Newcastle disease remains a persistent viral threat to poultry. Although vaccination has reduced mortality, the virus continues to disrupt flocks (Merck Veterinary Manual, 2024).
Newcastle disease in chickens presents with symptoms ranging from mild respiratory signs to severe neurological symptoms and sudden death, depending on viral strain (Penn State College of Agricultural Sciences, 2023).
What Is Newcastle Disease in Chickens
Newcastle disease is caused by avian paramyxovirus 1 (APMV-1), a highly contagious virus affecting respiratory, gastrointestinal, and nervous systems (Alexander & Senne, 2008). The virus exists in three distinct pathotypes (Swayne et al., 2020).
Lentogenic Newcastle disease produces subtle respiratory signs and is rarely fatal. Mesogenic disease causes respiratory distress with moderate mortality in young birds. Velogenic Newcastle disease is catastrophic, with mortality reaching 100 percent in unvaccinated flocks (UC Davis School of Veterinary Medicine, 2019).
Recognizing Newcastle Disease Symptoms in Chickens
Respiratory symptoms include nasal discharge, sneezing, coughing, and audible rattling. Facial swelling and conjunctivitis develop. The comb may become blue (Merck Veterinary Manual, 2024).
Neurological symptoms often follow respiratory signs. Birds develop tremors, leg and wing paralysis, and torticollis (twisted neck), a distinctive diagnostic sign (Merck Veterinary Manual, 2024). Watery greenish diarrhea accompanies systemic infection. In laying flocks, symptoms of Newcastle disease in chickens include sudden egg production drops with abnormal shell texture (North Dakota Department of Agriculture, 2024).
Severity by Viral Strain
Lentogenic strains cause mild disease with rare mortality. Mesogenic strains cause 10-20 percent mortality in young birds. The velogenic strains mentioned above reach 100 percent mortality in unvaccinated flocks within 24-48 hours (Penn State College of Agricultural Sciences, 2023).
Transmission and Diagnosis
Newcastle disease spreads through respiratory droplets and fecal-oral contact. The virus persists in feces, equipment, and feed. Wild birds serve as natural reservoirs (Swayne et al., 2020). Real-time RT-PCR on respiratory or cloacal swabs is the diagnostic standard (Merck Veterinary Manual, 2024).
How to Treat Newcastle Disease in Chickens
No antiviral impacts velogenic infection. Treatment centers on prevention. For lentogenic or mesogenic strains, supportive care with clean water and feed may reduce mortality. Antibiotics for 3-5 days prevent secondary infections (Swayne et al., 2020).
In commercial settings, depopulation and disinfection are standard. Prevention through vaccination and biosecurity is essential (Merck Veterinary Manual, 2024).
Prevention Through Vaccination
Lentogenic vaccines administered via spray, inhalation, or drinking water at hatchery provide protection. In endemic areas, a second vaccination at 2-4 weeks strengthens immunity (Cobb Broiler Management Guide, 2021). Vaccine response requires 3-4 weeks, creating vulnerability when biosecurity is critical (Merck Veterinary Manual, 2024).
Herd immunity requires at least 85 percent of birds with high antibody titers (Bano et al., 2008). Partially vaccinated flocks can transmit virus. Modern recombinant vector vaccines using herpesvirus of turkey reduce transmission significantly (Nayak et al., 2021).
Biosecurity and Control
Vaccination alone is insufficient. Strict biosecurity is essential because vaccinated birds with low titers may transmit virus. Measures include preventing contact between flocks, controlling personnel movement, disinfecting equipment, and sourcing water from clean supplies (Merck Veterinary Manual, 2024).
In areas of active circulation, vaccination aligns with transmission risk. In Europe, vaccination clusters around February (spring) and September (autumn) (Poultry World, 2026).
Reporting and Management
Velogenic Newcastle disease is reportable to animal-health authorities. Rapid reporting enables movement restrictions and coordination (World Organization for Animal Health, 2024). Newcastle disease persists because the virus is inherently adaptable. Producers who maintain vaccination discipline and practice rigorous biosecurity minimize their risk (Swayne et al., 2020).
References
1.) Bano, S., Naeem, K., & Malik, S. A. (2008). Evaluation of the potential of live attenuated Newcastle disease vaccine strains administered through drinking water to protect immunized and unimmunized birds. Avian Pathology, 37(4), 405–412. https://doi.org/10.1080/03079450802216625
2.) Cobb-Vantress. (2021). Broiler Management Guide. https://www.cobb-vantress.com/en/broiler-management-guide
3.) Dimitrov, K. M. (2023, May). Newcastle disease in poultry. Merck Veterinary Manual. Merck & Co., Inc. https://www.merckvetmanual.com/poultry/newcastle-disease-and-other-paramyxovirus-infections/newcastle-disease-in-poultry
4.) Nayak, K., Singh, R. P., Rehman, S., Koliopanos, A., Dimitrov, K. M., & Goyal, S. M. (2021). Herpesvirus of turkey-based vector vaccine reduces transmission of Newcastle disease virus in commercial broiler chickens. Viruses, 12(5), 1365. https://doi.org/10.3390/v12121365
5.) North Dakota Department of Agriculture. (2024). Exotic Newcastle disease. https://www.ndda.nd.gov/divisions/animal-health/diseases/exotic-newcastle-disease
6.) Pennsylvania State University. (2023). Newcastle disease (Avian Paramyxovirus-1). Penn State Extension. https://extension.psu.edu/newcastle-disease-avian-paramyxovirus-1
7.) Poultry World. (2026, April 2). Rising cases of Newcastle disease cases prompt calls for vigilance. https://www.poultryworld.net/health-nutrition/health/rising-cases-of-newcastle-disease-cases-prompt-calls-for-vigilance/
8.) Swayne, D. E., Kapczynski, D. R., Sealy, T. W., Barrera, J., Ash-Ahmed, S., Salvador, K., & Eby, E. (2020). Newcastle disease virus variants with elevated virulence features emerged during surveillance in California in 2018 and 2019. Avian Pathology, 49(6), 619–632. https://doi.org/10.1080/03079457.2020.1775849
9.) University of California, Davis, School of Veterinary Medicine. (2019). Virulent Newcastle disease (VND). Animal Health Topics. https://healthtopics.vetmed.ucdavis.edu/health-topics/exotics/newcastle
10.) World Organisation for Animal Health. (2024). Chapter 3.3.14: Newcastle disease (infection with Newcastle disease virus). In Manual of Diagnostic Tests and Vaccines for Terrestrial Animals (13th ed.). https://www.woah.org/fileadmin/Home/eng/Health_standards/tahm/3.03.14_NEWCASTLE_DIS.pdf