AVIAN POX
Avian pox is a relatively slow-spreading viral
disease in birds, characterized by wart-like
nodules on the skin and diphtheritic necrotic
membranes lining the mouth and upper
respiratory system. It has been present in birds
since the earliest history. Mortality is not usually
significant unless the respiratory involvement is
marked. The disease may occur in any age of
bird, at any time.
Avian pox is caused by a virus of which there are
at least three different strains or types; fowl pox
virus, pigeon pox virus and canary pox virus.
Although some workers include turkey pox virus
as a distinct strain, many feel that is identical to
fowl pox virus.
Each virus strain is infective for a number of
species of birds. Natural occurring pox in
chickens, turkeys and other domestic fowl is
considered to be caused by fowl pox virus.
Fowl pox can be transmitted by direct or
indirect contact. The virus is highly resistant in
dried scabs and under certain conditions may
survive for months on contaminated premises.
The disease may be transmitted by a number of
species of mosquitoes. Mosquitoes can harbor
infective virus for a month or more after feeding
on affected birds. After the infection is
introduced, it spreads within the flock by
mosquitoes as well as direct and indirect
contact. Recovered birds do not remain carriers.
Since fowl pox usually spreads slowly, a flock
may be affected for several months. The course
of the disease in the individual bird takes three
to five weeks. Affected young birds are retarded
in growth. Laying birds experience a drop in
egg production. Birds of all ages that have oral
or respiratory system involvement have difficulty
eating and breathing. The disease manifests
itself in one or two ways, cutaneous pox (dry
form) or diphtheritic pox (wet form).
Dry pox starts as small whitish foci that develop
into wart-like nodules. The nodules eventually
are sloughed and scab formation precedes final
healing. Lesions are most commonly seen on the
featherless parts of the body (comb, wattles, ear
lobes, eyes, and sometimes the feet).
Wet pox is associated with the oral cavity and
the upper respiratory tract, particularly the
larynx and trachea. The lesions are diphtheritic
in character and involve the mucous membranes
to such a degree that when removed, an
ulcerated or eroded area is left.
Fowl pox is readily diagnosed on the basis of
flock history and presence of typical lesions. In
some cases, laboratory diagnosis by tissue or
transmission studies is necessary.
There is no treatment for fowl pox. Disease
control is accomplished best by preventative
vaccination since ordinary management and
sanitation practices will not prevent it. Several
kinds of vaccines are available and are effective
if used properly.
Vaccination of broilers is not usually required
unless the mosquito population is high or
infections have occurred previously. The chicks
may be vaccinated as young as one day of age by
using the wing-web method and using a one
needle applicator. All replacement chickens are
vaccinated against fowl pox when the birds are
six to ten weeks of age. One application of fowl
pox vaccine results in permanent immunity.
Newcastle Disease
Newcastle disease is a contagious viral infection
causing a respiratory nervous disorder in
several species of fowl including chickens and
turkeys. Different types or strains of the virus
(varying in their ability to cause nervous
disorder, visceral lesions and death) have been
recognized.
The most severe strain is called viscerotropic
velogenic Newcastle disease (VVND) and is kept
from birds in the U.S. by enforcement of strict
quarantines at our national borders. It is often
referred to as "Exotic Newcastle Disease" and
infection of susceptible fowl with this form
usually causes high mortality. Due to the
reduced chance that poultry in this country will
become infected with this disease form, it will
not be discussed.
A milder form of the disease is called
"mesogenic" Newcastle disease and is the most
serious strain found in the U.S. This is the form
that is referred to as Newcastle disease in this
discussion.
Newcastle disease is highly contagious. All birds
in a flock usually become infected within three
to four days. The virus can be transmitted by
contaminated equipment, shoes, clothing and
free-flying birds. During the active respiratory
stage, it can be transmitted through the air. The
virus is not thought to travel any great distance
by this method. Recovered birds are not
considered carriers and the virus usually does
not live longer than thirty days on the premises.
Signs of Newcastle disease are not greatly
different from those of other respiratory
diseases. The signs most frequently observed are
nasal discharge, excessive mucous in the
trachea, cloudy air sacs, casts or plugs in the air
passages of the lungs and cloudiness in the
cornea of the eye.
The disease in young chickens begins with
difficult breathing, gasping and sneezing. This
phase continues for ten to fourteen days and
may be followed by nervous symptoms. If
nervous disorders develop, they may consist of
paralysis of one or both wings and legs or a
twisting of the head and neck. The head often is
drawn over the back or down between the legs.
Mortality may vary from none to total loss of the
flock.
In adult chickens, respiratory symptoms
predominate. Only rarely do nervous disorders
develop. If the flock is laying, egg production
usually drops rapidly. When this occurs, it takes
four weeks or longer for the flock to return to
the former production rate. During the
outbreak, small, soft-shelled, off-colored and
irregular-shaped eggs are produced. Mortality
in adult birds is usually low but may be fairly
high from some virus strains.
In turkeys, the symptoms are usually mild and
may be unnoticed unless nervous disorders
develop. During an outbreak, turkeys will
produce eggs with a chalky white shell. Reduced
production in breeder flocks is the main
economic loss from this disease in turkeys.
The flock history, signs of a respiratory nervous
disorder and other typical lesions often may be
sufficient to allow a tentative diagnosis. Usually,
however, the disease cannot be differentiated
from infectious bronchitis and some of the other
respiratory infections, except by laboratory
methods.
Vaccination is practiced widely and is the
recommended method for prevention. Several
types of vaccines are available but the most
successful and widely used is the mild live virus
vaccine known as the B 1 and La Sota types. The
vaccines may be used by drops into the nostril
or eye, addition to the drinking water or applied
in spray form.
Broiler chickens are usually vaccinated when
seven to ten days of age. Chickens kept for egg
production are usually vaccinated at least three
times. The vaccine is given when birds are
approximately seven days, again at about four
weeks and a third time at about four months of
age. Revaccination while in lay is commonly
practiced.
Vaccination is not widely used in turkeys. It is
used to protect egg producing breeder flocks.
One dose of the mild type vaccine is given after
selecting breeder birds.
There is no treatment for Newcastle disease. The
disease does not always respect even the best
management programs, but good "biosecurity"
practices will help reduce the possibility of
exposure to Newcastle disease virus.
Infectious Bronchitis
Infectious bronchitis is an extremely contagious
respiratory disease of chickens characterized by
coughing, sneezing and rales (rattling). It is
caused by a virus that affects chickens only.
Other fowl or laboratory animals cannot be
infected with this virus. Several distinct strains
of the virus exist.
Infectious bronchitis is considered the most
contagious of poultry diseases. When it occurs,
all susceptible birds on the premises become
infected, regardless of sanitary or quarantine
precautions. The disease can spread through the
air and can "jump" considerable distances
during an active outbreak. It can also be spread
by mechanical means such as on clothing,
poultry crates and equipment. The disease is not
egg transmitted and the virus will survive for
probably no more than one week in the house
when poultry are not present. It is easily
destroyed by heat and ordinary disinfectants.
The infection is confined to the respiratory
system. Symptoms are difficult breathing,
gasping, sneezing and rales. Some birds may
have a slight watery nasal discharge. The
disease never causes nervous symptoms. It
prevails for ten to fourteen days in a flock and
symptoms lasting longer than this are from some
other cause.
In chickens under three weeks of age, mortality
may be as high as thirty or forty percent. The
disease does not cause a significant mortality in
birds over five weeks of age. Feed consumption
decreases sharply and growth is retarded.
When infectious bronchitis occurs in a laying
flock, production usually drops to near zero with
a few days. Four weeks or more may be required
before the flock returns to production. Some
flocks never regain an economical rate of lay.
During an outbreak, small, soft-shelled,
irregular-shaped eggs are produced.
Infectious bronchitis is difficult to differentiate
from many of the other respiratory diseases. For
this reason, a definite diagnosis usually requires
a laboratory analysis.
Infectious bronchitis is highly contagious and
does not always respect sanitary barriers.
Vaccinate chickens being retained as layers.
Whether broilers should be vaccinated depends
upon many factors and is an individual decision.
Numerous vaccines are available commercially.
Most of them represent a modified or selected
strain of the infectious bronchitis virus. The
vaccine used should contain virus known to be
present in the area. All vaccines contain live
virus and those that give the best protection are
also capable of producing symptoms and
reducing egg production. The vaccine virus will
spread to other susceptible birds. Vaccine is
usually added to the drinking water, but may be
dropped into the eye or nostril or used as a
spray.
There is no treatment for this disease. In young
chickens it is helpful to increase the brooder
temperature and provide as nearly ideal
environmental conditions as possible.
Quail Bronchitis
Quail bronchitis is a contagious, highly fatal
disease in young bobwhite quail. The virus
causing this disease also infects chickens and
turkey. This agent is also known as a CELO
(Chick Embryo Lethal Organism) virus. It has
been isolated from chicken eggs but does not
produce a recognizable disease in chickens or
turkeys. This agent may play a part in
respiratory diseases and in infertility problems,
but its importance must be established by
additional research. It is important because it is
one of the agents that may be isolated from birds
with respiratory symptoms and is difficult to
separate from other agents such as infectious
bronchitis virus.
Lymphoid Leukosis
Characteristically, lymphoid leukosis is a disease
of adult chickens; however, the disease appears
to be increasing in importance for turkeys and
game birds. Although the virus of lymphoid
leukosis can produce various responses (blood,
bone, lymph), the lymphoid tumor response is
the most common.
The disease is transmitted in a variety of ways.
The causative viral agent is passed out of the
body of infected birds via eggs and feces. The
virus may be transmitted mechanically from
infected birds to susceptibles by blood-sucking
parasites or by man in such procedures as fowl
pox vaccination.
Lymphoid leukosis characteristically produces
lymphoid tumors, particularly in the liver and
spleen. The tumors may also affect other visceral
organs such as ovary and lungs. Affected birds
may die without preliminary symptoms, but the
disease usually is chronic in nature and affected
birds show loss of appetite, progressive
emaciation and diarrhea. Clinically affected
birds invariably die. Losses due to the disease
are most severe shortly after onset of egg
production, but losses will continue for as long
as the flock is retained. Total loss may approach
twenty percent during the life of a flock.
Clinical diagnosis of lymphoid leukosis is based
upon flock history and disease manifestations.
The lymphoid disease cannot be readily
distinguished from the visceral response to
Marek's disease; however, there are some
features that aid in differential diagnosis.
There is no treatment for lymphoid leukosis.
Although the disease cannot be prevented
completely, there are certain steps that can be
taken to help control the level of infection within
a flock. Some steps are:
Buy resistant strains of birds since genetic
resistance is a deterrent,
Brood in isolation and do not mix birds of
different ages, especially through six weeks of
age,
Keep the incubator clean and disinfected,
Control blood-sucking parasites,
Good care, limiting stress, and adequate ration
will be of benefit.
Marek's Disease (Visceral Leukosis)
Marek's disease is characteristically a disease of
young chickens but older birds can also be
affected. In contrast to the lymphoid leukosis
tumor response, Marek's disease may be
observed in more diverse locations.
Marek's disease is caused by a virus belonging
to the Herpes virus group. Much is known about
the transmission of the virus; however, it
appears that the virus is concentrated in the
feather follicles and shed in the dander
(sloughed skin and feather cells). The virus has a
long survival time in dander since viable virus
can be isolated from houses that have been
depopulated for many months.
The usual mode of transmission is by aerosols
containing infected dander and dust. Young
birds are most susceptible to infection by
Marek's disease; however, since the incubation
period is short, clinical symptoms can appear
much earlier than in the case with lymphoid
leukosis.
Marek's disease may produce a variety of clinical
responses, all lymphoid in character. These are
acute visceral, neural, ocular, skin or
combinations of the responses that can be seen.
Marek's of the visceral type is characterized by
widespread involvement with lesions commonly
seen in gonads, liver, spleen, kidney and
occasionally heart, lungs and muscles. The
disease is often acute, with apparently healthy
birds dying very rapidly with massive internal
tumors. The disease may appear in broiler-age
birds but the most severe losses occur in
replacement pullet flocks prior to onset of egg
production.
The neural type of Marek's is typified by
progressive paralysis of the wings, legs and
neck. Loss of body weight, anemia, labored
respiration and diarrhea are common symptom.
If lesions are present, they are confined to the
nerve trunks and plexes enervating the
paralyzed extremities. Frequently no gross
lesions can be observed.
Ocular (eye) leukosis or "gray-eye" is usually
seen in early maturity. Morbidity and mortality
are usually low but may approach twenty-five
percent in some flocks. It is characterized by the
spotty depigmentation or diffuse graying of the
iris in the eye. The pupil develops an irregular
shape and fails to react to light. Emaciation
diarrhea and death follow.
Skin leukosis produces the most severe losses in
broilers. The losses result from high
condemnations at the processing plant.
Enlargement of the feather follicles due to
accumulations of lymphocytes is the typical
lesion. This is the most infective virus since it is
produced in the regions of the feather follicles
and is shed with the skin dander.
Acute Marek's disease can be extremely rapid in
its course, producing mortality in apparently
healthy birds. However, in some cases the
lesions may regress and clinically affected birds
may make complete recoveries.
Diagnosis is based upon flock history and
disease manifestations. Accurate diagnosis may
depend on results of laboratory procedures. As
is the case with lymphoid leukosis, there is no
treatment for Marek's disease.
A vaccine is available that is extremely effective
(90% +) in the prevention of Marek's disease. It
is administered to day-old chickens as a
subcutaneous injection while the birds are in
the hatchery. Use of the vaccine requires strict
accordance with manufacturer's
recommendations in a sterile environment.
Infectious Bursal Disease (Gumboro)
Infectious bursal disease is an acute, highly
contagious viral disease of young chickens. It is
most often found in highly concentrated poultry
producing areas. It causes marked morbidity
and mortality in affected flocks. Although the
disease causes severe losses, its affect on
reducing the bird's ability to develop immunity
to other diseases may be the most serious effect
produced by this disease.
The transmission or spread of the disease can
occur by direct contact (bird to bird),
contaminated litter and feces, caretaker,
contaminated air, equipment, feed, servicemen
and possible insects and wild birds. It is
extremely contagious.
Birds have ruffled feathers, a slight tremor at
onset of the disease, strained defecation, loss of
appetite and are dehydrated. Affected birds
have a tendency to sit and when forced to move,
have an unsteady gait. Vent picking is common
and a whitish diarrhea frequently develops. A
sudden rise in body temperature is followed by a
drop to subnormal temperature, prostration and
death. Birds surviving the initial infection will
recover rapidly within two weeks.
Postmortem lesions include dehydration and
changes in the bursa, skeletal muscle, liver and
kidneys. All affected birds have bursal changes
characterized by swelling, change in shape
(oblong), color (pink, yellow, red, black) and the
formation of a gelatinous film around the bursa.
Within a few days the bursa shrinks to half its
normal size or smaller.
Diagnosis of infectious bursal disease is based on
flock history and postmortem lesions. Laboratory
procedures may be used to substantiate the
diagnosis.
Vaccines are available but must be carefully
used. If given correctly, good immunity can be
developed. There is no specific treatment for
infectious bursal disease and indiscriminate
medication with certain drugs may severely
aggravate mortality. Supportive measures such
as increasing heat, ventilation and water
consumption are beneficial.
.......#source http://msucares.com/poultry/diseases/disviral.htm
