Duration of Mycoplasma hyopneumoniae Infection in Gnotobiotic Pigs

Sixteen gnotobiotic pigs raised in flexible plastic isolators (four pigs per isolator) were inoculated with a culture of Mycoplasma hyopneumoniae. One pig was killed and underwent necropsy at weekly intervals for the following 16 weeks. Macroscopic lesions were observed in the lungs of 13 of 16 pigs and microscopic lesions were found in 14 of 16 pigs. Mycoplasma hyopneumoniae was cultured from the trachea or lungs from 10 of the 16 pigs. Scanning electron microscope studies showed areas of damage to the cilia, collections, of leucocytes and mucus, and mycoplasma in the trachea as well as the bronchi. These conditions were found in all the pigs seen at necropsy from nine to 16 weeks postinoculation and there was no evidence of noticeable regression or recovery during this 16 week period.     

The effects of antigenic competition on the efficacy of multivalent footrot vaccines

SUMMARY A multivalent footrot vaccine has been developed, containing pilus antigens produced in recombinant Pseudomonas aeruginosa and representing all nine serogroups of Dichelobacter (Bacteroides) nodosus commonly recognised in the field. The responses of sheep to the multivalent vaccine have been compared with those to monovalent vaccines representing only a single serogroup. Antigenie competition between serogroups occurred in sheep immunised with the multivalent formulation, but high levels of protection were still achieved. The study showed that in multivalent footrot vaccines, antigenic competition is predominantly due to the presence of a family of immunologically-related pilus antigens rather than to interference by extraneous proteins.     

Further investigation of lead exposure as a potential threatening process for a scavenging marsupial species

There is a growing recognition of the harmful effects of lead exposure on avian and mammalian scavengers. This can lead to both lethal and non-lethal effects which may negatively impact wildlife populations. Our objective was to assess medium-term lead exposure in wild Tasmanian devils (Sarcophilus harrisii). Frozen liver samples (n = 41), opportunistically collected in 2017–2022, were analysed using inductively coupled plasma mass spectrometry (ICP-MS) to determine liver lead concentrations. These results were then used to calculate the proportion of animals with elevated lead levels (>5 mg/kg dry weight) and examine the role of explanatory variables that may have influenced the results. The majority of samples analysed were from the south-east corner of Tasmania, within 50 km of Hobart. No Tasmanian devil samples were found to have elevated lead levels. The median liver lead concentration was 0.17 mg/kg (range 0.05–1.32 mg/kg). Female devils were found to have significantly higher liver lead concentrations than males (P = 0.013), which was likely related to lactation, but other variables (age, location, body mass) were not significant. These results suggest that wild Tasmanian devil populations currently show minimal medium-term evidence of exposure to lead pollution, although samples were concentrated in peri-urban areas. The results provide a baseline level which can be used to assess the impact of any future changes in lead use in Tasmania. Furthermore, these data can be used as a comparison for lead exposure studies in other mammalian scavengers, including other carnivorous marsupial species.     

Repurposing Ionophores as novel antimicrobial agents for the treatment of bovine mastitis caused by Gram‐positive pathogens

Increasing reports of multidrug‐resistant bacterial infections in animals has created a need for novel antimicrobial agents that do not promote cross‐resistance to critically important antimicrobial classes used in human medicine. In response to the recent emergence of antimicrobial resistance in several bovine mastitis pathogens, in vitro antimicrobial susceptibility was determined for four polyether ionophores (lasalocid, monensin, narasin and salinomycin) against Staphylococcus spp. and Streptococcus spp. isolated from clinical cases. In addition, erythrocyte haemolysis and WST ‐1 cell proliferation assays were used to assess in vitro mammalian cell cytotoxicity and biofilm susceptibility testing was performed using the minimum biofilm eradication concentration (MBEC ?) biofilm assay. Lasalocid, monensin, narasin and salinomycin exhibited bacteriostatic antimicrobial activity against all pathogens tested, including methicillin‐resistant staphylococci, with MIC ₉₀ values <16 μg/ml. Narasin and monensin displayed the least toxicity against mammalian cell lines and all compounds significantly reduced viable cell numbers in a Staphylococcus aureus biofilm. Based on in vitro characterization, all four ionophores offer potentially novel treatments against bovine mastitis but in vivo studies will be essential to determine whether acceptable safety and efficacy is present following intramammary administration.     

Recent advances in allelopathy for weed control: from knowledge to applications

Allelopathy is the biological phenomenon of chemical interactions between living organisms in the ecosystem, and must be taken into account in addressing pest and weed problems in future sustainable agriculture. Allelopathy is a multidisciplinary science, but in some cases, aspects of its chemistry are overlooked, despite the need for a deep knowledge of the chemical structural characteristics of allelochemicals to facilitate the design of new herbicides. This review is focused on the most important advances in allelopathy, paying particular attention to the design and development of phenolic compounds, terpenoids and alkaloids as herbicides. The isolation of allelochemicals is mainly addressed, but other aspects such as the analysis and activities of derivatives or analogs are also covered. Furthermore, the use of allelopathy in the fight against parasitic plants is included. The past 12 years have been a prolific period for publications on allelopathy. This critical review discusses future research areas in this field and the state of the art is analyzed from the chemist's perspective. © 2019 Society of Chemical Industry     

Effects of oxytocin on placental retention following dystocia

A double blind randomised clinical trial was performed to assess the effects of oxytocin on the duration of placental retention following dystocia. If the placenta remained attached to the uterus immediately following assisted delivery of a calf, and was not expelled in the period taken to complete the protocol, an intramuscular injection of either 3 ml (60 USP units) of oxytocin or 3 ml of 0.9 per cent physiological saline was given to the cow. Each farmer was asked to observe the cow to determine the time of placental expulsion. In 55 cases available for analysis there was no significant difference between the treatment and control groups for percentage of placental retention at days 1, 2 or 3 post partum.     

Effect of feeding on plasma antibiotic concentrations in Greyhounds given ampicillin and amoxycillin by mouth

In a cross-over study, six Greyhounds were dosed by mouth with ampicillin and amoxycillin at 20 mg/kg, using three different feeding regimens (no food, canned food prior to dosing, and dry food ad lib ) with each drug. Antibiotic levels in plasma were determined by microbiological assay at intervals after dosing.
Plasma ampicillin concentrations tended to be lower in fed than in starved Greyhounds, but amoxycillin levels were relatively unaffected by feeding. In starved Greyhounds, ampicillin gave higher early levels than amoxycillin.