Animal Waste, Water Quality and Human Health

124Animal Waste, Water Quality and Human Healthused to control infectious diseases in domestic animals and may be applicable toanimal pests such as rodents and mosquitoes, but this approach is not acceptablefor wildlife species thought to play an important ecological role or that areconsidered endangered. In this situation, control in wildlife is more difficult,which in turn fosters persistence of disease in livestock populations e.g. it isthought that attempts to eradicate bovine tuberculosis have been frustrated bythe inability to control Mycobacterium bovis infections in badger (Meles meles)populations in the United Kingdom (Delahay et al. 2003) and possums in NewZealand. Another example is leptospirosis which mainly occurs in humidtropical climates due to contamination of water with urine from infected wild orferal animal species. Control of leptospirosis in these species is challenging,given the variety of Leptospira interrogans serovars that are encountered in thewild animal reservoir and the cost of vaccination and eradication programmes.There are some non-lethal approaches to control zoonoses in wildlife, especiallyuse of vaccines. One of the few successful uses has been in the control of fox rabiesin northern Europe and Switzerland (Wandeler et al. 1988). In the vaccinationprogramme, food baits impregnated with a modified-live rabies virus weredistributed in the countryside. Aguilar-Setien et al. (2002) reported on thepotential use of a vaccinia-rabies glycoprotein recombinant virus aerosol forcontrol of rabies in vampire bats (Desmodus rotundus). Attempts have beenmade to vaccinate raccoons, skunks, coyotes, mongooses, and bats (Creekmoreet al. 1994, Aguilar-Setien et al. 2002, Hanlon et al. 2002, Linhart et al. 2002)with either aerosol or bait vaccines against rabies virus. Vaccines have also beendeveloped against brucellosis in feral swine and wild ruminants (Davis & Elzer2002) and the plague bacillus, Yersinia pestis, in rodents. Aerosol or baitvaccines may be useful for the control of certain waterborne zoonotic pathogens.Also, contraceptive vaccines have been developed to bring about control ofwildlife populations that may carry zoonotic diseases (Barber 2000, Mate et al.2003, Smith & Cheeseman 2002).4.3.5 Reducing exposure from litter and beddingLitter and bedding can provide an ideal environment for pathogen survival andgrowth. Poultry litter is commonly treated with agents such as aluminium sulfateand sodium bisulfate to limit the survival of bacterial pathogens. These littertreatments significantly reduced Campylobacter colonization in the caeca ofchickens, but had no effect on Salmonella colonization (Line 2001). If poultrylitter has high moisture content, very high bacterial cell numbers may be found.To prevent wet litter, moisture absorbing bedding material (softwood shavings)is used and heating and ventilation systems monitored to allow control of