Alison Colville-Hyde, Technical Support at Chicken Vet

Marek’s disease is commonly experienced by the hobby keeper who hatches and rears rare breeds, and those hatching a few chicks alongside keeping older birds. It is a disease which can cause much upset with keepers, particularly if they have never come across the disease before. Diagnosis is not completely straightforward as there is no serology option. Post mortem and histology are the most reliable ways to confirm the disease. Marek’s is caused by a herpes virus which attacks nerves and causes paralysis and/or the formation of tumours; commonly seen in the spleen and liver. Usually, birds over six weeks of age are affected. Pullets coming into lay can also succumb to this disease if unvaccinated. Birds initially become withdrawn and depressed, with food intake and water consumption reducing. Rarely do they recover and there is no treatment apart from supportive therapy.

Many keepers enquire about vaccinating birds. It is only effective to vaccinate chicks at day old so the vaccine can start to work and protect chicks from any field challenge on site. Adult birds are not suitable for vaccination and there are no boosters needed for birds vaccinated in the chick stage. Marek’s vaccine is a one off which needs to be carried out as soon as possible once chicks have dried off.

The vaccine is presented as a freeze dried pellet in a glass vial. The smallest quantity available is 2000 doses. Until summer 2016, there was a 1000 dose size, but this has been discontinued by the vaccine manufacturer, as demand was not sufficient to continue producing it. The vaccine vial comes with a separate diluent in a drip bag style presentation; the two need mixing before vaccinating commences. Once mixed, the vaccine has a two hour life span, so you need to be prepared! The vaccine can be supplied through Chicken Vet and is called Poulvac MD.

Each chick needs 0.2ml injecting subcutaneously or intramuscularly and here we explain the procedure: 

What you need to get started

  • Vial and diluent bag - The pack below is the kit used by commercial vaccinators to attach to their automatic vaccinating guns; you will not need to use this, however, this pack contains a 5ml syringe and a 18g x 1.5’’ needle which you will require for reconstituting (mixing) the vaccine.

  • 1ml syringe with 21g x 3/8 needle


1. Using a 5ml syringe and an 18g x 1.5’’ needle, remove approximately 2.5ml from the diluent bag.

2. Remove the metal lid from the vial, not the rubber bung, inject the diluent into the vial and rotate to mix.

3. Once mixed, extract the solution and inject back into the diluent bag, rotate gently to mix and you are ready to start vaccinating. Remember, 2 hour life span. 

When vaccinating chicks for Marek’s disease, the neck is the best place to use. This is referred to as a subcutaneous (going through the skin) injection, as you inject under the skin.

Use a 1ml syringe and fine needle (21g x 3/8). You will find this the easiest option as holding a chick in one hand and injecting with the other can be difficult and fiddly. You can progress onto using an injecting gun once skilled and used to handling chicks. Some people find it easier to sit down and put the chick on their lap with a towel underneath so it can grip. Others prefer to have someone else hold the chick while they inject.

The skin on the back of the neck is lifted in a pinch action, to create a ‘tent’ or pocket underneath. It is into this pocket you inject the vaccine, being careful not to inject it out through the other side. If you do, refill the syringe and start again. The other location which can be used is the thigh muscle of a leg, but in a chick (especially a bantam chick) this can cause damage, so the neck is the preferred area to start on.

Use a box to hold the group of chicks you want to vaccinate, once a chick has been vaccinated place it under the heat so that you know which chicks have been done. This needs to be completed as carefully and as quickly as possible to minimise stress.

Once the group of chicks have been vaccinated, keep them separate from older birds for as long as possible, to reduce the risk of site challenge getting into their systems before immunity has developed. The crucial phase is 14 days, but the longer the better. Vaccination, along with good hygiene practices and separate rearing of age groups is key to reducing Marek’s on a multi-age site.

For more details, email info@chickenvet.co.uk or call 01392 872885.