Evaluation of the clinical efficacy of a water soluble formulation of tylvalosin in the control of enzootic pneumonia associated with Mycoplasma hyopneumoniae and Pasteurella multocida in pigs.

BACKGROUND: The efficacy of a water soluble formulation of tylvalosin (Aivlosin® 625 mg/g granules) was evaluated in the treatment and metaphylaxis of Enzootic Pneumonia (EP) in pigs. In all four trials, pigs in the tylvalosin group were administered 10 mg tylvalosin/kg bodyweight in drinking water daily for 5 consecutive days (TVN). In a single-challenge study, pigs were inoculated with lung homogenate containing Mycoplasma hyopneumoniae. In a dual challenge study, pigs were sequentially inoculated with pure culture of M. hyopneumoniae and Pasteurella multocida. Efficacy was evaluated based on reduction of lung lesions compared to unmedicated control pigs (CTL). In two field studies at European commercial farms with confirmed outbreaks of EP, treatment efficacy in clinically affected fatteners was evaluated based on improved clinical conditions compared to pigs treated with tylosin at 10 mg/kg by injection for 3 consecutive days (TYL). In these field trials, healthy in contact pigs were enrolled for metaphylaxis efficacy evaluation based on reduction in incidence of new clinical cases of respiratory disease compared to unmedicated pigs (CTL). RESULTS: In the M. hyopneumoniae-only challenge study, pigs in TVN group had lower lung lesion scores than CTL (6.52 vs. 14.97; p <  0.001). In the dual challenge study with M. hyopneumoniae and P. multocida, pigs in TVN group had lower lung lesion scores than CTL (3.32 vs. 8.37; p <  0.01) and the recovery of both challenge bacteria from the lungs was lower in TVN compared with CTL group (p <  0.01). In field outbreaks of EP, multicentre analysis showed that 13 days after the start of medication, treatment success for TVN pigs was significantly better than for TYL pigs (80.0% vs 48.7% p = 0.03) and metaphylactic administration of TVN significantly reduced the incidence of new clinical cases (2.1% vs. 7.8%; p <  0.01) compared with unmedicated controls. CONCLUSIONS: Tylvalosin at 10 mg/kg daily for 5 days in drinking water was safe and effective in the treatment and metaphylaxis of EP in pigs associated with infections of M. hyopneumoniae either alone or in combination with P. multocida under both experimental challenge and field natural infection conditions.

Evidence that an internal schema adapts swallowing to upper airway requirements.

KEY POINTS: To swallow food and liquid safely, airway protection is essential. Upward and forward movements of the hyoid and larynx in the neck during swallowing vary in magnitude between individuals. In healthy human adults, hyoid and laryngeal movements during swallowing were scaled by differences in initial upper airway area before swallowing. Individuals increased laryngeal elevation during swallowing in response to increased airway opening before swallowing. We show that when upper airway protection requirements change, individuals use an internal sensorimotor scaling system to adapt movements to maintain swallow safety. ABSTRACT: Hyoid and laryngeal movements contribute to laryngeal vestibule closure and upper oesophageal sphincter opening during swallowing. Evidence of an internal sensorimotor scaling system allowing individuals to achieve these functional goals is lacking. In speech, speakers adjust their articulatory movement magnitude according to the movement distance required to reach an articulatory target for intelligible speech. We investigated if swallowing is similar in that movement amplitude may be scaled by the functional goal for airway protection during swallowing, rather than by head and neck size. We hypothesized that healthy individuals adapt to their own anatomy by adjusting hyo-laryngeal movements to achieve closure of the upper airway. We also investigated if individuals would automatically compensate for changes in their initial hyo-laryngeal positions and area when head position was changed prior to swallowing. Videofluoroscopy was performed in 31 healthy adults. Using frame-by-frame motion analysis, anterior and superior hyoid and laryngeal displacement, and hyo-laryngeal area were measured prior to and during swallowing. Kinematic measurements during swallowing were examined for relationships with pharyngeal neck length, and initial hyo-laryngeal positions, length and area before swallowing. During swallowing, individuals altered laryngeal elevation magnitude to exceed hyoid elevation based on hyo-laryngeal length before swallowing. Anterior laryngeal displacement was related to initial larynx distance from the spine, while hyoid elevation was predicted by pharyngeal neck length and initial hyoid distance from the mandible prior to the swallow. In conclusion, individuals automatically adapt hyo-laryngeal movement during swallowing based on targets required for closing the hyo-laryngeal area for safe swallowing.

The lethal fungus Batrachochytrium dendrobatidis is present in lowland tropical forests of far eastern Panamá.

The fungal disease chytridiomycosis, caused by Batrachochytrium dendrobatidis (Bd), is one of the main causes of amphibian population declines and extinctions all over the world. In the Neotropics, this fungal disease has caused catastrophic declines in the highlands as it has spread throughout Central America down to Panamá. In this study, we determined the prevalence and intensity of Bd infection in three species of frogs in one highland and four lowland tropical forests, including two lowland regions in eastern Panamá in which the pathogen had not been detected previously. Bd was present in all the sites sampled with a prevalence ranging from 15-34%, similar to other Neotropical lowland sites. The intensity of Bd infection on individual frogs was low, ranging from average values of 0.11-24 zoospore equivalents per site. Our work indicates that Bd is present in anuran communities in lowland Panamá, including the Darién province, and that the intensity of the infection may vary among species from different habitats and with different life histories. The population-level consequences of Bd infection in amphibian communities from the lowlands remain to be determined. Detailed studies of amphibian species from the lowlands will be essential to determine the reason why these species are persisting despite the presence of the pathogen.

Mycoplasma gallisepticum in pheasants and the efficacy of tylvalosin to treat the disease.

Infectious sinusitis, a common condition seen in adult pheasants, is primarily caused by Mycoplasma gallisepticum. The aims of the present study were to investigate the pathogenicity of M. gallisepticum in 14-day-old pheasants and evaluate the macrolide antibiotic tylvalosin (TVN) as a treatment for infectious sinusitis. The minimum inhibitory concentration of TVN for five isolates of M. gallisepticum taken from pheasants confirmed their susceptibility to TVN (range: 0.002 to 0.008 µg/ml). One of the isolates (G87/02) was inoculated intranasally into 72 pheasants (two groups of 36) at 14 days of age. Eight days later, when 18/72 (25%) of the pheasants showed clinical signs, one group was treated with 25 mg TVN/kg bodyweight daily in drinking water for three consecutive days. An uninfected, unmedicated control group (n=12) was also included. In contrast to the uninfected control group, a range of clinical signs typical of infectious sinusitis with varying severity was observed in challenged birds and M. gallisepticum was re-isolated from the infraorbital sinus and the eye/conjunctiva at necropsy, 22 days post challenge. In comparison with untreated birds, medication with TVN significantly reduced clinical signs and the re-isolation/detection of M. gallisepticum (P≤0.0021). The daily liveweight gain of treated birds was significantly increased in comparison with untreated birds (P=0.0002), and similar to daily liveweight gains observed in the uninfected control group. In conclusion, TVN at 25 mg/kg bodyweight daily for three consecutive days in drinking water was efficacious in the treatment of M. gallisepticum infection induced by challenging 14-day-old pheasants.

Towards a better understanding of the use of probiotics for preventing chytridiomycosis in Panamanian golden frogs.

Populations of native Panamanian golden frogs (Atelopus zeteki) have collapsed due to a recent chytridiomycosis epidemic. Reintroduction efforts from captive assurance colonies are unlikely to be successful without the development of methods to control chytridiomycosis in the wild. In an effort to develop a protective treatment regimen, we treated golden frogs with Janthinobacterium lividum, a skin bacterium that has been used to experimentally prevent chytridiomycosis in North American amphibians. Although J. lividum appeared to colonize A. zeteki skin temporarily, it did not prevent or delay mortality in A. zeteki exposed to Batrachochytrium dendrobatidis, the causative agent of chytridiomycosis. After introduction of J. lividum, average bacterial cell counts reached a peak of 1.7 × 10(6) cells per frog ~2 weeks after treatment but declined steadily after that. When J. lividum numbers declined to ~2.8 × 10(5) cells per frog, B. dendrobatidis infection intensity increased to greater than 13,000 zoospore equivalents per frog. At this point, frogs began to die of chytridiomycosis. Future research will concentrate on isolating and testing antifungal bacterial species from Panama that may be more compatible with Atelopus skin.