|WHO Recommended Surveillance Standards (WHO - OMS, 1999, 157 p.)|
RATIONALE FOR SURVEILLANCE
Anthrax is a widespread zoonosis transmitted from domestic animals (cattle, sheep, goats, buffaloes, pigs and other) to humans by direct contact or through animal products. Human anthrax is a serious problem in several countries and has potential for explosive outbreaks (especially the gastrointestinal form); while pulmonary (inhalation) anthrax is mainly occupational, the threat of biological warfare attacks should not be forgotten. Anthrax has a serious impact on the trade of animal products.
The control of anthrax is based on its prevention in livestock: programmes based only on prevention in humans are costly and likely to be ineffective except for those industrially exposed. There is an effective vaccine for those occupationally exposed, and successful vaccines for livestock, particularly for herds with ongoing exposure to contaminated soil. In most countries anthrax is a notifiable disease. Surveillance is important to monitor the control programmes and to detect outbreaks.
RECOMMENDED CASE DEFINITION
An illness with acute onset characterized by several clinical forms. These are:
(a) localized form:
· cutaneous: skin lesion evolving over 1 to 6 days from a papular through a vesicular stage, to a depressed black eschar invariably accompanied by oedema that may be mild to extensive
(b) systemic forms:
· gastro-intestinal: abdominal distress characterized by nausea, vomiting, anorexia and followed by fever
· pulmonary (inhalation): brief prodrome resembling acute viral respiratory illness, followed by rapid onset of hypoxia, dyspnoea and high temperature, with X-ray evidence of mediastinal widening
· meningeal: acute onset of high fever possibly with convulsions, loss of consciousness, meningeal signs and symptoms; commonly noted in all systemic infections
Laboratory criteria for diagnosis
Laboratory confirmation by one or more of the following:
· Isolation of Bacillus anthracis from a clinical specimen (e.g., blood, lesions, discharges)
· Demonstration of B. anthracis in a clinical specimen by microscopic examination of stained smears (vesicular fluid, blood, cerebrospinal fluid, pleural fluid, stools)
· Positive serology (ELISA, Western blot, toxin detection, chromatographic assay, fluorescent antibody test (FAT))
Note: It may not be possible to demonstrate B. anthracis in clinical specimens if the patient has been treated with antimicrobial agents.
Suspected: A case that is compatible with the clinical description and has an epidemiological link to confirmed or suspected animal cases or contaminated animal products.
Probable: A suspected case that has a positive reaction to allergic skin test (in non-vaccinated individuals).
Confirmed: A suspected case that is laboratory-confirmed.
RECOMMENDED TYPES OF SURVEILLANCE
Since the usual ratio of livestock cases to human cases is of the order of 10-20:1, it is ineffective to depend only on human case reports. Routine surveillance must be undertaken, especially in high-risk groups (slaughterhouse workers, shepherds, veterinarians, wool/hide workers), and unexplained sudden livestock deaths must be investigated. Immediate case-based reporting from peripheral level (health care providers or laboratory) to intermediate and central levels of public health sector and to the appropriate level of animal health sector is mandatory. All cases must be investigated.
Routine monthly reporting of aggregated data on confirmed cases and investigation reports from intermediate to central level in public health and animal health sectors.
RECOMMENDED MINIMUM DATA ELEMENTS
Case-based data for investigation and reporting
· Case classification by type (suspected/probable/confirmed), and by clinical form (cutaneous/gastro-intestinal/pulmonary (inhalation)/meningeal)
· Unique identifier, age, sex, geographical information, occupation
· Date of onset, date of reporting
· Exposure history
Aggregated data for reporting to central level
· Number of confirmed cases by age, sex, clinical form (cutaneous/gastro-intestinal/pulmonary (inhalation)/meningeal)
· Similarly for livestock by outbreaks and cases in relation to species and appropriate geographic/administrative area
RECOMMENDED DATA ANALYSES, PRESENTATION, REPORTS
Graphs: Number of suspected/probable/confirmed cases by date.
Tables: Number of suspected/probable/confirmed cases by date, age, sex, geographical area.
Maps: Number of human and animal cases by geographical area.
PRINCIPAL USES OF DATA FOR DECISION-MAKING
· Estimate the magnitude of the problem in humans and animals
· Monitor the distribution and spread of the disease in humans and animals
· Detect outbreaks in humans and animals
· Monitor and evaluate the impact of prevention activities in humans and of control measures in animals
· Identify populations at risk
· Identify potentially contaminated products of animal origin
· Identify potentially contaminated animal sources (herds or flocks)
The surveillance activities of both public health and animal health sectors must be fully coordinated and integrated. Administrative arrangements between the two sectors must be established to facilitate immediate cross-notification of cases/outbreaks, as well as joint case/outbreak investigations. Surveillance and control programmes should be promoted in high-risk areas, such as those with high pH/calcareous soils.
See Regional Communicable Disease contacts on section "Communicable disease contacts in Regional Offices".
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Communicable Diseases Surveillance and Response (CSR)
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