Scott D. Fitzgerald

Bovine Tuberculosis in Free-Ranging White-Tailed Deer From Michigan

A 4.5 yr-old male white-tailed deer (Odocoileus virginianus) killed by a hunter during the 1994 firearm hunting season in northeastern Michigan (USA) had lesions suggestive of tuberculosis and was positive on culture for Mycobacterium bovis the causative agent for bovine tuberculosis. Subsequently, a survey of 354 hunter-harvested white-tailed deer for tuberculosis was conducted in this area from 15 November 1995 through 5 January 1996. Heads and/or lungs from deer were examined grossly and microscopically for lesions suggestive of bovine tuberculosis. Gross lesions suggestive of tuberculosis were seen in 15 deer. Tissues from 16 deer had acid-fast bacilli on histological examination and in 12 cases mycobacterial isolates from lymph nodes and/or lungs were identified as M. bovis. In addition, lymph nodes from 12 deer (11 females and 1 male) without gross or microscopic lesions were pooled into 1 sample from which M. bovis was cultured. Although more male (9) than female (3) deer had bovine tuberculosis infections, this difference was not statistically significant. Mycobacterium bovis culture positive deer ranged in age from 1.5 to 5.5 yr with a mean of 2.7 yr (median 2.5 yr) for males and 3.2 yr (median 3.5 yr) for females. This appears to be the first epidemic occurrence of M. bovis in free-ranging cervids in North America. A combination of environmental (high deer density and poor quality habit) and management-related factors (extensive supplemental feeding) may be responsible for this epizootic.

Proposal of a 2-Tier Histologic Grading System for Canine Cutaneous Mast Cell Tumors to More Accurately Predict Biological Behavior

Currently, prognostic and therapeutic determinations for canine cutaneous mast cell tumors (MCTs) are primarily based on histologic grade. However, the use of different grading systems by veterinary pathologists and institutional modifications make the prognostic value of histologic grading highly questionable. To evaluate the consistency of microscopic grading among veterinary pathologists and the prognostic significance of the Patnaik grading system, 95 cutaneous MCTs from 95 dogs were graded in a blinded study by 28 veterinary pathologists from 16 institutions. Concordance among veterinary pathologists was 75% for the diagnosis of grade 3 MCTs and less than 64% for the diagnosis of grade 1 and 2 MCTs. To improve concordance among pathologists and to provide better prognostic significance, a 2-tier histologic grading system was devised. The diagnosis of high-grade MCTs is based on the presence of any one of the following criteria: at least 7 mitotic figures in 10 high-power fields (hpf); at least 3 multinucleated (3 or more nuclei) cells in 10 hpf; at least 3 bizarre nuclei in 10 hpf; karyomegaly (ie, nuclear diameters of at least 10% of neoplastic cells vary by at least two-fold). Fields with the highest mitotic activity or with the highest degree of anisokaryosis were selected to assess the different parameters. According to the novel grading system, high-grade MCTs were significantly associated with shorter time to metastasis or new tumor development, and with shorter survival time. The median survival time was less than 4 months for high-grade MCTs but more than 2 years for low-grade MCTs.

Epidemiology of Mycobacterium bovis in free-ranging white-tailed deer, Michigan, USA, 1995–2000

An endemic area of bovine tuberculosis (TB) (Mycobacterium bovis) currently affecting wild white-tailed deer (Odocoileus virginianus) in northern lower Michigan, USA, constitutes the first self-sustaining outbreak of the infection in free-ranging North American cervids. Given this precedent, epidemiologic insights gained from the outbreak afford the opportunity to guide not only current surveillance and intervention but also control efforts for future outbreaks involving wildlife reservoirs. Our specific objectives were to evaluate retrospective data from field surveillance conducted from 1995 to 2000 to determine apparent prevalence, trends in apparent prevalence, and the effects of various factors on the odds of being M. bovis positive. Data were gathered from post-mortem examinations of 62,560 wild deer collected from all 83 Michigan counties. Records of survey method, sex, age, geographic area and infection status as determined by mycobacterial culture were subjected to trend analysis and multivariable logistic regression. Apparent prevalence for the period was 0.54% (336/62,560) statewide. Prevalence varied widely with geographic area, but significantly decreased since 1995 in the core area of the outbreak-which coincided with implementation of control strategies. Significant risk factors were geographic area, sex, age, and the sex-by-age interaction. The survey method by which deer were obtained for testing was not a predictor of infection. Our results to date suggest an outbreak characterized by broad areas of very low prevalence surrounding focal areas where prevalence is sometimes orders-of-magnitude higher (e.g., deer originating from the core area were up to 147 times more likely to be TB positive than deer from other areas). Our results also identify older male deer as most likely to be M. bovis positive (OR=11.3, 95% CI 3.2, 40.3 for bucks > or =5 years vs. does < or =1.5 years)-an observation consistent with the biology and behavior of the species. Synthesizing these results with those of other ongoing investigations, we hypothesize a two-stage model of disease transmission where TB is maintained at very low prevalence in matriarchal groups, with primary dissemination of the disease attributable to the dispersal and movements of bucks (as well as to the large aggregations of animals created by human activities).

Effects of waterborne exposure of 17 β-estradiol on secondary sex characteristics and gonads of fathead minnows (Pimephales promelas)

Abstract Environmental contaminants with estrogenic activity have recently received attention because of their potential effects on the reproductive efficiency of humans and wildlife. This study was conducted with the endogenous estrogen, 17 β-estradiol (E2), to establish the histologic response of the fathead minnow (Pimephales promelas) as a model organism. Sexually mature fathead minnows were exposed for 14 days to waterborne concentrations of 1000, 100, 10, 2, 1, 0.5, 0.25, 0.125, 0.1 or 0.0625 nM E2. Exposure to E2 caused a reduction in size of the prominent male secondary sex characteristics, the fatpads and nuptial breeding tubercles. Histological lesions observed in the testes included proliferation of Sertoli cells and degenerative changes. Electron microscopy of seminiferous tubules and their Sertoli cells revealed large phagolysosomes filled with degenerating spermatozoa and other cellular debris. Females had ovaries in which most of the follicles were in the primary stage of development. There were also more atretic follicles and fewer secondary and Graafian follicles than in unexposed females. These findings demonstrate components of sexually mature fish which may be altered by compounds that mimic E2. To determine if lesions observed in males were permanent, 50 sexually mature males and females were exposed to a single concentration of 10 nM E2 for 10 days. Samples were collected from males on the final day of E2 exposure and over a period of 16 weeks after the exposure was stopped. No E2-induced lesions were observed beyond 16 weeks post E2 exposure. Results of these studies suggest that histological lesions could occur at ecologically-relevant exposures to ‘estrogenic’ compounds. However, certain lesions caused by exposure of adult fathead minnows are not permanent.

EVALUATION OF THE INFLUENCE OF SUPPLEMENTAL FEEDING OF WHITE-TAILED DEER (ODOCOILEUS VIRGINIANUS) ON THE PREVALENCE OF BOVINE TUBERCULOSIS IN THE MICHIGAN WILD DEER POPULATION

A retrospective study was conducted to test the hypothesis that supplemental feeding of white-tailed deer (Odocoileus virginianus) from 1995 to 1997 was associated with the prevalence of bovine tuberculosis (TB) in free-ranging deer in northeastern Michigan. Bovine TB prevalence data were obtained from an ongoing surveillance program, while data relating to supplemental feeding and other risk factors were collected via in-person interviews. A multivariable Poisson regression modeling approach was used to test the stated hypothesis while controlling for other risk factors. Of the 389 potential participants, 59% agreed to participate in the study. Results showed that supplemental feeding of deer was associated with bovine TB in white-tailed deer. Specific risk factors associated with increasing risk for bovine TB were locating feed sites in areas with high levels of hardwood forests (O.R.=1.8, 95% C.I.=1.3–2.4), other large-scale feeding sites in the area (O.R.=1.1, 95% C.I.=1.0–1.2), the number of deer fed per year (O.R.=3.9, 95% C.I.=1.4–11.4), the numbers of feed sites spreading grain (O.R.=14.7, 95% C.I.=2.2–98.9), the quantity of grains provided at the site (O.R.=1.4, 95% C. I.=1.1–1.7), and the quantity of fruits and vegetables provided (O.R.=1.4, 95% C.I.=1.2–1.7). Conversely, factors associated with decreasing risk of bovine TB were locating feed sites in areas with high levels of hardwood forests (O.R.=0.1, 95% C.I.=0.02–0.4), locating feed sites in forests (O.R.=0.05, 95% C.I.=0.01–0.4), and the level of sites providing grain (O.R.=0.1, 95% C.I.=0.01–0.3). The results of this study suggest that banning the practice of supplemental feeding is a valid policy for control of bovine tuberculosis in free-ranging white-tailed deer.

Bovine tuberculosis in free-ranging carnivores from Michigan

During a survey of carnivores and omnivores for bovine tuberculosis conducted in Michigan (USA) since 1996, Mycobacterium bovis was cultured from lymph nodes pooled from six coyotes (Canis latrans) (four adult female, two adult male), two adult male raccoons (Procyon lotor), one adult male red fox (Vulpes vulpes), and one 1.5-yr-old male black bear (Ursus americanus). One adult, male bobcat (Felis rufus) with histologic lesions suggestive of tuberculosis was negative on culture but positive for organisms belonging to the Mycobacterium tuberculosis complex when tested by polymerase chain reaction. All the tuberculous animals were taken from three adjoining counties where M. bovis is known to be endemic in the free-ranging white-tailed deer (Odocoileus virginianus) population. There were two coyotes, one raccoon, one red fox, and one bobcat infected in Alpena county. Montmorency County had two coyotes and one raccoon with M. bovis. Two coyotes and a bear were infected from Alcona County. These free-ranging carnivores/omnivores probably became infected with M. bovis through consumption of tuberculous deer. Other species included in the survey were opossum (Didelphis virginiana), gray fox (Urocyon cinereoargenteus), and badger (Taxidea taxus); these were negative for M. bovis.

Effects of air cell injection of perfluorooctane sulfonate before incubation on development of the white leghorn chicken (Gallus domesticus) embryo

Fifty white leghorn chicken (Gallus domesticus) eggs per group were injected with 0.1, 1.0, 10.0, or 20.0 microg perfluorooctane sulfonate (PFOS)/g egg before incubation to investigate the effects of PFOS on the developing embryo. Hatchlings were weighed, examined for gross developmental abnormalities, and transferred to a battery brooder, where they were raised for 7 d. Chicks were then weighed, and 20 birds per treatment were randomly chosen for necropsy. The brain, heart, kidneys, and liver were removed and weighed. Livers were processed further for determination of PFOS concentrations and histological assessment. Hatchability was reduced significantly in all treatment groups in a dose-dependent manner. The calculated median lethal dose was 4.9 microg PFOS/g egg. Perfluorooctane sulfonate did not affect posthatch body or organ weights. Exposure to PFOS caused pathological changes in the liver characterized by bile duct hyperplasia, periportal inflammation, and hepatic cell necrosis at doses as low as 1.0 microg PFOS/g egg. Perfluorooctane sulfonate concentrations in the liver increased in a dose-dependent manner. Based on reduced hatchability, the lowest-observed-adverse-effect level was 0.1 microg PFOS/g egg.

A Comprehensive Study of Easter Lily Poisoning in Cats

This study was conducted with 3 objectives in mind: first, to identify the toxic fraction (aqueous or organic) in leaves and flowers; second, to identify diagnostic marker(s) of toxicosis in cats; and, third, to evaluate the morphologic effects of intoxication. The study was conducted in 2 phases. Phase 1 was to identify which extract, organic or aqueous, was nephrotoxic and also to determine the appropriate dose for use in the phase 2 studies. Results indicated that only the aqueous extracts of leaves and flowers were nephrotoxic and pancreotoxic. To identify the proximate toxic compound, cats in the phase 2 study were orally exposed to subfractions of the aqueous flower extract, 1 subfraction per cat. Results confirmed vomiting, depression, polyuria, polydipsia, azotemia, glucosuria, proteinuria, and isosthenuria as toxic effects of the Easter lily plant. Another significant finding in serum was elevated creatinine kinase. Significant histologic kidney changes included acute necrosis of proximal convoluted tubules and degeneration of pancreatic acinar cells. Renal ultrastructural changes included swollen mitochondria, megamitochondria, edema, and lipidosis. Subfraction IIa3 of the aqueous floral extract contained most of the toxic compound(s). These studies reproduced the clinical disease, identified the most toxic fraction of the Easter lily, and helped characterize the clinical pathology, histopathology, and ultrastructural pathology associated with the disease.

Tuberculous lesions in free-ranging white-tailed deer in Michigan.

Descriptions of the anatomical distribution of Mycobacterium bovis gross lesions in large samples of white-tailed deer (Odocoileus virginianus) are lacking in the scientific literature. This report describes the distribution of gross lesions in the 58 white-tailed deer that cultured positive for M. bovis among the 19,500 submitted for tuberculosis testing in Michigan (USA) in 1999. For the vast majority (19,348) of those tested, only the head was submitted; for others, only extracranial tissues (33) or both the head and extracranial tissues (119) were available. Among those deer that cultured positive, cranial gross lesions were noted most frequently in the medial retropharyngeal lymph nodes, although solitary, unilateral parotid lymph node lesions also were found. Extracranial lesions occurred most commonly in the thorax. The distribution of lesions largely agreed with the few existing case reports of the M. bovis in white-tailed deer, although gross lesions were also found in sites apparently not previously reported in this species (liver, spleen, rumen, mammary gland). Some practical issues that may assist future surveillance and public education efforts are also discussed.

Wildlife Reservoirs of Bovine Tuberculosis Worldwide: Hosts, Pathology, Surveillance, and Control

Bovine tuberculosis due to Mycobacterium bovis is a zoonotic disease classically carried by cattle and spilling over into humans primarily by the ingestion of milk. However, in recent decades, there have been many endemic geographic localities where M. bovis has been detected infecting wildlife reservoirs, limiting the progress toward eradication of this disease from cattle. These include cervids in North America, badgers in Great Britain, feral pigs in Europe, brushtailed possums in New Zealand, and buffalo in South Africa. An overview of these wildlife hosts will provide insight into how these reservoirs maintain and spread the disease. In addition, the authors summarize the pathology, current ongoing methods for surveillance, and control. In many instances, it has proven to be more difficult to control or eradicate bovine tuberculosis in wild free-ranging species than in domesticated cattle. Furthermore, human influences have often contributed to the introduction and/or maintenance of the disease in wildlife species. Finally, some emerging themes regarding bovine tuberculosis establishment in wildlife hosts, as well as conclusions regarding management practices to assist in bovine tuberculosis control and eradication in wildlife, are offered.