THE EFFICACY OF VACCINATION OF LAYER CHICKENS WITH INACTIVATED FOWL CHOLERA BACTERIN PREPARED FROM LOCAL EGYPTIAN STRAINS OF Pasteurella multocida

Abstract

This study was carried out to evaluate the efficacy of vaccination of layer chickens with inactivated FC bacterin prepared from local Egyptian strains of Pasteurella multocida (P. multocida). A total of 200 layer chickens were divided into 5 equal groups, 40 for each. At the age of 6 weeks, chickens in groups (A) and (B) were vaccinated with P. multocida serotypes A:1 and A:3, respectively, booster doses were given after 3 weeks (9 weeks old) and challenge was done with virulent serotypes A:1 and A:3 at 2 weeks later (11 weeks old). Chickens in groups (C) and (D) were not vaccinated, only challenged with P. multocida serotype A:1 and A:3, respectively. Birds in group (E) were kept as non-vaccinated and non-challenged. Blood samples were collected weekly from all groups for humoral immune response. All the birds were kept under observation for signs, mortalities, lesions and re-isolation of challenging organism and for histopathological examination. Results of the mean Enzyme Linked Immuno-Sorbent Assay (ELISA) revealed that the highest level was at 5 weeks post vaccination as the titers reached to 3970 in group (A) and 3905 in group (B). The clinical signs, mortality rate and lesions were mild in the vaccinated birds while severe lesions were in non-vaccinated and challenged birds. The protection rates were 85 % and 80 % in groups (A) and (B); respectively, while 10 % and 20 % in groups (C) and (D); respectively. The re-isolation rates of P. multocida after challenge were 95 % and 90 % in non-vaccinated-challenged birds with P. multocida serotypes A:1 and A:3; respectively, while they were 25 % and 15 % in vaccinated-challenged groups with P. multocida serotypes A:1 and A:3; respectively. Histopathological examination of P. multocida vaccinated-challenged birds revealed mild to no microscopic lesions when compared with non-vaccinated challenged chickens. In conclusion, the prepared FC inactivated bacterin from the local Egyptian predominant P. multocida serovars proved efficacy and protection of layer chickens. Key words: Pasteurella multocida; chickens; immunization; protection; Egypt UČINKOVITOST CEPLJENJA KOKOŠI NESNIC Z INAKTIVIRANO BAKTERIJO KOLERE PERJADI, PRIPRAVLJENE IZ LOKALNIH EGIPTOVSKIH SEVOV BAKTERIJE Pasteurella multocida Povzetek: Raziskava je bila izvedena z namenom ocenitve učinkovitosti cepljenja kokoši nesnic z inaktivirano bakterijo FC, pripravljeno iz lokalnih egiptovskih sevov bakterije Pasteurella multocida (P. multocida). Skupno 200 kokoši nesnic je bilo razdeljenih v 5 enakih skupin. V vsaki skupini je bilo 40 kokoši. Pri 6 tednih smo kokoši v skupinah A in B cepili s serotipoma P. multocida A:1 in A:3, po 3 tednih, ko so bile živali stare 9 tednov, so dobile poživitvene doze cepiva. Po dveh tednih (v starosti 11 tednov) so bile kokoši okužene z virulentnima serotipoma A:1 in A:3. Piščanci v skupinah C in D niso bili cepljeni temveč samo okuženi s serotipoma A:1 in A:3. Kokoši v skupini E niso bile niti cepljene, niti okužene. Vzorci krvi so bili odvzeti pri vseh skupinah tedensko za preverjanje humoralnega imunskega odziva. Vse kokoši smo stalno opazovali in beležili prisotnost bolezenskih znakov, različnih ran in umiranje kokoši. Pri poginulih kokoših smo osamili bakterije ter opravili histopatološki pregled. Rezultati encimsko-imunskega testa (ELISA) so pokazali da je bila najvišja stopnja zaščite dosežena 5 tednov po cepljenju, saj so titri dosegli 3970 v skupini A in 3905 v skupini B. Klinični znaki, stopnja umrljivosti in rane so bili pri cepljenih kokoših blagi, hude rane pa so bile vidne pri necepljenih in okuženih kokoših. Stopnja zaščite je bila v skupinah A in B 85- oziroma 80-odstotna, v skupinah C in D pa 10- oziroma 20-odstotna. Stopnje ponovne izolacije P. multocida po okužbi so bile 90 in 95 odstotkov pri kokoših, ki niso bile cepljene, medtem, ko so bile v skupinah, ki so bile okužene s P. multocida serotipa A:1 in A:3 15- in 25-odstotkov. Histopatološki pregled cepljenih in okuženih kokoši je pokazal popolno odsotnost ali prisotnost blagih mikroskopskih poškodb, medtem ko so imele necepljene okužene kokoši bolj obsežne histopatološke poškodbe. Pripravljena inaktivirana bakterija FC iz lokalnih egiptovskih prevladujočih serovarov P. multocide se je izkazala za učinkovito zaščito kokoši nesnic.Ključne besede: Pasteurella multocida; kokoši; imunizacija; zaščita; Egipt