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Anthrax in Farm Animals
Michael
D. Piontkowski, DVM
Senior Staff Veterinarian
Technical Service
This
time of the year, we receive a lot of calls concerning anthrax
infection and vaccination for anthrax. Because this topic is
on a lot of people's mind, I thought it would be helpful to
reprint a recent article by Dr. Charles L. Stoltenow,
Extension Veterinarian for North Dakota State University. Dr.
Stoltenow has written an excellent review of Anthrax and has
graciously given Colorado Serum Company permission to reprint
this article.
North Dakota State University
NDSU Extension Service
Anthrax
A-561 (Revised) December 2000
Charles L. Stoltenow, DVM -- Extension Veterinarian
Anthrax occurs worldwide and is associated
with sudden death of cattle and sheep. Anthrax can infect all
warm-blooded animals, including man.
The anthrax organism (Bacillus
anthracis) has the ability to form spores and become
resistant to adverse conditions. Anthrax organisms in animals
or their secretions may be destroyed by pasteurization or
ordinary disinfectants. However, if the animal carcass is
opened and the organisms are exposed to air, they will form
spores. Sporulated anthrax organisms are highly resistant to
heat, cold, chemical disinfectants and drying. The anthrax
spore may live indefinitely in the soil of a contaminated
pasture or yard.
Herbivores — particularly cattle and sheep — are
susceptible to anthrax. Horses, swine, deer, and humans are
less susceptible than cattle or sheep. Wild ruminants such as
deer may also become infected. Dogs, cats, and birds have been
infected experimentally.
Sources of Infection
Outbreaks typically occur when livestock are grazing on
neutral or slightly alkaline soil. Infection in cattle, sheep,
or horses usually is the result of grazing on infected pasture
land. The organisms usually enter through the mouth, and less
often via nose or skin injury. Following ingestion or
inhalation, the organisms spread rapidly throughout the entire
body.
Dead animals that are opened and not
burned or buried provide an ideal source of the organism. It
is imperative that diseased carcasses be cremated (burned to
ashes) or buried deep and covered with quick lime before
covering with soil. Quick lime is Calcium Oxide (CaO) and
should be used with extreme care. Quick lime will react
quickly with water and form a calcium hydrate (CaO + H2O
Þ Ca(OH2)). Quick lime pulls water from plants,
bacteria, fungi and any other living organism.
Anthrax spores may also spread by flooding
pastures with contaminated water or dumping infected carcasses
in streams or ponds. Low lying ground or marshy areas are
readily contaminated by flooding, and resultant stagnant water
holes may serve as a source of infection. Hay that is infested
with spores may account for outbreaks of acute anthrax during
the winter months. However, anthrax is predominantly a warm
weather disease and is rarely diagnosed in North Dakota during
the winter.
It is best to use soil infected with the
anthrax organism to raise cultivated crops. Anthrax spores are
known to survive in the soil 100 years or longer.
Anthrax may also be spread through wounds
caused by blood sucking insects, dehorning, or castration.
Outbreaks have occurred because of contaminated feed,
particularly through bone meal, meat scraps, and other animal
protein products. Present regulations pertaining to
manufacture and importation of such animal products virtually
eliminate these as a source of infection.
Humans may become infected by handling
contaminated hides or wool, or by examining infected
carcasses.
Symptoms
Symptoms associated with anthrax depend to a certain degree on
the species involved and the route of infection. When the
anthrax organism enters the animal's body by mouth or
nostrils, the symptoms occur soon after infection (acute form)
followed rapidly by death. When infection takes place through
the skin because of injury or insect bites, it appears
localized at the site of injury in the initial stage.
The affected area is initially hot and
swollen, and becomes cold and insensitive. Later, the
infection can become generalized.
Anthrax usually is a fatal disease with no
symptoms observed. Upon or near death, blood oozes from the
body openings. This blood is heavily laden with anthrax
organisms. There is a marked bloating and rapid decomposition
of the carcass.
If the infection is less acute, there may
be a sudden staggering, difficult breathing, trembling,
collapse, and death. In horses, colic may be observed. Edema
and swelling may be seen over the body, particularly at the
brisket. Illness is observed for one or two days, but it may
last five days; symptoms are preceded by fever, with a period
of excitement in which the animal may charge anyone nearby.
This is followed by depression in cattle or sheep.
Sometimes the anthrax organism localizes
itself in the throat area. The tongue, throat, and neck are
extremely swollen and a frothy blood-tinged discharge comes
from the mouth. Though this is the typical form of anthrax
observed in swine, it may also occur in cattle and sheep.
Diagnosis of Anthrax
Not all cases of "sudden death" are anthrax, but if
anthrax is suspected, confirmatory laboratory examination is
needed.
If anthrax is suspected, do not perform a
necropsy. Using aseptic technique, have a veterinarian collect
a jugular sample of venous blood and send or deliver it to the
diagnostic laboratory in a sealed, sturdy, leakproof, iced
container, with an accompanying history identifying it as an
anthrax suspect.
Treatment and Control
Anthrax is highly fatal and it is difficult to treat affected
animals. Long acting penicillin is the antibiotic of choice.
Response to treatment may vary; best results are obtained when
drugs are administered early during an outbreak. If
antibiotics are used, vaccination with an anthrax vaccine
should be delayed for one to two weeks. The vaccine is a
modified-live bacterin and antibiotics will kill or neutralize
the vaccine.
An effective vaccine is available
(non-encapsulated, Sterne 34F2 strain). Since anthrax is a
reportable disease, details on use of the vaccine should be
coordinated through the Office of the State Veterinarian. It
is relatively safe and provides effective protection on most
species of livestock. Use caution when administering to goats
and llamas; cases have been reported of the vaccine actually
causing the disease in these species.
If the anthrax vaccine is used, all label
directions must be followed for proper withdrawal times
including withholding of milk and meat products from the
market.
Disposal
The carcass and all materials associated with the carcass
should be destroyed and the ground should be disinfected. This
can be very difficult. The preferred method of destruction
would be incineration of the carcass. Burying the carcass deep
(at least 6 feet) and covering with quick lime is still
acceptable.
The following are general recommendations
for burning a 1000 pound carcass: a pit about 2 feet deep and
exceeding the length and breadth of the carcass by about 1
foot on each side is dug. A 1 foot by 1 foot trench is dug
along the length of the center of the pit extending beyond the
ends of the pit by about 3 feet; this serves as an air duct
for the fire under the carcass. The trench is filled and the
bottom of the pit is covered with straw and soaked with
accelerant (kerosene or diesel fuel).
Heavy timbers such as railroad ties cut to
fit across the trench and within the sides of the pit are
placed on top of the straw. Other pieces of wood (or coal) are
added until the pit is filled to level with the ground
surface. This is all saturated with accelerant.
The carcass can then be lifted or drawn
onto the pyre. Further accelerant is poured over the carcass.
The fire is ignited at either end of the trench. Once the
incineration is well underway (probably after the first hour),
the pyre should be covered with corrugated metal or other
metal sheeting to retain heat but not lose ventilation.
If the ground and material under the
animal are contaminated by blood and body fluids, it is
preferable that this be incinerated as well. Soil should be
removed deep enough to contain blood and body fluids, and this
could be up to 6 inches. This material can be placed on top of
the carcass prior to ignition of the pyre.
The approximate quantities of fuel that
will be needed are 50 pounds of straw, 2½ gallons of
accelerant, and 2 tons of wood or ½ ton of wood and ½ ton of
coal.
If soil and other related materials cannot
be incinerated, it can be disinfected with 5 percent
formaldehyde solution at 50 quarts per square yard.
Personnel Protection
If anthrax is suspected, aseptically collect a jugular blood
sample for culture. DO NOT NECROPSY THE ANIMAL.
Producers should take every precaution to
avoid skin contact with the potentially contaminated carcass
and soil. Protective, impermeable clothing and equipment such
as rubber gloves, rubber or leather apron, and rubber boots
with no perforations should be used. No skin, especially that
which is compromised with wounds or scratches, should be
exposed. Disposable personal protective equipment is
preferable, but if not available, decontamination can be
achieved by washing any exposed equipment in hot water and
detergent. Disposable personal protective equipment should be
burned and buried with the carcass.
The Bacillus anthracis organisms
range from 0.5-5.0 um in size. Veterinarians and producers
working with anthrax suspects or confirmed cases should wear
respiratory equipment capable of filtering this size of
particle. A National Institute for Occupational Safety and
Health (NIOSH) and Mine Safety and Health Administration (MSHA)
approved high efficiency-respirator, such as a half-face
disposable respirator with a high-efficiency particulate air (HEPA)
filter, is recommended when conducting soil remediation and
burial and when applying quicklime to soil.
Human Implications
Anthrax is a zoonotic disease (disease that can affect both
man and animals). Anthrax in humans can take three forms:
cutaneous, respiratory, and intestinal.
The cutaneous or skin form occurs when
anthrax spores invade a cut or abrasion. Initially the site
will itch followed by swelling and discoloration of the
affected area. Pain is not usually present. If left untreated,
cutaneous anthrax can eventually become septicemic and lead to
death. Antibiotic therapy is very effective for the cutaneous
form of anthrax.
The respiratory form of anthrax occurs
when the spores are inhaled and then infect the lung tissue.
Initial symptoms are mild and may resemble having the flu or
common cold. The disease will progress at a rapid rate with
shock developing within three to five days, followed shortly
by death. Once shock has developed, any therapy is met with
limited success.
The intestinal form of anthrax occurs when
spores are ingested, primarily through ingesting contaminated
meat. It is a very rare condition and almost always involves
an explosive foodborne outbreak where many individuals are
involved. These cases are usually reported from underdeveloped
countries where dead animal carcasses are sometimes salvaged
for human food. Symptoms include fever, abdominal distress,
shock, and death.
Regulation Pertaining to the Control of
Anthrax
NDCC § 36-14-19.
Disposition of carcass of animal dying from contagious or
infectious disease.
Any animal that is found dead must be
presumed to have died from a contagious or infectious disease
until the contrary is shown unless another cause of death is
apparent. The owner or person in charge of any domestic animal
or nontraditional livestock that dies within this state from
or on account of any contagious or infectious disease shall
dispose of the carcass of such animal as follows:
-
If the animal died of anthrax, as
determined by a licensed veterinarian, the carcass must be
completely burned at the place where it died if possible.
If the carcass must be moved, it may not be dragged over
the ground but must be moved only on a suitable conveyor
and all body opening in the carcass must be plugged with
cotton saturated with a strong antiseptic solution.
NDCC §
48-04-01-08.
Control of Anthrax.
All livestock
on farms where anthrax has been diagnosed shall be vaccinated.
All animals shall be quarantined for thirty days after the
death of the last animal or thirty days following vaccination.
Sale of hides removed from animals infected with anthrax is
prohibited.
Anthrax --
A-561 (Revised) December 2000
NDSU Extension
Service, North Dakota State University of Agriculture and
Applied Science, and U.S. Department of Agriculture
cooperating. Sharon D. Anderson, Director, Fargo, North
Dakota. Distributed in furtherance of the Acts of Congress of
May 8 and June 30, 1914. We offer our programs and facilities
to all persons regardless of race, color, national origin,
religion, sex, disability, age, Vietnam era veterans status,
or sexual orientation; and are an equal opportunity employer.
This publication will be made available in alternative formats
for people with disabilities upon request, 701/231-7881.
North Dakota
State University
NDSU Extension Service
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