EXTERNAL PARASITES
Horn flies, face flies, stable flies, ticks, lice and mites are the
major external parasites in beef cattle.
Horn Flies
are about half the size of house flies and are dark
gray. They are blood-sucking flies that stay on the shoulders and
backs of cattle almost continuously. During extremely hot weather
or when it rains, they may move to the protected underside of the animal. When
disturbed, horn flies will fly up in a swarm but they will return to
the animals almost immediately. A horn fly leaves the back of a
cow or calf only to lay eggs in fresh manure. They suck blood from
the host 24 hours a day. Individual flies pierce the skin with
their short, tube-like mouthparts 20 to 30 times per day to ingest a
small amount of blood. Their feeding activity is painful and annoys
the animals, as well as causing some blood loss.
There are many effective options to keep horn fly numbers below the
100 fly per animal treatment threshold. Cost, convenience, and
herd management practices, such as grazing rotation, can be considered
when designing a control program that fits best. Backrubbers allow cattle
to treat themselves while loafing and scratching. Dust bags are
most effective when used where cattle have to pass under them daily to
get to water or mineral. Feed additives target horn fly maggots
breeding in fresh animal manure. High pressure sprays can
be used to treat cattle thoroughly and inexpensively on a per head basis. An
insecticide bolus is a large pill-like formulation that is given to the
animal with a standard balling gun. Insecticide-impregnated
cattle ear tags release small amounts of an insecticide which are distributed
over the animal during grooming or rubbing. Pour on insecticides
are ready-to use formulations that are applied in measured doses to animals
based upon body weight.
Face Flies
closely resemble house flies. Face flies cluster
on the faces of cattle and feed on secretions from the mucus membranes
of the eyes, nose, and lips. Face flies do not suck blood. They do irritate
the surface of the eyeball and carry and spread bacteria and viruses
that contribute to pinkeye problems. They spend only a small portion
of their life on cattle which makes them more difficult to control than
horn flies.
Stable flies
are sometimes called biting house flies. The look
very much like house flies. They feed primarily on legs and lower
abdomen of cattle. The mouth parts penetrate the skin and allow
them to engorge on blood two to three times a day depending on the weather. Once
full they move to a resting place, usually in the shade, to digest the
blood meal. The blood loss and pain associated with the bite of
stable flies results in substantial economic loss.
Ticks
cause blood loss, discomfort, and spread diseases like
anaplasmosis. Tick control is extremely difficult in areas with
high tick populations. High concentrations of ticks usually occur in
brushy pastures and woodlands so habitat management is an important part
of tick control. Control on cattle through persistent use of approved
pesticides is achieved by spraying, dipping, ear tags, pour-ons, dust,
and backrubs. A good residual insecticide is
necessary to prevent infestation.
Lice
cause skin irritation and itching. Both biting and
sucking lice infest cattle. Infested cattle can experience
reduced appetite and appear unthrifty.
Lice reside entirely on the host cow. Lice are present on cattle year
around but increase in numbers in winter. In spring most parasites are lost
with the winter hair coat. Lice control is most important in the fall and early
winter when the lice populations increase. Treat with approved products.
Treatment needs to be repeated in three weeks to kill hatching lice since most
insecticides do not successfully kill eggs. Sprays and pour-ons are common
methods to treat cattle lice.
Mite
infestation is called mange in cattle. A serious form
of mange is called scabies. Scabies is caused by sarcoptic and psoroptic
mites and must be reported to the disease control authorities. A
less severe mange is caused by chorioptes, demodex, or psorergates mites. Mites
are spread through close contact. Cattle infested with mites
suffer hair loss and a thickening of the skin. Severe infestations
can weaken cattle and make them vulnerable to diseases. Scabies
can result in severely debilitated animal. Control of mites is difficult
because mites burrow into hide. Injectable products or pour-on
products with systemic activity work to control mites best. As
with lice, a second application is necessary in two to three weeks to
kill newly hatched mites.
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Information contained in this article from one or more of the following:
Alabama Cooperative Extension System
South Carolina Extension Service
Nebraska Extension Service
Oklahoma State Cooperative Extension Service
University of Nebraska Cooperative Extension
University of Minnesota Extension Service