Disposition kinetics of tylosin administered intravenously and intramuscularly to pigs

The distribution of tylosin was studied using a crossover design, in six pigs following i.v. and i.m. administration of 10 mgkg(-1) b.w. Plasma samples were analysed by HPLC and UV absorbance detection. After i.v. administration, t(1/2beta) was 271.3 min, V(d) 14.6 Lkg(-1), V(ss) 9.7 Lkg(-1) and CL 26.8 mLmin(-1)kg(-1). After i.m. administration, a C(max) of 1 microgmL(-1) was reached at 90 min. Mean absorption time was 1988.7 min and bioavailability was 95%.     

A cross-sectional coprological survey of liver flukes in cattle and sheep from an area of the southern Italian Apennines

A cross-sectional coprological survey of liver flukes (Fasciola hepatica and Dicrocoelium dendriticum) was conducted on 81 bovine farms and 197 ovine farms with animals pasturing in an area (3971 km(2)) of the southern Italian Apennines. The farms were selected to be uniformly distributed throughout the study area using geographical information system (GIS) software. Between June 1999 and March 2000, faecal samples were collected from 975 cattle and 3940 sheep and examined using a modified McMaster technique. The results were subjected to statistical analysis and point distribution maps (PDMs) were drawn by GIS.Cattle of 9 of the 81 (11.1%) farms were positive for F. hepatica and of 43 (53.1%) for D. dendriticum. Sheep of 8 of the 197 (4.1%) farms were positive for F. hepatica and of 133 (67.5%) for D. dendriticum. Co-infection was found in cattle of 2 (2.5%) farms, and in sheep of 8 (4.1%) farms.The findings of the present survey show that D. dendriticum was the predominant liver fluke found in cattle and sheep with respect to egg count numbers for both farms and animals. In addition, the general trends of the PDMs show that D. dendriticum was widely and homogeneously spread throughout the study area, whereas F. hepatica was present only in a few concentrated zones of the study area that had both positive bovine and positive ovine farms.     

Hosts,seasonal occurrence and life cycle of Rhipicentor nuttalli (Acari: Ixodidae)

There are only two species worldwide within the genus Rhipicentor, namely Rhipicentor bicornis and Rhipicentor nuttalli and both occur only in Africa. Rhipicentor nuttali has a widespread distribution in South Africa and the present investigation was initiated to elucidate its host preference, seasonality and life cycle. Rock elephant shrews, Elephantulus myurus were examined for ticks at four localities in the Free State Province, one in Gauteng Province and two in Limpopo Province, South Africa. Cape elephant shrews, Elephantulus edwardii were examined at two places in the Western Cape Province, and a single specimen of the bushveld elephant shrew, Elephantulus intufi was examined in central Namibia. Small mammals of other species were also examined at two of these localities. The majority of E. myurus at two sites in the Free State, at the locality in Gauteng and both sites in Limpopo Province were infested with larvae and/or nymphs of R. nuttalli, while the single E. edwardii examined at one site in the Western Cape Province and the single E. intufi examined in Namibia were infested with nymphs of this tick. Not one of the other small animals was infested. Although larvae and nymphs of R. nuttalli were present on E. myurus throughout the year, the former were generally most numerous during the period March to September, and the latter during May to October. The preferred hosts of the adults are domestic dogs, leopards, Panthera pardus and South African hedgehogs, Atelerix frontalis. Adult females engorged on Atelerix frontalis in 16-32 days and, after a preoviposition period of 2-4 days, produced approximately 170,00 eggs during the following 60-70 days. The average incubation period of the eggs was 59 days. Larvae engorged on E. myurus in 4-10 days and moulted to nymphs 12-20 days later. Nymphs required 11-15 days to engorge on E. myurus and moulted to adults 32-47 days later. Allowing 14 days for the exoskeletons and mouthparts of each of the three parasitic stages to harden before they can attach to a host, the life cycle took approximately 214 days to complete in the laboratory. The length of this period, considered in conjunction with the times of maximum seasonal occurrence of the immature stages, indicates that the life cycle probably takes a year to complete in the field.     

The gamma-interferon test: its usefulness in a bovine tuberculosis survey in African buffaloes (Syncerus caffer) in the Kruger National Park

A survey to determine the bovine tuberculosis status of buffalo herds north of the Olifants River in the Kruger National Park was conducted, using a new diagnostic approach. Diagnosis of Mycobacterium bovis infection was accomplished using the gamma-interferon assay technique in 608 adult buffaloes out of a total of 29 discreet herds. The animals were immobilized in groups of 10-15, bled, individually marked and then revived and released on site. As soon as test results were available (after 26-36 h), the same buffalo herd was relocated by tracking the frequency of a radio-collar previously fitted to one adult cow per group during the initial operation. Bovine reactors were identified, darted and euthanased from the helicopter. Necropsy and culture findings of all culled buffaloes showed excellent correlation with the results of the ante-mortem gamma-interferon test. The survey revealed that over and above the two positive herds that had been identified during a previous survey carried out in 1996, there were three additional, but previously unidentified, infected herds in the region north of the Olifants River.     

Breed differences on the plasma availability of moxidectin administered pour-on to calves

The pharmacokinetic profile of avermectin and milbemycin compounds is affected by different drug- and host-related factors. This work reports the influence of cattle breeds on the plasma kinetics of moxidectin (MXD) after topical (pour-on) administration. Parasite-free Aberdeen Angus and Holstein calves were treated with a commercial MXD pour-on formulation at 500 microg/kg. Blood samples were collected over a period of 35 days post-treatment and the recovered plasma was analysed by high performance liquid chromatography using fluorescence detection. MXD was detected in plasma from two hours up to 35 days post-treatment in animals from both breeds. A slow MXD absorption and delayed peak plasma concentration were observed in Aberdeen Angus compared to Holstein calves. Significant lower systemic availability (expressed as AUC) (P<0.01) and peak plasma concentration (C(max)) (P<0.05) were also observed in Aberdeen Angus calves, although the plasma mean residence time (MRT) and elimination half-lives (T(1/2el)) of MXD in both breeds were similar. The pharmacokinetic differences observed between cattle breeds contribute to explain the variability in the pattern of clinical efficacy for pour-on administered endectocide compounds reported in different field trials.     

Comparison of nuclear morphometric parameters in cytologic smears and histologic sections of spontaneous canine tumors

Background — Nuclear morphometry may provide useful diagnostic and prognostic information for neoplasms in animals. Most available data have been obtained from histologic sections. Nuclear morphometry of cytologic smears may provide important pre-operative information.
Objectives — The goal of this study was to compare nuclear morphometric parameters in cytologic smears and histologic sections from spontaneous canine tumors.
Methods — Mean nuclear area (MNA), mean nuclear perimeter (MNP), mean nuclear form factor (FF; nuclear perimeter²/4π nuclear area) and their respective SDs were assessed by image analysis of both hematoxylin and eosin-stained histologic sections and May-Grünwald-Giemsa-stained cytologic smears from the same case in 20 spontaneous canine tumors of different histogenesis. The above parameters were selected as being the best morphometric tools for measuring variation in shape and size in cells after neoplastic transformation. Data were compared by ANOVA with P<.01 considered significant.
Results — There was a significant difference between histologic and cytologic specimens for MNA, MNP, and their SDs. Only the differences between FF and the SD of FF were not statistically significant.
Conclusions — Only nuclear morphometric data related to nuclear shape and nuclear shape variability are comparable between histologic and cytologic specimens. Nuclear area and perimeter may be affected by the different fixation and smear preparation techniques used in histology and cytology.     

A randomised,blinded, crossover study to assess the efficacy of a feed supplement in alleviating the clinical signs of headshaking in 32 horses

Reasons for performing study: Feed supplements are commonly used by owners to alleviate headshaking; however, randomised, controlled trials are required to assess their efficacy. Objective: To determine the efficacy of a feed supplement for alleviation of the clinical signs of headshaking using a randomised, blinded, placebo‐controlled trial. Methods: Using a crossover design, 44 horses previously diagnosed with chronic idiopathic headshaking received both the supplement and a matching placebo per os for 28 days with a washout period between of 14 days. Video recordings were taken at rest and exercise prior to the study and at the end of both periods of treatment. The degree of headshaking was assessed in a blinded, randomised manner by 2 veterinary surgeons. At the same time points, owners completed a questionnaire to assess the severity of headshaking signs. A Wilcoxon signed rank test was used to compare the scores while on supplement and placebo. Results: Using the video assessments, there was no significant difference between scores while on supplement compared with placebo (P = 0.7). Using the questionnaire responses, there was no significant difference between scores for any activity when the placebo and the supplement were compared with each other. However, owners reported significant improvement during all activities for both placebo and supplement compared with pretreatment scores. Conclusions and potential relevance: The supplement offered no benefit over a placebo in alleviating the clinical signs of headshaking. There appeared to be a significant proxy placebo effect when the outcome was based on subjective owner perception of clinical signs. This study demonstrated no beneficial effect of this supplement on the clinical signs of headshaking. The study did show a significant placebo effect, thereby highlighting the necessity of properly conducted, randomised controlled trials, with blinding, to assess true treatment effects in trials in animals.     

Serum chloramphenicol levels and the intramuscular bioavailability of several parenteral formulations of chloramphenicol in ruminants

Summary

Serum chloramphenicol concentrations were determined by microbiological and chemical assay methods in cows, ewes, and goats treated parenterally with seven different veterinary parenteral chloramphenicol products, including the water soluble sodium succinate ester of chloramphenicol and solutions of 20%, 25% and 50% of chloramphenicol base in various organic solvents. Serum drug concentrations were analyzed for the effect of product formulation differences, dosage, whether the drug was administered i.m. at a single body site or to two sites, and the method of assay, on the absorption from the injection site, peak drug levels, and the persistence in serum of effective concentrations of the drug i.e. 5 to 10 ug / ml. Although differences were observed among the 6 products containing chloramphenicol base in respect to absorption rate and peak serum drug levels, and although these differences significantly influenced the persistence of microbiologically‐active serum drug concentrations at the level of ≥ 10 μg / ml, they did not at the level of ≥ 5 μg / ml.

In the animal species examined, injections given at 2 sites appeared to influence the duration of predetermined serum drug levels more than the differences among the products in respect of the absorption and elimination rates from serum, the peak serum concentrations, and the dose. The shapes of the concentration‐to‐time curves in cows and ewes injected with the same dose of a given product were essentially the same, but they were different in goats. Serum chloramphenicol concentrations measured chemically after treatment with chloramphenicol base were 20% to 46% higher than those measured microbiologically.

For 60 minutes after the sodium succinate ester had been administered i.v. and i.m. to ewes, the chemically determined chloramphenicol levels were more than twice as high as the respective concentrations determined by microbiological assay, but thereafter, the magnitude of those differences was not greater than observed after treatment with chloramphenicol base.

Intramuscular bioavailability of the products containing chloramphenicol base injected at 2 sites was rather poor (51% to 80.5%ofthe dose) and even lower values were calculated after injection at a single site.

Results are briefly discussed of the effect of dosage form on the persistence of microbiologically effective serum drug levels. A dose of at least 50 mg / kg to be administered i.m. at two sites are essential prerequisits for chloramphenicol therapy in ruminants.     

Clinical Leptospira interrogans serogroup Australis serovar lora infection in a stud farm in the Netherlands

Summary

A Leptospira interrogans serogroup australis serovar lora infection in a stud farm is reported. During three successive years (1984–1986) clinical leptospirosis with a severe often rapid, fatal course was seen in 12 foals.

Clinical examination revealed severe respiratory distress, depression and pyrexia. Other symptoms were diarrhea (2), jaundice (1), and an unsteady gait (1). Morphological characteristics of the disease were massive pulmonary haemorrhage and haemorrhagicthrombotic or extracapillary glomerulonephritis with tubulonephrosis and interstitial oedema. In most foals high or increasing MAT titres to serovar bratislava were found; from one foal Leptospira interrogans serovar lora was isolated.

Serological examination of all 56 mares at the farm (August 1986) revealed antibodies to serovar bratislava in 64 per cent of the animals. These findings support the idea that Leptospira interrogans serovar bratislava and closely related strains (in this study serovar lora) may be adapted to and maintained by the horse population.     

Book Review

Agricultural landscapes are typically associated with a decreased biodiversity, particularly when they extend across large spatial scales. Despite the fact that some African bat species seem to provide essential ecosystem services across landscapes, we only have a limited understanding of how intensive agricultural practices influence bat communities. This study investigated the effects of sugarcane monoculture on the composition of both bat species and functional groups across a conservation-agricultural matrix. Specifically, we wanted to understand changes in the bat communities within savannas and sugarcane plantations. We categorised bats into broad foraging (functional) groups based on their echolocation call structure: open-air; clutter-edge; and, clutter. To measure bat activity, we established twelve 25 ha grids randomly located in savanna and sugarcane vegetation. Within each grid we placed nine acoustic detectors, in 3 × 3 formation, 250 m apart; totalling 54 plots in each land use. We sampled each plot over four nights (two in the wet season and two in the dry season) during a one-year period. We did not observe a significant difference in species richness between savanna and sugarcane. However, there was a difference in functional group composition. Sugarcane negatively affected clutter foragers; this group was practically absent here despite occurring within neighbouring savannas. We observed distinct patterns of seasonality in bat activity, with activity of all functional groups being reduced in the dry season.