frequently, but led to detection of higher percentages of seropositivity (23.7 -67.7 % and 35.9 -49 95.6 %, respectively). Attempts to grow C. psittaci in cell culture or embryonated chicken eggs 50 were successful in 2 -42.3 % and 0 -57.1 % of samples, respectively, antigen detection methods 51 were positive in 2.3 -40% of samples, while conventional PCR and real-time PCR using different 52

Feral pigeons (Columba livia, Gmelin 1789) cause different problems for building owners when using structures for daytime perching, sleeping, and breeding. Problems include fouling of building facades and pavements, transmission of allergens and pathogenic microorganisms, and infestations with ectoparasites emanating from breeding sites. Owners are primarily interested in keeping away unwanted pigeons from their property. Pest control companies offer different deterrent systems, of widely varying efficacy, for proofing buildings against feral pigeons. A better solution is avoiding attractive structures during building design or subsequent alterations of existing structures used by feral pigeons. With our study, we elaborate the relevant structural data to help to maintain a building free of pigeons. We performed experiments with free ranging feral pigeons in a feral pigeon loft in the City of Basel, Switzerland. The maximum outlet width a pigeon is not able to pass through is 4 cm; the respective outlet height is 5 cm and a pigeon-safe square opening is not larger than 6×6 cm. The maximum ledge width a pigeon is not able to sit on is 4 cm. The pigeon-safe angle of inclination for smooth construction materials (tinplate, glass, plastics) is 25°, for medium rough materials (wood, plane concrete) 35°, and for rough materials (sandstone, rough concrete) at least 50°. Additionally, we studied the behavioral strategies used by feral pigeons to surmount our experimental constructional restrictions, ledge width, and ledge inclinations. Our data provide the essential data to prevent feral pigeons from using building structures.

Feral pigeons (Columba livia) are commonly infected with Chlamydia psittaci, the agent of psittacosis in humans. To assess the risk of zoonosis posed by feral pigeons in the urban environment, we determined the prevalence of Chlamydia psittaci by detection of the outermembrane protein A (ompA) gene of this pathogen in pharyngeal and cloacal samples of 202 feral pigeons present in a loft in Basel, Switzerland. Additionally, we examined 620 fresh faecal droppings of feral pigeons at six public sites in Basel. The ompA gene of C. psittaci could be detected in only 17 (8.4 %) of the 202 feral pigeons in the loft. C. psittaci DNA was present in nine (2.0 %) of 447 of the pharyngeal swabs and 11 (3.2 %) of the 348 cloacal swabs. Genotyping of the ompA gene revealed genotype B in seven of the birds. In one bird, a mixed infection was detected with the genotypes A, B and E/B, which, to our knowledge is the first time such an infection has been reported. Some of these birds immigrated into the loft as adults. To our knowledge, this is the first study to document how the interconnectedness between feral pigeon subpopulations favours the spread of C. psittaci. C. psittaci DNA was not detected in any of the faecal droppings collected at the six public areas. In spite of the low levels of C. psittaci shedding by feral pigeons in Basel, close contact to feral pigeons bears the risk of zoonotic transmission of C. psittaci. Feral pigeon management programmes and public education should be implemented to reduce the risk of a pigeon-to-human transmission of such pathogenic agents.

Chlamydophila psittaci (Lillie, 1930) Everett et al., 1999, the pathogenic agent of human ornithosis, is widespread in feral pigeon populations and many cases of transmission from feral pigeons to humans have been reported. The aim of the present study was to detect C. psittaci in environmental samples to find out more about possible transmission routes and, therefore, to assess the zoonotic risk for humans. Fecal samples were collected from nest boxes in a feral pigeon loft. Additionally, samples were taken from the feather dust film covering the water surface of public fountains where pigeons regularly bathe. The samples were tested for the presence of chlamydial antigen using an antigen enzyme-linked immunosorbent assay to prove shedding of C. psittaci by feral pigeons. This test detects a genus specific lipopolysaccharide in the outer membrane of the chlamydial bacteria. Samples were tested using the IDEIA PCE Chlamydia Test kit (DakoCytomation) and positive results were verified with IDEIA Chlamydia Blocking Reagents (DakoCytomation). The IDEIA PCE Chlamydia Test yields a high proportion of positive results. However, when IDEIA Chlamydia Blocking was performed, most of the positive results turned out to be negative or could not be interpreted. We conclude that antigen-enzyme-linked immunosorbent assay tests are not suitable for detecting C. psittaci in environmental samples. Previous publications where no blocking test was used should be reconsidered critically.

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