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The prevention of pulmonary infections is essential for patients with CF, as every case of pneumonia bears the risk of a consistent decrease of their respiratory and health status. Beside the risk of pathogens, every pulmonary obstruction triggered by dust or allergens must be avoided. For example, Aspergillus spp. can elicit an allergic bronchopulmonary aspergillosis in patients with CF. Since the regular contact with animals is generally associated with an increased exposure to pathogens, dust and allergens, many doctors who treat patients with CF advise against having pets. Since up to this date, there exist no guidelines concerning ”CF patients and animal contact“, which are based on specific studies with CF patients, the present study provides a first step in the acquisition of relevant data. The aim was to assess the risk associated with pet animals for CF patients both quantitatively and qualitatively.
The working hypothesis guiding this study has been formulated as follows: Pet ownership and frequent contact to pets in general result in an increased health risk for patients with CF.
First, the intensity and extent of pet contact and the related hygienic behavior of patients from the Christiane Herzog-Zentrum Berlin were investigated. In this part of the project, 290 Patients of the Christiane Herzog-Zentrum volunteered to fill out a questionnaire and the provided answers were evaluated. For further analyses the group of patients with CF was divided in two groups. The group with regular pet contact (n=75) consisted of patients who all had currently ten hours or more in a week contact to at least one pet. Patients with less or no regular pet contact accounted for the cohort without regular contact (n=97). The analysis of the questionnaires revealed that CF patients, despite their condition, are not less likely to own pets than the German average. CF patients do prefer dogs and cats over other pets though, more so than German pet owners without CF. The hygienic behaviour in the context of animal contact of patients with CF was not particularly pronounced. It is remarkable however, that 90% of CF patients with pets attribute a positive emotional impact to their animals. In the second part of the study the health status of both cohorts was compared. Therefore clinical data, such as the forced expiratory volume in one second (FEV1), Body Mass Index (BMI), rates in exacerbation and hospitalization, as well as microbiological data (qualitative and quantitative detection of pathogens in sputum samples taken during the study period) were retrospectively compared across cohorts. In order to perform a high-quality statistical analysis, data reductions were necessary. After the exclusion of 19 patients (lung-transplant patients, patients with missing data), 56 patients with regular animal contact and 58 patients without regular animal contact were finally accepted into the statistical analysis.
Results of the statistical analysis provide no evidence that CF patients with regular animal contact suffer more infections than CF patients without regular animal contact. FEV1, BMI, rates in exacerbation and hospitalization did not significantly differ across cohorts. However, regular animal contact was a predictor for allergic bronchopulmonary aspergillosis (ABPA). CF patients with regular animal contact were 7 times more likely to develop an ABPA in comparison to CF patients without regular animal contact.
The third part of the study focused on the detection of bacteria and fungi that are associated with pets and their environment, in order to look for pathogenity and possible transmissions. For that purpose, a subsection of patients with pets were visited at their homes and pets and the home environment were examined in situ. 364 samples were analysed for clinically relevant bacteria and fungi by cultivation, microscopic examination and if necessary by DNA-sequencing and the MALDI-TOF method for bacterial analysis. This part of the project revealed multiple pathogens in patients and their pets, for which, considering the patient-pet-history, a transmission has to be considered likely. The mycological analysis showed that the keeping of pets on organic litter such as hey, straw, wood shavings or bark mulch result in an increased exposure to moulds, in particular Aspergillus spp.. This documented increase in pathogen prevalence does however not coincide with an increase in infections. The initial suspicion concerning the increased prevalence of potentially problematic pathogens from reptiles should be investigated in future research. The present study with only 4 relevant cases cannot provide conclusive evidence.
The results of the present study support the working hypothesis concerning the development of an ABPA, but not concerning all other aspects (risk of infection, lung function, nutritional status, hospitalizations and exacerbations).