VMED 5235

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VMED 5235
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• Ectoparasites of Ruminants
• I. Biting Flies
• II. Non-biting Flies
• III. Myiasis
• IV. Lice
• V. Mites
• VI. Ticks
• VII. Hemi-lymphatic Parasites

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I. Biting Flies
Several species of blood sucking flies (Order
Diptera Suborder Cyclorrhapha) with a general
resemblance to house flies, Musca domestica are
of importance in veterinary medicine. About 50
of estimated animal ectoparasites related losses
in cattle production are due to the biting flies.
Rather than the lapping mouthparts of the
housefly, these species have piercing
mouthparts adapted for blood sucking.
Development cycles involve complete
metamorphosis. Blood feeding mosquitoes, black
flies (Simulium) and biting gnats (Culicoides) of
the Suborder Nematocera are often referred to as
biting flies.
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Haematobia irritans
The common name comes from the flys habit of
sometimes clustering around the horns of cattle.
It is primarily a pest of
range or pastured cattle and is of less
importance in dairy cattle or in feedlots because
it requires fresh, undisturbed feces as breeding
material. The horn fly will attack a number of
other species on occasion including the horse,
but it is largely confined and adapted to cattle.
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Biology-
Horn flies are normally found on the back and
neck of cattle in cool mornings. In hot weather
the flies move during the day to the shaded
underside. They remain on the host day and night
and
feed intermittently on blood, taking made small
blood meals (20-30) per day, orienting themselves
head down and wings spread while feeding.
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Adult female horn flies are about half the size
of houseflies or stable flies but more slender.
Like stable flies, they have piercing
mouthparts which in the resting position is
carried forward so that it looks like a little
finger projecting anteriorly from the head.
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Horn flies leave the host only to lay eggs or to
change host. Eggs are laid only in fresh cattle
feces which are attractive for only about 5
minutes after being dropped. The female fly
darts down, oviposits underneath or in the folds
of the dung pat and returns to the host within 5
to 10 minutes.
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Horn fly eggs are reddish brown and not creamy
white as those of other flies and 1 mm in length.
Eggs hatch in 24 hr and the whitish maggots crawl
into the dropping. About 20-25 eggs are
oviposited each time. Larvae molt twice and
become full grown in
3-10 days. They pupate in soil or under the fecal
pat for 5 more days and emerge as adults. Three
days after mating, females produce eggs for a
life cycle of less than 2 weeks ( longer in
cooler weather). Infestation of horn flies often
number 200 to 5,000 per animal. Bulls and older
animals are preferred. Horn flies change hosts
sometimes and they can fly distances of several
miles. Longevity is about 7 weeks and females
lay up to 400 eggs during this time.
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Several generations can occur per year. In the
north Hematobia over- winters as pupae in
diapause and adults are present from spring to
frost. In southern states, some pupae undergo
facultative diapause in winter and
a few flies can be found on cattle on warm days.
Only one peak population of flies occurs in the
northern states and two peaks in the southern
states, one in early summer and one in late
summer. The decline in July and August is thought
to be due to hot, dry weather. Infestation of
horn flies often number 200 to 5,000 per animal.
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Economic Effects Disease

• Losses due to annoyance, worry leading
• to reduced production

• Very heavy infestations (200 flies) lead
• to significant blood loss

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Stephanofilaria stilesi- a filarid nematode
inhabits the ventral midline of cattle. The
presence of adults and microfilariae in the skin
produces a chronic, dry dermatitis. Haematobia
is the intermediate host.
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Sections of adult Stephanofilaria stilesi can be
seen in histosection of skin. Haematobia can also
carry other diseases as a mechanical vector.
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Stomoxys calcitransStable Fly
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Stomoxys calcitrans, stable flies are found
throughout the USA but are particularly numerous
in the Central and Southeastern states. In
contrast to horn flies, they are more of a
problem around barns or stables than on ranges or
pastures.
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Stomoxys
calcitrans
The female Stomoxys is sometimes called
the"biting housefly" because of the mutual
resemblance in size and general appearance to the
housefly, but Stomoxys is more robust and has a
broader abdomen than the housefly and it has
"bayonet-like" piercing mouthparts.
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Haematobia irritans
Stomoxys calcitrans
The mouthparts of the stable fly and horn fly
are very similar. The proboscis of the horn fly
is held more vertically while the stable fly
holds its proboscis"bayonet fashion when not
feeding.
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Stable flies feed on many mammals but attack
horses and cattle most often. They ordinarily
prefer to feed on the lower body, particularly
the legs. They are most active in sunlight and
usually take only one or two rapid blood meals
per day, completely engorging in about 5 minutes
unless disturbed.
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After feeding, stable flies typically fly to
sunny, often light colored surfaces such as a
barn wall or fence to rest and digest the blood
meal. This can be exploited for control because
stable resting surfaces can be sprayed with good
results. Stable flies tend to rest on a surface
head upwards and perpendicular to the ground.
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Under field conditions stable flies usually do
not breed in excrement unless it is moist and
mixed with decaying vegetable matter, straw or
hay such as occurs around bunkers and feedlots.
Decaying seaweed often gives rise to explosive
numbers of "biting flies" on beaches in summer.

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Stomoxys eggs hatch in 2 days and larvae complete
development in about 10 days and pupate in the
drier parts of the media. Adults emerge in about
4-5 days, mate and the females begin laying eggs
in 5-6 days. The total life cycle is completed in
about 3 weeks (or up to 2 months in cool
weather). Pupae overwinter in wet straw or straw
mixed with feces. Longevity is 3-7 weeks and up
to 1000 eggs can be produced by a single female.
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Several generations of stable flies can occur in
a season and abundance is largely dependent on
the quantity and quality of suitable breeding
media. Heavy infestations can be averted by at
least weekly cleaning of breeding areas such as
horse stalls.
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Stable Flies
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• Economic Effects

• Worry and blood loss due to stable flies can
  cause
• 15 or more reduction in dairy herd production.
• Great annoyance to horses
• Can be a major feedlot problem.
• Abundant flies cause foot stamping and
• tail swishing

• Animals may bunch together or find water to
  

stand in to avoid harrashment
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Stable Fly Control
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Sanitation is the most effective control. Manure
near feed bunkers and wet bedding should be
removed at least weekly and more often in summer.
Although, stable flies can travel miles from
other sites, residual spray on resting surfaces
are effective as treatment measures. Stable flies
spend only a short time on hosts, thus limiting
individual animal treatment for control purposes.

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Family Tabanidae (Suborder Brachycera)
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Horse Fly
The tabanids are biting flies that includes a
large number of species of the genus Tabanus
(horse flies) and the genus Chrysops (deer
flies). Tabanids are usually large and robust.
The approximately 30 species occurring in
Louisiana range in size from that of a housefly
to a hummingbird.
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Biology
Tabanids are strong flyers with a range of many
miles and are important pests of domestic animals
and deer. Only females
are parasitic, feeding on blood, males lack
mandibles and feed on vegetable matter. Tabanids
have an anterior pointing antenna of 3 segments
shaped like an Arabian sword.
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Sponging House fly
Slashing and Sponging Horse fly
Piercing and Sucking Mosquito
Piercing-sucking Stable fly
The broad, blade-like mouth parts of the fema1e
tabanid inflicts a deep and painful wound. An
anticoagulant is injected which contributes to
considerable blood flow which is lapped up by the
fly . Most tabanids are daylight feeders and
attack livestock most often on sunny days.
Tabanids do not attack sheltered animals.
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Tabanus spp. are aquatic or semiaquatic in
breeding habits. Eggs are normally deposited on
foliage or other objects projecting over water or
moist ground during spring and summer.
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Female tabanids lay large masses of eggs which
hatch in about a week and the larvae drop into
the water or moist earth.
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Tabanid larvae burrow into mud and feed on
organic matter, other insect larvae such as those
of stable flies and earthworms in the top few
inches of soil in swamps, lakes, ponds and
streams. A few species can breed in drier
habitats. Most species have only one generation
per year which emerges in spring or summer after
feeding as larvae during the previous summer and
autumn. They pupate in drier ground and emerge as
adults.
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Economic Effects of Tabanids
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Heavily infested livestock commonly have surface
areas of hair matted with blood from tabanid
feedings. Tabanids are attracted mostly to dark
colored animals. Anaplasmosis has been shown to
be transmitted in the southeast primarily by
horseflies.
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The abundance of horseflies in Louisiana and
other areas and their intermittent feeding habits
increases chances of disease transmission by them
as mechanical vectors, especially when stock
cluster together for protection
Tabanids are 'jittery feeders" because their
painful bite induces host reflex behavior. They
are strong flyers, but it has been shown that a
separation of 200 ft is enough to prevent
mechanical transmission by tabanids between
Anaplasma infected and non infected stock. Other
diseases such as anthrax and trypanosomiasis in
Asia, Africa and South America are transmitted by
tabanids.
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Chrysops sp., deer flies are usually much smaller
than horseflies and inhabit broken woodland
areas. They commonly attack deer but will also
attack humans in their habitat.
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Adult Chrysops sp.. have a cross band on their
wings which is absent in Tabanus sp.. Deer flies
have been incriminated as intermediate hosts for
Elaeophora schneideri, a filarid nematode of
sheep, deer and elk in the Rocky Mountains and of
Loa loa, the filarid eye worm of man in Africa.
Deer flies are also efficient mechanical vectors
of diseases such as Tularemia.
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Control
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There are no good control methods for tabanids
because of their dispersed breeding and resting
habits and short feeding period. Ball and tent
traps are often effective in reducing their
numbers.
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Melophagus ovinus - sheep ked (Suborder
Cyclorrhapha) also known as louse flies and sheep
ticks, are wingless flies which have adapted
completely to parasitic existence in the fleece
of sheep. They are ubiquitous wherever sheep are
raised. Sheep keds are blood sucking, obligatory
parasites that spend their entire life span on
sheep.
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Melophagus ovinus
Life Cycle

• Females incubate eggs within their body.
• Larvae develop one at a time in about 7
  days and are then extruded.
• Larvae pupate within a few hours and
  remain in fleece glued to wool fibers

• Young keds emerge from the pupae in ?3 weeks and
  then mate within 3-4 days.
• First larvae are deposited in 8-10 days.
• Total life span is 4 months, each female
  producing 10-12 pupae during that time.
• Transmission is by direct contact, life cycle is
  completed in 32-40 days. Keds are seasonal
  and found in large numbers winter spring.
  

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Economic Effects and Control

Sheep are usually asymptomatic and keds are well
tolerated, but heavily infested animals develop
signs associated with irritation and
pruritis. "Cockle", a reaction to repeated bites,
reduces hide value for leather . The
nonpathogenic Trypanosoma melophagium is
transmitted by sheep keds which serve as
intermediate host. Sheep keds and pupal debris
can be readily observed by parting the wool of
the neck, shoulder, belly or thigh Shearing sheep
removes large numbers of keds and high summer
temperatures also reduces population
numbers. Treatment for keds (and lice) is best
done within 6 weeks of shearing using a variety
of insecticide preparations. Shearing sheep
removes large numbers of keds and high summer
temperatures also reduces population numbers.
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Suborder Nematocera
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Blood-feeding nematocerans can lead to important
production losses in ruminants. The larval stages
are aquatic. Populations of mosquitoes can at
times be so great that stock die of
exsanguination or even suffocation. The major
reason cattle must be moved to summer pastures on
high ground after April 1 in coastal marsh
regions of Louisiana is the emergence of
overwhelming numbers of Aedes solicitans, the
salt marsh mosquito, and other mosquitoes on
marshy, often brackish winter pastures.
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Black flies - Simulium spp.
Black flies, Simulium spp. are seasonally
important in warm weather in certain regions,
especially in the northeastern USA, where their
feeding activities on the ears and elsewhere can
cause livestock severe weeping dermatitis with
great disturbance and irritability in livestock.
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Culicoides spp.
Biting midges, biting gnats, no-see-ums, punkies,
are a diverse group of small gnats whose painful
bite and elusive size is well known to fishermen.
Direct irritation and inflammation from bites of
Culicoides can be significant and in Australia
is well known as the cause of "Queensland itch",
a chronic dermatitis on the rump and back.
Culicoides spp. serve as vectors for bluetongue
in cattle and sheep in the USA and for Onchocerca
gibsoni, a nonpathogenic filarid nematode that
resides in the connective tissues.
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Phlebotomus spp.
Phlebotomus spp., can serve as a vector of
vesicular stomatitis and leishmaniasis where the
diseases occurs. Their bodies and wings are
hairy.
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II. Non - Biting Flies
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Musca autumnalis, the face fly (Suborder
Cyclorrhapha) was first found in this country in
New York m 1953 and has since become a serious
pest cattle, horses, and some breeds of sheep in
the northeast, northwest and central states. It
has spread west to California and only 5 states
were free of the face fly by 1971. They were
Louisiana, Florida ,Texas, Arizona, and New
Mexico. It first appeared in Louisiana in 1978
but subsequent droughts wiped out the population
and the state has been free since 1998.
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Musca domestica, the house fly, has a familiar
life cycle in animal waste or other organic
material and well known habits. The housefly is
commonly associated with livestock facilities or
garbage as a cause of great public annoyance and
they have long been incriminated in mechanical
transmission of a variety of diseases via
mouthparts, legs or internally.
These dull colored flies feed by sponging up
fluids and regurgitating "saliva" to help soften
solid food. The number of law suits are
increasing to force control measures for the
house fly (life cycle of 9 days to 2 weeks ) and
related members of the "filth-fly community",
including Muscina . (False stable fly), Euphoria
(garbage flies), Fannia (Little house fly,
latrine fly), Hermetia (Black soldier fly)
Eristalis (Drone fly)
and Psychoda (Moth flies). The latter feed on
livestock waste as adults or larvae and sometimes
on secretions.
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Manure management Control involves
mostly prevention by reducing suitable breeding
habitats. Egg mortality increases greatly when
substrate moisture falls below 90 humidity.
Residual surface sprays and area sprays or mists
are most effective around livestock housing.
Baits containing insecticides and sugar or other
material can be used, but feed additives are
usually ineffective because both old decaying
manure and fresh manure and garbage can be used
for breeding house flies. Ear tags and self
treating devices are ineffective.
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III. Myiasis Myiasis is the infestation of
vertebrates by dipteran larvae (maggots).
Parasite and host relationships are vary as
follows A. Facultative myiasis. Larvae normally
are free living in decaying organic matter and
may gain access and adopt the tissues of living
vertebrates where they feed only on dead or
necrotic debris. A vertebrate host is not
essential to the completion of the fly's life
cycle. B. Obligatory myiasis- Larvae develop
exclusively in or on a living vertebrate host.
The host is essential for completion of the
fly's life cycle. C. Accidental myiasis- Larvae
normally develop in a wide range of organic
matter, but may invade living tissues when the
eggs are accidentally ingested or deposited on a
host.
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Myiasis can also be classified by location a.
Dermal myiasis. warbles in skin (Hypoderma,
Oestrus), invasion and/or enlargement of wounds
(Phormia, Lucilia, Sarcophaga, Cochliomyia
americana). b. Nasopharyngeal myiasis- invasion
of nasal passages into sinuses and pharynx
(Oestrus ovis). c. Gastrointestinal myiasis-
invasion of gastrointestinal tract by wounds on
accidental ingestion (Sarchophaga, Cochliomyia
americana). d. Somatic myiasis- migration of
dipteran larvae in somatic tissues (Hypoderma).
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Facultative myiasis- "Fly strike" is caused by
one or more of several species that can feed on
either carrion or exudates and dead tissues in
wounds or soiled matted wool or hair, usually
leading to dermal myiasis.
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Phormia regina Phaenicia sericata
Calliphora sp..
Commonly incriminated species include members of
the family Calliphoridae the black blow fly,
Phormia regina, the green bottle fly Phaenicia
sericata used in cleaning wounds the blue
bottle flies, Calliphora spp., all of which have
a metallic sheen. The dull, striped flesh flies,
Sarcophaga spp. and even the house fly, Musca
domestica can be involved.
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Dermal or cutaneous myiasis caused by "wool
maggots" is cosmopolitan in distribution, with
the major species of flies varying from area to
area, and is fatal if not treated. Wool maggots
in particular are very important in sheep raising
areas of the world, especially in Australia due
to Phormia regina. Female flies are attracted to
odoriferous sites such as ulcers, wounds, or
fecal or urine soiled wool and lay eggs. Merino
breeds of sheep have "folds" in the perineal area
that often becomes moist from excreta or
prolonged rains. As hatched larvae feed,
inflammation and potent exotoxins produce more
dead tissues allowing larvae to invade deeper and
deeper, often undermining the subcutis of the
skin over large areas and attracting more flies.
Unattended, the animal dies and becomes carrion.
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Obligatory Myiasis
Obligatory Myiasis- Cochliomyia americana, the
primary screwworm fly was once widespread
throughout the southern tier of states of the
USA, prior to a successful USDA eradication
campaign. Based on mass release of sterile male
flies, the program was one of the first triumphs
in biological control. Unable to overwinter in
colder climates, but able to fly a distance of
100 miles, a seasonal northward invasion of
screwworms occurred annually from the warmer
areas of Mexico, southern Texas and Florida
causing billions of dollars in livestock losses.
Incidence of infestations was pushed south of a
buffer zone along the USA-Mexico border by 1964
and is now held below a narrower buffer zone in
southern Mexico. C. americana differs from other
obligatory myiasis flies by the need to attack
and feed on live tissues irrespective of species
of host. A wide range of domestic and wild
animals are affected.
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Biology - Cochliomyia americana
Females deposit 10-400 eggs at the edges of open
wounds which can be mere cuts, scratches, tick
bites, or tabanid bites. Larvae hatch within a
few hours and invade and feed on live tissue for
5-6 days.
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Biology - Cochliomyia americana
Larvae
Adult emerging
Larvae then drop out and burrow into the ground,
pupate and emerge as adults in about 1week.
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Biology - Cochliomyia americana
Adults are metallic greenish-blue in color with
three dark stripes on the thorax. Only minor
characters separates the adult C. americana from
the adult of C. macellaria, the secondary
screwworm fly which is still widely distributed
in the USA. The central thoracic stripe maybe
shorter in C. americana.
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Tracheal trunks
Primary C.hominivorax
Larval mouthparts
Secondary C. americana
The larvae of C. americana can be differentiated
from those of C. macellaria and other facultative
species by the darkly pigmented tracheal tubes of
the primary screwworm larvae and nonpigmented in
the other larvae. As a reportable disease,
suspect larvae must be sent to USDA for
definitive identification. In 1987 larvae in
wounds of a dog through New Orleans from Central
America suspected to be the primary screwworm
were reported by a practicing veterinarian in
Florida, thus enabling rapid control measures to
be taken by USDA.
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Infested wounds like these in an injured eye are
often fatal to cattle within 10 days. Initial
invasion of fresh wounds by primary screwworm
were often followed by facultative species
(secondary screwworms).
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Eradication of C. americana
Because females generally mate only once,
competitive, laboratory raised male flies raised
in captivity, sterilized in the pupal stage were
released in
large numbers. Large numbers of unproductive
females result when the ratio of sterile males to
each female fly is greater than10 to 1
(production capacity was 2000 million flies per
week). This approach was first tested in Curacao
in 1954 and expanded to Florida and southeastern
USA in 1958. In 1962-64 elimination of both
migratory and overwintering populations
throughout the USA was completed.
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Eradication
Eradication with the sterile male technology was
possible because of the alert surveillance and
treatment by producers, veterinarians and county
agents who directed where drops should be made.
The current program in Mexico also uses a new
bait station toxin "Swormlure" which has been
found effective in preparation for sterile male
release. Suspect larvae should be sent to
Southwest Screwworm
Eradication Program, APHIS, USDA,
Box 969, Mission, TX 78572
(pre-addressed vials are available from county
agents and USDA
offices)
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Hypoderma
Hypoderma (Warbles, Heel fly, Gadfly, Grubs) is
an obligatory myiasis fly with a complex, highly
evolved life cycle that takes one year to
complete. Mature grubs are found in the
subcutaneous tissues of the back line and are the
3rd
stage larvae in the life cycle. Two species occur
in the USA H. bovis, the "northern cattle grub"
found in the northern USA and H. lineatum, the
"common cattle grub, found in the southern USA.
The ranges of the two species overlap, but only
H. lineatum occurs in Louisiana.
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Hypoderma
Warbles are found in subcutaneous nodules in the
skin of the back. A fistulous opening is present
in each nodule serving as a breathing
hole. When mature, grubs can be extruded by
manual squeezing, carefully to avoid rupturing
the larva which may result in anaphylaxis from
toxic materials released.
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Hypoderma
Grubs are large, robust 3rd instar larvae, with
small mouth hooks and no body spines. They are
small (1 cm) when they arrive in the backline

and grow rapidly during 40 days residency. They
emerge spontaneously during winter/spring in
Louisiana, drop to the ground to pupate until the
arrival of warm weather, about
4-10 weeks. The adults live only for 7-10 days.
The robust flies do not feed, their sole function
being to mate and produce eggs.
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Adults are most active during warm days in spring
and summer. Eggs are laid on the distal hind
limbs, thus the term "heel fly' . The flies make
a distinctive sound that terrorizes some cattle
and stampedes them. Reasons for such reaction
are obscure since there is no apparent pain or
bite associated with egg laying. The eggs of
Hypoderma are cemented to hairs, those of H.
lineatum in clusters of 5- 7 per hair and those
of H. bovis usually singly on a hair.
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Hypoderma
Larvae hatch from the eggs in 3-4 days and
directly penetrate into the skin. This would be
the only apparent association with pain. Small
larvae migrate over a 5 month period via the
subcutaneous tissues or muscle fascia to the
thoracic area. H. lineatum then migrates to the
submucosa of the esophagus and H. bovis migrates
to the epidural fat of the spinal canal. They
remain in their respective sites for 3 months.
Larvae are still only 10-15 mm in size at this
time. Larvae then migrate in subcutaneous
tissues to the back where they set up cavities in
the subcutis and begin to grow rapidly over a
40-day period. An aperture is cut in the skin for
breathing. The total life cycle takes one year to
complete.
.
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Hypoderma seems to be well tolerated by cattle
and the major economic loss is attributed to a
reduced hide value. If a large number of grubs
have been present, the subcutaneous fat can take
on a brownish, gelatinous character. Holes or
scars in the skin caused by Hypoderma reduces the
hide's value for leather.
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Hypoderma
The entire life cycle of Hypoderma is influenced
by weather. In Louisiana the grubs first appear
on the back in winter . The first activity o f
the flies is in late spring o f each year , March
15-April 15 in Louisiana. The information is
important because treatment with systemic
organophosphates should be done during the 5
months larvae are migrating to the esophagus or
spinal canal. Once in these sites, larva1 death
and the host response may result in esophagitis
and bloat (H. lineatum) or posterior paralysis
(H. bovis).
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Oestrus ovis- nasal bot is a common, ubiquitous
parasite found wherever sheep are raised. Several
nasal bots can be seen in the sinuses of this
sheep head in cross-section. Oestrus ovis is only
mildly pathogenic and causes little beyond a mild
chronic rhinitis and sinusitis. Oestrus larvae
have large mouth hooks and spines only on the
ventral surface of the body.
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The Oestrus ovis annual life cycle is initiated
by the non-feeding, short-lived adults which mate
and then the female squirts the eggs into the
nares from around the nostrils. Adult fly
activity causes sheep to group together with
their heads down.
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Nematode parasites transmitted by biting flies
Stephanofilaria stilesi, a filarial nematode
transmitted by H. irritans causes chronic
dermatitis in the umbilical area of cattle. It
occurs throughout the USA, but is more common in
the western part. It is of little importance
except as a cause of minor hide damage or
secondary infection with screwworms. Early
lesions are reddened, scabby and ultimately
progress to rough, fissured, thickened chronic
lesions of 1 to 6 inches in diameter .
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Haematobia irritans, horn fly has been shown to
be the intermediate host for S. stilesi. Both
adults and microfilariae of S. stilesi are found
in skin lesions. Diagnosis can be made by
identifying microfilariae that migrate into
saline from skin snips.
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Elaeophora schneideri, a filarial nematode causes
a chronic, scabby dermatitis on the face and poll
of sheep. Lesions occur to a lesser extent in the
nasal and buccal cavity or hind feet. The
intermediate host is H. irritans.
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IV Lice (Pediculosis)
Lice are one of the most common ectoparasite in
cattle and can cause clinical effects when in
large numbers. Patchy alopecia as seen is the
result of rubbing in response to pruritis
associated with "pediculosis". Sucking lice in
large numbers may cause anemia. Weight loss,
decreased weight gain and decreased milk
production can occur.
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Anoplura
Mallophaga
The sucking lice (Anoplura) have narrow heads
with stylets for sucking blood and the biting or
chewing lice (Mallophaga) have heads, as wide or
wider than the thorax and large mandibles.
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Eggs
Adults
Male
Female
Nymph (3)
The life cycle of lice is one of incomplete
metamorphosis. Eggs (nits) are attached to hairs
and develop through three nymphal stages to adult
males and females. The life cycle is completed in
approximately 3 weeks.
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Lice are highly host specific and transmission is
by direct contact. Lice live only about 1 week
off the host and crowding enhances louse
problems. Bulls and young animals seem more
susceptible to infestation than others. Heavy
louse infestations with most lice occurs in
winter and spring. The tail louse Haematopinus
quadripertussus is an exception and occurs in
greatest numbers in late summer and fall in the
southeastern states.
73
72
Cool temperatures are thought to stimulate egg
production and massive louse populations can
build up after a few generations. During the
summer and hot weather, lice retreat to protected
areas such as ears, folds in skin and between the
legs. Even in moderate warm weather, skin
temperatures can reach 100 or more in the sun
and is unfavorable for louse survival.
74
Characteristics of Cattle Lice
74
75
Characteristics of Cattle Lice
75
Name Size(mm)
Color Type Location Activity
76
76
1
2
Louse infestations are more apparent on light
colored animals and the hair coat may appear
"sooty" if large numbers are present. Note "nits"
and dark lice (1) and the cluster of Linognathus
(2). Lice are harder to see on dark animals but
the nits are lighter in color.
77
77
1
2
Note large number of nits in this animal (1).
Feeding lice, Solenopotes, are indistinctly
visible on this Angus bull (2) which has denuded
the shoulder area by rubbing and scratching. Lice
are found by closely examining the coat of the
neck, shoulders, topIine, perineum, brisket and
poll.
78
78
Damalinia bovis(Bovicola bovis), the little red
louse, is the only chewing louse of cattle. It
feeds on the skin or hair debris and works its
way up and down the hair shaft, attaching with
specialized groove-like mouthparts It has a wide
head
and is reddish in color. Moderate to heavy
populations cause chronic dermatitis associated
with pruritis and results in animals rubbing
against posts, feed bunkers, etc. to relieve
itching.
79
79
Lice may occur in large numbers in sheep or
goats, but are often neglected. Lice are
associated with chronic dermatitis and annoyance,
unthriftness, wool damage and poor gain.
Afflicted animals may respond by rubbing, biting,
wool-pu11ing and kicking.
80
Characteristics of Sheep Lice
80
Names
Length(MM)
Color
Type
Location
Activity
81
81
Lice Found on Domestic Animals
Host Anoplura Mallophaga Cattle Haematopinus
eurysternum Damalinia bovis Haematopinus
quadripertussus Haematopinus
tuberculatus Solenopotes capillatus Horse
Haematopinus asini Damalinia
equi Pig Haematopinus suis None Sheep Linogn
athus ovillus Damalinia ovis Linognathus
pedalis Goat Linognathus africanus Damalini
a caprae Linognathus stenopsis Damalinia
crassipes Damalinia limbata Dog Linognath
us setosus Heteroxus spiniger Trichodecte
s canis Cat None Felicola subrostrata
82
82
V. Mites
Four species of mites are known to affect cattle
in the USA Psoroptes equi var. bovis, Chorioptes
bovis, Sarcoptes scabiei var. bovis and Demodex
folliculorum var. bovis. The first three cause
pruritic, subacute, or chronic, contagious skin
conditions called "scabies". Demodex causes
non-pruritic, nodular asymptomatic skin lesions
and is of little clinical importance.
Characteristics of bovine mites are listed in the
following table
83
83
Mange type
Name
Location
Characteristics
84
84
The causative agents of scabies share several
characteristics
-The life cycle is completed in 2-3 weeks -They
are highly host specific (affect only a single
species) -Each has a genetic predilection site
for initial lesion -They are most active in cool
weather, especially winter -They are transmitted
by direct contact and survive less than one week
off the host -All breeds, sex and ages may be
affected, but severity varies greatly among
individuals in a herd and usually occurs in
animals over 6 months of age
85
85
Animals with scabies experience irritation and
pruritis indicated by continual licking, biting,
kicking, rubbing and tail switching. Decreased
feed consumption and loss of condition may occur
which can have a devastating effect on weight
gain in feedlots, etc. Rubbing to relieve itching
results in hair loss. Specific manifestations of
each mite causing scabies may differ .
86
86
Rump
Tailhead
Scrotum
Chorioptic mange ( symbiotic scab, tail scab) is
presently more common in cattle than so called
"common mange" due to Psoroptes as a result of an
eradication campaign initiated by USDA in 1935.
Early lesions due to Chorioptes bovis are most
common on the escutcheon with later spread to the
medial thigh, tailhead and flanks. Chorioptic
mange is not as pruritic as either psoroptic or
sarcoptic manges. A chronic advanced case of
chorioptic mange is shown on the rump, tailhead
and scrotum Note the alopecic, thickened,
fissured and crusty appearance of the lesions.
87
87
Chorioptes bovis is considered to live in shallow
tunnels in scurfy debris produced on the skin
surface, feeding primarily on skin debris. Note
flakiness and alopecia of this chronic lesion.
Mites are most likely found on the periphery in
most active, inflamed areas.
88
88
A diagnosis of scabies is confirmed by skin
scrapings or scratching using a scalpel or
similar edge and identification of mites. A black
surface for examining the scraping increases
visibility of whitish mites that emerge from
debris. A deep scraping is taken from new lesions
or the periphery of chronic lesions.
89
89
USDA field veterinarians sometimes used a piece
of black felt or a black top hat as a smooth,
black surface to examine scrapings. Warmth of the
sun stimulates mite activity and a hand lens may
be used to find motile whitish mites which are
further identified by mounting on a slide for
microscopic examination.
90
90
Psoroptes
Sarcoptes
Chorioptes
Sarcoptes, Chorioptes, and Psoroptes can be
easily differentiated by leg stalk characteristic
and mouthparts. Speciation is more difficult and
usually requires an expert acarologist.
91
91
Female
Male
Mouthparts
Chorioptes has short, unjointed leg stalks and
blunt, rounded mouthparts of female and male.
Males have adana1 suckers and two caudal
protuberances and the more rounded female has
none.
92
92
Psoroptes Lesions
Early lesions caused by Psoroptes have a
predilection for the withers, backline and
tailhead in heavily haired areas Lesions appear
14-45 days after exposure and can become
generalized, especially in weak, poorly nourished
stock.
93
93
Psoroptes Lesions cont.
Mites feed more on the skin surface as compared
to the superficial tunnels of Chorioptes.
Sarcoptes tunnels into the epidermis itself.
Sharp mouthparts are used to pierce the skin and
feed on lymph, blood and serum.
94
94
Psoroptes Lesions cont.
Mite bites and reaction to saliva causes serous
scabs with constant severe pruritis and secondary
self-inflicted trauma. Advanced lesions have a
denuded, scaly center with an active, scabby
periphery.
95
95
Psoroptes has pointed, elongate mouthparts and
long, jointed leg stalks. Psoroptes is highly
contagious but has been reduced to sporadic
outbreaks, especially in feedlots and stock
shows. Not seen in Louisiana recently, cases are
reportedly still encountered in the Texas
panhandle and Oklahoma by federal inspectors.
96
96
Sarcoptes scabiei
Male (ventral
Skin scraping
Female(dorsal)
Sarcoptes scabiei var. bovis (barn itch) is found
in low incidence and occasional outbreaks in most
of the USA, especially in dairy animals. Mites
burrow into the epidermis itself eggs and
metabolic wastes induce inflammation and severe
pruritis. New generations of mites emerge to the
surface to mate and again submerge, creating a
new burrow.
97
97
Early lesions of Sarcoptes occur in the
relatively lightly haired areas of the escutcheon
and medial thighs and then spread along the
abdomen to the flanks, brisket, neck and down the
legs. The legs of this animal are affected with
acute sarcoptic lesions. Note the conical
papillae with dried, yellowish serum in the
histosection. Eventually Sarcoptes can generalize
over the entire body.
98
98
Demodex causes follicular mange, multiple nodular
lesions, usually nonpruritic, in the skin of the
shoulders, neck and brisket of cattle. If the
surface skin or the scab of large nodules are
removed, necrotic debris and exudate containing
large numbers of mites may be squeezed out of
greatly enlarged hair follicles.
99
99
Bovine Scabies
In the USA, bovine scabies is reportable (not
Demodex). Animals are quarantined until treated
and determined free of disease under supervision
of state and federal veterinarians.
100
100
Psorergates sp.
Psorergates ovis, itch mange mite is a small
round mite with no leg stalks armed with claws
instead of suckers. It has been found
occasionally in the
USA and causes intense pruritis. It has been seen
mainly in Merino and Merino-X breeds, spreads
slowly and is found in heavily wooled areas of
the flank, sides and thigh. It is found on the
skin surface where it feeds on lymph. Psorergates
bos is rare but has been reported from cattle in
the western USA
101
101
Raillietia
Raillietia auris is a small mite, 1mm in length,
occurs in the ears of cattle in North America,
South America and Europe . The presence of these
mites is not associated with any clinical
disorder.
Ventral view
102
102
Ticks and tick-borne agents of disease
Ticks are members of the superfamily Ixodoidea of
order Acarina, which includes both mites and
ticks. The ticks are divided into two families
the Argasidae or "soft" ticks and the Ixodidae or
"hard" ticks.
103
103
Hard tick (male)
Hard tick (female)
Soft tick
The Argasidae are covered by a leathery cuticle,
whereas the Ixodidae have a dorsal shield or
"scutum" which almost completely covers the back
of males but only the anterior portion of
females. Viewed from the dorsal aspect, the
mouthparts of the soft ticks occupy a ventral
position and are hidden under the margin of the
body, The hard ticks have more rigid mouthparts
which project anteriorly .
104
104
The hard ticks are classified into three groups
based on feeding pattern and the number of hosts
required to complete the life cycle. The genera1
life cycle of the Ixodidae pass through four
stages (egg, larva, nymph and adult )varying
from 6 weeks to 3 years.
105
105
In the One host tick all three stages engorge and
molt on one individual host (Boophilus annulatus).
106
106
The larva of a two host tick engorges and molts
to a nymph on the host. The nymph remains on the
host, engorges and drops to the ground where it
molts to an adult. The adult then seeks a new
host.
107
107
The majority of ticks follow a three-host feeding
pattern. Most of these tend to attack small
mammals or birds as larvae and nymphs, and larger
mammals as adults. In general, ticks, unlike
mites, have a host preference and not a strict
limitation to certain host species.
108
108
Females of the Argasidae, except for Otobius,
feed repeatedly as nymphs(more than one molt) and
adults lay their eggs in small batches at
intervals of weeks or months. Females of the
Ixodidae take a single enormous meal and drop off
the host to lay their eggs at once and pile them
up in elongate masses in front of them. Ixodid
ticks lay their eggs in sheltered spots such as
under stones or in cracks and crevices. Female
hard ticks die shortly after laying ova.
109
109
Eggs of Dermacentor spp. require from 2 or 3
weeks to several months to develop depending on
species and environmental conditions. Eggs
deposited in the fall do not hatch until the
following spring. Tick eggs are covered with a
waxy secretion and may withstand harsh
environmental conditions. They survive long
periods of water submersion but do not survive
desiccation well.
110
110
After ticks initially pierce the skin, a "cement"
substance is secreted by the salivary glands
which helps anchor the tick in place. A pool of
blood forms
under the mouthparts and the tick feeds by
intermittently exchanging blood and saliva during
the feeding period. More potent toxins are
produced by certain ixodid ticks which are
capable of producing a specific neurologic
disturbance called "tick paralysis". Dermacentor
spp. and Amblyomma spp.are known to cause
paralysis in the USA.
111
111
Diseases caused by ticks
A. Direct Effects Bites-inflammation,
ulceration and secondary
infection Hypersensitivity reactions to
secretions Tick-host anemia Toxicosis Tick
paralysis
112
112
Diseases caused by ticks cont.
B. Transmission of disease agents
The primary importance of ticks in veterinary
medicine is their disease transmission potential.
Ticks can transmit diseases in three different
ways
1) Simple replication - Maturation /or
replication of an organism in a single tick
stage and subsequent transmission. 2)
Trans-stadial - Larvae or nymphs acquire a
pathogen which survives the molt and is
transmitted by the next tick stage. 3)
Transovarial - Pathogens are acquired by a female
and transferred through the reproductive system
to the egg and subsequent progeny.
113
113
Tick Paralysis
Flaccid, ascending motor paralysis caused by
a neurotoxin Injected by engorging female
ticks 5-9 days after attachment If untreated ,
death in 1 - 4 days from respiratory
failure Rapid recovery after tick removal
114
114
Dermacentor andersoni
Most cases of tick paralysis in the USA are
associated with Dermacentor andersoni, the Rocky
Mountain Spotted Fever tick. In the southern USA,
Dermacentor variables, Amblyomma americanum and
Amblyomma maculatum produce paralysis in man and
dogs. Tick paralysis occurs in a wide range of
hosts. In livestock, mostly young animals are
affected.
115
115
Lesions at the site of attachment of ixodid ticks
develop a small ulcer and a local foreign-body
type reaction directed against the embedded
mouthparts. The break in the skin may predispose
to fly strike and secondary infection.
116
116
Dermacentor variabilis
Three host ticks D. variabilis D.
andersoni D. occidentalis
One host tick
D. albipictus is in- ornate and primarily a
problem in winter
Four species of Dermacentor, the wood ticks, are
of importance in the USA. Three are ornate and
difficult to differentiate from one another. D.
variabilis, the " American dog tick" is the most
widely distributed species and is found
throughout the USA except in the Rocky Mountains
and inter mountain regions. Adults prefer the dog
as a host but can be found on man, cattle, horses
and cats. They prefer grassy or brush covered
habitats and are frequently found on roadsides
and recreation areas such as picnic grounds.
117
117
Amblyomma americanum
Amblyomma americanum, "Lone Star" tick is a
three-host tick widespread in the southeast and
the midwest. They feed on domestic animals,
notably deer cattle, horses, dogs and man. The
ear is the preferred site of attachment, but in
heavy infestations, belly, flank or perineum can
be parasitized. The common name "Lone Star" tick
is derived from a white star.like marking on the
scutum of female ticks.
118
118
Amblyomma maculatum
Amblyomma maculatum, "Gulf Coast" tick is ornate
in both sexes and found on the South Atlantic
coastal and gulf regions of high temperature and
humidity. It is a three-host tick affecting
cattle primarily and horses, sheep, deer, dogs
and man secondarily. Larvae and nymphs attack
primarily ground inhabiting birds such as quail
and some rodents.
119
119
A. maculatum accumulates in large numbers on the
inside and outside of the ears. Trauma and
secondary infection associated with feeding ticks
sometimes initiates a suppurative process.
120
120
Ixodes spp.
There are two species of Ixodes of interest in
the USA. They are inornate and have long
mouthparts. Ixodes scapularis, Black-legged tick,
shoulder tick, occurs primarily on cattle and
secondarily on sheep, horses, dogs and man in the
Southeast along the gulf coast. Ixodes pacificus,
California Black -legged tick is found on the
West Coast. Deer are the primary host. Secondary
hosts include cattle, sheep, dogs and man. Ixodes
scapularis (I.dammini) is the vector for Lyme
disease in northeastern USA.
121
121
Soft ticks of veterinary importance
Otobius megnini, the spinose ear tick is endemic
in the southwestern USA.
Larvae and nymphs parasitize mainly cattle, but
horses, sheep, dogs and other hosts may be
affected. Adults are not parasitic.
122
122
Otobius megnini
Nymphs of the spinose ear tick have spines and a
unique bow fiddle shape. They are a pale yellow
to pink color and are difficult to see in ears
among earwax, etc.
123
123
Otobius megnini
Larvae find their way to the external ear canal
where they suck lymph. Larvae soon molt to nymphs
which remain in the ear for 1- 7 months.
Eventually, the nymphs fall to the ground, molt
twice and then molt to adults and mate. Adults
are found around feed bunkers, water troughs,
barns and other shady places. Once established in
a stable or barn, Otobius can become tenacious
problem and is eradicated only with great
difficulty .
124
124
Argas persicus
Argas persicus, Fowl tick, Blue bug, Tampan has a
worldwide distribution. In the USA, Argas occurs
primarily in the southern part of the country .
Larvae, nymphs and adults parasitize primarily
chickens. Turkeys, ducks, geese and wild birds
serve as secondary hosts. The color of the tick
is a slatey-blue when engorged.
125
125
VII. Hemi-lymphatic parasites
The most important parasites of the bovine
hemi-lymphatic system are protozoa. These
protozoan agents present very real disease
control problems to regulatory veterinarians in
the USA. An example is the accidental importation
of Rhipicephalus evertsi into Florida and New
York by zoo ruminants from Africa in 1960. After
launching a major effort, it was eliminated from
the USA by USDA in 1962. This species transmits
East Coast fever (Theileria parva), Texas Cattle
fever (Babesia bigemina), Babesia equi of horses
and an exotic Borrelia species. Hemi-lymphatic
parasites of lesser importance are the blood
flukes of the genus Schistosoma in Asia and
Africa and the nonpathogenic filarial worm
Setaria cervi which resides in the peritoneal
cavity and produces microfilariae which are found
in the blood.
126
126
Trypanosomiasis of domestic animals and man has
been considered by WHO to be among the ten major
health problems facing mankind. In Sub- Saharan
Africa, 4.5 million square miles are almost
devoid of cattle because of trypanosomiasis.
Trypanosoma in a Giemsa blood smear.
Of the several Trypanosoma species T. congolense
and T. vivax cause by far the greatest economic
loss . T. congolense is most pathogenic and is
most important in East Africa. In West Africa,
this species is less common and is overshadowed
by the less pathogenic T. vivax. T. brucei is
widely distributed but is far less pathogenic
than either of the above in cattle. Mixed
infections are the rule in some areas.
127
127
Tsetse flies
Several species of blood-sucking, day-biting
Tsetse flies (Glossina sp.) serve as vectors via
the salivary glands and limit the distribution of
nagana in Africa to the fly belt.
Various wild ruminants serve as reservoir hosts.
T. evansi causes "surra" (means "rotten" in
Arabic) in North Africa, Asia and northern South
America and is transmitted mechanically by
horseflies (Tabanus) and deer flies (Chrysops).
It is usually subclinical in cattle and affects
mainly horses, pigs and dogs. T. vivax is
similarly transmitted where it occurs in Central
and South America.
128
128
Piroplasms. The "piroplasms" include the genera
Babesia and Theileria each with several species
which are biologically transmitted by various
ixodid or hard ticks to food animals.
129
129
Babesia bigemina. was once one of the most
important infectious disease of cattle in the USA
and was largely responsible for the formation of
the U.S. Livestock Sanitary Association. Smith
and Kilbourne's milestone work (1893) on
transmission of Babesia bigemina (and the smaller
B. argentina B. bovis B. berbera) by Boophilus
annulatus was the first demonstration of
arthropod transmission of any disease.
130
130
Boophilus annulatus
Boophilus annulatus is the vector of "Texas
fever" caused by Babesia bigemina. The disease
was once widespread in the southern USA and
received its name because large cattle herds
driven northward from Texas passed this
mysterious disease to cattle in the north
Disease Characteristics. Disease caused by the
various Babesia sp. Follow a fundamentally
similar pattern and consists of an acute and a
chronic phase. After an incubation period of 1- 2
weeks, the acute phase begins with a febrile
response (up to 41.5C) which is related to a
marked parasitemia of 2-3 days duration
accompanied by anorexia and lethargy. Rapid
reproduction of the organism occurs by binary
fission with cell lysis and invasion of new
cells. Hemolysis of red blood cells leads to
anemia, hemoglobinuria, dehydration and
occasionally jaundice.
131
131
Boophilus infestation in cow
A cooperative tick eradication campaign using
cattle dips and quarantine was successfully
carried out between 1906 and 1943. The
eradication of bovine piroplasmosis was possible
because B. annulatus is a one-host tick feeding
exclusively on cattle.
A 1972 outbreak of Boophilus microplus in cattle
and deer in Alice, Texas over 100 miles north of
earlier records illustrates the importance of
continuing surveillance of the Mexican border by
the USDA.