Trichinella infection in wildlife of the southwestern United States.

Several potential mammalian reservoirs of sylvatic species of Trichinella were examined from Texas, New Mexico, and Arizona. During 1998-99, tongues were collected from a black bear (Ursus americanus) in Arizona; from 9 black bears, a coyote (Canis latrans), and a mountain lion (Felis concolor) in New Mexico; and from 154 coyotes, 32 raccoons (Procyon lotor), 13 opossums (Didelphis marsupialis), 4 ocelots (Leopardus pardalis), 3 bobcats (Lynx rufus), and 5 feral hogs (Sus scrofa) in southern Texas. Larvae of Trichinella murrelli were identified by a multiple-polymerase chain reaction analysis in 1 black bear (11.1%) from New Mexico and in 7 coyotes (4.5%) of Texas, whereas Trichinella spiralis larvae were detected in the black bear of Arizona. This is the first report of Trichinella infection in wildlife of New Mexico and Texas and extends the distribution of T. murrelli into the southwestern United States near the border of Mexico.

Detection of aflatoxin-contaminated grain by three granivorous bird species.

Supplemental feeding of game species and the use of backyard feeders to attract avian wildlife are common practices throughout the United States. However, these activities may expose wildlife to aflatoxins. We tested the hypothesis that wild birds would avoid consuming aflatoxin-contaminated feed. Individual northern bobwhites (Colinus virginianus), white-winged doves (Zenaida asiatica), and green jays (Cyanocorax yncas) were presented with feeders that had four compartments, which contained milo that was contaminated with aflatoxin levels of 0, 100, 500, and 1,000 microg/kg, respectively. Feed remaining was weighed at 6, 12, 18, 24, 36, 48, 60, and 72 hr after the initiation of the trial. White-winged doves and northern bobwhites did not avoid contaminated feed. However, green jays selected against aflatoxin-tainted grain. Because white-winged doves and northern bobwhites did not avoid contaminated feed, the risk of exposure to this potentially hazardous toxin exists for these species.

Survey of aflatoxin concentrations in wild bird seed purchased in Texas.

The use of backyard feeders to attract avian wildlife is a common practice throughout the United States. However, feeding wildlife may create a problem due to aflatoxin, a harmful fungal metabolite, which can affect wildlife that are fed contaminated grain. Our study was initiated to determine if songbirds were being exposed to aflatoxin-contaminated feed throughout Texas. Bags of wild bird seed (n = 142) were purchased from grain cooperatives, grocery stores, and pet shops located in the panhandle, central, south, east, and west regions of Texas during spring and summer 1999. Aflatoxin concentrations in bird seed ranged from non-detectable to 2,780 micrograms/kg. Overall, 17% of samples had aflatoxin concentrations greater than 100 micrograms/kg, of which 83% contained corn as an ingredient. Retail establishment effects were noted in the southern and western regions of Texas, with average concentrations of aflatoxin greater from bags of bird seed purchased from grain cooperatives, followed by pet shops, then grocery stores. Regional differences in aflatoxin levels were not apparent from bags of seed purchased at pet shops: however, regional differences were noted in aflatoxin levels from seeds obtained at grocery stores and grain cooperatives. Average aflatoxin concentration from seed purchased at grocery stores was greatest in the panhandle region, followed by the remaining regions. Within grain cooperatives, the panhandle, south, and west regions of Texas exhibited higher levels of aflatoxin-contaminated bird seed than cooperatives within the east and central regions of Texas. Granivorous songbirds in Texas are exposed to aflatoxins at backyard feeders, which may be a significant morbidity and mortality factor.

Bait delivery for oral rabies vaccine to gray foxes.

Rabies is a widespread zoonotic disease that has reached epizootic proportions in gray foxes (Urocyon cinereoargenteus) in central Texas. Because each species of carnivore has different food preferences and foraging strategies, it is essential that the efficacy of a bait delivery program be examined for gray foxes prior to an oral vaccination program being attempted. Field trials were conducted to determine bait preferences of free-ranging gray foxes to selected baits and odor attractants. Baits consisted of polymer cubes made of either dog food meal or fish meal, and a wax-lard cake that was enhanced with marshmallow flavoring. Attractants added to baits exuded sulfurous, fatty, cheesy, or sweet odors and flavors. During 3,589 operable bait station nights, gray fox visitation and bait uptake rates were 9.2% and 8.3%, respectively. Gray foxes exhibited no preference in bait uptake rates between bait and odor attractant combinations. Gray foxes exhibited no difference in cumulative bait uptake rates between onroad and offroad sites; however, the uptake rate by raccoons was significantly greater for baits placed on roads than for baits randomly placed. Raccoons were the major non-target species competing for baits, being attributed with 73% of the total uptake. Visitation and bait uptake rates by raccoons significantly increased after a 7-day lethal removal of raccoons (n = 37) from the study area. Random distribution of baits is recommended; it reduced bait uptake by non-target species without adversely affecting uptake by gray foxes.

Survival of Trichomonas gallinae in white-winged dove carcasses.

Survival of Trichomonas gallinae was examined in white-winged dove (Zenaida asiatica) carcasses to assess whether birds that have been dead up to 8 hr can be sampled reliably for this protozoan. Carcasses of 100 T. gallinae-positive white-winged doves were separated into four groups of 25 birds, representing 2, 4, 6, and 8 hr post mortem sampling intervals and placed into an environmental chamber maintained at 27 C and 75% relative humidity. Live T. gallinae were isolated in 96, 100, 100, and 92% of the carcasses at each of the respective post mortem intervals. The experiment was repeated with another 100 carcasses of T. gallinae-positive white-winged doves placed in the environmental chamber, this time maintained at 27 C and 40% relative humidity. Live T. gallinae occurred in 96, 100, 96, and 100% of the carcasses at each of the respective post mortem intervals. Across both trials, the overall ability to detect positive birds from sampling carcasses up to 8 hrs post mortem was 97%. An a posteriori experiment was conducted in which 23 and 18 carcasses from the second trial were maintained in the environmental chamber at 27 C and 40% relative humidity and resampled at 24 and 48 hr post mortem, respectively. Live trichomonads were isolated from 91 and 44% of the carcasses at 24 and 48 hr, respectively. Results suggest live T. gallinae can be obtained from dove carcasses reliably up to 8 hr and possibly up to 24 hr after host death. The ability for T. gallinae to survive within this time interval can aid wildlife personnel in monitoring this protozoan at hunter check stations or obtaining samples from recently killed birds.

Effect of climate and type of storage container on aflatoxin production in corn and its associated risks to wildlife species.

The effects of grain storage containers on aflatoxin production, and the relationship between the level of aflatoxin and the number and weight of fluorescing kernels were determined in corn (Zea maize) stored in controlled climate regimes. Two hundred and forty 100-g samples were held up to 3 mos using four types of storage containers placed in four climates. Storage containers included corn placed in metal cans, paper bags, plastic bags, and paper bags placed in plastic bags. Climates were constant during the duration of the project and included a combination of temperatures and humidities. Temperatures were 29-32 C and 14-18 C; relative humidities were 85-88% and 35-40%. In addition, corn was exposed to environmental conditions conductive for aflatoxin production and 100 g samples were randomly collected, examined under ultraviolet light for fluorescence, and then quantified for aflatoxin levels. Corn samples tested negative for aflatoxin at the beginning of the project. Main (i.e., container, climate, and month) and interactive effects were not observed. Mean levels of aflatoxin ranged from 0 to 151 microg/kg. Aflatoxin was produced regardless of type of storage container, time of storage, and climatic conditions; however, only 8% of the samples produced aflatoxin levels that exceeded 50 microg/kg. Fluorescing corn ranged from 0 to 19 kernels per sample, while aflatoxin levels ranged from 0 to 1,375 microg/kg for the same samples. No relationships were found between the number and weight of fluorescing kernels of corn and aflatoxin levels. The black light test yielded a false negative rate of 23% when in fact the aflatoxin concentrations exceeded 50 microg/kg. Therefore, quantifying fluorescing grain under UV light should not be considered a feasible alternative for aflatoxin testing of grain intended for wildlife.

Gray fox response to baits and attractants for oral rabies vaccination.

Rabies is a widespread zoonosis that recently reached epidemic proportions in gray foxes (Urocyon cinereoargenteus) in central Texas. The objectives of this study were to determine bait and attractant preferences among captive gray foxes, to determine the behavioral responses of gray foxes to selected bait-attractant combinations, and to evaluate baits as a delivery mechanism of oral rabies vaccines. Trials were conducted to determine bait preferences of captive gray foxes to selected baits and attractants. Tested baits consisted of a polymer-bound cube made of either dog food meal or fish meal, a polymer-bound cylinder made of dog food meal, and a wax-lard cake that was enhanced with marshmallow or chicken flavoring. Attractants were additives to baits that exuded sweet, sulfurous, fruity, fatty, cheesy, honey, and fishy odors and flavors. Captive gray foxes (n = 31) exhibited a preference for marshmallow wax cakes and polymer dog food baits with a lard interior and granulated sugar exterior. However, gray foxes exhibited chewing behaviors consistent with ingesting an oral vaccine only with the wax cake baits.

Responses of captive and free-ranging coyotes to simulated oral rabies vaccine baits.

The objective of this study was to develop a bait for delivering an oral rabies vaccine to free-ranging coyotes (Canis latrans) in southern Texas. Captive trials were conducted from January to April, 1994, to determine bait preferences and behavioral responses of coyotes (n = 42) to selected baits and attractants. Baits were hollow rectangular cubes made of polymer dog food or fish meal. Attractants had sweet (watermelon), fruity (raspberry), sulfurous (synthetic WU), and lard (beef lard) fragrances. Captive coyotes did not exhibit a preference for either bait bases or attractants; however, coyotes chewed dog food baits 1.6 times more than fish meal baits. Average proximity of coyotes eliciting a response to baits was 2.2 +/- 1.3 m (mean +/- SE). Captive coyotes readily accepted dog food baits containing 2 ml of liquid rhodamine B, a biological marker. Rhodamine B staining of the oropharyngeal region was evident in each captive coyote. Results from the field evaluation of baits and attractants were consistent with that of the captive trials. Of 2,070 bait station-nights conducted from February to April, 1994, coyotes comprised the greatest single species visitation and uptake rates with 31% and 28%, respectively. Bait uptake rates of free-ranging coyotes did not differ among bait-attractant combinations. Coyotes took baits 93% of the time they encountered a bait, regardless of bait type.

Efficacy of bait distributional strategies to deliver canine rabies vaccines to coyotes in southern Texas.

This study sought to develop a baiting strategy to deliver an oral rabies vaccine to free-ranging coyotes (Canis latrans) in southern Texas. To determine bait longevity, dog foodlard baits were placed (n = 50) on- and off-roads during July 1994 and January 1995. Coyote visitation and uptake rates did not differ between on-road and off-road placement of baits. To evaluate bait stations as possible visual cues, baits were placed out both with (n = 50) and without (n = 50) bait stations. A visual cue of a bait station did not affect coyote response to baits. Bait longevity was shorter during July (< or = 4 days) than January because of consumption of baits by imported fire ants (Solenopsis invicta). The effect of two different bait densities on coyote acceptance rates was determined on six 93.5 km2 study areas in southern Texas. Three study areas received a bait density of 19 baits/km2 (50 baits/mi2) and the remaining three study areas received 58 baits/km2 (150 baits/mi2). Coyote bait uptake rates, based upon the proportion of coyotes marked with either tetracycline hydrochloride or rhodamine B or both, were 83% (n = 99 coyotes) and 87% (n = 101 coyotes) for the 19 and 58 baits/km2 densities, respectively. Bait uptake rates did not differ (P > 0.54) between the two bait densities. Rodents and rabbits, which were fed baits containing tetracycline hydrochloride and a simulated oral rabies vaccine sachet containing rhodamine B, did consume the bait but not the rhodamine B sachet. These animals then were killed and fed to captive coyotes (n = 9). Canine teeth were extracted from coyotes and processed for tetracycline determination. Each coyote tested negative for tetracycline. Therefore, it was unlikely that coyote bait consumption rates were overestimated because of coyotes secondarily marking themselves by ingesting prey items that consumed baits.

Baylisascariasis in raccoons from southern coastal Texas.

Two hundred and two Baylisascaris procyonis were collected from 23 (70%) of 33 raccoons (Procyon lotor) at three localities in southern coastal Texas (USA). Abundances of B. procyonis were similar among collection localities. The presence of B. procyonis in Texas is confirmed, and this record considerably extends the potential range of baylisascariasis larval migrans in North America.

Changes in vitreous humor associated with postmortem interval in rabbits.

Concentrations of serum and vitreous humor constituents at time of death, and concentrations of vitreous humor constituents at time of death and at 7 postmortem intervals were compared in 70 domestic, female New Zealand White rabbits (Oryctolagus cuniculus). Urea nitrogen concentration was significantly (P = 0.0094) different, but was linearly correlated in serum and vitreous humor at time of death and at the 4- and 8-hour postmortem intervals. Concentrations of gamma-glutamyltransferase were not significantly different in serum and vitreous humor at time of death, nor were concentrations significantly different in vitreous humor at time of death and at the 4-hour postmortem interval. The vitreous humor concentrations of glucose, triglycerides, sodium, potassium, cholesterol, total protein, albumin, lactate dehydrogenase, creatine kinase, aspartate transaminase, bilirubin, cortisol, and IgG were neither similar to nor predictive of serum constituents. Vitreous humor can be used as a source for estimates of serum urea nitrogen and gamma-glutamyltransferase up to 8 and 4 hours after death, respectively.

Urinary bladders of freshwater turtles as a renal physiology model potentially biased by monogenean infections.

Because the urinary bladder of the freshwater red-eared slider turtle, Trachemys scripta elegans, is analogous to the collecting and distal tubules of the mammalian kidney, it is used frequently as an experimental model in renal physiology. The urinary bladders of 41% of these turtles obtained over a 1 year period from a commercial supplier were infected with the monogenean parasite Neopolystoma orbiculare. Macroscopically, the infected bladders appeared normal, aside from the presence of adult parasites (means = 2.3 +/- 0.3 monogeneans/turtle). However, there were distinct histological lesions associated with the deposition of masses of monogenean eggs in the bladder wall. Clusters of the eggs in varying stages of development in the mucosa and tunica muscularis were surrounded by granulomas with an inflammatory infiltrate of histiocytes, lymphocytes and occasional multinucleate giant cells. These often formed granulomatous polyps projecting into the bladder lumen. Eggs containing a mature oncomiracidium are apparently extruded into the bladder lumen. In general, the bladder walls of infected turtles were infiltrated with eosinophils and lymphocytes. Considering the extent of the inflammatory lesions, it is recommended that turtle bladders infected with these parasites not be used as models for renal physiology until the effects of these infections on the various physiological measurements are determined.

Effect of diet on condition indices in black-tailed jackrabbits.

Changes in blood, urine and physical condition indices in 23 adult male black-tailed jackrabbits (Lepus californicus) with ad libitum feeding and 25% feed restriction were measured over a 2 wk period from 30 May to 12 June 1988. Feed restricted jackrabbits had (1) lower post-trial body weights and kidney fat indices, (2) higher femur marrow fat, serum bilirubin and cortisol concentrations, and adrenal cortex width, and (3) depressed immune function. No single index alone could best measure the nutritional status of these jackrabbits.

Serologic survey of selected zoonotic disease agents in black-tailed jack rabbits from western Texas.

A serologic survey for the agents of Rocky Mountain spotted fever (RMSF) (Rickettsia rickettsii), Borrelia spp. including the causative agent for Lyme disease (Borrelia burgdorferi), and plague (Yersinia pestis) was conducted on blood samples collected from 30 and 46 black-tailed jack rabbits (Lepus californicus) from an urban environment in Lubbock, Texas (USA) during winter 1987 and the following spring 1988, respectively. Antibody titers to the agents of RMSF and borreliosis were detected in sera of 28 and 1% of the jack rabbits, respectively. Neither organisms (rickettsiae and/or spirochetes) nor their associated antigens were detected in any of the tissue or whole blood samples; plague antibodies were not detected in the 76 jack rabbits sampled. Four of 18 ticks (Dermacentor parumapertus) removed from 12 jack rabbits were positive for RMSF using the fluorescent antibody test. The black-tailed jack rabbit is a common wildlife species living in close proximity to higher density human populations in many areas of the southwestern United States. Our results indicate the potential importance of urban populations of this mammal as reservoirs for at least one important zoonotic disease, RMSF, in western Texas.