Characteristics of organic wastes 67
It is obvious from these tables that human wastes (excreta and wastewater) are a
source of health hazards to the public and are the beginning of the transmission
route of many diseases. The engineering profession responsible for the
collection, transport, treatment and disposal/reuse of these wastes must be aware
of the potential infectivity and transmission of these diseases, so as to be able to
ensure that these pathogens do not pose an actual threat to human health. Details
of these diseases, their modes of transmission and die-offs can be found in
"Sanitation and Disease" by Feachem et al. (1983).
Animals and their manure can also be sources of disease transmission to
human beings. The term "zoonoses" is defined as those diseases and infections
which are naturally transmitted between man and other vertebrate animals.
There are two groups of zoonoses. In the first group, animals act as hosts
alternative to man, for example the protozoon Balantidium (Table 2.22). In this
case both human excreta and animal manure have to be properly controlled to
avoid transmission of the disease. Taenia (Table 2.22) is an example of the
second group of zoonoses in which the animals (either cow or pig) are the
intermediate step in the disease transmission. Inactivation of Taenia ova in the
feces or consumption of well-cooked beef or pork will prevent the transmission
of Taeniasis. Therefore the control of either human excreta or animal manure
would be sufficient in controlling the spread of the second group of zoonoses.
Some of the zoonoses relating to viral, rickettsial and bacterial diseases are
given in Table 2.24, while those relating to protozoan and helminthic infections
are shown in Table 2.25.
Table 2.25 Partial list of parasitic zoonoses
Disease in humans Causative organism Vertebrate animals
principally involved
1.Protozoa infections
Amoebiasis Entamoeba histolytica Nonhuman primates,
dogs
Babesiosis Babesia divergens Cattle
Babesia microti Voles, mice
Balantiduasis Balantidium coli Swine, rats, nonhuman
primates
Giadiasis Giardia spp. Beavers
Sarcoporidiosis intestinal Sarcocystis miesheriana
(syn. S. suihominis; =
Isospora hominis proparte)
Pigs
Sarcocytis hominis (syn. S.
bovihominis; = Isospora
hominis proparte)
Cattle
Toxoplasmosisa Toxoplasma gondii Cats, mammals, birds