Although the foundation of Koch's postulates, that “if an agent is the cause of disease in one individual it should be capable of causing disease in a second individual,” is basically sound, the ritual that has evolved into present day experimental studies has obscured almost completely what occurs in natural processes outside the laboratory. Through a series of examples, it is emphasized that just bringing the host and the parasite together is not enough, but that the circumstances under which this is done is equally important. These circumstances include: the prior history of the host; the host's behavioral patterns, environmental conditioning, and disease history; the circumstances of exposure; and the environmental factors related to the host and the parasite. Of equal importance is the individual variation (genetic, physiologic, immunologic, etc.) of the host and the individual variation (strains, immunogenicity, pathogenicity, virulence, etc.) of the parasite. Because the rigor of the present day “scientific method” demands clearcut and reproducible results and investigations require predictable performance of the parasite in an evenly maintained host that is in a highly constrained environment, we should not wonder why we cannot produce the events of nature. If we are going to understand diseases of wildlife, we must consider the genetic heterogenicity of the host and parasite population, and recognize the complexity of the environment in which both exist. Koch's postulates, in the narrow sense, will help us to identify parasitisms but will not provide us with an understanding of information about diseases in wildlife; the real significance of these parasitisms to the health of the individual and to the size of the population. If the most significant effect of disease on a wildlife population is not the fairly rare and isolated catastrophic epizootic, but the less dramatic although more significant effects on survival of juveniles and reproduction, then our methods must move away from the idea of the pathogen and host as fixed entities reacting solely to each other. Only by examining the concepts of host and pathogen populations interacting in a varying environment can the real role of disease in wildlife populations be defined and understood.

Periodontal lesions were present in 26 of 107 feral pigs (Sus scrofa) that were shot in southern Queensland. The severity of the lesions varied from gingivitis to extensive destruction of the alveolus and its contents. Examination of slaughtered domestic pigs revealed a similar prevalence of lesions (12 of 52). Only cheek teeth were affected, and molars were affected more frequently than premolars. In both feral and domestic pigs, prevalence of periodontal disease affecting bone increased with age. Although periodontal disease is recognized as a common and often serious problem in many mammalian species, both domestic and wild, it has rarely been recorded in the pig. It is considered that the most severe lesions would have interfered with mastication but that the contribution of the disease to mortality of feral pigs in Australia is probably not great.

Sixteen raptors, including one eagle, two falcons, five hawks and eight owls, were found to have developmental ocular lesions. The most common lesion was microphthalmia. Other findings included cataract, microphakia, retinal dysplasia, malformation of the ciliary body, choroid and pecten, and lentoid formation. Specific causes for these lesions could not be determined. It is hypothesized that developmental ocular disease probably is more common than available reports indicate.

Endogenous lipid pneumonia was present in 19 of 27 opossums (Didelphis virginiana) trapped in the vicinity of Baton Rouge, Louisiana. The severity of lesions varied from small pleural and subpleural aggregates of foamy macrophages with minimal disruption of pulmonary architecture to large nodular accumulations of foam cells with cholesterol clefts and localized emphysema. The cause of the lipid pneumonia may be related to pulmonary nematode parasite infections, which were evident in 13 of the affected animals.

Normal values and ranges for 31 clinical hematology and serum chemistry tests are reported for the beluga or white whale (Delphinapterus leucas). The values were collected over a 6-yr period from eight belugas maintained for display at Sea World (San Diego, California, USA) facilities and represent long-term evaluations for each animal in a controlled environment. They represent the first report for a number of serum chemistry values for the beluga. Normal values such as these provide an important data base from which to detect diagnostically important changes in health status for belugas in a zoological setting. They also establish a baseline from which to evaluate differences in normal values in free-ranging belugas and from which to diagnose disease problems in wild populations.

Between January 1984 and May 1987, blood samples were collected from 12 young (3- to 6-mo-old) Hawaiian monk seals (Monachus schauinslandi) that were captured in the wild and held in captivity. All samples evaluated were from clinically normal animals. Average hematologic and serum chemistry values were not remarkable for a young diving mammal. The blood and serum analyses performed established reference ranges, which can be used as indicators of health status for this endangered species.

Blood was collected from 486 feral horses of mixed sex and age classes captured from three wild horse management areas in Nevada and Oregon from December 1985 to February 1986. Males were significantly outnumbered by females in the Flanigan area, but both sexes were represented in approximately equal numbers in the Wassuk and Beaty's Butte areas. Hematology and chemistry values averaged 16.4 ± 0.11, 46.3 ± 0.28, 9.9 ± 0.07, 6.9 ± 0.10, 47.1 ± 0.24, 16.6 ± 0.09, 35.2 ± 0.09, 10.4 ± 0.14 and 23.4 ± 0.25 for hemoglobin (HGB), hematocrit (HCT), red blood cells (RBC), white blood cells (WBC), mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH), mean corpuscular hemoglobin concentration (MCHC), Cortisol (F) and serum urea nitrogen (SUN), respectively. Statistically significant differences in HGB, HCT, RBC, WBC, MCV and MCH levels occurred with respect to age (P ≤ 0.001). Serum F levels were lower in immature animals than in either subadult or adults in all areas. Flanigan horses appeared in the poorest condition and had the lowest HGB, HCT and RBC counts while the values for Wassuk horses were significantly higher (P ≤ 0.001). Serum F levels were lowest in the Flanigan horses. A significantly lower (P ≤ 0.001) proportion of adult mares had progesterone levels consistent with pregnancy in the Flanigan horses versus those from the other two areas. These data are consistent with a subjective evaluation of the condition of the horses.

Mallard (Anas platyrhynchos) ducklings (2 wk old) were given water from natural saline wetlands or fresh water as drinking water for 1 or 2 wk prior to, and after, receiving material containing Clostridium botulinum type C toxin. Water with conductivity ranging from 3,460 to 6,690 μmhos/cm had no detectable effect on the occurrence or severity of clinical signs of botulism. Ducks drinking water with conductivity of 7,130 μmhos/cm for 1 wk prior to receiving toxin had more severe clinical signs and greater mortality than did birds drinking fresh water. Ducks given the same water for 2 wk prior to receiving toxin did not differ from the controls in response to toxin. Fewer ducks in groups drinking the most saline water tested (conductivity = 13,500 μmhos/cm) had clinical signs of botulism than in groups drinking fresh water.

We describe an indirect enzyme-linked immunosorbent assay (ELISA) that utilizes anticanine immunoglobulin for the measurement of rabies-specific antibody in the sera of the major domestic and wildlife reservoirs of rabies in North America. Sufficient cross-reactivity was found to exist between anticanine IgG and serum antibody from all carnivores tested, including dogs, cats, foxes (Vulpes vulpes), skunks (Mephitis sp.) and raccoons (Procyon lotor). With sera of most species, good correlation was observed between results obtained with the ELISA and with the fluorescence inhibition microtest (FIMT). Some wildlife specimens, particularly of skunk and raccoon origin, were cytotoxic in the FIMT, resulting in possible false-positive reactions. In view of this, and since the ELISA is rapid, economical and reproducible (coefficient of variation < 13%), we consider it to be a favorable alternative to the fluorescence inhibition test for assay of wildlife sera.

The IDEIA Chlamydia Test, a commercially available antigen-capture enzyme-linked immunosorbent assay (ELISA) test, based on a monoclonal antibody for the detection of chlamydia in clinical specimens, was evaluated in a population of 65 free-ranging koalas in southeastern Queensland determined to be infected with Chlamydia psittaci. Compared to isolation of the organism in tissue culture, the sensitivity of the IDEIA test ranged from 3 to 11%, and the specificity from 90 to 97%. The results indicated that the IDEIA test is unsuitable for use as a diagnostic screening test for C. psittaci in free-ranging koalas.

Fifty-three newly captive birds of prey were tested serologically for neutralizing antibodies against rabies virus, using a fluorescent focus inhibition test. No significant antibody titers were detected with this sensitive and specific technique in any of these birds. This study supports the contention that free-ranging birds of prey are of limited importance in the epidemiology of rabies.

The presence of antibodies against bovine herpesvirus 1 (BHV-1), bovid herpesvirus 6 (BHV-6), herpesvirus of Cervidae type 1 (HVC-1), reindeer herpesvirus, bovine herpesvirus 2 (BHV-2) and bovid herpesvirus 4 (BHV-4) was investigated in wild ruminants of France and Belgium between 1981 and 1986. There were no animals serologically positive for BHV-4. Antibodies against BHV-2 were demonstrated in roe deer (Cervus capreolus) (<1%) and chamois (Rupicapra rupicapra) (1%) in France. Animals seropositive to the four related viruses (BHV-1, BHV-6, HVC-1, reindeer herpesvirus) were detected in red deer (Cervus elaphus) in France and Belgium (1% and 11%, respectively), in roe deer (<1%) from France, in chamois (4%) in France and in ibex (Capra ibex) (4%) from France. The presence of antibodies against HVC-1, especially in red deer from Belgium, may suggest that wild ruminants in continental Europe are now infected with this virus, which previously has been isolated only in Scotland.

Blood from endangered San Joaquin kit foxes (Vulpes macrotis mutica) inhabiting the Elk Hills Naval Petroleum Reserve, Kern County, and the Elkhorn Plain, San Luis Obispo County, California, was collected in 1981, 1982 and 1984 and sera were tested for antibodies against 10 selected pathogens. Proportions of kit fox sera containing antibodies against pathogens were: canine parvovirus, 100% in 1981–1982 and 67% in 1984; infectious canine hepatitis virus, 6% in 1981–1982 and 21% in 1984; canine distemper virus, none in 1981–1982 and 14% in 1984; Francisella tularensis, 8% in 1981–1982 and 31% in 1984; Brucella abortus, 8% in 1981–1982 and 3% in 1984; Brucella canis, 14% in 1981–1982 and none in 1984; Toxoplasma gondii, 6% in 1981–1982; Coccidioides immitis, 3% in 1981–1982; and Yersinia pestis and Leptospira interrogans serotypes canicola, grippotyphosa, hardjo, icterohaemorrhagiae, and pomona, none in 1981–1982. Although antibodies against selected pathogens were present, no clinical indications of disease were observed in these fox populations.

A population of free-ranging koalas in southeastern Queensland was examined to determine the prevalence of Chlamydia psittaci infections. Although C. psittaci was isolated from 46 of 65 (71%) koalas studied, only six (9%) of these had clinical signs of disease. Most adult females (82%) had back or pouch young present even though 67% of them were infected. There were no significant correlations between age, sex or site of sampling (urogenital versus conjunctival tissues) and the isolation of C. psittaci. No other important bacterial or fungal pathogens were isolated. The complement fixation test had a sensitivity of 7% and a specificity of 94% in detecting chlamydial infections, suggesting that it is unsuitable for use as a screening test. Chlamydia psittaci infection within this population appeared to represent a generally well-balanced host-parasite relationship and few animals had clinical signs of disease. Only four of 27 (15%) healthy koalas infected with C. psittaci followed for 24 wk after sampling developed eye disease or “dirty tail.” Two koalas with keratoconjunctivitis recovered without treatment during the study period. Additional factors, including the stresses imposed by loss of habitat, may act to produce overt disease in koalas with latent C. psittaci infections.

A seasonal survey of skin tumor prevalence in walleyes (Stizostedion vitreum) was conducted during the ice-free period on Oneida Lake, New York in 1986. During the survey, 1,028 walleyes were collected and examined for the presence of lymphocystis disease, dermal sarcoma, discrete epidermal hyperplasia and diffuse epidermal hyperplasia. Skin growths were high in prevalence in early spring, low in prevalence during the summer, and again high in prevalence in the fall. Lymphocystis disease and dermal sarcoma were more frequently observed than either discrete or diffuse epidermal hyperplasia. Histologically, a moderate to severe inflammatory response was associated with dermal sarcoma in the early spring and late spring but not in the fall. Regardless of the time of year, varying degrees of inflammatory response were seen associated with lymphocystis disease. Samples were inadequate to assess seasonal trends in incidence of discrete and diffuse epidermal hyperplasia.

We determined the prevalence of six genera of bacteria from a sample of 387 cloacal swabs from 364 passerines and woodpeckers. The prevalence of bacteria were as follows: Escherichia coli (1%), Pseudomonas spp. (22%), Salmonella spp. (0%), Staphylococcus spp. (15%), Streptococcus spp. (18%), and Yersinia spp. (1%). The prevalence of Streptococcus spp. was higher in omnivorous species than in granivorous species (20% versus 8%). Individuals captured at feeders had a lower prevalence of both Streptococcus spp. (15% versus 33%) and Escherichia coli (0.5% versus 4%) than birds that did not have access to feeders. These differences are probably not due to the feeder per se, but instead to other site related differences. The prevalence of bacteria did not differ between male and female black-capped chickadees, Parus atricapillus. For 279 color marked black-capped chickadees, we calculated the cumulative mortality rate during 12 wk following swabbing. Although the cumulative mortality rates of infected birds were consistently higher than the rates of non-infected birds, none of these differences were significant. Infections may cause slight reductions in survival rates, but we were not able to confirm this with our data.

The prevalence of antibodies to Brucella spp., Mycobacterium paratuberculosis and the Mycoplasma spp. causing contagious bovine pleuropneumonia and contagious caprine pleuropneumonia was determined in various species of ruminants on a ranch in the semi-arid zone of southeastern Kenya. Antibody titers to Brucella spp. were found in eland (Taurotragus oryx), oryx (Oryx beisa) and camels (Camelus dromedarius). Reactors were not found in buffalo (Syncerus caffer), sheep (Ovis aries) and goats (Capra hircus). Brucella sp. was not isolated from eland and camels. Antibody titers to M. paratuberculosis were found only in camels and goats. Mycobacteria were not detected in feces of two serologically positive camels. Significant serum antibody titers to Mycoplasma mycoides mycoides were found only in camels. Antibody titers to Mycoplasma sp. (strain F38), which causes contagious caprine pleuropneumonia, were found in buffalo, cattle and camels but not in the other species. Attempts to isolate the Mycoplasma sp. from nasal secretion of the buffalo and camels failed. The possible occurrence of tuberculosis in camels is discussed. Under the conditions at the ranch, contagious bacterial diseases appear to be of minor importance in the domesticated wild herbivores. The introduced camels, however, might be a source of various infections such as brucellosis, mycoplasmosis and possibly tuberculosis for the other susceptible species.

This study documents glycosuria effects of xylazine and ketamine in eight captive and 19 free-ranging white-tailed deer (Odocoileus virginianus) from January to April 1985. Mean urinary glucose: creatinine ratios in two groups of deer fed high protein-high energy and low protein-low energy diets and in free-ranging deer were 1,000, 719, and 259, respectively. Glucose did not occur in urine of deer immobilized by physical restraint. Glucose: creatinine increased with the time interval between xylazine injection and urine collection in the two groups of captive deer.

Five red-tailed hawks (Buteo jamaicensis) were anesthetized at weekly intervals with intravenous ketamine hydrochloride (KET, 4.4 mg/kg) and xylazine hydrochloride (XYL, 2.2 mg/kg). Twenty min after anesthesia, yohimbine hydrochloride (YOH, 0.05, 0.10, 0.20 and 0.40 mg/kg) or a control was administered. All doses of YOH significantly reduced the head-up times (F = 20.84, df = 1,24, P < 0.0001) and the standing times (F = 12.30, df = 1.24, P < 0.0001), compared to the control group. The heart and respiratory rates following YOH (all doses) were significantly greater (P < 0.01) than the anesthetized rates, but were comparable to the rates observed in restrained, unanesthetized hawks. Yohimbine did not appear to have any significant effect on body temperature. Based upon administration of 4.4 mg/kg KET and 2.2 mg/kg XYL, a dose of 0.10 mg/kg YOH was recommended to achieve antagonism without causing profound cardiovascular or respiratory changes.

The laboratory-born progeny from two geographically distant populations of northern grasshopper mice (Onychomys leucogaster) were challenged with Yersinia pestis to determine their relative susceptibilities to plague. One of the O. leucogaster populations was associated with a known epizootic focus of the disease and was found to be nearly 2,000 times more resistant to mortality than were members of another population from an area historically free of plague. The ecology and omnivorous behavior of O. leucogaster appears to promote strong selection for resistance to plague in areas where they are naturally exposed.

Leptospires were isolated from the kidneys of four of 211 toads (Bufo marinus) caught on Barbados. Two of the isolates were identified as Leptospira interrogans serovar bim in the Autumnalis serogroup (the most common cause of leptospiral illness on Barbados), and two as possibly new serovars in the Australis serogroup. Sera from 198 of the toads were examined by the leptospire microscopic agglutination test. Forty-two (21%) were positive at titers of ≥ 1:100, and 54 (27%) at ≥1:50. The predominating serogroups were Australis (50%), Autumnalis (23%) and Panama (13%). The agglutination tests on the culture-positive toads showed that serologic studies alone may be of limited value in these animals. Bufo marinus can harbor pathogenic leptospires, and it may be a significant source of the Autumnalis serogroup infections in the Caribbean.

Body masses of 3,739 birds representing immature and adult males and females of 15 species of passeriforms (both uninfected and infected with Haemoproteus spp. and Leucocytozoon spp.) were compared. There was some interaction among year, month and area of capture for several host species, but there was no discernible effect of either parasite genus on body mass. There were no effects due to high intensity parasitemia for eight host species examined. Either parasitism does not cause loss of body mass, or the techniques used were too insensitive to separate effects of parasitism from other natural causes.

Hepatozoon sp. is described for the first time in foxes (Vulpes vulpes silacea) in Portugal. Of 301 foxes examined, 143 (48%) were infected. The gametocyte was the predominant stage of the life cycle and was found in every organ except the bone marrow, where schizonts were the most abundant stage. The morphological similarity of this parasite's gametocytes to Hepatozoon canis is emphasized.

From 1981 through 1986, plasma or serum samples were obtained from 322 wild turkeys (Meleagris gallopavo) from Georgia (n = 111), Kentucky (n = 21), Louisiana (n = 22), North Carolina (n = 118), Tennessee (n = 19), Missouri (n = 24) and Iowa (n = 7). These samples were tested for antibodies to Mycoplasma gallisepticum (MG) and in most instances, M. synoviae (MS), M. meleagridis (MM), and avian influenza (AI) virus. All 322 turkeys were seronegative for MG by the rapid plate agglutination (RPA) test. All of a subsample (n = 147) also were negative (titer ≤ 1:40) for MG by the hemagglutination inhibition (HI) test. Five of 253 turkeys (2%) were seropositive ( 4 reaction) for MS by the RPA test; however, HI tests for MS on these five turkeys were negative as were attempts to isolate MS from trachea and homogenized lung tissue. Three of 253 turkeys (1%) were seropositive ( 1 to 3 reactions) for MM by the RPA test. None of 210 turkeys had antibodies to AI by the agar gel precipitation test. These data suggest that populations of native eastern wild turkeys are not important in the epizootiology of MG, MS, MM, or AI.

A serologic survey of 60 eastern cottontail rabbits (Sylvilagus floridanus) from three counties in Pennsylvania was conducted in March 1983. Serum antibody prevalences for Herpesvirus sylvilagus and La Crosse virus (California serogroup) were <4%. There was no evidence of previous exposure to either Jamestown Canyon or snowshoe hare viruses (California serogroup). Antibody to trivittatus virus (California serogroup) was found in 60% of the 20 cottontails from York County. No cottontails had antibodies to Bacillus piliformis, the etiologic agent of Tyzzer's disease.

Five Rocky Mountain bighorn sheep (Ovis canadensis canadensis), approximately 5 mo old and without detectable antibody titers to respiratory syncytial virus (RSV), were assigned to two groups to study the effects of RSV challenge inoculation in vaccinated (n = 3) and unvaccinated (n = 2) bighorns. The three lambs vaccinated with a modified live bovine RSV vaccine developed a detectable antibody response to the vaccine. Vaccinated and unvaccinated lambs challenged with an ovine isolate of RSV developed increased levels of neutralizing antibody, but clinical signs of disease were not observed. Neutralizing antibody titers to RSV remained higher (2–4-fold) in vaccinated lambs over time when compared to unvaccinated lambs.

Prevalences of poxvirus-like lesions were determined for 177 northern bobwhites (Colinus virginianus) and 24 scaled quail (Callipepla squamata) trapped in southern Texas from 1976 to 1979 and for 190 northern bob-whites and 105 scaled quail shot at five locations in southern Texas from 1980 to 1981. None of the northern bobwhites trapped in 1976–1977 was infected, but 54% of the trapped scaled quail were infected; 17% of the northern bob-whites and 34% of the scaled quail shot in 1980–1981 had pox lesions, primarily on the wings. Prevalence was unrelated to sex or age of birds. For both species, prevalence was greatest during late spring and early summer. Histologic and electron microscopic examination confirmed poxvirus in two scaled quail, which constituted the first report of poxvirus in this species.

The isolation and identification of the Gram-negative fish pathogen, Aeromonas salmonicida salmonicida, from masu salmon (Oncorhynchus masou) at the Yang Yang Salmon Hatchery in the Republic of Korea is described. The bacterium possessed certain characteristics in common with isolates from fish in Japan. It is an important cause of mortality among cultured salmonids in the Republic of Korea. This is the first report of this fish pathogen from the Asian mainland.

Blood, kidney and tick samples were obtained from 18 hunter-killed black bears (Ursus americanus) from three sites in northern Wisconsin. A Borrelia sp., morphologically and antigenically similar to Borrelia burgdorferi, was isolated from the blood of two of the animals, and from the kidney of a third. Ixodes dammini and Dermacentor variabilis were found on the bears. This is the first report of borreliosis in the Ursidae, and of the primary vector of Lyme disease, I. dammini, from this host.

From 1984 to 1986 110 white-tailed deer (Odocoileus virginianus) from Big Cypress National Preserve in southern Florida were examined for intestinal coccidial infections. Three species of Eimeria (E. mccordocki, E. madisonensis, and E. odocoilei) were found in low prevalences. There were no differences in prevalence due to age, sex, season of collection or specific locality within the Preserve.

Viscera of 16 moose and hide samples of 24 moose (Alces alces) shot in eastern Ontario in 1985 were examined for parasites. Two species of trematodes, one species of cestode, five species of nematodes and one species of tick were recovered. One nematode species, Trichuris discolor, is reported for the first time from moose. Our results suggest that the parasite fauna of the moose may have been influenced by the absence or scarcity of other species of wild cervids or carnivores and by the presence of domestic livestock.

Thirty-five desert cottontails (Sylvilagus audubonii) and 35 black-tailed jack rabbits (Lepus californicus), occurring sympatrically near the Clovis-Portales area of eastern New Mexico were infected with four species of Eucestoda (adults of Raillietina salmoni and Raillietina selfi, larvae of Taenia pisiformis and Taenia serialis). Raillietina salmoni and T. pisiformis more commonly infected S. audubonii. Raillietina selfi was found in near equal prevalence in both host species. Taenia serialis was recovered only from L. californicus. Thus, three of the four helminth species were shared by both lagomorphs (Jaccard's coefficient = 75). Female hosts were most heavily infected with R. selfi and Taenia serialis.

During a routine examination of a female Cooper's hawk (Accipiter cooperii) nematodes were found in the thoracic air sacs. A total of 12 females and nine males were recovered and identified as Serratospiculoides amaculata. This is the first record of this parasite found in a raptor, other than a falcon, in North America.

Ketamine hydrochloride was given orally at a dose of 200 mg/kg to six domestic turkeys (Meleagris gallapovo). There was no apparent anesthetic effect. The same birds received 500 mg/kg by the same route 1 wk later. All birds became ataxic within 10 min; although some sedation was apparent, they made coordinated escapes when challenged.