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Cholera Testing

Has any one compared the effectiveness and practicality of Cholera testing field equipment?

Before everyone used the Delagua kit, now we are looking to use Coli alert, or Colitest. Has any one used these kits and how easy are they to read, and use in the field?

The early discovery of Cholera, in the field can save thousands getting sick.

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The Delagua kit tests for faecal coliforms http://www.delagua.org/products/categories/delagua-kits which will indicate if there has been faecal contamination – it will not tell you if there is or isn’t cholera or other of the various nasties in the water. I am unsure about the other kits mentioned but I would not hold my breath that they did anything more in this regard.

Testing for cholera specifically I believe has to be done in a laboratory. It is politically sensitive as major outbreaks are notifiable under the International Health Regulations with all sorts of implications: governments do not like confirming it and hence the use of Acute Watery Diarrhoea as a “politically acceptable” term for it.

In Goma at least, the cholera swept in but so did dysentery; from rumours to frightening numbers of dead bodies was a matter of days – I doubt anyone knows how many were killed by each – but I would suggest that there is sometimes too much focus on cholera. The explosive mixture is people crammed together in a weakened state without sanitation and safe water.

My feeling is that important as testing is, it is more important (and quicker?) to look at the risk factors and take informed action so far as possible on crowding, sanitation and water. I would focus hygiene promotion on helping people adapt to their new conditions and risks – many will have lived in slums before but have been more presentable and a whole lot cleaner than the average aid worker, so beware preaching!

Regards

Tim Foster

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I did some research through various texts including the Red Cross / John Hopkins Manual on environmental Health. As far as I can see there does not seem a conclusive test for cholera, there are tests as Toby says for various contributors such as faecal coliforms, and for indicators of these (e-coli etc).

From the various texts looked at today I cannot identify a specific conclusive "test" for cholera .... it seems more a case of an experienced medical practitioner identifying the cholera from the various surrounding conditions causing risk, and an observation of the various symptoms exhibited by patients ... which might individually also be shared by other conditions

Regards

Chris Nixon

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Question from Gino to Jane:

I recall, (but would be grateful if you could confirm or correct me on this) that confirming the positive presence of Cholera (as opposed to some other type of faecal coliform) is quite a complicated test and requires some fairly sophisticated laboratory equipment.

Jane: can you tell me more about what tests need to be done to confirm the presence of Cholera? Assuming that this is what Paul wants. Are there any kits that can be used in the field to test for Cholera? Are you familiar with “Coli alert” and “Colitest” mentioned in Paul’s e-mail below?

I am not sure how familiar you are with the Del Agua kit but I understand that, at least the older (basic) single incubator model “checks for” the presence of thermotolerant (faecal) coliforms by “growing” these coliforms (at 44 deg C). The particular coliforms grown during the use of this equipment were selected (because of their hardy nature) really as an indicator of the possible presence of other possibly more harmful faecal organisms.

Although I believe that the Del Agua kit is not capable of giving a positive confirmation of Cholera (as opposed to some other gastroenteritis disease), the kit is a valuable tool in checking water samples for the presence of other faecal coliforms which can indicate the possible presence of the Cholera causing bacteria.

I have no personal knowledge or experience of Haiti, but I would suggest that in any situation where sanitation is poor or non-existent and where people are living densely packed together, appropriate precautions to reduce the chances of a Cholera outbreak occurring should be taken as soon as possible. Measures could include chlorinating the water supply to disinfect it. At the risk of stating the obvious, don’t wait for the presence of Cholera to be confirmed, chlorinate the water supplies as soon as possible.

Answer from Jane: Good to hear from you, and I agree totally that the most important issue is to look for coliforms as a marker of faecal contamination rather than spending time and resources on searching out cholera in the environment. The ecology of cholera is complex and I believe detection in the environment is difficult. Easier would be detecting it in fresh stool of symptomatic people (i.e. those with profuse diarrhoea) - you can see the little buggers whizzing around under the microscope. The other issue is that there is a range of pathogens that can cause severe cholera-like watery diarrhoea and it seems to me that detecting cholera or not detecting it is of little value in relief conditions... although I have a vague recollection that funding/resources might be more forthcoming in a cholera outbreak??? (You'd know more about this than me, Gino).

Regards

Gino Henry and Jane Wilson-Howarth

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The contacts I have are in the University of Bristol, where professor Stephen Gundry is developing a 24 hour water testing kit (based on a numerical relationship of faecal coliforms to volume). The kit is about to be rolled out into a testing programme, which I have tried to integrate into an upcoming MM project in Tanzania. I'm not sure if there are any immediate linkages other than it's a bit of kit people have been waiting a long time for and would be very useful in the field for water engineers and emergency relief planners.

http://www.bristol.ac.uk/aquatest/

Regards

Oliver Hawes

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CDC and UNICEF mention the Crystal VC® dipstick rapid test and WHO says it "is currently in the process of validating" this new rapid diagnostic test (RDT).

Quote from CDC - http://www.cdc.gov/cholera/diagnosis.html:

In areas with limited to no laboratory testing, the Crystal VC® dipstick rapid test can provide an early warning to public health officials that an outbreak of cholera is occurring. However, the sensitivity and specificity of this test is not optimal. Therefore, it is recommended that fecal specimens that test positive for V. cholerae O1 and/or O139 by the Crystal VC® dipstick be confirmed using traditional culture-based methods suitable for the isolation and identification of V. cholerae.

Quote from the UNICEF Cholera Toolkit 2013 - http://www.unicef.org/cholera/Cholera-Toolkit-2013.pdf

Rapid diagnostic tests (RDT)

A rapid diagnostic test (RDT) provides important complementary information that, when combined with clinical and epidemiologic information, can further support or oppose the suspicions that an outbreak is due to cholera, especially when awaiting confirmation from stool cultures. RDT’s for cholera do not require an equipped laboratory, and they can be performed in field conditions or in any clinic. However, they are not 100% specific, and provide no isolates for antimicrobial susceptibility testing, serotyping, toxin testing or molecular subtyping.

The Crystal VCR RDT for V. cholerae O1 and O139 can provide results in about 10 minutes. It can be used to detect outbreaks early in their course, if procured and distributed to all levels of the national health system. It is relatively inexpensive (approximately $2 per test) and easy to use (even by those with limited technical skills) with appropriate instructions.

However, RDTs are not particularly useful for making the diagnosis of cholera in a single patient. The greater the number of patients tested, the more confidence one can have in the results of the RDTs, which will either show a majority of cholera-positive or a majority of cholera- negative results.

For example, using the Crystal VCR RDT for a cluster of cases:

• If the cause of their disease is cholera, the test will be positive in about 8 or 9 of the ten tests (sensitivity = 80-90%). • If the cluster of cases is due to another disease, the RDT will be negative in most instances (at least 6 out of 10, and probably more) (specificity > 60%).

Because of its potential usefulness, the Crystal VC RDT and locally adapted instructions or guidelines for its appropriate use should probably be part of the supply package distributed in advance of an outbreak in areas where outbreaks are predictable occurrences.

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Asked:
2013-12-09 04:06:04 -0600
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Last updated:
Dec 09 '13