Pacheco's Disease in Birds: Causes, Signs, Treatment, and Prevention
Veterinary & Aquatic Services Department, Drs. Foster & Smith

parrotAlso known as Parrot Herpesvirus, Pacheco's Disease causes acute viral hepatitis. First observed in the 1930's and thought to attack only Psittacines, there is one documented case of a Keel-billed Toucan succumbing to Pacheco's Disease. New World (from the Americas) parrots seem to be more susceptible to Pacheco's Disease than Old World parrots (from Australasia and Africa).

What causes Pacheco's Disease?

Pacheco's Disease is caused by a herpes virus. Often seen in shipments of imported birds, stress seems to trigger a reaction in a previously asymptomatic carrier or increase the susceptibility of becoming infected. The close proximity and stressful nature of shipping appear to contribute to the transmission of the virus.

How is Pacheco's Disease transmitted?

Mitred ConureUsually, Pacheco's Disease is transmitted via contact with contaminated food, water, or feces. Less common is airborne transmission. The virus can be contracted from an obviously ill bird as well as from carriers, who appear asymptomatic, but can shed the virus in feces as well as through ocular and respiratory secretions. Examples of species commonly seen as carriers and seem to have a resistance to the virus include Mitred, Nanday, and Patagonian Conures; however, any bird that recovers from Pacheco's Disease can become a carrier. At risk populations include imported birds, those housed in aviaries and pet stores in large groups, and those in quarantine stations.

What are the symptoms of Pacheco's Disease and how is it diagnosed?

The incubation period for Pacheco's Disease is 3-14 days. Unfortunately, the most common symptom is sudden death, with diagnosis confirmed at necropsy. Other symptoms can include diarrhea with a rapid progression to death within 48 hours. One may also see regurgitation, yellow-green urates, and acute central nervous system signs such as tremor, imbalance, or seizures. Necropsy often reveals enlarged kidneys, liver, and spleen, circumscribed areas of necrosis on the liver, and hemorrhage. The skin, spleen, intestines, pancreas, and body cavity may also show signs of hemorrhage. Diagnosis is based on history (such as recent importation), clinical symptoms, and viral isolation from infected tissues.

What is the treatment for Pacheco's Disease?

Pacheco's Disease is generally considered untreatable because of its sudden onset and rapid death. There has been some success with the antiviral drug acyclovir followed by supportive treatment including fluid administration, isolation, and tube feeding (gavage). The best treatment for Pacheco's Disease is considered to be prevention.

How is Pacheco's Disease prevented?

Strict observance of good husbandry techniques and quickly isolating suspected cases are the best preventive measures to take. In cases where carriers are suspected, some suggest serologic testing for the virus. However, due to problems of false negatives and the fact that all positive birds do not shed the virus, others do not yet consider this a reliable diagnostic tool.

 
References and Further Reading

Da Cunha, MB; Correia, JJ; Fagulha, T; Fevereiro, M; Peleteiro, MC; Vollrath, G; Kaleta, EF. Pacheco's parrot disease in macaws of the Lisbon's Zoological Garden. Description of an outbreak, diagnosis and management, including vaccination. Dtsch Tierarztl Wochenschr. November 2007;114(11):423-8.

Olsen, GH; Orosz, SE. Manual of Avian Medicine. Mosby, Inc. St. Louis, MO; 2000.

Phalen, DN. Viruses. Altman, RB; Clubb, SL; Dorrestein, GM; Quesenberry, Katherine (eds.) Avian Medicine and Surgery. W.B. Saunders Co. Philadelphia, PA; 1997.

Rupley, AE. Manual of Avian Practice. W.B. Saunders Co. Philadelphia, PA; 1997.

Spandofori, G; Speer, BL. Birds for Dummies. IDG Books Worldwide, Inc. Foster City, CA; 1999.

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