Gumboro strikes chicks at three to six weeks and weakens immunity for life. Signs, vaccine timing, outbreak care and how to clean the house afterwards.
Halaal Farms Ghana team4 October 2026 · 13 min read
Gumboro has a shape. A flock that was eating well on Monday stands hunched and ruffled on Tuesday, deaths climb steeply for three or four days, and then, almost as fast, the survivors get up and go back to the feeders. If your birds are between three and six weeks old and the losses follow that sharp rise and fall, infectious bursal disease (IBD), which every Ghanaian farmer calls Gumboro, belongs near the top of your list of suspects. The deaths are the part you see. The part you do not see, a damaged immune system in the birds that lived, often costs more.
The disease takes its name from Gumboro, a small town in Delaware in the United States, where it was first described in the early 1960s. The cause is a small, tough virus with one main target: the bursa of Fabricius, a rounded, cream-coloured sac that sits just above the cloaca, under the tail.
In a growing chick the bursa works like a training school. White blood cells called B lymphocytes mature there and go on to make antibodies, the proteins that attach to germs and to vaccine viruses and give the bird lasting protection. The bursa is busiest in the first weeks of life and shrinks naturally as the bird approaches sexual maturity.
The Gumboro virus multiplies inside those immature B cells and destroys them. Within three or four days of infection the bursa is swollen and inflamed. About a week later it has shrunk to a fraction of its normal size, with most of its working tissue gone. A bird that survives has a reduced ability to make antibodies for the rest of its life, and the younger it was when infected, the bigger the loss.
The virus causes disease only in chickens. It is not a danger to people.
Clinical Gumboro, the form with visibly sick birds and deaths, is mostly a disease of chicks from about three to six weeks old. Three things set that window.
Broilers therefore meet Gumboro around the fourth week, when each bird already carries a month of feed. Layer pullets and cockerels meet it early in rearing. Light breeds tend to suffer heavier death losses than broilers, so an outbreak in a pullet house can be severe. Sasso, Kuroiler, Noiler and local chickens are susceptible too.
Infected birds pass huge amounts of virus in their droppings for about two weeks. Other birds pick it up by mouth from litter, feed and water. Signs appear two to three days after infection, which is why a whole house seems to fall sick at once. The virus is not passed through the egg, and recovered birds do not stay carriers for long. The real carrier is the house: litter, dust, cracked floors, equipment, boots, crates, rats and the small black litter beetles that live under feeders all hold live virus between batches.
The first sign is often birds pecking at their own vents. Within hours the picture fills in:
Nearly every bird may look unwell for a few days. Deaths vary widely. A mild outbreak in partly protected broilers may take a few birds in every hundred. Classical strains in unprotected flocks can take two or three in ten, and the very virulent strains reported in West Africa can kill far more, especially in layer pullets.
Open four or five freshly dead birds, not one, and look for the combination below. No single sign proves the disease.
Your vet or the district veterinary office can confirm the diagnosis. Take birds that died within the last few hours, or live sick ones, and keep them cool on the journey. A carcass that has lain in the heat since morning tells nobody anything.
| Condition | What it shares with Gumboro | What points away from Gumboro |
|---|---|---|
| Coccidiosis | Same age group, ruffled birds, wet litter, soiled vents | Blood or orange mucus in droppings, damage inside the gut wall, bursa normal, losses build more gradually |
| Newcastle disease | Sudden illness and heavy deaths | Gasping, green droppings, twisted necks and paralysis, any age affected, deaths continue instead of stopping after a week |
| Mouldy feed (mycotoxins) | Bleeding in muscles, small bursa, poor immunity | Slow onset, poor growth over weeks, pale or yellow liver, problem follows a feed batch |
Two of these can run together. Gumboro often opens the door to coccidiosis in the same fortnight, and a flock weakened by Gumboro is easy prey for Newcastle disease.
When the deaths stop, many farmers think the problem has ended. For the survivors it has only changed form. With the bursa wrecked, the flock makes fewer antibodies, and the results show up over the following weeks:
The silent form, infection in the first two weeks, gives all of this without the warning of a death spike. If a farm has vaccine failures and minor illness batch after batch, ask your vet to look at the bursas of a few three-week-old birds. Small, shrunken bursas at that age are a strong clue.
Breeder hens are vaccinated against Gumboro so that they pass antibodies into the yolk. The chick absorbs these in its first days, and they guard it through the early part of brooding. This borrowed protection is not topped up. It falls by about half every three to five days, faster in quick-growing broilers than in layer chicks, and for most flocks it runs out somewhere in the second or third week.
Here is the puzzle. A live Gumboro vaccine is a weakened virus that must multiply in the bursa to teach the bird's own immune system. Give it while maternal antibody is still high and the antibody neutralises it. Wait until antibody is certainly gone and the field virus may get there first.
The puzzle gets harder because chicks in one box are not identical. Chicks from young and old breeder flocks start with different antibody levels, and a batch made up from several sources has a wide spread. Some chicks are ready for vaccine at day ten while their neighbours are not ready until day twenty.
That spread is the reason most farm programmes give two doses. The first catches the chicks whose antibody faded early. The second catches those that neutralised the first dose. Where a laboratory service is available, a vet can blood-test a sample of day-old chicks and calculate the best date for that batch. It is also why a whole batch from one hatch and one source is easier to protect than a flock built from several small purchases.
Some hatcheries vaccinate against Gumboro at day-old, by injection, using newer vaccines that are designed to get around maternal antibody. One kind carries a Gumboro gene inside a harmless Marek's-type vaccine virus. Another binds the vaccine virus to antibody so that it only becomes active once the chick's maternal protection has fallen. Where one of these has been given, farm doses in the drinking water may be unnecessary or may need to change.
Chicks from Halaal Farms Ghana are vaccinated at the hatchery before they leave. When you book your chicks, ask exactly what the batch has had and write it in your records, then show that note to your vet. The same question belongs on your list for any supplier of broiler chicks or layer chicks.
Live Gumboro vaccines for drinking water are grouped by strength: mild, intermediate and intermediate-plus (sometimes called hot). Stronger strains can break through higher levels of maternal antibody, which helps on farms with heavy field challenge, but they also cause some bursal damage of their own. Choosing the strain is a job for a vet who knows the disease pressure in your district.
As a typical example, many programmes in Ghana give a first dose in the second week of life and a second dose seven to ten days later, fitted around the Newcastle doses. Layer pullets, cockerels and dual-purpose birds follow the same pattern during brooding. Treat these timings as examples only. Our article on vaccination schedules for broilers and layers shows how the pieces fit together, and your local vet sets the final programme.
A correctly timed dose still fails if half the flock does not drink it. Heat, sunlight, chlorine and disinfectant residue in drinkers all kill the live vaccine. The full method is in our guide to giving poultry vaccines properly.
No drug kills the virus. The aim is to carry as many birds as possible through the five to seven bad days and to keep the virus out of other houses.
The Gumboro virus is one of the hardest poultry viruses to remove. It has no fatty outer coat for soap and mild disinfectants to dissolve, and it survives in an uncleaned house for four months or longer. Placing new chicks on old litter after an outbreak almost guarantees early infection. Do the full job:
Each step is explained in our article on cleaning and disinfecting a poultry house between batches. Earth floors cannot be disinfected properly. If Gumboro keeps returning on an earth floor, a concrete screed is likely to pay for itself.
The figures below are examples only. Use your own prices.
Take a flock of 500 broilers that loses 15 per cent, or 75 birds, at four weeks. Each dead bird took with it the price of the chick and roughly 2 kg of feed. If the chick cost GH₵ 20 and feed costs GH₵ 8 per kg (a 50 kg bag at GH₵ 400), each bird represents about GH₵ 36 already spent, before vaccines, charcoal and labour. Seventy-five birds make GH₵ 2,700 gone, plus the sale value you expected from them.
Then count the survivors. If the remaining 425 birds each eat an extra 200 g of feed to reach the same weight, that is another 85 kg, close to two bags. Put your own numbers through the poultry profit calculator with mortality at 5 per cent and again at 20 per cent, and the value of two properly given vaccine doses and a clean house becomes clear.
Vaccine cannot protect chicks that are swamped with virus in their first week, and cleaning alone cannot keep out a virus that travels on boots and crates. A farm that controls Gumboro usually does the following.
If you are preparing for a new batch after a Gumboro outbreak, or you are unsure how the hatchery vaccination fits with your farm programme, call Halaal Farms Ghana on 024 915 1503 or send the order form. We confirm the hatch date, price and delivery cost before you pay, and advice before and after your order is free.
Birds that recover from Gumboro are solidly immune to it and will not go through the disease again. The danger is to the next batch. The virus stays alive in litter, dust and cracks for months, so chicks placed in a poorly cleaned house meet it in their first days, before any vaccine has had time to work. The birds change but the house stays infected.
Yes. Broilers are at greatest risk between about three and six weeks, exactly when they are carrying the most feed cost. An outbreak in week four can kill a large share of the flock and leave the rest growing slowly with poor feed conversion. Protection from the hatchery, the farm programme or both should be in place well before the third week.
No. Gumboro is caused by a virus, and antibiotics do not act on viruses. Care is supportive: keep birds warm and well ventilated, keep clean water in front of them, and give vitamins and electrolytes if your vet advises. A vet may prescribe treatment for bacterial infections that follow the outbreak. Tell the vet before giving any drug, because sick kidneys cope badly with some medicines.
The usual reasons are timing and delivery. If the dose was given while maternal antibody was still high, the vaccine was neutralised. If the vaccine got warm, was mixed in chlorinated water or was not drunk by every bird, part of the flock stayed unprotected. A heavily contaminated house can also infect chicks before the vaccine has built immunity. Ask a vet to review the whole programme.
No. The Gumboro virus infects chickens and is not known to cause illness in people. Healthy birds from a flock that has recovered can be sold and eaten as normal once any medicine withdrawal period has passed. Sick and dead birds should never be sold or eaten, whatever the disease, and should be buried deep or burnt away from the poultry house.
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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