Key Points on the Differential Diagnosis, Prevention and Control of Newcastle Disease and Avian Influenza in Chickens

Newcastle disease and avian influenza in chickens are both highly contagious diseases caused by viruses. They can occur in all four seasons, and both are more common in winter and spring. In @#@230@#@ production, both diseases occur frequently, and the losses they cause are very serious. The vast majority of farmers attach great importance to this and have intensified various prevention and control efforts, but they are not very clear about the differences between these two diseases. The following is a comparison of Newcastle disease and avian influenza in chickens from several aspects including pathogens, clinical symptoms, and pathological changes.

Pathogens

Fowl plague and avian influenza must be clearly distinguished...

Newcastle disease in chickens:

It is caused by a virus of the genus Respirovirus (mumps virus genus) in the family Paramyxoviridae. It can infect chickens of all ages, with chicks being the most susceptible. Clinically, it mostly presents as a mixed-type or atypical onset.

Avian influenza in chickens:

It is caused by Asian type A influenza virus of the family Orthomyxoviridae. It is characterized by rapid spread and long duration, and it has a certain cross-infectivity for poultry, among which chickens, ducks, geese and other poultry are the most susceptible.

Clinical symptoms

Newcastle disease in chickens: Typical Newcastle disease is mainly peracute and acute. In the early stage of illness, body temperature rises, the bird is depressed, has poor appetite, the comb and wattles turn purple, and large amounts of mucus frequently flow from the tip of the beak. When the bird is held upside down, large amounts of grayish-white mucus with a sour and foul odor can flow out of the crop. Breathing difficulty may produce a cackling wheeze or wet rales. There is diarrhea, with green, yellow-green, or yellowish-white thin droppings; the subacute and chronic forms mainly show neurological symptoms such as wing paralysis, lameness, twisted neck, and incoordination; atypical Newcastle disease mostly occurs in vaccinated flocks, and clinically it is characterized by mild respiratory symptoms, decreased egg production rate, faded eggshell color, mildly deformed eggs, high morbidity, low mortality, and diarrhea.

Avian influenza in chickens: Highly pathogenic avian influenza may show elevated body temperature, difficulty breathing, listlessness, complete loss of appetite, purple-black combs and wattles that become thickened and hardened with occasional necrotic nodules, swollen head, tearing, diarrhea with yellow-green thin droppings, and purple or dark red hemorrhagic spots visible on the unfeathered parts of the legs and on the foot scales. In adult laying hens, the egg production rate drops sharply, and most chickens die from paralysis and exhaustion. Low pathogenic avian influenza mainly shows difficulty breathing, decreased egg production rate, and other mild changes.

Pathological changes

Newcastle disease in chickens:

There are hemorrhagic spots and patches on the mucosa of the proventriculus, on the papillae, and between the papillae; in atypical cases, faint hemorrhage may be seen, and the mucus is turbid; the intestinal tract is congested and hemorrhagic, especially in the ascending part of the duodenum, around the vitelline stalk, and at the ileocecal junction, where hemorrhage is relatively obvious and concentrated; on the small intestinal mucosa there are round or date-pit-shaped necrotic ulcer foci; the rectum and cloaca both show congestion and hemorrhage, appearing as spot-like or brush-like lesions, and the cecal tonsils are red, swollen, and ulcerated.

Avian influenza in chickens:

The edges of the pancreas are congested and hemorrhagic, with grayish-white or yellowish-white necrotic foci; the lesions in the digestive tract are similar to those of Newcastle disease, but the difference is that the proventricular papillae are enlarged and show suppurative hemorrhage, and no ulcer foci are seen in the duodenum or cecal tonsils; in adult laying hens, white or pale yellow purulent exudate or tofu-dreg-like caseous material can be seen in the oviduct, along with yolk-like exudate and other lesions in the abdominal cavity.

For other pathological changes in tissues and organs, there is no obvious clinical significance for the diagnosis and differentiation of Newcastle disease and avian influenza in chickens.

Prevention and control measures

1. Prevent pathogens from invading the flock, cut off all possible routes of transmission, strengthen feeding management and routine hygiene work, and strictly implement disinfection systems.

2. Rationally formulate scientific immunization programs, carry out vaccination work well, and regularly perform antibody testing so as to strengthen immunity from time to time. Newcastle disease vaccine and avian influenza vaccine should be reasonably combined in use, and attenuated vaccines and virulent vaccines should be used in a coordinated manner to enhance the body's antibody levels and improve immunity.

3. Once a suspected epidemic disease is found, timely diagnosis should be made and the handling of dead chickens should be done well. Emergency prevention should be carried out for threatened flocks, and active treatment should be given to affected flocks to prevent the spread of the epidemic and secondary infection.

4. Highly pathogenic avian influenza must be handled strictly in accordance with relevant national disease prevention regulations. For mild avian influenza and Newcastle disease, the following methods can be used for treatment:

Vaccination:

Newcastle disease: If the whole-flock mortality rate is below 10%, the entire flock can be urgently immunized by drinking water with attenuated vaccines such as strain IV and clone-30 at 5-7 times the dose, or the whole flock can be urgently vaccinated with strain I at 2 times the dose; otherwise, drugs should first be used to control deaths.

Mild avian influenza: Use H9 and H5 avian influenza vaccines to urgently immunize flocks in surrounding areas that have not yet been infected.