The Deadliest Insect on Planet Earth

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

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

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AMH

Baby Heartworms - Video

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

Honking Dogs - The Kennel Cough Complex

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