In global chicken farming, other than avian influenza, Newcastle disease (ND) and Infectious Bronchitis (IB) are considered the most economically important diseases. According to evidence-based publications and survey results, global day-old broiler chick vaccination practice has been shifting from IBMass+ND to co-vaccination with IBMass+IBVariant+ND.
ND and IB are caused by a paramyxovirus and coronavirus respectively. Notably, mortality of 80-100% and 25-80% have been reported for ND and IB respectively. To date, there are no specific global figures outlining the total economic losses due to ND and IB. However, a recent publication, the World Livestock Disease Atlas (The World Bank, Agriculture and Rural Development), stated that losses in poultry production due to IB are far higher than losses due to ND. Workers in Brazil indicated that for every 1,000 chicks placed, losses due to IB in broiler and breeder chickens were estimated at US$ 266 and around US$ 3,567 respectively. While costs attributed to ND outbreaks can have devastating impacts on the livelihood of local producers, no similar data is currently available.
Genetically improving resilience to Newcastle Disease
A team of international scientists in Africa and the United States are developing strategies to genetically improve the resistance of chickens to Newcastle Disease virus in indigenous chickens in Africa.
Traditionally for many decades, live ND or IB vaccines were administered to chicks when maternally derived antibodies (MDA) against ND or IB had sufficiently declined. This was practiced as highly virulent live vaccines had been shown to neutralise MDA and potentially cause disease in susceptible flocks. However, with the development of attenuated live vaccines continuously improving, less virulent vaccines were administered at one-day-old. This therefore induced early immunity and reduced the frequency of vaccine administration to the same flock (thus avoiding stress to birds). Day-old vaccination also means that they are administered at the hatchery, which provides a cleaner and more steadfast vaccination environment compared to the farm. Subsequently, hatchery vaccination technology was further refined with more sophisticated, reliable, faster and efficient automated equipment.
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Initially, only live ND vaccines were applied in day-old broiler chicks at the hatchery or farm in many countries. With the availability of milder IB vaccine strains such as H120 or Ma5, producers started to use a combined IBMass+ND vaccination. This has been in practice for a few decades and is still a common practice in many countries.
Emergence of variant IBVs
From the 1990’s, poultry farming began experiencing the emergence of variant IBVs (such as 793B, QX, Q1, Variant 2), which caused increased levels of respiratory and kidney diseases in broilers, with high mortality and carcass condemnation at abattoirs. To tackle this, in addition to IBMass+ND at day-old, a second dose of IBMass or IBVariant given at 10-14 days became common practice. Unfortunately, such vaccination regimes in some countries did not manage to suppress the production losses effectively.
Research on co-vaccination
Our research at the University of Liverpool, has shown that IBMass+IBVariant or IBMass+IBVariant+ND can be co-administered in day-old broiler chicks. Such vaccination provided excellent protection (> 90%) against classical and variant IBV strains, including M41, 793B and QX (Table 1). In addition, ND HI titres were equal to or more than 5 log2, which is considered to be a protective titre. In particular, the compatibility of administering IBMass+IBVariant+ND in day-old commercial broiler chicks has given much confidence for producers where ND is endemic. Co-vaccination induced the same protection against challenge as if the vaccines were administered separately.
Designer vaccines for free-range poultry
Preventative veterinary care is gaining in importance, but vaccinations offer no panacea. That said, farm-specific inoculations are becoming more mainstream.
To ascertain the degree of change in ND and IB vaccination programs since 2012, a short survey was undertaken, where questionnaires were sent to poultry producers in different regions of the world. Producers in Africa, Asia, Europe, and South America, who all have a combined approximate production of 1,337 million chickens, were surveyed. From the information returned, it was evident that producers around the world have begun to adopt the combined IBMass+IBVariant+ND vaccination protocol.
When poultry producers in various countries applied the modified scheme:
By 2017, the majority of chickens surveyed were receiving the combined IBMass+IBVariant+ND vaccination, rather than IBMass+ND. By end of 2019, it appeared that an increasing percentage of birds are being vaccinated with IBMass+IBVariant+ND compared to IBMass+ND (Figure 1).
Source: University of Liverpool. Click here to view larger image
A producer’s decision on the selection of vaccine strains and vaccination schedule is much influenced by flock performances. Though there are different strains of IBMass or IBVariant, in our survey, only those using IBMass H120 or Ma5 plus IBVariant of 793B (either CR88, 4/91 or 1/96) were included. Based on this limited study, several economic advantages were found in the surveyed countries (Figure 2). It was obvious that in certain countries, advantages of changing the vaccine scheme had more of an impact, reflecting either the overall commercial farming technology or know-how, and other constraints of the respective country/region. Following application of IBMass+IBVariant+ND, mortality rates reduced in all regions (0.06% – 7.5%), live weight at catch increased (6 – 425 g/bird), and there was a reduction of 6-25g of feed intake per Kg of body weight. In addition to performances, some respondents reported an improvement of 0.06% in carcass condemnation and reduced turn-over days (1-2 days).
Source: University of Liverpool. Click here to view larger image
According to evidence-based publications and survey results, global day-old broiler chick vaccination practice has been shifting to co-vaccination with IBMass+IBVariant+ND. Such practice is likely to continue to increase, due to improved flock performances, more efficient administration of vaccines at day-old in the hatchery, and early and stronger (wider) induction of immunity. A reduction in handling of chicks in farms also reduces stress, prevents spread of disease due to visits of the vaccination team, and improves overall welfare benefits for birds. Still, the efficacy of combined vaccination is dependent on the strain of live ND or IBMass or IBVariant vaccines, flock status and environmental conditions in the farm. Veterinarians need to be consulted prior to implementation of any vaccination changes.
Kannan Ganapathy & Chris Ball, University of Liverpool, UK