Abstract
Early in January, I was presented with 8 dead Half moon parrots with the explanation that in a group of some 500 birds, several hundred had suddenly died and more were dying. Upon gross examination, each bird was found to be in good flesh, its crop was empty, and its liver was conspicuously light yellow in color under a multitude of pinpoint to larger red spots, hemorrhages. Other organs were not as striking in appearance although often the spleens were enlarged, sometimes almost black in color, and there was often an increase in the amount of fluid around the heart. The duodenum, the uppermost loop of the intestine, often appeared dark red to purple in color. As the laboratory examination continued, it became clear that no bacterial agent could be incriminated. An emulsion of the liver, when inocculated into the yolk sac of 5 to 7 day old embryonating chicken eggs, caused their death within 3 to 4 days and produced a generalized reddening of the embryo and its membranes. Tests confirmed that neither Newcastle Disease virus nor Influenza were the cause of death. Microscopic examination of prepared sections of the livers revealed the presence of a severe, generalized degeneration, and most importantly, the presence of many intranuclear, acidophilic inclusion bodies, structures which signal the presence of several kinds of virus. In fact they resemble the ones which we see in Pacheco's Parrot Disease, caused by a type of virus called Herpes. However, none of the other characteristics of the disease were consistent with a diagnosis of Pacheco's Parrot Disease as I have seen it nor as it is described in the literature.
There is a disease of chickens which resembles this one of parrots in many respects. It is called Inclusion Body Hepatitis or IBH. The gross lesions are quite similar, especially those of the liver. It is caused by one of the many adenoviruses which infect animals, birds, and man. Many of them appear to be innocuous, although many cause disease of one kind or another. The adenoviruses produce the same kind of inclusion bodies as I saw in the parrot livers. Work is continuing on a specific identification of the virus, but until it can be completed, several weeks or months from now, I am going to make a tentative, working identification of the virus and call the disease Inclusion Body Hepatitis of Psittacines or IBHP.
Even at this early stage, we must make some assumptions as to how IBHP is spread, which of the species it may in feet, and what can be done to control it.
Preliminary evidence strongly suggests that this group of Halfmoons is not the source of the infection, but rather is its victim. The birds passed through a quarantine station with remarkably low losses, and another lot of some 1,000 of the same birds, which went to another premise, continues in good health. The same situation holds for a large shipment which went to Texas. To confuse the picture, birds which are known to have had intimite contact with the specific group of 500, all of whom died by the way, have not been shown to have IBHP, at least they are not dying of it. Another group of Half Moons, isolated a short distance from the original group of 500, has subsequently become infected and have all died. In addition, a presumptive diagnosis of IBHP has been made in a Double Yellow Headed Amazon, a Finsches Amazon, an Eclectus, and in a Sulphur Crested Cockatoo. In contrast, it appears that Budgerigars, Nanday and Patagonian Conures, as well as Red Caps or Cherry Heads are not affected, at least they haven't died although they have been exposed. This list is woefully incomplete, and may be innacurate, but it represents our preliminary findings and may be useful as a working outline. I hope that any of you who comes upon further pertinent information as to species susceptibility will share it with us for our mutual benefit.
If IBHP is really caused by an adenovirus, no hope for an effective treatment should be entertained. As is the case with Exotic Newcastle Disease, prevention, identification, and eradication will be our most valuable tools in its control.
It will probably be found to be spread partly by obviously sick birds, but quite likely by apparently healthy birds as well. Probably the virus will be found in most of the body fluids and in the droppings. We don't know the length of the incubation period, the period between infection and illness or death, but it may be as short as one week. Individual birds may appear healthy in the morning and be dead before evening.