The Pathogenesis and Prevention and Control Methods of Wild Duck Influenza

The wild duck is a typical representative of waterfowl; the wild duck is the common name for the mallard in the Northern Hemisphere. The wild duck belongs to the class Aves, order Anseriformes, family Anatidae; its numbers are very large, and it is a general name for many kinds of wild ducks, with more than ten species. It is not afraid of heat or cold, and can live normally at -25 to 40°C, so the suitable breeding range is very broad. It has strong disease resistance, few diseases occur, and the survival rate is high, which is even more conducive to intensive raising.

Influenza is a very common disease of wild ducks. If prevention is poor, it will bring huge losses to wild duck farmers, so what exactly is wild duck influenza? How is it prevented and controlled? Below is an introduction for everyone.

Pathogenesis of wild duck influenza:

Wild duck influenza was originally named true fowl plague, also called European fowl plague, or avian influenza for short, and is an infectious syndrome of poultry caused by type A influenza virus.

(Pathogen) The pathogen is avian influenza virus, which in classification belongs to the family Orthomyxoviridae and the genus Influenzavirus A, type A influenza virus. Because of the different combinations of the two glycoproteins hemagglutinin and neuraminidase, type A influenza virus can be divided into many different subtypes, and there is no cross-immunity among the subtypes.

(Epidemiological characteristics) Influenza viruses can be divided by experimental typing into 3 kinds: non-pathogenic, low-pathogenic and highly pathogenic. At present, the main strains causing disease in waterfowl are highly pathogenic strains, whose pathogenicity is very strong, and both the incidence rate and mortality rate are high. Influenza virus exists in the nasal secretions and feces of poultry, and because it is protected by organic matter, the virus has extremely strong resistance.

(Clinical features) The incubation period is from several hours to several days, and the longest can reach 21 days. Sick poultry suddenly become ill, body temperature rises, appetite decreases or is completely lost, the head is drawn in, the spirit is listless, feathers are dull and disordered, and they doze. Some waterfowl show nervous symptoms. The feces are loose, yellow-white or yellow-green. In most sick poultry the ocular conjunctiva is congested, flushed or bleeding, and in severe cases the nasal cavity also bleeds. Some develop corneal opacity and blindness; some have swelling of the head and face, and edema of the lower jaw. After laying ducks are infected, the egg production rate drops sharply, or even stops completely; even if eggs are laid, the eggs become smaller, egg weight decreases, and some deformed eggs appear. Before death, most waterfowl show cyanosis at the tip of the beak and on the webs of the feet, and in some, bleeding under the scales of the feet can be seen.

(Necropsy features) Dead waterfowl show cyanosis at the tip of the beak, and in some the head and face are also cyanotic. Some waterfowl have swelling of the head and face, bleeding under the head, and gelatinous edema; in severe cases gelatinous edema can also appear in the lower jaw, and the ocular conjunctiva and nasal mucosa are congested, bleeding and edematous. In some, the tracheal mucosa and the subcutaneous fat throughout the body bleed. The liver is enlarged, with scattered hemorrhagic spots and necrotic foci. In those with a slightly longer course, the liver texture becomes hard. The gallbladder is distended and enlarged. The spleen is enlarged and congested, with scattered necrotic spots. The myocardium is degenerated and necrotic, and the fat at the coronary groove of the heart and the pericardium bleed. There are hemorrhagic spots under the mucosa of the proventriculus and under the keratinous membrane of the gizzard, and in some a hemorrhagic band also forms at the junction of the proventriculus and esophagus. The small intestinal mucosa is often congested and bleeding, and in some the mucosa of the entire intestinal tract is diffusely congested and bleeding. The pancreas is enlarged, bleeding and necrotic. The kidneys are enlarged with surface bleeding. In dead waterfowl with nervous symptoms, the cerebral blood vessels are congested, and in some brain tissue large areas of gray-yellow necrosis appear. In young waterfowl, enlargement and bleeding of the bursa of Fabricius can be seen. In laying waterfowl, the cloacal mucosa is congested, bleeding and edematous; eggs are deformed and degenerated; follicles are congested and bleeding, and some follicles appear like purple grapes.

(Diagnostic features) Based on the clinical symptoms and necropsy lesions of affected wild ducks, combined with the epidemiological characteristics of acute onset, rapid spread, short course and high mortality, a preliminary diagnosis can be made.

Prevention and control measures for wild duck influenza:

Strengthen quarantine to strictly prevent the introduction of highly pathogenic avian influenza virus.

Strengthen feeding management, pay attention to environmental hygiene, improve the body's resistance, and avoid contact with wild waterfowl when grazing wild ducks.

For healthy wild ducks, vaccination with inactivated highly pathogenic avian influenza vaccine should be carried out. The first immunization is at 7 to 10 days of age, with 0.5 milliliter injected intramuscularly per bird; repeat once after 3 months, with 1 milliliter injected intramuscularly per bird.