Mary Allen
It is the nightmare scenario of every rabbit owner: the rabbits that were healthy the night before are dead in the hutch in the morning. The first point of contact for determining the cause of death is the Department of Poultry and Rabbit Diseases at the University of Zurich.
Tiled walls, large, cold metal tables, and unusual, sometimes foul-smelling clouds of scent – the atmosphere in the section hall of the Vetsuisse Faculty at the University of Zurich takes some getting used to. The object under investigation, a rabbit weighing almost five kilograms with an unknown cause of death, lies on one of the large tables. Sarah Albini, Head of the Department of Poultry and Rabbit Diseases, opens the animal body with targeted cuts and sets out to find the reason for the long-eared bat’s unexpected death.
A few days earlier, Hoppel was perfectly healthy. The one-and-a-half-year-old red New Zealand buck was slightly over the ideal weight, but ate as usual and presented himself skilfully in the trained evaluation pose. Until the next day, he lay almost motionless, lethargic, and visibly weak in the stable and died a short time later. Due to the unclear situation, a dissection was arranged by telephone with the department for poultry and rabbit diseases.
Normally the dead animals arrive there well packed by parcel post (see box), are neatly unpacked, and provided with an identification number. First, the animals are weighed and searched for external features such as markings (ear tags, tattoos) and bite wounds. Then the focus is on possible ectoparasites such as mites: the harmful predatory mites (Cheyletiella parasitivorax) usually feel particularly at home in the shoulder area, while the harmless fur mites (Leporacarus gibbus) are primarily at home in the pelvic area; a few fur mites were found at Hoppel.
First, Come the Ribs
This is followed by the dissection of the animal. Albini has now opened the chest and is removing organ by organ. These are always removed according to the same process and arranged on trays so that any abnormalities in color, size, shape, or consistency are immediately recognizable: first the ribs, the lungs, and the heart as well as the trachea and esophagus. Next comes attention to the liver, kidneys, and gastrointestinal tract.
Lo and behold, Hoppel’s cause of death has been found: a liver lobe torsion. A lobe of the lever rotates around its own axis and blood vessels are clamped off. The blood flow is blocked, the blood stagnates and the rabbit eventually dies of cardiovascular failure. The exact cause of liver lobe torsion is unknown; Ram rabbits – especially dwarf rams – appear to be more susceptible, but solid data is lacking. Diagnosis on the live animal is only possible with specialized, targeted tests. In most cases, surgery is indicated for the survival of the rabbit.
This cause of death fits the description: “The rabbit was suddenly dead.” Secretly, however, the experts at the University of Zurich are hoping for further information on the animal bodies that are being sent in for dissection. Information on the type of husbandries such as individual, group, and free-range is helpful if it is important to rule out injuries from conspecifics or predators. The health of the other rabbits in the hutch gives clues as to whether contagious diseases or widespread feeding problems are involved. And the medical history – such as vaccinations or previous treatments – are often good indicators of which traces to follow or discard.
After the organs, Albini addresses further detailed questions. A cut in the muscle flesh, an examination of the genitals or the aorta provide further information about a possible cause of death and the state of health. It is also important to check parts of the body that can be particularly affected by infections; in rabbits, this is, in particular, the tympanic cavity. This is the name given to the cavity of the middle ear, in which the auditory ossicles are located. This can sometimes be completely filled with pus with residues of bacteria (often Pasteurella multocida).
The cause of death has been found for Hoppel and the autopsy can be completed with a clear conscience after the macroscopic assessment of the organs. Normally, however, further examinations follow: samples of the liver, stomach, and intestines, which are analyzed under the microscope, provide information about parasites such as appendicitis or the well-known coccidia of the Eimeria genus. And if there are signs of infection, bacteriological analyzes bring more clarity; however, these usually last a few days. Finally, viruses – such as the causative agents of myxomatosis or viral hemorrhagic disease (VHK) – are detected using a PCR test; the same procedure currently used for the novel human coronavirus.