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Effects of pollutants on the aquatic environment
Effects of pollutants on the aquatic environment

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7.9 Typical pathogens

Table 3 lists some of the major pathogens that cause disease to humans and are likely to be found in polluted water.

Table 3  Some of the major pathogens likely to be present in sewage and in faecally polluted streams
Organism typeOrganismDiseaseRemarks
BacteriaVibrio choleraeCholeraTransmitted via sewage and polluted waters in cholera-endemic areas
Salmonella typhiTyphoid feverCommon in sewage
Salmonella paratyphiParatyphoid feverCommon in sewage
Salmonella spp.Food poisoningCause of food poisoning; usually found in contaminated food of animal origin
Shigella spp.Bacillary dysenteryPolluted waters are main source of infection
Bacillus anthracisAnthraxCan be found in effluents from tanneries processing hides from infected animals; spores resistant to treatment
Brucella spp.Brucellosis (Malta fever) in humans; contagious abortion in sheep, goats and cattleNormally transmitted by infected milk or by contact
Leptospira icterohaemorrhagiaeLeptospirosis (Weil’s disease)Carried by sewer rats; also present in water contaminated by urine from infected animals and humans; can infect through cuts in skin, or intact skin if immersed for a long time
VirusesPoliovirusPoliomyelitisTransmitted by faecal–oral route via contaminated food or water
Hepatitis A virus (HAV)Hepatitis ATransmitted by faecal–oral route via contaminated food or water
ProtozoaEntamoeba histolyticaAmoebic dysenterySpread by contaminated waters and sludge used as fertiliser; common in warm countries
Giardia lambliaGiardiasisFound in inadequately treated water
Cryptosporidium spp.CryptosporidiosisCarried by agricultural livestock and infected persons
HelminthsTaenia saginataTapewormsEggs very resistant, present in sewage sludge and sewage effluents; can be present in contaminated water sources and food
Ascaris lumbricoidesNematode wormsPresent in sewage effluents and dried sludge used as fertiliser
Schistosoma haematobium, Schistosoma mansoniBilharziaCarried by water snails in rivers and irrigation ditches contaminated by human waste in specific regions of the world; enter humans by direct penetration of skin