Summer is here
and a hot topic during these months is whether or not to administer heartworm
medication. This topic is extremely personal and I’d rather not give a definitive
‘yes or no’ answer to. There are multiple factors that can affect how much risk
our dogs, ferrets, and cats are to developing heartworm. Rather, I will discuss
how heartworm develops and provide you with alternatives to heartworm
medications and allow you, as a responsible owner, to make a decision. When you
understand the enemy you’re up against, it makes the battle much easier.
 |
| Picture taken from http://www.martindaleanimalclinic.com/heartworm-disease/ |
Firstly, I would
like to start by saying that by blindly administering heartworm medication
simply because it is warm outside or because the calendar says it’s May, is the
wrong reason to give Heartworm drugs. Let me explain to you why. Heartworm, Dirofilaria immitis, cannot develop if appropriate environmental conditions are not present. Like all living organisms on planet Earth, heartworm, too, must follow biology to become a risk to our pets. They simply do not magically appear out of thin air. In case you were wondering, heartworm is not limited to cats and dogs; ferrets can also become infected with the heartworm parasite. However, cats and ferrets do not typically cycle the parasite back to the mosquito (Brooks, 2012).
What is
heartworm?
Heartworm is a
parasitic roundworm that lives in the heart and pulmonary
arteries of dogs, cats, and ferrets. It is
spread to the animal by being bitten by an infected mosquito and releasing immature
worms or larvae called microfilaria onto the skin, which then penetrated the
bite wound and enters into the animal’s blood stream
(Brooks, 2012). Once in the blood stream, it takes approximately 6
months for the microfilaria to leave the skin, circulate the body, and reach
the heart where they can develop into adult heartworm (Fudens, 2014).
How does it develop?
The key note
about heartworm is that it is not as simple as being bitten by a mosquito. Only
females carrying stage 3 microfilaria can transmit the parasite. If the microfilaria
is not a stage 3 larva, infection cannot occur. There are five stages of
development.
 |
| Picture taken from http://en.wikipedia.org/wiki/Dirofilaria_immitis |
Stage One: L1
-
When
adult male and female worms are present in the heart of the host, they breed
and give birth to microfilaria which circulate the body and can do so for up to
2 years before they die of old age (Brooks,
2012).
-
When
bitten by a mosquito, it sucks up the L1 larvae in its body to start the development
into the L2 stage (Brooks, 2012).
Stage Two: L2
-
The
L2 development into L3’s depends on temperate conditions (Brooks, 2012).
-
For
temperatures of 14 degrees Celsius, 57 degrees Fahrenheit, 45 days of consecutive,
day and night, temperatures must occur (Brooks,
2012).
-
The
warmer the temperature, the faster the L2’s will develop into L3’s (Brooks, 2012).
-
For
temperatures of 26 degree Celsius or higher, 80+ degrees Fahrenheit, at least 2
weeks of night and day temperatures must occur (Brooks,
2012).
Stage Three: L3
-
When
the mosquito bites the host, the L3 larvae are deposited onto the skin of the
host in a droplet of saliva (Brooks, 2012).
-
For
infection to occur, it must be humid enough for the larvae to swim into the
bite wound and into the host before the saliva evaporates (Brooks, 2012).
-
Inside
the host the L3 develop into an L4 over a time span of 1-2 weeks (Brooks, 2012).
Stage Four: L4
-
L4’s
live in the skin of the host for approximately 3 months until it develops into
the L5’s and ready to enter the circulatory system (Brooks, 2012).
Stage Five: L5
-
L5’s
are young adult worms that travel to the heart and pulmonary arteries to mate
and breed (Brooks, 2012). Approximately
5-7 months after infection (Brooks, 2012).
Is heartworm medication
a preventative?
No. Heartworm
medication is not a preventative. The medications are poisons that kill parasites
and microfilaria after the animal has become infected, it does not prevent the mosquito
from biting and infecting the animal.
*It is important
to understand that heartworm medication does not protect the dog from future
infection. It only treats after potential infection has occurred.
Are there
natural preventatives?
First and foremost,
a healthy immune system is always the best defence against anything. Feeding a
raw diet and minimal vaccinations are the best ways to keep the body working at
its optimal level. Having said that, although a healthy immune system is best,
it will not guarantee 100% that your dog will not contract heartworm. The
notion that a healthy, raw fed, dog with minimal vaccines cannot contract
heartworm is not true. Even healthy dogs have the potential to become infected
with heartworm.
Second, avoid the
time of the day where mosquitoes are most active. Between dusk and dawn is
typically when mosquitoes are most active due to the cooler temperatures. They avoid
direct sunlight. In addition, avoid letting your dog sit in the shade surrounding
wooded, forestry areas as humid, moist, spots are where mosquitoes love to hang
out around. Having said that, after a rainfall when the air is moist and humid
and there is not much direct sunlight, mosquitoes are very active so avoid
spending much time outside wooded, forestry areas.
- Garlic is a great
tool to repel parasites such as fleas, ticks, and mosquitoes from approaching the
animal. It also has cleansing properties within the body. I administer fresh
crushed garlic as a natural preventative myself, but do not solely rely on this
method.
- Keeping the pests
away that transmit heartworm is key. Natural pest repellents are a great
preventative for mosquitoes, as well as ticks and fleas. Make sure if you are using
one on your cat, it is manufactured for the use on cats. They are very sensitive
to certain essential oils and chemicals. Remember with natural pet sprays,
frequent application is recommended. Natural products simply do not have the
duration of effectiveness as chemical spray products do.
* I pair up a
natural pest repellent with fresh crushed garlic.
- Food grade Diatomaceous
Earth is another way to keep pests off of our pets. It cuts into the pests
bodies and dries them out so they dehydrate and die. However is MUST be food grade, others have nasty
chemicals that are harmful to us and our pets. Rubbing some into the pet's coat
keeps bugs off.
Should I give Heartworm
medication to my pet?
The decision to
give heartworm medication should be weighed by the risks of infection. Ask yourself
this:
1)
Are
temperatures appropriate for the development of heartworm in my area and for
how long? In all areas of Canada, when temperatures reach appropriate levels it’s
less than 4 months of the year and that is including the time it takes for the microfilaria
to develop into L3’s. Yet I would still get 6 doses for heartworm medication from my vet. That means I
would be dosing my pets during months when it is biologically impossible for
our pets to become infected.
2)
What
are my pet’s lifestyles like? Majority of pets I know do not sleep outside and
since between dusk and dawn is when they are most vulnerable of being bitten by
a mosquito, the risk is reduced.
3)
Do
my pets spend majority of their time near moist, damp, environments like wooded
areas and forests? If you live in the city, there is not as many moist, cozy area’s
mosquitoes like to hang out in which reduces the risk of infection.
*The link below shows
you a chart of the risk of infection in all US states.
Is there a healthier
program for administering Heartworm Medication?
For those of you
that feel the risk is too high to not give Heartworm medication, the link below
gives great information on the timing and dosing of different heartworm medications.
Most drugs can be dosed safety, with 100% effectiveness, 6 weeks after threat
of L3’s development has occurred.
Other Resources:
Bibliography:
Brooks, W. C. (2012, July 5). Heartworm:
The Parasite. Retrieved June 12, 2014, from VeterinaryPartner.com:
http://www.veterinarypartner.com/Content.plx?A=615
Fudens, J. (2014). Heartworm. Retrieved
June 12, 2014, from Dogs Naturally Magazine:
http://www.dogsnaturallymagazine.com/heartworm/
