Low frequency of positive skin tests in asthmatic patients infected with Schistosoma mansoni exposed to high levels of mite allergens

Helminthic infections and allergic diseases are highly prevalent in many parts of the world. Although skin reactivity to indoor allergens is decreased in subjects from helminthic endemic areas, the degree of exposure to mite allergens has not yet been investigated in these areas. This study evaluated the association between exposure to dust mites and skin reactivity to mite allergens in subjects with a history of wheezing in the last 12 months selected from a rural endemic area for schistosomiasis (group I, n = 21), and two non-Schistosoma mansoni endemic locale, a rural area (group II, n = 21) and a urban slum area (group III, n = 21). All subjects were evaluated by skin prick tests with mite allergens, and for total and specific immunoglobulin E (IgE) against dust mites, antibodies for S. mansoni, and for intestinal parasites. Dust samples from each subjects' home were quantified for mite allergen and species of the mite identification. Except for S. mansoni infection which was more prevalent in group I than in groups II and III (p < 0.0001), the prevalence of intestinal parasites, and total and specific IgE levels were similar for all groups. Despite the levels of mite allergens and specifically to Der p 1 detected in dust samples of subjects home from all three areas, the frequency of positive skin reactivity to mite antigens was significantly lower (19.0%) in subjects from group I relative to group II (76.2%) and group III (57.1%; p < 0.001). This result suggests that S. mansoni infection could modulate the immediate hypersensitivity skin response to mite allergens in highly exposed subjects.

Mite allergen levels and acarologic analysis in house dust samples in Uberaba, Brazil

Mite allergen exposure has been widely related to sensitization and development of allergic diseases. This study intended to evaluate the degree of allergen exposure in Uberaba, Brazil, through the measurements of Der f 1 and Der p 1 allergen levels associated with the acarologic analysis in house dust samples. A total of 240 dust samples were collected from 60 houses through vacuuming sofas and bedding, during the months of March and July 2000. Indoor temperature and relative humidity were also measured. Mites were counted and identified under light microscopy and allergen levels were measured by two-site monoclonal antibody ELISAs. The major mite family was Pyroglyphidae (39.4%), having D. pteronyssinus as the most frequent species (15.6%), followed by D. farinae (12.3%) and E. maynei (7.9%). The family Glycyphagidae was less commonly found (4.8%), with Blomia tropicalis (4.4%) as its majoritary member. The highest levels of Der f 1 and Der p 1 allergens were found in bedding samples in March (31.7 and 0.9 microg/g of dust, respectively), with Der f 1 levels significantly higher than Der p 1 (p < 0.0001). There was a significant positive correlation between the mite number and allergen levels. These results indicate that Dermatophagoides sp are the most frequent mites in our region followed by E. maynei. Therefore, the knowledge of the local mite fauna would improve the means of investigating the association between allergen exposure and sensitization, allowing the addition of new mite extracts in diagnostic tests.

Association between mite allergen (Der p 1, Der f 1, Blo t 5) levels and microscopic identification of mites or skin prick test results in asthmatic subjects

BACKGROUND

Mite allergens have been involved in airway sensitization and allergic diseases. Immunoassays for the identification and quantifiction of house dust mite (HDM) allergens are useful to improve the knowledge of regional mite fauna and the remediation of mite allergens in allergic diseases. The present study analyzed the association between levels of HDM allergen and results of mite identification or skin prick test (SPT) in two different areas of Bahia, Brazil.

METHODS

Forty-two asthmatic subjects from a rural area (group I; n = 21) and a slum (group II; n = 21) were evaluated through SPT with HDM allergens and had dust samples collected at their homes for mite identification and allergen measurements.

RESULTS

Positive SPT to Dermatophagoides pteronyssinus, Dermatophagoides farinae and Blomia tropicalis allergens were observed in 42.9, 38.0 and 42.9% subjects from group I and in 47.6, 19.0 and 33.3% subjects from group II, respectively. D. pteronyssinus and B. tropicalis were identified in approximately 76 and 50% of samples from both groups, respectively. D. farinae was identified in 38.0 and 9.5% of samples from groups I and II, respectively (p < 0.005). Der p 1, Der f 1 and Blo t 5 detection were associated with mite identification (p < 0.05). Association between HDM allergen levels over 2 microg/g of dust and positive SPT occurred only with D. pteronyssinus (p < 0.0001).

CONCLUSIONS

D. pteronyssinus was the most prevalent mite species in this study followed by B. tropicalis and D. farinae. Immunoassays done to measure mite allergens were associated with mite-species identification. We conclude that these three mite species must be included on panels for the diagnosis of allergic airway diseases in subjects living in such regions.