Victor F. Nettles

The effect of dietary aflatoxin on wild turkey poults.

Aflatoxins, toxic metabolites of Aspergillus flavus or Aspergillus parasiticus, cause poor feed utilization, decreased weight gains, depressed immune function, liver dysfunction, coagulation abnormalities, and death in a wide variety of species including humans. Conservationists have become concerned that increasingly popular wildlife feeding or baiting practices could expose wildlife to toxic amounts of aflatoxin-contaminated grains. In particular, the effects of aflatoxins on the wild turkey (Meleagris gallopova silvestris) are of concern because the conspecific domestic turkey is highly susceptible to aflatoxins. To evaluate the effect of dietary aflatoxin on wild turkeys, four groups of 4-mo-old wild turkeys were fed diets containing either 0, 100, 200, or 400 μg aflatoxin/kg feed for 2 wk in September and October 1996. Aflatoxin-fed poults had decreased feed consumption and weight gains as compared with control poults. Decreased liver-to-body weight ratios, liver enzyme alterations, slightly altered blood coagulation patterns, and mild histologic changes indicated low-level liver damage. Compromise of cell-mediated immunity was indicated by decreased lymphoblast transformation. The effects were apparent in all treatment groups to variable levels, but significant differences most often were found at 400 μg aflatoxin/kg feed. This study shows that short-term aflatoxin ingestion by wild turkeys can induce undesirable physiologic changes; therefore, exposure of wild turkeys to feeds containing aflatoxin levels of 100 μg aflatoxin/kg feed or more should be avoided.

DISEASES DIAGNOSED IN GRAY FOXES (UROCYON CINEREOARGENTEUS) FROM THE SOUTHEASTERN UNITED STATES

Diagnostic findings were reviewed on 157 sick or dead gray foxes (Urocyon cinereoar-genteus) from the southeastern United States examined during the period 1972 through 1989. Most foxes (n = 118) originated from Georgia; fewer animals were from Florida, Kentucky, Maryland, Mississippi, North Carolina, South Carolina, Tennessee, Virginia and West Virginia. Etiologic diagnoses included canine distemper (n = 125), congenital absence of guard hairs (n = 7), traumatic injuries (n = 7), rabies (n = 3), suspected toxicoses (n = 3), verminous pneumonia due to Paragonimus kellicotti (n = 1), bacterial septicemia secondary to Dracunculus insignis (n = 1), and tick paralysis (n = 1). Concurrent toxoplasmosis or cryptosporidiosis was noted in six and three foxes with canine distemper, respectively. Only lesion diagnoses were attainable for three foxes, and six cases were classified as undetermined. Canine distemper was diagnosed in 78% of the foxes, was geographically widespread, was detected in 16 of 18 yr, and exhibited a seasonal pattern of occurrence. These facts indicate that canine distemper is more significant as a mortality factor for gray foxes than all other infectious and noninfectious diseases combined.

Acceptance of Simulated Oral Rabies Vaccine Baits by Urban Raccoons

In summer 1986, a study was conducted to evaluate raccoon (Procyon lotor) acceptance of oral baits that could be used for rabies vaccination. One thousand wax-coated sponge bait cubes were filled with 5 mg of a seromarker (iophenoxic acid), placed in polyethylene bags, and hand-distributed in an 80 ha area within an urban National Park in Washington, D.C. (USA). After 3 wk, target and nontarget animals were trapped and blood samples collected to evaluate bait uptake. Thirty-three of 52 (63%) raccoons had elevated blood iodine levels indicating they had eaten at least one bait, 13 (25%) were negative, and six (12%) had marginal values. These results indicate that sponge baits hand-placed at a density of 12.4/ha can reach a significant proportion of an urban raccoon population. Implications for oral rabies vaccination of raccoons are discussed.

STUDIES ON ENDOPARASITES OF THE BLACK BEAR (Ursus americanus) IN THE SOUTHEASTERN UNITED STATES 1

Examination of 53 black bears (Ursus americanus) from six states in the southeastern United States revealed at least 17 species of endoparasites, including Sarcocystis sp., Spirometra mansonoides (spargana), Macracanthorhynchus ingens, Ancylostoma caninum, Arthrocephalus lotoris, Baylisascaris transfuga, Capillaria aerophila, Capillaria putorii, Crenosoma sp., Cyathospirura sp., Dirofilaria immitis, Gnathostoma sp., Gongylonema pulchrum, microfilariae, Molineus barbatus, Physaloptera sp. and Strongyloides sp. Twelve of these represent new host records for black bear, and two are considered to be new species. Data are presented on prevalence, intensity and geographic distribution of each species. Pathologic effects were associated with infections of spargana of S. mansonoides and adults of C. aerophilia.

RESPONSES OF RED FOXES TO FIRST AND SECOND INFECTION WITHSARCOPTES SCABIEI

The clinical response of red foxes (Vulpes vulpes) to the mange mite, Sarcoptes scabiei, was characterized by infection of five, 4-mo-old red foxes with S. scabieioriginally isolated from a wild red fox. The infected foxes and three uninfected control foxes were monitored with weekly complete blood counts and biweekly serum chemistry profiles, hypersensitivity tests, and evaluation of skin biopsies. After 7 wk, the foxes were treated and held free of infection for 2 mo. Six foxes, three previously infected and three with no history of exposure, were then infected with the same isolate of S. scabiei and followed for another 7 wk; two additional previously infected foxes were held as treatment controls, and two foxes with no history of exposure as naive controls. All infected foxes developed significant immediate (Type I) hypersensitivity reactions to a S. scabiei mite extract within 2 wk of exposure and maintained this reaction as long as 4 mo after clearance of mites. Pronounced mast cell hyperplasia and infiltration with eosinophils were the earliest inflammatory cell responses noted in biopsy samples from infected foxes and were maintained throughout infection. Infected foxes also showed significant increases in white blood cell counts, due primarily to increases in numbers of circulating neutrophils and eosinophils. Clinical response, severity of disease, and relative numbers of mites per cm2 of skin of previously infected foxes and foxes undergoing their first infection did not differ. These results show that red foxes develop strong immediate hypersensitivity reactions to S. scabieibut, under our experimental conditions, did not exhibit resistance to reinfection.

HOST DEFENSE RESPONSES ASSOCIATED WITH EXPERIMENTAL HEMORRHAGIC DISEASE IN WHITE-TAILED DEER

Our objectives were to examine the immunity conferred by epizootic hemorrhagic disease virus serotype 2 (EHDV-2) infection in white-tailed deer (Odocoileus virginianus) and determine if this immunity was protective during challenge with homologous (EHDV-2) or heterologous (bluetongue virus serotype 10; BTV-10) virus. Trials were conducted in the fall of 1992 and 1993. In the first experiment, naive white-tailed deer were infected intradermally and subcutaneously with EHDV-2 and monitored via physical examinations, complete blood counts, a and P interferon (IFN) assays, viral isolation, and serology. Infected deer had a wide range of clinical signs in response to infection. Eleven of the 16 deer had body temperature elevations ≥0.5 C between post-infection day (PID) 4 and 8. Infected deer had decreased lymphocyte counts between PID 6 and 10 that returned to normal levels by PID 17. Severely lymphopenic animals had the most severe clinical signs; five of 10 deer with lymphocyte counts less than 1000 cells/μl succumbed to the infection. Viremia was detected in all 16 EHDV-2 infected animals by PID 4, and peak viremias occurred between PID 4 and PID 10. Three deer remained viremic until PID 56, the study endpoint. Interferon was first detected between PID 2 and 6. Peak α and β IFN levels coincided with peak viremia in 11 deer. Precipitating and neutralizing antibodies were detected in infected deer by PID 10. In the second experiment, convalescent deer were challenged subcutaneously and intradermally with either EHDV-2 or BTV-10 and similarly monitored. Virus was detected in the blood of all four deer challenged with BTV-10, but viremia was not detected in three EHDV-2-challenged deer. Temperature fluctuations, blood cell parameter changes, and IFN and antibody responses seen in BTV-10-challenged deer were similar to those seen in the initial experiment. Deer challenged with EHDV-2 had mildly increased temperatures, but minimal IFN response and lymphocyte alterations.

HELMINTH PARASITES OF TRANSLOCATED RACCOONS (Procyon lotor) IN THE SOUTHEASTERN UNITED STATES1

Raccoons (Procyon lotor) typical of animals released by private hunting clubs in the Appalachian Mountains were examined for helminth parasites to evaluate the influence raccoon translocation might have on parasitic diseases. Results were compared with data from resident raccoons from characteristic release areas. Translocated raccoons harbored 19 helminth species that were exotic to resident animals. Most of these exotic parasites were trematodes (74%). An additional 19 species were found in both translocated and resident raccoons, and another 5 species were present only in residents. Three of the 19 exotic helminth parasites and 10 of the 19 enzootic species found in translocated raccoons are known to have some degree of pathogenicity to raccoons, other wildlife, domestic animals or man. At present, disease risks associated with the helminth parasites of these translocated raccoons were not considered alarmingly high; however, potential problems that could not be discounted were artificial intensification of undesirable enzootic parasites on release sites or expression of pathogenicity by exotic parasites presently considered nonsignificant.

MORBIDITY AND MORTALITY FACTORS IN KEY DEER (ODOCOILEUS VIRGINIANUS CLAVIUM)

The population health of endangered Key deer (Odocoileus virginianus clavium) was monitored from 10 February 1986 to 28 September 2000 by necropsy of animals that were killed by vehicles, euthanized because of terminal injuries or disease conditions, or found dead. The predominant mortality factor during the period was collision with motor vehicles; however, several infectious diseases were diagnosed, including infections with Arcanobacterium pyogenes, Haemonchus contortus, Salmonella spp., and Mycobacterium avium subsp. paratuberculosis. During the period monitored, the only infectious disease that was thought to have affected population dynamics was haemonchosis. Nevertheless, several of the observed diseases have potential to impact viability of the Key deer population under appropriate environmental conditions.

EPIZOOTIC HEMORRHAGIC DISEASE VIRUS AND BLUETONGUE VIRUS SEROTYPE DISTRIBUTION IN WHITE-TAILED DEER IN GEORGIA

Serum samples collected from 1,396 white-tailed deer (Odocoileus virginianus) in five areas of Georgia (USA) from 1989 to 1991 were tested for precipitating and serum neutralizing (SN) antibodies to the enzootic North American epizootic hemorrhagic disease virus (EHDV) and bluetongue virus (BTV) serotypes. Precipitating antibodies to the EHDV or BTV serogroups, as detected by agar gel immunodiffusion (AGID) tests, were present in 35%, 29%, and 39% of deer sampled in 1989, 1990, and 1991, respectively. Significant differences (P < 0.05) in precipitating antibody prevalence were detected between physiographic regions during all years. Antibody prevalence consistently was highest in deer sampled from the Coastal Plain (77%), followed by the Piedmont (33%), Ridge and Valley (29%), Barrier Island (5%), and Blue Ridge (2%) regions. All AGID-positive samples were tested by SN tests for antibodies against all North American EHDV and BTV serotypes (EHDV serotypes 1 and 2, BTV serotypes 2, 10, 11, 13, and 17). Criteria for previous exposure to a specific serotype were either detection of monospecific results or clusters of positive results against that serotype. Serologic evidence of previous exposure to EHDV serotypes 1 and 2, and BTV serotypes 11 and 13 was detected during all years. Predominant serotypes varied among years. In general, evidence of exposure to EHDV serotype 2 appeared annually while exposure to BTV serotype 13 and EHDV serotype 1 decreased and increased, respectively. To determine serotype diversity prior to 1989, 134 AGID-positive white-tailed deer serum samples collected from 1967 to 1988 also were tested by SN. Evidence of exposure to EHDV serotypes 1 and 2 and BTV serotypes 11, 13, and 17 was detected.

Paratuberculosis in key deer (Odocoileus virginianus clavium).

Paratuberculosis was diagnosed in an endangered Key deer (Odocoileus virginianus clavium) in November 1996. Between 10 April 1997 and 28 September 2000, the Key deer population was monitored for infection with Mycobacterium avium subsp. paratuberculosis by necropsy of available carcasses (n = 170), fecal cultures, and serology. One additional clinically affected Key deer was discovered in July 1998, and M. avium subsp. paratuberculosis was cultured from the feces of one live, asymptomatic deer. The results of this study provided sufficient evidence to consider the Key deer herd infected with M. avium subsp. paratuberculosis at very low prevalence.