Specialists of the Rostov reference center of Rosselkhoznadzor talk about metapneumovirus infection

Metapneumovirus infection (MPVI, "swollen head syndrome" of broilers, rhinotracheitis of turkeys) is a highly contagious viral disease of turkeys and chickens, characterized by inflammation of the upper respiratory tract, sero-catarrhal inflammation of the conjunctiva, eyelids, serous edema of the subcutaneous tissue in the upper part of the head. 

The infection can also reproduce in the genital tract, which leads to a decrease in the egg production of the bird and a deterioration in the quality of the eggs. Currently, metapneumovirus infection is registered in all countries of the world with developed poultry farming, both in turkeys and chickens of all ages. It is noted that metapneumovirus infection in chickens is more severe than in adult chickens. Morbidity can reach 100%, mortality - 4-90%. The economic damage from MPVI is due to increased culling of substandard birds, a decrease in live weight gain and a decrease in egg productivity.

The causative agent of the disease is an RNA-containing virus - Avian metapneumovirus (AMPV), belonging to the species Pneumovirus. There are 4 subtypes of the virus: A, B, C and D. In the Russian Federation, from 1995 to 2014, the MPV genome of birds of subtype A and subtype B was detected. concomitant factors (poor housing conditions (ventilation), high stocking density, elevated ammonia levels, secondary infections).

The main routes of infection are aerogenic and alimentary. After entering the body, the virus multiplies in the ciliated cells of the epithelium of the upper respiratory tract, destroys them and penetrates into the blood. With the blood stream, the virus enters the reproductive tract, the defeat of which leads to a decrease in egg production and egg quality.

In an acute course, chickens show lethargy, poor feed intake, leakage from the eyes and nasal openings, soft tissue edema in the periorbital and infraorbital sinuses, neck curvature, disorientation and depression, and purulent otitis media. In subacute and chronic course, the periorbital space, eyelids and lacrimal glands are involved in the inflammatory process. Chickens hide their heads under their wings, try to scratch their eyes with their paws and claws, as a result of which purulent conjunctivitis and blindness develop.

In laying hens, greenish-brown diarrhea is observed, as well as nervous phenomena, manifested by a shaky gait. There is profuse lacrimation, sneezing, shaking the head, coughing and swelling around the eyes. Egg production decreases, hens lay deformed eggs.

Pathological and anatomical changes are not characteristic and are due to the action of secondary microflora. Reveal signs of rhinitis, tracheitis, sinusitis. In the tissues of the swollen head, the presence of serous, purulent or fibrinous exudate, congestion in the lungs. Serous inflammation of the anterior larynx - when the larynx is cut in its anterior part, a red border is detected, exudate may not be detected. This sign can be considered the most pathognomonic, since other pathological changes may not be expressed against the background of permanent vaccination of birds.

The disease is diagnosed on the basis of epizootological data, clinical and pathological morphological signs and laboratory results - isolation and identification of the virus using PCR.

Metapneumovirus infection is differentiated from other diseases occurring with respiratory syndrome alone or in association with metapneumovirus infection: influenza; Newcastle disease; infectious bronchitis; infectious laryngotracheitis; smallpox; pasteurellosis; colisepticemia; hemophilia; respiratory mycoplasmosis; chlamydia; aspergillosis; hypovitaminosis A; ornitobacteriosis; turkey bordetellosis.

The most effective way to prevent MPVI is to carry out mass vaccination, subject to the requirements of the biological safety of the farm.