Waterborne diseases

Waterborne diseases are caused by pathogenic microorganisms that most commonly are transmitted in contaminated fresh water. Infection commonly results during bathing, washing, drinking, in the preparation of food, or the consumption of food thus infected. Various forms of waterborne diarrheal disease probably are the most prominent examples, and affect mainly children in developing countries; according to the World Health Organization, such diseases account for an estimated 4.1% of the total DALY global burden of disease, and cause about 1.8 million human deaths annually. The World Health Organization estimates that 88% of that burden is attributable to unsafe water supply, sanitation and hygiene.^[1]

Overview

The term "waterborne disease" is reserved largely for infections that predominantly are transmitted through contact with or consumption of infected water. Trivially, many infections may be transmitted by microbes or parasites that accidentally, possibly as a result of exceptional circumstances, have entered the water, but the fact that there might be an occasional freak infection need not mean that it is useful to categorise the resulting disease as "waterborne". Nor is it common practice to refer to diseases such as malaria as "waterborne" just because mosquitoes have aquatic phases in their life cycles, or because treating the water they inhabit happens to be an effective strategy in control of the mosquitoes that are the vectors.

Microorganisms causing diseases that characteristically are waterborne prominently include protozoa and bacteria, many of which are intestinal parasites, or invade the tissues or circulatory system through walls of the digestive tract. Various other waterborne diseases are caused by viruses. (In spite of philosophical difficulties associated with defining viruses as "organisms", it is practical and convenient to regard them as microorganisms in this connection.)

Yet other important classes of water-borne diseases are caused by metazoan parasites. Typical examples include certainNematoda, that is to say "roundworms". As an example of water-borne Nematode infections, one important waterborne nematodal disease is Dracunculiasis. It is acquired by swallowing water in which certain copepoda occur that act as vectors for the Nematoda. Anyone swallowing a copepod that happens to be infected with Nematode larvae in the genusDracunculus, becomes liable to infection. The larvae cause guinea worm disease.^[2]

Another class of waterborne metazoan pathogens are certain members of the Schistosomatidae, a family of blood flukes. They usually infect victims that make skin contact with the water.^[2] Blood flukes are pathogens that cause Schistosomiasis of various forms, more or less seriously affecting hundreds of millions of people world-wide.^[3]

Long before modern studies had established the germ theory of disease, or any advanced understanding of the nature of water as a vehicle for transmitting disease, traditional beliefs had cautioned against the consumption of water, rather favouring processed beverages such as beer, wine and tea. For example, in the camel caravans that crossed Central Asiaalong the Silk Road, the explorer Owen Lattimore noted, "The reason we drank so much tea was because of the bad water. Water alone, unboiled, is never drunk. There is a superstition that it causes blisters on the feet."^[4]

Protozoal infections

Disease and Transmission	Microbial Agent	Sources of Agent in Water Supply	General Symptoms
Amoebiasis(hand-to-mouth)	Protozoan (Entamoeba histolytica) (Cyst-like appearance)	Sewage, non-treated drinking water, flies in water supply	Abdominal discomfort,fatigue, weight loss,diarrhea, bloating, fever
Cryptosporidiosis(oral)	Protozoan (Cryptosporidium parvum)	Collects on water filters and membranes that cannot bedisinfected, animal manure, seasonal runoff of water.	Flu-like symptoms, watery diarrhea, loss of appetite, substantial loss of weight,bloating, increased gas,nausea
Cyclosporiasis	Protozoan parasite (Cyclospora cayetanensis)	Sewage, non-treated drinking water	cramps, nausea, vomiting, muscle aches, fever, and fatigue
Giardiasis (fecal-oral) (hand-to-mouth)	Protozoan (Giardia lamblia) Most common intestinal parasite	Untreated water, poor disinfection, pipe breaks, leaks,groundwater contamination, campgrounds where humans and wildlife use same source of water. Beavers andmuskrats create ponds that act as reservoirs for Giardia.	Diarrhea, abdominal discomfort, bloating, andflatulence
Microsporidiosis	Protozoan phylum (Microsporidia), but closely related to fungi	Encephalitozoon intestinalis has been detected ingroundwater, the origin of drinking water [5]	Diarrhea and wasting inimmunocompromisedindividuals..

Parasitic infections (Kingdom Animalia)[edit]

Disease and species	Microbial Agent	Sources of Agent in Water Supply	General Symptoms
Schistosomiasis(immersion)	Members of the genusSchistosoma	Fresh water contaminated with certain types of snails that carryschistosomes	Blood in urine (depending on the type of infection), rash or itchy skin. Fever, chills, cough and muscle aches
Dracunculiasis(Guinea Worm Disease)	Dracunculus medinensis	Stagnant water containing larvae, generally in parasitised Copepoda	Allergic reaction, urticaria rash, nausea, vomiting, diarrhea, asthmatic attack.
Taeniasis	Tapeworms of the genusTaenia	Drinking water contaminated with eggs	Intestinal disturbances, neurologic manifestations, loss of weight,cysticercosis
Fasciolopsiasis	Fasciolopsis buski	Drinking water contaminated with encysted metacercaria	GIT disturbance, diarrhea, liver enlargement, cholangitis, cholecystitis, obstructive jaundice.
Hymenolepiasis(Dwarf Tapeworm Infection)	Hymenolepis nana	Drinking water contaminated with eggs	Abdominal pain, severe weight loss, itching around the anus, nervous manifestation
Echinococcosis(Hydatid disease)	Echinococcus granulosus	Drinking water contaminated with feces (usually canid) containing eggs	Liver enlargement, hydatid cysts press on bile duct and blood vessels; if cysts rupture they can cause anaphylactic shock
coenurosis	multiceps multiceps	contaminated drinking water with eggs	increases intracranial tension
Ascariasis	Ascaris lumbricoides	Drinking water contaminated with feces (usually canid) containing eggs	Mostly, disease is asymptomatic or accompanied byinflammation, fever, and diarrhea. Severe cases involve Löffler's syndrome in lungs, nausea, vomiting, malnutrition, andunderdevelopment.
Enterobiasis	Enterobius vermicularis	Drinking water contaminated with eggs	Peri-anal itch, nervous irritability, hyperactivity and insomnia

Bacterial infections

Disease and Transmission	Microbial Agent	Sources of Agent in Water Supply	General Symptoms
Botulism	Clostridium botulinum	Bacteria can enter an open wound from contaminated water sources. Can enter the gastrointestinal tract through consumption of contaminated drinking wateror (more commonly) food	Dry mouth, blurred and/or double vision, difficulty swallowing, muscle weakness, difficulty breathing, slurred speech, vomiting and sometimes diarrhea. Death is usually caused by respiratory failure.
Campylobacteriosis	Most commonly caused byCampylobacter jejuni	Drinking water contaminated with feces	Produces dysentery like symptoms along with a high fever. Usually lasts 2–10 days.
Cholera	Spread by the bacterium Vibrio cholerae	Drinking water contaminated with the bacterium	In severe forms it is known to be one of the most rapidly fatal illnesses known. Symptoms include very watery diarrhea, nausea, cramps, nosebleed, rapidpulse, vomiting, and hypovolemic shock (in severe cases), at which point death can occur in 12–18 hours.
E. coli Infection	Certain strains ofEscherichia coli(commonly E. coli)	Water contaminated with the bacteria	Mostly diarrhea. Can cause death inimmunocompromised individuals, the very young, and the elderly due to dehydration from prolonged illness.
M. marinuminfection	Mycobacterium marinum	Naturally occurs in water, most cases from exposure inswimming pools or more frequently aquariums; rare infection since it mostly infects immunocompromisedindividuals	Symptoms include lesions typically located on the elbows, knees, and feet (from swimming pools) or lesions on the hands (aquariums). Lesions may be painless or painful.
Dysentery	Caused by a number of species in the generaShigella andSalmonella with the most common being Shigella dysenteriae	Water contaminated with the bacterium	Frequent passage of feces with blood and/or mucusand in some cases vomiting of blood.
Legionellosis (two distinct forms: Legionnaires' disease and Pontiac fever)	Caused by bacteria belonging to genusLegionella (90% of cases caused by Legionella pneumophila)	Contaminated water: the organism thrives in warm aquatic environments.	Pontiac fever produces milder symptoms resembling acute influenza without pneumonia. Legionnaires' disease has severe symptoms such as fever, chills, pneumonia (with cough that sometimes producessputum), ataxia, anorexia, muscle aches, malaise and occasionally diarrhea and vomiting
Leptospirosis	Caused by bacterium of genus Leptospira	Water contaminated by the animal urine carrying the bacteria	Begins with flu-like symptoms then resolves. The second phase then occurs involving meningitis, liverdamage (causes jaundice), and renal failure
Otitis Externa(swimmer's ear)	Caused by a number ofbacterial andfungal species.	Swimming in water contaminated by the responsible pathogens	Ear canal swells, causing pain and tenderness to the touch
Salmonellosis	Caused by many bacteria of genusSalmonella	Drinking water contaminated with the bacteria. More common as a food borne illness.	Symptoms include diarrhea, fever, vomiting, and abdominal cramps
Typhoid fever	Salmonella typhi	Ingestion of water contaminated with feces of an infected person	Characterized by sustained fever up to 40 °C (104 °F), profuse sweating; diarrhea may occur. Symptoms progress to delirium, and the spleen andliver enlarge if untreated. In this case it can last up to four weeks and cause death. Some people with typhoid fever develop a rash called "rose spots", small red spots on the abdomen and chest.
Vibrio Illness	Vibrio vulnificus,Vibrio alginolyticus, andVibrio parahaemolyticus	Can enter wounds from contaminated water. Also got by drinking contaminated water or eating undercooked oysters.	Symptoms include Abdominal tenderness, Agitation, Bloody stools, Chills, Confusion, Difficulty paying attention (attention deficit), Delirium, Fluctuating mood, Hallucination, Nosebleeds, Severe fatigue, slow, sluggish, lethargic feeling, weakness.

Viral infections

Disease and Transmission	Microbial Agent	Sources of Agent in Water Supply	General Symptoms
SARS (Severe Acute Respiratory Syndrome)	Coronavirus	Manifests itself in improperly treated water	Symptoms include fever, myalgia, lethargy, gastrointestinalsymptoms, cough, and sore throat
Hepatitis A	Hepatitis A virus (HAV)	Can manifest itself in water (and food)	Symptoms are only acute (no chronic stage to the virus) and include Fatigue, fever, abdominal pain, nausea, diarrhea, weight loss, itching, jaundice and depression.
Poliomyelitis(Polio)	Poliovirus	Enters water through the feces of infected individuals	90-95% of patients show no symptoms, 4-8% have minor symptoms (comparatively) with delirium, headache, fever, and occasionalseizures, and spastic paralysis, 1% have symptoms of non-paralyticaseptic meningitis. The rest have serious symptoms resulting inparalysis or death
Polyomavirus infection	Two ofPolyomavirus:JC virus andBK virus	Very widespread, can manifest itself in water, ~80% of the population has antibodies to Polyomavirus	BK virus produces a mild respiratory infection and can infect thekidneys of immunosuppressed transplant patients. JC virus infects the respiratory system, kidneys or can cause progressive multifocal leukoencephalopathy in the brain (which is fatal).

Socioeconomic impac

Waterborne diseases can have a significant impact on the economy, locally as well as internationally. People who are infected by a waterborne disease are usually confronted with related costs and not seldom with a huge financial burden. This is especially the case in less developed countries. The financial losses are mostly caused by e.g. costs for medical treatment and medication, costs for transport, special food, and by the loss of manpower. Many families must even sell their land to pay for treatment in a proper hospital. On average, a family spends about 10% of the monthly households income per person infected.

Source:From Wikipedia, the free encyclopedia