Cholera
Queensland Health Guidelines for Public Health Units
Revision History
| Version | Date | Changes |
|---|---|---|
| 1.0 | March 2015 | Initial guideline |
Cholera is quarantinable under the Commonwealth Quarantine Act (1908)
Refer to The Guidelines for the Management of Human Quarantine Disease in Australia - March 2004.
- Disclaimer
- Infectious Agent
- Notification Criteria
- Notification Procedure
- Reporting to NOCS
- Public Health Significance and Occurrence
- Clinical Features
- Reservoir
- Mode of Transmission
- Incubation Period
- Period of Communicability
- Susceptibility and Resistance
- Management
- Preventive Measures
- Feedback
- Summary
- References
Infectious Agent
The agent is toxigenic Vibrio cholerae serogroup O1 or O139.
V. cholerae O1 occurs in two major biotypes: classical and El Tor. Both include organisms of the Inaba and Ogawa serotypes.
For non-O1 or non-O139 Vibrio cholerae, or non-toxigenic strains of 01 or 0139 V. cholerae causing diarrhoea, refer to the protocol for "Food/waterborne illness in two or more related cases" in this manual. Reporting of these infections as 'cholera' is inaccurate.
Notification Criteria
Clinical evidence
An illness characterised by profuse watery diarrhoea ± vomiting, with little fever. There is usually with a history of recent travel to a cholera endemic area or an epidemiological link to a confirmed case of cholera. Most cases (75%) are asymptomatic but remain potentially infectious to others.
Laboratory definitive evidence
Isolation of toxigenic Vibrio cholerae O1 or O139
Community Outbreak Criteria
A single case represents an outbreak
Notification Procedure
Pathology Laboratories
To notify on microbiological confirmation of toxigenic strains of O1/O139 Vibrio cholerae, by telephone or facsimile.
Attending Medical Practitioners/Medical Superintendents (or delegates)
To notify on provisional clinical diagnosis, by telephone or facsimile.
The Public Health Unit should immediately notify cases of cholera to the Chief Quarantine Officer in Queensland.
WHO requires the first imported, non-imported or transferred case to be reported to WHO and adjacent countries - this reporting pathway is implemented by the Australian Government Department of Health and Ageing.
Reporting to NOCS
Report only confirmed cases.
Confirmed case
A confirmed case requires laboratory definitive evidence
Public Health Significance and Occurrence
Since 1817, there have been seven pandemics of cholera. The seventh pandemic is ongoing and is responsible for significant morbidity and mortality in developing countries. Asymptomatic or mild disease is common. Untreated severe cholera has a case-fatality rate which may exceed 50%. If properly treated with prompt aggressive fluid therapy this figure should be less than 1%.
Cholera is not endemic in Australia. There are only about six recorded cases a year, mostly imported from endemic areas. Since the commencement of the National Notifiable Diseases Surveillance System in 1991, all cases have been acquired outside Australia except for 1 case of laboratory-acquired cholera in 1996 and 3 cases in 2006. The 3 cases in 2006 were associated with the consumption of imported raw white bait. There are also rare sporadic occurrences in NSW and Queensland where the organism has become established in some river systems. The organism may be viable in low numbers in summer, but it would be unlikely that a person would consume an infective dose. The disease is closely linked with poor sanitation, so the risk of a large-scale outbreak is small in Australia due to appropriate sewage disposal and sanitation.
Clinical Features
Cholera is an acute diarrhoeal disease with variable severity. Mild illness and asymptomatic infection are common. Less than 20% of infected persons develop severe illness characterised by sudden, painless, profuse watery diarrhoea ("rice water" diarrhoea) often with vomiting, rapid dehydration, muscle cramps, acidosis and circulatory collapse. Death may result in 3-4 hours if the patient is not adequately rehydrated.
Reservoir
Humans
Water: brackish or estuarine waters where organisms may be associated with copepods (which are mainly minute freshwater and marine crustaceans) or other zooplankton.
Mode of Transmission
Infective dose required to cause illness is high so direct person-to-person transmission is unusual.
- Ingestion of water contaminated by bacteria from an infected person's faeces or vomitus
- Ingestion of food contaminated by dirty water, soiled hands or flies, eg. vegetables fertilised with sewage or night soil or washed in contaminated water
- Fish or shellfish (raw or poorly-cooked) obtained from contaminated waters
- The organism can survive for long periods in water and in ice
Incubation Period
From a few hours to 5 days, usually 2-3 days.
Period of Communicability
Faeces and vomitus are infectious during the acute stage and for a few days after recovery. By the end of the first week 70% of patients are non-infectious and by the end of the third week 98% are non-infectious. Chronic carriage is rare, but occasionally the carrier state may persist for months and, very rarely, chronic biliary infection is associated with intermittent shedding of organisms lasting years.
Antibiotics may shorten the period of communicability but are not recommended for treatment except in severe cases.
Susceptibility and Resistance
Even in severe epidemics attack rates of overt disease rarely exceed 2%. Gastric achlorhydria increases the risk of disease as does having blood group O. Breastfed infants are at reduced risk. Infection results in a rise in agglutinating vibriocidal and antitoxic antibodies with increased resistance to reinfection. Immunity due to previous infection is serogroup specific. Immunity after classic cholera probably lasts longer than immunity after El Tor cholera.
An initial clinical infection by V. cholerae 01 of the classical biotype confers protection against either classical or El Tor biotypes. In contrast, an initial clinical infection caused by biotype El Tor results in only a modest level of long-term protection that is limited to El Tor infections.
Management
Cases
Investigation
If possible, identify the serogroup of Vibrio cholerae.
In consultation with the attending medical practitioner, identify possible exposure, including time and place of travel, and return flight/ship.
Restriction
Exclude from work food handlers and carers of patients, children and the elderly in the stool-positive stage (usually only until a few days after recovery, i.e. until two consecutive negative stools are taken 24 hours apart). Persons with poor hygiene such as young children may require isolation during the infectious period.
Treatment
Prompt fluid replacement is the basis of the treatment of cholera. Anti-diarrhoeals e.g. loperamide should not be given. Antibiotic therapy reduces the volume and duration of diarrhoea and should only be used in severe cases and where rehydration has occurred and vomiting has stopped. Regimens are:
Azithromycin
- 1g (child: 20mg/kg up to 1g) orally, as a single dose
OR
Ciprofloxacin
- 1g (child: 25mg/kg up to 1g) orally as a single dose
Antibiotic resistant strains are now common in some regions. In the event of clinical failure treatment should be guided by in vitro susceptibility data.
Counselling
The case should be advised of the need to maintain hydration until diarrhoea has ceased, of the nature of the infection and its mode of transmission.
Educate about hygiene, in particular hand washing before eating / food preparation (cases should avoid preparing food for others), and after going to the toilet, and disinfection of contaminated clothes/linen/other articles.
Contacts
Contact Tracing
Yes.
Definition
Household members or those exposed to a possible common source.
Investigation
A stool culture from each household member and those exposed to a possible common source. All contacts should be under surveillance (for diarrhoea) for five days after the last exposure.
Prophylaxis
Vaccination is not indicated, nor is mass chemoprophylaxis. Chemoprophylaxis of household contacts may be required if there is evidence or high likelihood of secondary transmission within households.
Counselling
Encourage early referral if symptoms develop.
Educate about hygienic practices, in particular hand washing before preparing food, eating and after going to the toilet.
Other control measures
Identify Source
Ascertain whether or not the case was likely to have been exposed during travel to an endemic area.
If the source is thought to be within Australia, the actual or probable source of infection must be determined, for example by testing the water supply, and preventive measures undertaken.
Disinfection
Disinfection of linen and articles used by the patient.
Health Education
Populations at risk to be informed of the need for early referral and treatment if symptoms develop. Vaccination of overseas travellers is rarely indicated, as the infective dose is large and compliance with advice on safe food and drink offers a high degree of protection. The efficacy of the killed parental vaccine is poor, but newer oral vaccines offer a higher degree of protection and may be indicated in those at increased risk.
Community outbreaks/epidemics
An outbreak is unlikely to occur in Australia. Measures limiting the movement of people or goods are not warranted.
Preventive Measures
Education re:
- good hygiene practices
- safe food preparation
- appropriate waste disposal
Consider oral cholera vaccination for high-risk travellers, eg. humanitarian workers in refugee camps in endemic areas. Cholera vaccine is also recommended for travellers to endemic areas who are at risk of severe disease including those with HIV & AIDS, or other conditions of immunocompromise, achlorhydria, inflammatory bowel disease, complicated diabetes and significant cardiovascular disease.
Feedback
The relevant State Chief Quarantine Officer should be notified of a suspected or confirmed case of cholera
Report to notifying agency.
The Australian Government Department of Health and Ageing is required to notify the WHO.
Summary
Prepare a report of the investigation for the Communicable Diseases Unit, Queensland Health
References
eTG (2011) e-Therapeutic Guidelines - Vibrio cholera (cholera). https://online-tg-org-au.cknservices.dotsec.com/ip/desktop/index.htm : accessed 01/06/2014.
Forssman, B. et al. 2007 in Australia's Notifiable Disease Status, 2010: Annual report of the national Notifiable diseases surveillance system. NNDSS. http://www.health.gov.au/internet/main/publishing.nsf/content/cda-cdi3601-pdf-cnt.htm/$FILE/cdi3601a.pdf
Handa, S. 2014. Cholera treatment and management. Medscape. http://emedicine.medscape.com/article/962643-treatment#a1156
Heymann D. (Ed). 2015. Control of Communicable Diseases Manual, 20th edition. American Public Health Association: Washington.
Waldor, M.K., Ryan, E.T. 2012. Cholera and other Vibrioses in Harrisons online (chp 156) http://accessmedicine.mhmedical.com/content.aspx?bookid=331§ionid=40726906
National Health and Medical Research Council. 2013. The Australian Immunisation Handbook, (10th ed.). Australian Government Department of Health and Ageing: Canberra.
Nielsen, A.A., Mayer, C.A. (2010). Cholera: recommendations for prevention in travellers. Australian Family Physician, 39 (4), 222-225.
Public Health Laboratory Network. 2006. Cholera laboratory case definition (LCD). Australian Government Department of Health. http://www.health.gov.au/internet/main/publishing.nsf/Content/cda-phlncd-cholera.htm
World Health Organisation. 2010. Cholera Vaccines. Weekly Epidemiological Record. 13:117-128.
World Health Organisation. 2014. Cholera. http://www.who.int/topics/cholera/en/ :accessed 01/06/2014