Microbes and Plants - Freshwater Ecology: Concepts and Environmental Applications - page 126

VIRUSES

All organisms have viruses. Viruses are not really organisms because
they cannot survive without a host and are not capable of basic metabolic
function. Nonetheless, they are important in population dynamics of
aquatic organisms, aquaculture, and public health (Table 8.1). Viruses also
transfer genetic material among microorganisms, so they can be important
in issues related to release of genetically engineered microorganisms into
the environment.
Viruses are very small particles (25-350 nm) that remain in suspen-
sion. Particles that look like known viruses are commonly seen in lakes
when scanning electron microscopy is used (Fig. 8.2). It is difficult to de-
termine if particles that look like viruses are actually infectious and to de-

TABLE 8.1 Organisms Causing Human Diseases That Can Be Transmitted by
Water or Wastewater a

Group Organisms Disease/symptoms

Bacteria Salmonella spp. Typhoid fever, paratyphoid fever,

gastroenteritis

Shigella spp. Gastroenteritis, dysentery

Vibrio cholerae Cholera

Escherichia coli Gastroenteritis

Leptospira Weil's disease

icterohaemorrhagiae
Campylobacter spp. Gastroenteritis

Yersinia enterocolotica Gastroenteritis

Mycobacterium spp. Tuberculosis/respiratory illness

Legionella pneumophila Legionnaire's disease/acute

respiratory illness

Virus Hepatitis A Liver disease

Norwalk agent, rotaviruses, Gastroenteritis

astroviruses
Poliovirus Polio

Coxsackievirus Herpangia/menengitis, respiratory

illness, paralysis, fever

Enteroviruses (68-71) Pleurodynia/ menengitis,

pericardities, myocarditis

Protozoa Giardia lamblia Diarrhea, abdominal pains,

nausea, fatigue, weight loss

Entamoeba histolytica Acute dysentery

Acanthomoeba castellani, Meningioencephalitis

Naegleria spp.
Balantidium coli Dysentery

Cryptosporidium spp. Dysentery

Helminths Nematodes ( Ascaris lumbricoides, Intestinal obstruction in children

Trichuris trichiura )
hookworms ( Necator Americanus, Hookworm disease/

Ancylostoma duodenale ) gastrointestinal tract

tapeworms ( Taenia spp.) Abdominal discomfort, hunger pains

Schistosoma mansoni Schistosomiasis (liver, bladder, and

large intestine)

a Adapted from Bitton (1994).