الفهرس 
Chapter I : IntroductionOnly 14 pages are availabe for public view
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Abstract
Foot and Mouth disease (FMD) is a contagious world wide spread disease affecting cloven footed animals causing high economic losses due to reduced meat and milk production, abortion, high mortalities in young calves, hindering local and international trade of animals and convalescent animals became carriers acting as asource of infection. The disease is caused by FMD virus including seven main serotypes (O, A, C, SAT1, SAT2, SAT3, and Asia), as well as numerous intra typic strains. In Egypt FMDV type O1 and A are circulating serotypes, so prophylactic vaccination of animals with a locally produced serotype O, A vaccine is considered one of the most important methods of control; However, improper vaccination programs, insufficient vaccines, poor disease combat measures and the presence of carrier animals are important causes that influence FMD spread and recurrence among livestock. Sheep is a domestic animal that lives in almost all cattle farms and plays and important role in maintaining and transmitting FMDV. So the aim of our work is to spot the light on the role of sheep in transmitting the disease between the animals The applied experiments showed the following results:1- A highly potent inactivated bivalent FMD vaccine (A and O) was prepared,adjuvanted with Montanide ISA 206 and saponin. 2- The inactivated bivalent FMD vaccine (A and O) was evaluated for quality and showed purity, sterility and safety for both sheep and calves with no rise in body temperature and no clinical abnormalities for 10 days post vaccination. 3- Potency testing of the prepared vaccine was done in Guinea pigs and showed that the number of Guinea Pigs Protective Dose 50% (GPPD 50 ) was 33.6/dose for type A virus and 41.6/dose for type Evaluation of the humeral immune response in vaccinated groups of sheep using SNT at 7, 14 and 21 days post vaccination, showed that protective neutralizing
serum antibody titer (1.2) was reached at 14th days post vaccination, (1.30 for FMD virus type A and 1.41 for FMD virus type O) and the mean SNT titers after 21 days post vaccination were (1.66) for type A and (1.84) for type O5- Evaluation of the humeral immune response in vaccinated groups of sheep using SNT every week in first month and then every two weeks till 7 months post vaccination, showed that protective neutralizing serum antibody titer (1.2) was started from 2nd week post vaccination (1.32 for FMD virus type A and 1.4 for FMD virus type O) and persisted in protective level until the end of 7 months, and the highest level of antibody was recorded at 6th week post vaccination (2.53for FMD virus type A and 2.65 for FMD virus type O).
6- Vaccinated sheep were challenged at 21 days and 7 months after vaccination4 according to the group), by direct contact with calves infected by 10 BTID 50 of virulent homologous strain (A/Egypt/2006and O1/3/93) showed no rise in body temperature or clinical signs of FMD appeared on them in comparison to challenged unvaccinated control sheep group that showed elevated body temperature for 4 days post challenge, but there was no clinical signs of FMD appeared on them except only on one sheep from the group which challenged by FMDV type A that denotes sheep can remain as a silent carrier to FMD virus. 7- Detection of FMDV antigen in oro-pharyngeal ?uid samples collected from individual sheep post-challenge in all groups of vaccinated and unvaccinated
sheep using antigen detection ELISA revealed that there is no FMD virus type A or O were detected in isolated sample from groups of vaccinated sheep for one month post challenge time but FMD virus either type A or type. Summary in samples collected from groups of unvaccinated sheep post challenge time
which persisted for 22 - 30 weeks and 24 -32 weeks for type A and type O, FMD virus respectively; This result showed that the persistence of FMD virus in pharyngeal fluid of infected sheep as a carrier state ranged from five to eight months. 8- The humeral immune response to FMD virus type A and O in unvaccinated sheep post challenge using SNT for 12 months post challenge time showed that neutralizing antibody titer was raised to reach to peak at 8th week post challenge with high titer reach to (2.31) for type A and (2.37) for type O, and then decrease reach to zero at 40th week post challenge for virus type A and at 44th week post challenge for virus type O; This result showed that neutralizing antibody titer of the infected non vaccinated sheep quickly elevated reach to high titer and then rapidly decline than the vaccinated one with the presence of infection by the detected virus. putting free non infected calves in contact with unvaccinated groups of sheep after one week from their air born challenge revealed that the free calves become infected with
appearance FMD signs on them and rise in their body temperature that was confirmed by detection of FMD virus in tissue specimens from tongue of these calves using sandwich ELISA (FMD virus type A was detected in samples collected from twocalves in contact to sheep challenged indirectly with FMD virus type A and FMD virus
type O was also detected in samples collected from two calves in contact to sheep challenged indirectly with FMD virus type O); This result showed occurrence of transmission of FMDV from sheep challenged with FMD to free calves, so that cattle is considered as the main susceptible host to FMDV and that primary mode of animal to-animal transmission through inhalation or ingestion of aerosols containing the virus In conclusion, persistent infection in ruminants “carrier state” is an important feature of FMDV in infected and probably in vaccinated ruminants following exposure to infection especially sheep that play an important role in persistence or spread of FMD virus, So, highly potent, highly antigen payload, inactivated FMDV vaccine that confer early and rapid protective immunity against aerosol challenge in sheep within\14 days and inhibit local virus replication so prevent the carrier status in sheep.