NZ Lifestyle Block - - Your Poultry -

THE CLIN­I­CAL SIGNS OF MAREK’S dur­ing an acute out­break will be signs of de­pres­sion, with birds stand­ing around look­ing ‘off colour’. This could be fol­lowed by lame or paral­ysed birds. Mor­tal­ity may oc­cur with no symptoms at all or there may be pale­ness, loss of ap­petite, di­ar­rhoea and de­hy­dra­tion, gasp­ing, or blind­ness. Note: many of th­ese are also symptoms of other dis­eases.


• Im­mune sup­pres­sion and sus­cep­ti­bil­ity to dis­eases like coc­cid­io­sis and black­head. • Paral­y­sis, no­tably where a bird will have one leg for­ward and one leg back, but it may also drag one leg or wing as if it is bro­ken. This may oc­cur be­tween 6-12 weeks old but it’s also seen up un­til sex­ual ma­tu­rity (20-25 weeks). • The nerves to the brain and neck may cause the head to bend un­der or twist to one side. The virus af­fects the ma­jor nerves to the legs or wings and the bird is un­able to flex the mus­cles. • A con­di­tion pre­vi­ously known as range or tran­sient paral­y­sis may also be due to the Marek’s virus. • When the op­tic nerve is in­volved the iris may ap­pear to be grey and the pupil be­comes dis­torted and/ or blind­ness is ap­par­ent. This can de­velop much later in life, es­pe­cially if the bird has been un­der stress. • The vis­ceral form which causes tu­mours, no­tably the ovary, liver, kid­neys or lungs is most usu­ally seen in weeks 10-15. Tu­mours present in young birds sug­gest Marek’s dis­ease but in older ma­ture birds are more likely to be caused by an­other dis­ease called lym­phoid leu­co­sis. Tu­mours on the skin which may ap­pear as bleed­ing feather fol­li­cles that won’t heal may oc­cur in young birds as well.

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