Allergenic Extract - Flea Antigen

Company: Stallergenes-Greer

U.S. Vet. Lic. No.: 294

Active Ingredient(s): FLEA ANTIGEN is an aqueous extract of the whole bodies of Ctenocephalides spp. with phenol added as a preservative.

Allergenic Extract - Flea Antigen Indications

1. Diagnostic: FLEA ANTIGEN is a valuable aid in the diagnosis of flea bite allergy. Compatible clinical signs and documented exposure to fleas are also necessary to establish the diagnosis.

2. Therapeutic: FLEA ANTIGEN EXTRACT is indicated as an aid in alleviating the symptoms associated with flea bite allergy. A program of controlling the flea population by breaking the life cycle and minimizing flea infestation on the animal should be initiated before or concurrent with hyposensitization treatment. Concomitant antibiotic therapy and an appropriate bathing program should be given where significant secondary bacterial infection is evident. Short-term corticosteroid therapy may be used as an adjunct in the early stages of therapy.

The exact mechanism by which flea antigen elicits an allergic response is still under investigation. It has been demonstrated however, that successful hyposensitization treatment decreases specific IgE antibody levels, theoretically by increasing the level of blocking IgG antibodies. These blocking IgG antibodies are believed to complex with the circulating antigen before it can reach the IgE present on the skin and trigger the allergic response.

Test Procedure: Skin Testing:

1. Materials Needed:

a. Sterile 1 mL tuberculin type syringes with 25- to 26-gauge needles, 3/8 to 1/2 inch in length.

b. FLEA ANTIGEN at 1:1,000 w/v (final concentration).

c. Diluent control (negative control).

d. 1:100,000 w/v histamine phosphate (positive control).

2. Suggested Procedure:

a. Prepare the test area by clipping and cleansing the testing site (lateral thorax or inguinal area).

b. Five (5) minutes prior to the test, the site may be flooded with alcohol which is allowed to dry by evaporation.

c. Using a separate syringe for each solution, load the 1 mL tuberculin syringe with 0.1 mL of control solution or flea extract.

d. Ensure that all air bubbles have been expelled from the loaded syringe, because the injection of air bubbles may force dermal cells apart and create false reactions.

e. The injection sites should be at least 2.5 cm from each other and the injections should be atraumatic.

f. After gently stretching the skin around the test site, the needle is inserted into the skin at an angle of approximately 10° with the bevel upwards.

g. Stop inserting the needle when the entire bevel is buried in the skin (ideally the bevel should be visible through the superficial layers of the skin).

h. Inject 0.05 mL of the control solution of flea extract and gently remove the needle to prevent traumatic hemorrhage.

i. Retain the remaining 0.05 mL of control solution or flea extract in case the wheal is unsatisfactory due to the movement of the patient or poor injection technique.

j. The skin test should be completed as soon as possible to allow simultaneous comparison of the flea antigen wheal against the controls.

3. Interpretation:

a. Immediate (IgE mediated) reactivity will cause a wheal within 15 minutes.

b. A wheal that is five (5) or more millimeters greater than the negative control denotes a positive reaction. However, a strong positive is likely to be close to the histamine injection in size, and will be a minimum of 1 cm in diameter.

c. If the patient is negative at 15 minutes, re-examine after 24 hours to check for delayed reactions.

d. See Overdose procedure if adverse reactions occur.

Hyposensitization:

Discussion: The optimum dosage and route of administration of FLEA ANTIGEN has not been clearly established and currently many dosage schedules are in use.

Subcutaneous or intradermal injections have been administered with success,^6,7 but it has been noted that if at least part of each injection is intradermal the response seems improved.¹

A suggested treatment schedule is offered below, however; in the final analysis, the dosage and length of treatment will depend upon the sensitivity and responsiveness of the patient.

Treatment: The suggested hyposensitization dose is 0.1-0.5 mL of FLEA ANTIGEN at a 1:100 w/v per 25 lbs. of body weight. Treatments should be initiated with a 0.1 mL/25 lbs. dose and gradually increased to a maintenance dose of 0.5 mL/25 lbs. The treatment should continue for a 6- to 24-week period.

The injection is administered intradermally at a number of sites with a 1.0 mL sterile tuberculin syringe, using a 25- or 26-gauge needle 3/8 to 1/2 inch in length. Intradermal injections should not exceed 0.2 mL per site or adverse reactions may occur.

Suggested Dosage Schedule:

Boosters can be given if symptoms re-occur or as a prophylactic measure before flea season. The booster dose should not exceed the last dose given.

Contraindication(s):

1. Diagnostic: Corticosteroids will inhibit the histamine mediated immediate skin test. Any patient that has undergone continual corticosteroid treatment should discontinue the treatment for a period of one week for every month of the treatment before the patient is skin tested. However, animals with severe skin problems should be treated with antibiotics, soothing baths and possibly a short-term oral cortisone until their skin conditions will not interfere with skin testing.

2. Therapeutic: FLEA ANTIGEN is indicated for hyposensitization only when flea bite hypersensitivity has been unequivocally demonstrated both clinically and by intradermal skin testing.

Caution(s): Have in stock the following:

1. A hydrocortisone (such as Solu-Cortef^® or a prednisolone (such as Solu-Delta-Cortef^®).

2. An antihistamine such as diphenhydramine hydrochloride (Benadryl^®).

3. Epinephrine diluted 1:1,000.

Keep the patient under observation for a period of at least 30 minutes after administration.

Note: Animals prone to severe reactions should be given diphenhydramine hydrochloride (Benadryl^®) 30 minutes prior to treatment dose administration.

Overdose: If symptoms of overdosage occur (see Side Effects section below), treatment employing (a), (b) or (c) below, or a combination thereof can be effective in combating an adverse reaction.

a) Intravenous injection of hydrocortisone (i.e. Solu-Cortef^®) in a dosage of 10-15 mg/lb., or alternatively, a prednisolone (i.e. Solu-Delta-Cortef^®) in a dosage of 5 mg/lb.

b) Intramuscular or subcutaneous injection of epinephrine in a dosage of 0.5-1.0 mL at 1:1,000.

c) Intravenous injection of an antihistamine such as diphenhydramine hydrochloride (Benadryl^®) in a dosage of 0.5-1.0 mg/lb.

Note: In a crisis situation epinephrine may be administered intravenously. Use 0.5 to 1.0 mL of a 1:1,000 dilution.

Side Effects

Adverse reactions are very rarely seen and usually consist of an exacerbation of clinical signs if too large a dose is given. However, in the event of an overdose or alternatively, exquisite sensitivity of the animal, the patient may exhibit restlessness, panting, generalized hives, vomiting, circulatory collapse and diarrhea (see Overdose section above for treatment).

There are also several normal reactions that may occur and the owner should be advised of these prior to administration of the allergen. Temporary pain and discomfort may be experienced at the time of injection, with some stiffness and soreness occurring later. A small area of ulceration may occur where intradermal administration is employed.

References

Available upon request.

Presentation: FLEA ANTIGEN is supplied in sterile 10 mL vials at a concentration of 1:100 w/v (aqueous only).

CPN: 1110000.1