Survey in _(year)_, by American Heartworm Society, revealed _______ dogs were diagnosed with hearworm disease across the US. This number has more than doubled in recent years.
The first case of heartworms was found in a ______ in the _____.
Heartworm disease means the animal
1. has heartworms (etiological agent) AND
2. animal suffers from the debilitating symptoms associated with the infection of hearworms
Applies to 1st stage larva of Dirofilaria immitis. Only talking about first stage larva and only when referring to heartworms in the definitive host.
Dirofilaria immitis found in its definitive host the canidae is found in 3 primary regions in the United States:
1st - Gulf coast
2nd - East Coast
3rd - Great Lakes
Concern that a subpopulation of heartworms in certain areas has developed resistance to heartworm preventative medications. What is this new strain?
This new subspecies of heartworms _______, this identified as subspecies to D. immitis and showed resistance to __________
The strain was isolated from a naturally infected dog in __________. It was placed in a Beagle to test the efficacy of four commercially available heartworm preventatives. Which one tested at 100% efficacy?
Northeast Georgia in 2006
This heartworm is most commonly found in large cats of Africa
A parasite that is infecting an animal that is not its definitive host will have differences, making it_______.
1. parasite will not be as big
2. will not reproduce as well
3. life span will be shorter
What makes heartworms spread so easily?
1. pet owners can't afford heartworm preventatives
2. confusing as to when they should start and stop giving preventatives
3. unwillingness to accept the possibility of heartworm transmission
Heart worm epidemiology:
Diagnosed Dirofilaria immitis all States including world wide from ______ to _______.
However there has been no recorded transmission to occur in _________ although it has been diagnosed here.
Europe to Asia
Most important factor contributing to further dissemination of Dirofilaria immitis disease (heart worms)
Relocation of infected, microfilaremic dogs
First appearance of heartworms in the United States:
Hennepin County, Minnesota in 1937
Stages of the Heartworm
include where each stage is found
Stage 4 - Pre-adult Stage - 2nd adult only (migrate under skin 100 days)
Stage 5a - Immature Adult Stage - 2nd adult only (in pulmonary artery 80 days)
Stage 5 - Mature Adult Stage - 2nd adult only
Heart worm Transmission
_____ is common in homes of US and effects both dogs and cats
50% of all dogs positive on occult test for Dirofilaria immitis, are known to be negative for microfilaria. Why?
1. All adult HW are same sex
2. WBC have attacked and engulfed the foreign proteins of the microfilaria
There is another filarid other than D. immitis that is transmitted by the flea. What is this filarid and the name of the flea?
Ctenocephalis felis "the cat flea"
Stage 1 of this blood filarid will appear almost identical in a direct smear to that of Dirofilaria immitis.
Why is it important to know the difference between D. immitis and A. reconditum?
Both filarids produce 1st stage larva that will appear in the blood. A. reconditum is not pathogenic and does not need treatment although it can be treated
History for diagnosis of heartworms, symptoms of a HW (+) dog:
"not doing well" - ususally reason owner brings animal in
loss of stamina
ascites - fluid in abdomen
front legs bowed out - due to stress, elbows will rotate out
Diagnosis of Heartworm Disease:
1. blood samples
2. history - usually reason dog is in clinic
Best and worst Diagnosis for microfilaria:
modified knots test
Hematocrit tube - worst for microfilaria
difil test - best for microfilaria
Best diagnosis test for Heartworms
Occult Test - antibody or antigen test
Why is the modified Knots test no longer used to diagnose HW?
A filtration test that used formaldehyde - this is a cancer producer
When diagnosing HW, radiology diagnosis is used to________
confirm severity of infection
Blood sample - Microfilaria
Fresh blood is taken from the vein and a drop is placed on the slide. Cover and observe for microfilaria in motion (____)
Direct Smear 64%
Blood sample - Microfilaria
Utilizes formaldehyde 2% and a centrifuge method to localize the microfilaria at the bottom of a tube (____)
Modified Knot's Method 84%
Signs of caval syndrome
Heart will appear as an inverted D shape on echochardiogram and a cap over pulmonary artery
Blood sample - Microfilaria
1mL of blood mixed with 1mL of lysing solution and filtered through difil paper. Paper is stained and viewed.
Difil (Millipore filtration test) test - most reliable in detecting microfilaria
Blood sample - Microfilaria
blood is spun down for a PCV check. View above the buffy coat to see the microfilaria moving around. Efficacy?
Microhematocrit Tube test
Poorest of the diagnostic blood test
Poorest method for diagnosing microfilaria
When differentiating D. immitis from A. reconditum in a difil test we look at the anterior end. What difference is visible to us?
A. reconditum anterior end is blunt
D. immitis anterior end is tapered
Blood Sample Occult tests
Two types of Occult test:
1. Antibody Test - MAT (microfilaria antibody test) and DAT (dirofilaria antibody test)
2. Antigen test
Occult test of choice and the most diagnostic test on the market
These Occult tests are no longer used since the antigen test is considered far superior in diagnosing Heart Worms
MAT - microfilaria antibody test
DAT - dirofilaria antibody test
3 medications that will react to the microfilaria resulting in anophylactic chock and death
1. milbemycin oxime (Interceptor - Novartis)
2. organophosphates (Diclorvus)
3. Diethylcarbamazine citrate (DEC)
What are reasons as to why we would get a false negative heartworm (1)antibody test and a false negative heartworm (2)antigen test:
1. antibody - Will get a positive if there are ANY foreign worms in the body. Other parasitic worms are detected other than D. immitis
2. antigen - some animals have developed immune complexes against the antigen test giving a false negative
Any test that detects antigens or antibodies is considered an _______
Companion Animal Parasite Control (CAPC) recommends what testing to veterinarians?
Microfilaria and antigen tests annually on dogs including those on HW preventatives
Why can't we use the antigen test to detect HW in cats?
There are not enough adults present to get a (+) antigen test. We use the antibody test instead
Two Antigen test available for detecting circulating HW antigens.
ELISA (Enzyme Linked Immunosorbent Assay Test) and immunochromatographic test
We can reconcile unexpected negative results by simply __________
retesting with a different test
Was once written that all antigen test required at least _______ to get a positive antigen occult test. This is not held as absolute today.
three mature females
A graded test reaction can be recognized by __________ but quantitative results are not displayed by ___________.
ELISA test systems
This antigen or ELISA test can be run individually or as a group of tests, which is called ________.
Other causes of false negatives on a Heartworm test
(1)blood sample not warmed up to room temperature, (2)infection is light, (3)female worms have yet to mature, or (4)they are only males in this infection
Before starting heart worm treatment the American Heartworm Society recommends ________
confirming all positive ELISA test
Largest test labs in United States.
These labs checked over _________ in 2010 using exclusively antigen and not antibody tests.
Idexx and Antech
Why aren't more dogsprotected from HW each year?
1. 24% of pet owners don't spend money at clinics, instead they get their info and products from Wal-Mart or Petco
2. Clients have no understanding of HW
3. Prices of treatment and prevention deter clients
4. 1/3 of all pet owners only go to the vet for vaccines
5. 1/3 only go when animals are sick
According to research, the two items critical in persuading clients to further health care are _________ and _________.
communication and consistency
Why are ELISA test not as sensitive to Heartworms in cats?
1. due to low heartworm burden
2. immature female heartworms in the early stages of development
3. strictly male infection
Overall, the most useful tests to confirm heartworm infection in cats are _________ or ________ or __________
Serology (antibody levels or antibody test)
thoracic radiographs - still not useful
echocardiography - still not useful
Best heartworm testing for cats is _________ not thoracic radiographs or echocardiography, why?
serology (antibody) - antibody levels or antibody testing
why? because there are not enough heartworms present to get a positive test
Clinical picture of heartworms in cats. (What causes death)
If cats have a male and female they will attach to chardi tendani on tricuspid and mitral valves and release when the cat breathes taking them to the pulmonary artery and then to the lungs. Adults caught in the Pulmonary artery and block the flow. Cat will die in minutes due to hypoxia
_____ - lack of oxygen to the tissues
After treating animal for a heart worm infection you must wait to retest with an antibody test or you can get a false positive. Explain.
antibody test will only show whether an infection occured. It will detect antibodies still present from a previous infection even when no adults are present. It will detect the hormones still present in the blood
This test is most useful in testing for heart worms in cats; checks for the antibodies produced by the immune system when the body is fighting a heart worm infection.
An immune response can be produced by both male and female heart worms and the response is seen as early as ____________.
2 months post infection
When testing for heart worms this is the most logical test to run on asymptomatic cats.
What is the downside of the antibody test?
antibody test can only show whether an infection occurred. It cannot show if the animal is still infected
Changes typically seen in a positive heart worm canine radiograph
1. enlargement of the pulmonary artery at 1 o'clock
2. enlargement of the right side of the heart commonly called the "inverted D"
Which 2 views do we use when diagnosing heart worms via radiograph? If positive what can be seen with each view?
1. lateral view - heart is enlarged more than 5 ribs in length
Changes that can be seen in a heart worm positive cat:
What can not be seen due to the low HW burden?
1. enlargement of the main lobar and peripheral pulmonary arteries
2. the pulmonary artery is greater than 1.6xs the width of the ninth rib
no "inverted D"
The body wall of an adult heart worm is highly echogenic, therefore a positive echocardiograph will show the worms appearing as _________ where the imaging plane cuts across loops of the parasite.
These are novel parasiticides and insecticides that are produced through fermentation by soil-dwelling microorganisms
Macrocyclic lactones includes the following preventative medications
Macrocyclic lactones are highly therapeutic possessing anthelmintic activity against _____, ______, and in some instances ______________.
microfilaria, 3rd and 4th stage larvae, young adult heartworms (S5a)
Prevention of heartworm disease medications
1. This is an oral medication to be given daily as a HW preventative by Pfizer (now called _____) would kill stage 3 HW and came in the proprietary name of Filarabits, Nemacide, Dirocide
DEC diethylcarbamazine citrate
2. An oral manufactured by Bayer, came in the proprietary name of Heartgard. For dogs and cats
3. Oral by Novartis - Interceptor
4. Oral by Novartis that would kill other parasites as well as being a HW preventative - Sentinel
Milbemycin oxme + Lufenuron
5. 1st topical HW preventative by Pfizer (____), also took care of other parasites such as intestinal parasites, mange mites, etc. - Revolution for dogs and cats
6. 1st inject-able HW preventative by Ft Dodge - Proheart 6
7. Topical by Bayer - Advantage Multi for dogs only
Imidacloprid + Moxidectin
Liquid Diethylcarbamazine Phosphate is
A non-macrocyclic lactone that was the first oral heart worm preventative. To be given daily, would kill only S3 larva and would react with S1 microfilaria.
DIC - diethylcarbamazine citrate
Before starting prophylaxis with DlC __________ is mandatory
testing for microfilariae
This product was dispensed as a liquid in the food of dogs in the early 70s, for dogs that would not take a pill or for owner with many dogs. A non-macrocyclic lactone, Styride Caricide - last of this product was "Dirocide"
DIC may be started on dogs with _____ infections only.
adult heart worm
Oral heart worm preventatives of importance:
Heartworm preventatives that will react with S1 larvae, microfilaria
Organophosphates - Diclorvus (Task)
Protocol for heartworm prevention concerning Ivermectin and Milbemycin oxime (this is no longer considered effective in places like Houston)
recommended to be given one month before heartworm season up until one month after heartworm season
1st alternative to DEC
"heartgard" by Merial
killed L3 and L4
oral (chewable), every 30 days
1st heartworm preventative made for the feline
Ivermectin dosage for dogs
Ivermectin also came as Heartgard Plus when __________ was added
Pyrantel Pamoate - added for intestinal parasite control
50% of dogs with heartworms will be negative for microfilaria, why?
wbc are doing their job and engulfing the microfilaria
all adult heartworms are the same sex and cannot reproduce
Family Avermectins include:
Warning with Ivermectin. What dogs are unusually sensitive to high doses of ivermectin
Collie dogs have autosomal recessive inheritance
and other glycoprotein deficient dogs
Interceptor - Novartis
L3, L4, hooks, rounds, and whips
given once a month
* used off label - sterilize M HW and lessen life expectancy if given 3-4 months
Milbemycin oxime + lufenuron
Sentinel - Novartis
Oral ovitrol effect - prevents formation of chitin
L3, L4, hooks, rounds, and whips
flea must bite the dog. does not kill the adult
Mechanism of action of avermectin and Milbemycin oxime
Suffocates the parasite.
Behind the neuron transmitter glutamate chloride channel between a nerve and the muscle. This interrupts communication from CNS and does not allow the muscle to activate. Prevents breathing, suffocate and die
To topical products for heartworm prevention on the market today:
2. Moxidectin + imidacloprid
Revolution - Pfizer
dogs 6-7 wks and older
1st topical to protect against heartworms and fleas