Task 12 Read the text using your dictionary. Give Russian equivalents to the following words and phrases.

Avian influenza; high morbidity/mortality rate; charac­teristic lesions; subcutaneous haemorrhages; oedema; prov- entriculus; susceptible to something; the causative agent; mechanical means of transfer of infection; the onset of signs; field outbreaks; inappetence; suffocation; blood-tingled mu­cus; the acute phase; excitation.

AVIAN INFLUENZA

Avian influenza (Fowl Plague) in chickens is character­ised by a high morbidity and mortality rate with respiratory and nervous signs. The characteristic lesions include subcu­taneous haemorrhages, cyanosis of the head region, oedema of various parts of the body, and haemorrhages in the pro- ventriculus.

Incidence. Avian influenza virus, associated with highly fatal disease, has been isolated in a number of countries. Less pathogenic types are frequently associated with respiratory disease in turkeys. Infection is probably widespread in wild bird populations.

Susceptibility. Influenza virus naturally infects ducks, however, chickens, turkeys, geese, quail, and a wide variety of wild birds are susceptible to the infection.

Cause. The causative agent is a virus which belongs to the influenza group of viruses. There are a number of sero­types isolated from avian species which differ widely in their pathogenicity. The virus is readily destroyed in the poultry environment.

Transmission.

1. Contact spread readily occurs among pen mates.

2. Aerosol spread of the virus has been reported to occur between flocks.

3. The possibility of vertical transmission should always be considered, especially with less pathogenic types.

4. Mechanical means of transfer of infection include peo­ple, equipment, and artificial insemination.

Clinical signs. In susceptible chickens following an incu­bation period of 2-4 days the signs of the disease may appear suddenly. The course of the disease is usually short and the virus spreads rapidly within a flock.

Following the onset of signs, birds may only live a few hours. In field outbreaks morbidity may be 100 per cent and mortality may vary from 50 per cent to 100 per cent. The flock is generally depressed. Individual birds have ruffled feathers, inappetence and drop in egg production. The eye­lids may be closed and the conjunctiva is red and swollen. Characteristically oedema and cyanosis develop around the head region involving the comb, wattles and the area sur­rounding the eyes. The oedema may extend down the neck and breast. Oedema of the glottis may occur causing diffi­culty in breathing resulting in suffocation.

When respiratory signs are present a grey to blood-tinged

mucus exudes from the nostrils. There may be haemorrhag­es in the mouth. In most outbreaks varying degrees of di­arrhea may be observed.

Affected birds usually die within 2 days of the onset of signs. Birds surviving the acute phase of the disease deve­lop nervous signs including excitation, convulsions, or cir­cling movements and ataxia.

Task 13. Read the text and do the assignments that follow it.

THE PREVENTION OF DISEASE

There is no factor that will prevent disease coming on to or spreading within a farm.

Disease usually occurs because a number of factors are working against the animal, for example the weather, its nutrition or the number of stock in one building. All live­stock units should formulate a comprehensive policy to pre­vent disease.

All new stock should be inspected to ensure they are healthy. Some general signs of health are applicable to most animals: bright alert eyes, clean tail, groomed coat, even breathing, no sign of discharge from the nose, no coughing and healthy appetite. All new stock must be vaccinated against any known on-farm diseases.

The environment in which the animal lives probably has the greatest influence on the continuing good health of the animal. The more intensive the livestock system, the more attention must be paid to hygiene.

The animal’s own dung is a constant source of infection, so one of the animal’s major requirements is a clean lying area. Many livestock buildings and pens require regular clean­ing and disinfection.

The spread of and the severity of a disease can be reduced by the use of drugs. The best examples of these are antibiot­ics, insecticides and wormers.

Regular visits from the veterinary surgeon can go a long way in preventing disease. Regular visits every three or four months, when the veterinary surgeon and the stockperson can get together to look at and talk about the health of the unit, can help build up a health profile of the farm. This information can be useful when trying to identify or locate the cause of a problem.

Task 14. Answer the questions:

1) Why is it important to work out a comprehensive pro gramme to prevent disease?

2) What are some general signs of healthy animals?

3) Why is hygiene so important in intensive livestock systems?

4) Is it necessary to use drugs to prevent diseases?

5) How often should the veterinary surgeon visit the farm?