Transcript External Parasites - Dr. Brahmbhatt's Class Handouts

External Parasites
External Parasites
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Arthropod pests limit production in cattle industry
by affecting animals in many ways.
External parasites are the most serious threat
since they feed on body tissues such as blood,
skin and hair.
The wounds and skin irritation produced by
these parasites often result in discomfort and
irritation for the animal.
More significant, however, is that any bloodsucking arthropod may transmit diseases from
infected animals to healthy ones.
External parasites such as lice, flies, ticks,
cattle grubs and mites are a serious
problem to livestock breeders.
 These pests are most prevalent during
spring and summer months; however,
southeast Texas's warm climate permits
many pests to live year-round.
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Flies
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Flies are characterized by
having one pair of wings.
They have complete
metamorphosis with egg,
larva, pupa and adult
stages in their life history.
About 20 families of flies
are of veterinary
importance
House Fly
CREDITS: J. F. Butler, University of Florida
Comparison of the horn fly to the stable fly, house fly, and
face fly. Photo: Photo: John B. Campbell, University of
Nebraska-Lincoln
Horn Fly
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The horn fly is one of the most
serious pests of cattle in
Texas. It causes pain,
annoyance and interference
with feeding, resting and other
normal activities.
The fly pierces the skin to
blood feed and is a persistent
biter.
With high summertime
populations, they cause cattle
to lose weight and lower milk
production.
Horn flies may cause open
sores on the head and
underline, which can
predispose the animals to
secondary infection.
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Horn fly: greatest economic
loss in US cattle
Horn fly
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Eggs are laid exclusively in
fresh (within 10 minutes of
dropping) cattle manure.
Larvae hatch in about 18 hours
and feed on the dung, passing
through 3 stages in 3 to 5
days.
The pupal stage lasts 3 to 5
days, and the adults which
emerge have a preoviposition
period of 3 days.
Mating takes place on the host,
and females can lay about 200
eggs in their lifetime. The life
cycle from egg to adult takes
about 10 to 14 days
Horse and Deer Flies
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Horse flies and deer flies , also
called Tabanids, are insects
that are usually strong fliers.
As with mosquitoes, only
females bite.
They are usually daytime
feeders and are vicious biters.
Because of their painful bites
and frequent attacks, horse
flies produce frenzied behavior
in their hosts, sometimes
causing them to run long
distances in an effort to
escape.
Tabanids
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Tabanids introduce an anticoagulant into the
wound when they bite that causes blood to ooze.
These wounds are excellent sites for secondary
invasion of other insects and diseases, and also
cause more blood loss.
Being intermittent feeders, they can be important
mechanical transmitters of diseases such as
anthrax, tularemia and anaplasmosis.
Stable Flies
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Bite wounds also can serve as
sites for secondary infection.
These flies are easily
interrupted in feeding and are
mechanical transmitters of
anthrax and anaplasmosis
The stable fly, or dog fly, is
similar to the house fly in size
and color, but the bayonet-like
mouthparts of the stable fly
differentiate it from the house
fly.
Unlike the flies previously
discussed, both sexes of the
stable fly are vicious biters.
Stable flies cause irritation and
weakness in animals and
account for much blood loss in
severe cases.
Non-Blood Sucking Flies
Cattle Grubs
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Two species of cattle grubs are
found in the United States, the
common cattle grub and the
northern cattle grub.
The common cattle grub lays
its eggs chiefly on the hair of
cattle, attaching 5 to 15 eggs
to a single hair
Eggs hatch within about 4
days, and the maggots burrow
through the skin.
Migration of the first stage
larvae of the common cattle
grub is through connective
tissue, assisted by enzyme
secretion.
Cattle Grubs
The larvae produce two types of injury.
--First there is irritation caused by larval migrations
in the body of the host and later by emergence
from beneath the skin.
--Second, the escape of the larva from the warble
leaves an open, running wound that is persistent
and subject to secondary infection
The grubs must be killed before they reach the
gullet or spinal cord, because killing grubs in
these areas can cause swelling, and paralysis or
death
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Infestations of Fly Maggots
(Myiasis)
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Myiasis is the presence of
fly larvae in the living
tissue of the host.
Several kinds of maggots
infest the wounds of
warm-blooded animals;
however, the only one
that feeds exclusively on
live flesh is the primary
screwworm
Lice
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Most lice are permanent ectoparasites, spending their entire lives on
the host. Both immature and adult stages are parasitic; therefore,
they must remain on their hosts to survive.
Sucking lice are found on the head, neck and brisket during winter to
early spring
Lice are generally transmitted from one animal to another by
contact.
Transmission from herd to herd is usually accomplished by
introduction of carrier animals
Mites
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Mange mites (Psoroptes (most
damaging), Sarcopte, and
Chorioptes) feed on the
surface or burrow just beneath
the skin, making very slender,
winding tunnels
The fluid discharged at the
tunnel openings dries to form
nodules. A toxin is also
secreted which causes intense
irritation and itching
The infection may spread over
the entire body, forming large,
cracked scabs on the
thickened skin
Mange lesions
Mosquitoes
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Mosquitoes are small insects
with piercing-sucking
mouthparts, and scales on
their wings.
Female mosquitoes suck blood
but do not always need blood
to lay the first batch of eggs.
Several species of mosquitoes
attack livestock causing painful
bites, unthriftiness, and
occasionally death by
suffocation or heavy blood loss
Ticks
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Ticks are easily distinguished from insects, since the body is not
definitely divided and the strong fusion of the thorax and abdomen
produces a sac-like, leathery appearance. They belong to the class
Arachnida
A distinct head is lacking, but there is a head-like structure which
bears recurved teeth that are inserted into the wound, allowing the
tick to hold on strongly.
Females can be greatly distended and are bean-like in form when
fully engorged. Ticks have 4 developmental stages: egg, 6-legged
seed or larval stage, 8-legged nymphal stage and 8-legged adult.
Ticks
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The effects of ticks upon the
host include inflammation,
itching and swelling at the bite
site, blood loss, production of
wounds that may serve as
sites for secondary invasion,
obstruction of body openings
and paralysis from the injection
of toxic fluids.
They also transmit many
diseases, including
anaplasmosis, bovine
piroplasmosis and tularemia.
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The cattle tick, Boophilus microplus, is a significant
ectoparasite of cattle and a vector for important diseases
such as babesiosis and anaplasmosis.
B. microplus requires high humidity and ambient
temperatures of at least 15-20o C for egg laying and
hatching.
Differentiate from
 Haemophysalis spp
 Ixodes holocyclus
Keys To Pesticide Safety
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Before using any pesticide, stop and read the
precautions.
Read the label on each pesticide container before each
use. heed all warnings and precautions.
Store all pesticides in their original containers away from
food or feed.
Keep pesticides out of the reach of children, pets and
livestock.
Apply pesticides only as directed.
Dispose of empty containers promptly and safely.
Hemolytic System
Diseases
Babesiosis (Redwater fever)
This parasitic disease is usually first
reported in May/June when its tick host
first becomes active.
What is Babesiosis?
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Babesiosis is an infection of the red blood cells
by a single cell parasite of the genus Babesia
Two important species in cattle— B bigemina
and B bovis
The disease is spread between cattle by ticks
The babesia is injected into the bloodstream by
the tick and then invades the red blood cells and
begins dividing, eventually rupturing the cell.
Clinical signs begin around 2 weeks after
infection.
Boophilus annulatus: Vector for
Babesia bigemina
Boophillus microplus: Vector for
Babesia bovis
Clinical Signs
Increased temperature
 Diarrhea which ceases after around 36
hours and then becomes constipation
 Red urine (due to haemoglobin produced
by the rupture of the red blood cells) which
becomes darker with time
 Increased pulse rate
 Abortion of pregnant cows
 Death.
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Diagnosis
On the clinical signs described above
 Recent movement to pastures known to
harbour ticks
 Blood smears can show up the parasite
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Babesia in blood smear
Treatment
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Tetracyclines are the
drug of choice for
treating
Cattle dip for
Babesia control
Prevention
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Identification of risk areas
Prophylactic treatment of cattle about to
be moved to a risk area
Tick control
Vaccine not yet available
Anaplasmosis
Anaplasma marginale
Anaplasmosis is a vector-borne
infectious, hemolytic, rickettsial
disease of cattle, sheep, goats, and other
wild ruminants.
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Young calves seem to have an innate
resistance to the disease while the acute
form generally occurs in cattle from 1 to 3
years.
In cattle over 3 years, the peracute or most
severe form, with rapid onset and death,
predominates.
Animals that survive anaplasmosis can
become carriers for life and act as a reservoir
of infection for susceptible animals.
-The disease commonly occurs during the
warm months when arthropod vectors, both
biological and mechanical are abundant.
-Ticks are the most important biological
vector
Biological transmission can occur with other
vectors such as blood sucking flies (horse
and stable flies) and mosquitoes.
Accordingly, humans can be a mechanical
vector by using anaplasma-contaminated
equipment such as scalpels, needles, and
tatoo equipment on susceptible animals
Symptoms
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Anaplasmosis is characterized by progressive
anemia due to extravascular destruction of
infected and uninfected erythrocytes
Animals with peracute infections succumb within
a few hours of the onset of clinical signs. Acutely
infected animals lose condition rapidly
The urine may be brown but, in contrast to
babesiosis, hemoglobinuria does not occur
Bos indicus breeds of cattle appear to possess a
greater resistance to A marginale infection than
B taurus breeds
Diagnosis
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Anaplasma marginale infection in bovine blood, WrightGiemsa, 100X oil immersion. Intracellular organisms
appear as basophilic, spherical inclusions that are
generally located near the margin of erythrocytes.
Frequent echinocytes are present. The hemat Courtesy
of Dr. John W. Harvey
Treatment:
Tetracycline antibiotics and imidocarb are
currently used for treatment.
 Prompt administration of tetracycline drugs
(tetracycline, chlortetracycline,
oxytetracycline, rolitetracycline,
doxycycline, minocycline) in the early
stages of acute disease (eg, PCV >15%)
usually ensures survival
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Anthrax
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Anthrax is a zoonotic disease caused by the
sporeforming bacterium Bacillus anthracis .
Anthrax is most common in wild and domestic
herbivores (eg, cattle, sheep, goats, camels,
antelopes) but can also be seen in humans
exposed to tissue from infected animals
B anthracis spores can remain infective in soil
for many years. During this time, they are a
potential source of infection for grazing livestock
Feed contaminated with bone or other meal from
infected animals can serve as a source of
infection for livestock
Anthrax: Bacillus anthracis
Anthrax: Transmission
Epidemiology:
In the USA, anthrax has been reported
among domestic and wild animals nearly
every year since records have been
available.
 B anthracis has been manufactured as a
biologic warfare agent. B anthracis was
used successfully as a weapon of
terrorism in 2001, killing 5 people and
causing disease in 22
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Pathogenisis
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B anthracis spores have a high affinity for
macrophages. After wound inoculation,
ingestion, or inhalation, spores infect
macrophages, germinate, and proliferate
As the bacteria multiply in the lymph nodes,
toxemia progresses and bacteremia may ensue.
With the increase in toxin production, the
potential for disseminated tissue destruction and
organ failure increases
Anthrax: Inhalation
Anthrax spores
Clinical Findings:
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Typically, the incubation period is 3-7 days
(range 1−14 days). The clinical course
ranges from peracute to chronic. The
peracute form (common in cattle and
sheep) is characterized by sudden onset
and a rapidly fatal course. Staggering,
dyspnea, trembling, collapse, a few
convulsive movements, and death may
occur in cattle, sheep, or goats with only a
brief evidence of illness.
Diagnosis:
A diagnosis based on clinical signs alone
is difficult
 Specific diagnostic tests include bacterial
culture, and fluorescent antibody stains to
demonstrate the agent in blood films or
tissues. Western blot and ELISA tests for
antibody detection are available in some
reference laboratories
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Bacillus anthracis, ground glass colonies. Courtesy of Dr. J. Glenn Songer
Bacillus anthracis, methylene blue stain of tissue smear, high power.
Note the intense red stain of the large capsule of this organism and the
large number of bacteria. Demonstration of the capsule distinguishes
this from post-mortem contamination by a Cl Courtesy of the
Treatment, Control, and
Prevention:
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Anthrax is controlled through vaccination
programs, rapid detection and reporting,
quarantine, treatment of asymptomatic animals
(postexposure prophylaxis), and burning of
suspect and confirmed cases.
Livestock at risk should be immediately treated
with a long-acting antibiotic to stop all potential
incubating infections. This is followed by
vaccination ~7-10 days after antibiotic treatment.
Domestic livestock respond well to penicillin if
treated in the early stages of the disease
References
http://edis.ifas.ufl.edu/ig130
 http://pods.dasnr.okstate.edu/docushare/d
sweb/Get/Document-1932/VTMD7000web.pdf
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