The course of infectious diseases in the subclinical, latent and associated forms complicates their diagnosis and prevention. Particular attention deserves infectious diseases associated with the defeat of the respiratory tract, in which by airborne transmission there is a rapid spread of infection among a considerable number of poultry, regardless of the system of retention. This group should include the metapneumoviral infection (MPVI) of the poultry, which is characterized by inflammatory processes of the upper respiratory tract.
MPVI is difficult to diagnose. This is due to the diversity of strains of the virus, the characteristics of the pathogen, and the fact that this infection often occurs in an associated form with other viral or bacterial infections.
Epidemiological monitoring of viral and bacterial diseases was carried out during 2016–2018 in breeding private poultry farms of the Kharkiv region, where bird against viral infection was not spilled. The research was carried out among the turkeys, chicks and geese using the ELISA method, the diagnostic kit IDEXX (USA), erythrocytic diagnostic kit for IHA (developed by NA in 2012 for the diagnosis of MPVI of the bird) and the molecular genetic method (PCR).
In 2017, serological tests blood serum samples from turkeys and chickens revealed 90–100% of positively responsive to MPV with antibody titres, respectively, from 2843 to 21580 and from 1380 to 7350 (ELISA), ARVI — from 1278 to 7430 and mycoplasmosis — from 1757 to 21769. With the help of an erythrocytic diagnostic, positive titres of antibodies to metapneumatic and retroviral infections in the turkeys and geese, ranging from 1:8 (3 log) to 1:128 (7 log), were detected in IHA.
Thus, according to the results of serological studies, the titres of antibodies detected were similar to those of using the IHA and the ELISA method, and the obtained indices testify to the circulation of field metapneumaurous in the farm among turkeys and geese.
Bacteriological studies from the blood of the lungs and the heart of the bird isolate the pathogenic serotypes of E. coli, staphylococci, streptococcus not sensitive to gentamicin, enrofloxacin, ciprofloxacin, fluorophenicol and P. aeruginosa — sensitive to henthamycin, fluorophenicol, chloramphenicol.
The associated course of viral and bacterial infections and the pathognomonic nature of their signs makes it difficult to diagnose due to the lack of test systems that would be available to veterinary medicine laboratories, which led to the need to develop a domestic ELISA-method for controlling MPVI. On the basis of purified high-level antigen PVT-09/B, the components of the kit were obtained and an ELISA-test system was developed for the detection of antibodies to the metapneumovirusis in blood serum of chickens and turkeys in the testing of samples in one dilution. The optimal concentrations and conditions of interaction of the components of the reaction are determined. The thresholds that distinguish specific and nonspecific reactions are established, the linear regression equation for determining the antibody titer in blood serum of a patient suspected of poultry disease or persistent infection is proposed.
The test-system was commissioned laboratory and production tests at the State Research Station of Poultry of the National Academy of Agrarian Sciences (Kharkiv), Kharkiv Branch of the State Research Institute for Laboratory Diagnostics and Veterinary and Sanitary Expertise.
It was established that the diagnostic library on the basis of ELISA is active and specific and can be used for epizootic monitoring and control of immunity tension with regard to the MPVI of chickens and turkeys. The high sensitivity of the test system makes it possible to use it in laboratory practice.
