YOUR ANIMAL HEALTH QUERIES SIMPLIFIED
Question: Newcastle diseases and Mycoplasmosis (CRD) in laying birds are two major factors in profitability of egg production enterprise. How do we differentiate the two and prevent accordingly?
Answer
Differentiating Newcastle disease (ND) from mycoplasmosis in laying birds can be challenging as both sides can present with respiratory symptoms and drops in egg production. However there are distinct features that can help distinguish between the two diseases based on clinical signs, post mortem findings and diagnostic tests.
(1) Causative Agents:-
• New castle diseases is caused by the Newcastle diseases virus (NDV), a highly contagious paramyxovirus.
• Mycoplasmosis is caused by mycoplasma galliseplicun (MG) which is a bacteria pathogen without cell walls.
(2) Mode Of Transmission:-
• Newcastle Disease: is a highly contagious disease through aerosol, direct contact with infected birds, contaminated equipment and fomites.
It can spread quickly within a flock, often with high morbidity and mortality.
• Mycoplasmosis: is a chronic disease that spread primarily by bird to bird contact or vertically (from infected breeders to offspring’s through eggs).
• The diseases spread more slowly compared to ND, with low mortality.
Key Clinical Signs
Newcastle Diseases
• Respiratory Symptoms: gasping, coughing, nasal discharge, sneezing.
• Neurological Signs: tremor, paralysis, torticollis (twisting of the head and neck) and dropping wings.
• Dropping Egg Production: sudden and sharp decline in egg production, with poor quality
• Eggs (thin shells, discolored and misshapen).
• Other Signs: diarrhea, dehydration in severe cases, high mortalities.
• Hemorrhages in the trachea, proventiculus and intestinal linings during post mortem examination.
Mycoplasmosis (MG/MS)
• Respiratory Symptoms: mild respiratory signs like nasal discharge trachea rales, coughing, sneezing.
• Conjunctivitis or swollen sinuses, particularly in chronic stages
• Chronic nature
Unlike ND, mycoplasmosis is a more chronic respiratory disease with slower onset and progression.
• Egg production decline:
• Drop in egg production, but typically not as sudden or severe as with ND.
• Egg quality issues (thin shells, reduced egg size) can occur.
• Joint involvement (mycoplasma synoviae).
• In the case of MS, birds may show swollen joints, leanness, and reduced mobility.
Mortality:- mortality rate can be very high, depending on the virulence of the NDV strain (Up to 100% in virulent strains)
Mycoplosmosis – Mortality is generally low but the diseases causes chronic losses in production and overall flock health.
Post Mortem Findings
Newcastle diseases
• Hemorrhages in the trachea, proventiculus and intestines are typical
• Air sacculitis
• Inflammation of air sacs with fibrinous exudates in some cases.
• Lesson in the CNS
• With neurotropic strains, microscopic brain lesions are found.
Mycoplasmosis
• Air saculitis
• Often see foamy or caseous exudates in the air sacs more pronounced than ND.
• Tracheitis: mild inflammation of the trachea, with mucus present.
• Swollen sinuses.
• Mycoplasma gallisepticum can cause swollen sinuses with clear or turbid discharge.
• Chronic lesions
• Pocket of pus and chronic inflammatory lesions, especially around the respiratory tract.
Preventive strategies for controlling Newcastle diseases (ND) and Mycoplasma gallisepticum (MG) in a laying flock focus on bio security, vaccination, and management practices and diseases surveillance. These measures are essential to prevent introduction and spread of these diseases which can lead to significant production loses:
(1) Bio Security Measures:
Effective bio security is the first line of the defense against NCD and MG. key practices include
Controlled Access:
(a) Restrict entry to the poultry farm to authorized personnel only.
(b) Install foot baths with disinfectant at the entrance of each poultry house to prevent contamination
(c) Ensure workers wear protective clothing (boots, gloves and cover all) and disinfect between poultry houses.
• Visitors And Vehicle Control:
Limit farm visitors and ensure that visitors follow strict hygiene protocols.
• Disinfect vehicles entering the farm to avoid introducing pathogens from external sources.
• All in, all out system:
• Implement and all in all out system to avoid mixing flock of different ages. Older birds can be carriers of MG, while ND spreads rapidly across age groups.
• Isolation Of New Birds:
quarantine new birds for at least two to three weeks before introducing them into the existing flock. This allows time to monitor for signs of disease.
Rodent and wild bird control:
• Rodents and wild birds can carry both ND and MG. Secure poultry houses with proper netting and eliminate potential rodent habitat near the pens.
Vaccination Programs
Newcastle diseases (ND) vaccination
• ND vaccines are critical for preventing outbreaks. Vaccination should be done according to local schedule that matches the diseases risk in the region. (consult us on bespoke protocol for your farm).
• Common vaccines include:
- Live vaccine (eg lasota, B1 strains, avinew) administered via drinking water, spray or eye drops. These provide good protection but need periodic boosting.
- Inactivated vaccine: can be administered in combination with live vaccine to provide long lasting immunity.
- Vaccinate chicks at an early age (often at 1 day old or within the first week) and follow up with boosters doses based on the regional diseases pressure.
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Mycoplasma gallisepticum (MG) vaccination
• Vaccination against MG can help reduce clinical diseases although it may not fully eliminate infection.
• Live vaccine (e g F-strain, 6/85 strain) are often used in endemic areas to reduce the impact of the diseases. This vaccine can be administered via spray or drinking water.
• Killed Vaccine: are used in conjunction with live vaccine or in layers to provide additional protection.
• Vaccination Timing: vaccine birds before the onset of lay or before any expected MG challenge, as stressed birds are more vulnerable to the diseases.
(2) Environmental Management:
- Ventilation and stocking density
- ensure proper ventilation to reduce respiratory stress, which can make birds more susceptible to both MD and MG.
- Avoid overcrowding, which increases stress and likelihood of diseases spread.
Litter management
• Maintain clean, dry litter to reduce the risk of MG and ND transmission through contaminated feces and dust particles.
• Regularly remove and replace wet soiled litter to minimize pathogen building.
Water and feed hygiene
• Ensure clean, uncontaminated water sources by regularly cleaning and disinfecting drinkers.
• Provide balanced nutrition to birds healthy and improve their immune response to both MD and MG.
(3) Monitoring And Early Protection
• Surveillance And Regular Testing:
Improve routine serological and PCR testing for both ND and MG especially in endemic areas, to detect subclinical infections.
• Monitor flocks health regularly, keeping an eye out for respiratory symptoms, lethargy, or drops in egg production, which could indicate an outbreak.
Post- Mortem Examination
• Conduct necropsies on any birds that die unexpectedly to check for signs of ND or MG such as respiratory lesion or organ damage.
Immunity Support
Probiotic, Immune Modulators And Antibiotics
• Use probiotics, vitamins or other immune-boosting supplements in feed to strengthen the bird’s immune systems against viral and bacterial challenges.
• In cases where MG is endemic, the strategic use of antibiotics (eg tylosin, doxycycline) can help reduce the impact of the diseases.
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