Animal Waste, Water Quality and Human Health

Assessing the importance of zoonotic waterborne pathogens 49stream. However, the organism may persist in several “immunologicallyprivileged” sites such as the renal tubules, brain, eye and genital tract. Onceestablished in the renal tubules and/or genital tracts of animals, pathogenicleptospires can be passed in the urine and placental fluids, for periods from afew days to several weeks. Chronically infected animals act as the reservoir forthe organism and act as the source of infection for herd mates and other animals.Specific serovars tend to be maintained in specific host animal speciesreservoirs; however, there are overlaps and shifts in serovar occurrence amongdifferent domestic and wild animals.Leptospirosis in humans is almost always derived either directly or indirectlyfrom animal sources (McBride et al. 2005). While many domestic and wildlifespecies can be the source of human infections, rodents are considered the mostimportant reservoir host worldwide. Individuals in certain occupations are at ahigh risk for developing leptospirosis; these include abattoir workers,veterinarians, and sugar cane and rice farmers (Acha & Szyfres 1987; Heath &Johnson 1994). Recently, leptospirosis has also been associated withrecreational activities, travel and adventure tourism (McBride et al. 2005).Typical symptoms of leptospirosis in humans include fever, jaundice and renalfailure; however, the specific manifestations of disease are highlyserovar-dependent. A study of one waterborne outbreak associated withrecreational water showed that there was an increased likelihood of developingleptospirosis in individuals with the human leukocyte antigen-DQ6, stronglysuggesting that there is a genetically based difference in susceptibility to theinfection among humans (Lingappa et al. 2004).Leptospirosis is endemic in animal and human populations in many tropical andsubtropical developing nations. McBride et al. (2005) noted that leptospirosis is adisease of urban slum dwellers and the rural poor and that Brazil, India and Chinahave a high incidence of human leptospirosis. Leptospira was responsible for anepidemic of severe pulmonary haemorrhagic syndrome in a rural community inNicaragua in 1995 (Trevejo et al. 1998). The outbreak is thought to have beencaused by flood waters contaminated with urine from infected dogs.In industrialized countries leptospirosis is usually sporadic; however, epidemicshave also been reported. Human infections with Leptospira are uncommon in thecontinental USA, but are more frequent in the Hawaiian Islands where about 300cases were reported from 1999 to 2006. This is a clear case where the ecology ofthe pathogen has to be taken into consideration. The tropical/subtropical climatesare more likely to lead to environmental growth of this pathogen. Puerto Rico andFlorida are likely to be afflicted by this pathogen. Preliminary studies in PuertoRico have demonstrated the presence of Leptospira spp in fresh water lakes(Toranzos, unpublished data), and there are sporadic human cases reported.