findings: Influenza virus will be hematogenously disseminated (affect all lobes). The lungs can be hemorrhagic or consolidated (interstitial pneumonia). Again, lungs are among the most difficult of organs in which to detect gross changes; histological analysis is of paramount importance in evaluating the sequelae of the virus and/or co‐infections in the lungs. The tissue collection protocol that was elaborated for respiratory disease sample collection should be followed.
PCR: Fresh, or fresh frozen respiratory tissue is always best, but RNA extracted from paraffin‐embedded tissues has been used to detect the virus. Laboratories that offer this type of testing are limited but will accept samples by courier. Some specific instructions are listed below.
US:
https://www.idexx.com/en/veterinary/reference‐laboratories/canine‐feline‐influenza
California:
https://pcrlab.vetmed.ucdavis.edu/veterinary‐diagnostics
New York:
https://ahdc‐portal.vet.cornell.edu/#!/test_fee/search
Wisconsin:
https://www.wvdl.wisc.edu/index.php/canine‐influenza‐information‐for‐veterinarians
5.5.3.2.4 Feline infectious respiratory disease (FIRD) (Upper respiratory infection (URI))
FIRD is typically multifactorial, and, like CIRD, recognition of the contributory infectious agents can be very helpful in organizing a response. Moreover, unusual agents, or unusually virulent agents have plagued some shelters. The most commonly recognized agents involved in infections limited to the upper respiratory tract are feline calicivirus (FCV), feline herpesvirus (FHV1), Mycoplasma, Chlamydia, and occasionally B. bronchiseptica (Pesavento and Murphy 2014). Other bacterial organisms such as Streptococcus canis have also and more recently been described in outbreak situations (Pesavento et al. 2007). Nasal swabs can be performed postmortem, and sampling in an outbreak of severe FIRD should include the histological samples described in the general section on respiratory disease. Many diagnostic laboratories now offer PCR panels for the most common organisms associated with FIRD. Nonetheless, the presence of the pathogen does not always imply causation, and concurrent culture and histology can be very helpful in identifying the cause. Gross assessment cannot distinguish among even the most common agents involved in FIRD, however, it is helpful to note the character of the nasal conchae, lungs, and whether or what type of fluid is present within the sinuses.
5.6 Other Shelter Necropsies
5.6.1 Necropsy on a Previously Healthy Animal Found Dead
5.6.1.1 Acute Death
Common causes of acute death, with special attention to possible shelter situations or submissions are anaphylaxis, physical trauma (with neurologic or hemorrhagic consequences), intestinal malpositions (volvulus, intussusception), cardiomyopathy, electrocution (lightning or chewing on electric cords), gunshot, drowning, septicemia, heatstroke, dehydration, or ingestion of toxins or poisons (plant or synthetic, including disinfectants). Note that the most common cause of acute death in incompletely vaccinated shelter cats is panleukopenia. While some of these conditions may be obvious on gross necropsy (physical trauma, intestinal malpositions, gunshot, cardiomyopathy), in others histopathology is useful (e.g. some toxins, septicemia); still others are unlikely to have either gross or histological lesions (e.g. anaphylaxis, dehydration, electrocution, some toxins, heat stroke). Even in this latter subset, a gross necropsy effectively rules out most possible causes of disease. In all cases, diagnosis requires a good history to arrive at the definitive diagnosis.
5.6.2 Feline Infectious Peritonitis (FIP)
There is no single, predictable target organ for feline infectious peritonitis (FIP). The virus widely (systemically) disseminates in macrophages, and the clinical outcome is dependent on both the host immunity and the specific organ affected. Histopathology on biopsy or necropsy specimens remains the gold standard for diagnosis. Many of the pre‐mortem tests, and especially a cumulative amount of information, can be highly suggestive of the disease. If an animal dies or is euthanized with suspect FIP, a necropsy with histology would be diagnostic.
Gross findings: In the effusive form, there will be fluid within either or both the thoracic and abdominal cavities. The fluid is high in protein and may vary from slightly viscous to gelatinous. The surfaces of the viscera are covered with tiny (1–5 mm) friable, pale tan to white plaques (fibrin) that can give the surfaces a granular appearance (See Figure 5.9).
In the non‐effusive (chronic) form, there will be nodules (granulomas) of variable size present in one or multiple organs. These can vary in color from off white to light tan, in texture from slightly firm to soft. The nodules are typically associated with capsular or serosal vessels, although when abundant this can be difficult to distinguish. Within organs, the granulomas can be scattered throughout the parenchyma. Lymph nodes are often enlarged.
Figure 5.9 Feline infectious peritonitis (FIP) virus (feline coronavirus). In the effusive form of FIP, along with intracavitary fluid, the surfaces of abdominal and thoracic viscera are covered with small (1–2 mm) to coalescing pale tan plaques.
Formalin‐fixed tissues: Samples should be taken from affected organs (in the case of the non‐effusive form, this would be any viscera with detectable granulomas). In the case of the effusive form, multiple samples should be taken from affected viscera (liver, GI, lung). If the clinical presentation is limited to the nervous system and FIP is suspected, it is imperative to submit the brain. Brain lesions are, however, rarely uniquely present.
5.7 Conclusion
It is impossible to provide necropsy guidelines for every infectious disease encountered in shelter animals—therefore a few characteristic diseases were selected. It is hoped that the information in this chapter will enable the shelter veterinarian to work more closely with pathologists and microbiologists to develop good shelter surveillance programs. This chapter should aid veterinarians in collecting samples so that the pathologist and the diagnostic laboratory can analyze and diagnose problems more accurately. Necropsy has multiple potential roles in shelter animal health: it is a method to detect disease, to establish the cause of death, to assess diagnostic suitability in a single animal, and as a source of knowledge to apply to future cases.
References
1 American Society for the Prevention of Cruelty to Animals (2017). Are Anmal Shelter Outcomes Improving? https://www.aspca.org/blog/are‐animal‐shelter‐outcomes‐improving (accessed 4 August 2020).
2 Decaro, N. and Elia, G. (2005). A real‐time PCR assay for rapid detection and quantitation of canine parvovirus type 2 in
