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

15. Louping-ill virus
15.1. HAZARD IDENTIFICATION
15.1.1. Aetiological identification
Family: Flaviviridae; Genus: Flavivirus; Species: Louping ill virus. British, Irish, Spanish
and Turkish subtypes are recognised (Thiel et al 2005).
The viruses causing tick-borne encephalitis (TBE) are a closely related group of viruses
including the agents of Louping-ill, Central European TBE, Far Eastern TBE, Omsk
haemorrhagic fever in Siberia, Kyasanur Forest disease in the Indian subcontinent, Langat
in Malaysia, Negishi in Japan, Powassan in North America and parts of Russia, and four
viruses from Asia that have no known veterinary or medical significance (Gresikova &
Beran 1981; Korenberg & Kovalevskii 1999; Gilbert et al 2000).
15.1.2. OIE list
Not listed.
15.1.3. New Zealand status
Listed as an unwanted organism (MAF 2009).
15.1.4. Epidemiology
Louping-ill is a tick-borne disease that occurs in the United Kingdom. Closely related
viruses cause tick-borne encephalitis in various parts of Europe and the USA (Powassan
virus).
Louping-ill in the United Kingdom is primarily a disease of sheep but other species can be
infected. It has been suggested that at least 32 vertebrate species and a wide variety of ticks
can be infected with louping-ill virus (Reid 1990). The TBE viruses that occur in Eastern
Europe and Russia are primarily pathogens of humans. In Russia, 11,000 cases occur
annually and another 3,000 cases occur in the rest of Europe (Gritsun et al 2003a).
In animals, transmission of TBE viruses is entirely by ticks (Gresikova & Beran 1981).
The main tick vectors are Ixodes ricinius and Ixodes persulcatus, although other tick
species may also be involved (Gresikova & Beran 1981; Korenberg & Kovalevskii 1999).
Antibody has been demonstrated in, or virus has been isolated from, a wide range of
animals including small rodents, wildlife, and domestic animals such as deer and cattle
(Swanepoel & Laurenson 2004). TBE viruses of Russia and Eastern Europe are believed to
be sustained mainly in a tick/small mammal cycle, although transovarial transmission
through multiple generations of ticks also occurs (Gresikova & Beran 1981). In the case of
louping-ill, small mammals are probably of lesser importance in maintaining the virus
(Gilbert et al 2000). In sheep, louping-ill has an incubation period of 2-5 days. In
experimental infection of sheep and goats viraemia lasts 1-5 days and shedding of virus in
milk 2-7 days (Gresikova & Beran 1981).
The disease has been described in camelids in the United Kingdom (Macaldowie et al
2005; Cranwell et al 2008). Detailed studies in this species have not been carried out and
information must be extrapolated from data from sheep.
MAF Biosecurity New Zealand Import risk analysis: Llamas and alpacas from specified countries ● 51