Infectious bronchitis (IB) virus, first described in the 1930s (Schalk & Hawn, 1931), continues to be a major cause of disease in chickens of all ages and types in all parts of the world (Anon, 1988, 1991). Good quality vaccines have been available to control IB infections since the 1950s. However, despite their careful use, IB continues to be a major problem. One reason for this is the large number of antigenic types of IB that are known to exist worldwide. The first IB serotype to be described was Massachusetts (Schalk & Hawn, 1931). This was followed in the mid-1950s by the Connecticut serotype (Jungherr et al., 1956). Since that time, new IB serotypes continued to be reported from the US (Gelb et al., 1991), Europe (Davelaar et al., 1984; Cook & Huggins, 1986) and many other parts of the world. (Cubillos et al., 1991); Middle Eastern countries are also suffering from this problem.
With the help of molecular studies, it is now known that it is the S1 part of the IB virus that is responsible for the determination of its serotype. Furthermore, a new IB virus serotype(s) can arise as a result of only a very few changes in the amino acid.
The Middle East area has an estimated poultry population of 3 billion broilers, 137 million commercial layers, 30 million breeders, 2 million layer breeders and 0.5 million GP broilers. In the last few years it was noticed that breeder and layer flocks in the Middle East area were facing different problems such as false layers, penguin position, drop in egg production and no peak in production; while broilers were suffering from respiratory signs, nephritis and high mortality up to 25% with an increase when it is combined with AI-H9N2 or ND.
Although several vaccines were available in the market for controlling IB infection, new variant strains have appeared and cannot be controlled by them. Thus, it has been believed valuable to find out what type of IB variant strains are playing a role in the Middle East area and to check using live-attenuated IB vaccines belonging to different serotypes (IB Ma5 + IB 4/91) to help control different IB variant strains.
Materials and methods
Samples from infected flocks were taken from Kingdom Saudi Arabia (KSA), Jordan, Syria, Lebanon, United Arab Emirates (UAE), Kuwait, Algeria, Bahrain and Yemen and analyzed using an HI test at MSDAH- Regional Service Lab / Jordan and PCR techniques at X-Ovo lab and Intervet International R&D lab (Netherlands).
The results showed that different IBV variant strains played a role in the Middle East. QX and 4/91 showed high titer (graph 1), while PCR results showed the presence of more than one IB variant (QX, 4/91,Var 2, Iranian, Sul/01/09, D274 and M41 in the same farm even in the same flocks [graph 2]).
Graph 1: % of positive resultsa of HI test. Graph 2: % of positive PCR results
a: positive results for breeders and layers HI >6 and HI >4 for broilers.
For better IB control the ProtectotypeTM concept (Ma5 and the variant strain 4/91) was applied in breeders, layers and broilers. Involved flocks were vaccinated and monitored according to:
Broiler ProtectotypeTM program:
@ day 1: Nobilis IB Ma5
@ 14 days: Nobilis IB 4/91
The following parameters were our monitoring parameters:
For broilers: the reduction in mortality, improvement in body weight, feed conversion, and for breeders and layers, production and egg quality were monitored.
The ProtectotypeTM program was implemented in two broiler farms–A & B–and according to the graph 3, 4, and 5 showed a reduction in % of mortality, increase of body weight and improvement in production index.
Graph 3: Mortality before and after the new IB vaccine protocol was implemented on Farm A.
Graph 4: Average weight before and after implementation of the new IB vaccine protocol on Farm A.
Table 1: Performance results on Farm B before and after implementation of the IB ProtectotypeTM protocol
On the other hand, the following ProtectotypeTM program was applied for breeders/ layers:
@ day 1: Nobilis IB Ma5 +Nobilis IB 4/91
@ 14 days: Nobilis IB Ma5
@ 8 weeks: Nobilis IB 4/91
The following parameters were our monitoring parameters:
Egg production and egg quality
As shown in graph 5 it was noticed that there is a drop in egg production during IBV infection, starting from 32 weeks, compared to standard curve. After implementation of ProtectotypeTM program the drop disappeared and production curve returned back to the standard level as seen in graph 6.
Graph 5: Egg production.
A. During IBV infection before implementation of ProtectotypeTM. - B. After ProtectotypeTM implementation.
Additionally, many field visits to flocks to check the clinical signs, in Kingdom Saudi Arabia (KSA), Jordan, Syria, Lebanon, United Arab Emirates (UAE), Kuwait, Algeria and Yemen.
Graph 6: Clinical signs in breeders and broilers? Penguin position, oviduct fluidity and egg quality.
A. Breeders B. Broilers
Researchers, however, have shown that some serotypes of the IB virus can induce cross-protection against other serotypes and that a new live vaccine is not required to control each new serotype that emerges. Existing IB serotypes that can provide cross-protection are referred to as ProtectotypesTM. Recent experience on two broiler farms in the Middle East has demonstrated that after utilizing IB vaccine ProtectotypeTM protocols featuring Nobilis IB Ma5, Nobilis IB Ma5 + Clone 30 and Nobilis IB 4/91, body weight increased, mortality decreased and feed conversion improved. Additionally, in breeders, it was noticed that drop in production disappeared and production curve returned back to its standard level. Our results were consistent with the previous one that confirms the ProtectotypeTM concept (Cook et al,1999).
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