Agriculture Reference
In-Depth Information
throughout the nasal passages (including into the head
sinuses), and after a period of development (about 6
months), they drop from the nostrils to the ground, where
they complete their development to the adult form.
Sheep keds (
Melophagus ovinus
) also primarily affect
sheep, but occasionally can be found on goats. Unlike most
insects, the female sheep ked gives birth to living larvae,
which are nourished within her body until they reach the
pupal stage, and then are expelled and glued to hairs. Adult
keds emerge from the pupa and commence to feed on
blood, which can damage the skin; thus buyers may down-
grade the skins.
and lay eggs. The eggs hatch, producing larvae, called seed
ticks. The seed tick moults twice, passing through a
nymphal stage before reaching maturity. A blood meal
must be taken before each moult can occur. They are clas-
sifi ed as one-, two-, or three-host ticks, depending on how
many times they drop off, moult, and seek a new animal.
A one-host tick remains on the animal from the seed-tick
stage to maturity. A two-host tick drops off the initial host
to moult from larva to nymph. The nymph seeks a second
animal for the fi nal blood meal before fi nal moult to adult.
The three-host tick drops to the ground for each moult,
after which a new host is sought. The bodies of hard ticks
are roughly oval, and the mouthparts protrude at the front.
The mouthparts help to identify them. One mouthpart
structure, the hypostome, anchors the tick to the host's skin
to facilitate blood feeding. The abdomen, fl attened top and
bottom, can expand to several times its original size as a
tick feeds. When fully engorged, females are many times
greater in size. The patterns of pigmentation on the scutum
of the tick also help with identifi cation.
Soft ticks differ from hard ticks in many respects.
They have a leathery outer skin rather than a hard cuticle,
and both males and females engorge when feeding on the
host. Their shapes vary among species and their mouth-
parts are located underneath the tick so it does not protrude
forward.
Lice and Mites
Lice and mites undergo incomplete metamorphosis. These
parasites are relatively permanent residents on the animal.
They thrive and reproduce during the cooler months (fall/
winter) of the year. Transmission from animal to animal is
by contact usually pronounced when crowding occurs.
Infestation (commonly called mange when mites are
involved) may be seen as intense irritation with the animal
scratching and chewing creating skin lesions that can lead
to bacterial infection.
There are two kinds of lice—anoplura (suckling lice)
and mallophaga (chewing lice). Suckling lice feed on
blood and can cause anemia. Chewing lice scurry around
feeding on organic debris leading to irritation, scratching,
and skin lesions.
Mites commonly found are follicle mites (
Demodex
caprae
), scabies mites (
Sarcoptes scabei
), psoroptic ear
mites (
Psoroptes cuniculi
), and chorioptic scab mites
(
Chorioptes bovis
).
The follicle mite causes nodules due to obstruction of
the hair follicle trapping the mites and producing swelling.
Nodules are usually seen on the face, neck, axillary region,
and udder. These nodules may rupture, and the exuded
mites can be transmitted to other animals.
Scabies mites burrow into the skin causing varying
degrees of dermatitis causing crusty lesions and hair loss,
usually around the muzzle, eyes, ears, inner thigh, brisket,
abdomen, axillary region, and scrotum. Psoroptic ear mites
cause crusty lesions and discharge from the external ear
canal. Chorioptic scab mites cause mange seen primarily
on the legs and feet. This is very common in goats.
Fleas
Fleas occasionally can be found on goats. There are two
kinds, the cat fl ea (
Ctenocephalides felis
) and the sticktight
fl ea (
Echidnophaga gallinacea
). The cat fl ea feeds on
blood and may cause anemia. The sticktight fl ea may cause
ulcers on the head and ears.
Ectoparasite Control
There are many insecticides/acaricides that can be used for
control when necessary. These are classifi ed as organo-
phosphates (coumaphos, diazinon, dichlorvos, famphur,
fenthion, malathion, etc.), carbamates (carbaryl and pro-
poxur), pyrethrins/synthetic pyrethroids (cypermethrin,
deltamethrin, fenvalerate, fl umethrin, permethrin, etc.),
macrocyclic lactones (avermectins and milbemycins),
formamidines (amitraz), chloronicotinyls (Imidacloprid),
Spinosyns (Spinosad) and insect growth regulators
(benzoylphenyl ureas, triazine/pyrimidine derivatives,
Difl ubenzuron, and fl ufenoxuron). The most common
methods of administration are dusts, sprays, pour-on prod-
ucts, and some oral products.
Seasonal occurrence such as fl ies and ticks in the warmer
seasons and lice and mites in the cooler seasons, should be
Ticks
Ticks undergo incomplete metamorphosis. They are blood
feeders and are subdivided into hard and soft ticks accord-
ing to structural characteristics. Adult hard ticks feed and
mate on the animal. Engorged females drop to the ground
