Managing Newcastle disease: Proactive poultry disease strategies

Estimated reading time: 5 minutes

  • Newcastle disease is a serious viral infection caused by the highly contagious avian paramyxovirus serotype 1. It affects domestic poultry and other birds, and is known for its rapid onset and varying degrees of mortality.
  • In laying flocks, a sudden decrease in egg production with many abnormal (often soft-shelled) eggs can be an early sign of Newcastle disease.
  • According to the Animal Diseases Act, 1984 (Act 35 of 1984), any suspicion or confirmation of the disease must be reported to the nearest animal health technician, state or private veterinarian.
  • Although there is no treatment for chickens infected with Newcastle disease, registered vaccines are available to help trigger an antibody response.
  • The main benefit of early vaccination against Newcastle disease is the speed at which it provides protection. Chicks usually inherit some level of maternal antibodies from vaccinated breeder chickens.

Poultry are susceptible to various harmful pathogens, including bacteria, viruses and parasites, which can lead to serious and sometimes fatal illness. One of the most severe poultry diseases worldwide is Newcastle disease, which can cause major disruptions on farms and greatly affect the poultry industry.

According to an article by the Department of Agriculture, Land Reform and Rural Development (DALRRD), Newcastle disease is a serious viral infection caused by the highly contagious avian paramyxovirus serotype 1. It affects domestic poultry and other birds, and is known for its rapid onset and varying degrees of mortality. The article notes that symptoms in birds can range from severe, with sudden onset and high mortality, to milder forms where the only signs are respiratory issues or a drop in egg production.

The disease is typically spread through direct contact with infected birds’ secretions, particularly faeces, but it can also be transmitted through contaminated vehicles, equipment, people, clothing, water or feed.

In laying flocks, a sudden decrease in egg production with many abnormal (often soft-shelled) eggs can be an early sign of Newcastle disease. Infected chickens show various symptoms, including lethargy, loss of appetite, respiratory distress with beak gaping, nervous symptoms, coughing, sneezing, gurgling noises, green diarrhoea, and swollen sinuses.

The article highlights that young birds are particularly susceptible, often experiencing high mortality rates, and survivors may have permanent nervous symptoms.

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A notifiable disease

If Newcastle disease is suspected or confirmed through lab tests, no items that could spread the disease may be removed from the premises. According to the Animal Diseases Act, 1984 (Act 35 of 1984), any suspicion or confirmation of the disease must be reported to the nearest animal health technician, state or private veterinarian. The Provincial Veterinary Services will impose controls on the movement of poultry, other captive birds, people, animals, eggs, vehicles and any other items that might carry the disease, both to and from the premises.

Poultry and captive birds on-site must be housed or kept away from other birds to avoid spreading the infection. Additionally, if not already present, disinfection facilities should be set up at the entrances and exits of the premises and around housing. These measures are aimed at containing the disease and preventing it from spreading further.

Prevention measures

Although there is no treatment for chickens infected with Newcastle disease, registered vaccines are available to help trigger an antibody response. Implementing good on-farm biosecurity measures is also one of the best ways to prevent and control outbreaks. An information piece on the South African Poultry Association’s website discusses vaccination strategies for the disease, mentioning that the lentogenic and apathogenic strains are the primary strains used in vaccines.

The article explains that maternal antibodies passed from the hen to the chick can offer some protection against the disease. However, these antibodies may interfere with the long-term development of the chick’s humoral immunity, which is the body’s ability to produce antibodies. Despite this, they do not stop the rapid onset of protection through local immunity, making early vaccination highly effective. This is why vaccinating against Newcastle disease at a very young age – even as early as day-old – is recommended.

Early vaccination stimulates local immunity in key areas such as the Harderian gland, the upper respiratory tract, and the gastrointestinal tract. The development of humoral immunity, which involves the production of antibodies in response to a pathogen, follows later. This dual approach ensures that chicks have protection both locally and systemically.

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Early vaccination

The main benefit of early vaccination against Newcastle disease is the speed at which it provides protection. Chicks usually inherit some level of maternal antibodies from vaccinated breeder chickens. Early vaccination is usually done at the hatchery using a live vaccine, which will significantly boost the protection given by these maternal antibodies during the first three weeks of a chick’s life. Early immunity can be further boosted using recombinant vaccines against Newcastle disease at the hatchery. In long-lived birds such as laying hens, live vaccine boosters are recommended every six to eight weeks to maintain long-term protection.

Antibodies can be detected in local secretions and serum within six to ten days after vaccination. The best methods for administering live vaccines against Newcastle disease are spraying or using the eye-drop method, as these stimulate both local and body-wide immunity. A common approach in longer-lived birds is to add an inactivated vaccine at between 12 and 16 weeks of age. Provided that live vaccine boosters are applied, this combined approach will provide good lifelong immunity.

It is worth noting that some Newcastle disease vaccine strains can cause mild respiratory issues in birds, which could increase the risk of other respiratory diseases. Always consult a veterinarian to determine the best vaccination strategy and the appropriate vaccines to use for your specific situation. – Christal-Lize Muller, Stockfarm

For references, email the author at christal-lize@plaasmedia.co.za.

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