Psittacine Herpes Virus Update by Dr Phalen

Epizootiology, Diversity, and Pathogenicity of Psittacine Herpes Virus 

Presenting Author: David Phalen, DVM, PhD, Dipl ABVP (Avian)

Schubot Exotic Bird Health Center,Texas A&M University, TX

Interpretive Review and comments by Dr. Nemetz:

In a continuation of the research on Psittacid herpesvirus, Dr. Phalen, Dr. Styles, et al brought new important information to this year's conference attendees.


Pacheco disease virus, a potentially deadly disease, is now known as the Psittacid herpesvirus (PsHV 1) that causes Pacheco's disease and mucosal papillomas (Click Here for Dr. Styles paper regarding PsHV-1 association with mucosal papillomas). PsHV 1 can produce an acute fatal disease or a latent disease process that can lead to mucosal papillomas and sometimes bile duct and pancreatic duct carcinomas. Amazon parrots seem the most susceptible. 

There are two genetically distinct viruses, PsHV 1 and PsHV 2. We will talk more about PsHV 1 since more is known about this virus. PsHV 2 seems at the moment to be restricted to African grey parrots. PsHV 1 has four genotypes and 3 serotypes. I will list them as PsHV 1-11, PsHV 1-22, PsHV 1-33, and PsHV 1-41.

These genetic variants seem host adapted. Because of this, Pacheco's disease and mucosal papillomas became diseases of captivity when latently infected species and susceptible species were commingled. This is VERY important because the spread and disease occurred by housing multiple species within the same environment.

The species diagnosed most often with this disease are Amazons (Amz), followed by macaws (M) and in equal numbers, African grey parrots (AG), conures (C), and birds from the Pacific Distribution (PD). PsHV 1-11 can also infect passerines (finches, canaries, and possibly toucans). 

Most papillomas seem to develop within a year of infection and if cancer occurs, it seems to develop within a few years from the onset of mucosal papillomas. This could help with tracing the origin of the infection. Possible origin of the genotypes in the wild is as follows: 

                        Adapted Host                     Causes Pacheco's in:       Causes Papillomas

PsHV 1 - 11    Red shoulder macaws (Noble)        Amz, AG, PD                     Uncommon <13%

PsHV 1 - 22    Aratinga spp. (Conures)               Amz, PD                           Uncommon

PsHV 1 - 33    Hyacinth macaws                       Amz, M, AG, C, PD              Most common

PsHV 1 - 41    Patagonian conures                    Amz, M, AG, C, PD              Rarely

(Other species may be involved but have not been discovered as of yet)

Oral and fecal routes seem the most likely means of viral transmission. Once infected, parrots are latently infected for life. What triggers reactivation and presentation of disease is still not known, but the onset of breeding, stress, and concurrent disease are likely triggers.


The research by Dr. Phalen's group brings new insight and some cause for alarm regarding Psittacid herpesvirus and its pathogenicity. Last year I recommended that ALL amazons and macaws with discovered mucosal papillomas be removed and isolated from any collection to prevent a potential Pacheco's outbreak or spread of this potentially lethal virus. 

There is now a diagnostic test available to discover latent carriers of PsHV 1 Genotype 1-4. It is recommended that ALL clients test their birds for potential carriers to help prevent further spread of latent carriers and possible disease outbreaks. Boarding and commingling of avian species, as I have mentioned many times, is the SINGLE GREATEST RISK of disease for your pet bird. Be aware of these research updates and don't let your beloved pet become a sad statistic.

The BIRD Clinic Veterinary Corporation will institute new safety measures in its limited boarding of client's birds. In 2005 Donna Garrou and  Dr. Nemetz created a new independent, safe, quarantine-style facility to further safe guard against the risk of Psittacid Herpesvirus or other airborne diseases affecting exotic avian species called birdStuff.
The store can be reached as another resource at (714) 639-6039.

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