Microsoft word - notes dermclub 3-22 april 2009- how i treat flea allergy in 2009 _recovered_.docx

Dermclub 3:
How I Treat Flea Allergy in 2009
Dr Amanda Burrows

A. Introduction

1. Flea allergy dermatitis (FAD) is one of the most common skin diseases
of dogs and cats worldwide, where fleas are endemic. Ctenocephalides felis felis is the species most commonly implicated.
2. Somewhat surprisingly, flea allergy dermatitis still is seen relatively
commonly in University dermatology clinics and dermatology specialty practice worldwide. This occurs despite modern advances in flea control plus the fact that most small animal clinicians are quite cognisant of flea allergy dermatitis and routinely manage dogs and cats with flea allergy dermatitis.
3. Self-referral by the owner (second opinion) or veterinary referral of
dogs and cats with flea allergy dermatitis occurs for multiple reasons.
4. Surprisingly, when you suspect flea allergy, your most important task
is convincing the owner that you are making the correct diagnosis. Reasons Flea Allergy Dermatitis is seen in
Dermatology Specialty Practice

1. Owner disbelief that flea allergy is the correct diagnosis.

2. Owner scepticism that flea allergy is the correct diagnosis based on

3. Veterinary practitioner scepticism that flea allergy is the correct
diagnosis based on perceived management failure or lack of visualization of fleas.
C. Owner Disbelief in the Diagnosis of FAD

1. Failures in the management of flea allergy dermatitis correlate
strongly with owner disbelief that fleas are the underlying problem….”my veterinarian believes that the problem is due to fleas but I know that it is not!”
Dermclub 3 – How I Treat Flea Allergy in 2009 – Amanda Burrows
2. Reasons for disbelief
• Cultural biases against having ectoparasites…“it is not acceptable for me to have ectoparasites!.therefore it is not acceptable for my dog • “How can fleas cause this much trouble?”
D. Owner or Veterinary Scepticism Based on Past
Management Failure

1. Owner……“I am already doing everything that I can to kill fleas!”

2. Veterinarian……we are already using the latest “wonder drugs”.

E. What is Flea Allergy Dermatitis?

1. FAD is induced by the injection of antigenic material from the salivary
glands of fleas into an allergic host. Initial reactions to flea bites may be seen in all animals, however sustained reactions are only observed in allergic dogs and cats.
2. The pathogenesis of FAD is complex. A major factor in the
development of FAD is, naturally enough, exposure to fleas. In the dog, the age of first exposure, the scheme of exposure and underlying other diseases such as atopic dermatitis (AD) are also factors that influence the development of FAD. Early exposure to fleas may be protective against the later development of FAD. Intermittent exposure to fleas favours the development of FAD whereas continuous, chronic exposure may retard the development of FAD and decrease its severity, suggesting that continuous exposure may result in partial or complete tolerance. AD may be a predisposing factor raising the possibility of genetic predisposition to FAD, as FAD is seen more frequently in dogs with AD. Cross reactivity between flea antigens and other insects may allow atopic individuals to be sensitised to fleas indirectly by exposure to antigens from other insects, including ants and house dust mites.
3. In the cat there appears to be no difference in the rate of development
of clinical FAD between cats with continuous exposure to fleas and
4. In summary, all dogs and cats living in an environment with flea
infestation are at risk. Dogs with atopic dermatitis and/or where Dermclub 3 – How I Treat Flea Allergy in 2009 – Amanda Burrows infrequent use of adulticides encourages intermittent flea exposure are most at risk of developing FAD. In cats, inadequate flea control permitting either intermittent or continuous flea exposure increases
5. Formerly, FAD was viewed as an ‘all-or-none phenomenon’. Adult fleas
begin feeding (injecting antigen) almost immediately after finding a host. Studies have shown that most fleas feed within 5 minutes on the host before most modern products kill fleas. Therefore, effective modern products must diminish rather than prevent flea feeding. Flea allergy is now recognized as another dose dependent hypersensitivity contingent on the antigen dosage injected. The severity of FAD is dependent on allergy severity, number of fleas feeding, and amount of antigen injected.
F. Clinical Features of FAD

1. The flea bite induces a wheal or a papule which may develop an
appreciable surrounding area of erythema that persists for up to 48 to
72 hours. It may develop a small crust, but spreading lesions do not
occur. Crusts may develop on the surface of the papules.
2. Crusted papules in the umbilical fold, especially in male dogs is an
under-appreciated clinical marker for flea allergy dermatitis.
3. Lesions have a partially bilaterally symmetric pattern and are
classically confined to the dorsal lumbosacral area, caudomedial
thighs, ventral abdomen and flanks.

4. Chronic pruritus may lead to alopecia, lichenification, crusting,
and hyperpigmentation. Pyotraumatic dermatitis, secondary
bacterial pyoderma and secondary dry or greasy scaling and
odour are common in chronic cases.

5. Fibropruritic nodules are a highly characteristic clinical marker of flea
allergy dermatitis in susceptible dogs and are usually present in the
1. Papulocrustous eruptions are common; alopecia, excoriations,
crusting and scaling may also be found. Pigment changes may
occur and multifocal, small, melanotic macules are evidence of
previous inflammatory sites.

2. Lesions are typically confined to the dorsal lumbosacral region,
caudomedial thighs, ventral abdomen, flanks and neck but
lesions may become generalised.
Dermclub 3 – How I Treat Flea Allergy in 2009 – Amanda Burrows
3. FAD cats may also present with self-induced symmetric alopecia
and eosinophilic granuloma complex lesions.

4. Moderate to marked peripheral lymphadenopathy.

G. Diagnosis of FAD

1. The diagnosis is based on a combination of a consistent history,
suggestive clinical signs and positive response to flea control. In addition to the clinical diagnosis, diagnostic tests have been developed to help the clinician
2. Flea comb for 5 minutes and evaluate detritus collected for flea
excreta, eggs and fleas. Place debris on a white background, eg gauze swab and moisten the flea excreta with water. Blood will leach from flea faeces resulting in a characteristic red-brown staining of the gauze swab. A negative result on flea combing for fleas or flea excreta does
3. Gently express a papule to extrude the contents; directly apply a
microscope slide to the exudate, make a thin film and then air dry. Stain with Diff Quik and rinse the back of the slide with water and dry. If expression of a papule does not produce any material then use the back (blunt) surface of a #23 scalpel blade; scrape the top of the papule firmly and smear the contents collected along the edge of the scalpel. Determine the predominant inflammatory cell type and the number and type of bacteria (cocci, rods) and/or yeast (Malassezia) with oil immersion lens (1000X). In FAD, early lesions show a predominance of eosinophils (occasionally basophils) but more
chronic lesions are neutrophilic. An eosinophilic papule without
bacteria is strongly suggestive of FAD.

4. In many cases of FAD the history, physical examination and cytologic
findings will result in a strong clinical suspicion of a diagnosis of FAD.
Confirmation of the diagnosis is made by resolution of the
symptoms with eradication of the fleas. The time taken for clinical
improvement depends on the severity and chronicity of the disease,
the degree of hypersensitivity and the magnitude of the flea challenge.
As a general rule the response (or lack thereof) of a therapeutic trial is assessed at Day 28. Therapeutic trials may be conducted using the
following products and application frequencies as outlined below

Dogs: Fipronil spray q 14 days and then switch to Fipronil and S-
methoprene or Imidacloprid plus Permethrin spot-on applied every
7 to 14 days for 30 days plus Nitenpyram 1mg/kg PO daily for 30 days
Cats: Selamectin, Fipronil and S-methoprene or Imidacloprid spot-on
applied every 7 or 14 days for 30 days plus Nitenpyram 1mg/kg PO q 48
hrs if the cat is amenable to oral dosing.
Dermclub 3 – How I Treat Flea Allergy in 2009 – Amanda Burrows 5. Interpretation of the Therapeutic Trial

• A good response (>80%) is consistent with FAD
• A moderate response (30 to 80%) warrants continuing for a further 14 • If there is no further response (still 30 to 80% at Day 42) there may be concurrent disease eg FAD and atopy or an adverse food reaction • A poor response (< 30%) suggests FAD is unlikely
H. Treatment: Let’s start with an Understanding of
Flea Biology

Flea Biology Fact 1
• A newly emerged flea starts feeding within 23 seconds after arrival on
the host: the first blood meal lasts from 10 minutes (males) to 25 minutes (females) and mating occurs in the first 24 hours. • It is easy to understand, therefore that none of the available products • Some of them (Nitenpyram and Selamectin) reduce the flea blood consumption and therefore decrease the amount of injected saliva.
Flea Biology Fact 2
• Female fleas start laying eggs after 24hrs.
• After feeding for 48 hours, the flea is metabolically dependent on a
constant source of blood and removal after this time results in rapid death (2 to 4 days). • Thus the flea is a permanent ectoparasite. • It does not freely transfer from one animal to another and the majority of fleas are removed by grooming and ingested.
Flea Biology Fact 3
• Flea eggs are 0.5 mm diameter, white, smooth and shed off the coat
• The eggs will hatch in 1 to 10 days depending on the relative humidity (RH) and temperature of the microclimate. • They are extremely sensitive to desiccation, and humidity less than
Flea Biology Fact 4
• Newly hatched larvae are mobile, free living and feed on organic
• Larvae are negatively phototactic (move away from light), positively geotactic and hygrotactic and move deep into the carpet pile or under organic debris moving the larvae to a stable microclimate and closer to food. • In the house, they will migrate away from major traffic areas and large numbers will be found under furniture, near where the animal sleeps. Dermclub 3 – How I Treat Flea Allergy in 2009 – Amanda Burrows
Flea Biology Fact 5
• The larva moults over 5 to 11 days depending on food availability,
temperature and humidity before developing into a pupa. • If the there is a decline in RH below 50% or high temperatures, larvae • Given these factors, larval development outdoors is most likely to occur in shaded, moist spots where the animal rests; indoors the larvae require a sheltered microclimate; usually afforded by carpet pile or bedding.
Flea Biology Fact 6
• Once the larvae have completed their development, they spin a loose,
sticky, silk cocoon that may offer some protection to the developing pupae from environmental sprays. • It is the location of the pupae, however, deep in carpet pile, under organic debris that protects the cocoon; the sprays are physically not
Flea Biology Fact 7
• Adult fleas begin to emerge within 5 days with peak emergence in 8 to
• Temperature, physical pressure, changes in light intensity and exhaled carbon dioxide from a passing host are the stimulants to emergence. • The survival of the emerged (prefed) off host adult is dependent on humidity and temperature; the higher the temperature and lower the • Depending on environmental conditions the life cycle can be complete
I. Modern Flea Control Products
Imidacloprid spot on preparation (Advantage®, Bayer; Advocate®
Bayer, Imidacloprid and moxidectin)

• Advantages: larvicidal on the animal and kills/ debilitates adult fleas
• Disadvantages: does not have repellent action, diminished efficacy after bathing or swimming, does not have activity against ticks, • Bottom-line: good narrow-spectrum product for fleas.

Fipronil & S-methoprene spot on and spray (Frontline® Plus, Merial),
Fipronil (Frontline® Spray, Merial)

•
Advantages: kills adult fleas, disrupts flea life cycle, ease of application, kills ticks, spray - rapid dispersion and coverage. Dermclub 3 – How I Treat Flea Allergy in 2009 – Amanda Burrows • Disadvantages: does not have repellent action, diminished efficacy after bathing or swimming, occasional application site reactions, spray is more effective but labour-intensive.
• Bottom-line: good broader spectrum product

Imidacloprid & 44% Permethrin spot on preparation (Advantix®,
• Advantages: larvicidal on the animal, kills or debilitates adult fleas on contact, interrupts flea life cycle, repellent ‘flushing’ permethrin, ease of application, also kills ticks and mosquitoes. • Disadvantages: dog only product, diminished efficacy after bathing/swimming, occasional application site reactions. • Bottom-line: good broader spectrum product, dog only
Selamectin spot on preparation (Revolution®, Pfizer)
• Advantages: broad spectrum against many parasites, kills adult fleas plus larvae and eggs, rapid flea kill in cats, kills ticks, kills mites (Sarcoptes, Notoedres, Cheyletiella, Otodectes), ease of application, • Disadvantages: no repellent action, diminished efficacy after bathing or swimming, slower efficacy on dogs? application site reactions.
• Bottom-line: good broader spectrum product.
Nitenpyram oral tablet (Capstar™, Novartis)
• Advantages: rapid response with visual results, kills all adult fleas within 4 hours, short-acting, oral administration, give every 24-72 hours (half-life in dogs is 2.8 hours, half-life in cats is 7.7 hours), very safe. • Disadvantages: no repellent action, does not disrupt flea life cycle, short-acting, does not have activity against ticks, expensive when used frequently. • Bottom-line: good narrow spectrum product, use with spot-ons initially for rapid response, use in dogs requiring frequent shampooing or that swim, adverse reactions not seen yet Dermclub 3 – How I Treat Flea Allergy in 2009 – Amanda Burrows Lufenuron oral tablet (Program®, Novartis; Sentinel Spectrum®
Novartis (Lufenuron, milbemycin oxime and praziquantel)

• Advantages: oral product, very safe, adverse reactions not seen.
• Disadvantages: does not kill adult fleas or pupa, time lag 60-90 days to disrupt flea life cycle, no repellent action, no activity against ticks, give with food. • Bottom-line: use with spot-ons or newer oral products, not for use as sole therapy unless closed environment, treat all animals, use in dogs requiring frequent shampooing or that swim.

Spinosad oral chewable tablet (Comfortis®, Lilly). New oral monthly
• Advantages: rapid response for a systemic once monthly product, kills adult fleas before egg laying initiated, efficacy not affected by bathing or swimming. • Disadvantages: no perceived disadvantages yet.
• Bottom-line: awaiting judgment, exciting potential!
Metaflumizone spot on preparation (ProMerisTM for cats, Fort Dodge).
Advantages: kills/debilitates adult fleas on contact, ease of • Disadvantages: no repellent action, assume diminished efficacy after bathing or swimming, no activity against ticks, occasional application site reactions?
• Bottom-line: awaiting judgment.
Metaflumizone & metaflumizone & amitraz spot on preparation
(ProMerisTM for dogs, Fort Dodge). New product. Advantages: kills/debilitates adult fleas on contact, ease of application, stops egg production ?efficacy against ticks. • Disadvantages: separate dog & cat products, no repellent action, diminished efficacy after bathing or swimming? occasional application • Bottom-line: new product awaiting judgment Dermclub 3 – How I Treat Flea Allergy in 2009 – Amanda Burrows J. In summary
1. Historically, flea control has required treating both the animal and the
environment. Today, more rapid acting and more effective topical and systemic anti-flea therapy may be the only management required. The initial agents that created this paradigm shift include Imidacloprid, Fipronil, Selamectin, Nitenpyram, Lufenuron, S-methoprene, and
pyriproxifen. Despite relatively rapid flea kill and industry claims,
none of these products prevent fleas from feeding before they
are killed. However, these products reduce an animal’s flea burden
enough to diminish clinical signs of FAD. New oral product containing
spinosad and topical product containing metaflumizone may substantially add to that armamentarium.
2. Most of these products are very effective adulticides or have ovicidal
and larvicidal activity or both. None of them has any repellent activity or kills mosquitoes except for those containing permethrin. The disadvantage of products containing Permethrin is that they cannot be used in cats.
3. Our strong clinical impression is that dogs and cats with flea allergy
experience better efficacy when these products are applied every 3
weeks instead of once a month.

4. Our strong clinical impression also is that either bathing or swimming
degrades the efficacy of all the spot-on topical products. In
circumstances where animals are swimming frequently or being
bathed regularly we are recommending bimonthly or weekly application of spot on products or the use of oral product.
L. What flea control do we recommend?

1. We recommend different combinations of insecticides depending on
the situation. Total flea eradication may not be necessary in non-allergic dogs but is the ultimate goal in all dogs and cats with FAD. This requires both eliminating adult fleas and preventing their
2. Client education is crucial. All dogs and cats in the environment must
be treated. Flea control must be personalized and regionalised based on severity of possible infestation in your geographic region, number of dogs and cats in the environment, indoor/outdoor/run free status, infested pests and strays in the environment, finances of the owner, and severity of disease vs. magnitude of the infestation.
a. Puppies and kittens: in young puppies and kittens (< 4 weeks)
mechanical removal using a flea comb permits removal of adult fleas until the animals are old enough for the direct application of insecticide. Fipronil and S-methoprene spot-on preparations are Dermclub 3 – How I Treat Flea Allergy in 2009 – Amanda Burrows licensed for dogs and cats older than 8 weeks of age and the Fipronil spray preparation is registered for application in puppies and kittens after 48 hours of age. Imidacloprid spot-on is safe to use on puppies and kittens after weaning. Selamectin can be used in dogs and cats b. The Non Allergic Pet
i. Indoor dogs or cats with limited flea exposure: Lufenuron; only
be effective in a closed environment; will not be acceptable for those clients who never wish to see fleas on their pet. The average dog: Fipronil and S-methoprene, Imidacloprid,
iii. The average cat: Selamectin, Fipronil and S-methoprene or
iv. Dogs that swim or are bathed regularly: Nitenpyram every 1 to 2
c. Allergic Pets: initial management
Dogs: Fipronil spray q 14 days and then switch to Fipronil and S-
methoprene or Imidacloprid plus Permethrin spot-on applied every 7 to 14 days for 30 days plus Nitenpyram 1mg/kg PO daily for 30 days ; spinosad
only?
Cats: our choice would be Selamectin, Fipronil and S-methoprene or
Imidacloprid spot-on applied every 7 or 14 days for 30 days plus Nitenpyram 1mg/kg PO q 48 hrs if the cat is amenable to oral dosing. d. Allergic Pets: maintenance
Dogs: Fipronil and S-methoprene or Imidacloprid plus Permethrin spot-on
applied every 3 weeks with oral or injectable Lufenuron for all in-contact
pets. In dogs with severe FAD that are not controlled with this regime, re-evaluate the patient to identify a breakdown point in flea control e.g visiting a contaminated environment or regular swimming or bathing and
administer intermittent Nitenpyram in conjunction with above
Cats: Selamectin, Fipronil and S-methoprene or Imidacloprid spot-on
applied every 3 weeks with oral or injectable Lufenuron for all in contact
pets.
e. Mobile Pets
When an animal with FAD leaves a controlled environment then, there is
always the possibility of a flea challenge. Repellents are useful in this
situation. For dogs, Permethrin spray is ideal; an alternative is to use
Nitenpyram for due to its rapid killing effect in these situations. While
Permethrins cannot be used on cats, oral Nitenpyram is a valuable tool for cats visiting cat shows or given to both dogs and cats prior to visits to day care, kennels etc. Dermclub 3 – How I Treat Flea Allergy in 2009 – Amanda Burrows M. Reasons for Flea Allergy Dermatitis Treatment

1. Failure to treat all in-contact animals (The squeaky wheel gets the
oil.) In-and-out cats are a frequent cause of treatment failure in households with multiple animals. Consider regular animal visitors that are not receiving flea control.
2. Failure to maintain consistency in treatment

3. Failure to deal with environmental issues in severe cases

4. Substitution of prescription spot-ons with less expensive, but less
effective and less safe spot-on products from pet stores N. Troubleshooting for Clients with Flea Control
Problems

When fleas are found the infestation is often blamed on product failure or
resistance to the insecticide. Although the extent or prevalence of insecticide resistance has not been fully determined, it seems to be low based on the current evidence. With any breakdown of flea control, the following should be considered and discussed with the client. a. Application method
The two broad areas where breakdowns may occur are from frequency and method of application. Occasionally owner concerns about cumulative toxicity may lead them to apply the insecticide at longer intervals than recommended leading to sub-therapeutic levels and poor efficacy. Numerous errors in application methods can also result in sub-therapeutic levels and poor efficacy. These include inadequate volume of application (particularly with sprays), but can also occur due to use of the wrong size of spot-on for the animal’s weight. The spot-on formulations have a range of specific application requirements that must be followed or breakdown can occur, including application to a wet coat, soon after bathing or swimming etc b. Are all the pets in the household being treated?
The cat flea will happily infect a wide range of hosts. Failure to treat all hosts in the household will lead to poor flea control through continued contamination of the environment from the untreated host. Dermclub 3 – How I Treat Flea Allergy in 2009 – Amanda Burrows c. The pupal window (re-emergence)
Not all existing pupae will emerge at the same time (remember that pupae can remain dormant for up to 140 days) and some spontaneously emerge throughout this time and others due to specific stimuli. The pupae are often in protected microenvironments, out of reach of environmental insecticides. Depending on the climatic conditions this may give the appearance of a “re-emergence” of infestation while animals are already on therapy and the environment has already been treated. d. Washing and swimming
The effect of shampooing is controversial. It is hard to compare product versus product as studies between companies often have differences in reporting (eg. fleas found per animal versus total flea numbers found), lack of uniformity in shampoos used and that not all other variables (concurrent pyoderma, keratinisation defects etc) can be allowed for. It is wise to presume that intensive shampooing eg. once to twice weekly and frequent (daily) swimming will reduce the duration of activity of topically applied flea control products. e. Secondary larval breeding sites (other pets and feral
animals, other locations for breeding)
The potential for external flea breeding sites should be considered. Environmental treatment should be focused on areas that can support larval survival (garden areas protected from desiccation) where potential
carriers of fleas (other pets, neighbour’s cats) spend their time.
f. Hitchhiker fleas

Transfer of adult fleas from one host to another, although possible can
occur, it is unlikely that this would be a cause for breakdown of flea
control. Visitations to an area of heavy flea burden can however result in
temporary breakdown in control.
Conclusion:
New infestations come from the environment. An educated client armed
with an integrated approach to flea control can rapidly and profoundly affect flea numbers and reproduction and achieve effective flea control. Dermclub 3 – How I Treat Flea Allergy in 2009 – Amanda Burrows
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