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Ask a vet online – How often should my dogs get boosters?

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Karen Taylor asked: How often should our dogs be re-vaccinated (boosters)? Answer: Hi Karen, thanks for your question about booster vaccinations. This is an area that’s become quite controversial in the last few years, and there’s a lot of confusion about the subject. In addition, there’s a lot of very poor-quality information out there, so I’ll try to make this quite clear and obvious! To put it as simply as possible – see your vet every year for a health check, and discuss your vaccination strategy with them. For more detail... now read on! What are vaccinations? Put simply, a vaccination is a way of teaching your dog’s immune system how to recognise and defeat the micro-organism that causes an infectious disease, without the risks (of illness, potential long term health problems or death) inherent in a “natural” infection. This is achieved in one of three ways: 1)      A weakened form of the disease-causing organism. These are called “modified live” or “attenuated” vaccines, e.g. for Distemper and Parvovirus; the organism included is unable to multiply and/or cause clinical disease, but it is active enough to stimulate a strong immune response. Most modified live vaccines give a stronger and more long-lasting immune response than an inactivated vaccine; however, they aren’t suitable for every disease (because some organisms cannot be weakened enough to make them safe). 2)      An inactivated (“killed” or “dead”) form of the organism. These cannot ever cause disease, but allow the immune system to recognise the protein coat of the organism and therefore attack it next time. They may be used for particularly dangerous or unpredictable diseases such as Rabies or Leptospirosis, but don’t always give such long-lasting protection. 3)      Subunit vaccines, introducing part of the organism to teach the immune system what it “looks like”. For these, part of the protein coat of the target organism is replicated in a lab, and included in the vaccine; this means the immune response is really tightly targeted at one particular, vital, part of the organism. These are used, for example, in the Leishmania vaccine. There are 2 groups of vaccines – core and non-core. Core vaccines are those that should be given to every dog – they protect your dog and everyone else’s against dangerous, highly contagious and potentially fatal diseases. Non-core vaccines are those that are given to protect dogs that are particularly at risk of a specific condition because of their location, lifestyle, etc. The core vaccines that every dog should have are against:
  • Distemper.
  • Parvovirus.
  • Canine Infectious Hepatitis.
The vaccine against Leptospirosis is technically non-core; however, it is generally agreed that every dog in the UK is at risk of Lepto (which is spread by rat urine), and so it is treated as a core vaccine by most vets. The non-core (optional) vaccines available are:
  • Rabies (only necessary for pets travelling abroad).
  • Parainfluenza (one of the causes of kennel cough).
  • Kennel Cough (the bacterial sort, Bordetella bronchiseptica).
  • Lyme Disease (only necessary for dogs at high risk, e.g. gundogs, in high risk areas, e.g. the South West peninsula).
  • Leishmania (only necessary for dogs travelling to southern Europe).
  • Canine Coronavirus (only usually needed in breeding kennels).
If vaccines are so good, why do they need boosting? Because nothing lasts forever! Eventually, the immune system starts to “forget” how to handle a particular disease organism. Booster vaccines effectively remind the system and refresh the immunity. However, immunity to different diseases (and different types of vaccine, for that matter) lasts a variable amount of time, and that’s the problem. Some dogs will retain immunity for longer than others – unfortunately, there’s no easy way to tell which dogs are immune to what for how long. Is there any way to tell whether my dog actually needs a booster? Not really! The trouble is that although some vaccines operate by producing protective antibodies (e.g. Rabies), others rely on inducing a Cell Mediated Immune Response (immunity that doesn’t rely on antibodies in the blood, but circulating immune cells, e.g. T-lymphocytes and Natural Killer (NK) cells) – such as the Leishmania vaccine, which may not produce any antibodies at all. And most of them probably rely to some extent on both systems. It's easy to test the dog’s blood for antibodies (and there are some commercial companies that will do this and say “yes, high levels of antibody, so the dog is protected” or “no, not enough antibody, the dog needs to be vaccinated again”. However, this is not generally considered reliable, because:
  • The serological titre (level of antibodies in the blood) can only tell you how much antibody there is in the bloodstream at the specific time the test is done - it cannot tell you whether the levels will remain high for the following 12 months.
  • The link between antibody levels and protection isn't consistent - some dogs utilise other parts of the immune system (cell mediated immunity) – for example, dogs can be protected against Leptospirosis in the presence or absence of significant circulating antibody levels.
So how long does immunity actually last? How long the vaccine lasts depends on the exact formulation of the vaccine; at the time of writing, the three Core vaccines generally need boosting 1 year after the initial course, then every 3 years. Most Rabies vaccines needs boosting only every 3 years; and the others usually require annual boosters. To get a license for a vaccine, the manufacturer has to demonstrate that the product has a protective effect, however that is defined. For Core vaccines, they have to demonstrate onset and duration of immunity such as to fulfil the license claim to:
  • “Prevent mortality and clinical signs caused by canine distemper virus infection”.
  • “Reduce clinical signs of infectious hepatitis and viral excretion due to canine adenovirus type 1 infection”.
  • “Prevent mortality, clinical signs and viral excretion following canine parvovirus infection”.
If this cannot be demonstrated to the regulator (in the UK, the Veterinary Medicines Directorate - VMD), they won’t get a license for the product. This means that manufacturer’s recommendations for duration of immunity are those that will protect the vast majority of dogs for the quoted time (3 years or 12 months, depending on the vaccine). To make life a little more complex, any vet who uses a different vaccination interval, unless they can document a good clinical justification, is technically acting illegally by using the vaccine off-license (i.e. not as licensed by the manufacturer). This sort of behaviour tends to lead to unpleasant interviews with the VMD and has led to vets being struck off (although not, to my knowledge, for vaccine infringements as yet). Can over-vaccination harm my dog? There’s no reliable evidence that it can. In cats, every subcutaneous injection (of anything, even saline!) slightly increases the risk of an Injection Site Sarcoma, but despite a lot of scientists, vets and owners trying to find a link, there’s no evidence that it causes any problems in dogs. That said, absence of evidence is not necessarily evidence of absence, so a responsible approach would be to vaccinate as infrequently as the current evidence suggests is sufficient to provide protection – in other words: 1)      Get a health check for your dog at the vets every year. 2)      Follow the manufacturer’s recommendations (unless your vet has a particular clinical reason not to):
  1. Distemper, Parvo and Infectious Hepatitis – boosters every 3 years.
  2. Lepto – annual booster.
  3. Rabies – boost every 3 years.
  4. Other Non-core vaccines – usually every year.
  I hope that helps; this is a really controversial area in some quarters, but the evidence base for the current vaccination protocols is pretty secure, and it is what I’d advise you to follow. David Harris BVSc MRCVS
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The story of Dan, a coughing Springer Spaniel

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Dan was a nine year old Springer Spaniel who loved strenuous physical exercise. His owner, Dr Mullen, was a medical doctor who was an enthusiastic hill walker, so they made a good team. They would spend days off in the Dublin mountains together on six-hour hikes through the countryside. Dan was brought to see me because he had developed an irritating cough, and Dr Mullen was worried.

The cough did not affect Dan during exercise. He was still able to run for hours without any problem, but the following morning, immediately after getting up, he would cough repeatedly as he walked around the room. It seemed to be a productive cough: sometimes he swallowed after the cough, and other times Dr Mullen found patches of white phlegm on the floor. When Dan had been up and about for half an hour, the cough seemed to clear, and he’d be fine for the rest of the day.

I started by physically examining Dan. I listened carefully to his chest with my stethoscope. He had the perfect heartbeat of a fit dog, with slow steady sounds and no murmurs or irregularities. His lungs, however, sounded noisier than normal, with some wheezes and crackles. He definitely had some type of lung disease, and further tests were needed.

The following day, Dan was anaesthetised, X-rays were taken, an endoscope was used to directly view the lining of his airways, and finally tiny biopsies were taken of the many red sore areas that we could see. Dr Mullen called in three days later to discuss the full results of our investigations.

“I can say for certain that Dan is suffering from Chronic Bronchitis”, I began. “The initial X-rays suggested that that there was thickening of his lower airways, and using the endoscope, we could see that the thickening was because of inflammation of the lining of the small tubes of the lungs, known as ‘bronchi’. The biopsy of the red, swollen areas confirms that the disease process is simple inflammation, with nothing sinister going on. Finally, he has a mild bacterial infection in his lungs.”

Dr Mullen asked me if an antibiotic would completely cure his dog.

“Although antibiotics will help him, for a complete cure, he needs to go onto long term medication using other drugs. The chronic bronchitis probably started out with a simple infection, but there is now also an irritant and allergic aspect to the disease. The tiny particles of dust, smoke and pollens that are always in the air are perpetuating the bronchitis. We’ll use two drugs to help him. Firstly, a ‘broncho-dilator’, which will widen his airways and lessen the tight narrowing of the bronchi that is making them irritated. Secondly, a low dose of steroids will directly lessen the irritation. We’ll modify his dose of each drug so that he should be able to live a normal, symptom free life without side effects from medication.” There are other options for treatment, including an inhaler mask, but this treatment was my standard first stage.

Dan was sent home with three containers of tablets, and twice-daily medication ritual became part of his routine. I saw him again two weeks later, and the cough had almost completely stopped. He was suffering some side effects from the steroids, with increased thirst and appetite, but we were then able to reduce the dosage, so that he was given tablets only on every second day. When he came back a full month later, Dr Mullen was delighted.

“His cough has vanished completely”, he told me. “And he is enjoying his walks more than ever. The only problem is that he’s wearing me out! Do you know any tonic pills for a fifty-five year old human?”

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Oscar, the grumpy cat who needed twice daily injections to treat his diabetes

[caption id="attachment_4489" align="aligncenter" width="585"]Oscar does not tolerate humans who annoy him Oscar does not tolerate humans who annoy him[/caption]

Oscar, a ten year old cat, had started to lose weight, despite the fact that he was eating well. His coat had begun to look bedraggled, as if he was not grooming himself as much as usual. His owner had noticed him visiting his water bowl more frequently, and she had needed to fill up the bowl every day, rather than every three days.

When I examined him it was clear that Oscar had lost a significant amount of weight. His ribs were prominent, and I could feel the sharp tips of the bones of his back. When I weighed him, I discovered that he had lost a kilogram since his previous visit.

Physically, I could find no obvious cause of a problem, so I decided that a blood profile was needed. Fifteen minutes later, the printout from the biochemistry analyser gave me the clear-cut diagnosis of his illness.

Oscar’s blood glucose was around four times higher than normal. The only possible reason for this was the condition known as diabetes mellitus. Oscar’s pancreas had stopped producing the hormone called insulin, and as a result, his blood glucose was not being controlled. Weight loss, ravenous appetite and copious thirst are classical signs of diabetes, in cats just as in humans and dogs.

As I explained the diagnosis to his owner, I could see a worried furrow developing across her brow. I explained that Oscar’s condition was treatable, but that he would need to have a daily injection of insulin for the rest of his life. Her shoulders slumped, and she looked at me sadly. “Nobody would dare to give Oscar an injection”, she told me. “He’d just get so annoyed with us if we tried something like that!”

I reassured her that the injection was given with an ultra-fine needle, and that only a tiny amount of liquid would be needed. For a cat of Oscar’s size, the volume of insulin would probably be around one hundredth of a teaspoonful, which is literally a single drop. It was very likely that he would barely notice the injection.

I demonstrated the injection technique, using a piece of fruit – an orange – as a practice target. It took a few attempts until she had learned to hold the syringe correctly, but soon she was able to insert the needle steadily and firmly into the orange. She was still very anxious about injecting her cat, so we decided that it would be best for her to bring him in to see me for his injection every morning for the first week.

The technique was simple. I gave Oscar a bowl of his favourite food, and as he lowered his head to eat, I quickly slipped the injection into the scruff of his neck. He stopped eating for a moment, and looked suspiciously at me before recommencing his meal. On day three, his owner gave the injection herself, and by day five, she was able to do this quickly and confidently.

After several dose adjustments over a few weeks, Oscar’s blood glucose had returned to normal. At the same time, his owner reported that his excessive thirst had disappeared. It seemed that his diabetes had been controlled.

The success of his treatment was confirmed at his final visit six weeks later. As the cage door was opened, Oscar stepped out in a confident and dignified fashion, with his head held high. He had put on weight, he was grooming himself again, and even his whiskers looked alert and bristling. He was definitely a healthy cat again.

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Kittens with passengers: ear mites

[caption id="attachment_4382" align="aligncenter" width="640"]Ear mites are very common in kittens Ear mites are very common in kittens[/caption] When a litter of rescued kittens were brought to see me recently, a careful examination of their ears was an important part of the check-up. I introduced the tip ofthe auroscope into each kitten’s ear, and by looking through the instrument I was able to see a magnified view of each ear canal. In normal animals, the pale blue-grey of the eardrum itself can often be seen. However, in these kittens, I could hardly see any normal ear canal. My view was blocked completely by thick, brown, sticky earwax. The cause of the excessive ear wax could be seen very clearly. Tiny white wriggling insect-like creatures could be seen swarming around the inside of each ear. The kittens were infected with ear mites. Ear mites are very common in kittens. They are very small mites, each measuring the size of a pin-head. They are very active, and they tend to move away from bright light. When examining an ear with an auroscope, ear mites can often be seen moving quickly out of the field of vision, as if running away from the vet. Ear mites are highly infectious, and they are especially common in feral colonies of cats. The adult mite feeds on the secretions produced by the lining of the ear. Eggs are laid inside the ear. These hatch out into tiny larvae which then mature into adults, and the life cycle continues. If one cat pushes its head against the body of another cat, ear mites can easily be transferred from one to the other. Kittens are obviously in very close contact with their mothers and with each other, so it is very common to find entire litters of kittens affected by dramatic infestations of ear mites. Most of us are familiar with the discomfort of an irritation in the ear, even from something as harmless as a small quantity of water lodging in our ears after swimming. The concept of live, wriggling insects crawling around inside the ear canal is very unpleasant! In many cases, kittens do show dramatic signs, such as repeated scratching of the ears. In other cases, an owner may have noticed the animal shaking their head more than usual,. However some cats, even with severe infestations, show no obvious external signs. Close examination of a kitten’s ears with an auroscope is essential to detect such ‘invisible’ cases. Ear mites can also affect dogs, but they are less common. Fortunately, there is no risk to humans. Those alarming, tiny, wriggly creatures are not going to crawl onto your hand, up your arm and into your own ear. However, if you have a household of dogs and cats, you do need to treat every animal individually to ensure that you have completely eradicated the infestation. Treatment of ear mites is not always easy. The mites are sensitive to most insecticides and a range of drops and ointments are available from your vet. The only complication is that the eggs of the ear mite are resistant to treatment, and these can remain unhatched for up to three weeks. This means that it may be necessary to continue to medicate affected kittens for an entire three week period, to ensure that all eggs have hatched with the resulting larvae being eradicated. Young kittens can be difficult to hold still, and they often learn how to escape from your grasp, so after the first few days of treatment it can become more difficult to continue. I saw the kittens again two weeks after their first visit. They were all in wonderful form, purring, playing with each other, and growing rapidly. Their ears were clean, both inside and out. They were ready for their new homes – with no passengers included!
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Could your cat have high blood pressure?

High blood pressure is a common problem for humans but did you know that cats can get it too? High blood pressure, also known as hypertension, is actually quite common in older cats, especially those with other diseases such as kidney disease or hyperthyroidism. The symptoms can be quite subtle or mimic those of other diseases so many cases remain undetected for quite some time. If left untreated, however, hypertension can lead to significant secondary health problems, so it’s definitely worth testing for. [caption id="attachment_4332" align="alignleft" width="288"]Bob having his blood pressure checked. Bob having his blood pressure checked.[/caption] What exactly is high blood pressure? High blood pressure occurs when the pressure within the blood vessels exceeds a certain threshold. Think of the hosepipe used to water your garden. If you turn the tap on too strongly, the water shoots out of the nozzle uncontrollably, damaging your flowers. The same is true for the body – organs like the brain and kidneys need blood to survive but if the blood pressure gets too high, it can start to damage the very organs it is trying to keep alive. To further complicate things, blood vessels have a tendency to leak under pressure and this extra fluid can cause further problems. How do cats develop high blood pressure? Many things can cause hypertension in cats from certain medications to neurological disease, but the two most common causes are kidney failure and hyperthyroidism. Both of these illnesses cause alterations in the very precise mechanisms that monitor and control blood pressure. It doesn’t always correlate with the severity of the disease (i.e., severe hypertension can be seen with only mild kidney disease) and in the case of hyperthyroidism, we sometimes see hypertension develop only after the thyroid problem has been treated. What are the symptoms of hypertension? The clinical signs associated with high blood pressure depend on which organs are most badly affected. One of the most common signs is acute blindness because the high pressure within the vessels of the eye causes the retina to detach from the nerves that tell the brain what the eye is seeing. So you may notice the cat bumping into things (although it’s amazing how many owners aren’t aware of their cat’s blindness because cats are so good at using their other senses to compensate), staying closer to home or having very dilated pupils or ‘wide eyes’. Another organ that is commonly affected is the brain so you might see serious signs such as circling and seizures or perhaps much more subtle behavioural changes such as crying out at night or being less sociable when people are around (how else would you tell if your cat had a headache?). You may see bleeding in unexpected places like nosebleeds or blood in the urine. It can also speed up the progression of kidney failure. The list goes on so any unexplained physical or behavioural change warrants a blood pressure check, especially in older cats. How is high blood pressure diagnosed? The only way to tell if a cat has high blood pressure is to measure it. The process is much the same as it is in humans – a cuff is inflated around the arm or leg (or possibly the tail) which controls blood flow to the limb. A special device (sometimes a handheld Doppler unit or sometimes an automatic sensor) then measures the blood pressure. It doesn’t hurt and isn’t usually a stressful process that is good because if the cat is stressed the reading can be artificially elevated. Sometimes the cat objects to the cuff being tightened so it can help to practice a few times before taking the reading. Some cats just plain hate going to the vet or any kind of restraint whatsoever so it isn’t always possible to get a reading, although many clinics have special protocols in place to help the cat stay as calm as possible before attempting to take a blood pressure. If all else fails in the clinic, a reading might be possible at home where they are more comfortable. Is there any treatment? Absolutely. There are several medications that can treat high blood pressure but the one that most vets use these days is called amlodipine. A very tiny dose goes a long way, and it’s important that once you start the medication, you give it regularly to avoid dangerous spikes in blood pressure. Once a cat starts the medication (usually a tiny tablet that most cats seem to tolerate relatively well) it’s important to follow up with regular blood pressure checks to ensure that they are on the correct dose. I’ve seen many cats respond very well indeed to treatment and many owners report that their cat seems years younger once their blood pressure is under control, even if they hadn’t noticed any symptoms in the first place. It is yet another example of how well cats can hide their illnesses and how important it is for owners and vets to work together to detect health problems while there is still time to treat them effectively. If you think your cat is showing signs of high blood pressure or if you have an older cat with unexplained physical or behavioural changes, please speak with your vet about having their blood pressure checked. You may never know unless you make an effort to look for it. Amy Bergs DVM MRCVS  - Visit The Cat Doctor website by clicking HERE
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