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The diarrheal outbreak in Far- and Mid-Western regions of Nepal in 2009 was a cause for genuine concern as it affected over 5,000 individuals and caused more than 200 deaths. In Jajarkot district alone, more than 100 people died in just four months, with over 400 affected. Scientifically speaking, a bacterial strain by the name of Vibrio cholera was identified in almost 39 percent of the 15 samples tested. However, V. cholera is not the only pathogen capable of causing severe or fatal diarrhea in developing countries, Nepal being an example. A number of other bacterial and viral pathogens have been implicated in diarrheal outbreaks worldwide. Those include a number of Escherichia coli strains, Aeromonas strains, Campylobacter strains, Shigella strains, Salmonella strains, as the most pathogenic ones. Campylobacter strains are sometimes associated with food poisoning in diarrheal cases while Salmonella strains are known to be mostly associated with foodstuff and in some cases with contaminated drinking water. Aeromonas species is primarily associated with water and is known to cause cholera-like diarrheal symptoms, thus increasing the possibility of false diagnosis of cholera when this may not actually be the case.

In the Nepali context, V. cholera types have been implicated often in a larger number of occasions. The first report of cholera in Nepal was officially published for the years 1958 to 1960 by a medical doctor visiting Nepal. A total of 410 deaths over a three-year period in Kathmandu, with more than 3,000 affected, were reported. An outbreak of acute diarrheal disease in Kavre district during the year 2005 showed 31 percent cases positive for V. cholera. Using molecular (DNA/RNA of organisms as targets) method, a Japanese research group found that recent outbreaks in the country were mainly due to the V. cholera. A very recent study using latest molecular methods carried out by Center for Molecular Dynamics Nepal in collaboration with Nepal Health Research Council has found that diarrheal outbreak may be caused not only by V. cholera alone, but in a combination with other virulent pathogens, including Aeromonas species.

To date, the detection of diarrheal pathogens in Nepal has relied almost extensively on microbiological (growth of pathogens in culture media), biochemical (by-products of pathogenic metabolism) and serological tests (immune response of host to pathogen). These methods may have been useful until the recent past, but with the advent of molecular technology, same cannot be said anymore. Thus, the limited laboratory facilities in the government sector appears to have prevented early diagnosis of the recent 2009 outbreak considering that the first presumptive identification of the causative agent was only carried out and made public three months after the start of the outbreak. This may have contributed to delayed treatment as it is hard for a clinician to effectively suggest the dosage and frequency of medication in outbreak situations without a proper screening mechanism in place.

Many of the deaths due to diarrhea in Nepal have been caused as a result of dehydration resulting from loss of water and electrolytes (intestinal malabsorption or increased secretion). Replacement of these losses by oral rehydration solution is the mainstay of therapy for individuals with watery diarrhea. The treatment of diarrhea by water or water supplemented with salts (Oral Rehydration Solution) has been extensively promoted in endemic pockets in Nepal where the incidence of diarrheal outbreaks is high. However, in extreme cases, antibiotic needs to be administered. As an example, if we just take the case of two different causative agents of diarrheal outbreaks in developing countries, Vibrio species and Aeromonas species, the critical importance of prior diagnosis becomes apparent. The recommended medication for Aeromonas species is usually Cefixime, and most third-generation and fourth-generation cephalosporins (a family of antibiotics). However, in the case of V. cholera, Tetracycline is the usual antibiotic of choice, and in some cases, doxycycline, and other broad-spectrum antibiotics (another family of antibiotics). Thus, there are clearly differences in medication for the two different species and wrong medication for either could lead to delayed recovery and in the long term, development of antibiotic resistance by the pathogen.

The principle of PDTC (Prevention, Diagnosis Treatment and Care) has been the guiding light in major disease management in Nepal and elsewhere. However, in the case of diarrheal outbreaks, the relative emphasis needs to be adjusted. While prevention remains the mainstay strategy to deal with the problem of diarrhea, the need for correct diagnosis has emerged as the most important prong of the ladder for effective and efficient management of diarrheal diseases and epidemics as well as prevention of such future outbreaks. One of the major reasons is that traditional methods require that the pathogen be grown (cultured) in the laboratory. A large number of pathogens cannot survive very well outside the human body and thus may not be detected although they are present in the body. Methods that do not require culture such as biochemical tests and serological tests take time and are not very indicative of the actual bacterial species present. Therefore, molecular methods are the future of any disease diagnostics.

A comprehensive screening for presence of major pathogens, both bacterial and viral, can be carried out using this type of technology which is already available in Nepal. The use of these modern methods would not only result in rapid diagnosis, but also enable highly-specific identification of the actual pathogen(s) involved in a diarrheal outbreak. Therefore, modern methods of diagnosis should be explored, and utilized by the government health sector as well as external development partners working in health sector, for better management of future outbreaks. The cost of such diagnostic procedures which may be higher than traditional methods initially can be lessened tremendously if the capacity-building for molecular diagnosis is promoted within the country.

Dr Sameer M Dixit, PhD is the Country Director of Center for Molecular Dynamics Nepal (CMDN). Dr Mahesh Maskey, DSc is the Former Chair, Nepal Health Research Council (NHRC)

Source : http://www.myrepublica.com/portal/index.php?action=news_details&news_id=15949

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