Equine ehrlichial colitis (Potomac horse fever): recognition of the disease in Pennsylvania, New Jersey, New York, Ohio, Idaho, and Connecticut

Equine ehrlichial colitis (Potomac horse fever), a newly identified colitis of the horse, was first recognized in Maryland. In this report, we document occurrence of the disease in Pennsylvania, New Jersey, New York, Ohio, Idaho, and Connecticut. Enzootic areas were recognized by a characteristic pattern. Frequently there was a seasonal pattern and high prevalence of sporadic colitis in unstressed horses. The attack rate per farm generally was low. Horses on pasture, as well as those stabled, were affected. Clinical signs varied from fever and depression to severe diarrhea and laminitis. Occasionally horses developed profound ileus and severe colic. Diagnosis was based on detection of an increase or decrease in serum antibody titers to Ehrlichia risticii, using an indirect fluorescent antibody technique.     

Ketamine, Telazol, xylazine and detomidine. A comparative anesthetic drug combinations study in ponies.

This study was designed to assess the effects of 5 anesthetic drug combinations in ponies: (1) ketamine 2.75 mg/kg, xylazine 1.0 mg/kg (KX), (2) Telazol 1.65 mg/kg, xylazine 1.0 mg/kg (TX), (3) Telazol 2 mg/kg, detomidine 20 micrograms/kg (TD-20), (4) Telazol 2 mg/kg, detomidine 40 micrograms/kg (TD-40), (5) Telazol 3 mg/kg, detomidine 60 micrograms/kg (TD-60). All drugs were given iv with xylazine or detomidine preceding ketamine or Telazol by 5 min. Heart rate was decreased significantly from 5 min to arousal after TD-20 but only at 60 and 90 min after TD-40 and TD-60 respectively. Respiratory rate was decreased significantly for all ponies. Induction time did not differ between treatments. Duration of analgesia was 10 min for KX, 22.2 min for TX, 27.5 min for TD-20, 32.5 min for TD-40, and 70 min for TD-60. Arousal time was significantly longer with detomidine and Telazol. Smoothness of recovery was judged best in ponies receiving KX and TD-40. All ponies stood unassisted 30 min after signs of arousal.     

Differences among restriction endonuclease DNA fingerprints of Pennsylvania field isolates, vaccine strains, and challenge strains of infectious laryngotracheitis virus.

Restriction endonuclease fingerprints of infectious laryngotracheitis virus (ILTV) DNA from 13 Pennsylvania field isolates, embryo-propagated and tissue-culture-propagated vaccine strains, and three reference strains were compared. These comparisons were made to evaluate the possible contribution of mutation of ILTV vaccine strains to recent outbreaks of infectious laryngotracheitis (ILT) in Pennsylvania. Six different restriction enzymes were used to generate the fingerprints. Differences in DNA banding patterns were revealed between the currently used ILTV vaccine strains and six of the 13 field isolates. Even greater DNA banding pattern differences were found between the older ILTV reference strains and the vaccine strains. The ILTV DNA fingerprints generated in the present study suggest that at least five different strains of ILTV have contributed to the outbreaks of ILT that have occurred since 1987 in Pennsylvania.     

Advantages and guidelines for using alpha-2 agonists as anesthetic adjuvants.

Xylazine and medetomidine produce reliable sedation, muscle relaxation, and analgesia in dogs and cats. In addition, alpha-2 agonists have proved very effective as sedative-analgesic adjuncts when coadministered with benzodiazepine or opioid agonists. Alpha-2 agonists should not be classified as monoanesthetics. They are excellent anesthetic adjuncts when combined with dissociatives and opioids. Because of the acute alterations in cardiopulmonary function commonly induced by alpha-2 agonists, it is suggested that their use be restricted to the young healthy patient undergoing routine surgical or diagnostic procedure. The development of more specific and selective alpha-2 agonists will continue to enhance the safety and reliability of this novel class of compounds. The unique spectrum of anesthetic properties induced by alpha-2 agonists has assured them of an increasingly prominent role in the development of new and sophisticated ways of achieving anesthesia.     

Radiographic characterization of diaphragmatic excursion in halothane anesthetized ponies: Effect of mode of ventilation and muscle paralysis

A radiographic technique was used to identify and characterize segmental diaphragmatic movement in anesthetized ponies breathing spontaneously and with controlled ventilation with and without muscle relaxant-induced paralysis. Paralyzed mechanically ventilated ponies were also studied at varying peak inspiratory pressures. Controlled ventilation induced a change in pattern of diaphragmatic displacement which was accentuated by paralysis and increased inspiratory pressure. In conclusion, these results indicate that uneven distribution of inspired gases is not corrected by mechanical ventilation. Furthermore, increased tidal volume during mechanical ventilation is largely wasted because this increased volume is distributed principally to the poorly perfused nondependent lung. Thus, while mechanical ventilation can alleviate hypoventilation, i.e., will decrease P_aCO₂, it will be of limited value in relieving arterial hypoxemia due to venous admixture in anesthetized patients.     

Comparative ester hydrolysis of carbaryl and ethiofencarb in four mammalian species

The comparative ester hydrolysis and selective toxicity of carbamate insecticides were studied in four mammalian species. Hydrolysis rates of carbaryl and ethiofencarb (Croneton) were examined in the rat, mouse, guinea pig, and gerbil. Respiratory ¹⁴CO₂ resulting from the hydrolysis of orally administered [carbonyl-¹⁴C]carbamates (0.2 mg/kg) was taken as measure of in vivo hydrolytic capabilities. Ester hydrolysis was found to be greater for ethiofencarb than for carbaryl in all species tested, although the relative order of hydrolysis among species was the same with both compounds. After 24 hr, gerbils had hydrolyzed 91% of the ethiofencarb and 65% of the carbaryl. Guinea pigs hydrolyzed somewhat less of the compounds, 65 and 58%, but considerably more than rats and mice, about 40 and 25%. Comparing hydrolysis capabilities to acute toxicity data revealed that those species exhibiting the greatest hydrolysis were equally or more susceptible to carbamate poisoning than those having lesser hydrolytic capabilities. While ester hydrolysis destroys the anticholinesterase activity of carbamates, it is clear from these findings that factors other than hydrolysis are largely responsible for the variation in toxicity of the carbamates to different mammalian species.     

Ultrastructural and functional correlates of increased luteinizing hormone synthesis and secretion in castrated male mice.

The changes in the ultrastructure of gonadotrops and in the plasma levels of LH were studied three, five, seven, ten, twenty and forty days after castration in adult male mice. Gonadotrops in sham operated animals contained numerous granules and moderately developed synthetic organelles. Castration induced mobilization of the secretory granules at three days, and degranulation of gonadotrops and a hypertrophy of the synthetic organelles at seven days. By ten days after castration gonadotrops were greatly enlarged, while in addition at forty days they frequently contained large cytoplasmic vesicles filled with lipid-like material. These changes were paralleled by an initial three fold increase in serum LH three days after castration, and a further ten fold increase in the levels of the hormone forty days after castration. In conclusion, the castration-induced morphologic changes in gonadotrops correlate well with increased release of LH. The subtle differences in the control of timing of LH secretion in mice and rats are discussed. A trans-cytoplasmic route for rapid transport of gonadotropic hormones in the mouse is postulated, and the significance of cytoplasmic vesicles in the castrate discussed.     

Pharmacokinetics of imipenem-cilastatin following intravenous administration in healthy adult horses

In two studies, six healthy adult horses were given imipenem-cilastatin by slow intravenous (i.v.) infusion at an imipenem dosage of 10 mg/kg (study 1) and 20 mg/kg (study 2). The same horses were used in each dosage schedule, with a 2-week washout period between studies. In each dosage group, serial blood and synovial fluid samples were collected for 6 h after completion of the infusion. HPLC was used to determine the imipenem concentration in all samples. Imipenem was well tolerated by all horses at both dosages; no adverse effects were noted during the study period or during the 24-hour postinfusion observation period. The pharmacokinetic profiles of imipenem in the plasma and synovial fluid indicate that an imipenem dosage of 10-20 mg/kg by slow i.v. infusion q6h (every 6 h) is appropriate for most susceptible pathogens.     

Disseminated Acanthamoeba sp. infection in a dog

Several species of free-living amoebae can cause encephalomyelitis in animals and humans. Disseminated acanthamoebiasis was diagnosed in pyogranulomatous lesions in brain, thyroid, pancreas, heart, lymph nodes, and kidney of a one-year-old dog. Acanthamoeba sp. was identified in canine tissues by conventional histology, by immunofluorescence, by cultivation of the parasite from the brain of the dog that had been stored at -70 degrees C for two months, and by PCR. The sequence obtained from the PCR product from the amoeba from the dog was compared to other sequences in the Acanthamoeba sp. ribosomal DNA database and was determined to be genotype T1, associated with other isolates of Acanthamoeba obtained from granulomatous amebic encephalitis infections in humans.