The Deadliest Insect on Planet Earth

Posted by Aaron

Monday, October 26, 2009


I didn't forget my blog. I left the influenza post up a bit longer because I kept getting questions from folks about it.

We've had a TON of rain here lately and thanks to that, we've had a TON of mosquitoes. You may or not be aware, but the mosquito is considered the most deadly insect on Earth. Specifically, the female anopheles mosquito because she carries malaria. But there are many other genus of mosquitoes that are quite capable of transmitting other diseases as well.

Now, to be fair, the mosquito is not inherently evil. Annoying, itchy, and somewhat disgusting to look at, but the same could be said about so many of us from time to time. Mosquitoes get the bad wrap on this one because they are blood feeders and they feed on multiple hosts over the course of their lives. This means that they, in essence, swap blood from one individual to another.

Certain parasites have taken advantage of this biological fact. Malaria organisms hitch a ride with mosquitoes and infect another person via the mosquito saliva in an infected bite. Heartworm is another example. Larva are picked up with a blood meal, molt twice in the mosquito, and then infect the next animal through the bite wound from the mosquito. Most viruses can't hitch a ride with mosquitoes, but there are some notable exceptions - mainly West Nile Virus and the equine encephalitis viruses.


Different mosquitoes have different preferences in what they feed on. Some only feed on birds, for instance. Others will freely feed on anyone including dogs, cats, people, and horses. The feeding habits of a mosquito will decide what kind of threat that particular buggar represents.

I will often see outdoor cats with little crusted bumps on the ears and upper nose, and similar areas on dogs where the ears fold over or on the bridge of the nose. These can be little bites from mosquitoes or flies and may be an indication that repellent would be appropriate.

How to protect you and your pet:

Avoidance. Mosquitoes are active near dusk and dawn. They don't like to be out in direct sunlight and don't like high winds. If you are having a hard time with mosquitoes (like we are lately), then avoid keeping your dogs and cats out during that time.

The second line of defence will be repellents. There are fewer repellent options for dogs than there are for people. Any permethryn containing product will likely be repellent to mosquitoes. Bayer's Advantix and the Vectra 3D are examples of products that have "repels mosquitoes" on the label. I've also had folks tell me they've had good luck with the Avon Skin-so-Soft products. Spray a wipe and then wipe the fur of the dog, specifically getting the tips of the ears. In theory DEET should work, but I just don't think DEET is safe. You must wash it off and that makes it impractical for most owners on a day-to-day basis.

DON'T FORGET YOUR CATS! There are even fewer options for cats than for dogs. All of the permethryn products labeled for dogs will likely kill your cat, and that's just counter productive. There are pyrethryn products that may work, and the Skin-So-Soft trick may work. You must be more careful with all of the flea, tick, and mosquito control products in cats.

MOSQUITOES WILL GET INDOORS, TOO! Having an "Indoor only" dog or cat does NOT mean that their risk of heartworm disease is eliminated. All cats and all dogs should be on preventative year round - especially those dogs and cats living in more temperate climates.

The moral of the story is that many owners forget about mosquitoes if they are not outside being bitten. Mosquitoes happily feed on your pets and they do carry with them the potential for disease. Keep your pet current on preventatives and, if appropriate, use a safe repellent for your pet.

AMH

Canine Influenza - Yet ANOTHER flu bug

Posted by Aaron

Sunday, October 11, 2009




It is rather exhausting to hear so much about influenza. There is a fine line between caution and panic. The media has make this line difficult to identify. My goal here is to prevent as much fact as possible with an occasional injection of opinion.
Influenza is a HOT topic. When words like pandemic and enzootic are used it tends to make people very nervous. The moral of the story: Be cautious, be aware, but DO NOT PANIC.
The Virus:
The images above are all of influenza type A virus. Influenza A virus are further characterized by their H and N subtypes. Swine influenza is H1N1. Horse is H3N8. Seasonal flu is H3N2. The canine influenza that is causing all of the current panic is the H3N8 subtype of virus. This is because there was a jump at some point in history from the horse to the dog.
The current episode of canine influenza is dated to 2004 when there was a rather dramatic epidemic in a racing greyhound population that killed many dogs. Although we have seen influenza steadily since then, serum samples taken from dogs as early as 1999 have been positive for H3N8 virus. Those may have been previous jumps or they may represent the same virus we are seeing now. It's hard to know what used to be around when we weren't looking for it back then. All we can really say is what is here now and keep looking to know what is here in the future.
Transmission/Infection:
The disease is transmitted in exactly the same ways that the human influenza is transmitted. It's stinkin' contagious and is capable of spreading quickly through dense populations. Dogs infected with virus typically have a 2-5 day incubation prior to showing symptoms. They are then "sick" for a period of approximately 5 days. The cough may last weeks longer.
Dogs shed virus several days prior to showing symptoms. This is part of the frustration with the disease because dogs can infect others long before we even know they are sick.
The disease appears to be enzootic (permanently in a population) in Florida, New Jersey, New York, Colorado, and California. It has been diagnosed in 31 states (including Texas) but is still spotty in those states and has not been shown to be permanently in the population.
Transmission is most reliable in situations where a dog is in a larger population of closely housed dogs. This includes: boarding, grooming, dog shows, traveling with the family, dog parks, day care, and racing greyhounds.
Disease Symptoms:
Nearly every dog exposed will become infected. Of those dogs 80% will show some symptoms. Of those dogs 95% show little to no disease and what they do show is limited to:
Cough (deeper, chesty cough)
Mild fever
Lethargy
Nasal Discharge
5% of infected dogs will become more severely ill and those dogs may develop:
Pneumonia
Anorexia
and in rare cases hemorrhagic disease and death.
Greyhounds appear to be exceptionally sensitive to the virus and they nearly always develop more severe disease.
These statistics are smackingly similar to human influenza, yes? I think most dogs are actually at lower risk of exposure than many humans. We humans are such social creatures and are always interacting with random members of our species. We touch door handles, shopping carts, phones, hands, and breathe the same air on public transportation. Aside from the dogs in the at risk population listed above, your dog is probably in a much more controlled environment than you are.
Treatment:
Supportive care. Plenty of water, controlled environment (don't leave a sick dog outside in the cold, wet weather), and watch closely. If the cough is severe enough we will use cough suppressants. If we are dealing with a very young dog, very old dog, or dog with history of cardiopulmonary disease, we may use an antibiotic. Notice how this sounds exactly like how we would treat any old "kennel cough?"
In a few, very sick dogs veterinarians have tried Tamiflu. There are no controlled studies to prove if this works and there are few dogs that are sick enough to warrant treatment. It is NOT recommended for prevention of disease!
Prevention:
Avoid high density situations if there is a local outbreak. Use common sense and if a dog has a cough - DON'T TAKE HIM TO THE PARK OR TO DAYCARE! My daughters have to stay home from school with a fever. Doesn't matter how good they feel. Any fever, vomiting or diarrhea and they have to stay home. It is encouraged that a child with a severe cough not be sent to school. Same concept goes for your dog.
And now the big question: What about the vaccine? Not to sound too redundant, but this is yet another hot topic. Here are a few facts about the vaccine:
  • It has only existed on the market for a few months. It looks like it will be a safe vaccine, but it's still new.
  • The vaccine is not labeled to prevent disease or eliminate infection - it is designed to reduce severity of clinical signs, shorten disease course, and reduce shedding of virus
  • It requires an initial dose followed by a booster 2-4 weeks later. It must then be boostered annually.

As with any vaccination of its type, protection will not happen until around 10 days AFTER the SECOND vaccine. So you must plan ahead if you want your dog "protected" prior to entering a boarding facility. You need a MINIMUM of 24 day lead-time and closer to 5 weeks is recommended.

Which dogs should get the vaccine? High risk dogs (see the above list) and especially high risk dogs traveling to or living in the areas of NJ, NY, CA, CO, or southern Florida.

Your veterinarian may have identified a local outbreak of influenza and may feel that vaccination for your pet is important regardless of where you live. Always follow your primary care veterinarians recommendations regarding what vaccinations are recommended for your pet.

I don't have statistics regarding the H3N8 in other countries. I would imagine it is in Canada and Central America, but nobody has mentioned this on my discussion boards. I'll keep looking.

AMH

New Guestbook

Posted by Aaron

Saturday, October 10, 2009

Check out the new Guestbook. Please sign in so I know where you are visiting from. Comments always welcome (especially if they are positive)!

AMH

Baby Heartworms - Video

Posted by Aaron

Friday, October 9, 2009

I had a heartworm positive dog come see me today. We checked for microfilaria (baby heartworms) and in one drop of blood there were dozens of them. I shot a couple of quick videos. The little worms are easy to spot. They literally are little round worms and they wiggle just like an earthworm. All of the red dots around them are red blood cells. Some of the red cells are stuck together, but on one video it is easier to make out individual red cells. The worm is just a bit thinner than the diameter of a red blood cell.


Enjoy!

AMH
video video

Honking Dogs - The Kennel Cough Complex

Posted by Aaron

Thursday, October 8, 2009

A cough can be caused by different things and can sound different depending on what causes it. For instance, a deep, productive, wet cough may be more typical of pneumonia (in the UK, I saw this referred to as a "chesty" cough). Tracheal irritation will cause a typical "goose honk," non-productive kind of cough. Debris on the larynx (like post-nasal drip or laryngitis) will usually cause of hacking kind of non-productive cough. (Think croup in children)

I wanted to specifically mention Infectious Tracheobronchitis (ITB), a.k.a Kennel Cough, a.k.a. Contagious Canine Cough Complex. The names alone should suggest that it is not as simple as a single bacteria or virus causing it. We are talking about a complex of diseases.

The most famous culprit is Bordetella. This bacteria is WICKED contagious and can cause all kinds of upper and middle respiratory issues. It is a very close cousin to whooping cough in people. Other known causes of the ITB complex include:
Parainfluenza
Mycoplasma
Strep equi (var zooepidemicus)
Canine herpesvirus
Canine respiratory coronavirus
Canine influenza virus
Canine adenovirus type 2
Canine distemper virus (CDV)

The above list includes a paltry three bacteria with the rest being viral. The most common cause of all appears to be the parainfluenza virus. Bordetella is often blamed, but is not often the cause. It is also important to note that these viruses don't always act alone. A co-infection with bordetella when you already have parainfluenza can cause a nasty infection where either alone may be harmless.

Because ITB is infectious, it is most commonly associated with animals in a high-density setting. This includes boarding, grooming, shelters, play parks, daycare, or dog shows. HOWEVER, because it's so stinkin' contageous, it's not uncommon for me to see a dog with typical "kennel cough" that has not stepped foot in a kennel in months! Cats or dogs coming through the yard, visiting dogs coughing on the fence, or dogs sharing a patch of grass at the park or in the apartment building shortly before your dog does can all be sources of infection.

When I am presented with a dog who is otherwise healthy (no history of respiratory, cardiac, or immune system disease) and ONLY has a tracheal cough, I rarely treat with antibiotics. If they are very young, very old, or have other issues, I may use an antibiotic. Why? Because the infections are nearly always self-limiting. If I treat with an antibiotic, the patient will nearly always get better in 5-7 days. If I don't use an antibiotic, they patient will nearly always get better in 5-7 days. There are exceptions to every rule, and if the patient isn't responding or gets worse, I will intervene earlier.

I try to reserve the use of antibiotics to only those times I feel there is evidence that antibiotic use is necessary. The goal is to prevent antimicrobial resistance. For me, that's a pretty danged important goal.

That's how I handle it. I have many colleagues that treat all coughing dogs with antibiotics and I can't fault them for it. The argument for antibiotics include:
1) It can't hurt
2) The problem may resolve faster with antibiotics
3) I can't prove it is viral, so I should protect against the possible bacteria that can cause more severe infection.
4) That doctor's local population of animals seem to get particularly nasty infections and regularly require antibiotics.

Because these guys usually have WICKED coughs, I will give a cough suppressant to help everyone get some sleep. The most effective cough medications are narcotics (i.e. hycodan), but there are others that may work well. Our supply of narcotic cough medications has been dicey at best over the past few years, so we use what we can when we have it. An alternative to hycodan if it is not available is tramadol.

Vaccination:

Here's a hot topic! We can vaccinate for Bordetella, Parainfluenza, Influenza, and Adenovirus. None of these vaccines are perfect and we consider them likely to protect against severe disease, but NOT ALWAYS protective against infection. There's just too much variation in the wild-type bacteria and viruses. So YES, a vaccinated dog can get "kennel cough." It doesn't mean the vaccine wasn't given correctly or failed. There are just too many variables.

The influenza vaccine is new and in my opinion, the jury is still out on whether it will be worth using much. I've had two requests to blog on influenza virus. I'll get the rest of my data together and post on that one soon.

How often should a pet be given a "bordetella" vaccine? That depends. Some vaccines peter out after 6 months. Some have been proven to last one year. The most common protocol you will find is every 6 months. Even when I was using a vaccine that I felt worked for at least one year, groomers and boarding facilities required it every 6 months. I disagreed with them, but I was just the doctor. It's their facility. Is it hurting to give it every 6 months? Doesn't appear to be, but this goes back to the discussion of how many vaccines are enough and how many are too many.

Religion, Politics, and Vaccination - topics never to be discussed in mixed company ;)

Moral of the story:
I have LOTS of cases of "kennel cough" come to me every year. Most are viral, some are bacterial, and (in my hands) nearly ALL of them go home with cough medications only. A few end up with antibiotics. Think of it as the common cold for dogs. You just have to ride it out. Annoying, but rarely more than that.

AMH

Pill Poppin' Pets

Posted by Aaron

Tuesday, October 6, 2009

Now that we know more about how and why pain happens and is perceived, we can talk about how to treat pain.

Different types of pain come from different places. Remember the pain starts at the receptor somewhere out in the body and is then carried upwards towards the brain with a couple of junctions along the way. Depending on the patient, nature of the pain, and duration of the pain, we may change exactly how we treat different pets with similar problems.

Classes of drugs:
Local anesthetics
Lidocaine, bupivocaine, carbocaine are all examples. These drugs work by short circuiting the nerves carrying the signal. If they can't generate an electrical charge, the signal never makes it upstream. This can be done locally (like the spray you spritz into your throat when it's sore) or injected near a nerve (like when we do ring blocks for declaw procedures) or into the spinal column itself. Anywhere the drug goes, there will be no pain sensation generated. These drugs don't last long. For instance, lidocaine only lasts a couple of hours. Bupivocaine lasts about 12 hours when injected.

NSAIDs
Non-Steroidal Anti-Inflammatory Drugs. These are drugs like ibuprofen (for PEOPLE ONLY), carprofen (Rimadyl), meloxicam (Mobic, Metacam), and ketoprofen (Ketofen, Orudis). This is a class of drugs that is very popular because they work well and are available over the counter on the human side. NSAIDs work by blocking the enzymes that generate pain causing chemicals and decreasing the amount of pain generated. NSAIDs work out at the SITE of where the pain is starting. NSAIDs are usually our first-line pain medications for osteoarthritis, post-operative pain control, and trauma pain management. They are often used in conjunction with a narcotic.

CAUTION: NSAIDs are a class of drugs that can be fantastic in dogs and cats, however, they must be used with caution and ONLY under the advice/supervision of your veterinarian. Cats in particular are sensitive to this class of drugs. DO NOT GIVE ANYTHING OVER THE COUNTER WITHOUT FIRST TALKING TO YOUR VETERINARIAN.

Narcotics
Also referred to as opiates because most all of these either came from or are related to opium and its derivatives. Opiates function in large part in the spinal cord. They decrease the amount of pain signal that is allowed to jump from the nerve carrying the signal from the periphery to the nerves in the spinal cord. They work in a couple of other places as well (brain).

Opiates are fantastic for all kinds of pain, from mild to severe. Opiates also have the unfortunate side effect of being prone to addiction because of the change in brain chemistry that happens with chronic use. Because they simply block the receptors in the central nervous system, the receptors can respond by making more of themselves. This means it takes more drug to work. We refer to this as tolerance of the drug. We have to increase doses to match. Bigger doses, longer term use and we're now talking addiction. Addiction does happen in our pets. It "looks different" because your dog won't loose his job, family, house, and friends over addiction, but the underlying physiologic response is the same - the body NEEDS the drug after it has had the drug for a period of time. Long term use of opiates must only be done under the direct management of your veterinarian.

Opiates are frequently combined with NSAIDs (think Percocet, Vicoden). This accomplishes two things - first, it provides two modes of pain control in one pill. They ALWAYS work better together than either one will work alone. It also makes them hard to abuse because the more NSAID you take, the more likely you are to have problems with the NSAID. It also makes it hard to cut the drug for street sale.

Opiates are all Scheduled drugs. This means the DEA tracks each and every tablet and drop of narcotic produced in the USA from the manufacturer to the patient. Your veterinarian has to keep lots of records on controlled/scheduled drugs. The more likely a drug is to cause addiction or abuse, the more tightly the DEA is in control of it.

Tramadol (Ultram) has become a darling of veterinary medicine. It is not a narcotic, but is narcotic-like. It also has some nifty effects in the brain where it increases seratonin levels. So even if you're in pain, you don't care (sort of). Because it's cheap, effective, and not controlled we veterinarians LOVE the stuff. Rumor has it that tramadol may become a controlled drug. We'll see. We'll still use the heck out of it, but it will make our lives a bit more difficult.

Amantadine and Gabapentin
Amantadine and gabapentin are medications that are used along WITH other pain medications. Both of these (although through different actions) help to change the way the brain and spinal cord react to CHRONIC stimulation of pain pathways. Chronic pain can cause these pathways to be "turned on" all of the time. Over time, these pathways can be permanently turned on or can be so freaked out that they don't know how to tell the difference between a little pain and a lot of pain. In some cases of chronic pain, amantadine can bring huge relief where our usual arsenal of drugs isn't cutting it anymore. These drugs take time to work and aren't used in the acute "I gotta have pain control NOW" setting.

Multi-modal pain control:
This concept means that we try to attack pain from different angles. When I am doing a painful procedure to a toe, for instance, I may do a local block at the level of the toe to try and block the signal from starting. I will also use a narcotic at the time of the procedure to help block any signal that makes it past my local block. I'll also give an NSAID so that when the local block wears off, the NSAID has had time to block the inflammatory chemicals from being made and the patient is, in theory, not painful. I've now blocked the pain signal at just about every available level. By using all three, I can use less of each and have a much better effect than I would by using only one drug alone.

There are literally entire books published on this subject, so I'm not trying to cover it all. Just trying to give you more information.

One last thing:
Some veterinarians still offer pain medications as "optional" after surgical procedures. Others make it a requirement. I require it and without fail I would have a few owners get upset that they were being sent home with pain medications when the pet didn't "look painful." 99% of the time, the complaint is that they have been asked to pay for the medication. Remember that pets don't show pain the way we do. They may be in significant pain, but not show it in an obvious way. Painful animals usually rest more than usual, have trouble getting comfortable, have increased breathing and heart rates, may refuse to eat, and may be more aggressive than usual. Cats are especially bad about hiding pain. They will seem to just be sleeping more than usual, when they are actually in quite a bit of pain.

Because it's nearly impossible to predict which pets will be more painful than others, we should ALWAYS TREAT THE PET AS IF THEY ARE PAINFUL. If pain medications are optional for you - TAKE THEM!!!!!!!! If they aren't optional - TAKE THAT AS A SUGGESTION AND USE THEM AS DIRECTED! Bone pain/amputation pain is usually the worst, followed by supporting muscle pain, neurologic pain, and organ pain. Trust me, after I have removed your dog's uterus, she's painful. After a de-claw (amputation), I can GUARANTEE your cat is painful.

Well controlled pain = faster healing time (well documented that this is true!), less stress, lower stress hormones, less susceptibility to secondary infection, and a happier pet!

AMH

OUCH! That Hurt! Pain Perception and Control

Posted by Aaron

Thursday, October 1, 2009




In this post we'll talk about what pain is and how it is perceived. Next post I'll talk about some specific pain medications and methods for dealing with pain.

We've all felt pain. Pain can be acute (cut finger, broken leg, twisted knee) or can be chronic (spinal pain, compressed disk, arthritis). Different types of pain require different approaches. I thought I'd do an overview of different types of pain management and talk a little bit about the way animals perceive pain.

First thing first. Let me say this loud and clear. ANIMALS FEEL PAIN.

All of us mammals are essentially wired the same way. The nerve endings, nerve fibers, and nerve junctions are all pretty darned similar. So a broken leg hurst no matter what species you are talking about. Where's the difference between people and animals?

Animals PERCEIVE pain differently than humans.

Even though we are wired the same, that signal has to be interpreted by the brain for you to have concious knowledge of that pain. This explains why I have seen many dogs walk into the emergency hospital DANGLING A LEG behind them. It is also why I've seen a cow get their horns sawed off and they walk right out into the field and start eating as if nothing ever happened.

There have been many excellent studies looking at pain perception in various animal species. Each have these have shown that animals definitely perceive pain. However, there is a difference in what kind of pain they perceive and what it does to their body.

Every individual is different.

Some people have a very high pain tolerance and don't seem to hurt too badly even though they have a broken arm. Others cry and are severely affected by a paper cut. This is also true in our pets. Some require more pain medication than others.

The Anatomy of Pain:

Pain perception starts at a nerve ending somewhere out in the body. Let's use the toe as an example. When the pain receptor is triggered (like the toe is squished or the skin is cut), those receptors fire off a signal to the spinal cord. The signal is linked in the cord to another nerve that sends the signal up to the brain. Once in the brain, the signal is perceived both consciously and sub-consciously. This is an over simplification, but the point here is that pain happens at multiple, yet different levels in the body. When considering the pain in the toe, there are at least three locations that I can treat to eliminate the pain being "felt" or "perceived" by the individual.

Ever had novacaine at the dentist? This is an anesthetic that numbs up the nerves at the sight that the medication is given. That way, the nerves never get a chance to fire.

Ever taken an ibuprofen? Drugs like this work by keeping the chemicals that stimulate the pain signal from being produced. The idea is that if you decrease the chemicals, you eliminate the pain signal all together. In other words, by cutting inflammation, it reduces the stimulation of the signal, and reduces pain. (NSAIDs, COXIIB)

Ever had morphine? Narcotics main action occurs in the spinal cord, although they do a fair amount in the brain as well. Narcotics keep that signal from jumping from the nerve that sent the signal to the nerve that carries the signal to the brain.

And then there are the drugs that affect the brain chemicals that make us either more sensitive to pain or take away that sensitivity. In other words, they help change whether or not we give a damn that we're painful.

So in people and in animals, there are many, many different places that pain can be modified. This helps explain why there are such different responses from different individuals. Depending on your body chemistry, your brain chemistry, your specific genetic make up, you may have more or less sensitivity to pain. Cows are NOT as sensitive to pain as poodles. It's a fact. They both FEEL pain, but they don't PERCEIVE it the same.

Acute pain is handled differently than chronic pain. Over time, these pathways I've described above can become hyper-active or can be blunted. So chronic pain may require different targets to get the pain response to either shut down or start up. Acute pain can be easier to manage for this reason. The pathways are more predictable and we can use drugs in the short term (narcotics that sedate) that wouldn't be smart to use long-term (narcotics and addiction).

I'll stop there for now. Next post we'll talk about specific pain medications and how they can help.

AMH