Detection of macrocyclic trichothecene mycotoxin in a caprine (goat) tracheal instillation model.

This study demonstrates the detection and dynamics of macrocyclic trichothecene mycotoxin (MTM) tissue loading using a commercially available assay in a goat model. The detection of MTMs has been difficult and complex due to the uncertainty of what tissues to examine and when to sample. Twelve goats (two groups of each) were instilled with Stachybotrys chartarum conidial suspension via the trachea. The first group was challenged repeatedly with fungal conidia containing 1 mg/kg of MTM per instillation whereas the second group was exposed once, to spores with a calculated concentration of 5 microg/kg of mycotoxin. These toxin estimates were generated by the QuantiTox(TM) Kit assay; a conidium of S. chartarum possessed 8.5 pg of MTM. After repeated exposure of 3 days, MTM was detected in one of six animals. This animal and two others from the same group had mycotoxin detected in their serum 24 hours after challenge at a comparable level (1.69 ng/mL) to the six animals challenged with a single dose (2.02 ng/mL) at the same time post-instillation. Results showed that MTMs are detectable in experimental animals soon after challenge and contribute to the understanding of the role of these mycotoxins in the disease process following mold exposure.

Effects of inhaled fine dust on lung tissue changes and antibody response induced by spores of opportunistic fungi in goats.

OBJECTIVE: To investigate the effects of sterile fine dust aerosol inhalation on antibody responses and lung tissue changes induced by Mucor ramosissimus or Trichoderma viride spores following intratracheal inoculation in goats. ANIMALS: 36 weanling Boer-Spanish goats. PROCEDURES: 6 goats were allocated to each of 2 M ramosissimus-inoculated groups, 2 T viride-inoculated groups, and 2 control (tent or pen) groups. One of each pair of sporetreated groups and the tent control group were exposed 7 times to sterilized fine feedyard dust (mean+/-SD particle diameter, <7.72+/-0.69 microm) for 4 hours in a specially constructed tent. Goats in the 4 fungal treatment groups were inoculated intratracheally 5 times with a fungal spore preparation (30 mL), whereas tent control goats were intratracheally inoculated with physiologic saline (0.9% NaCl) solution (30 mL). Pen control goats were not inoculated or exposed to dust. Goats received an IV challenge with equine RBCs to assess antibody responses to foreign antigens. Postmortem examinations were performed at study completion (day 68) to evaluate lung tissue lesions. RESULTS: 5 of 7 deaths occurred between days 18 and 45 and were attributed to fine dust exposures prior to fungal treatments. Fine dust inhalation induced similar lung lesions and precipitating antibodies among spore-treated goats. Following spore inoculations, dust-exposed goats had significantly more spores per gram of consolidated lung tissue than did their nonexposed counterparts. CONCLUSIONS AND CLINICAL RELEVANCE: Fine dust inhalation appeared to decrease the ability of goats to successfully clear fungal spores from the lungs following intratracheal inoculation.

Effects of aerosolized class C fly ash in weanling goats.

OBJECTIVE: To determine effects of repeated aerosol exposures to fly ash dust on respiratory tracts of tent-confined goats. ANIMALS: 12 weanling Boer-Spanish crossbred goats. PROCEDURE: Goats were randomly assigned to 2 groups: fly ash treatment group (principal goats, n = 6) or control group (control goats, 6). Aerosolized fly ash dust was provided during a 4-hour period for each of 6 applications given over 3 months and one 2-hour application prior to necropsy. Fly ash particle diameters ranged from 0.1 to 130 microm and averaged 17.8 microm, with 1.5% of fly ash particles in the 0.1- to 5-microm-diameter range. A mean +/- SD of 748 +/- 152 g/treatment was delivered inside a tent containing principal goats; control goats were placed inside a similar tent for 4-hour treatments without dust. Following treatment, rectal temperatures were taken at 0, 4, 6, 8, 24, and 72 hours; Hcts were recorded at 0, 24, and 72 hours. RESULTS: Rectal temperatures were significantly increased at 4, 6, and 8 hours and decreased at 72 hours, compared with 0 hours. Mean +/- SEM Hct values were significantly increased for principal goats (3747 +/- 0.39%), compared with control goats (36.17 +/- 0.42%). A significant increase in the mean area of gross atelectatic lung lesions (1,410 mm2) was found in principal goats (n = 6), compared with control goats (440 mm2; 5). CONCLUSIONS AND CLINICAL RELEVANCE: An increase in atelectatic lung lesions was observed in principal goats, compared with control goats; however, overall, fly ash dust effects were nontoxic.

Virulence of fungal spores determined by tracheal inoculation of goats following inhalation of aerosolized sterile feedyard dust.

OBJECTIVE: To compare the virulence of spores of 7 fungi by tracheal inoculation of goats following exposure of goats to an aerosol of sterilized feedyard dust. Animals-54 weanling Boer-Spanish goats. PROCEDURE: A prospective randomized controlled study was conducted. There were 7 fungal treatment groups, a tent control group, and a pen control group (n = 6 goats/group). Goats in the 7 treatment and tent control groups were exposed to autoclaved aerosolized feedyard dust for 4 hours in a specially constructed tent. Goats in the 7 treatment groups were then inoculated intratracheally with 30 mL of a fungal spore preparation, whereas tent control goats were intratracheally inoculated with 30 mL of physiologic saline (0.9% NaCI) solution. These treatments were repeated each week for 6 weeks. RESULTS: Severity of pathologic changes differed significantly among the 7 fungal treatment groups as determined on the basis of gross atelectatic and consolidated lung lesions and histologic lesions of the lungs. Descending order for severity of lesions was Mucor ramosissimus, Trichoderma viride, Chaetomium globosum, Stachybotrys chartarum, Aspergillus fumigatus, Penicillium chrysogenum, and Monotospora lanuginosa. Trichoderma viride spores were the most invasive and were isolated from the bronchial lymph nodes and thoracic fluid of all 6 goats administered this organism. Spores were observed-histologically in lung tissues harvested 72 hours after inoculation from all treatment groups. CONCLUSIONS AND CLINICAL RELEVANCE: 4 of 7 fungal spore types induced significantly larger lung lesions, compared with those induced by the other 3 spore types or those evident in control goats.

Effect of transport stress on respiratory disease, serum antioxidant status, and serum concentrations of lipid peroxidation biomarkers in beef cattle.

OBJECTIVE: To determine the effect of transportation stress on serum concentrations of oxidative stress biomarkers of calves. ANIMALS: 105 crossbred beef steer calves (mean [+/-SD] body weight, 207 +/- 21.2 kg). PROCEDURE: Calves were assembled at 1 location in Tennessee, and pretransit (day -3) blood samples were collected. Calves were allotted randomly by body weight into 2 groups. Calves were transported 1,930 miles to a feedlot in Texas, and 1 group received tilmicosin phosphate (33 microg/kg, s.c.) upon arrival. Calves were weighed and blood samples collected on the day of arrival (day 1) and on days 15, 22, and 28. Calves were scored daily for signs of bovine respiratory disease (BRD). Serum total antioxidant capacity (TACA) and serum malondialdehyde (MDA) concentrations were determined. RESULTS: Transportation stress significantly decreased mean serum TACA concentrations (from 147 +/- 31.2 U/mL to 133 +/- 20.1 U/mL) and significantly increased serum MDA concentrations (from 10.9 +/- 18.3 microg/mL to 30.2 +/- 50.5 microg/mL). Calves that died had a 43% increase in serum MDA concentration on day 1, compared with calves that lived (42.2 +/- 67.0 microg/mL vs 29.4 +/- 49.4 microg/mL, respectively). Calves that had > or =3 episodes of BRD had 2-fold higher serum MDA concentrations on day 1 than healthy calves. Tilmicosin-treated calves had a 20.8% significantly greater average daily gain and significantly greater serum TACA concentration than nontreated calves on day 28. CONCLUSIONS AND CLINICAL RELEVANCE: Transportation stress increases serum concentrations of oxidative stress biomarkers that are related to episodes of BRD and mortality in calves.

Diversity of Salmonella serovars in feedyard and nonfeedyard playas of the Southern High Plains in the summer and winter.

OBJECTIVE: To compare Salmonella isolates cultured from feedyard and nonfeedyard (control) playas (ie, temporary shallow lakes) of the Southern High Plains. SAMPLE POPULATION: Water and muck (sediment) samples were obtained from 7 feedyard playas and 3 nonfeedyard playas in the winter and summer. PROCEDURE: Each water and muck sample was enriched with sulfur-brilliant-green broth and incubated in a shaker at 37 degrees C for 24 hours. A sample (100 mL) of the incubated bacterial-enriched broth was then mixed with 100 mL of fresh sulfur-brilliant-green enrichment broth and incubated in a shaker at 37 degrees C for 24 hours. After the second incubation, a swab sample was streaked on differential media. Suspect Salmonella isolates were further identified by use of biochemical tests, and Salmonella isolates were confirmed and serovar determinations made. RESULTS: Salmonella isolates were not recovered from the 3 control playas. Seven Salmonella enterica serovars were isolated from 5 of 7 feedyard playas in the summer, and 13 S. enterica serovars were isolated from 7 of 7 feedyard playas in the winter. In the summer, 296 isolates were cultured, and 47 were Salmonella organisms. In the winter, 288 isolates were cultured, and 171 were Salmonella organisms. CONCLUSIONS AND CLINICAL RELEVANCE: Results indicated that feedyard playas are frequently contaminated with many Salmonella serovars. These pathogens should be considered whenever feedyard managers contemplate the use of water from these playas. Water from feedyard playas should not be used to cool cattle in the summer or for dust abatement.

Comparison of the type and number of microorganisms and concentration of endotoxin in the air of feedyards in the Southern High Plains.

OBJECTIVES: To determine the bacterial, fungal, and endotoxin concentrations in aerosolized ambient air during the winter and summer in feedyards located in the Southern High Plains, identify aerosolized microbial pathogens, and determine the size of microbial and dust components. SAMPLE POPULATION: Aerosol samples were obtained from 7 feedyards. PROCEDURE: Aerosol samples were collected upwind, on-site, and downwind from each feedyard at a point 1 m above the ground by use of biological 2- and 6-stage cascade impactors. RESULTS: Significantly more microbes were cultured from on-site and downwind samples than upwind samples. There were significantly more microbes during the summer than during the winter. However, mean endotoxin concentration was significantly higher during the winter (8.37 ng/m3) than the summer (2.63 ng/m3). Among 7 feedyards, mean +/- SE number of mesophilic bacteria (1,441 +/- 195 colony-forming units [CFUs]/m3) was significantly higher than mean number of anaerobic bacteria (751 +/- 133 CFUs/m3) or thermophilic bacteria (54 +/- 10 CFUs/m3) in feedyard air. Feedyard aerosol samples contained more mesophilic fungi (78 +/- 7 CFUs/m3) than thermophilic fungi (2 +/- 0.2 CFUs/m3). Eighteen genera of bacteria were identified by use of an automated identification system. CONCLUSIONS AND CLINICAL RELEVANCE: It appeared that gram-negative enteric pathogens offered little risk to remote calves or humans via ambient aerosols and that gram-positive pathogens of the Bacillus, Corynebacterium, and Staphylococcus spp can be spread by aerosols in and around feedyards. It was common to detect concentrations of endotoxin in the ambient air of 7 feedyards.

Effects of aerosolized dust in goats on lung clearance of Pasteurella and Mannheimia species.

The objective was to determine whether the inhalation of large quantities of feedyard dust predisposed the animals to pulmonary bacterial proliferation. Two control groups, C1 and C2, did not receive dust treatments, and two principal groups (P1 and P2) received a total of 14 dust treatments each. The C1 and P1 groups of goats each received a transthoracic challenge of live Mannheimia haemolytica (4 x 10(6) colony forming units, CFU) The C2 and P2 groups of goats each received a transthoracic challenge of live Pasteurella multocida (1.0 x 10(6) CFU/goat). The results showed that dusted animals had fever when compared with non-dusted controls. In addition, dusted animals demonstrated a leukocytosis with neutrophilia after the first dust treatment that was not sustainable. Finally, dusted animals demonstrated pulmonary clearance of two potential bacterial pathogens that was not significantly different from that shown by control (not dusted) animals.

Bovine adenovirus serotype 7 infections in postweaning calves.

OBJECTIVE: To detect bovine adenovirus serotype 7 (BAV-7) infections in calves by use of viral isolation and serologic testing. ANIMALS: 205 postweaning calves. PROCEDURE: 121 calves were assembled by an order buyer through auction markets in eastern Tennessee and transported to New Mexico where they were commingled with 84 healthy ranch-reared calves. Tests included viral isolation in cell culture from peripheral blood leukocytes (PBL) and detection of serum BAV-7 antibodies by use of microtitration viral neutralization. RESULTS: BAV-7 was isolated from PBL of 8 calves and seroconversion to BAV-7 was detected for 38 of 199 (19.1%) calves. Concurrent bovine viral diarrhea virus infections were detected in most calves from which BAV-7 was isolated. CONCLUSIONS AND CLINICAL RELEVANCE: Results of our study indicate that BAV-7 infections can be found in postweaning commingled calves and may develop more commonly in calves with concurrent infections with viruses such as bovine viral diarrhea virus (BVDV).

Effects of vaccination prior to transit and administration of florfenicol at time of arrival in a feedlot on the health of transported calves and detection of Mannheimia haemolytica in nasal secretions.

OBJECTIVE: To determine effects of vaccination prior to transit and prophylactic administration of florfenicol at time of arrival at a feedyard on health of cattle and colonization of the nasopharynx by Mannheimia haemolytica (MH). ANIMALS: 121 steers from Tennessee and 84 steers from New Mexico. PROCEDURE: Half of the steers were vaccinated before transport to a feedyard. Steers from Tennessee were vaccinated with MH bacterin-toxoid, and steers from New Mexico were vaccinated intranasally with modified-live leukotoxin-deficient MH. Half of the vaccinates and nonvaccinates were randomly selected to receive florfenicol on arrival at the feedyard. Steers were observed daily for respiratory tract disease (RTD). RESULTS: Administration of florfenicol at time of arrival reduced the incidence of RTD, delayed the interval before onset of RTD, and reduced the incidence of MH colonization of the nasopharynx for at least 4 days, but vaccination did not have any effect. Vaccination elicited an increase in serum antibody titers to MH. Administration of florfenicol at time of arrival reduced the development of serum antibody titers in intranasally vaccinated steers and both groups of nonvaccinated steers, but intranasal vaccination did not affect colonization by wild-type MH. CONCLUSIONS AND CLINICAL RELEVANCE: Administration of florfenicol at time of arrival decreased the incidence of MH organisms in the nasopharynx and delayed the onset of RTD. Prophylactic use of suitable antibiotics is likely to reduce the incidence of acute RTD in calves for several days after arrival at feedyards, which is the period when they are most susceptible to infectious organisms.

Effects of aerosolized feedyard dust that contains natural endotoxins on adult sheep.

OBJECTIVE: To determine the clinical, clinicopathologic, and histologic effects of aerosolized feedyard dust that contains natural endotoxins on adult sheep. ANIMALS: Eighteen 3-year-old Saint Croix sheep. PROCEDURE: A prospective randomized controlled study was conducted. There were 2 treatment groups (dust-endotoxin group, n = 9; control group, 9). Aerosolized feedyard dust was provided continuously during a 4-hour period for each application (once in week 1, 3 times in week 2, and 7 times in week 3) to sheep in a semiairtight tent. All sheep were euthanatized and necropsied 8 hours after the treatment group received the last dust treatment. Variables measured before and after each dust treatment were rectal temperature, total WBC count, and concentrations of fibrinogen and haptoglobin. RESULTS: Mean amount of dust administered during each treatment was 451 g/4 h. Filter collection indicated 51 mg of dust/m3 and 7,423 ng of endotoxin. Mean rectal temperature at 8 hours (40.4 C) and mean WBC counts 12 and 24 hours after dust treatment were significantly higher for the treated group than the means of the respective variables for the control group. Similar responses were observed with repeated dust-endotoxin treatments; however, with each subsequent treatment, there was a diminished response. Sheep in the treatment group had generalized alveolar septal thickening and hypercellularity. CONCLUSIONS AND CLINICAL RELEVANCE: Feedyard dust induced a temporary febrile response and leukocytosis in sheep in the treatment group. Exposure to dust that contains endotoxins may be a stressor preceding acute infectious respiratory tract disease of marketed sheep.