Gumboro disease In Poultry

Gumboro disease is a sudden and severe, highly contagious viral infection of young chickens. Next to

Ranikhet, it is the second most important disease of poultry, and every year inflicts heavy mortality. The disease is of great economic importance because, besides causing heavy mortality, it produces severe and prolonged suppression of the natural immune responses (immunosuppression). Immunosuppression, inturn, can lead to vaccination failures, Escherichia coli infection, and gangrenous dermatitis. The deaths resulting from these other diseases in many cases are greater than those from Gumboro disease itself. Gumboro disease occurs throughout the year, and usually affects young chickens between 18 to 40 days of age. Rarely, however, in layers, it may be seen even up to 14 weeks.

Cause

A virus - called birnavirus. The virus has two main serotypes: I and 2. Only serotype I produces disease.

It has several strains. Some strains are so mild that they do not produce disease, while others are so harmful that they cause up to 50% mortality. The viruses have an attraction for cells of bursa and cause depletion of this organ. Virus in the sick birds is excreted in faeces for 10-14 days. It is very stable and remains highly infectious in the poultry environment for many months.

Spread

The most common route of infection is by mouth. The virus being resistant to heat and disinfectants

continues to linger on at the farm, and poultry houses remain infective for up to 122 days after an outbreak.

Water, feed, and droppings in the infected sheds are infectious even after 52 days.

Symptoms

Symptoms vary, depending on the disease-producing power of the virus; and age and maternal antibody level of the chick.

I. Severe form is seen in chicks between 3 and 6 weeks of age (between 21 and 42 days). One of the

earliest symptoms is the tendency for some birds to pick at their own vents. Other symptoms include

depression, white watery diarrhea, soiled vents, loss of appetite, ruffled feathers, unwillingness to move, trembling, closed eyes (Fig. 9), lying down in exhaustion, and finally death. The number of birds affected may vary from 10 to 100%, and mortality from 0 to 20%, sometimes reaching 50%. Strains of the most severe type of Gumboro virus cause 90 to 100% mortality.

2. Mild form may not show any symptoms except poor growth.

3. The course of the disease in individual chicks is short (5-7 days), leading rapidly to death or recovery.

Postmortem Findings

I. Swollen (oedematous) bursa in the early stages that may be double in size and weight by the 4 th

day .

2. The bursa first shows cheesy mass within its lumen, and later on small and large haemorrhages on its

inner surface. Sometimes widespread haemorrhages are present throughout the bursa . This is typical of Gumboro disease.

3. Kidneys are swollen and slightly pale in appearance .

4. Haemorrhages in the thigh and breast muscles. This again is typical of Gumboro

disease.

Diagnosis

I. From the characteristic postmortem findings. Changes in the bursa are quite characteristic and confirm the diagnosis.

2. Confirmation of the diagnosis can be made by ELISA and isolation of the virus.

Treatment

No treatment is available for Gumboro disease.

Control

I . Vaccination of parent breeders and/or young chicks is the best method of control.

2. Hygiene and sanitary precautions that are applied to prevent the spread of most poultry infections must also be strictly followed in the case of Gumboro disease.