Activity of clarithromycin or rifampin alone or in combination against experimental Rhodococcus equi infection in mice.

Treatment of mice with the combination of clarithromycin with rifampin resulted in a significantly lower number of Rhodococcus equi CFU in the organs of mice than treatment with either drug alone or placebo. There was no significant difference in the number of R. equi CFU between mice treated with clarithromycin monotherapy, rifampin monotherapy, or placebo. The combination of clarithromycin with rifampin conferred a clear advantage over either drug as monotherapy in this model of chronic R. equi infection.

Successful use of intravenous and oral levetiracetam in a goat to control refractory seizures secondary to suspected polioencephalomalacia.

OBJECTIVE: To assess the clinical efficacy and plasma concentrations of levetiracetam in a goat with seizures. ANIMAL: A 5-month-old doeling. CLINICAL PRESENTATION, PROGRESSION, AND PROCEDURES: The goat was referred because of progressive anorexia and lethargy over 3 days. Clinical signs consisted of weakness, obtundation, opisthotonos, anisocoria, and cortical blindness. Initial evaluation was most consistent with polioencephalomalacia. TREATMENT AND OUTCOME: Neurologic improvement occurred within 4 hours of thiamine administration, with appetite returning over 12 hours. On day 3 of hospitalization, the goat suffered acute onset repetitive seizures that were incompletely responsive to standard interventions over 3 hours. Administration of IV levetiracetam (60 mg/kg) produced resolution of seizure activity within 20 minutes. Levetiracetam was continued twice daily IV, then PO after day 6. Plasma concentrations were above or within therapeutic ranges (5 to 45 µg/mL) as previously established for other species, following both IV and PO levetiracetam. Oral administration (60 mg/kg, PO, q 12 h) resulted in plasma levetiracetam concentrations of 48.1 µg/mL 2 hours after a dose and 23.4 µg/mL 2 hours prior to the next dose. CLINICAL RELEVANCE: Levetiracetam is a newer anticonvulsant commonly used in humans and small animals due to its efficacy, cost, and wide safety margin. Its use has not previously been reported in domestic small ruminants. In this case, levetiracetam showed excellent clinical efficacy in the face of refractory seizures, with no apparent side effects. Plasma concentrations during oral administration were at the high end of the therapeutic range, indicating absorption in a nonmonogastric species. Further studies are warranted to determine optimal dosing in small ruminants.

Macrolide- and rifampin-resistant Rhodococcus equi on a horse breeding farm, Kentucky, USA.

Macrolide and rifampin resistance developed on a horse breeding farm after widespread use was instituted for treatment of subclinical pulmonary lesions in foals. Resistance occurred in 6 (24%) of 25 pretreatment and 8 (62%) of 13 (62%) posttreatment isolates from affected foals. Drug-resistant isolates formed 2 distinct genotypic clusters.

Description of fecal shedding of Cryptosporidium parvum oocysts in experimentally challenged dairy calves.

The objective was to describe the probability of Cryptosporidium parvum fecal oocyst shedding at different magnitudes of exposure, the pattern of fecal shedding over time, and factors affecting fecal shedding in dairy calves. Within the first 24 h of life, 36 calves were experimentally challenged with C. parvum oocysts at one of four possible magnitudes of oral exposure (1 × 10(3), 1 × 10(4), 1 × 10(5), and 1 × 10(6) oocysts), and 7 control calves were sham dosed. Fecal shedding occurred in 33 (91.7 %) experimentally challenged calves and in none of the control calves. There was a difference in the log-total number of oocysts counted per gram of feces dry weight among the four exposure groups; calves with the lowest magnitude of exposure (1 × 10(3) oocysts) shed less than the other three groups. At higher magnitudes of exposure, there was more variability in the range of fecal oocyst shedding. There was an inverse relationship between the log-total amount of oocysts counted per gram of feces dry weight and the number of days to the onset of fecal shedding per calf, i.e., the more time that elapsed to the onset of fecal shedding, the fewer oocysts that were shed. The pattern of fecal shedding over time for all calves shedding oocysts was curvilinear; the number of oocysts increased with time, reached a peak, and declined. Therefore, the dynamics of oocyst shedding can be influenced in part by limiting exposure among calves and delaying the onset of fecal oocyst shedding.

Prognostic indicators for nonambulatory cattle treated by use of a flotation tank system in a referral hospital: 51 cases (1997-2008).

OBJECTIVE: To evaluate clinical variables assessed during the first 24 hours of hospitalization as prognostic indicators for nonambulatory cattle treated by use of a flotation tank. DESIGN: Retrospective case series. ANIMALS: 51 nonambulatory cattle that underwent flotation treatment. PROCEDURES: Signalment, history, serum biochemical analyses, patient behavior during flotation, and outcome data were collected from medical records. Outcome was survival to discharge from the hospital or nonsurvival (death or euthanasia). Data were analyzed by use of Wilcoxon rank sum, Fisher exact, and chi(2) tests. RESULTS: 19 of 51 cattle survived. Survivors and nonsurvivors did not differ significantly with regard to median weight; age; stage of lactation; duration of recumbency prior to flotation; serum potassium, ionized calcium, or phosphate concentrations at admission to the hospital; or serum creatine kinase activity (value at admission to the hospital, highest value, and last recorded value). Cattle that were able to walk out of the tank after the first flotation treatment were 4.8 times as likely to survive as those that could not. Cattle that did not eat during flotation treatment were 1.9 times as likely to die as those that ate. Cattle that stood apparently normally on all limbs during the first flotation treatment were 2.9 times as likely to survive as those that had an asymmetric stance or were unable to stand. CONCLUSIONS AND CLINICAL RELEVANCE: Results indicated that objective variables evaluated during the first 24 hours of hospitalization and flotation treatment are associated with outcome among nonambulatory cattle; findings might assist in logical decision making with respect to treatment options.

Efficacy of liposomal gentamicin against Rhodococcus equi in a mouse infection model and colocalization with R. equi in equine alveolar macrophages.

Rhodococcus equi, a facultative intracellular pathogen and an important cause of pneumonia in foals, is highly susceptible to killing by gentamicin in vitro. However, gentamicin is not effective in vivo, due to its poor cellular penetration. Encapsulation of drugs in liposomes enhances cellular uptake. The objectives of this study were to compare liposomal gentamicin and free gentamicin with respect to their uptake by equine macrophages and intracellular colocalization with R. equi and to compare the efficacies of liposomal gentamicin, free gentamicin and clarithromycin with rifampin for the reduction of R. equi CFU in a mouse model of infection. After ex vivo exposure, a significantly higher mean (±SD) percentage of equine alveolar macrophages contained liposomal gentamicin (91.9±7.6%) as opposed to free gentamicin (16.8±12.5%). Intracellular colocalization of drug and R. equi, as assessed by confocal microscopy, occurred in a significantly higher proportion of cells exposed to liposomal gentamicin (81.2±17.8%) compared to those exposed to free gentamicin (10.4±8.7%). The number of R. equi CFU in the spleen was significantly lower in mice treated with liposomal gentamicin compared to that of mice treated with free gentamicin or to untreated control mice. Treatment with liposomal gentamicin also resulted in a significantly greater reduction in the number of R. equi CFU in the liver compared to treatment with clarithromycin in combination with rifampin. These results support further investigation of liposomal gentamicin as a new treatment for infections caused by R. equi.

Spiral colon impaction in juvenile alpacas: 12 cases (2006-2010).

OBJECTIVE: To describe clinical signs and treatment outcomes for juvenile alpacas with spiral colon impaction (SCI). DESIGN: Retrospective case series. Animals-12 juvenile (< 6 months old) camelids with SCI. PROCEDURES: Crias with SCI were identified by searching the medical records database of the Cornell University Equine and Farm Animal Hospital. A keyword-based search method was used. Inclusion required confirmation of SCI on the basis of surgical or necropsy findings. History, signalment, examination findings, diagnostic test results, medical treatments, and surgical reports as well as short- and long-term outcomes were reviewed. Peritoneal fluid parameters were compared with those of age-matched comparison crias in which SCI was suspected but ruled out at necropsy or exploratory celiotomy. RESULTS: 12 crias with confirmed SCI were identified. Common clinical signs included lethargy and diarrhea. Abdominal distention was observed in 9 crias. In 3 crias, a mass in the region of the spiral colon was palpated. Seven crias underwent peritoneal fluid analysis; compared with age-matched comparison crias, SCI-affected crias had higher peritoneal fluid nucleated cell counts and nucleated cell count-to-total protein concentration ratios. A ventral midline celiotomy was performed in 9 crias; 7 underwent an enterotomy, and 2 underwent transmural infusion of saline (0.9% NaCl) solution with manual breakdown of ingesta; 3 of these crias survived for at least 6 months. CONCLUSIONS AND CLINICAL RELEVANCE: Crias with SCI that were not resolved by medical management had a poor prognosis. During celiotomy, transmural infusion of saline solution with manual breakdown of ingesta provided a less invasive alternative to enterotomy.

Fecal shedding of Cryptosporidium oocysts in healthy alpaca crias and their dams.

OBJECTIVE: To determine the apparent prevalence of shedding of Cryptosporidium spp in healthy alpaca crias and their dams on 14 farms in New York and 1 farm in Pennsylvania. DESIGN: Cross-sectional study. ANIMALS: 110 alpaca crias and their 110 dams. PROCEDURES: Fecal samples were obtained from 220 alpacas at 14 alpaca farms in New York and 1 farm in Pennsylvania. For each animal, age, sex, and health condition were recorded. A fecal score (1 = normally formed; 2 = soft or loose; 3 = diarrhetic) was recorded for each cria. Cryptosporidium oocysts were identified in fecal samples by a direct immunofluorescence assay. RESULTS: Apparent prevalence of fecal shedding of Cryptosporidium oocysts was 8% (95% confidence interval, 4% to 15%) in dams and was 7% (95% confidence interval, 3% to 13%) in crias. There was no significant difference in age between dams with positive fecal test results for Cryptosporidium oocysts (median age, 4 years; range, 3 to 8 years) and dams with negative results (median age, 4 years; range, 2.5 to 19 years). No significant difference was found in age between crias with positive fecal test results (median age, 20 days; range, 7 to 53 days) and those with negative results (median, 36 days; range, 2 to 111 days). No significant difference in fecal scores was found between crias with positive versus negative fecal test results. CONCLUSIONS AND CLINICAL RELEVANCE: A higher than previously reported apparent prevalence of fecal shedding of Cryptosporidium oocysts in healthy alpacas was found. A zoonotic risk should be considered, especially for Cryptosporidium parvum.