Selection and characterisation of two attenuated vaccine lines of Eimeria tenella in Australia

Objective To attenuate two strains of Eimeria tenella by selecting for precocious development and evaluate the strains in characterisation trials and by field evaluation, to choose one precocious line for incorporation into an Australian live coccidiosis vaccine for poultry. Design Two strains from non-commercial flocks were passaged through chickens while selecting for precocious development. Each strain was characterised for drug sensitivity, pathogenicity, protection against homologous and heterologous challenge, and oocyst output in replicated experiments in which the experimental unit was a cage of three birds. Oocyst output and/or body weight gain data collected over a 10 to 12 day period following final inoculation were measured. Feed conversion ratios were also calculated where possible. Results Fifteen passages resulted in prepatent periods reduced by 24 h for the Redlands strain (from 144 h to 120 h)and 23 h for the Darryl strain (from 139 h to 116 h). Characterisation trials demonstrated that each precocious line was significantly less pathogenic than its parent strain and each effectively induced immunity that protected chickens against challenge with both the parent strain and other virulent field strains. Both lines had oocyst outputs that, although significantly reduced relative to the parent strains, remained sufficiently high for commercial vaccine production, and both showed susceptibility to coccidiostats. Conclusion Two attenuated lines have been produced that exhibit the appropriate characteristics for use in an Australian live coccidiosis vaccine.

Comparative growth and pathogenicity of geographical isolates of Sclerotinia sclerotiorum on lentil genotypes

Isolates of Sclerotinia sclerotiorum were collected from infected lentil plants from 2 agro-ecological zones of Syria and used to study their comparative growth on culture media and pathogenicity on different lentil genotypes. The growth studies were carried out on Potato Dextrose Agar (PDA) growth media under laboratory conditions. Mycelial radial growth and sclerotial production were the parameters used to compare the isolates. Pathogenicity studies were carried out with selected isolates on 10 lentil genotypes, infected as detached shoots and as whole potted-plants in the plastic house. The isolates showed considerable variation in cultural characteristics through mycelial growth, mycelial pigmentation and sclerotial production in the media plates. There were significant differences in the growth and sclerotial production of most of the isolates, but no apparent correlation between mycelial growth and sclerotial production among the isolates. Genotype by isolate interactions was significant for the isolates tested for pathogenicity. These interactions, however, appeared to be caused by differences in virulence of the isolates and did not suggest the occurrence of distinct pathogenic races of the pathogen isolates.

Using immunology and resistant sheep to beat the fly

New methods for controlling blowfly strike will be needed when mulesing is phased out and the availability or efficacy of insecticides for control of fly strike decreases. The Australian Sheep Industry CRC has pursued two approaches for the development of new methods to help control blowfly strike. In the first, genetic resistance of sheep to survival and growth of blowfly larvae was examined. Resistance to growth of larvae was heritable (0.29 ± 0.22). The trait was not associated with resistance to internal parasites, nor was it influenced by wool characteristics such as fibre diameter or coefficient of variation of fibre diameter. This new trait differs from resistance to fly strike associated with resistance to fleece rot. Because measurement of the trait is labour intensive, gene markers or correlated measures are needed before it will be suitable for industry adoption. The second approach examined the impact of larval products on the immmune system of the sheep. Larvae suppress the sheep immune system and thereby limit the ability of the sheep to reject the larvae. The immunosuppresive agent is being purified and strategies to abolish its activity are being explored. Abolition of immunosuppression would create opportunities for the development of new vaccines againts blowfly strike.

Phylogenetic considerations for predicting the host range of Ustilago sporoboli-indici, a potential biological control agent for Sporobolus species in Australia

The ribosomal DNA internal transcribed spacer region was amplified and sequenced from a selection of specimens of the Sporobolus smut Ustilago sporoboli-indici. Phylogenetic comparison with other Ustilago and Sporisorium species revealed strong support for an evolutionary radiation of Ustilago species infecting the Chloridoideae and Pooideae, of which U. sporoboli-indici forms a major lineage. Comparisons are made with other groups of plant pathogenic fungi, and it is concluded that phylogenetic analyses of potential biocontrol agents are useful for identifying pathogens that are derived from evolutionary lineages that parasitize a wide range of unrelated plants. Such pathogens are less desirable as biocontrol agents as they may have a greater likelihood of infecting plants outside their normal host ranges.

Phytogeny of the Quambalariaceae fam. nov., including important Eucalyptus pathogens in South Africa and Australia

The genus Quambalaria consists of plant-pathogenic fungi causing disease on leaves and shoots of species of Eucalyptus and its close relative, Corymbia. The phylogenetic relationship of Quambalaria spp., previously classified in genera such as Sporothrix and Ramularia, has never been addressed. It has, however, been suggested that they belong to the basidiomycete orders Exobasidiales or Ustilaginales. The aim of this study was thus to consider the ordinal relationships of Q. eucalypti and Q. pitereka using ribosomal LSU sequences. Sequence data from the ITS nrDNA were used to determine the phylogenetic relationship of the two Quambalaria species together with Fugomyces (= Cerinosterus) cyanescens. In addition to sequence data, the ultrastructure of the septal pores of the species in question was compared. From the LSU sequence data it was concluded that Quambalaria spp. and F. cyanescens form a monophyletic clade in the Microstromatales, an order of the Ustilaginomycetes. Sequences from the ITS region confirmed that Q. pitereka and Q. eucalypti are distinct species. The ex-type isolate of F. cyanescens, together with another isolate from Eucalyptus in Australia, constitute a third species of Quambalaria, Q. cyanescens (de Hoog & G.A. de Vries) Z.W. de Beer, Begerow & R. Bauer comb. nov. Transmission electron-microscopic studies of the septal pores confirm that all three Quambalaria spp. have dolipores with swollen lips, which differ from other members of the Microstromatales (i.e. the Microstromataceae and Volvocisporiaceae) that have simple pores with more or less rounded pore lips. Based on their unique ultrastructural features and the monophyly of the three Quambalaria spp. in the Microstromatales, a new family, Quambalariaceae Z.W. de Beer, Begerow & R. Bauer fam. nov., is described.

Immunointervention for patients with HIV and tuberculosis

Therapeutic options aimed at confronting the HIV pandemic face many obstacles. Current opinion on HIV-induced pathogenic immune activation and strategies aimed at eliminating HIV, including a potential role for non-neutralising antibodies as part of a therapeutic vaccine option, was elegantly reviewed by Martin Cadogan and Angus Dalgleish. 1 It is important to note that, for eliciting such antibody responses in patients, functionally fit antigen presenting cells and effector T and B cells are cruc.

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.

Ceratocystis atrox sp. nov. associated with Phoracantha acanthocera infestations on Eucalyptus grandis in Australia

Ceratocystis spp. include important pathogens of trees as well as apparently saprophytic species. Four species have been recorded on Eucalyptus grandis in Australia, of which only one, C. pirilliformis Barnes and M.J. Wingf., is known to be pathogenic. A recent survey of pests and diseases of Eucalyptus trees in northern Queensland revealed a species of Ceratocystis associated with the tunnels made by the aggressive wood-boring insect Phoracantha acanthocera (Macleay) (Cerambicydae: Coleoptera). The aim of the present study was to identify the fungus based on morphological characteristics and comparisons of DNA sequence data for three gene regions. The fungus peripherally resembles C. fimbriata Ell. and Halst. but differs from this species most obviously by having much darker mycelium, longer ascomatal necks, segmented hyphae and an absence of aleuroconidia. Comparisons of combined sequence data confirmed that the Ceratocystis sp. from P. acanthocera represents an undescribed taxon, which is provided with the name Ceratocystis atrox sp. nov. C. atrox appears to have a close relationship with P. acanthocera, although its role in the biology of the insect is unknown and its pathogenicity has not been considered.

Insecticide resistance and implications for future aphid management in Australian grains and pastures: A review

Aphids can cause substantial damage to cereals, oilseeds and legumes through direct feeding and through the transmission of plant pathogenic viruses. Aphid-resistant varieties are only available for a limited number of crops. In Australia, growers often use prophylactic sprays to control aphids, but this strategy can lead to non-target effects and the development of insecticide resistance. Insecticide resistance is a problem in one aphid pest of Australian grains in Australia, the green peach aphid (Myzus persicae). Molecular analyses of field-collected samples demonstrate that amplified E4 esterase resistance to organophosphate insecticides is widespread in Australian grains across Australia. Knockdown resistance to pyrethroids is less abundant, but has an increased frequency in areas with known frequent use of these insecticides. Modified acetylcholinesterase resistance to dimethyl carbamates, such as pirimicarb, has not been found in Australia, nor has resistance to imidacloprid. Australian grain growers should consider control options that are less likely to promote insecticide resistance, and have reduced impacts on natural enemies. Research is ongoing in Australia and overseas to provide new strategies for aphid management in the future.

Encroachment of Echinococcus granulosus into urban areas in eastern Queensland, Australia

Objective: To investigate the prevalence of Echinococcus granulosus in wild dogs (dingos and dingo-domestic dog hybrids) living in and around human habitation on Fraser Island and in townships of the Maroochy Shire, on Queensland's Sunshine Coast, Australia. Design: Wild dogs were humanely killed on Fraser Island and in the Maroochy Shire because they were deemed a potential danger to the public. Their intestines were collected and the contents examined for intestinal parasites. Procedure: Intestines were removed as soon after death as possible, packed in plastic bags and kept frozen until examination. The intestinal contents were washed, sieved and examined microscopically for the presence of helminths, which were identified and counted. Results: Intestines from 108 wild dogs, 7 foxes and 18 Fraser Island dingoes were examined. Echinococcus granulosus was only present in the wild dogs from Maroochy Shire (46.3%) with worm burdens of between 30 and 104,000. Other helminths included Spirometra erinacei, Dipylidium caninum, Taenia spp., Ancylostoma caninum and Toxocara canis. Two specimens of a trematode (Haplorchinae sp.) usually found infecting fish and seabirds were recovered from a Fraser Island dingo. Conclusion: Dingoes on Fraser Island are not infected with E. granulosus and do not pose a hydatid disease public health risk to residents or visitors. However, wild dogs examined from the Maroochy Shire do present a potential hydatid disease public health risk.

Genetic alternatives to mulesing and tail docking in sheep: a review

A genetic solution to breech strike control is attractive, as it is potentially permanent, cumulative, would not involve increased use of chemicals and may ultimately reduce labour inputs. There appears to be significant opportunity to reduce the susceptibility of Merinos to breech strike by genetic means although it is unlikely that in the short term breeding alone will be able to confer the degree of protection provided by mulesing and tail docking. Breeding programmes that aim to replace surgical techniques of flystrike prevention could potentially: reduce breech wrinkle; increase the area of bare skin in the perineal area; reduce tail length and wool cover on and near the tail; increase shedding of breech wool; reduce susceptibility to internal parasites and diarrhoea; and increase immunological resistance to flystrike. The likely effectiveness of these approaches is reviewed and assessed here. Any breeding programme that seeks to replace surgical mulesing and tail docking will need to make sheep sufficiently resistant that the increased requirement for other strike management procedures remains within practically acceptable bounds and that levels of strike can be contained to ethically acceptable levels.

Evaluation of the most effective measures of infectivity of a precocious line of Eimeria acervulina in poultry

Coccidiosis is an economically important parasitic disease of chickens that, in Australia, is caused by seven species of the genus Eimeria.1 The disease has traditionally been controlled by prophylactic drugs, but vaccination with attenuated lines of the parasites2–4 is rapidly gaining acceptance world wide. Live Eimeria vaccines are produced in batches which are not frozen and have a limited shelf life. The per cent infectivity of vaccine seed stocks and the vaccines produced from them must therefore be accurately monitored using standardised dose dependant assays to ensure that shelf life, quality control and vaccine release specifications are met. Infectivity for the chicken host cannot readily be determined by microscopic observation of oocysts or sporocyst hatching.5 Dose dependent parameters such as body weight gain, feed conversion ratio, visual lesion scores, mortality, oocysts production, clinical symptoms and microscopic lesion counts could be used as measures of infectivity.6–11 These parameters show significant dose dependant effects with field strains, but lines of vaccine parasites that have been selected for precocious development with associated reduced virulence and reproductive capability may not have the same effect.3,4 The aim of this trial was to determine which parameters provide the most effective measures of infective dose in birds inoculated with a precocious vaccine strain.

First fungal pathogen to be utilized for weed biocontrol in Fiji and Papua New Guinea

Biological control of weeds has been carried out in Fiji since 1911, when the seed-fly Ophiomyia lantanae was introduced in an attempt to control Lantana camara. In 1988, the thrips Liothrips mikaniae was introduced from Trinidad into the Solomon Islands in an attempt to undertake biocontrol of Mikania micrantha (mikania) in the Pacific. A small colony of the thrips was subsequently taken from the Solomon Islands to the Kerevat Lowlands Agricultural Experimental Station in New Britain, Papua New Guinea (PNG). Now two decades later and for the first time, a pathogenic rust fungus has been imported for use against mikania, one of Fiji’s and the Pacific’s worst invasive weeds.