Goose parvovirus infection is a highly contagious and fatal disease of goslings and Muscovy ducklings, often causing as much as 70%−100% mortality in goslings <4 wk old. Goose parvovirus has been reported from all the major goose-farming countries of Europe and the Far East, where the disease is of serious economic significance. Muscovy ducks and several hybrid duck breeds are also susceptible to another parvovirus that has been shown to be antigenically related to goose parvovirus. This so-called Muscovy duck parvovirus has been isolated from an outbreak among Muscovy ducks in California. Goose parvovirus has not been detected in the USA.
Goose parvovirus is a member of the family Parvoviridae and, based on phylogenetic analysis, has been shown to be related to the dependovirus genus. Apart from the Muscovy duck parvovirus, to which it is closely related, goose parvovirus shows no similarity to the other avian or mammalian parvoviruses. After primary infection, the virus replicates in the intestinal wall and, after a short viremic phase, reaches the heart, liver, and other organs.
Transmission and Epidemiology:
The virus is excreted in large amounts in the feces of infected birds, resulting in rapid spread by direct and indirect means. Outbreaks are often initiated in susceptible goslings after transmission of the virus via eggs laid by infected breeder geese. Evidence suggests that older, subclinically infected geese may act as carriers. Infected eggs are often the source of the virus when outbreaks of goose parvovirus occur in countries or geographic locations formerly free of the disease. Serologic evidence suggests that the virus is present in several species of wild geese in Europe. No other avian or biologic vectors have been identified.
In susceptible goslings and ducklings, clinical signs vary according to the age of the birds. The course of the disease in birds <1 wk old is rapid, with anorexia and death occurring within 2–5 days. Mortality can reach 100% in birds infected in the hatchery. In older birds, the disease follows a more protracted course, characterized by ocular and nasal discharge, a profuse white diarrhea, and weakness. The eyelids and uropygial glands are red and swollen. Birds that survive the acute stage show profound growth retardation, with loss of feathers and reddening of the skin, particularly on the back. Birds may stand in a “penguin-like” posture due to accumulation of ascitic fluid in the abdomen. In 2- to 4-wk-old birds, mortality can reach 10%, but morbidity levels may be much higher. No clinical signs are seen in older birds, although adults will respond immunologically. An enteric form of goose parvovirus infection has been documented to exist.
Gross lesions include the presence of a fibrinous pseudomembrane covering the tongue and oral cavity, perihepatitis, pericarditis, pulmonary edema, liver dystrophy, and catarrhal enteritis. In acute cases, the heart is characteristically rounded at the apex, with a pale myocardium. The main microscopic lesions are pronounced degenerative changes in the myocardial cells and the presence of Cowdry type-A intranuclear inclusion bodies.
A presumptive diagnosis is based on the characteristic clinical course, age incidence, and gross and histologic lesions. Confirmation can be obtained after isolation of the parvovirus in cell cultures or embryonated eggs derived from susceptible geese and Muscovy ducks. Presence of the virus can be confirmed by electron microscopic examination of infected cultures and neutralization with specific goose parvovirus antiserum. Diagnosis can also be confirmed by direct detection of antigen or virus in tissues from infected birds, by immunofluorescence, or by the use of PCR. Serologic tests for goose parvovirus include virus neutralization, agar gel precipitation, immunofluorescence, and ELISA.
Although goose parvovirus causes disease in both geese and Muscovy ducks, Muscovy ducks are also infected with another antigenically related parvovirus. This virus causes serious disease in Muscovy ducklings, but not in goslings, and can be detected and differentiated using PCR combined with sequencing or restriction fragment length polymorphism. Differential diagnoses should also include duck viral enteritis (duck plague, see Duck Viral Enteritis Duck Viral Enteritis ), which affects all types of waterfowl. Duck viral hepatitis ( see Duck Viral Hepatitis Duck Viral Hepatitis ) causes a fatal disease in ducklings but is not pathogenic for goslings or Muscovy ducklings. Riemerella anatipestifer and Pasteurella multocida may also cause high mortality in goslings and Muscovy ducklings but can be differentiated by bacterial isolation and identification.
Prevention and Treatment:
Goslings should be hatched together only from flocks that are known to be free of goose parvovirus; many outbreaks are attributed to the practice of custom-hatching eggs from various sources. Eggs should be imported only from countries that can guarantee freedom from goose parvovirus. Geese that have survived an outbreak should not be used for breeding purposes. Both live, inactivated oil emulsion vaccines and baculovirus expressed VP2 capsid-based recombinant vaccines are available and are widely used in countries where the disease is endemic. Vaccination of breeding flocks induces high levels of maternal antibody in the progeny until ~2 wk of age.