DEVELOPMENT OF INACTIVATED WHOLE CELL VACCINE AGAINST OVINE FOOT-ROT
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Date
2012-11
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Sri Venkateswara Veterinary University, TIRUPATI – 517 502,A.P
Abstract
ABSTRACT :
Foot rot is an infectious and contagious disease of sheep and goat caused by an anaerobic bacterium Dichelobacter nodosus. The disease results in lameness of affected sheep and goat leading to production losses. The disease is being reported in Andhra Pradesh regularly during the rainy season. Treatment of affected sheep appears to be costly and not economical. Serogroup specific vaccination found to have excellent therauptic efficacy. Hence the study was taken up to develop an inactivated whole cell vaccine against ovine Foot rot using local isolates belonging to serogroups B and I.
The serogroups B and I of D. nodosus were selected as vaccine strains based on earlier isolation and serogrouping studies in Chitoor district of Andhra Pradesh. The available serogroups B and I of D. nodosus were revived in TASH agar media with 2% hoof powder. Purity of antigens were checked and the concentration of antigens were adjusted to 1x108 org/ml and 2x109 org/ml. Later the antigens were inactivated by adding formalin at a concentration of 0.5% for overnight and adjuvanted separately using Montanide and Alum. The whole cell inactivated adjuvanted vaccines thus prepared were subjected for safety and sterility tests according to British pharmacopoeia (1985). Later trials were conducted in laboratory animals and also in the field to study the efficacy of vaccine.
Experimental trials were conducted in sheep and goat under laboratory conditions with two different adjuvants, namely Montanide, Alum and with two different antigenic concentrations i.e. 1x108 org/ml and 2x109 org/ml.
The immune responses were evaluated in sheep and goat by measuring antibody response using microtiter plate agglutination test and ELISA. The immune response was high in vaccines prepared using antigenic concentration of 2x109 org/ml compared with antigenic concentration of 1x108 org/ml. Similarly among two adjuvants Montanide and Alum, Montanide adjuvanted vaccines were found to be better in eliciting immune response.
Further field evaluation of vaccine prepared using serogroup B of D. nodosus adjuvanted with montanide was also conducted in sheep in one of the village of Chitoor district of Andhra Pradesh, where the Foot rot was reported previously. The booster injection was given on 30th day of primary dose. The vaccine induced satisfactory protective titers.
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Keywords
OVINE FOOT-ROT; sheep; goat; WHOLE CELL VACCINE