Harm of Duck Influenza and its Comprehensive Control

Duck influenza is a highly lethal infectious disease caused by influenza A virus, which can infect ducks of all breeds and ages. It is the most serious disease that harms@#@231@#@industry today.

1. epidemic characteristics

In the past, it was generally believed that waterfowl were only carriers of influenza virus and did not develop disease. However, since the mid-1990s, the fact that ducks were infected with highly pathogenic influenza virus and died broke people's traditional understanding of duck influenza. Ducks are not only highly susceptible to influenza, but also can transmit horizontally to terrestrial birds and become the source of influenza infection. This is a trend that should be highly valued at present.

Sick birds, sick birds, seemingly healthy birds with virus are the source of infection of the disease. The disease can be transmitted vertically and horizontally (through contaminated water, air, birds, duck vendors, etc.). All kinds of ducks can be infected, but muscovy duck is the most common disease. The infection occurred in ducks of all ages, but clinically it was more common in ducks over 20 days old. The morbidity and mortality of infected ducks were related to duck breed, age, virus subtype (virulence) and whether there were complications or secondary diseases. The morbidity of ducklings was as high as 100%, and the mortality was 30%~95%. Infected ducks died within 1~3 days after symptoms appeared. The incidence and virus rate of breeding duck and laying duck were relatively low, mainly manifested as abnormal laying.

The disease occurs all year round, but the incidence is more from November to April or May of the following year. The duck flocks with this disease are prone to concurrent or secondary duck infectious serositis, duck colibacillosis, duck paratyphoid fever, duck cholera and duck coccidiosis. The virus rate of ducks with concurrent or secondary diseases increased significantly.

Meat ducks, laying ducks and breeding ducks raised in different ways (ground or net, captive or stocking, single breeding or mixed breeding of chickens and ducks) all had disease and death, but the incidence and mortality were different. Regular monitoring of avian influenza virus distribution in ducks and other waterfowl and their environment (water) is of great significance to prevent and control the occurrence and epidemic of avian influenza.

2. clinical symptoms

In meat ducks, sick ducks show severe mental exhaustion, eyes closed and crouching; various neurological symptoms (neck twisting in "S" shape, head touching ground, upside down, lateral lying, rampage, ataxia, etc.); swollen head; tears, wet eye circles, red eyes; breathing difficulties (mouth breathing or panting); acute death of sick ducks can be seen in cyanosis or bleeding of upper beak and foot webs; diarrhea (white or green loose feces). Disease ducks infected with moderate virulence influenza virus or partially immunized ducks appeared body weight, growth retardation and other phenomena.

15%~90% of laying ducks or breeding ducks infected with the disease did not lay eggs, resulting in a sharp decline in egg laying rate (such as from 95% to about 10% or stop production), abnormal egg laying (soft shell eggs, thick shell eggs, thin shell eggs, no shell eggs, abnormal eggs, etc.), no egg laying peak or continuous low egg laying rate, low mortality (daily mortality rate 0.1%~3% or no death).

3. autopsy lesion

In meat ducks, the main manifestations of dead ducks were a large number of cheese-like substances or hemorrhage in respiratory tract (trachea and bronchus), pulmonary hemorrhage or congestion; pancreatic hemorrhage, a large number of white necrosis spots (or necrosis spots) with large needle points on the surface, or hyaline (or liquefied) necrosis spots and necrosis foci; coronary fat, myocardial hemorrhage, white striated necrosis of myocardium, pericarditis, pericardial effusion; focal ulcer of glandular stomach mucosa; Intestinal tract (duodenum, jejunum, rectum, etc.) mucosa bleeding or bleeding ring, intestinal wall fat bleeding. In addition, meningeal hemorrhage, focal necrosis of brain tissue, and enlarged hemorrhage or congestion of liver, spleen and kidney can also be seen. Duck infected with influenza virus of moderate virulence or partially immune duck, chest muscle, leg muscle obviously hypoplasia, sternum soft.

In addition to the pathological changes of meat ducks, the egg ducks or breeding ducks suffering from this disease also showed severe congestion and hemorrhage of follicular membrane, hemorrhage and edema of oviduct mucosa with bean curd dregs like clot, and even the follicles of individual sick (dead) ducks ruptured in abdominal cavity.

4. diagnosis

The initial diagnosis can be made according to the characteristic clinical symptoms and pathological changes of autopsy.

The differential diagnosis of the disease in ducklings should be distinguished from duck viral hepatitis, which is characterized by enlarged liver, punctate or ecchymosis bleeding on the surface and enlarged kidneys, and in muscovy ducklings, the disease is easily confused with "three-week disease", which usually has no neurological symptoms and characteristic lesions in myocardium and pancreas of influenza infected (dead) ducks. For meat duck influenza cases with three kinds of inflammation (pericarditis, perihepatic inflammation, air sac inflammation) and influenza lesions, it should be distinguished from single duck infectious serositis and duck colibacillosis. In breeding ducks, laying ducks, due to the occurrence of influenza after the occurrence of complications or secondary colibacillosis, so in clinical diagnosis should also pay attention to a single colibacillosis to distinguish.

5. control methods

The key is to control the introduction of this disease, we should do a good job in the quarantine of imported breeding ducks and breeding eggs, adhere to the all-in and all-out feeding mode, strengthen disinfection at ordinary times, and do a good job in immunity to common diseases in order to improve duck resistance.

Inactivated duck influenza vaccine has a good immune protection, vaccination with it is the main measure to prevent the disease, but should be selected with the local epidemic duck influenza virus serotype of the same inactivated vaccine for immunization.

Once duck influenza caused by highly pathogenic strains is found, it should be reported and extinguished in time. For duck influenza caused by moderate or low virulence strains, some antiviral drugs and broad-spectrum antibiotics are available to reduce mortality and control secondary infections.