Environmental risk factors for equine West Nile virus disease cases in Texas

West Nile Virus (WNV) was first detected in the Texas equine population during June 2002. Infection has since spread rapidly across the state and become endemic in the equine population. Environmental risk factors associated with equine WNV attack rates in Texas counties during the period 2002 to 2004 were investigated. Equine WNV attack rates were smoothed using an empirical Bayesian model, because of the variability among county equine populations (range 46−9,517). Risk factors investigated included hydrological features (lakes, rivers, swamps, canals and river basins), land cover (tree, mosaic, shrub, herbaceous, cultivated and artificial), elevation, climate (rainfall and temperature), and reports of WNV-positive mosquito and wild bird samples. Estimated county equine WNV attack rate was best described by the number of lakes, presence of broadleaf deciduous forest, presence of cultivated areas, location within the Brazos River watershed, WNV-positive mosquito status and average temperature. An understanding of environmental factors that increase equine WNV disease risk can be used to design and target disease control programs.     

Effects of ingestion of ponderosa pine needles by late-pregnant cows on uterine blood flow and steroid secretion.

Consumption of Ponderosa pine needles by late-pregnant beef cows results in the premature delivery of a viable calf. We have demonstrated the presence of a factor(s) in plasma from cows fed pine needles that specifically increased uterine arterial tone (i.e., decreased arterial diameter) in vitro. This study was designed to investigate changes in uterine blood flow and steroid secretion/uptake by the gravid uterus of cows fed pine needles to induce premature parturition. Sixteen beef cows were laparotomized on d 240 of gestation, and an electromagnetic blood-flow probe was placed around the uterine artery supplying the gravid horn. Cows were randomly assigned on d 250 of gestation to a control (n = 8; 8.2 kg/d of alfalfa hay) or pine needle (n = 8; 2.7 kg/d of pine needles + 5.5 kg/d of alfalfa hay) diet. Uterine blood flow was monitored, and systemic blood (uterine arterial and[or] jugular venous) and uterine venous blood samples were collected daily between 0630 and 0800, just before feeding. Five of eight cows fed pine needles calved prematurely (average day of gestation = 260.2 +/- .6) compared with cows fed the control diet, which calved on 287.6 +/- 3.4 d of gestation. Uterine blood flow in the control cows remained constant from d 250 through the day of parturition. In contrast, uterine blood flow of cows fed pine needles that calved early decreased progressively (P less than .01), declining to 25.2% of its original value by the day of parturition.(ABSTRACT TRUNCATED AT 250 WORDS)     

Standing surgery and procedures of the head

Although most surgical procedures of the head are technically easier to perform with the horse under general anesthesia, other factors will influence whether a surgical procedure is performed with the horse standing or recumbent under the influence of general anesthesia. The accessibility of the head lends itself to many standing surgical procedures if the proper combination of analgesia and physical and chemical restraint is used. Traumatic injuries of the head (lacerations, facial bone fractures, and oral fractures) may involve vital structures, and a thorough examination is indicated. Failure to treat a traumatic injury may result in facial deformity, bony sequestra, paranasal sinusitis, salivary-cutaneous fistula, cutaneous fistulas into a nasal passage or paranasal sinus, nasal septal deformities, and ocular dysfunction. Proper management of these injuries typically results in a cosmetic outcome because of the head's abundant blood supply. Other surgical procedures that can be performed in the standing horse include centesis and trephination of the paranasal sinuses, certain dental procedures, alar fold stabilization, and extirpation of epidermal inclusion cysts of the nasal diverticulum.     

Ivermectin for the control of swine scabies: relative values of prefarrowing treatment of sows and weaning treatment of pigs

Ivermectin given in a single subcutaneous dose (300 micrograms/kg of body weight) was tested for activity against swine scabies (Sarcoptes scabiei). Efficacy was determined by recoveries of mites from ear scrapings and by observations of clinical signs. Treatment of infected sows 8 to 37 days before farrowing eliminated scabies from the sows and prevented its transmission to their offspring. Pigs farrowed by ivermectin-treated sows remained noninfected throughout the study regardless of whether they were treated with ivermectin at weaning. Placebo-treated sows remained infected and transmitted scabies to their offspring. Ivermectin treatment of pigs at weaning eliminated the infection, whereas placebo treatment did not. The placebo-treated pigs remained infected while in the nursery, but ivermectin treatment eliminated the infection when they were moved to the growing and finishing floor at 12 weeks of age. It appears that an effective control program for swine scabies using ivermectin could be based on a single treatment of the sows before farrowing. Any infection (epizootic) appearing in growing pigs could be controlled by a single treatment of all in-contact pigs.     

Alterations in Lipoprotein Profiles in Dogs With Lymphoma

After a 12-hour fast, blood samples were obtained from 31 dogs with previously untreated lymphoma. Blood samples were also collected from 16 of these dogs after up to 5 treatments with doxorubicin (30 mg/m² intravenously every 3 weeks). All 16 dogs underwent complete remission. Five dogs were re-evaluated after relapse and after overt signs of cancer cachexia had become clinically apparent. Samples were assayed for 8 quantitative parameters: total cholesterol (T-CH) and total triglyceride (T-TG) concentrations, and the concentration of cholesterol and triglyceride in each of the three major lipoprotein fractions, very-low-density lipoprotein (VLDL-CH and VLDL-TG), low-density lipoprotein (LDL-CH and LDL-TG), and high-density lipoprotein (HDL-CH and HDL-TG). The results were compared with those from 20 healthy control dogs of similar weight and age before and 3 weeks after being given one dose of doxorubicin (30 mg/m² intravenously). The administration of doxorubicin to control dogs resulted in a significant (P> .05) decrease in T-CH, LDL-CH, and HDL-CH, as well as a significant increase in VLOL-TG and HDL-TG. When compared with untreated controls, untreated dogs with lymphoma had significantly higher concentrations of VLDL-CH, T-TG, VLDL-TG, LDL-TG, and HDL-TG, and significantly lower concentrations of HDL-CH. HDL-TG and VLDL-TG concentrations from dogs with lymphoma were significantly increased above pretreatment values after relapse and development of overt signs of cancer cachexia. Dogs in remission that were evaluated after one dose of doxorubicin had significantly higher concentrations of T-CH, VLDL-CH, T-TG, and LDL-TG when compared with controls that were evaluated after an identical dose of doxorubicin. HDL-TG increased significantly over pretreatment values in dogs with lymphoma after doxorubicin therapy. These results suggest that dogs with lymphoma have significant alterations in lipid profiles, and with the possible exception of HDL-CH, these abnormalities do not normalize when clinical remission is obtained.     

Changing adrenergic sensitivity of the caruncular arterial vasculature supplying the bovine placentome

With the advancement of gestation, blood flow increases preferentially to the caruncular bed of the gravid uterus in association with a decreasing sensitivity of the uterus to the vasoconstrictive effects of circulating catecholamines. This study directly compared the sensitivity of the caruncular artery (CA) of the isolated bovine placentome to phenylephrine (PE), a specific alpha 1-adrenergic receptor (AR) agonist, with that to norepinephrine (NE) and epinephrine (E), both of which are alpha 1-, alpha 2-, and beta-AR agonists, at two stages of gestation (140 to 170 d, mid-pregnant; 210 to 270 d, late pregnant). The CA of each placentome was perfused with oxygenated Krebs Ringer solution into which PE, NE or E were administered; increases in intra-arterial pressure were recorded. Further, NE content and numbers of alpha 1- and alpha 2-AR in the CA, intercaruncular arteries (ICA) and uterine arteries (UA) were quantitated. The CA from mid-pregnant cows exhibited greater (P less than .05) contractile responses to NE and E than did the CA from late pregnant cows, whereas responsiveness to PE remained constant. No difference in NE content, alpha 1-AR or alpha 2-AR numbers were observed in the UA, ICA or CA between mid-pregnant or late pregnant cows. Alpha 1-AR numbers were similar in CA, ICA and UA. However, CA contained threefold greater alpha 2-AR numbers than either the ICA or UA (50.2 +/- 6.1 vs 14.6 +/- 1.6 and 14.8 +/- 2.4 fmol/mg protein, respectively; P less than .01).(ABSTRACT TRUNCATED AT 250 WORDS)     

The development of a screening method to estimate contact toxicity of pyrethroids against wood-boring marine crustacea,Limnoria spp.

A bioassay method has been developed for the screening of pyrethroids for contact toxicity against Limnoria species which should prove suitable for insecticides with low water-solubility. Less than 1% of a topically applied dose of cypermethrin (4.8 ng per isopod) was lost to the sea-water from the body surface; the pharmacokinetics of cypermethrin in the isopod accounted for the fate of the remainder. LD₅₀ parameter estimates obtained by this method represent measurements of absolute toxicity; NRDC 161^b proved the most effective of three pyrethroids tested.     

Ovarian follicular changes after weaning in sows.

Three experiments investigated ovarian follicular development in sows whose litters were weaned at 28 to 31 d of lactation. Unilateral ovariectomy near the time of weaning was used to assess early follicular characteristics and to identify those sows that would not return to estrus within 10 d after weaning. This allowed segregation of and exclusion from the study those sows that had a prolonged interval from weaning to first estrus. In Exp. 1, 82 and 72% of the large follicles that were marked at 48 or 72 h after weaning (10 sows per time point) were subsequently identified as corpora lutea. In Exp. 2, sows (seven to nine per time point) were unilaterally ovariectomized at 0, 6, 12, 18, 24, or 48 h after weaning, and follicular fluid was evaluated for changes in steroid concentrations. Progesterone concentrations in fluid from medium-sized (4 to 6 mm) follicles increased by 6 h after weaning and then declined through 24 h concomitant with increases in testosterone and estradiol. For Exp. 3, follicular fluid and granulosa cells from individual follicles were obtained from sows (seven to nine per time point) at 0, 6, and 24 h after weaning. In follicular fluid, insulin-like growth factor I (IGF-I) concentrations were not correlated (P greater than .05) with concentrations of progesterone, testosterone, or estradiol, or with granulosa cell production of estradiol during culture in androstenedione-supplemented medium.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of pretreatment with hepatic microsomal enzyme inducers on the toxicity of diazinon in calves

The pretreatment of calves with a single dose of 10 mg kg-1 dieldrin or 21 daily doses of 10 mg kg-1 phenobarbitone increased the toxicity of diazinon as reflected by the development of more severe clinical signs and greater depression in whole blood cholinesterase activity in the pretreated calves. Induction by dieldrin or phenobarbitone of the hepatic microsomal enzyme amidopyrine-N-demethylase was also accompanied by a concurrent rise in the liver carboxylesterase activity.