Gumboro disease: the disease that disarms the defences

Recognising Gumboro disease

• Age: 3 to 6 weeks most often.
• Sudden onset: birds prostrate, feathers ruffled, trembling, sitting on their hocks, beak on the ground.
• Whitish diarrhoea, watery; the birds peck at their vent (the rump area is soiled).
• Bell-shaped mortality: it rises over 2 to 3 days, peaks around the 3rd or 4th day, then falls back within a week. Often 5 to 20% losses, sometimes much more with certain strains.
• At the post-mortem, the veterinarian finds the bursa of Fabricius (a small organ near the vent) swollen, sometimes haemorrhagic, then shrunken.

This bursa is the organ that makes the young bird's defences. Once destroyed by the virus, it no longer makes them: the survivors are immunosuppressed, respond poorly to later vaccines and fall to every infection (coccidiosis, respiratory diseases, Newcastle disease).

A very resistant virus

The Gumboro virus survives for months in a house, the litter, the dust, the equipment, and resists many common disinfectants. That is why a farm that has had Gumboro disease sees it again flock after flock if the cleaning stays superficial. After an outbreak: complete cleaning, a disinfectant effective against non-enveloped viruses (the veterinarian or the product seller will tell you which), a long sanitary break (at least 3 to 4 weeks), litter taken far away, cages and boots treated.

Vaccination: it is all in the date

Chicks receive antibodies from their mother that protect them in the first days… and that also neutralise the vaccine if it is given too early. Given too late, the virus arrives before the vaccine. The right date depends on the flock's antibody level and on the disease pressure in the area: it is the veterinarian who sets it (often a first dose at around 10 to 14 days and a booster at around 18 to 24 days, but this varies). The drinking-water rules seen in lesson 1 (no chlorine, skimmed milk, water drunk within 1 to 2 hours) apply exactly.

Reminder: there is no vaccine at the hatchery for broilers; Gumboro disease is vaccinated against on the farm.

When it happens

• Call the veterinarian: they confirm (post-mortem) and decide; there is no treatment for the virus, only support (water, electrolytes, vitamins) and sometimes an antibiotic against secondary infections, on prescription.
• Isolate, do not sell, dispose of carcasses properly.
• Protect the neighbouring houses: separate boots, clothing and equipment; review their vaccine dates with the veterinarian.
• Prepare the long sanitary break and the appropriate disinfection.