Fowl pox spreads by mosquitoes and wounds; Marek's travels in feather dust. What each looks like, when vaccines are given and why Marek's is a hatchery job.
Halaal Farms Ghana team4 October 2026 · 12 min read
Fowl pox and Marek's disease have almost nothing in common as diseases. One puts scabs on combs and is carried by mosquitoes. The other paralyses legs, grows tumours and travels on the dust from feathers. What they share is this: once signs appear no medicine cures either, and both are prevented by a vaccine given once. The difference that matters to you is who gives it. Pox vaccine goes through the wing web on your own farm when the birds are some weeks old. Marek's vaccine has to go in on the day of hatch, before the chick leaves the hatchery, and if it was missed there is no catching up.
Fowl pox is a slow-moving viral disease of chickens and turkeys of any age. It takes two forms, and both can be present in one flock.
Small pale, raised spots appear on the bare skin of the comb, wattles, eyelids and the corners of the beak, and sometimes on the legs or under the wings. Over several days they grow, turn yellowish, then become rough, dark brown scabs that look like warts. After three to four weeks the scabs dry and fall off, leaving a scar. Most birds with the dry form keep eating. The trouble comes when scabs on the eyelids close the eyes, because a bird that cannot see cannot find feed or water. Growth slows, egg production falls, and cockerels meant for sale look unsightly at exactly the wrong time.
Here the damage is inside. Raised, yellow-white cheesy patches form on the tongue, the roof of the mouth, the throat and the opening of the windpipe. Birds gasp, swallow with difficulty and stop eating. Deaths are few in the dry form but can be heavy in the wet form, where birds suffocate or starve.
A scratch from fighting is flat, heals within days and does not spread from bird to bird. Pox lesions are raised and warty, take weeks to clear, and week by week more birds show them.
The pox virus cannot pass through healthy, unbroken skin. It needs a way in, and it has three.
Around the farm, the practical work is to remove mosquito breeding sites: old tyres, tins, broken drinkers, blocked gutters, open tanks and any container that holds rainwater for a week. Keep grass and bush cut short around the houses.
Any bird that will be kept for months should be vaccinated: layer pullets, breeders, cockerels, local chickens and dual-purpose birds such as Sasso, Kuroiler and Noiler. Turkeys get pox as well, so if you rear turkey poults, ask your vet about protecting them. Broilers sold at six to seven weeks are commonly left out.
As a typical example, pullets are vaccinated once at around six to ten weeks of age, and in any case well before they start to lay. Where mosquitoes are heavy and pox strikes young birds, some programmes vaccinate earlier. Your vet sets the timing, and our article on vaccination schedules for broilers and layers shows where pox sits among the other vaccines.
The vaccine is a live virus, supplied dried with a bottle of diluent and a two-pronged applicator. One person holds the bird and spreads a wing so that the wing web, the triangle of thin skin at the front of the wing between the shoulder and the wrist joint, is exposed from underneath. The vaccinator dips the prongs fully into the mixed vaccine and pushes them straight through the web.
Handling technique for all the vaccine routes is covered in our guide to giving poultry vaccines properly.
Pox is one of the few vaccines where you can see whether the job worked. Seven to ten days after vaccination, catch a sample of birds from different parts of the house, 50 is a sensible number, and look at the wing web. A successful vaccination leaves a small swelling or scab at the puncture site, called a take. It disappears within two or three weeks.
Nearly every bird should show one. If many do not, the vaccine was dead (too warm, too old or used too long after mixing), the technique was poor, or birds were missed. Tell your vet, who will usually advise repeating the vaccination. Record the date, the batch number of the vaccine and the result of the check.
No drug acts on the virus. The outbreak runs its course, and the aim is to keep birds eating and drinking until the scabs fall.
When the flock is sold, clean the house thoroughly and remove the dust, because fallen scabs keep the virus alive for the next batch.
Marek's disease is caused by a herpesvirus of chickens. It infects white blood cells and turns some of them into tumour cells, which then invade nerves and organs. Signs seldom appear before six weeks of age and are most common between about three and seven months, with the stress of coming into lay a typical trigger. That timing is cruel for a layer farmer: the losses come after months of rearing cost and before many eggs have been sold.
The disease shows itself in several ways.
Marek's does not arrive as a wave of deaths. It is a steady drip: one or two birds a day or a week, for weeks on end. In an unprotected flock the total can reach a third of the birds or more. The virus also weakens the immune system, so affected flocks suffer more from other diseases and respond less well to other vaccines.
Several conditions resemble it. Newcastle disease also causes paralysis and twisted necks, but it hits many birds at once, usually with breathing signs and green droppings. Curled toes and weak legs in chicks of two to four weeks point to a vitamin shortage in the feed, not Marek's. Leg injuries affect single birds and do not progress. Other tumour diseases occur in adult hens without the paralysis. A vet separates these by opening birds and examining the main leg nerves, which are thickened and dull in Marek's disease, and the internal organs.
The Marek's virus finishes its development in the skin around the feather follicles. It leaves the bird in the tiny flakes of skin and feather that make up much of the dust in a poultry house. Chicks become infected by breathing that dust in.
Three features make the virus hard to avoid. It survives in house dust and litter for many months. An infected bird sheds it for life, whether or not it ever looks sick. And the dust travels: on clothes, hair, egg trays, crates, equipment and the wind between houses. The virus is not passed through the egg, so a chick hatches clean and is infected by its surroundings.
This creates a race. A vaccinated chick needs roughly one to two weeks to build full protection. A chick placed in a house that still holds dust from the last flock, or brooded beside older birds, starts breathing field virus on day one. If the field virus gets established before the vaccine has done its work, the bird can develop Marek's disease in spite of being vaccinated. Younger chicks are also far more easily harmed by the virus than older ones, so every day of delay in exposure helps.
Everything about this vaccine points to the hatchery.
Our article on how a hatchery works, from fertile egg to boxed chick, shows where vaccination fits into hatch day.
Two more facts keep expectations realistic. First, the vaccine prevents tumours and paralysis but does not stop infection. Vaccinated birds can still carry and shed the field virus, so hygiene still matters. Second, layer and breeder chicks are routinely vaccinated against Marek's, while broilers, which are sold long before the usual age of disease, often are not. For dual-purpose and slow-growing birds kept for several months, ask.
Chicks from Halaal Farms Ghana are vaccinated at the hatchery before they leave. When you order, ask exactly which vaccines your batch has had and note it in your flock record. Chicks hatched in small backyard incubators and sold informally have very often had no Marek's vaccine at all, which is one of the hidden costs of a cheap pullet chick.
The hatchery gives the vaccine. You give it time to work.
| Point | Fowl pox | Marek's disease |
|---|---|---|
| How it spreads | Mosquitoes, skin wounds, dust from dried scabs | Feather and skin dust breathed in |
| Usual age | Any age | Signs from about 6 weeks, mostly 3 to 7 months |
| What you see | Warty scabs on comb, wattles and eyelids; cheesy patches in mouth and throat | Lameness and paralysis, wasting, grey eyes, tumours on post-mortem |
| Pattern of loss | Slow spread over weeks; few deaths unless the wet form is present | A steady trickle of cases over weeks or months |
| Vaccine given | On the farm, wing-web stab, typically at 6 to 10 weeks | At the hatchery, injection at day-old or into the egg |
| Can you check it worked | Yes, look for takes at 7 to 10 days | No visible sign; rely on the hatchery's record |
| Treatment | None; nursing care | None; cull affected birds |
| Risk to people | None | None |
Both diseases are decided long before you see a sick bird, so the useful questions come at ordering time. Was Marek's vaccine given at hatch? What else was given, and by which route? Our list of questions to ask a hatchery before you buy chicks covers the rest. Then write the fowl pox date into your own programme with your vet, buy the vaccine from a shop that keeps it refrigerated, and plan who will hold birds on the day.
For layer or dual-purpose chicks, or advice on preparing a brooding house apart from your older stock, call Halaal Farms Ghana on 024 915 1503 or send the order form. The minimum order is one box of 50 chicks, and we deliver to all 16 regions.
No. Fowl pox is a bird virus and has nothing to do with human chickenpox, despite the similar name. Marek's disease virus infects chickens and is not known to cause illness in people. Meat and eggs from healthy birds in an affected flock are safe to eat. Sick, wasted or dead birds should not be sold or eaten, as with any disease.
Not usefully. The vaccine has to be in the chick before it meets the field virus, which happens within hours of placement in most poultry houses, and it needs a week or two to protect. The most effective vaccines are also stored in liquid nitrogen and injected chick by chick. Buy pullet chicks that were vaccinated on the day of hatch.
Usually not. Broilers sold at six to seven weeks leave the farm before pox would normally do much harm, so most programmes leave it out. Birds kept longer, such as layers, cockerels, Sasso, Kuroiler, Noiler, local chickens and turkeys, should be vaccinated. On a farm with a history of pox in young birds, ask your vet whether earlier vaccination is worthwhile.
An individual bird carries scabs for about three to four weeks before they dry and fall off. Because pox spreads slowly from bird to bird, the outbreak in a whole house often runs for six to eight weeks or longer. During that time growth slows and egg production falls. Birds that recover are immune afterwards.
Almost never. The paralysis comes from tumour cells invading the nerves, and it gets worse, not better. The bird cannot reach feed and water, loses weight and is trampled, and all the while it sheds virus in its feather dust. Once a vet has confirmed the cause, affected birds should be culled humanely and disposed of away from the flock.
Written by the Halaal Farms Ghana team. We hatch and import day-old chicks at Opeikuma, Kasoa, and deliver to all 16 regions. This article is general guidance for farmers. For diagnosis and treatment of sick birds, speak to a vet or your district veterinary office.
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