Agriculture Reference
In-Depth Information
Nose Bots
The nose bot,
Oestrus ovis,
is a mature fl y that is dark gray and about the size
of a bee. Both the mature fl y and the larvae can cause problems for sheep.
The full-grown larvae are thick, yellowish white grubs with dark transverse
bands and are about 1 inch (2.5 cm) long. These pests are found primarily
in the frontal sinuses of sheep. When deposited by a fl y on the edges of the
nostrils, the grubs are less than
1
⁄
12
of an inch (0.2 cm) long. They cause irri-
tation as they crawl through the nostrils and sinuses and gradually move up
the nasal passages. The resulting infl ammation causes a thin secretion that
becomes quite thick if infection occurs. These thickened secretions can make
it diffi cult for a sheep to breathe, and it may sneeze frequently. The sheep can
become run-down because of its lack of appetite or from the stress of being
so annoyed by fl ies that it cannot graze in peace.
Sheep put their heads to the ground, stamp, and suddenly run with their
heads down to avoid this fl y. They often become frantic and press their noses
to the ground or against other sheep as the fl ies attack them. This usually
happens during the heat of the day, letting up in early morning and late in the
afternoon, and is more prevalent in areas with a hot summer.
Scab Mites
Several kinds of parasitic mites produce scab in sheep.
Psoroptes ovis
is the
common scab mite. This mite is a pearl gray color and about
1
⁄
40
of an inch
(0.06 cm) long, with four pairs of brownish legs and sharp, pointed, brownish
mouthparts.
Mites puncture the skin and live on the blood that oozes from the wounds.
The skin becomes infl amed and then scabs over with a gray, scaly crust. The
wool falls out, leaving large bare areas.
To determine whether mites are present, scrape the outer edge of one
of the scabs (mites seek the healthy skin at the edge of a lesion) and put the
scrapings on a piece of black paper. In a warm room under bright light, exam-
ine the paper with a magnifying glass. The mites become more active when
warm and can be seen with the glass.
The common scab mite, often called “mange mite,” is still a reportable dis-
ease in most states but has been all but eradicated in sheep. However, if mites
are found, all sheep must be treated in one session because mites are quite
contagious. Clean sheep should not enter infected premises for 30 days.
