Environmental Microbiology of Aquatic and Waste Systems

8.1 Disease Transmission Through Drinking Water 193

aquatic environment before intake. While the toxic
peptides (e.g., microcystins) are usually contained
within the cells (Falconer and Humpage 2005 ) and
thus may be largely eliminated by filtration, toxic alka-
loids such as cylindrospermopsin and neurotoxins are
also released into the water and may break through
filtration systems (see Fig. 8.4).

8.1.2 Disease Outbreaks in Drinking Water

Due to the Presence of Chemicals,

and Biotoxins

It should be pointed out that water-borne diseases are

not restricted to communicable diseases (Fig 6.2); some

water-associated diseases are caused by chemicals or

lack of them. For example, it has been shown that mor-

tality due to cardio-vascular disease incidence is higher

by at least 24% in towns with soft water than in those

with hard water. Cities with high amounts of magne-

sium (Mg2+) and calcium (Ca2+), the ions responsible

for hardness, show lower incidence of cardiovascular

disease by 17% and 22% respectively. Goiter and tooth

decay have been attributed to the absence of iodine and

fluoride respectively, in drinking water. On the other

hand, nitrate levels have been incriminated with metha-

nogloblinemia in infants; while yet unknown chemicals

in water have been implicated with the high incidence

of bladder cancer in some cities. Although the short-

term or long-term presence or absence of certain

amounts of some chemicals in drinking water is impor-

tant, the incidence of water borne diseases due to micro-

organisms and biological agents appears far more

important, especially in developing countries.

Biotoxins are sometimes produced in drinking water

by cyanobacteria. Examples are the neurotoxin, anatox-

ins and the cytotoxin, cylindrospermopsin (Fig. 8 .4).

8.1.2.1 Brief Notes on Some Water-Borne

Diseases

This section will give some insight into the nature of

waterborne diseases (Anonymous 2006b).

Cholera

Frequently called Asiatic cholera or epidemic cholera,

the disease is caused by the Gram-negative, comma-

shaped bacterium Vibrio cholera with a single polar

flagellum. Cholera is characterized by a diarrhea with

profuse watery stool, vomiting, rapid dehydration, fall

of blood pressure, subnormal temperature and collapse

may occur within 48 h unless medical care is given.

The bacterium produces cholera toxin, an enterotoxin,

whose action on the mucosal epithelium lining of the

small intestine is responsible for the characteristic

massive diarrhea of the disease. In its most severe

forms, cholera is one of the most rapidly fatal illnesses

known; a healthy person may become hypotensive

within an hour of the onset of symptoms and may die

N 1

N

R 4

R (^2) R 3
R 5
OH
NH3

• H 2 N


• 
  

  R 1 N
  H
  H
  H
  2
  3 4
  5
  6
  N
  10
  11
  (^1214)
  15
  17
  7
  8
  16
  N
  N
  CH 3
  CH 2
  O
  P O
  OH
  OH 3
  CH 3
  NH 4

  
  

+

+

(^321)
45 O CH 3
NH 3

• 12
  3
  4
  (^65)
  7
  8
  9
  10
  General structure of anatoxins
  Anatoxin -a (S)
  MW 252: C 7 H 17 N 4 O 4 P
  Anatoxin-a
  MW252:C 10 H 15 NO
  OCH 3
  COOH
  H 3 C
  H 3 C
  H 3 C
  CH 3
  Microcystin
  Cylindrospermopsin

• O 3 SO

OH

O

O

CH 2

O

O

NH

NH

HN N

OO

O

O

R2

NH

N NH

Me

HN NH

NH

H R1

N

H

N

[Y]

O COOH O

[X]

Fig. 8.4 Akaloid neurotoxins from Cyanobacteria (From Falconer
and Humpage 2005. With permission)