Monitoring and surveillance Management implications 1. Benchmarks

Public Health Significance of Urban Pests Birds 261 260 8.4. Management implications 8.4.1. Benchmarks In general, the benchmarks for urban bird management should take into consideration the following K. Sweeney, United States Environmental Protection Agency, personal communication, 2005: • identifying the real public health threat posed by urban birds, using monitoring and surveillance methods; • determining the level of threat that requires a response to protect the public; • deciding the type, intensity and timing of a response; • measuring the success of the response. This chapter has attempted to describe the recent state of knowledge of urban birds as a public health hazard. Some synanthropic avian species can obviously serve as hosts, reser- voirs, transporters or lessors of a few human pathogens. However, the extent and signi- ficance of this epidemiological hazard might vary enormously, and it should be measu- red according to local conditions in particular urban areas. It is therefore very difficult to propose and apply a set of general benchmarks for urban birds as a public health threat. In general, the evidence and estimation of the level of threat must be based on data on the incidence of bird-borne illnesses in particular urban settings, using standard epidemio- logical surveillance methods. The straightforward way of determining the epidemiolo- gical hazard is to first establish whether a human bird-borne infection does or does not occur at a particular urban setting. If it does, the second step is to establish how often it occurs incidence of the disease. The final step then involves a decision about the level such as one human case or more cases at which public funds should be spent on pre- ventive and control programmes and measures. At least several cases of human disease directly associated with urban birds or their habi- tats have been reported for ornithosis, histoplasmosis, campylobacterosis, salmonellosis, mycobacteriosis, cryptococcosis, toxoplasmosis and Q fever Table 8.1. However, com- pared with other communicable diseases, in general, their annual incidence is quite low, but underreporting should be taken into account. Also, although no cases acquired directly from birds have been described for a number of other infectious diseases mostly arthropod-borne infections, certain wild urban birds can serve as amplifying hosts or carriers of infected preimaginal ixodid ticks, contributing thus to the circulation of dis- ease agents in urban areas Table 8.1. Moreover, allergic responses to ectoparasites of feral pigeons have not been included in Table 8.1 and are another consideration.

8.4.2. Monitoring and surveillance

A prerequisite for managing urban birds and their potential public health hazard is the nitrogenous compounds contained in bird droppings, and the birds thus serve not as hosts for these microorganisms, but as lessorsfor them. This could pose a public health hazard in the case of mass communal roosts or large nesting colonies of birds at urban or subur- ban sites inhabited, exploited or attended by people. In these cases, airborne inhalation is the main means of infection in people, and it usually occurs during rebuilding or related work in contaminated areas. In general, the prevailing modes of transmission of pathogens from birds to people in urban areas are either via airborne or alimentary routes. An airborne, respiratory infec- tion is the commonest mode in, for example, ornithosis, avian tuberculosis, cryptococco- sis and histoplasmosis, while infection by ingestion might occur in, for example, salmo- nellosis, campylobacterosis, colibacillosis, listeriosis, toxoplasmosis and cryptosporidiosis, which are food-borne or water-borne diseases. Less frequently, some zoonotic infections in urban areas are transmitted by direct contact with birds, suffering from, for example, erysipeloid, streptococcosis, or pseudotuberculosis. Finally, arthropod-borne diseases such as Eastern and Western equine encephalomyelitis, Sindbis fever, West Nile fever, TBE and Lyme borreliosis are caused by haematophagous invertebrates such as mos- quitoes and ixodid ticks that acquired the infectious agent previously, by feeding on viraemic or bacteraemic urban birds. A number of ecological factors might affect the risk of bird-borne illness in urban set- tings. For example, bird species that have higher population densities such as feral pigeons; that nest in colonies such as colonial waterbirds, gulls and rooks; that roost gregariously such as starlings, grackles, corvids and gulls; and that congregate at water and food sources such as terrestrial birds or in other particular places in urban areas for mass moulting such as waterfowl in summer, migration stops and overwintering such as waterfowl and gulls are more important epidemiologically due to frequent interin- dividual contacts that enable effective horizontal transmission of disease agents than spe- cies with low population densities that live solitarily or in small groups. Habitat prefe- rences by birds also affect their epidemiological role. For example, aquatic birds, even in urban situations, attract higher numbers of haematophagous insects such as mosquitoes than do terrestrial birds, while woodland, ground-foraging birds are parasitized by ixo- did ticks. Avian mobility and migratory habits are other crucial factors; they make the transport and spread of various agents by carrier birds more effective. In brief, the most important factors that increase the risk of bird-borne infections are: • overpopulation of infected urban birds; • overpopulation of infected invertebrate vectors in the case of arthropod-borne diseases; and • enhanced, intimate contacts between people and infected urban birds or their habitats the latter case when urban birds serve as a lessor of the agent or both. Public Health Significance of Urban Pests Birds 263 262 effective decontamination of the soil under communal roosts infected with sapronotic fungi H. capsulatum is possible by repeated 3–4 times use of 3 formaldehyde Tosh et al., 1967; • reducing the number of nest boxes available for starlings; • trapping birds in nets or various bird traps and euthanizing the captured birds, if per- mitted; and • sterilizing birds chemically, with a treated grain bait, if permitted. These activities should be carried out in an integrated approach to bird management, since individual steps alone do not produce success. Furthermore, inspection and control measures must be performed by, or under the supervision of, veterinary public health agencies – and only when they are substantiated and necessary. Ornithologists, wildlife managers and citizen representatives such as consumers should be involved in imple- menting the control measures. The integrated approach to bird management also needs a public education component media and a legal regulatory component – that is, poli- tical support – as necessary parts of the process. Finally, a risk–benefit analysis should also be performed.

8.4.4. Techniques for dispersing birds in cities