Wildlife Necropsy and Forensics

P.K. Sriraman

• Publisher: CRC Press
• Year: 2021
• ISBN:
  9781000386004
• Edition: 1
• Topic: Law
• Subtopic: Forensic Science
• Index: Law

The book discusses various necropsy procedures for wild animals both for the disease investigation and forensic usage. The list of various wildlife crimes, the role of each member of wildlife crime team investigation in general and the role of pathologist in particular, (the forensic veterinary pathology)and the salient features of methodology of crime investigation is given. Information on the mistakes and omissions in forensic necropsy, negative necropsy, common errors committed by pathologist while performing forensic necropsy, postmortem appearances of common pathological conditions and estimation of age of some of the domestic animals and their foetuses is given for guidance. Various types of wounds, and the types of firearms and their terminology are also given for easy understanding about the wounds and fire arms.
Note: T&F does not sell or distribute the Hardback in India, Pakistan, Nepal, Bhutan, Bangladesh and Sri Lanka.

Part I

Wildlife Necropsy

1 Introduction

The disease affects the viability of wild animal population. In a balanced ecosystem most populations survive with low levels of disease or with periodic epidemics. With habitat restrictions, the wildlife populations have become more dense leading to an increased risk of catastrophic epidemics. With restricted habitat of wildlife there are increased chances of disease transmission between wild and domestic animals. To determine the disease risks to a population, one must know (1) the causes of morbidity and mortalities in that population and (2) the natural history of infectious diseases in that environment, including the history of previous epidemics. Most often it is necessary to examine the entire animal to know the cause of epidemic.

Determination of cause of death of a wild animal is often difficult and need cooperation of a number of disciplines. A careful selection and preservation of specimens in suitable condition sent to the laboratory will help in the final diagnosis of cause of death. Many a times the carcass of a wild animal is found in an unsuitable condition for postmortem examination due to high ambient temperatures which cause a very rapid putrefaction of carcasses, common in tropics and due to the presence of avian and mammalian scavengers. The carcasses of young animals disappear without a trace. In view of this, every effort should be made to examine even a single carcass. Efforts should be made to detect and destroy a representative sick animal for postmortem examination (PME).The mortality rate and structure of population particularly of young, pregnant/lactating female and old animals can be altered due to extreme cold climate, wet and draught and nutritional stress due to deep snow cover or draught which hinders the growth of vegetation. Hence attention should be paid to local environmental factors. Similarly, epizootic disease, caused by an agent which is enzootic in contiguous domestic stock, may act similarly.

The determination of cause of death in non-domestic animals in captivity or natural habitat is difficult due to (1)Lack of history of the disease (2) Lack of observation before death, (3) Non exhibition of symptoms of illness until they are weak to walk, fly or crawl (4) Sudden death without showing gross and microscopic lesions and (5) Non familiarity of normal anatomy of wild animals by examiners.

Many disease epidemics affecting the wildlife or livestock go undetected if appropriate samples are not collected for diagnostic testing from animals that died during epidemics. Selective sampling limits the information that could be procured from a wild animal necropsy which could aid in future population or ecosystem management. In the case of captive animals, the veterinarian will focus on that one area (eye, brain, heart, etc)where the source of the problem originated. But it is necessary to examine the entire animal. In the case of a wild animal no idea of cause of death maybe known, while in captive animals the apparent cause of illness during life may simply mask the true cause of death. With appropriate samples and accurate written and photographic records the cause of an epidemic can be determined in most of the cases.

Wild animals rarely exhibit the signs of disease. Death may be as a result of an encounter with a predator that has taken advantage of the weakened state of the sick animal. In those species of animal with high reproductive rate, there is usually higher mortality among young ones. The carcasses of small and young animals disappear without traces.

In the investigation of any disease outbreak in wildlife, attention should therefore be paid to the local environmental circumstances, including those that may be affected by climate and man. The investigator must collect as much general and local information as possible, including any evidence of similar mortality or morbidity in domestic stock. When there is mass mortality it is important to examine (1). fresh carcasses of a number of animals, representative of the range of species affected and (2). the ages of individuals affected. One should remember that more than one disease process may be acting at any one time and that the major cause(s) of death may change during a prolonged mortality. The results of the postmortem examination with the history of the animal and assessment of the environment will help in determining their significance and recommending the future course of action. A thorough inspection of the surroundings of a sick or dead animal is vital. One must observe for signs of a struggle which may indicate an encounter with a predator or a paroxysm at the time of death. An accumulation of faeces behind the carcass may indicate a period of immobility, as may heavy browsing of food plants within easy reach. If the animal is found alive, it should be observed from a distance for any peculiarities of gait, respiration, excretion, unusual behaviour and unusual degrees of wildness or tameness. Photographs should be taken, illustrating environmental conditions and the appearance of sick animals and their lesions since these will be of great value if litigation is likely.

The performance of a thorough necropsy (post-mortem examination) plays an important part in the diagnosis of the cause of death. However, it is very important to avoid preconceptions that may limit the information and specimen collection. Determination of the cause of death in zoo animals is often difficult and may require the close co-operation of a number of disciplines. Some zoo veterinarians perform a post-mortem examination (PME) in the zoo. But in doing the post- mortem, careless observation and sampling can result in useless, and sometimes even harmful, information. Those who perform post-mortem examinations in this manner are running a risk, as overlooking fundamental changes in tissue can be costly. The specimen(s) collected must be selected carefully and preserved in suitable conditions. A thorough post-mortem examination of animals that die or are euthanized is a necessary adjunct to any good clinical practice. When a post-mortem is performed in the zoo itself, or samples are collected for diagnostic purposes, the results and information deriving from this activity are highly protocol sensitive. For a diagnostic laboratory to contribute fully to the final diagnosis, the specimen(s) collected must be selected carefully and preserved in suitable conditions. Collect complete tissue and blood samples from carcasses. If only selected samples are taken because a certain disease is suspected and if the animal does not have that disease, the specimens submitted to the laboratory may not be adequate for the diagnosis of other unsuspected diseases that may be involved in an epizootic. The pathologist uses the clinical history (including haematology, blood chemistry and therapeutic measurements), the gross description, culture results and other data, as well as the cytological and histological appearance of the lesions, to make a diagnosis. Absence of any of these, or incorrect submission of tissues, will hamper this process.

Postmortem examination may be performed by the case clinician or by a specialist/ pathologist. When the gross postmortem is performed by an individual other than the pathologist (who will perform further examinations on samples provided), communication between the two parties is essential to ensure that optimal samples are taken (tissue type, volume/ weight, storage, transport, temperature etc.). One cannot reach accurate diagnosis, if an inadequate or incorrect samples are collected.

Reasons for Carrying Out Post-mortem Examination(PME)

• To know the cause of death. It can reveal genetic, environmental and dietary problems which can be avoided or controlled in future generations.

• Without a postmortem one may not know what has happened to the dead animal. For the protection of the species it is necessary to know...