Agriculture Reference
In-Depth Information
There is no major concern, but growth of kids (not adults)
may be somewhat reduced and intestinal blockage may
rarely occur. Infection can be controlled with albendazole,
fenbendazole, or oxfendazole.
diagnosis is by using the Baermann procedure (Urquhart
et al., 1996), which extracts the larvae from feces. Infection
can be controlled with albendazole, fenbendazole, iver-
mectin, or oxfendazole. There are two other minor lung-
worms (
Muellerius capillaris
and
Protostrongylus
spp.)
whose life cycles are indirect requiring land snails/slugs as
intermediate hosts. Control is not as easy and fortunately
pathology is minor.
Liver Fluke (
Fasciola hepatica
)
Adult liver fl ukes reside in the bile ducts of the liver. The
life cycle is indirect requiring an amphibious snail as an
intermediate host. Eggs are passed in the feces and a larval
stage called a miracidium develops inside the egg. After
hatching, the miracidium infects a snail. Asexual reproduc-
tion occurs in the snail, and then the next immature larval
stage called a cercaria leaves the snail and attaches to
forage where it develops into a metacercaria. Animals
ingest the metacercaria when grazing. The developing
immature fl uke migrates through the liver where damage
results in unthriftiness, weight loss/reduced gains, and
sometimes death. Infection can be a major problem in low-
lying perennial wet areas. Snails are active mainly in the
spring depending on environmental conditions, providing
the source of infection (transmission). Snails burrow into
the mud and become dormant the rest of the year, espe-
cially the hot summer months. Development of the adult
fl uke takes about 6-8 weeks. Because transmission ceases
in late spring/early summer, treatment to control fl ukes can
be divided into two periods—one period when immature
and adult fl ukes are present (spring/early summer) and
another when adults only are present (fall). Diagnosis is
by using a sedimentation procedure to fi nd eggs in feces.
Clorsulon (Curatrem) is the only product that is effective
against immature fl ukes. Clorsulon and albendazole are
effective against adult fl ukes. Therefore, selection of either
of these depends on the time of year. Another liver fl uke,
the deer fl uke (Fascioloides magna), can kill goats by
destroying the liver. Infection is rare but should be consid-
ered where deer have access to pastures. Control is
diffi cult.
Meningeal worm (
Parelaphostrongylus tenuis
)
The meningeal worm, also known as the deer worm or
meningeal deer worm, frequently infects llamas, alpacas,
and sometimes goats. White-tailed deer are the natural
host, so goats are at potential risk everywhere that white-
tailed deer are found. Small ground dwelling slugs and
snails are intermediate hosts. Goats, which are not normal
hosts, can ingest the slugs/snails that harbor the infective
form, and the larvae migrate into places where they don't
normally reside in the deer. Migration is up the spinal
nerves to the spinal cord, but then they seem to get lost,
and the larvae can migrate to the brain. This causes damage
to the central nervous system, which may be severe enough
to result in death. Animals acquire infection in the spring/
summer, but disease is usually seen in the fall/winter about
3-4 months after infection. Infected animals will show a
wide variety of symptoms, which may include rear leg
weakness and ataxia, paralysis, hypermetria, circling,
abnormal head position, blindness, and gradual weight
loss. Generally, animals with more severe symptoms have
a worse prognosis.
Diagnosis is diffi cult in the live animal and is usually
made when animals die and the larvae are found on exam-
ining the spinal cord and brain microscopically. The use
of ivermectin at monthly intervals during the transmission
season has been used in attempts to prevent infection, but
this strategy has not been proven. However, this frequent
administration interval most likely will have an effect on
the development of resistance by the other resident worms.
Lungworms (
Dictyocaulus fi laria,
Muellerius, Protostrongylus
)
Adult lungworms live in the bronchi or tissue of lungs. The
life cycle is direct with larva (not eggs) being passed in the
feces where they develop to infective larvae. Grazing
animals ingest the infective larvae, and after extensive
migration through the body, they reach the lungs and
mature to adults. Infection results in respiratory distress
(chronic coughing), unthriftiness, and sometimes death.
Problems with lungworm infection occur sporadically in
the U.S. with transmission during the cooler months (fall/
winter) of the year. Because larvae are found in feces,
Coccidia (
Eimeria
spp.)
Coccidia are protozoan parasites that infect cells in the
small intestine. Mature oocysts are passed in the feces and
develop into infective stages (sporocysts) within the
oocyst. Upon ingestion, infective stages break out of the
oocysts and invade intestinal cells where they undergo
asexual reproduction producing many more invasive
stages. This can occur repeatedly, and eventually sexual
reproduction occurs forming oocysts to complete the cycle.
Infection results in damage to the intestinal lining, which
can be permanent with reduced nutrient absorption capac-
