BODY HEP­ATI­TIS

The Poultry Bulletin - - INCLUSION BODY HEPATITIS - By Obed M. Lukhele

A Ifield re­port on IBH over 4 years

nclu­sion body hep­ati­tis (IBH) is caused by the fowl ade­n­ovirus (FADV) which is made up of five geno­types or molec­u­lar groups A-E and twelve serotypes (17, 8a, 8b & 11). Ade­n­oviruses are ubiq­ui­tous in na­ture with an­ti­bod­ies against them found in healthy and dis­eased chick­ens mak­ing it dif­fi­cult to in­ter­pret sero­logic tests.

An­ti­bod­ies de­velop one week post in­fec­tion and reach peak lev­els af­ter three weeks. The hu­moral im­mu­nity is per­sis­tent while the lo­cal im­mu­nity is short-lived.

The in­cu­ba­tion pe­riod for IBH is short: 1-2 days. Sources of in­fec­tion are mainly hen-to-egg (ver­ti­cal) and oral-fae­cal (hor­i­zon­tal) with fac­tors such as im­muno­sup­pres­sion (in­fec­tious bur­sal dis­ease, chicken anaemia virus, my­co­tox­ins, etc.), im­muno­log­i­cally naïve broiler breeder par­ents and high chal­lenge on broiler

farm known to ex­ac­er­bate the oc­cur­rence of IBH.

Some strains of ade­n­oviruses in­fect and dam­age or­gans of the im­mune sys­tem such as the bursa, thy­mus and spleen re­sult­ing in im­muno­sup­pres­sion. As there are many serotypes and an­ti­bod­ies are serotype­spe­cific, it is prac­ti­cally not pos­si­ble to vac­ci­nate breed­ers against all known twelve serotypes.

Back­ground

In­clu­sion body hep­ati­tis, IBH, was first de­scribed in the USA in 1963 by Helm­bolt & Fra­zier, then in Canada, United King­dom, Ire­land, Aus­tralia, France and South Africa.

South African broiler cases that were re­ported in 2008 were most likely in­tro­duced through broiler breed­ers from the USA and Europe. Th­ese cases were as­so­ci­ated with non-spe­cific clin­i­cal signs such as de­pres­sion, loss in body weight, wa­tery drop­pings and weak­ness. Mor­tal­ity was acute in 2-29 day old broil­ers ranged from 10-20%. On post-mortem, ab­nor­mal­i­ties were no­ticed in the liver, spleen, kid­ney and giz­zard wall with histopatho­log­i­cal changes mainly in the liver; also kid­ney and spleen. The causative serotypes of the fowl ade­n­ovirus (FADV) were found to be 2 and 8a in th­ese 2008 cases.

In South Africa, IBH, is worth more at­ten­tion as it may be con­sid­ered an “emerg­ing” dis­ease since its first re­port­ing in 2008, and then our first field ex­pe­ri­ence in 2012.

Field Ex­pe­ri­ence October 2012 to April 2016

Our field re­port is based on thir­teen broiler flocks over about a fouryear pe­riod. Broil­ers at risk were ap­prox­i­mately 380,000 spread in three South African prov­inces, namely Gaut­eng, Mpumalanga and the Western Cape. The in­ci­dence of IBH from October 2012 to April 2016 av­er­aged 0.31% with no ap­par­ent sea­sonal ef­fect.

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