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

19. Anaplasma phagocytophilum
19.1. HAZARD IDENTIFICATION
19.1.1. Aetiological agent
Anaplasma phagocytophilum (synonym Ehrlichia phagocytophilum) is a gram-negative
bacterium that is an obligate intracellular blood parasite of neutrophils. It is very closely
related to Ehrlichia equi (Hulinska et al 2004) and may be the same species. Some authors
refer to a genogroup of similar species (Barlough et al 1997a; Barlough et al 1997b).
19.1.2. OIE list
Not listed.
19.1.3. New Zealand status
Ehrlichia spp. are listed as exotic unwanted organisms (MAF 2009).
19.1.4. Epidemiology
Re-organisation of the taxonomy of the organisms in the family Anaplasmataceae as a
result of new information on their genomic structure has resulted in significant changes in
their classification (Dumler et al 2001). The family now contains four genera, Ehrlichia,
Anaplasma, Neorickettsia, and Wolbachia. Changes to names and classification of the
organisms in this group have been ongoing for several years. Uilenberg has suggested that
classification of organisms based only on partial gene sequences may lead to
misclassification of some species (Uilenberg et al 2004). The recent name changes have
been summarised in an article on the internet (Anonymous undated). It has been suggested
that knowledge about the Ehrlichia spp. is inadequate and that many new species may be
found in the future. Attention has also been drawn to the problem of “perpetuation of many
doubtful species names” (Sumption & Scott 2004).
This section is restricted to Anaplasma phagocytophilum. The genus and species names
used in this chapter are those used by the authors of the articles referred to above.
A. phagocytophilum is the agent of tick-borne fever in animals and human granulocytic
ehrlichiosis (McQuiston et al 2003; Grzeszczuk et al 2004). It has a world-wide
distribution. In Europe the organism primarily affects young cattle and sheep and usually
runs a mild course and inapparent infections occur. In the USA it causes subclinical
infections in cattle and is the predominant cause of ehrlichiosis in horses (McQuiston et al
2003). Experimental infections with A. phagocytophilum in sheep and goats caused a nonfatal
disease (Gokce & Woldehiwet 1999a). Infections with A. phagocytophilum may make
animals more susceptible to concurrent infections with other organisms (Woldehiwet 1983;
Gokce & Woldehiwet 1999b). Infected animals may carry the infection for 2 years
(Woldehiwet 1983). In the USA the vectors are Ixodes scapularis and Ixodes spinipalpis,
while in Europe the main vector is Ixodes ricinus (Alberdi et al 1998; Telford et al 2002;
McQuiston et al 2003). A. phagocytophilum DNA was identified in Haemaphysalis
longicornis from Korea but the report does not confirm that the tick can transmit the
organism (Kim et al 2003). It has been suggested that although natural infection of several
genera of ticks by single species of Ehrlichia occurs, infected species of ticks may not
66 ● Import risk analysis: Llamas and alpacas from specified countries MAF Biosecurity New Zealand