what to do when you encounter a new

8/14/2019 What to Do When You Encounter a New

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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


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


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


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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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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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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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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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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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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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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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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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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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?

what to do when you encounter a new

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