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

30. Yersinia pestis
30.1. HAZARD IDENTIFICATION
30.1.1. Aetiological agent
Yersinia pestis is the causative agent of plague and is a gram-negative bacterium.
30.1.2. OIE list
Not listed.
30.1.3. New Zealand status
The last case of plague in humans was reported in 1911. It is classified as an unwanted,
other exotic organism (MAF 2009) and yersiniosis is a Section A disease notifiable to the
Medical Officer of Health (MoH 2009).
30.1.4. Epidemiology
Plague, caused by Yersinia pestis, resulted in millions of human deaths in the middle ages.
Modern treatment and management of vermin has reduced the threat but the World Health
Organization still reports 1,000 to 3,000 cases of plague annually (CDC 2009). Plague is
primarily transmitted by fleas from rodent hosts, particularly rats and wild rodents such as
prairie dogs in the USA. It can also be transmitted by bites and scratches from infected
animals or by the respiratory route in cases of pneumonic plague. It is carried by a large
number of rodents and mammals and according to one reference about 200 species of
rodents had been proved to be naturally infected (Davis et al 1975). The disease in humans
presents as bubonic plague (lymph node infection at the site of infection), septicaemic or
respiratory infection.
The disease in camels has been reviewed (Wernery & Kaaden 2002). It is associated with
contact with infected rodents and transmission by fleas or mechanically by ticks of the
genera Hyalomma and Ornithodoros. The incubation period in camels is 1-6 days and
death occurs within 20 days. In a recent plague outbreak, deaths that occurred in
dromedary camels were associated with transmission by fleas from jirds (desert dwelling
rodents) living in the camel enclosure. The disease was transmitted to humans that ate raw
liver from a camel that had died of the infection (Bin Saeed et al 2005).
The OIE ad hoc group on Camelidae diseases does not list plague as a significant disease
of camelids. Only one reference was found relating to plague in a llama. This was a
personal communication only with no supporting information (Orloski 2003). Camelids are
not considered to be maintenance hosts for Y. pestis.
30.1.5. Hazard identification conclusion
Camelids are not recognised maintenance hosts for Y. pestis. Only one report was found of
the occurrence of plague in camelids and this was a second-hand report of a personal
communication. The disease in camels is an acute disease with death occurring within 20
days. Camelids that are not infested with fleas are unlikely to transmit the disease. Fleas
are not mentioned as significant parasites of camelids by the OIE ad hoc group on
112 ● Import risk analysis: Llamas and alpacas from specified countries MAF Biosecurity New Zealand