Animal Waste, Water Quality and Human Health

270Animal Waste, Water Quality and Human Health2004, Nichols 2008). Strains and serotypes of a range of virulence levels have alsobeen demonstrated for the waterborne bacterial pathogens: Campylobacter,pathogenic E. coli, Salmonella and Yersinia (Lightfoot 2004, Molbak & Scheutz2004, Percival et al. 2004).7.3.3 HostAspects that influence the susceptibility of the host include the type (degree) ofwater exposure, the duration of the contact period and the strength of thedefences or immunity exhibited. The nature of water activity also impacts themeans through which pathogens may gain entry into the human host. Threemain routes exist for the uptake or entry of pathogens during water-relatedactivities: inhalation, direct body contact and oral ingestion.7.3.3.1 InhalationAirborne pathogens in droplet form can enter the human respiratory tract as a resultof direct inhalation through the mouth or nasal passages. A number of natural andhuman-based actions can result in the production of aerosols containing microbes(Haas et al. 1999). These include waves, white-water spray and spray fromengine-driven water activities. In these contexts, inhalation can be a conceivableroute of entry for any primary or secondary-contact activity.7.3.3.2 Direct body contactFor direct body contact, small cuts or abraded skin, as well as prominent accesspoints like the eyes or ears are potential entryways for microbial pathogens.These routes would be considered of relevance for all primary-contact activities.Skin contact is the most frequent type of exposure during contact withnear-shore sands, soils or sediments. For secondary-contact recreational pursuits,exposed arms and legs constitute the most frequent points of contact; but it isalso important to consider that splashing can lead to additional exposurescenarios, and spills or falls can result in whole-body immersion. Schistosomes,whose infectious larvae are water-based, actively penetrate the skin of suitablehosts in contact with contaminated water.7.3.3.3 Oral ingestionFaecal microorganisms that are transmitted via the faecal-oral route and whichinfect the gastrointestinal tract are referred to as enteric pathogens (Haas et al.