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

The larvae reach maturity about 4-8 days after hatching from the egg and leave the wound,
falling to the ground into which they burrow and pupate. Adult flies emerge from the
pupae in 1 week (at 28�C) to 2 months time dependent on temperature and humidity (Acha
& Szyfres 1987; Ausvetplan 1996). Freezing or sustained soil temperatures of 8°C or less
kill the pupae (Merck 2006). The optimal temperature range for the fly is 20-30�C and this
has had a major influence on their distribution. Flies will not move at temperatures below
10�C, and in the range 10-16�C they are very sluggish and probably will not mate. At no
stage in the fly's lifecycle is it resistant to freezing and over-wintering in frost areas does
not occur (Ausvetplan 1996).
The NWS fly is endemic in parts of Central and South America as far south as Argentina.
It has been eliminated from the USA, Mexico and several Central American countries,
where it was previously endemic, by use of the sterile insect technique. NWS has never
established in Australia.
Dermatobia hominis, the tropical warble fly, lives in humid forested areas and is one of the
most important parasites of cattle in Latin America, where it is distributed between
southern Mexico and northern Argentina (Acha & Szyfres 1987). Larval stages are found
in many hosts, including humans (Soulsby 1968). The adult fly fastens its eggs to different
types of insects of which 49 (mostly mosquitoes and muscoid flies) have been described as
vectors of D. hominis in Latin America. These vectors then transport the eggs to warmblooded
hosts where they hatch as the insect vector feeds. The warble fly larvae penetrate
the skin of the animal within a few minutes of hatching and remain in the subcutaneous
tissue for 4-18 weeks (Acha & Szyfres 1987) where they form ‘warbles’ which are
connected by breathing holes through the skin to the air. When mature, the larvae leave the
host and drop to the ground, burrow, and pupate (Soulsby 1968).
The gray flesh fly, Wohlfahrtia vigil causes cutaneous myiasis in North America. Larval
stages are maggot-like in appearance and are adapted to maintain an attachment to living
tissues with strongly developed oral hooks. Wohlfahrtia vigil is larviparous i.e. it deposits
larvae (not eggs) on healthy, uninjured skin of suitable hosts. Larvae penetrate the
unbroken skin and form a boil-like swelling. Development to the infective third-larval
stage is usually completed in 9-14 days. The parasites then drop to the ground and pupate,
approximately 11-18 days later, depending on temperature.
W. magnifica occurs in the European and African Mediterranean area, the Middle East,
Russia and China. The fly is attracted to open wounds and, being larviparous, deposits
larvae in these wounds. It is an important disease of sheep in southern parts of Russia
(Acha & Szyfres 1987).
The following larval dipterans are often referred to as facultative myiasis-producing flies:
Musca domestica (the house flies), Calliphora, Phaenicia, Lucilia, and Phormia spp. (the
blowflies or bottleflies) and Sarcophaga spp. (the flesh flies). Their adult stages are
synanthropic flies, i.e. they are often associated with human dwellings and readily fly from
faeces to food. Larval stages are usually associated with skin wounds of any animal that
has become contaminated with bacteria or with a matted hair coat contaminated with
faeces. In facultative myiasis, the adult flies are attracted to a moist wound, skin lesion, or
soiled hair coat. As adult female flies feed in these sites, they lay eggs. The eggs hatch,
MAF Biosecurity New Zealand Import risk analysis: Llamas and alpacas from specified countries ● 143