The marsh deer (Blastocerus dichotomus) is the largest Brazilian cervid. It is considered in danger of extinction by the IBAMA (National Brazilian Institute of Natural Resources), vulnerable by IUCN classification, and is listed in Appendix I of CITES. The main causes of the decline of this species are habitat loss and degradation. The marsh deer is an animal with very specific habitat requirements, living in marsh areas. With the formation of the Sérgio Motta hydroelectric power plant reservoir in the Paraná river basin, between the states of São Paulo and Mato Grosso do Sul, Brazil, an area of approximately 200,000 hectares were flooded, most of them constituting low land bordering the river. The flooding negatively affected the regional marsh deer population.
A project was implemented designed to:
1. Study the genetic, ecologic, behavioral, health conditions, and physiologic aspects of marsh deer
2. Study the effects of the reservoir on the resident deer population
3. Initiate an ex situ conservation program
As part of the ex situ program, deer were captured and removed to a 60 to 120 day quarantine, when they were evaluated for infectious diseases and adapted to captivity. After quarantine, animals were sent to institutions participating in the ex situ conservation program. The main objective of this study was the determination of the main causes of death for marsh deer in the ex situ program from July of 1998 to May of 2000.
Material and Methods
A complete postmortem examination was performed on the 72 marsh deer that died during the program.
The animals were divided in three main groups:
1. Animals that died during capture and quarantine (n=41)
2. Animals that died in captivity at the participating institutions (n=27)
3. Offspring (n=4)
Macroscopic lesions were recorded during necropsies and representative tissues from all organ systems were collected, fixed in 10% formalin and processed routinely for histopathology.
The main causes of death, in descending order, for animals in group 1 were: cachexia (macroscopically characterized by emaciation, absence of food in the gastrointestinal tract); pneumonia; bacterial sepsis; capture myopathy; hyperthermia; and euthanasia (usually animals that had traumatic injuries). The animals of group 2 succumbed to: cachexia, bacterial sepsis, hyperthermia, and capture myopathy (during handling). Finally, the animals of the group 3 died mainly of cachexia and pneumonia.
Cachexia was the main pathologic alteration found in the marsh deer in any of the analyzed groups. This could have been related to poor adaptation to captivity, stress, nutritional factors, and endo- and ectoparasitism. Notably some of the quarantine animals had severe flea infestations which caused severe anemia. Pneumonia cases were occasionally consistent with aspiration, and probably were related to anesthesia. The cases of capture myopathy recorded during the capture phase of the project were not as frequent as what was anticipated at the onset of the program. This demonstrated the efficiency of the capture process. Some capture myopathy cases occurred, however, during the handling of the animals in captivity. Hyperthermia was a mortality event only during transport. Euthanasia was performed only in animals that suffered traumatic injuries such as multiple fractures or irreversible dislocation, where treatment was very difficult or impossible. Many animals had multiple, interrelated processes. Many cachectic animals had evidence of immunosuppression, such as splenic lymphoid depletion, and subsequent bacterial infection (sepsis) was a common sequela. This association was very common since, particularly at the outset of the program, animals were often debilitated. Finally, common causes of death: cachexia, sepsis, and pneumonia, were largely related to the predisposing factors of capture and captivity. Maladaption to captivity was manifested by chronic forms of anorexia, intense ectoparasitism, traumatic injury, and opportunistic infections.
Financial support for this work was provided by CESP - Energetic Company of São Paulo.