Short‐distance dispersal of splashed bacteria of Xanthomonas citri subsp. citri from canker‐infected grapefruit tree canopies in turbulent wind

Citrus canker (Xanthomonas citri subsp. citri (Xcc)) can cause yield loss and trade restrictions. The pathogen is dispersed in rain splash and spread is promoted by wind. The goal of this study was to gain some insight into the properties of short‐distance splash dispersal of Xcc from ～1·5 m‐tall cankered grapefruit canopies in turbulent wind, common during rainstorms in Florida. Turbulent wind up to 19·9 m s^?1 was tested in five experiments. Bacteria flux density (BFD, bacteria cm^?2 min^?1) was quantified at heights of 30, 70, 110, 130 and 180 cm above ground, and at four horizontal points (17, 51, 85 and 119 cm) at each height across the direction of the wind 1 m downwind. BFD varied among experiments, but the lowest BFDs were consistently detected at the greatest sample height. Despite differences between experiments, the relationship between log BFD and sample height was consistently described by a linear function (P = 0·06–<0·0001, R² = 0·75–>0·99). The BFD collected at the horizontal points across the wind path was variable. BFDs collected were sometimes significantly different, but no relationship was discernible. Stronger, turbulent wind resulted in greater BFD, with a linear function describing the relationship between log BFD and wind speed (P = 0·2–0·02, R² = 0·94–0·96). Multiple regression analysis demonstrated predictability of the proportion of total bacteria collected (F = 141, P < 0·0001, d.f. = 3, R² = 0·53).     

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.     

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.     

Effects of an S6 strain of Mycoplasma gallisepticum inoculation before beginning of lay on the leukocytic characteristics of commercial layers

A clinical study was conducted on commercial layers housed in biological isolation units, within which exogenous stress factors potentially affecting bird performance were minimized. This set-up was devised in order to assess how a pre-lay inoculation of S6 strain Mycoplasma gallisepticum affects the leukocytic properties of laying chickens. Previous studies have demonstrated relative decreases in lymphocyte and relative increases in heterophil percentages in birds infected with other strains of Mycoplasma gallisepticum. However, current results showed that the differential percentages of lymphocytes were decreased, whereas those of heterophils were increased, in both sham-inoculated control birds and birds inoculated with S6 Mycoplasma gallisepticum between 19 and 26 wk of age. This study clearly shows that a pre-lay inoculation of S6 Mycoplasma gallisepticum alone had no apparent effect on the leukocyte profile of commercial layers housed in biological isolation units.     

Excess cortisol interferes with a principal mechanism of resistance to dehydration in Bos indicus steers

This study investigated the effects of excess cortisol on physiological mechanisms that resist dehydration in Bos indicus steers (n = 31, 2 yr of age, 193 +/- 21.47 kg mean BW) during a 90-h period. Steers were assigned randomly to one of four groups: 1) no water/no cortisol (n = 8), 2) water/no cortisol (n = 8), 3) no water/cortisol (n = 8), and 4) water/cortisol (n = 7). Animals allocated to cortisol treatment groups were given 0.1 mg x kg BW(-1) x h(-1) of hydrocortisone suspended in isotonic saline for the duration of the study. Total body water, osmolality, hematocrit, urine output, feed and water intake, and plasma concentrations of arginine vasopressin (AVP), angiotensin II (AII), electrolytes, total protein, and albumin were determined at 24-h intervals for 90 h. In the presence of excess plasma cortisol, total body water was maintained in the presence of a water deprivation insult for 90 h, whereas hydration indices, such as total plasma protein and albumin, did not change, supporting the body water data. However, plasma osmolality increased for the water-deprived groups from 24 h (P = 0.008). Hematocrit did not reflect dehydration in any group. Water deprivation induced an increase in endogenous plasma cortisol concentrations after 60 h of the study (P = 0.028). Plasma concentrations of AVP increased with water deprivation (P = 0.006). Excess cortisol decreased the plasma concentration of AVP at 72 h only (P = 0.027) and suppressed plasma concentrations of AII at 24 and 72 h (P < 0.001 and P = 0.036, respectively). Animals treated with excess cortisol maintained urinary output for 48 h before decreasing at 72 h (P = 0.057), although there was no effect on water or feed intake. Water deprivation increased plasma sodium concentrations (P < 0.05) until 72 h, whereas potassium decreased under the influence of excess plasma cortisol (P = 0.001) at 24 h. Water deprivation increased plasma chloride concentration at 72 and 90 h (P = 0.051 and P = 0.026, respectively). Plasma phosphorus decreased at 24 h (P = 0.001) and remained at lesser concentrations for the duration of the study (P = 0.05). These results highlight the complexity of endocrine interactions associated with water balance in Bos indicus steers. We accept our hypothesis that, in the presence of excess cortisol, the renin-angiotensin-aldosterone axis is suppressed; however, homeostasis is achieved through other physiological systems.     

Position of inoculum in the canopy affects the risk of septoria tritici blotch epidemics in winter wheat

The spread of septoria leaf blotch in wheat caused by Mycosphaerella graminicola is widely reported to depend on the occurrence of splashy rainfall. Previous studies have also implicated an important effect of canopy architecture on the risk of disease spread. This is because architecture affects the proximity of the yield-forming leaves to inoculum present on older diseased leaves within the crop. This study demonstrated that infection of the final three leaves of winter wheat could occur in the absence of splashy rainfall. For cvs Riband and Longbow, the final two leaf layers emerged at a position ≈ 8 cm below older leaves containing sporulating lesions. Under these conditions, infection of new leaves occurred in treatments that simulated dew and nonsplashy rainfall. These treatments resulted in disease incidences of 10–40% above the untreated control on the final two leaf layers. Within a season, the distance between diseased and healthy leaves during the period of stem extension varied substantially across a range of 30 cultivars. While the magnitude of these differences was not the same across seasons, the relative differences between cultivars were generally consistent, suggesting a strong genotype influence on lesion proximity. This study shows how knowledge of the distribution of lesion proximity within a crop can be used to estimate the risk of inoculum transfer for a given maximum splash height. A rapid crop-monitoring method for estimating the distribution of lesion proximity was developed and tested. Lesion proximity was manipulated by plant growth regulator (PGR) treatments. Significant increases in disease, between 14 and 62%, were observed on the upper canopy leaves of plants treated with PGR. The largest differences were observed in treatments where lesion proximity was most affected.     

Keratinizing ameloblastoma in a 9-month-old llama (Lama glama).

A 9-month-old male llama (Lama glama) was presented because of a rapidly growing mass on the right side of the face. Radiographs revealed a marked expansion of the right caudal face region with bone lysis involving the maxilla and the nasal, lacrimal, zygomatic, and palatine bones. Cytologically, the mass consisted of atypical round to polygonal cells with round nuclei and basophilic cytoplasms that formed acini and rows. Histologically, the mass consisted of anastomosing cords and sheets of neoplastic odontogenic epithelial cells embedded in a loose fibrovascular connective tissue. Single layers of peripheral, polarized, palisading, columnar epithelial cells were seen at the edges of some cords. Within the centers of the cords, epithelial cells showed rapid progression to keratin production. The histologic diagnosis was keratinizing ameloblastoma. Ameloblastomas are neoplasms of odontogenic epithelium that tend to be locally aggressive and can cause substantial destruction of bony structures. Because ameloblastomas do not tend to metastasize, they can be successfully treated by complete surgical excision, performed before extensive bony destruction occurs. Ameloblastoma, although expected to be rare, should be onthe list of differential diagnoses for facial swelling in llamas.     

Use of lufenuron as a treatment for fungal endometritis in four mares

Lufenuron, a benzoylphenyl urea derivative, was evaluated as a treatment for endometrial fungal infections in 4 mares. Intrauterine lavage was performed with lufenuron suspended in sterile saline (0.9% NaCl) solution. Cytologic evaluation and fungal culture of the endometrium, as well as subsequent reproductive performance, were used to monitor efficacy of this treatment. Fungal endometritis in mares is associated with infertility. Treatment is often ineffective and costly, and recurrence following treatment is not uncommon. Intrauterine infusions of lufenuron were effective in eliminating fungal endometritis in the 4 mares of this report.     

Use of a parainguinal approach for cryptorchidectomy in alpacas

Cryptorchidism is an uncommon condition in llamas and alpacas, and there are no reports detailing surgical management of this condition in llamas or alpacas; however, flank or ventral midline approaches have been mentioned. Cryptorchid castration was performed by use of a parainguinal approach in 2 alpacas. The retained testicle of each alpaca was found on the ventral aspect of the abdomen, just caudal to the incision in 1 alpaca and at the cranial edge of the incision in the other. The testicle was approximately 1 X 0.5 cm in 1 alpaca and 2 X 1 cm in the other. In an alpaca or llama with a single abdominal testicle and no history of surgery, the parainguinal approach has several advantages, including the likely proximity of the testicle to the incision; the small incision, which can be extended if needed; ease of closure; and minimal aftercare. The retained testicles were small and could be difficult to find from a more distant midline, paramedian, or flank incision.