Osteopenia and rickets in the extremely low birth weight infant: A survey of the incidence and a radiological classification

A review was carried out of the radiographs of twenty-five infants with birth weights under 1000 G, who survived for more than twenty-eight days; eighteen of these had enough suitable films for a survey of the progressive bone changes which occur in these infants, including estimation of humeral cortical cross-sectional area. The incidence of the changes has been assessed and a typical progression of radiographic appearances has been shown, with a suggested system of staging. All infants showed some loss of bone mineral, with frank changes of rickets occurring in forty-four percent. Aetiological factors are mainly concerned with the difficulty of supplying and ensuring absorption of sufficient bone mineral (calcium and phosphate) and vitamin D. Liver immaturity may be another factor. Disease states additional to prematurity accentuate the problem. Rib fractures occurring around 80–90 days post-nataEy commonly draw attention to the bone disorder and are probably the major clinical factor of importance; there is a high incidence of associated lung disease of uncertain pathology. Attention is drawn to possible confusion with other bone disorders in the post-natal period.

The genetic diversity of ampeloviruses in Australian pineapples and their association with mealybug wilt disease

Pineapple mealybug wilt-associated virus 1 (PMWaV-1), 2 (PMWaV-2) and -3 (PMWaV-3) have been detected in Australian commercial pineapple crops, along with a previously undescribed ampelovirus, for which the name Pineapple mealybug wilt-associated virus 5 (PMWaV-5) is proposed. Partial sequences extending from open reading frame 1b through to the heat shock protein homologue were obtained for PMWaV-1, -3 and -5. Phylogenetic analyses of selected regions of these sequences indicated that PMWaV-5 is a distinct species and most closely related to PMWaV-1. The amino acid sequence variation observed in the RNA-dependent RNA polymerase region of PMWaV-1 isolates was 95.8–98.4% and of PMWaV-3 isolates was 92.2–99.5%. In surveys of mealybug wilt disease (MWD) affected crops, none of the four viruses was clearly associated with the disease at all survey sites. A statistically significant association (P < 0.001) between the presence of PMWaV-2 and symptoms was observed at one survey site (site 3), but the virus was at a low incidence at the remaining three survey sites. By contrast, although PMWaV-1 and -3 were equally distributed between symptomless and MWD-affected plants at site 3, there was a statistically significant (P < 0.001) association between each of these two viruses and MWD at sites 1 and 4. At site 2, there was a statistically significant (P < 0.001) association only between PMWaV-3 and MWD. PMWaV-1 was the most commonly found of the four viruses and conversely PMWaV-5 was only occasionally found. Australian isolates of PMWaV-1, -2 and -3 were transmitted by the mealybug species Dysmicoccus brevipes.

The vaccination-challenge trial: the gold standard test to evaluate the protective efficacy of infectious coryza vaccines

Infectious coryza is an upper respiratory tract disease of chickens with the major impact occurring in multi-age flocks. We investigated the relationship between the level of antibodies, as detected by a haemagglutination-inhibition (HI) assay, in infectious coryza-vaccinated chickens and the protection against challenge in those chickens. In one experiment, chickens given a single dose of either of two infectious coryza vaccines lacked a detectable HI response to vaccination but showed significant levels of protection 11 weeks after vaccination. In contrast, in chickens given two doses of an infectious coryza vaccine and challenged 3 weeks after the second vaccine dose, there was a strong serological response with 36/40 birds having a HI titre of 1/20 or greater. In this trial there was an apparent relationship between titre and subsequent protection, with none of the 32 chickens with a titre of 1/40 or 1/80 showing any clinical signs and only one of the same group yielding the challenge organism on culture. In contrast, three of the four vaccinated chickens with a HI titre less than 1/5 developed the typical clinical signs of coryza and yielded the challenge organism on culture. Overall, our results suggest that HI titres cannot be regarded as a definitive predictor of vaccine efficacy. We suggest that the vaccination-challenge trial is the gold standard for the evaluation of the immune response to infectious coryza vaccines.

Transgenic gene silencing strategies for virus control.

Co-suppression of transgenes and their homologous viral sequences by RNA silencing is a powerful strategy for achieving high-level virus resistance in plants. This review provides a brief overview of RNA silencing mechanisms in plants and discusses important transgene construct design features underpinning successful RNA silencing-mediated transgenic virus control. Application of those strategies to protect horticultural and field crops from virus infection and results of field tests are also provided. The effectiveness and stability of RNA-mediated transgenic resistance are assessed taking into account effects of viral, plant and environmental factors.

Quambalaria species associated with plantation and native eucalypts in Australia

This study aimed to determine which species of Quambalaria are associated with shoot blight symptoms on Corymbia spp. An additional aim was to determine the presence and impact of quambalaria shoot blight on Eucalyptus species used in plantation development in subtropical and tropical regions of eastern Australia. Surveys identified three Quambalaria spp. -Q. pitereka, Q. eucalypti and Q. cyanescens - from native and plantation eucalypts, as well as amenity plantings, including the first confirmed report of Q. eucalypti from Eucalyptus plantations in Australia. Symptom descriptions and morphological studies were coupled with phylogenetic studies using ITS rDNA sequence data. Quambalaria pitereka was the causal agent of blight symptoms on species and hybrids in the Corymbia complex. Quambalaria eucalypti was identified from Eucalyptus species and a single Corymbia hybrid. Quambalaria cyanescens was detected from native and plantation Corymbia spp.

Tospoviruses - An Australian perspective

The detection, distribution, molecular and biological properties, vector relations and control of tospoviruses present in Australia, including Tomato spotted wilt virus (TSWV), Capsicum chlorosis virus (CaCV) and Iris yellow spot virus (IYSV), are reviewed. TSWV occurs throughout Australia where it has caused serious sporadic epidemics since it was first described in the 1920s. The frequency and distribution of outbreaks has increased in the 1990s, with the arrival and dispersal of the western flower thrips (Frankliniella occidentalis) being one factor favouring this situation. The crops most frequently and severely affected are capsicum, lettuce, tomato, potato and several species of ornamentals. Minimal differences were found between the nucleocapsid (N) gene amino acid sequences of Australian isolates and these were most closely related to a clade of northern European isolates. CaCV was first detected in Australia in 1999 and is most closely related to Watermelon silver mottle virus, a serogroup IV tospovirus. The natural hosts include capsicum, tomato, peanut and Hoya spp. The virus also occurs in Thailand and Taiwan. IYSV was first found in Australia in 2003, infecting onion and leek, with the distribution in three States suggesting that the virus has been present for some time.

Antimicrobial susceptibility testing of Brachyspira intermedia and Brachyspira pilosicoli isolates from Australian chickens

Susceptibilities of predominantly Australian isolates of the pathogenic intestinal spirochaetes Brachyspira intermedia (n=25) and Brachyspira pilosicoli (n=17) from chickens were tested in agar dilution against four concentrations each of the antimicrobials tiamulin, lincomycin, tylosin, metronidazole, tetracycline and ampicillin. Based on available minimum inhibitory concentration (MIC) breakpoint values for Brachyspira hyodysenteriae or other Gram-negative enteric veterinary pathogens, isolates of both species generally were susceptible to tiamulin, lincomycin, metronidazole and tetracycline. Although not classed as resistant, four isolates of B. intermedia had an elevated MIC range for tiamulin (1 to 4 mg/l), 11 isolates of B. intermedia and five of B. pilosicoli had an elevated MIC range for lincomycin (10 to 50 mg/l), one isolate of B. pilosicoli had an elevated MIC range for tetracycline (10 to 20 mg/l), and one isolate of B. intermedia and five of B. pilosicoli had an elevated MIC range for ampicillin (10 to 50 mg/l). A clear lack of susceptibility to tylosin (MIC >4 mg/l) was seen in 11 isolates each of B. intermedia and B. pilosicoli, and to ampicillin (MIC >32 mg/l) in two isolates of B. pilosicoli. These data suggest that some resistance to common antimicrobials exists among intestinal spirochetes obtained from laying hens and supports the need of MIC data for clinical isolates before any treatment is considered.

Diversity in the sunflower: Puccinia helianthi pathosystem in Australia

Sunflower rust caused by Puccinia helianthi is the most important disease of sunflower in Australia with the potential to cause significant yield losses in susceptible hybrids. Rapid and frequent virulence changes in the rust fungus population limit the effective lifespan of commercial cultivars and impose constant pressure on breeding programs to identify and deploy new sources of resistance. This paper contains a synopsis of virulence data accumulated over 25 years, and more recent studies of genotypic diversity and sexual recombination. We have used this synopsis, generated from both published and unpublished data, to propose the origin, evolution and distribution of new pathotypes of P. helianthi. Virulence surveys revealed that diverse pathotypes of P. helianthi evolve in wild sunflower populations, most likely because sexual recombination and subsequent selection of recombinant pathotypes occurs there. Wild sunflower populations provide a continuum of genetically heterogeneous hosts on which P. helianthi can potentially complete its sexual cycle under suitable environmental conditions. Population genetics analysis of a worldwide collection of P. helianthi indicated that Australian isolates of the pathogen are more diverse than non-Australian isolates. Additionally, the presence of the same pathotype in different genotypic backgrounds supported evidence from virulence data that sexual recombination has occurred in the Australian population of P. helianthi at some time. A primary aim of the work described was to apply our knowledge of pathotype evolution to improve resistance in sunflower to sunflower rust. Molecular markers were identified for a number of previously uncharacterised sunflower rust R-genes. These markers have been used to detect resistance genes in breeding lines and wild sunflower germplasm. A number of virulence loci that do not recombine were identified in P. helianthi. The resistance gene combinations corresponding to these virulence loci are currently being introgressed with breeding lines to generate hybrids with durable resistance to sunflower rust.

An annotated checklist of smut fungi (Ustilaginomycetes) from Thailand

An annotated checklist of the smut fungi (Ustilaginomycetes) from Thailand has been compiled after an examination of the scientific literature, previously deposited herbarium specimens and specimens collected by the authors during a survey in December 2005. Fifty-two species of smut fungi are listed, including 11 species which were newly discovered during our survey. Most of these smut fungi are reported for the first time from Thailand. Several species are very rare, being known only from the type material or a limited number of collections.