Import risk analysis: Llamas (Lama glama) and alpacas (Vicugna ...

20. Bacillus anthracis
20.1. HAZARD IDENTIFICATION
20.1.1. Aetiological agent
Bacillus anthracis is an aerobic, spore-forming bacillus that causes the disease anthrax.
20.1.2. OIE list
Listed as a disease of multiple species.
20.1.3. New Zealand status
The last case of anthrax occurred in 1954 (Gill 1992). It is an unwanted, notifiable
organism (MAF 2009).
20.1.4. Epidemiology
Anthrax is a bacterial disease of most warm-blooded vertebrates including camelids. It is
primarily a natural disease of herbivores which are most susceptible, followed by humans
and pigs. Carnivores such as the dog and cat are resistant to infection (Langston 2005;
Coker 2008). The disease has occurred in recent years in many countries including
Australia, Canada, the EU, the USA and many South American countries (OIE 2009).
The infectious agent is a spore forming bacillus that can survive in the spore state in
suitable soils for many decades. In 1999 an outbreak occurred in Australia on farms where
the disease had not occurred for about 100 years. On these properties earthworks in
relation to an irrigation scheme possibly resulted in disturbance of old burial sites of cattle
(Turner et al 1999a; Turner et al 1999b).
Bacillus anthracis is probably an obligate pathogen that multiplies only in animals, and if
an infected carcass is opened, it sporulates resulting in contamination of soil and the
environment. In unopened carcasses the organism does not sporulate and is destroyed by
putrefaction (De Vos & Turnbull 2004). The disease is not directly transmissible from
animal to animal and infection is believed to be associated with ingestion of soil or other
infected material that is contaminated with spores. Biting flies may carry the infection but
they were not considered to be important in the transmission of the disease in an outbreak
in Australia (Turner et al 1999a). Blowflies may be important in the spread of the disease
when they have been feeding on infected carcasses (De Vos & Turnbull 2004). Infection
through skin wounds and abrasions may also occur and is a common route of infection for
humans (De Vos & Turnbull 2004). In some circumstances human infection can occur by
inhalation (so-called woolsorter's disease) but inhalation is not likely to be of importance in
camelids.
The incubation period probably ranges from 1-14 days. In the peracute form in susceptible
species, animals may die without showing signs. In other cases animals may die in 1-3
days after developing subcutaneous swellings on various parts of the body (Fowler 1998).
Efficient live spore vaccines are available for control of the disease. The vaccine strain
developed by Sterne (Sterne 1937) is used for most animals including camelids. It is a
rough strain that has lost plasmid pX02 which codes for the bacterial capsule. The vaccine
is non-pathogenic in most animal species and provides good immunity for about a year (De
MAF Biosecurity New Zealand Import risk analysis: Llamas and alpacas from specified countries ● 69