Jason W. Brooks

A Retrospective Study of Mortality in Pennsylvania Captive White-Tailed Deer (Odocoileus Virginianus): 2000–2003

The postmortem records of 160 white-tailed deer (Odocoileus virginianus) submitted for necropsy examination from 59 separate Pennsylvania captive deer farms over a 3.5-year period were reviewed to determine the primary cause of death of each animal. The most common causes of death were bronchopneumonia (39 cases), enterocolitis (30 cases), malnutrition (13 cases), and trauma (11 cases). Other causes of mortality included severe gastrointestinal parasitism (6 cases), cellulitis with septicemia (5 cases), degenerative myopathy (4 cases), ruminal acidosis (4 cases), and nephritis (4 cases). The cause of death was undetermined in 13 of the 160 animals. Arcanobacterium pyogenes (19 cases), Fusobacterium necrophorum (10 cases), Escherichia coli (7 cases), and Mannheimia haemolytica (4 cases) were the most commonly isolated bacteria from the pneumonic lungs. Bacterial agents associated with enterocolitis included Clostridium perfringens (15 cases), E. coli (12 cases), and Mycobacterium avium subsp. paratuberculosis (2 cases). The majority (52.2%) of the death loss in white-tailed deer of known ages occurred in animals 1 year of age or less, with 46.2% of the bronchopneumonia cases and 50.0% of the enterocolitis cases occurring during this time period. Cases of degenerative myopathy, myocardial degeneration, hepatic necrosis, meningoencephalitis, peritonitis, and urolithiasis considered severe enough to be the primary cause of death appeared early in life, affecting deer 6 months of age or less in all cases. In conclusion, bronchopneumonia, enterocolitis, malnutrition, and trauma were considered the most common causes of death in confined white-tailed deer in this study.

Antimicrobial susceptibility of Arcanobacterium pyogenes isolated from the lungs of white-tailed deer (Odocoileus virginianus) with pneumonia.

In vitro susceptibilities of 29 strains of Arcanobacterium pyogenes isolated from lung lesions of white-tailed deer (Odocoileus virginianus) with pneumonia were determined using the broth microdilution method to ascertain efficacious treatment options for pneumonic white-tailed deer. All 29 A. pyogenes strains tested were susceptible to ceftiofur, spectinomycin, tiamulin, and trimethoprim–sulfamethoxazole but were resistant to both danofloxacin and sulfadimethoxine. Likewise, all 29 isolates were either fully susceptible or intermediately susceptible to gentamicin (25 susceptible; 4 intermediate) and tulathromycin (25 susceptible; 4 intermediate). At least one isolate of A. pyogenes tested was resistant to ampicillin, chlortetracycline, clindamycin, enrofloxacin, florfenicol, oxytetracycline, penicillin, and tilmicosin suggesting their ineffectiveness in treating A. pyogenes–associated lung infections in white-tailed deer. Minimum inhibitory concentration (MIC) data for tylosin and neomycin could not be interpreted due to unavailability of Clinical and Laboratory Standards Institute (CLSI)-approved breakpoints for these 2 agents. In summary, based on MIC values, ceftiofur, spectinomycin, tiamulin, and trimethoprim–sulfamethoxazole are more efficacious than other antimicrobial agents for treating A. pyogenes–related pneumonia in white-tailed deer. However, ceftiofur may be preferred over the other 4 drugs as it is being widely used to treat respiratory disease in cattle and other animal species, as well as is available for single dose parenteral administration.

Mortality in Pennsylvania captive elk (Cervus elaphus): 1998-2006.

The necropsy records of 65 elk ranging from 1 day to 13 1/2 years of age were reviewed to determine the primary cause of death of each animal. The animal carcasses were submitted from 22 separate Pennsylvania elk farms over an approximately 8-year period. The most common causes of mortality in animals in which the cause of death was determined were gastrointestinal parasitism (21 cases), pneumonia (7 cases), enterocolitis (5 cases), malnutrition (5 cases), and rumenitis/acidosis (5 cases). The cause of death was undetermined in 4 of the 65 elk. Nematode organisms (20 cases) were the primary parasites identified in cases of mortality owing to gastrointestinal parasitism. Arcanobacterium pyogenes (3 cases), Escherichia coli (3 cases), and Streptococcus sp. (2 cases) were the most commonly isolated bacteria from the lung in the cases of pneumonia. Fungal organisms, consistent with Aspergillus sp. were present histologically within the pulmonary lesions in 5 cases. Bacterial agents associated with enterocolitis included Clostridium perfringens (2 cases), E. coli (1 case), Salmonella Newport (1 case) and Salmonella Thompson (1 case). The majority (56.3%) of the death loss in elk of known ages occurred in animals 1 year of age or less, with 71.4% of the gastrointestinal parasitism, 60.0% of the malnutrition, 60.0% of the enterocolitis, and 57.1% of the pneumonia cases occurring in animals within this age range. In conclusion, gastrointestinal parasitism, pneumonia, malnutrition, enterocolitis and rumenitis acidosis were considered the most common causes of death in captive elk in this study.

Failure to Detect Bovine Viral Diarrhea Virus in Necropsied Farm-Raised White-Tailed Deer (Odocoileus Virginianus) in Pennsylvania

Between January 1 and December 31, 2005 gross and histologic examinations were performed on carcasses of 61 farm-raised white-tailed deer originating from Pennsylvania. Single-tube real-time reverse transcription polymerase chain reaction (real-time RT-PCR) for the detection of bovine viral diarrhea virus type 1 (BVDV-1) and type 2 (BVDV-2) was performed on each animal. Virus isolation was performed on tissue samples from 25 of 61 animals. Immunohistochemical (IHC) staining of ear-notch skin to identify BVDV antigen was performed on each animal. All tissues samples tested negative for both BVDV-1 and BVDV-2 by real-time RT-PCR, virus isolation, and IHC. Gross or histopathologic lesions suggestive of BVDV infection were not detected. Results of this study suggest that BVD is not a common cause of mortality in farm-raised white-tailed deer in Pennsylvania.

Next step in the ongoing arms race between myxoma virus and wild rabbits in Australia is a novel disease phenotype

Significance When a pathogen emerges in a host population, will it evolve to do more or less harm to its host? A single strain of myxoma virus was released as a biocontrol agent against Australian rabbit populations in 1950. The subsequent coevolution has become a textbook classic, although there has been little experimental work on this topic since the early 1980s. Here, we show that the host–pathogen arms race continued with the evolution of highly lethal viruses that cause immune collapse. The possibility that pathogens can become highly immunosuppressive in response to increases in host resistance needs to be considered where genetic and immunologic manipulations are used to enhance host resistance, as, for instance, in agriculture. In host–pathogen arms races, increases in host resistance prompt counteradaptation by pathogens, but the nature of that counteradaptation is seldom directly observed outside of laboratory models. The best-documented field example is the coevolution of myxoma virus (MYXV) in European rabbits. To understand how MYXV in Australia has continued to evolve in wild rabbits under intense selection for genetic resistance to myxomatosis, we compared the phenotypes of the progenitor MYXV and viral isolates from the 1950s and the 1990s in laboratory rabbits with no resistance. Strikingly, and unlike their 1950s counterparts, most virus isolates from the 1990s induced a highly lethal immune collapse syndrome similar to septic shock. Thus, the next step in this canonical case of coevolution after a species jump has been further escalation by the virus in the face of widespread host resistance.

Management practices used by white-tailed deer farms in Pennsylvania and herd health problems

OBJECTIVE To determine current management practices used by white-tailed deer farms in Pennsylvania and identify animal health problems that exist in these herds. DESIGN Cross-sectional study. STUDY POPULATION Owners and managers of 233 farms in Pennsylvania that raised white-tailed deer. PROCEDURES A self-administered questionnaire was mailed to participants. RESULTS Herds ranged in size from 1 to 350 deer. Land holdings ranged from 0.07 to 607 hectares (0.17 to 1,500 acres). Stocking density ranged from 0.1 to 118.6 deer/hectare (0.04 to 48 deer/acre). Most (84%) respondents raised deer for breeding or hunting stock; 13% raised deer exclusively as pets or for hobby purposes, and purpose varied by herd size. Multiple associations were identified between management or disease factors and herd size. The use of vaccines, use of veterinary and diagnostic services, use of pasture, and use of artificial insemination increased as herd size increased. The most common conditions in herds of all sizes were respiratory tract disease, diarrhea, parasitism, and sudden death. The prevalence of respiratory tract disease increased as herd size increased. CONCLUSIONS AND CLINICAL RELEVANCE Results suggested that many aspects of herd management for white-tailed deer farms in Pennsylvania were associated with herd size, but that regardless of herd size, many preventive medicine practices were improperly used or underused in many herds.

Characterization of Fusobacterium isolates from the respiratory tract of white-tailed deer (Odocoileus virginianus)

A total of 23 clinical isolates of Fusobacterium spp. were recovered at necropsy over a 2-year period from the respiratory tract of white-tailed deer (Odocoileus virginianus). Isolates were identified as Fusobacterium varium (18/23), Fusobacterium necrophorum subsp. funduliforme (3/23), and Fusobacterium necrophorum subsp. necrophorum (2/23). Using polymerase chain reaction–based detection of virulence genes, all F. necrophorum isolates were positive for the promoter region of the leukotoxin operon and the hemagglutinin-related protein gene, while all F. varium isolates were negative. The presence of the leukotoxin gene in F. necrophorum isolates and the absence of this gene in F. varium isolates were confirmed by Southern hybridization using 2 separate probes. Toxicity to bovine polymorphonuclear leukocytes was observed with all F. necrophorum isolates, but was not observed in any F. varium isolates. Susceptibility to antimicrobials was markedly different for F. varium as compared to F. necrophorum. In summary, no evidence of leukotoxin production was detected in any of the 23 F. varium isolates used in the current study. The data suggests that F. varium, the most common species isolated, may be a significant pathogen in deer with a different virulence mechanism than F. necrophorum.

Age Determination in Dogs and Cats

This chapter addresses age determination in domestic dogs and cats through assessment of rates of physeal and ossification center appearance and closure across different breeds. Two types of data tables were created first by completing an extensive review of the published literature on physeal and ossification center appearance and closure rates and then by validating the published data with radiographs from the University of Florida: College of Veterinary Medicine’s Small Animal Hospital. The first table created was a modification of previously published data documenting the approximate ages for appearance and closure times of physes and ossification centers at each of the major body regions. The second table created was unique to this study listing physes and ossification centers at the diaphysis, distal, and proximal epiphyses, plotted against a horizontal timeline of approximate ages. Using this horizontal timeline vs. vertical anatomical axis graph, color-coded areas were created within the chart to indicate both appearance and closure times of the major physes and ossification centers. This allows for applications in both clinical and veterinary forensic science settings since the two differing axes can be used separately (depending on the available information) or together to narrow down the most accurate age of the animal in question. The validation was not breed specific, which led to some variation within the time frames indicated in the tables. In particular, larger dogs tended to take longer for full ossification to occur whereas smaller animals—both canine and feline—experienced compete ossification sooner than their larger counterparts.

Performing the Forensic Necropsy

The forensic necropsy is done to facilitate a legal investigation, and its scope and focus are often different than a traditional diagnostic necropsy performed on clinical cases of natural death. In the case of a forensic necropsy, the examination and documentation are being prepared for law enforcement and the court. Examination procedures should follow best practices for evidence handling and documentation. The pathologist must be well prepared to testify to her or his findings and conclusions in court. The forensic necropsy should not, however, be regarded with fear. This chapter will review the forensic necropsy procedure, highlighting areas in which it might differ from the routine diagnostic necropsy. Ancillary techniques such as imaging studies, alternate light source examination, and skeletal preparation are also discussed. Finally, proper evidence handling and trace evidence collection techniques are outlined.

Postmortem Changes and Estimating the Postmortem Interval

Knowledge of the postmortem chemical and physical processes and the factors that affect them will permit the accurate interpretation of gross and microscopic pathology at necropsy and aid in the estimation of the postmortem interval (PMI). Estimation of the PMI is important in many human and animal death investigations; however, the accuracy in estimation of the time of death has not significantly improved after decades of research. Currently, no single method can be reliably used to accurately estimate the time of death. The investigator should exercise caution when formulating such an estimate, for it is dependent upon multiple circumstantial and environmental factors, and the accuracy and precision of the estimate decrease as the actual PMI increases. Much insight has been gained through studies of human decomposition; however, the veterinary pathologist must use care when attempting to extrapolate data and apply formulas designed for use in humans. Although only several of these methods are currently practical for application in casework, it is expected that future research will result in improved techniques with enhanced accuracy in the estimation of the PMI.