General information
Avian Paramyxoviruses (APMV) are a group of RNA viruses that cause acute respiratory or neurologic disease. There are 12 recognized serotypes of avian paramyxoviruses (APMV-1 to APMV-12). In wildlife, avian paramyxovirus is most typically seen in cormorants and gulls. A variant of APMV-1 found in pigeons and doves is referred to as Pigeon Paramyxovirus (PPMV-1).
Clinical signs depend on which strain has infected which species. Birds may die acutely or have prolonged disease. Typical signs may include: weight loss, sneezing, nasal discharge, labored breathing, yellow-green diarrhea, stumbling, and head bobbing. In prolonged cases, wing and leg paralysis, jerky movements, and dilated pupils also may be seen. Lesions seem to affect the liver, spleen, and respiratory system the most.
Transmission occurs primarily from direct contact with feces, respiratory secretions or through a contaminated environment. Poultry populations are especially susceptible to infections when in close contact with other birds commonly infected like cormorants, pigeons, and imported psittacine species. Avian paramyxovirus can be diagnosed by isolating virus from swabs (oropharyngeal and/or cloacal), serology or PCR testing. There is no treatment for APMV infection, only supportive care. Zoonoses Some strains can potentially cause a temporary conjunctivitis and flu-like symptoms in people. However, this is mostly limited to lab workers and vaccination teams that are exposed to very large quantities of the virus.
There are 12 recognized serotypes of avian paramyxoviruses (APMV-1 to APMV-12), all singlestranded RNA viruses. The most common wildlife species affected by avian paramyxoviruses are cormorants and pigeons, and species-adapted APMV1 strains routinely circulate in those populations. APMV-2 has been isolated from wild birds, mainly passerines, and caged psittacine species. A virulent strain of APMV-1 is sometimes seen in cormorant populations and leads to periodic outbreaks of severe illness and deaths in young birds. In domestic poultry, infection with virulent APMV-1 is called Newcastle Disease, a reportable disease.
Transmission: Avian paramyxoviruses can spread in multiple ways: through exhaled air, respiratory discharges, excrement, and sometimes even through eggs laid by infected birds. Virus is shed during almost every stage of infection, including when an individual is recovering. In addition, the virus can survive for months in the environment and has a wide tolerance range for both pH and temperature; this makes it very easy for wild birds to become infected even without the immediate presence of an infected individual.
Poultry populations are especially susceptible when in close contact with wild birds commonly infected, such as cormorants, pigeons, and imported psittacine species. Species-adapted APMV-1 strains do not always affect poultry, although more virulent strains can cause outbreaks of severe disease with economic impacts. For APMV-2, infections in poultry are also thought to originate through contact with wild birds, but the mechanics of transmission between wild and domestic birds are unclear.
Clinical Signs: Infections can range from being rapidly fatal to absolutely harmless. The severity of the infection depends on virus strain and the species, age, and immune status of the potential host. In cormorants, clinical signs of virulent APVM-1 infection are usually limited to juvenile birds and may end in death. Affected birds show neurological signs including weakness, partial or complete paralysis of wings or legs, incoordination, and tremors. In pigeons, infection with PPMV-1 causes neurologic signs and a high mortality rate. Clinical signs in psittacines include inflammation of the trachea and intestines, as well as pneumonia. In domestic poultry, clinical signs of APMV-1 infection range from asymptomatic to severe, depending on the virulence of the virus strain involved. Infection typically results in respiratory illness, but diarrhea, nervous system signs, and depression are also common clinical signs. Some birds may not appear to be sick but die suddenly.
Treatment: For avian paramyxovirus infection, treatment is supportive care. If suspected, infection with a virulent strain of APMV-1 must be reported to appropriate federal and state authorities. Vaccination of domestic poultry is an option to lessen the severity of infection, but it does not grant complete immunity.
Diagnosis: Avian paramyxovirus can be formally diagnosed by isolating virus or DNA from swabs (oropharyngeal and/or cloacal) and serology coupled with identifying clinical signs. Strain identification is confirmed by PCR. Reference laboratories use sequence analyses to detect genetic differences for comparison of strains from different outbreaks and to identify the source of those infections.
Precautions and Prevention: As many outbreaks of APMV in poultry originate from contact with wild birds, bird-proofing poultry houses and using good biosecurity practices is critical in prevention. Vaccines are used for chickens, turkeys, and pigeons in other parts of the world, but are prohibited in birds entering the USA as it does not prevent individuals from carrying APMV-1 and hampers detection of infection during outbreaks. Some strains of APMV-1 can infect people, causing a temporary conjunctivitis. There is no risk of zoonosis for APMV-2 – APMV-12.