Santos N, Plácido JL. Sensitization to Tetranychus urticae: prevalence and clinical relevance. Allergy 2013;68(Suppl.97):463.

1.  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)
SlinPrickTest(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.