Caseous%20lymphadenitis%20in%20goats%20 - PowerPoint PPT Presentation

Title: Caseous%20lymphadenitis%20in%20goats%20


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Caseous lymphadenitis in goats sheepPaul R.
EarlFacultad de Ciencias BiológicasUniversidad
Autónoma de Nuevo LeónSan Nicolás de los Garza,
NL, Mexicopearl_at_dsi.uanl.mx
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Introduction. Caseous lymphadenitis
(CL) involves 1) prenatal intoxication causing
immune tolerance, 2) respiratory paralysis, 3)
the futility of vaccinating subclinically
infected animals, many of which do not respond
well immunologically, 4) involves treatment and
5) quarantine as needed for eradication.
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The theme of perinatal CL is death by paralysis
with many variations. In districts with CL, all
goats and sheep may be infected as they are
likely born tolerized to the toxin phospholipase
D (PLD) and the other corynebacterial proteins.
This means that the kids (cabritos) and lambs
have no defense against prompt infections that
can raise the blood PLD concentrations to lethal
levels including demyelination analogous to
diphtheric polyneuropathy.
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Pathology. It is a false impression
that CL in goats sheep caused by
Corynebacterium pseudotuberculosis and is
confined to the lymphatic system, evincing
abscesses and granulomas mainly seen in the skin.
Grave lesions in the lungs are common. CL can be
a permanent heritage rather than a chronic
disease as the fetus is often exposed to and
therefore tolerized by the toxin phospholipase D
(PLD) and other corynebacterial proteins produced
in its infected dam.
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In some districts and countries like Mexico,
all sheep and goats that have been inspected
are or were infected. To vaccinate them as being
disease-free is a traditional mistake. The
cabrito can acquire immune tolerance. Many
neonatal cabritos intoxicated with PLD are
infected from their dams milk, feces in the
corrals or from other goats with the production
of more PLD leading to paralysis and death. That
is, many tolerized cabritos born intoxicated with
PLD never reach market age of 1 to 3 months,
dying of asphyxiation that is almost always
undiagnosed. This is respiratory muscle
dysfunction.
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An unusual but wellknown situation is
exemplified. A truckload of 600 cabritos arrived
in Monterrey, NL after a 6-hour ride at 8 oclock
of a hot day. All were dead. This is why
slaughter is at night, and trucks start off after
6 oclock, arriving at times like 4 AM.
Asphyxiation was credited to the heat, and of
course goatraisers do not know about PLD. In one
ranch, 352/352 cabritos of a herd of 500 goats
died, and complete wipeouts are common. The
majority might pass as cases of pneumonia, but
actually death is by paralysis involving the
demyelination of the nerves to the diaphragm.
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Furthermore, C. pseudotuberculosis has been long
known to infect horses and cattle. Infections in
man are known for over 50 years Still, it is not
always clear that Corynebacterium sp. rather than
Actinomyces sp. was the cause. ? Hemolysis with
catalase Identification of orynebacterium
pseudotubercul-osis. It is Gram-positive and
catalase positive, usually a bacillus, but on
solid agar it can grow as a coccoid.
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Biochemical tests that are suggested for
coryneform bacteria are 1) catalase, 2)
nitrate, 3) starch, 4) pyrazinamide,
5) esculin, 6) mannose, 7) mannitol,
8) ribose, 9) trehalose, and 10) xylose.
However, many more tests might well be added.
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Treatment. Animals can be successfully
treated orally with penicillin G, and oral
tetracycline is a second choice on a longterm
basis such as 2-3 months of treatment. However,
encapsulated abscesses (cheesy glands) have to
be removed or cleaned out surgically. Rose-red
abscesses should have the circulation needed for
antibiotic treatment.
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In common texts, antibiotic treatment is
discouraged unfortunately as blocked circulation
is considered. Treatment lowers the PLD levels.
Negative levels will change to positive antitoxin
levels with successful penicillin since PLD
production by the bacteria is then stopped while
antibodies are being produced. By a negative
antitoxin level is obviously meant a positive
toxin titer. The cabrito that is born intoxicated
has a positive toxin level Nonetheless, the
textbook advice could imply that difficult
treatment costs more than the patient.
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Vaccines. Human and animal health vaccines dating
from Louis Pasteur have had enormous success in
disease prevention. Diphtheria by Corynebacterium
diphtheriae is among these famous diseases.
Nevertheless, CL vaccines have consistently
failed via not recognizing immune tolerance for
PLD and other proteins of Cps. There are also a
large number of antecedent works, all to be
graded as failures, because survivors have often
been taken as uninfected, and the antibody status
of the host before and after vaccination was not
given. Toxin in the blood should be searched for.
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The futility of vaccinating an infected and
thereby PLD-intoxicated animal has not always
been wisely taken into account. The effect of the
first vaccination can often be that of a booster
when antitoxin is detectable.. Nonetheless, the
health status of each goat or sheep against CL is
not usually known, and in particular its CL
immune state is unknown.
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Immune tolerance. The goat says to the
veterinarian, You are vaccinating me against
me! The goat is wrong, but recognized PLD and
other CL proteins as self.It is wellknown that
immunosuppressed animals and man may succumb to
other diseases. In addition, sheep goats
infected with CL do suffer accidents. Injections
lend towards hysteria in them or considerable
stress.
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The intoxicated and thus tolerized newborns soon
to be infected are not recognized by most
veterinarians who believe that skin abcesses and
swollen lymphatics are the main indicators of the
disease prevalence. This misdiagnosis encourages
vaccination campaigns with unresponsive animals.
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Eradication. PLD production in the
infected dam can be stopped by treatment with
penicillin G as formulated in some milk replacers
sometimes used to protect calves. Tetracycline is
a second choice by cost and oral administration.
However, treatment for elimination of CL has
never been tried on a respectable scale. When the
infected dam receives an antibiotic throughout
pregnancy, the fetus is not tolerized, and the
newborn will receive passive immunity from
colostrum and milk, i. e., is protected against
CL.
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Nonetheless, cabritos should have some access to
antibiotics in milk replacers. This has never
been seen in the field since often owners cannot
find such milk replacers even if they were
willing to pay for them. Again, the normal state
is assumed when the infected state is factual.
Mexican goatraisers are losing more than 10
millions of dollars a year, essentially because
the problem is unrecognized. The problem is
bacterial PLD production and all its attributes
including low level immune responses.
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Goats, a symbol of poverty, are raised in a
subsistance no-cost system, yet have a high labor
requirement, and expected facilities like a
watering trough can be missing in the barren
corrals. If by cost and lack of facilities, the
dams are not to be treated, the cabritos can be
by using an antibiotic milk replacer. One hundred
replaceable plastic nipples can be placed along a
large plastic pipe to hold the milk replacer (50
nipples on each side). This two-times per day
feeding system will save cabritos.
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Toxicosis again. Complete wipeouts with CL
deaths of all cabritos are recurrent events. Goat
owners usually do not keep records and soon
forget catastrophic animal losses that they
always accept fatalistically. Fatalism widens the
gap between traditional losses and technical
prevention. The last question is Who will pay
for prevention?
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The goat or sheep in repose may not be able to
get up, because of paralysis in the limbs and the
diaphragm, and very likely will die. This
condition is likely to be repiratory muscle
dysfunction. It cannot reach food or water. yet
may refuse them. Importantly, seasonal starvation
by drought or winter enter this panorama which of
course includes other infectious diseases and
common parasitoses.
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Erradication is the ultimate form of prevention
and depends on 1) longterm antibiotic treatment,
2) quarantine and 3) vaccination of competent
animals as well as veterinary monitoring of
ranches over perhaps several decades and
extending to millions of goats and sheep.
Clearly, erradication is both costly and slow,
likely radiating from some center that has been
freed of CL. However, it is crystal clear that
vaccinating unresponsive animals must fail to
prevent CL which is already subclinical in them.
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How to raise cabritos. The infected dams must
receive penicillin G to normalize their immune
status so that a passively immune cabrito is
obtained. The cabrito must be removed from its
mother at birth to enter a clean environment and
then to be raised on antibiotic milk replacer, if
it is retained by the ranch. At 1 month of age if
it has PLD neutralizing antitoxin, it can be
vaccinated with a killed vaccine (toxoide).
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In conclusion, CL should be recognized as a
paralyzing toxicosis rather than as a necrotizing
skin disease. It can be controlled or eliminated
by oral penicillin G, or other antibiotics.
Cabritos can be saved by giving them antibiotics
in milk replacers with but also without removing
them from their infected dams at birth. Vaccine
success depends on the immune response rather
than on the vaccine qualities. The cessation of
PLD production in the infected host allows the
antitoxin expression. Ongoing vaccine campaigns
as in Brazil are presumed to fail since all
others have, mainly because immune tolerance does
not allow protective host responses.