Evaluation of a rapid dipstick test for identifying cholera cases during the outbreak

Among the diarrhoeal diseases, cholera is one of the most significant causal elements in terms of severity of the disease and outcomes. Several epidemics of cholera have been reported from different parts of India and abroad1–8. Vibrio cholerae strains belonging to O1 and O139 serogroups are responsible to cause cholera in the form of epidemics and pandemics9,10. Despite the fact that the pathophysiology and transmission of cholera have been well understood and several advances have been made in modern health systems, cholera remains as a dreadful disease due to its rapid onset, severity to the extent of death, if left untreated, and potential to cause outbreaks that easily break through the public health systems in impoverished settings11,12. Outbreaks of cholera are related to limited access to safe drinking water and poor sanitation12,13. Earlier reports have pointed out the fact that high case fatalities in cholera outbreaks were due to inadequate use of oral rehydration therapy and in some cases inadequate experience in managing severe cholera by the health workers13. In a recent report, lack of clean water has been attributed for an exacerbation of cholera outbreaks in Haiti14. Strengthening of health services infrastructure in rural areas along with enhanced public education can significantly reduce cases fatalities15. Case fatality rates for untreated cholera cases can reach to 50 per cent, while implementation of good case management can reduce this figure below 1 per cent12,15. Outbreaks often start in fringes in very low number but without effective and efficient healthcare system it can become threat to wider communities. The reported cholera cases to WHO ranged from 178,000 to 237,000 with 4000-6300 deaths12. There are numerous evidences, which show that without having timely intervention, delayed diagnosis of cholera has turned handful of cases into large epidemics16–19. Therefore, prompt, rapid and sufficiently sensitive diagnosis of cholera is the key factors to prevent the disease from being an epidemic. Currently, cholera diagnosis relies on the microbiological identification of the pathogen V. cholerae from the diarrhoeal stool specimens followed by serological characterization into either O1 or O139 serogroups. Culture confirmed cholera case detection requires 2~ 3 days in a good laboratory set up with trained manpower. Therefore, rapid diagnostic tests consuming least time, requiring minimum laboratory infrastructure and technical skill, will be the best choice in diagnosing cholera, in an outbreak situation. These rapid tests are based on the chromatographic changes due to the presence of O1 and/or O139 antigens in the test specimen. Studies have already been carried out on the applicability of such rapid tests in cholera endemic areas like Madagascar and Bangladesh; the specificity of O1 and O139 dipsticks ranged between 84-100 per cent and the sensitivity ranged between 94.2-100 per cent20. National Institute of Cholera and Enteric Diseases (NICED), Kolkata, conducts diarrhoeal outbreak investigations, as and when required, in different parts of the country. This study was a part of an outbreak investigation carried out NICED, Kolkata, at Bholakpur, Secunderabad, India. This study also evaluated the potential of using rapid dipstick test to identify the aetiologic agent of the outbreak.