Parasite control programs for dogs and cats pt 2 Flashcards
heartworm life cycle
- A mosquito bites an infected animal, ingesting heartworm microfliariae (pre-L1)
- Microfilariae mature into heartworm larvae (L3) inside mosquito (10-14 days)
- Infected mosquito bites a dog, transmitting the larvae (L3)
- Larvae enter the dog’s bloodstream, migrate to the heart and lungs, grow to a foot long and become sexually mature (7-9 months)
- Adult heartworms can live within the heart and lungs for 5-7 years
Heartworm in Ontario - where are most cases diagnosed?
~80% cases south of highways 402/401/403
Heartworm in Ontario
- How likely is a dog to get infected ?
- overall prevalence
- who is mostly testing positive?
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- how common is disease in dogs?
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- How likely is a cat to get infected ?
- overall “prevalence” = 0.13%
- imported infections constitute 29% of total
- 83% positive dogs not on heartworm prevention in previous year
<><><><> - ~88% heartworm-positive dogs had subclinical infections
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How likely is a cat to get infected ? - ~100th risk of infection in dogs (in Ontario)
Oral heartworm preventives for dogs
- what drugs are routinely used in ontario? what other parasites do these products protect against?
Ivermectin + pyrantel
- Dirofilaria, toxocara, toxascaris, ancylostoma, Uncinaria
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Milbemycin
- Dirofilaria, toxocara, toxascaris, ancylostoma, Trichuris
> also can be combined with praziquantel for tapeworms (D. caninum,T. pisiformis, E. multilocularis)
Echinococcus multilocularis in southern Ontario
- disease in dogs? concerns?
- how do they get this?
- should we treat?
- Reportable infection in dogs (2018) > zoonotic, bad human disease
- Dogs only develop intestinal infections
if ingest rodents – public health concern - Monthly treatment with praziquantel
(multiple products) prevents eggs shedding - Only high risk dogs in high risk
Wild canid
households
Topical heartworm preventives for dogs available in ontario
- what drugs are included, and what other parasites are they effective against
selamectin
- Dirofliaria, (toxocara), ctenocephalides, otodectes, sarcoptes, (dermacentor), rhipicephalus
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moxidectin + imidacloprid
- Dirofilaria, toxocara, toxascaris, ancylostoma, Uncinaria, (trichuris), ctenocephalides, otodectes, sarcoptes
Injectable heartworm preventive for dogs
- what other parasites does it protect agaisnt?
moxidectin
- dirofilaria
- ancylostoma
- uncinaria
When should dogs be placed on monthly heartworm preventive medication?
- drugs approved with 1 month “reach back” activity:
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Start: - Within one month after earliest start date of transmission season
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Finish: - Within 1 month following end date of transmission season
(all except Interceptor Plus, NexGard SPECTRA,
and Credelio PLUS)
<> - 6 months following end date of transmission season (Interceptor Plus and NexGard SPECTRA)
- 2 months following end date of transmission season (Credelio PLUS)
Heartworm prevention in Canada using a monthly preventive
- what is the season? when do we give drugs?
- transmission starts at beginning of June
- ends sometime in October
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> first dose should be July 1 for HW, many people give on June 1 > (remember on-label all products have 4 weeks reachback activity. Off label activity is 8 weeks reachback)
> last dose should be Nov 1
when is year-round heartworm prevention reccomended
Note: If transmission > 6 months, year-round prevention is recommended
If a puppy is born in July in an area of Ontario where heartworm risk is a concern, by what age should it receive its first preventive treatment for heartworm ?
- 8 weeks of age, assuming they can get infected on day one of life
- In the southern US, then monthly for life
What is the minimum age that a dog should be tested for heartworm antigen ?
- 7 months > need adult parasites present
How often should dogs be tested for heartworm ?
- first time seen (if > 7 months old) – establish baseline data
- thereafter ?
> on-label use of heartworm preventives requires annual testing
> testing less frequently than once a year = off label:
=> acceptable if evidence to justify (i.e. low risk); requires informed consent - annual testing recommended for all dogs in the USA
Heartworm risk assessment to determine if test required
(applicable in low risk areas)
- If > 7 months old, has baseline status been determined ?
- Were heartworm preventives used in previous year ?
- Compliance in previous year ?
> doses missed ?
> vomiting of pill, difficulty applying spot-on ? - Travel history in previous year ?
> If so, to where ? Risk of heartworm infection ?
What if dog tests antigen positive for heartworm?
a) Repeat antigen test with different blood sample
> Also request microfilaria test:
> use concentration method (Knott’s, Difil method)
b) Is dog genuinely infected ?
> If Ontario risk, additional information is required
