deterioration, or degeneration of the joint cartilage.
Symptoms and Types
Symptoms depend on the degree of joint looseness or laxity, the degree of joint inflammation, and the duration of the disease.
- Early disease: signs are related to joint looseness or laxity
- Later disease: signs are related to joint degeneration and osteoarthritis
- Decreased activity
- Difficulty rising
- Reluctance to run, jump, or climb stairs
- Intermittent or persistent hind-limb lameness, often worse after exercise
- “Bunny-hopping,” or swaying gait
- Narrow stance in the hind limbs (back legs unnaturally close together)
- Pain in hip joints
- Joint looseness or laxity – characteristic of early disease; may not be seen in long-term hip dysplasia due to arthritic changes in the hip joint
- Grating detected with joint movement
- Decreased range of motion in the hip joints
- Loss of muscle mass in thigh muscles
- Enlargement of shoulder muscles due to more weight being exerted on front legs as dog tries to avoid weight on its hips, leading to extra work for the shoulder muscles and subsequent enlargement of these muscles
Influences on the development and progression of hip dysplasia are concurrent with both genetic and environmental factors:
- Genetic susceptibility for hip looseness or laxity
- Rapid weight gain and obesity
- Nutritional factors
- Pelvic-muscle mass
Your veterinarian will perform a complete physical exam on your dog, including a blood chemical profile, a complete blood count, an electrolyte panel and a urinalysis. Inflammation due to joint disease may be noted in the complete blood count. As part of surveying the physical symptoms and fluid work-ups, your veterinarian will also need a thorough history of your dog’s health, onset of symptoms, and any possible incidents or injuries that may have contributed to your dog’s symptoms. Any information you have on your dog’s parentage will be helpful as well, as there may be a genetic link.
X-rays are crucial for visualizing the signs of hip dysplasia. Some of the possible findings may be degenerative disease of the spinal cord, lumbar vertebral instability, bilateral stifle disease and other bone diseases.
Canine Hip Dysplasia Treatment | Management of Hip Dysplasia in Dogs
So your dog’s just been diagnosed with hip dysplasia, or you just welcomed a cute cuddly puppy into your home who is part of a breed genetically predisposed to get hip dysplasia. Either way, we’ve put together a really helpful list of treatment and management options so you know just what to expect down the road!
Before you read on, we’ll recap our in-depth medical look at hip dysplasia. The condition occurs when a dog’s hip joints don’t develop right, causing the hips to partially dislocated and leads to early development of degenerative joint disease. This can cause a dog a lot of pain and can make it really hard to walk around. The cause is almost always genetic, and being overweight can make it a lot worse. And while it tends to affect large breed dogs more frequently, all breeds of dogs are at risk.
Because the condition is inherited, there’s no cure for hip dysplasia. But the good news is, there are tons of effective ways to treat and manage it! Here are some common treatments and habits that can help your pooch stay happy and healthy:
- Exercise. Regular, low-impact activity such as swimming or leash-walking will help reduce some of the pain in your dog’s joints. It will also lead to increased tendon and muscle strength. TIP: When walking, try to keep your pup away from hard surfaces like concrete or asphalt. It’s hard on the joints and might do more harm than good.
- Physical therapy can really help reduce your dog’s pain and increase his mobility. From massages to hydrotherapy – the use of underwater treadmills – physical therapy can be a great option when done right. Before starting, be sure to talk with your veterinarian who knows your dog’s limitations.
- Joint prescription diets or formulas, recommended by your veterinarian, can help decrease inflammation and promote cartilage healing.
- Give your pooch pain medications, like NSAIDs (non-steroidal anti-inflammatory drugs), to reduce pain, but only as directed by your veterinarian.
- Create a dog-friendly environment using ramps or easy steps to help your dog into a car, bed, or around the house. Limit your dog’s movement up and down steps. Soft mattresses work well too, and a heated dog bed in cold weather can be great. TIP: Be careful with regular heating pads, as they can get very, very hot and burn your pooch.
- Acupuncture as an ancillary therapy may provide additional benefit in some patients.
- Surgery can help in many cases. Various surgical procedures have been described including juvenile pubic symphysiodesis and total hip replacement (see below). Your veterinarian will advise you of the various surgical procedures, if an option for your pet, and will refer you to a veterinarian who is a board certified specialist in surgery if appropriate.
- Juvenile pubic symphysiodesis. It’s a mouthful, but it describes a short, simple surgical procedure for very young puppies in breeds with a high likelihood of developing hip dysplasia. It is a preventive procedure, often combined with a neuter or spay.
- Total hip replacement. This is an option in dogs with especially severe hip dysplasia and can really increase quality of life if successful.
This list isn’t comprehensive – there are a variety of other procedures and recommendations, and your veterinarian will be the best resource in determining what is right for a dog diagnosed with hip dysplasia. With the right treatment and management, hip dysplasia can often be managed successfully and allow for a healthy, happy life for the dog.
If you have any questions or concerns, you should always visit or call your veterinarian – they are your best resource to ensure the health and well-being of your pets.
Copyright 2013 by András Péter
This site was created to provide a web based image processing tool that can be used to demonstrate the differences in visual perception between humans and dogs. The Dog Vision tool can only show the differences that can be visualized on a static image:
- Differences in color perception
- Differences in brightness discrimination
- Differences in visual acuity
The user can upload an image and then apply the modifications corresponding to any of the three perceptual differences above. The effect of each perceptual difference can be applied separately or in any combination. There are numerous other differences between the visual perception of humans and dogs. For an excellent review see the article from Miller & Murphy 1995 or for a shorter summary Miller & Lights 2001.
Below you’ll find some information about the visual perception of dogs and technical details about how the image processing tool works. If you would like to use the tool right away click here!
More like: Roses are yellow, Violets are blue!
Dogs are not completely color blind since they have a dichromatic color perception. Unlike humans who have three different color sensitive cone cells in their retina (red, green and blue) dogs have only two (yellow and blue)[3,4].
This does not mean that dogs can’t see green or red objects! It only means that they can’t distinguish green, yellow or red objects based on their color. However they can still distinguish a red ball from a green one if there is a difference in the perceived brightness of the two.
The color vision of dogs is similar to a person suffering from deuteranopia (red-green color blindness). Red, yellow and green are perceived as one hue. Blue and purple are perceived as a second hue. Cyan and magenta are perceived as a neutral hue (grey).
The image below shows a full RGB spectrum and how the same colorline would be perceived by a dog.
Brightness discrimination is the ability to differentiate between different shades. It is measured by determining the smallest discernible difference in brightness (ΔR) between two stimuli compared to the absolute brightness (R) of the brighter stimulus (ΔR/R = Weber fraction). The Weber fraction calculated for humans is 0.11 whereas the Weber fraction for dogs is 0.22]. Thus the brightness discrimination of dogs is about 2 times worse than that of humans.
This means for example that certain shades of gray that humans perceive as different are perceived as the same shade by dogs. The image below illustrates this effect by showing a set of rectangles with differing brightness, and the same set with halved relative brightness.
Visual acuity is a measure of the spatial resolution of the visual system. It is often measured in cycles per degree (CPD), which measures how much an eye can differentiate one object from another in terms of visual angles. The maximum visual acuity of the human eye is around 50 CPD and 60 CPD. The measurements of dogs’ visual acuity vary around 7.5-9 CPD and 11.6 CPD. According to these measurements dogs’ visual acuity is 4 to 8 times worse than that of humans.
Choosing the amount by which the visual acuity should be decreased depends on many factors: the angle of view of the image, the resolution of the image, dpi ratio of the screen on which the image is viewed and the distance from which the screen is viewed. Under average conditions if the picture’s resolution is equal to the resolution of the screen that it is viewed on then by reducing the visual acuity by a factor of 5 is a good approximation.
The image below shows a black and white grating with a bar width of 1 to 7 pixels. The effect of visual acuity reduced by a factor of 2 to 8 can be observed on the horizontal bands stacked above each other.
Visual acuity reduced by a factor of 2
Visual acuity reduced by a factor of 3
Visual acuity reduced by a factor of 4
Visual acuity reduced by a factor of 5
Visual acuity reduced by a factor of 6
Visual acuity reduced by a factor of 7
Visual acuity reduced by a factor of 8
- Miller PE, Murphy CJ (1995) Vision in dogs. J. Am. Vet. Med. Assoc. 207:1623-34.
- Miller PE, Lights F (2001) Vision in animals – What do dogs and cats see? In: The 25th Annual Waltham/OSU Symposium. Small Animal Ophthalmology. pp 27–28.h
- Neitz J, Geist T, Jacobs GH (1989) Color vision in the dog. Vis. Neurosci. 3:119-125.
- Jacobs GH, Deegan JF, Crognale MA, Fenwick JA (1993) Photopigments of dogs and foxes and their implications for canid vision. Vis. Neurosci. 10:173-80.
- Griebel U, Schmid a (1997) Brightness discrimination ability in the West Indian manatee (Trichechus manatus). J. Exp. Biol. 200:1587-92.
- Pretterer G, Bubna-Littiz H, Windischbauer G, Gabler C, Griebel U (2004) Brightness discrimination in the dog. J. Vis. 4:241-249.
- Russ J (2006) The Image Processing Handbook. CRC Press.
- Campbell FW, Green DG (1965) Optical and retinal factors affecting visual resolution. J. Physiol. (Lond.) 181:576-93.
- Murphy CJ, Mutti DO, Zadnik K, Hoeve J Ver (1997) Effect of optical defocus on visual acuity in dogs. Am. J. Vet. Res. 58:414-418.
- Odom JV, Bromberg NM, Dawson WW (1983) Canine visual acuity: retinal and cortical field potentials evoked by pattern stimulation. Am. J. Physiol. 245:R637-41.
Image with smiling dog taken from: http://axon-axoff.tumblr.com/post/7340439912
This short and entertaining video will help you understand one of your dog most useful sense