Is the risk of developing atopic sensitization and bronchial asthma in animal laboratory workers preventable in well-defined susceptible individuals?

To the editor

We have read the excellent study conducted by Simoneti et al.[1)] with considerable interest, which shows that laboratory animal (LA) exposure was associated with atopic sensitization. With regard to this, we would like to disagree on the modalities to collect data on "pet ownership" and provide some suggestions on the possible "preventive aspects" of allergic sensitization to LA based on our clinical and scientific experiences.

It is indubitable that the presence of a persistent exposure to LA increases the amounts of allergens reaching the airways and, consequently, the risk of developing allergic sensitization and bronchial asthma. However, only this aspect should not be considered as the exclusive risk factor for the development of occupational asthma to LA.

The query on pet ownership "Are there animals at home?" is common and usually done when collecting anamnestic data. This prevalent modality to consider exposure to pet allergens could constitute a potential bias in epidemiological studies and in clinical practice for an objective evaluation of the clinical significance of the skin prick test (SPT) positivity to common pets (cat/dog)[2)]. Pet allergens should be considered as ubiquitous because they are found in indoor private or public places where cats/dogs have been never kept.

In a study involving 723 patients sensitized to cats/dogs, 49.92% of patients reported direct pet contact, but only 29.46% were pet owners (pets at home) while 20.19% were directly exposed to pets in other settings. The remaining individuals were sensitized because their previous pet ownership (20.75%) or because they were indirectly exposed to pet allergens though pet-contaminated items (e.g. clothes of pet owners). Only 15.35% of our patients reported no apparent direct or indirect contact with pets. Therefore, only 29.46% patients could be classified as "exposed to pets" and 70.54% as "not exposed" according to the usual query. Our classification has shown that a significant percentage of "not-exposed" patients (55.19%) are instead "really exposed" (Liccardi G. unpublished data). Moreover, using in vivo (SPT)[3)] and in vitro (micro-array technique immunoCAP ISAC)[4)] methods, we have shown that exposure and allergic sensitization to common pets greatly increase the risk of developing sensitization to other furry animals probably for the presence of cross-reacting allergens (e.g., albumins and lipocalins).

In other words, it is likely that a consistent number of patients in the study by Simoneti et al. were already sensitized to epithelial allergens through previously reported mechanisms before occupational exposure to LA.

Based on this background, the key question is "How can we estimate the risk of sensitization to LA in patients already sensitized to cats/dogs or in those exposed to furry animals who wish to come into contact with animals in laboratory settings?." We suggest a possible diagnostic flow-chart in Fig. 1.

Fig. 1.

Possible flow-chart to evaluate the risk of developing allergic sensitization to laboratory animals (LA) in susceptible individuals who wish to work in laboratory settings.

In conclusion, there is no doubt that a persistent exposure to LA can induce respiratory symptoms in sensitized patients. It is also important to underlie that allergic sensitization without direct animal exposure is a potential risk for patients because they are often unaware of this. The above-mentioned aspect should be considered by susceptible individuals before starting to contact with LA for working reasons. SPTs and/or evaluation of specific IgE to LA should also be highly recommended in these individuals to identify the occurrence of allergic sensitization and, consequently, to avoid (or control) future exposure. In this context, an evaluation of specific IgE using the micro-array technique [Component Resolved Diagnosis (CDR) ] for lipocalins (Can f 1, Can f 2, Equ c 1, Fel d 4, Mus m 1) and albumins (Bos d 6, Can f 3, Equ c 3, Fel d 2) may be quite useful to evaluate the possibility of cross-reactions between allergens of different animals[5)].

Conflict of interest and financial resources: All authors declare that they have no conflict of interest and that the study has been conducted without any financial support.