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Consider the global impact of a waterborne infectious disease (which may be caused by a bacterium or parasite) and discuss current methods for detection, treatment and prevention
Waterborne Diseases are associated with lack clean drinking water supply and contaminated the water by pathogenic micro-organism and causes infection. This contamination occurs by human or animal faeces. The major human health problems are related to failure to supply clean water for more than quarter of the world's population. Outbreaks of infectious intestinal illness occur because of pollution of drinking water supply have consequences of economic cost, to reduce this economic cost that is important to investigated as soon as possible and prevention the causes of an outbreak. By recognised the main causes of contaminated of drinking water, which could be possible to prevent those factors causes outbreaks the disease and water contamination event, (Hrudey et al., 2003)
Diseases are associated with waterborne are characterized by infection of digestive system and acute diarrhoea, vomiting and fever. Waterborne disease is more common in the developing countries
The consequence of waterborne disease there are a quite a lot of types of pathogenic micro-organism like bacteria, viruses and parasites presence in contaminated water. Most of these have been involved in much type of diseases passing by water. Every eight seconds a child dies because of drinking unsafe water and almost five million people die in the world because of the waterborne disease. (WHO, 2001)
Cholera is a gram negative and causes an acute infection of the intestine caused by bacterium Vibrio cholerae. It is classified as a waterborne infection illness while ingestion of contaminated water. Cholera is an infectious disease that can occur when there is lack of clean drinking water or adequate sewage disposal. It is incubated in one to five days, Vibrio cholerae produce cholera toxin the model for enterotoxin that is causes a painless watery diarrhoea then severe dehydration and electrolytic imbalance and death if not be treat it soon also vomiting is common in most of patients.
The clinical characterized of cholera is an acute diarrhoeal disease, and intestinal infected by toxigenic bacterium Vibrio choleae serogroup O1 or O139, these two serogroup are responsible for epidemic cholera, serogroup O1 is divided into two biotypes, (classical and EI Tor) O1 serogroup has been analyzed genetically and revelled dissimilarity in different genes among these biotypes cholera toxin (CT) causes disease cholera. Have two immunologic forms (CT1 and CT2). Three genotypes of cholera toxin B subunit gene (ctxB) were recognized. A few years ago Vibrio cholerae O1 classical and EI Tor biotype has been founded in some countries in Asia and Africa. (Amit et al., 2009)
Infection can be mild or sever: about 5% of those are infected people have severed disease characterized by plenty watery diarrhoea, vomiting and leg pain, and people with this condition they are losing plenty of body fluids this is causes dehydration and electrolytic if not be treated, death can occur within short period. (Nicholas, et al. 2007)
Cholera was reduced in the developed countries by water treatment, but still causes morbidity and mortality in developing countries, particularly where it is lack of clean drinking water.
At beginning; V. Cholera strains appear in the environment and than spread in public especially in the heavy rain and flood. The environment and climate lead to spread the cholera in so many countries especially in Africa. In 2003 world health organization (WHO) collected the reports from 45 countries, about 11,575 persons are infected by cholera and 1,894 deaths. The most of cholera cases event in sub-Saharan Africa. (World Health Organization, 2003).
Cholera is caused by a protein toxin called choleragen. This is secreted by the intestinal bacterium Vibrio cholera. Choleragen toxin alters the G-proteins in cells lining the intestine.
This causes water to be pumped continuously out of the cells into the intestines. As a consequence severe diarrhoea occurs.
Mechanism of action:
Cholera toxin adds Adenosine diphosphate ADP-ribose to G protein subunits to prolong their activation, G protein is trapped in the active or "on" conformation. This causes the signal-transduction pathway to be continually stimulated and therefore the active G protein continuously activates protein kinase A (PKA). PKA opens a chloride channel (CFTR channel) and inhibits the Na+-H+ exchanger by phosphorylation. The net result of the phosphorylation of these channels is an excessive loss of NaCl and the loss of large amounts of water into the intestine. This causes dehydration and death if not be treated in the a few hours (Sack, 2004)
Diagnosis of cholera
Previously the culture methods are used for detection of Vibrio cholera this method is an accurate but it is slower Microbiologic services are usually not presented in cholera endemic location, which are often characterized by poverty, or under urgent situation such as natural disasters, wars, refugee crisis, and population displacements. A perfect rapid test would be helpful for the early detection of cholera outbreak to be easily controlled the situation. (Xuan et al., (2006)
Immunochromatoggraphic dipstick is the fast test for diagnosis cholera, this method is currently used for rapid detection of Vibrio cholerae from faeces sample or rectal swab, and dipsticks have been developed by Institute Pasteur in Paris, and successfully been used in Madagascar and Bangladesh, where it showed shows potential levels of sensitivity and specificity (Bhuiyan, et al., 2003)
Dipsticks test is take a few minutes, this method significantly progresses cholera surveillance in the far destination.
The feces samples collect from the patient with severe watery diarrhoea .the sample obtain by rectal catheter from the patient or obtain a rectal swab. Sample of stool site in Cary-Blair transport medium, the sample of stool transfer in to plastic dish and then sent to clinical laboratory.
Usually the bacteriological culture is required, the sample of faeces placed in to thiosulfate citrate bile salt sucrose (TCBS) agar and taurochlate tellurite gelatine agar (TTGA), and then the sample transfer to the TCBS and TTGA and then improvement in the alkaline peptone water (APW) incubation for 6 hours at 37°C. After incubation select the colonies on the agar for biochemical examination and agglutination with polyvalent. Non agglutinating strains test with antiserum to V. Cholera O139 strain.
The dipstick test use monoclonal antibodies specific to V. cholerae O1 lipopolysaccharide (LPS).
The rectal swab sample is entry inside the culture medium, which is then incubated for 4 hours at 37° C and then used for the dipstick test. The test strips read after 10 minutes of immersion in the APW suspension. The tests defined as positive when both a test line and control line appeared on the test strip (Wang et al., 2006)
The vibrio-cholera O1 and O139 dipsticks show sensitivities of 96% and 93%, in that order, and specificities of 92% and 98%. (Bhuiyan, NA. Et al (2003)) Dipstick test is use for rectal swab and it is the most significant for reliable estimation of many of cholera cases during an epidemic, and for early revealing of the emergence of a new epidemic.
The treatments available for cholera are oral antibiotics. Amongst the list of antibiotics, tetracycline is most prescribed drug for patients. Tetracycline works by inhibiting the translation process. Tetracycline binds to 30S ribosomal subunit and therefore prevents amino-acyl tRNA from binding to the A site of the ribosome. The binding is reversible in nature. Apart from tetracycline some patients are also prescribed with Doxycycline (Bhattacharya, 2003).
Prevention of cholera
Cholera can be prevented by using safe water for drinking or washing, contaminated water can be treated by boiling and disinfecting by chemical such as chlorine. And educated those people are living in the endemic area and advice them about food and water hygiene.
Cholera prevented by oral vaccination currently Dukoral vaccine is available, about 85% affective against the Vibrio cholera, dukoral vaccine is available in the UK and about 60 countries, oral vaccine is the best option for traveller when they are travelling to endemic cholera area (Lopez et al., 2007).
Importantly, vaccinations are effective if correct control measure are put in place alongside vaccination. Most of the current vaccinations are only effective against O1 strain therefore there is need to develop vaccine against O139 strain also. Because we know from several researches that O139 is becoming prevalent.