Diseases of Poultry - APSC 301
Diseases of Poultry
Monitoring Poultry Health
Healthy birds are critical for profitability, while unhealthy birds can lead to financial losses.
Animal health programs play a significant role in reducing mortality and poor performance.
Historical context: In the 1920s, poultry mortality was approximately 18%. By the 1970s, this number had decreased to around 5%.
Current statistics indicate that in the broiler industry, mortalities run approximately 5% throughout the growing period, with increases beyond this threshold indicating potential health issues.
Key Concepts in Poultry Diseases
Definition of Disease
Disease is defined as any departure from normal health.
Symptoms: Manifestations of diseases known as signs or symptoms, with two categories:
General symptoms include loss of appetite, droopiness, diarrhea, and a drop in egg production.
Specific symptoms can include flaccid paralysis associated with botulism.
Lesions and Etiology
Lesions refer to visible changes in size, shape, color, or structure of an organ.
Etiology is the study of the cause of disease.
Virulence or pathogenicity: Refers to the ability of an organism to cause disease in its host.
Monitoring Mortality
Abnormal signs indicating health issues may include the following rules of thumb:
More than 1% of birds being sick at one time signals concern.
During the first three weeks of life, mortality losses for chicks usually average around 2%, while for turkey poults, it can be approximately 1% higher.
After three weeks, mortality should not exceed 1% per month.
Normal Physiological Indicators
Key physiological indicators to monitor include:
Normal feed and water consumption.
Normal growth/egg production rates.
Normal appearance of droppings.
Physiological measurements, including:
Temperature: 106°F
Pulse: 200-400 beats per minute
Breathing: 15-36 breaths per minute
General sounds and activity levels of birds should also be assessed:
Comparison to signs of illness such as droopiness and ruffled feathers is important.
Multifactorial Nature of Disease
Disease typically arises from a combination of factors:
Indirect or predisposing factors:
These lower the resistance of birds and include stress factors such as overcrowding, poor ventilation, inadequate feed, and water.
Direct factors:
Caused by infectious or non-infectious factors.
Infectious vs Non-Infectious Diseases
Infectious diseases can be contagious or non-contagious:
Contagious diseases are readily transmitted among individuals or flocks and pose the greatest threat to poultry health.
Infectious diseases arise from living organisms, which include bacteria, viruses, fungi, and more.
Transmission of Disease in Poultry
Modes of infection spread include:
Carrier birds.
Other animals such as rodents and insects.
Airborne transmission or contact with contaminated materials.
Egg transmission.
Failure to properly dispose of carcasses from dead birds.
Contaminated shoes and clothing.
Introduction of diseased birds into a flock and incorporating healthy birds that are carriers.
Contaminated feed, feed bags, soil, litter, insects, and impure water.
Prevention and Control Programs
Components of effective prevention and control strategies include:
Development of a flock health program and biosecurity measures.
Management and sanitation at hatcheries.
Use of disinfectants.
Application of antibiotics and coccidiostats as required.
Vaccination practices.
Involvement of veterinarians and diagnostic laboratories.
Planned responses to disease outbreaks.
Avian Immune System
Immunity is defined as the ability to resist infection.
Two types of protective mechanisms:
Innate or natural immunity:
Mechanisms that prevent or hinder the invasion of microorganisms, including skin and mucous membranes.
Acquired or specific immunity:
Mechanisms that combat pathogens that invade the body, such as white blood cells and antibodies.
Lymphoid Tissues
Primary lymphoid tissues include:
Thymus: Located in the neck where T immune cells, responsible for cell-mediated immunity, originate.
Bursa of Fabricius: Located dorsal to the cloaca where B immune cells, responsible for humoral or antibody-mediated immunity, originate.
Secondary lymphoid tissues (where both B & T cells are present):
Spleen (located adjacent to the liver).
Lymph nodes.
Harderian gland (close to the eyeballs).
Peyer's patches (located near the junction of the ileum and ceca).
Meckel’s diverticulum (remnants of the yolk stalk).
Causes of Avian Diseases
Avian diseases can result from the following:
Pathogenic microorganisms, including viruses, bacteria, fungi, protozoa, and parasites.
Non-pathogenic factors such as nutritional deficiencies, genetics, metabolic issues, environmental factors, and behavioral problems.
Poultry Diseases Caused by Bacteria
Notable bacterial diseases include:
Botulism
E. coli infection
Necrotic enteritis
Erysipelas
Fowl cholera
Fowl typhoid
Pullorum disease
Infectious coryza
Ulcerative enteritis
Mycoplasma infections
Omphalitis
Poultry Diseases Caused by Viruses
Notable viral diseases include:
Fowl pox
Infectious bronchitis
Quail bronchitis
Infectious bursal disease
Lymphoid leucosis
Marek’s disease
Newcastle disease
Poultry Diseases Caused by Protozoa
Important protozoal diseases include:
Blackhead
Coccidiosis
Hexamitiasis
Poultry Diseases Caused by Parasites
Notable parasitic diseases include:
Ascarid worms
Capillaria
Cecal worms
Chiggers
Gapeworms
Lice
Mites
Tapeworms
Ticks
Poultry Diseases Caused by Fungi/Mold
Important fungal diseases include:
Aspergillosis
Moniliasis
Mycotoxicosis
Detailed Analysis of Specific Diseases
Fowl Cholera
Cause: Pasteurella multocida (bacterium)
Organism can survive for up to one month in droppings and three months in decaying carcasses, two to three months in soil.
Hosts:
Affects various birds including chickens, turkeys, pheasants, pigeons, waterfowl, and sparrows.
Symptoms:
Stupor, loss of appetite, rapid weight loss, lameness due to joint infections, swollen wattles, difficulty breathing, and watery yellow or green diarrhea.
Transmission:
Through excreta of diseased birds, carcasses of affected birds, contaminated water supplies, and mechanical transmission via shoes and equipment.
Diagnosis:
Accurate diagnosis can only be performed in a laboratory. Isolation and identification of the organism are necessary.
Treatment:
Sulfonamides (such as sulfadimethoxine) may be administered in water to control disease and reduce mortality; however, there may be relapse after drug withdrawal.
Control Measures:
Use of bacterins (live vaccines) which are effective, with total eradication being the ultimate control measure.
Aspergillosis (Brooder Pneumonia)
Cause:
Aspergillus fumigatus (fungus) found in poultry environments live on decaying organic matter.
Symptoms:
Gasping, sleepiness, and loss of appetite, particularly in young chicks, with internal symptoms including hard nodules in lungs and air sac infections.
Transmission:
Through dried spores in the air and contact with contaminated feed or litter.
Diagnosis:
Visual examination of lung slices will reveal nodules, with culturing possible.
Treatment:
No drug treatments available; thorough cleaning of premises is necessary to eliminate the infection source.
Control/Prevention:
Preventative measures include avoiding moldy feed, litter, and thorough disinfection of equipment used in poultry housing.
Newcastle Disease
Historical Context:
Known for being first diagnosed in Newcastle, England; also known as Ranikhet disease.
Characteristics:
Highly infectious, primarily affecting chickens, turkeys, and pheasants.
Cause:
Caused by a filterable RNA virus with one serotype and classified into four forms based on pathogenicity:
Viscerotropic velogenic (high pathogenicity)
Velogenic or neurotropic (high pathogenicity)
Mesogenic (intermediate pathogenicity)
Lentogenic (mild pathogenicity)
Symptoms:
Symptoms include difficulty breathing, gasping, sneezing, nasal discharge, nervous disorders, reduced egg production and quality, and corneal cloudiness.
Transmission:
Highly contagious; the virus can spread via the air, clothing, shoes, and equipment, as well as from wild birds.
Diagnosis:
Diagnosis is mostly based on physical examination and may include tests such as the hemagglutination-inhibition test and fluorescent antibody test.
Treatment:
No known treatment exists; prevention relies on vaccination programs, where broiler chicks are typically vaccinated when 7-10 days old and laying hens three times at 7 days, 4 weeks, and again at 4 months old.
Marek’s Disease
Characteristics:
Common in young chickens but can also affect older birds; chicken is the only known susceptible source.
Cause:
Associated with a DNA herpesvirus, with several identified serotypes.
Transmission:
Primarily bird-to-bird transmission, as well as airborne spread from skin and feather cells.
Symptoms:
Symptoms include paralysis of legs, wings, neck, weight loss, anemia, and diarrhea.
Diagnosis:
Easily observable tumors may indicate Marek's disease; lab tests exist but can be costly.
Treatment:
No effective treatments available; prevention includes vaccination shortly after hatching.
Coccidiosis
Definition:
Refers to diseases caused by coccidia, a group of protozoan organisms; one of the most devastating diseases of poultry.
Cause:
Caused by a group of protozoan organisms in the genus Eimeria, specific to chickens.
Transmission:
Coccidia spreads via unicellular bodies (oocysts) present in feces; sporulation is necessary before ingestion.
Life Cycle:
Sporulation occurs in optimal conditions within 2-4 days; sporulated oocysts are ingested and invade the intestinal tract, multiplying and restarting the cycle.
Symptoms:
Presentation includes bloody droppings, ruffled feathers, paleness, loss of appetite, poor growth performance, and decreased egg production.
Diagnosis:
Diagnosis based on visible intestinal lesions; scrapings are examined under a microscope for presence of coccidia.
Treatment:
Several drugs like sulfaquinoxaline, sulfamethazine, and amprolium may be beneficial, depending also on the type of poultry being treated.
Control/Prevention:
Easier to prevent than treat; coccidiostats are often included in feed to suppress the life cycle of protozoa.
Other Diseases
Laryngotracheitis (LT)
Global Presence:
Found globally, primarily affects chickens, though turkeys and pheasants can also be infected.
Cause:
Caused by the specific herpesvirus Tarpeia avium.
Symptoms:
Include severe coughing, difficulty breathing, and significant hemorrhaging.
Transmission:
Airborne transmission and indirectly via equipment and contaminated surfaces.
Diagnosis:
Testing involves inoculating suspicious material and observing responses.
Control/Prevention:
Vaccination strategies must be employed early for effective prevention.
Pullorum Disease
Transmission:
Highly contagious, can localize in multiple organs; egg transmission is significant in spreading.
Diagnosis and Treatment:
Cultures taken from infected organs to identify Salmonella pullorum; treatment consists of administering furazolidone and sulfonamides.
National Poultry Improvement Plan (NPIP)
Establishment:
Initiated in 1935 as an agreement between producers, state authorities, and the USDA to enhance poultry health.
Initially aimed at controlling Pullorum Disease, resulting in high mortality rates.
Expanded to include a broader range of diseases.
Testing and Monitoring:
Includes testing for Salmonella Pullorum, Mycoplasma infections, and Avian Influenza, among others.
Management:
Jointly developed standards by industry members and government officials ensure poultry freedom from NPIP diseases.
Relation to State Officials:
State officials assist in program administration, with requirements varying by state.
Eligibility and Benefits:
Initial requirement: birds must be tested free of designated Salmonella strains; offers benefits like confirmed health status for buyers, facilitating interstate transport and participation in shows.
Conclusion
Understanding poultry diseases, their mechanisms, treatments, and prevention strategies is critical for maintaining the health and productivity of poultry stocks. By leveraging the information provided in this document, poultry health management can be approached with a science-based framework for reducing loss and ensuring food security.