Streptococcus iniae: an aquatic pathogen of global veterinary significance and a challenging candidate for reliable vaccination

Streptococcus iniae has become one the most serious aquatic pathogens in the last decade causing high losses in farmed marine and freshwater finfish in warmer regions. Although first identified in 1976 from a captive Amazon freshwater dolphin, from which it derives its name, disease outbreaks had most likely been occurring for several decades in marine aquaculture in Japan. S. iniae is globally distributed throughout warm water finfish aquaculture. In common with other encapsulated beta-haemolytic streptococci and in direct contradiction to the phenomenal success story of bacterial vaccines in finfish aquaculture, control of S. iniae by vaccination has met with limited success. Thus, antibiotic usage is the current practice for reducing mortality and consequent economic loss. Vaccine failure appears to result in part from serotypic variation and, whilst 2 serotypes have been named, variation would appear to be more complex. S. iniae also has zoonotic potential, with human infections identified in the USA, Canada, and throughout Asia. In humans, infection is clearly opportunistic with all cases to date associated with direct infection of puncture wounds during preparation of contaminated fish, and generally in elderly or immunocompromised individuals. Significant progress has been made in terms of research into pathogenic mechanisms of S. iniae, with recent research elucidating the role of capsule in virulence for fish through antiopsonic activity. In light of this recent coverage in the literature, the present review centres on areas of direct veterinary interest including identification, epidemiology, therapy and prevention in farmed finfish. Clearly as the prevalence of S. iniae and associated economic losses continue to increase, further work towards developing a reliable vaccine is essential. This would appear to require a much better understanding of cell-surface variability amongst S. iniae isolates.     

Acute oral toxicity of zinc phosphide: an assessment for wild house mice (Mus musculus)

Irregular plagues of house mice, Mus musculus, incur major economic impacts on agricultural production in Australia. The efficacy of zinc phosphide (ZnP), the only registered broadacre control agent for mice, is reported as increasingly variable. Have mice become less sensitive over time or are they taking a sub-lethal dose and developing aversion? In this laboratory study, the sensitivity of mice (wild caught; outbred laboratory strain) was assessed using oral gavage of a range of ZnP concentrations. The estimated LD₅₀ values (72–79 mg ZnP/kg body weight) were similar for each mouse group but are significantly higher than previously reported. The willingness of mice to consume ZnP-coated grains was determined. ZnP-coated grains (50 g ZnP/kg grain) presented in the absence of alternative food were consumed and 94% of wild mice died. Mice provided with alternative food and ZnP-coated wheat grains (either 25 or 50 g ZnP/kg grain) consumed toxic and non-toxic grains, and mortality was lower (33–55%). If a sublethal amount of ZnP-coated grain was consumed, aversion occurred, mostly when alternative food was present. The sensitivity of wild house mice to ZnP in Australia is significantly lower than previously assumed. Under laboratory conditions, ZnP-coated grains coated with a new higher dose (50 g ZnP/kg grain) were readily consumed. Consumption of toxic grain occurred when alternative food was available but was decreased. Our unambiguous findings for house mice indicate a re-assessment of the ZnP loading for baits used for control of many rodents around the world may be warranted.     

Extrapituitary and Pituitary Pathological Findings in Horses with Pituitary Pars Intermedia Dysfunction: A Retrospective Study

The objective of this study was to describe the histopathologic changes observed in extrapituitary organs as well as the pituitary glands of horses with pituitary pars intermedia dysfunction (PPID). Adrenal gland, thyroid gland, liver, lung, kidney, heart, and pituitary gland from 32 horses with clinical and histologic evidence of PPID and 20 control horses were reviewed histologically. Ten of the control horses were aged animals (≥15 years), allowing those changes attributed to age to be identified. In addition to previously reported changes in adrenal gland and liver, an association was established between PPID and several extrapituitary histopathologic changes, namely bronchiolitis, proliferative glomerulopathy, and myocardial lipofuscinosis and fibrosis. The potential biologic significance of these changes is discussed and, although the retrospective design of the current study precludes establishment of causal relationships between the observed extrapituitary changes and PPID, these findings suggest that further investigations are warranted.     

Short-term response of salal (Gaultheria shallon Pursh) to commercial harvesting for floral greenery

Salal (Gaultheria shallon Pursh), which is widely used for floral greenery, is an important non-timber forest product (NTFP) from the coastal forests of the Pacific Northwest of North America. However, there are no known studies on the impacts of commercial salal harvesting on subsequent growth. A study was therefore initiated to quantify the growth of salal 1 year after commercial harvesting, and to compare this with growth of unharvested salal. The amount of biomass removed from shrubs through commercial harvesting (131 g m⁻²) was the same as the amount of annual growth in adjacent undisturbed plots (135 g m⁻²). One year later, the amount of regrowth in previously harvested plots (144 g m⁻²) was greater than the amount of new growth in adjacent undisturbed plots (111 g m⁻²). As there was little difference in the weight per current stem, the increased biomass after commercial harvesting was attributed to the observed increase in stem number (60 stems m⁻²) as compared to undisturbed salal (50 stems m⁻²). Our study does not incorporate either repeated annual harvesting or variable harvesting intensities, both of which have been anecdotally reported to affect levels of re-growth and therefore sustainability.     

Exploring the efficacy of vaccine techniques in juvenile sablefish,Anoplopoma fimbria

Wild sablefish, Anoplopoma fimbria, are a valuable commercial species whose populations are declining. Fortunately, sablefish are excellent species for commercial aquaculture. Sablefish raised under high‐density conditions in the marine environment require the use of efficacious vaccines to control disease. Sablefish impacted by disease in net pens may have poor flesh quality and high mortality during grow‐out. As a result, disease can cause financial hardship for sablefish aquaculture operators. The efficacy of a multivalent vaccine preparation for sablefish, administered either by intraperitoneal (i.p.) injection or by immersion, against atypical and typical Aeromonas salmonicida, the causative agents of atypical and typical furunculosis, respectively, was examined. A. salmonicida can affect sablefish at any age and size. Consequently, an efficacious vaccine that can be appropriately and optimally administered to all life stages is desirable. Sablefish vaccinated by immersion at ~1.5 or ~4.5 g with a whole‐cell multivalent vaccine were not protected against either typical or atypical A. salmonicida. Factors that may have contributed to the ineffectiveness of the immersion vaccine are discussed. By contrast, the relative per cent survival (RPS) or potency of the whole‐cell multivalent vaccine injected i.p. in juvenile sablefish at ~50 g against typical and atypical A. salmonicida was 94.3% and 81.7% respectively. The high RPS values indicated that the vaccine successfully initiated an immune response in sablefish upon a second encounter with the pathogen.     

The fate of chlorpyrifos-methyl in stored wheat: A comparison of a laboratory-scale experiment with a pilot-scale treatment

An experiment was carried out in which a pilot-scale treatment of a bulk of grain with chlorpyrifos-methyl was compared with a laboratory treatment of 1 kilogram of grain with ¹⁴C-radio-labelled chlorpyrifos-methyl. The conditions under which the grain was maintained in the laboratory resembled those of the pilot-scale treatment as closely as possible, with sampling and analysis being carried out at the same time and in a similar manner in both. The results from the two experiments were in general agreement with approximately 60% of the chlorpyrifos-methyl remaining intact at the end. A satisfactory level of insect control was achieved in the pilot-scale treatment although it was not possible to assess efficacy in the radiochemical experiment. The use of the radio-label enabled more information about the fate of the degraded insecticide to be obtained from the laboratory experiment. The majority of this radioactivity comprised a fraction which remained within the grain tissue after solvent extraction. The level of activity in the grain tissues gradually increased with time but its nature is as yet unknown. The good agreement obtained between the residue profile and the breakdown patterns in both experiments would suggest that such a laboratory-scale experiment can be a satisfactory model for the situation obtaining in a larger-scale treatment.     

Effect of diet on the feces quality in javan langur (Trachypithecus auratus auratus).

A high intake of easily fermentable carbohydrates and a low intake of fiber material are generally regarded as major factors affecting the health of captive langurs. The effect on fecal consistency of excluding fruits and vegetables from the diet was evaluated in Javan langurs (Trachypithecus auratus auratus). Cross-over trials were carried out at Rotterdam Zoo and at the Apenheul Zoo, The Netherlands. During the first and third dietary period, the langurs were fed their usual diet, which contained fruits, vegetables, langur pellets, and browse. During the second period, the vegetables and fruits were excluded from the diet and the diet essentially consisted of pellets and browse. Feces consistency was scored using a fecal score chart developed for langurs. During the second feeding period the feces consistency improved significantly in animals at both zoos. Across all trials, a firmer feces consistency was correlated with an increase in dietary cell wall (measured as neutral detergent fiber) and a decrease in dietary water. It is suggested that the combined decrease in the intake of soluble sugars, the increase of fiber intake, and a lower amount of dietary water in the diet resulted in more solid stools. The results indicate that a dietary neutral detergent fiber content of approximately 46% in dry matter will result in a feces consistency indicative of undisturbed gut function.