Field evaluation of avian encephalomyelitis maternal antibody transfer in chicken flocks in Southwest Nigeria

O.A. Oladele1* C.O. Onwuka1

Keywords Summary Poultry – Avian encephalomyelitis Avian encephalomyelitis (AE) is controlled by ensuring adequate level of virus – Layer chicken – Broiler maternal antibodies in chicks. Incessant outbreaks in chicken flocks in South­ PATHOLOGIE INFECTIEUSE PATHOLOGIE

chicken – Hemagglutination test – west Nigeria in spite of vaccination of breeders prompted the assessment of

Vaccination – Nigeria. AE virus antibody levels in breeder flocks and their progeny. Five prevac­ ■ cinated chicken breeder flocks (A, B, C, D and E) were selected in Ibadan, Oyo State, and Mowe, Ogun State. Blood samples were collected from fif­ teen breeders from each flock, as well as their chicks at 1, 7 and 14 days of age and sera subjected to the passive hemagglutination test. Ranges of titers, modal titers, mean geometric titers (MGTs) and maternal antibody transfer rates were determined for each flock. MGTs ranged between 3.3 ± 0.09 and 4.8 ± 0.14 in breeder flocks, 0.8 ± 0.09 and 2.4 ± 0.21 in day-old chicks, and 2.8 ± 0.15 and 3.9 ± 0.06 in 7-day-old chicks. The highest values in all categories were observed in broiler flock D. MGTs ranged between 1.4 ± 0.18 and 2.3 ± 0.17 in 14-day-old chicks, and the highest value was found in broiler flock C. In general, significant (p < 0.05) declines in MGTs were recorded from breeder flocks to day-old chicks. Maternal antibody transfer rates were higher in broiler flocks C and D with 50 and 40.9%, respectively, whereas those of pullet flocks A, B and E were 24.2, 19.5 and 19.5%, respec­ tively. Results showed that by six months post-vaccination, maternal antibody transfer was low especially in pullet flocks, resulting in low to undetectable antibody titers in day-old chicks. A modification of the vaccination schedule is therefore advised.

■ INTRODUCTION Avian encephalomyelitis virus (AEV) belongs to the Picornavir­ idae family and was temporarily classified as a Hepatovirus due Avian encephalomyelitis (AE) is an infectious viral disease of to its relatedness to hepatitis A virus (6, 10). It has recently been poultry, which occurs in young chickens, turkeys, pheasants, Jap­ re-classified as a Tremovirus (6) and only one serotype exists, i.e. anese quails, pigeons, ducklings and partridges (4, 17, 19). It is AEV-1. All strains are enterotropic but some strains are more neu­ characterized by clinical signs of central nervous system disorder, rotropic than others, thus exhibiting varying levels of pathogenic­ particularly ataxia and tremors of the head, neck and limbs from ity (6). The disease occurs worldwide including Nigeria (2), Zim­ where the name epidemic tremor was derived. The clinical signs babwe (5) and Sudan (1). AE is a disease of economic concern to are usually accompanied by high morbidity and variable mortal­ poultry farmers as it causes decrease in egg production in layers, ity. Older poultry can become infected but rarely develop clinical decrease in hatchability, neurologic signs in chicks, and survivors signs, except a drop in egg production in layers (6). are considered unprofitable (14). Control is mainly by vaccination of breeders and layers with live 1. Department of Veterinary Medicine, University of Ibadan, Ibadan, Nigeria. or inactivated vaccine before the onset of laying to prevent verti­ Tel: +234 806 113 8531 cal transmission of the virus and ensure transfer of maternal anti­ E-mail: [email protected] / [email protected] bodies to progeny. Transfer of maternal antibodies from hens plays

* Corresponding author a crucial role in the protection of chicks against many poultry tropicaux, 2013, 66 (2) : 47-50 des pays et de médecine vétérinaire Revue d’élevage 47 Avian encephalomyelitisantibodytransfer

48 Revue d’élevage et de médecine vétérinaire des pays tropicaux, 2013, 66 (2) : 47-50 ■ PATHOLOGIE INFECTIEUSE weeks ofage. sitization). The suspensionofsensitizedRBC wascentrifuged, volume ofRBCsuspensionand incubatedfor2hat37°C(sen- in PBS. AEV vaccinediluted1:10inPBSwasmixed withanequal acid inPBS,pH6.4,for30min at56°Candsubsequentlywashed malinized RBCwasincubated with asolutionofdilutedtannic repeated washingindoubledistilled water. The suspension offor 37°C (i.e.formalinization).Excess formalinwasremovedby incubated with equal volume of3%formalin inPBSfor20hat buffered threetimes inphosphate washed Itwas saline(PBS). A suspensionofturkeyredbloodcells(RBC)washarvestedand inoculation. afterthesecond tendays forserum, sampled were the chickens The procedurewasrepeatedtwicewithinthreeweeksafterwhich AE vaccine(Calnek,Italy)equivalentto10doses,intramuscularly. icine negative (which tested to AE virus antibody), with diluted disease-free flockbelongingtotheDepartmentof Veterinary Med­ serum wasdevelopedbyinoculatingtwoadultchickensfrom a as describedbyPennerandHennessy(15).Knownpositiveanti ­ Serum samplesweresubjectedtopassivehemagglutinationassay Passive hemagglutinationtest as at7and14daysofagebyjugularvenipuncture. from eachflockatone-day-oldterminally(intracardially),aswell samples werealsocollectedfromtwelveofthetwenty-fivechicks presence of AE antibodieswithinoneweekofcollection.Blood vested intoeppendorftubes,storedat-20°Candtestedforthe room temperature andallowedtoclot.Serumsampleswerehar vacutainer tubes.Bloodsampleswereleftslantedonthebenchat and weresampledforblood(3ml)viathejugularveinintoplain Fifteen chickenswererandomlyselectedfromeachbreederflock Blood collection Feed pled forblood. They werefedwithbroilerchickstarter(UAC Vital ­ sam were daytheparentstocks batch ofeggslaidonthesame pens perflockforeaseofmonitoring. The chickshatchedfromthe at adifferent locationinanopen-sidedhousingfacility, in separate Twenty-five day-old chickshatched from each flock were housed were housedinnaturallyventilatedopen-sidedhouses. stock Ewas43weeksofageandvaccinatedat11 weeks. A-Ozzano Emilia{BO}–Italy)at13weeksofage,whereasparent and werevaccinatedwith AE livevaccine(Calnek114, FATRO s.p. A, B,CandDwere36,71,3645weeksofage,respectively, flocks Cand Dconsisted of Anak broiler breeders. Parent stocks Flocks A, BandEconsistedofIsaBrownpulletbreeders, in IbadanwhereasbreederflocksDandEwerelocatedMowe. State, inNigeria,wereused.Breederflocks A, Band Cwerelocated from twoselectedfarmsinIbadan,OyoState,andMowe,Ogun Five chickenbreederflocksdesignatedas A, B,C,DandE, Chicken flocks ■ MATERIALSMETHODS AND fer rateswerealsodetermined. antibody levelsintheirrespectivechicks.Maternaltrans­ post-vaccination inselectedchickenbreederflocksandmaternal study wasthereforeconductedtoassesstitersof AE antibodies Nigeria inspiteofbreedervaccinationremainachallenge. This ever, incessant outbreaks of AE in poultry farms in Southwest two tothreeweeksandisbelievedbelonglasting(18).How­ pathogens (16),inparticular AE virus(20).Immunity developsin

® ) andmultivitamins(Vitalyte

® ) wereadministeredtilltwo

They

­ ­

titer oftherespectiveserumsample. agglutination ofredbloodcellswasrecordedasthe AE antibody at roomtemperaturefrom40minto1h. The lastwellshowing plate weremixedgentlyonamicroshakerandallowedtoincubate were thenaddedintoeachwell. The contentsofthemicrotiter Fifty microliters of 1% AE antigen sensitized RBC suspension the rowstilleleventhwellfromwhich50µlwerediscarded. each rowofwells. A double-foldserialdilutionwascarriedoutin otiter plate,then50µlofseraweredispensedintothefirstwellin Fifty microliters of PBSwere dispensed intoeach well of the micr a finalconcentrationof1%. washed threetimesinPBS,andRBCwerere-suspendedPBSto 40.9, 50.0and19.5%inflocks A, B,C,DandE,respectively. body transferfromparentstockstoday-oldchickswere24.2,19.5, significant (p<0.05)declinesat14days.Ratesofmaternalanti­ This wasfollowedbysignificant(p<0.05)increasesat7daysand were observedfromparentstockstoday-oldchicks(Figure1). (p<0.05)in Significant declines antibody titers,i.e.MGTs,AE between 1.4and2.3. respectively, and24 simultaneously inflockE;MGTs ranged 8,4and8inflocks modaltiterswere flocks, B,CandD, A, MGTs rangedbetween2.8and3.9atthisage.In14-day-oldchick the modaltiterwas8inflocks A, B,CandE,16inflockD. MGTs rangedbetween0.8and2.4.Inthe7-day-oldchickflocks, 2, 0,4,8andinflocks A, B,C,DandE,respectively, andtheir between 3.3and4.8.Intheday-oldchickflocks,modaltiterswere group in flocks C and D. MGTs of the five parent stocks ranged B and E, and they were 16and 32simultaneously within each ent stocks,modaltiterswere8inflock A, and16inbothflocks of flocks A, B,C,DandEarepresentedin Table I.Inthepar Ranges ofantibodytiters,modaltitersandmeangeometric ■ RESULTS analysis ofvarianceandDuncan’s multiplerangetest. between flocks at each sampling time and within flocks using the mean titer of the respective breeder flock. MGTs were compared expressing themeanantibodytitersin chicks aspercentageofthe transfer fromparentstockstochickswerealsodeterminedby ens weredeterminedandrecorded.Ratesofmaternalantibody ring titer)andmeangeometrictiter (MGT) ofeach flock ofchick­ Range of antibody titers, modal titer (i.e. most frequently occur Analysis

transfer in selected breeder flocksinSouthwesttransfer inselected breeder Nigeria. Figure 1: Mean geometric titer (MGT) 0 1 2 3 4 5

A Avian encephalomyelitis virusmaternalantibody

Breeder groupsandprogeny Breeders

B

Day-old chicks

C

D E ­ ­ ­

Transfert des anticorps contre l’encéphalomyélite aviaire

Table I West Nile virus maternal antibody titers and extended decay period Avian encephalomyelitis virus antibody passive in chicks whose dams had high titers. hemagglutination titers in breeder flocks and progeny Vaccination programs for the control of most viral diseases of chickens such as Newcastle disease and infectious bursal disease Flock Class Range Modal Mean Rate of usually comprise one or two live vaccines administered early in of titers titer geometric maternal life, as well as an inactivated (killed) vaccine administered prior titer antibody to lay in order to ensure transfer of high level maternal antibody transfer (%) to progeny (12, 13). However, the breeder flocks investigated in this study were vaccinated only once with a live AE vaccine at A Parent stock 8-16 8 3.3 ± 0.09a 24.2 either 11 or 13 weeks of age as recommended by the manufacturer Day old 0-2 2 0.8 ± 0.09c and which is the usual practice in the industry (6). This schedule 7 days old 0-16 8 2.9 ± 0.23a contrasts with multiple vaccinations used for the control of most diseases of poultry (6). It is our belief that the administration of 14 days old 0-8 8 2.2 ± 0.19b a single live vaccine to these breeder flocks was responsible for

a the generally low antibody levels in parents with subsequent low B Parent stock 8-32 16 4.1 ± 0.11 19.5 to undetectable levels in day-old chicks. Day old 0-8 0 0.8 ± 0.19d 7 days old 4-16 8 2.9 ± 0.16b The absence of detectable antibodies observed in some day-old chicks in most of the flocks is undesirable at this age as it may 14 days old 0-8 8 1.8 ± 0.26c provide a portal of entry of infection into the flock. The higher maternal antibody titers, reflected by MGTs recorded at 7-day-old a C Parent stock 8-64 32,16 4.4 ± 0.15 40.9 compared with day-old and 14-day-old titers, are believed to result Day old 2-4 4 1.8 ± 0.08c from further release of immunoglobulins (IgY) from yolk sac into 7 days old 4-16 8 2.8 ± 0.15b chick immediately post hatching. According to Vegad (18), the 14 days old 0-8 4 2.3 ± 0.17c level of maternal antibodies in circulation of newly hatched chicks peaks at about 2-3 days of age and decreases thereafter to unde­ D Parent stock 16-64 32,16 4.8 ± 0.14a 50.0 tectable levels by 2-5 weeks of age. Day old 0-8 8 2.4 ± 0.21c The passive hemagglutination test used in this study was declared 7 days old 8-16 16 3.9 ± 0.06b to be more sensitive than the immunodiffusion test which can 14 days old 0-8 8 2.0 ± 0.23c detect antibodies as early as four days post-inoculation of AE virus (3). Thus, the absence of detectable antibodies in the serum E Parent stock 8-32 16 4.1 ± 0.12a 19.5 of a large proportion of day-old chicks, which indicates inefficient Day-old 0-2 2 0.8 ± 0.09c transfer of maternal antibodies as a result of low levels in parent stocks, highlights the need to revise the vaccination schedule. 7 days old 2-16 8 3.0 ± 0.17b 14 days old 0-8 2,4 1.4 ± 0.18c ■ CONCLUSION Values with different superscripts are significantly different (p < 0.05) This study showed that by six months post-vaccination of breed­ ers, AEV antibodies were low resulting in the inefficient trans­ ■ DISCUSSION fer of maternal antibodies to chicks especially in pullet breeders. The administration of a secondary vaccine is therefore advised to Chicks depend on maternal antibodies as the main source of boost the primary immune response. This should be an inactivated immune protection until they become immunocompetent. Our or killed vaccine administered prior to laying in order to prevent objective was to evaluate the capacity of chicks from vaccinated vertical transmission of the virus via eggs and decrease in egg pro­ parent stocks to withstand challenges of avian encephalomyelitis duction, which could occur with the use of live vaccines after the outbreaks in poultry farms in Southwest Nigeria. As a first step, we onset of lay. assessed the rate of maternal antibody transfer from AE vaccinated hens to their progeny. There was a decrease in modal titers from breeder stocks (8-32) to day-old chicks (0-8). Also, MGTs reduced REFERENCES significantly (p < 0.05) from range 3.3–4.8 in breeder stocks to 0.75–2.41 in day-old chicks with transfer rates ranging from 19.5 1. ABDELLAH E., BALLAL A., ABDELRAHIM S., 2007. Avian to 50%. This decrease in antibody levels from parent stocks to day­ encephalomyelitis virus in Sudan. Res. J. Anim. Vet. Sci., 2: 9-11. old chicks is a regular occurrence in poultry health management 2. ADENE D.F., FABIyI S., BABARINDE Z.O., 1976. Isolation of avian (7). Hamal et al. (8) reported a dam-to-chick antibody transfer of encephalomyelitis virus in Nigeria. Bull. Anim. Health. Prod. Afr., 24: 9-12. approximately 30%. In our study, transfer rates of 40.9 and 50% 3. AHMED A.A.S., ABOU EL-AZM I.M., AyOUB N.N.K., TOUKHI were obtained for the two broiler flocks C and D, respectively. By B.I.M.E., 1982. Studies on the serological detection of antibodies to avian encephalomyelitis virus. Avian Pathol., 11: 253-262. contrast, it was 24.2, 19.5 and 19.5% in the three pullet flocks A, B and E, respectively. Sharma (16) evidenced a relation between 4. BODIN G., PELLERIN J.L., MILON A., GERAL M.F., BERTHELOT X., LAUTIE R., 1981. Etude de la contamination expérimentale du high maternal antibody transfer efficiency and high antibody level gibier à plumes (faisans, perdrix rouges, perdrix grises), par le virus de in parent stock. Thus, the two broiler parent flocks C and D, which l’encéphalomyélite infectieuse aviaire. Rev. Méd. Vét., 132 : 805-816. had the highest antibody titers in this study, i.e. 4.4 ± 0.15 and 5. CADMAN H.F., KELLy P.J., ZHOU R., DAVALAAR F., MASON P.R., 4.8 ± 0.14, respectively, also had the highest maternal antibody 1994. A serosurvey using enzyme-linked immunosorbent assay for transfer rates compared with the pullet parent flocks. This finding antibodies against poultry pathogens in ostriches (Struthio camelus) from also concurred with Nemeth and Bowen (11) who reported high Zimbabwe. Avian Dis., 38: 621-625. tropicaux, 2013, 66 (2) : 47-50 des pays et de médecine vétérinaire Revue d’élevage 49 Avian encephalomyelitisantibodytransfer

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20. reared pheasants:acasestudy. Avian Pathol., V.J.,D., TODD 19. ebooksfreedownload.org/2011/04/a-colour-atlas-of-poultry-diseases poultry professionals.InternationalBookDistributingp.83-85.http:// 18. infected pigeonsin Turkey. Avian Pathol., 17. development ofthedisease.Aust. Vet. J., avian encephalomyelitis. IV. The effectofmaternalantibody onthe nación – Vacunación –Nigería. Gallina ponedora –Pollo deengorde–Pruebahemagluti ­ Palabras clave: Ave de corral – Virus encéfalomielitis aviar – ción delosesquemasvacunación. de undíaedad.Por lotantose recomiendaunamodifica­ titulaciones deanticuerposbajas onodetectablesenpollitos baja, especialmenteenlasparvadas depollitas,resultandoen post vacunación, latransferencia deanticuerposmaternosfue pectivamente. Elpresenteestudiomostróquealosseismeses los grupos de pollitas A, B y E fueron 24,2, 19,5 y 19,5%, res­ de engorde,con50y40,9%,respectivamente, mientras que maternos fueronmáselevadas enlosgruposCyDdepollos de undíaedad.Lastasastransferencia deanticuerpos vas (p<0,05) en MGTs en parvadas de reproductores a pollitos engorde. Engeneral, seregistraron disminucionessignificati­ valor más elevado se encontró en el grupo C de pollos de enpollitosde14díasedadyel y2,3± 0,17 1,4 ± 0,18 ron enelgrupoDdereproductores.LosMGTvariaron entre valores máselevados detodaslascategoríasseobserva­ 2,8 ± 0,15 y 3,9 ± 0,06 en pollitos de 7 días de edad. Los enpollitosdeundíaedady y2,4± 0,21 res, 0,8± 0,09 0,14 en parvadas de reproducto­ 0,09 y 4,8 ± entre 3,3 ± anticuerpos maternos para cada grupo. Los MGTs variaron laciones geométricas (MGTs) y tasas de transferencia de los determinaron losrangos detitulación,promedioslastitu­ sueros sesometieronaltestdehemoaglutinaciónpasiva. Se grupo, asícomosuspollitos,de1,7y14díasedad,cuyos estado de Ogun. Se sangraron quince reproductores de cada (grupos A, B, C,DyE)en Ibadan,estadodeOyo, Mowe y ron cinco parvadas depollos reproductores prevacunados parvadas dereproductoresysusprogenituras. Seselecciona­ luación delosniveles deanticuerposcontra elvirus AE en pesar delavacunación delosreproductores,impulsólaeva­ tantes, enparvadas depollosenelsuroesteNigeria,a adecuado deanticuerposmaternosenpollitos.Brotescons­ La encefalomielitisaviar (AE)secontrolaasegurando unnivel tis aviar enparvadas depollosenelsuroesteNigeria transferencia deanticuerposmaternoscontra laencefalomieli­ Oladele O.A., Onwuka C.O. Resumen Accepté le15.1 15. Books. ISBN978-029-097-4 Poultry productioninwarm wetclimates.Ibadan,Nigeria,Spectrum 14. OLUyEMIJ.A.,ROBERTS F.A., 2007. Avian encephalomyelitis. In: technique for serotyping Campylobacter fetus Diseases ofpoultry, 11 Barnes H.J.,GlissonJ.R.,Fadly A.M., McDouglasL.R.,Swayne D.E., Eds, 16. of solubleheatstableantigens.J. Clin. 12:732-737. Microbiol.,

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Evaluación de campo de la 54: 81-85. 33: 381-386. 38: 251-256.

subsp. jejuni

on thebasis