VPE 511: Environment and Environmental Hygiene (2+1)

SEWAGE AND ANIMAL HEALTH

• It has frequently been alleged that the drinking water polluted by domestic sewage has given rise to symptoms of poisoning in cattle and other animals.
• It has been affirmed that cattle may be rendered ill by drinking water containing sewage. In this connection it is important to make it clear that there are two kinds of sewage namely household or domestic sewage and industrial sewage. The latter consists of waste products from factories and its composition will naturally vary with the industry concerned, but if it contains some poison whether chemical or bacteriological it is liable to cause harmful effects on stock. Domestic sewage is also a product of variable composition and consists of water containing human faeces and urine as well as kitchen waste.
• It is especially in connection with the effluent from works engaged in the disposal of domestic sewage that so called sewage poisoning of animals and particularly cattle has been alleged. It has been stated that the symptoms of so called sewage pollution in cattle resemble in some respects those of johne’s disease , and there can be no doubt that streams contaminated with faeces from cattle with Johne’ s disease play a large part in the spread of infection. Intestinal parasites such as nematodes are also quite commonly transmitted in a similar manner, and in countries where the human population carries the cestode T. saginata, cattle grazed on the sewage farms become invariably infected with cysticercus bovis from the eggs which have been passed in the human feaces. There is possibility that bacteria pathogenic to cattle may be also conveyed by water.
• In general human sewage does not injure cattle, since cattle and other stock are commonly kept on sewage farms where they eat grass wet with sewage and even drink sewage with no apparent harm.
• On the other hand there is plenty of evidence that some industrial effluents are definitely poisonous for animals. Thus cyanide in toxic amounts have been found in the drinking water of animals on several occasions, which is being discharged into drinking water in the effluent from factories.
• The method of sewage disposal may be divided broadly into the conservancy and water carriage systems.