Avian paramyxoviruses types 2–22 are predominantly harbored in wild bird populations. Infections of poultry with these viruses are mostly inapparent. Occasionally, types 2, 3, 6, and 7 have caused mild disease in chickens, turkeys, and ostriches.
While avian paramyxovirus type 1 (APMV-1) infections have substantial impact on poultry, infections with other APMV types have been reported mainly from wild birds. Occasionally, some of these viruses have been isolated from poultry with respiratory disease or decreases in egg production. The animal health and economic significance of these viruses is considered low, and it is not fully elucidated whether isolations from sick poultry are incidental findings or these infections have contributed to the disease.
Specialized and reference laboratories can identify and subtype the viruses. Vaccines against APMV-3 exist in Europe and the US.
Etiology and Epidemiology of Other Avian Paramyxovirus Infections
Advances in genome sequencing and enhanced surveillance programs have resulted in identification of 13 previously unreported avian paramyxovirus types since the year 2000. There are 22 recognized types of avian paramyxoviruses (APMV-1 to APMV-22). Newcastle disease virus (APMV-1) is the most important pathogen of this group for poultry; however, APMV-2, -3, -6, and -7 are occasionally associated with disease in chickens, turkeys, and ostriches.
Avian paramyxoviruses have been historically grouped primarily based on their hemagglutination inhibition reactivity with serotype‐specific sera. Currently, paramyxovirus species and isolates are defined based on genomic sequence similarities.
Experimental infections and pathogenicity studies in chickens with most APMV types did not produce clinical signs of disease, unlike APMV-1. Types APMV-6 and APMV-7 caused mild respiratory disease and affected egg production in turkeys.
Avian paramyxoviruses have been isolated from different wild birds worldwide. Primary infections in poultry are believed to be the result of contact with wild birds. The method of transmission to chickens or turkeys is unclear, but the fecal-oral route is considered to play a primary role. Once introduced in a turkey flock, the virus's transmission within the flock is usually slow.
Some APMVs are adapted to specific wild species and can cause serious disease—for example, APMV-5 in budgerigars.
Clinical Findings of Other Avian Paramyxovirus Infections
Because clinical signs of avian paramyxovirus infection are rarely observed, estimating the incubation period is challenging. Infections are restricted to the respiratory tract and sometimes the digestive tract. Infections with APMVs are more severe when accompanied by secondary pathogens, and it is not clear whether APMVs play a role as primary pathogen or cause underlying conditions that are exacerbated by infection with other viruses and bacteria.
Clinical signs vary among different APMVs:
APMV‐2, ‐3, and ‐6 infections have been associated with clinical symptoms in turkeys and have produced mild to severe respiratory disease, drops in egg production, decreased hatchability and infertility of eggs, and increased numbers of white-shelled eggs.
Infection with APMV-2 has produced mild respiratory disease in chickens; however, APMV-2 infection is usually most severe in turkeys, especially breeders. Sinusitis has been documented in turkeys infected with APMV-2.
Lesions are rare; enlargement of pancreas with focal necrosis has been reported in chickens infected with APMV-3. APMV‐3 has also been isolated from farmed ostriches in South Africa.
Turkeys with an APMV‐7 infection presented with rhinitis and airsacculitis. Enlarged pancreas and airsacculitis have also been observed in turkeys infected with APMV-7.
Enlarged spleens and livers have been reported in parakeets and doves infected with APMV-3 and APMV-7, respectively.
Diagnosis of Other Avian Paramyxovirus Infections
Detection of APMV RNA
Detection of specific antibodies
Virus isolation
Most diagnoses of avian paramyxovirus infection are made by laboratory confirmation after initial suspicion based on clinical signs. The APMVs can be isolated from oropharyngeal or cloacal swabs or from tissue samples from infected birds by inoculating the allantoic cavity of 9- to 11-day-old SPF embryonated chicken eggs. Confirmation of the virus as APMV can be made by hemagglutination inhibition tests with antiserum specific to individual serotypes, by specific rRT-PCR, or by genomic sequencing.
Of note, APMV-1 (Newcastle disease virus) and APMV-3 and APMV-7 may cross-react in hemagglutination inhibition tests (and in other serologic tests such as ELISA), which causes interpretation problems in vaccinated birds. Birds vaccinated against Newcastle disease show a rise in hemagglutination inhibition titers to both viruses if subsequently infected with APMV-3. Differential diagnosis includes infections with other pathogens that cause similar respiratory disease such as low pathogenicity avian influenza, infectious bronchitis, and avian metapneumovirus.
Prevention and Control of Other Avian Paramyxovirus Infections
Because there are no vaccines for some avian paramyxoviruses, implementing good biosecurity practices is the chief prevention strategy.
No vaccines are available for APMV-2, -6, and -7. Inactivated virus oil-emulsion vaccines against APMV-3 have been used in turkey breeder flocks. These are injected twice, 4 weeks apart, before the birds begin to lay (usually when 20–24 weeks old). Autogenous vaccines have been tested for different APMV types, but these are not widely used.
The risk of introducing APMVs from wild birds may be minimized by bird-proofing poultry houses and using good hygiene and biosecurity practices. Treatment of secondary bacterial infections with antibiotics has had some success.
Zoonotic Risk of Other Avian Paramyxovirus Infections
No infections in humans have been reported for APMV-3 to APMV-22 viruses. Serologic evidence of APMV-2 in humans has been reported but likely has no public health significance.
Key Points
Most infections with APMV 2–22 are inapparent in chickens.
APMV-2, -3, -6, and -7 have occasionally been associated with disease in chickens, turkeys, and ostriches.
Clinical course may be worsened by secondary infection.
For More Information
Suarez DL, Miller PJ, Koch G, Mundt E, Rautenschlein S. Newcastle disease, other avian paramyxoviruses, and avian metapneumovirus infections. In: Swayne DE, Boulianne M, Logue CM, McDougald CR, Nair V, Suarez DL, et al, eds. Diseases of Poultry. 14th ed. Wiley-Blackwell; 2020;111–166. doi:10.1002/9781119371199.ch3
Alexander DJ. Newcastle disease and other avian paramyxoviruses. Rev Sci Tech. 2000;19(2):443-462. doi:10.20506/rst.19.2.1231
