Effects of Vaccination Routes Against IB on Performance and Immune Responses of Broiler Chickens

Vaccination is often considered as an appropriate option in prevention most of poultry viral diseases worldwide. This study was conducted to evaluate effects of current routine vaccination routes (spray, eye-drop and drinking water) of live vaccines against infectious bronchitis (IB) on performance and humoral immune responses of broiler chickens. The results of this study indicated that Vaccination significantly (P<0.05) affects performance of the broiler chickens and effects on weight gain and FCR, did not differed significantly among these routes. Immune responses of vaccinated chickens were significantly (P<0.001) differed from those of control chickens. Comparison of various vaccination routes revealed that eye-drop group had the highest antibody titer with the closest range. There were also positive significant (P<0. 01) degrees of correlation among chickens vaccinated with spray and eye-drop, spray and drinking water, eye-drop and drinking water (r = 0.84, r = 0.80 and r = 0.82, respectively). In conclusion, eye-drop method induced the highest antibody titers with the closest range. Key word: Vaccination, IB, spray, eye-drop, drinking water Introduction Materials and Methods The art and science of vaccinology aimed at prevention of infectious diseases responsible for the huge economic losses in poultry industry worldwide. Among viral poultry diseases, infectious bronchitis (Cavanagh and Naqi, 2003) is acute, highly contagious and economically important diseases of chickens and in most countries, control of this disease is largely through the vaccination. Isolation of different strains or serotypes of IB virus (Cook, 2001) indicates that vaccination policy could be effective if the vaccines contain local strains and delivered via the best application route. Different types of vaccine including live, inactivated, DNA (Kapczynski et al., 2003) and recombinant (Song et al., 1998; Johnson et al., 2003) vaccines have been studied. On the other hand, effects of some vaccination routes with different types of vaccine on the outcome of immune responses have also been investigated (Ratanasethakul and Cumming, 1983; Cholakova, 1985; Wakenell and Sharma, 1986; Halvorson et al., 1991; Toro et al., 1997; Kapczynski et al., 2003). Previous studies support that routes of application affect receiving the proper dose of vaccine, time of stimulating protective immunity and range of immunity in a vaccinated flock. Differences between this study and the previous reports are application of three routes as a routine vaccination program and in drinking water routes. During this study, level of antibody, uniformity of immune responses and effects of secondary vaccination on humoral immunity induced by different methods of vaccination were compared. Chickens: Eighty one-day-old broiler chicks (Arbor-Acres strain) were divided into 4 groups (A, B, C and D, 20 chicks in each group). The chicks of each group were leg labeled, kept in a separate cages, fed ad libitum with a diet prepared based on Arbor-Acres husbandry catalogue. Vaccine and vaccination: Live attenuated Massachusetts H strain vaccine was used for primary 120 vaccination of 1-day-old chicks on arrival day and for revaccination at age 18 days against IB via the most routine routes of application including spray, eye-drop and drinking water methods as follows: Drinking water: A vial of vaccine was diluted with distilled water and serial dilutions were made until to get 1 dose of vaccine in 1 ml distilled water. The chickens of group A were given 1ml containing 1 dose of the vaccine via mouth using 1ml syringes. Eye-drop method: The vaccine was diluted with distilled water and serial dilutions were made until to get 400 dose of vaccine in 10 ml distilled water. One drop (0.25 μl containing 1 dose) was delivered for one-eye of each chicks of group B using a droplet dividing 1ml into 40 drops. Spray method: In this method, a vial of vaccine was diluted with distilled water and serial dilutions were made until to get 10 dose of vaccine in 10 ml distilled Talebi et al.: Routes of vaccination 796 Table 1: Performance of chickens during eight weeks of husbandry period Age Control Group Routes of Vaccination (week) --------------------------------------------------------------------------------------------------------------------------------------------------------------------Feed Average FCR Spray Group Eye-drop Group Drinking water Group ------------------------------------------------------------------------------------------------------------------Feed Average FCR Feed Average FCR Feed Average FCR (gr/week) Weight (gr/week) Weight (gr/week) Weight (gr) (gr) (gr) 0 --38 ----37.5 ----38 ----37.5 --1 112 125 1.28 112 120.5 1.34 112 120 1.36 112 121 1.34 2 224 275 1.49 224 268 1.51 224 267 1.52 224 270 1.50 3 420 540 1.58 420 530 1.60 420 527 1.61 420 533 1.59 4 630 895 1.77 630 877 1.81 630 875 1.81 630 880 1.81 5 77