what to do when you encounter a new
TRANSCRIPT
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What to Do When YouEncounter a New Disease in
poultry flocks:
Dr.Kedar Karki
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Backgroumd
New diseases are potential threats impacting theeconomy of the poultry industry and ruralcommunities. Some come and go creating littleimpact while others have a significant effect. Most
affect breeders, either directly by reducingproductivity (decreased egg production, decreasedfertility, increased mortality, increased costs, poorchick viability or productivity, etc.),or indirectlythrough genetics, inadequate immunity, or vertical
transmission. New diseases occur with astonishingfrequency on average at least one new poultrydisease is described each year.
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new poultry diseases that have affected
the
industry during the past 25 years:
1. Turkey Coryza (Bordetellosis)
2. Avian Nephritis
3. Zoonotic Avian Influenza
4. Highly Virulent . Infectious BursalDisease Syndrome
5. Variant Inf. Bursal Disease6. Variant Infectious Bronchitis
7. Ornithobacterium rhinotracheale
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affected the
industry during the past 25 years:
8. Angara (Hydropericardium)
Disease
9. Runting Stunting Syndrome10. Chicken Infectious Anemia
11. Transmissible Viral
Proventriculitis12. Variant MG and MS Infections
13. Dermal Squamous Cell
Carcinoma
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affected the
industry during the past 25 years:
14. Myeloid Leukosis
15. Turkey Rhinotracheitis
16. Cryptosporidiosis
17. Spiking Mortality-Hypoglycemia
18. Very Virulent Mareks Disease
19. Pulmonary Hypertension Syndrome20. Big Liver and Spleen Disease
21. Salmonella enteritidis phage type 4
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affected the
industry during the past 25 years:
22. Equine Encephalitis Virus in
Turkeys
23. Stunting Syndrome in Turkeys
24. Poult Enteritis Mortality Syndrome
25. Multicentric Histiocytosis
26. Hepatitis-SplenomegalySyndrome
27. Turkey Osteomyelitis Complex
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Recognizing a New Disease
New diseases are most readily
recognized when disease
surveillance is already in place. We
are fortunate in Nepal to have an
excellent and virtually no-cost
diagnostic service available to the
poultry industry, which makes diseasesurveillance readily available through
Bird flu surveillance.
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Recognizing a New Disease
New diseases will be seen by the
grower initially, service person, farm
manager or other person who
interacts on a continuous basis with
the birds.
Experience and training will help the
individual to recognize that a newdisease may have occurred.
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Recognizing a New Disease
New diseases will be different insome way from diseases that haveoccurred previously.
They can be an emerging disease(truly new) or a re-emerging disease(a variation of a known disease).
Recognizing how a disease isdifferent from what is known isessential to identifying a new disease.
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Steps to be Taken
1) Is the problem really a new disease
or is it a known disease? Careful and
complete diagnostic workups of
affected flocks will help to determinethis question. It is important to
consider management and
environment as well as search forinfectious agents.
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Steps to be Taken
2)The new disease needs to be
described, defined, and named to
make communication possible.
What are the salient features of the
new disease that distinguish it from
previously known diseases?
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Steps to be Taken
3) An epidemiologic study needs to
be done. In most situations,
something has been changed to
permit the new disease to emerge orre-emerge. What is different now from
when the disease was not occurring?
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Types of New Diseases
a) Well-known classical diseases in
unusual situations. Either a previously
known disease occurs in a different
class of poultry or in a geographicarea where it has not occurred
previously. This includes the
introduction of foreign diseases suchas exotic Newcastle disease or Highly
Pathogenic Avian Influenza
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Types of New Diseases
b) Production diseases. Mosteconomic loss from disease in poultryflocks results from a failure of the bird
to achieve its genetic potential, i.e.,morbidity, and not from outright death(mortality). Collectively these ill-defined diseases that adversely affect
production are called productiondiseases to differentiate them fromclassical diseases with known cause
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Types of New Diseases
c) Polymicrobial diseases. Few diseases
result solely from the effects of a single
agent. In most instances there is a primary
pathogen, which initiates the diseaseprocess, and opportunistic microbes or
non-infectious factors that complicate or
intensify the clinical severity of the
condition. Polymicrobial diseases require atleast two infectious agents for the disease
to occur.
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Types of New Diseases
d) Emerging and reemerging diseases.Infectious agents are constantly interactingwith their host(s) in the process ofadaptation and with each other to form new
organisms through transfer of geneticmaterial.
Coinfection of a bird with two similarviruses can result in a recombinant viruswith properties of both viruses, effectivelyresulting in a new virus.Variants also result from mutations duringreplication.
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Emerging and reemerging diseases
In fact the mutation rate in coronaviruses isso high that it is unlikely that any two virusparticles have completely identicalgenomes. For virologists, evolution is adaily reality not a theory, according toDr. M. C. Horzinek (2000). Fortunatelymost genetic variants do not develop intounique pathogens or vary significantly from
the original virus, however, the few that dobehave differently can be the cause of anemerging or reemerging disease.
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Types of New Diseases
e) Diseases that jump from anotherspecies. Another means by which aninfectious agent acquires newcharacteristics is when it adapts to a new
host. Several pathogens spread betweendifferent avian species, most notablyviruses such as avian adenovirus type 3,avian influenza viruses, avianmetapneumoviruses, and Newcastle
disease virus that commonly infectwaterfowl with little or no effect, to poultryin which they cause clinical disease.
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Diseases that jump from another
species.
Spread between mammals and
poultry is less common although it is
well recognized that influenza viruses
common to pigs can cause egg-dropsand mortality in turkeys and avian
influenza viruses can infect people,
occasionally with fatal results.
T bl 1 Ch t i ti f
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Table 1. Characteristics of
production and classical diseases.
Usuallypresent
and readily
recognized
Not present or mild
and not
considered
significant
ClinicalSigns
Simple, usually one,
or lescommonly, two
agents; may b
infectious or non-
infectious
Complex,
multifactorial,interactions between
noninfectious
& infectious factors
Cause
ClassicalDisease
Production Disease
Ch t i ti f d ti d
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Characteristics of production and
classical diseases.
Typical
lesions
usually
present
Not
present or
mild and
nonspecifi
Pathology
Variable,
butusually
present
Typically
nil to low
Mortality
Classical
Disease
Productio
n Disease
Ch t i ti f d ti d
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Characteristics of production and
classical diseases.
Often possible,
moderate to high
success
Rarely possible, often
too late,
usually of little valueTreatment
Signs, lesions
recognized, ID ofcause; deductive
(many findings
lead to specific
cause)
Production below
geneticpotential; inductive
(few findings
lead to generalities
about flock)
Diagnosis
ClassicalDisease
Production Disease
Ch t i ti f d ti d
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Characteristics of production and
classical diseases.
Generally easy to
experimentally
reproduce; proven by
Kochs
postulates
Difficult to
impossible to
experimentally
reproduce and
confirm; proven byEvans
Experimental
Reproduction
Vaccines and
medications often
useful
Requires high
biosecurity,
excellent
management, very
good nutrition
Preventio
n/
Control
ClassicalDisease
Production Disease
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Characteristics of production and
classical diseases.
Natural or
experimental
disease,
emphasis on
microbiology,
pathology,
toxicology, etc.
In flocks on farms,
good records
essential, emphasis
on
population medicine,
epidemiology, etc.
Methods
of
Study
ClassicalDisease
Production Disease
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Getting Help?
To minimize the impact of newdiseases, early detection and controlare essential.
Unlike the situation with emerginghuman diseases, there exists nocomprehensive systematicinvestigative approach to quicklyidentify and combat new food animaldiseases.
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Getting Help?
The current approach is fragmented
and dependent on individual
production companies and individual
researchers, which often results in anuncoordinated effort that can result in
severe economic losses due to
delays in recognition and control ofthe disease.
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Getting Help?
Health care for poultry can be thought
of as a three-tier system that mirrors
health care for people. Primary health
care, provided at the flock or complexlevel, is analogous to that provided by
the family physician. Individuals
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Getting Help?
Individuals within the company,
consultants, or extension personnel
handle the day-to-day health issues
including preventative healthprograms.
Often this is a poultry veterinarian
assisted by the service people whovisit flocks and complex managers.
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Getting Help?
Unfortunately, primary care for
poultry, which is when a possible new
disease would initially be recognized,
continues to decrease. The numberof poultry veterinarians working in
production has decreased even
though live production has increased.
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Getting Help?
Poultry veterinarians also have
increased responsibilities that may
span breeders to processing plants or
a number of complexes in differentgeographic areas, and regulatory or
other governmental duties that can
consume considerable time andprevent attention being given to bird
health.
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Getting Help?
Medical specialists, following referral
of a patient from the primary
physician, provide secondary health
care for people.
Veterinary diagnosticians provide
secondary health care for poultry
following submission of affected birdsto a diagnostic laboratory.
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Getting Help?
The number of diagnostic labs,
diagnosticians, and capabilities of the
labs continues to decrease, even in
areas where poultry production issignificant.
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Getting Help?
An important aspect for controlling new
diseases is partnerships between local
government, academia, and industry.
No one group alone has the requisiteresources needed to identify and control a
new disease. These relationships are best
established and maintained prior to a new
disease problem occurring.
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Getting Help?
Poultry extension personnel play a
key role in the identification of
possible new diseases.
They span all levels of health care
and connect companies that have a
potentially new disease problem with
resources, secondary and/or tertiary,that can help solve the problem.
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Getting Help?