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

6. African horse sickness virus
6.1. HAZARD IDENTIFICATION
6.1.1. Aetiological agent
Family: Reoviridae; Genus: Orbivirus, Species: African horse sickness virus (AHSV).
There are 9 serotypes of AHSV (Mertens et al 2005).
6.1.2. OIE list
Listed as a disease of equidae.
6.1.3. New Zealand status
Listed on the Unwanted Organisms Register as a notifiable organism.
6.1.4. Epidemiology
African horse sickness (AHS) is an infectious but noncontagious viral disease affecting all
species of equidae. Camels and dogs can also be infected. Humans are not natural hosts
and it is not a zoonotic disease.
The virus is transmitted by midges in the genus Culicoides with C. imicola and C. bolitinos
considered to be the principal vectors (Sanchez-Vizcaino 2008).
AHS is endemic in sub-Saharan central and east Africa and sometimes spreads to southern
Africa and occasionally to northern Africa and Mediterranean countries. Outbreaks have
occurred in Europe (Spain, 1966, 1987-1990 and Portugal, 1989) (Sanchez-Vizcaino
2008). The most serious infections occur in horses and mules. Zebras often do not show
clinical signs of infection and are considered to be the natural reservoir hosts in Africa
(Coetzer & Guthrie 2004; CFSPH 2006).
Dogs may become naturally infected by consuming contaminated horse meat but play no
role in the epidemiology of the disease (Coetzer & Guthrie 2004). Reports of infection in
camels appear to be uncommon and infection is not associated with clinical disease
(CFSPH 2006). Few details are available as to the level and duration of viremia in camels
and their role, if any, in the epidemiology of AHS (Guthrie 2008). The OIE ad hoc group
on Camelidae diseases considers that camelids could potentially act as carriers of the virus
(OIE 2009).
A Culicoides surveillance programme has been operating in New Zealand since 1991
(Ryan et al 1991). To date, seroconversion to arboviruses has not been detected in sentinel
cattle and no Culicoides have been trapped (Tana & Holder 2008).
AHS has not been associated with disease in camelids or camels. It is not known if any
Camelidae develop a viraemia sufficient to infect feeding Culicoides.
Imported camelids would not be able to infect other animals in New Zealand since the
virus can only be transmitted by vectors that are not present.
MAF Biosecurity New Zealand Import risk analysis: Llamas and alpacas from specified countries ● 17