A high prevalence of allergy to Tetranychus urticae was found.

No differences were found between patients allergic and non allergic to Tetranychus urticae regarding atopy, allergic disease, housing

type, region type, distance to farming fields or farming activities.

Future studies with a larger number of patients are needed to evaluate the relation of sensitization with clinical symptoms and the impact

of environmental factors.

Prevalence and clinical relevance

Introduction Methods

Results

Conclusions

Natacha Santos, José Luís Plácido

Immunoallergology Department, Centro Hospitalar São João, EPE, Porto, Portugal

Tetranychus urticae (Tet u) is a phytophagus mite that has been

associated with rhinitis, asthma, contact dermatitis and urticaria

symptoms, especially in farm and greenhouse workers.

Aims

• Determine the frequency of sensitization to Tetranychus urticae in a

population, irrespective of occupational exposure

• Assess clinical relevance with conjunctival provocation test (CPT)

• Evaluate possible environmental risk factors for Tet u allergy

Navarro AM, Delgado J, Sanchez MC, Orta JC, Martínez A, Palacios R, Martínez J, Conde J.; Prevalence of sensitization to Tetranychus urticae in greenhouse workers; Clin Exp Allergy. 2000 Jun;30(6):863-6.

Jee YK, Park HS, Kim HY, Park JS, Lee KY, Kim KY, Kim YK, Cho SH, Min KU, Kim YY. Two-spotted spider mite (Tetranychus urticae): an important allergen in asthmatic non-farmers symtomatic in summer and fall months. Ann Allergy Asthma Immunol. 2000 May;84(5):543-8.

Consecutive population of patients ≥6 years old followed in the Allergy Department of

a Tertiary Hospital in Portugal and referred by their allergist to be skin prick tested to a

panel of airborne allergens

Percentage of patients with positive skin prick tests to the six more common sensitizers

Der p Der f Lep d Tyr p Tet u Grasses

62.8% 54.6% 50.5% 40.8% 38.3% 36.7%

Skin Prick Tests (n=196)

(January to March 2010) Skin prick test negative (n=121)

Children (n=12)

12 controls not allergic to Tet u (health care

workers)

Conjunctival Provocation Tests

and Questionnaires (n=24)

(July 2012)

Skin Prick Tests:

House dust mites,

Animal dander

Pollen

Fungus

Tetranychus urticae

Saline (negative control)

Histamine 10mg/mL (n=12)

Conjuntival Provocation Tests:

• Single-blinded placebo-controlled

• Increasing concentrations of Tet u

(0.002-0.02-0.2-2mg/mL)

• Positive: conjunctival hyperemia,

palpebral edema or

lacrimation

(10 min)

Unreachable / telephone not attributed (n=9)

Unable to commute to hospital (n=21)

Under immunotherapy (n=17)

Pregnancy or breast feeding (n=2)

Ocular disease or CPT contra-indications (n=2)

Telephone invitation

Questionnaire:

• Demographic data

• Environmental exposure: housing type

region, distance to farming fields or

greenhouses and farming activities

• Allergy symptoms/diagnosis

Positive:

≥ 3 mm

Statistical analysis was performed with SPSS 18.0 (p>0.05)

Aproved by the Ethical Committe

Atopic = 163 (83.2%)

Sensitized to Tet u = 75 (46.0% of atopic)

47 (62.7%) female

mean age 29.2±4.7 years

60 (80.0%) sensitized to other mites

8 (4.1%) monossensitized to Tet u

Acari

Sarcoptiformes Astigmata

Pyroglyphidae Dermatophagoides

Glycyphagidea Lepidoglyphus

Acaridae

Acarus

Tyrophagus

Trombidiformes Prostigmata Tetranychidae Tetranychus

Conjunctival Provocation Test dose (mg/mL)

Slin

Pri

ck T

est

(mm

)

Conjunctival Provocation Test

Positive (n=9)

Negative (n=15)

p (<0.05) §

Atopy 6 8 0.678

Allergic symptoms 9 12 0.266

Rhinits 7 8 0.389

Asthma 2 4 1.000

Cutaneous 2 4 1.000

Apartment / Dwelling house 3 / 6 10 / 5 0.206

Rural / Urban 6 / 3 5 / 9 0.214

Farming activity 3 7 0.678

>40 / <20 hours per week 0 / 3 1 / 6 1.000

Pesticide use 2 4 1.000

Distance to farming fields <200m / >1Km 5 / 2 6 / 6 0.590

Skin Prick Tests to Tet u

Positive

(n=12)

Negative

(n=12) p (<0.05) §

Age, mean (SD) 28.8 (9.9) 36.8 (10.8) 0.071

Gender, female 10 10 1.000

Sensitized to other mites 9 2 0.012*

Allergy symptoms 12 9

Rhinitis 9 6 0.400

Asthma 3 3 1.000

Cutaneous 3 3 1.000

AUC = 0.952. Spearman correlation coeficient = - 0,112, p = 0,774

For wheal size ≥ 3 mm: sensitivity = 100%, specificity = 80%

positive likelihood ratio=5, negative likelihood ratio=0

False positives – co-sensitized to other mites

7 patients with respiratory symptoms (1 monossensitized), 5 referred an

exacerbation of symptoms in the vicinities of farming fields

2 patients monossensitized to Tetranychus urticae reported isolated

cutaneous symptoms (urticaria) in the spring, which was not related to

either exposure or removal from farming fields or greenhouses

Mean wheal size 4.4±1.5mm

§ Fisher test

In relation to this presentation, I declare that there are no conflicts of interest.