Guidelines for the Surveillance and Control of Anthrax in Humans and Animals

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The WHO guidelines are at http://www.who.int/emc-

documents/zoonoses/whoemczdi986c.html

 

A little more about Pathogenesis and symptoms

 

Except when taken up by the pulmonary route, B. anthracis needs a

lesion through which to enter the body. Following entry, the spores,

which may have commenced germination, are carried to the lymphatics

where they multiply and, in terms used by workers in the 1950s,

continuously feed the blood stream with the vegetative bacilli in a

manner analogous to continuous culture. Initially, during the

incubation period, the bacteria are filtered out by the spleen and

other parts of the reticuloendothelial system. However, the system

finally breaks down due to toxin action and, during the last few

hours of life (fulminant systemic phase), the bacteria build up

rapidly in the blood (doubling time approximately 0.75 to 2 hours

depending on host species) to levels of >108/ml together with massive

toxaemia at the time of death. The action of the toxin on the

endothelial cell lining of the blood vessels results in their

breakdown, internal bleeding and the characteristic terminal

haemorrhage to the exterior which is an essential part of the

organism's cycle of infection (Figure 1 and front cover).

 

The incubation period in the susceptible herbivore ranges from about

36 to 72 hours and leads into the hyperacute systemic phase, usually

without easily discernible prior symptoms. The first signs of an

anthrax outbreak are one or more sudden deaths in the affected

livestock, although farmers may reflect retrospectively that the

animals had shown signs such as having been off their food or having

produced less milk than usual. During the systemic phase, the animals

become distressed, appear to have difficulty breathing and cease

eating and drinking. Swellings in the submandibular fossa may be

apparent; temperatures may remain normal for most of the period or

may rise. The animal can remain responsive to treatment well into

this period but if treatment fails it lapses into coma followed by

death from shock. In highly susceptible species, the period between

onset of visible symptoms and death may be just a few hours; the

course of these events is more protracted in more resistant species.