A minor study on avian metapneumovirus

Abstract: Avian metapneumovirus (aMPV) is an important pathogen that causes respiratory diseases and reproductive failure in various avian species. The disease was first reported in South Africa in the late 1970s. Later, the disease has been reported from all countries around the world, except for Australia, and has caused economic losses in poultry industry worldwide due to the transient drop in eggs and meat production. In 1998 there was an outbreak in Sweden but due to good biosecurity and effective vaccine control program the disease has been under control since then. In South America the industry of egg-laying hens struggles with many respiratory diseases, such as aMPV, Infectious bronchitis, Laryngotracheitis and Newcastle disease. This study is a field project on the Avian metapnuemovirus and took place in the state of São Paulo, Brazil. The study contributed to a bigger research project at the University of Sao Paulo under the department of Preventive Veterinary and Animal Health where the veterinarians are trying to control the problems with respiratory diseases in Brazilian poultry production. The scope of this study was to detect aMPV in egg-laying hens with respiratory disease and reproductive failure and further sequence the viral RNA and compare it to previously found viral strains. This information is important to obtain accurate vaccination-programs for control of the virus. Organ-samples and blood-samples were collected from five different farms in Bastos, a town in the state of São Paulo with extensive egg-production. Reverse transcriptase PCR was performed to detect RNA of aMPV in the organs of the sampled birds. One out of 66 pools of samples was positive. The sequencing of the RNA was unsuccessful and no phylogenetic tree comparing this strain to other known viral strains of aMPV could be designed. The blood-samples were tested with two types of ELISAs, one indirect ELISA and one blocking ELISA, for antibodies against aMPV. Antibodies could be detected in 85 % of the birds with the SVANOVIR-kit; and in 87 % of the birds using the IDEXX-kit. A majority of the birds had antibody-titers corresponding to previous infection. At the farm where the PCR-positive sample was collected, the birds had not seroconverted in spite of reported vaccination against aMPV one month earlier. The result of this study is consistent with previous conclusions from other studies; that RNA of aMPV is difficult to detect and that vaccine prevention of the disease is sometimes unsuccessful.