Agriculture Reference
In-Depth Information
swollen lymph glands at 6-8 weeks after
inoculation.
Murine typhus is a rickettsial disease
and one of the most widely distributed fl ea-
borne infections, endemic in many coastal
areas and ports throughout the world,
including parts of Europe and the USA.
X. cheopis is the main fl ea vector but other
species may also be involved. The classic
rat-fl ea-rat cycle seems to have been
replaced in some areas by a peridomestic
animal cycle involving feral cats, dogs,
opossums and their fl eas (Azad et al. , 1997).
Tungiasis is an infl ammatory skin con-
dition resulting from infection by the sand
fl ea, Tunga penetrans (also known as the
jigger, chigger or jigoe). The female fl ea
becomes permanently attached to the host,
typically on the foot, although infection
may also occur on the knees or hands. The
site of attachment typically becomes
infl amed and infected, sometimes resulting
in gangrene that may require amputation.
The fl ea is found primarily in South
America and Africa. Infection rates are
highest in low-income communities where
people walk barefoot, there is bare, friable
soil, and there is a free movement of
animals, such as dogs, pigs and so on, into
and between houses (Pampiglione et al. ,
2009).
known as genal and pronotal combs,
respectively. These help the fl ea move
through the fur or feathers of the host and
are useful in fl ea identifi cation. The head is
helmet-shaped, with the eyes often being
reduced or even absent. The labrum and
mandibles are sharp and are used to pierce
the host's skin, and the blood is pumped
into the fl ea's alimentary canal. Most fl ea
species have a preference for one host
species but many are able to take blood from
other hosts, particularly if they are hungry.
This fl exible feeding behaviour is important
for the transmission of diseases, such as
plague.
Those fl eas that typically live within the
host's nest tend to crawl rather than jump.
Those fl eas that tend to stay on the host
itself, however, have rear legs that are well
developed for jumping. Fleas can jump up
to 18 cm vertically and up to 33 cm
horizontally, with the energy generated by
compression and decompression of the
rubbery protein resilin at the base of the rear
legs.
Egg laying
The fertilized female fl ea starts to lay eggs
within about 2 days of an initial blood meal.
Each subsequent blood meal triggers the
laying of another batch of eggs, with up to
several hundred eggs being laid over the
fl ea's lifetime. The eggs are pearly-white,
oval, and are slightly sticky when laid and
may initially adhere to the host's fur,
plumage or clothing. They are, however,
easily dislodged and will fall to the ground,
often in or around the host's nest or sleeping
area.
Flea Biology and Behaviour
Fleas are small, wingless parasitic insects
that undergo complete metamorphosis
through egg, larva, pupa and adult stages.
The adults are typically 1.5-3.5 mm
long, with a few species reaching as much
as 8 mm in length. They are brown and
sometimes almost black in colour. Their
laterally fl attened body enables them to
crawl easily through the fur or plumage of
host animals. The fl ea body is heavily
sclerotized, making it quite tough and
resistant to mechanical pressure and
damage by the host animal. The body
appears quite polished and, in addition to
the usual setae, many fl ea species also have
a row of backward pointing spines under
the head and also on the back of the thorax,
Larvae
The larvae hatch from the eggs after 2-6
days, depending on temperature and
humidity. They are cylindrical in shape,
legless, pale-coloured and with a ring of
bristles on each segment. They reach about
5 mm in length when fully grown. The
larvae feed on organic debris but particularly
 
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