Echinococcus granulosus in northern Queensland. 1. Prevalence in cattle.

OBJECTIVE: To determine the prevalence and geographical distribution of hydatidosis and investigate factors that might be expected to influence the prevalence of hydatids in cattle in Queensland north of the Tropic of Capricorn. To determine the effect of natural levels of infection on carcase weight and subsequent economic loss. PROCEDURE: An abattoir survey conducted in 1981 provided information on the distribution, prevalence and viability of hydatid cysts in cattle from all shires north of the Tropic of Capricorn in Queensland. Livers, lungs and spleens from 10,382 cattle were palpated at abattoirs in Cairns, Townsville and Rockhampton to detect hydatid cysts. Prevalence of infection in cattle in each shire was estimated from results of the abattoir study together with reports of infection in a further 22,185 cattle obtained from abattoir records. Linear modelling was used to define the effect of geographical origin, age, breed and sex on prevalence of infection. Differences in the weights of carcases between infected and non-infected cattle of the same age, sex, breed and property of origin were examined. The economic loss to the beef industry in the region surveyed was estimated. RESULTS: Cattle infected with hydatids originated almost entirely from regions to the east of the Great Dividing Range. The mean prevalence inside this zone was 28% compared with 3% in other areas. Viable protoscoleces were found in 0.7% of cysts. Geographical origin and age of the cattle were the most significant factors influencing prevalence. Infection with hydatids had no effect on carcase weight. Economic loss was limited to that associated with condemnations of organs at meat inspection, estimated to be 0.5 million dollars per annum in 1981 and 6 million dollars in 2004. The distribution of hydatids in Queensland north of the Tropic of Capricorn corresponded most closely with the distribution of small wallabies such as Macropus dorsalis (black-striped wallaby), M parryi (whiptail wallaby) and M rufogriseus (red-necked wallaby). CONCLUSIONS: It was concluded that cattle are not an important part of maintaining the life-cycle of E granulosus in Queensland north of the Tropic of Capricorn. Within the endemic zone, which is almost all to the east of the Great Dividing Range, the local pattern of bovine echinococcosis is most likely to be determined by the presence or absence of small species of wallaby such as M dorsalis, M parryi and M rufogriseus.

Echinococcus granulosus in northern Queensland. 2. Ecological determinants of infection in beef cattle.

OBJECTIVE: To provide information on possible ecological determinants of infection with Echinococcus granulosus in a beef pastoral area of northern Queensland. PROCEDURE: An ecological study was carried out on the prevalence and viability of infection with Echinococcus granulosus in definitive and potential intermediate hosts, and their predator prey relationships. Seven adjacent extensive beef properties 100 km south of Townsville, that included areas of savannah, open woodland and dense closed scrub, were selected for the study. Infection with E granulosus in dingoes was determined at post mortem, and in domestic dogs by examining duodenal mucus after purging with arecoline hydrobromide. Cattle, wild pigs and macropods were examined at post mortem for viable hydatid cysts. The diet of dingoes was investigated by identifying the hair of prey species found in their stomach and colon, and that of domestic dogs by questioning their owners. RESULTS: Prevalence of hydatidosis in adult cattle ranged from 41% in animals from properties with large areas of dense closed scrub, to 3% on properties with little or no scrub. Hydatid cysts were found in 21.8% of black-striped wallabies (Macropus dorsalis), 9.4% of feral pigs, 1.5% of wallaroos (Macropus robustus), and 1.4% of eastern grey kangaroos (Macropus giganteus). No rufous rat kangaroos (Aepyprymnus rufescens) or swamp wallabies (Wallabia bicolor) were infected. Most cysts in macropods were viable, whereas in pigs about half were viable and in cattle only 0.7% contained viable protoscoleces. Infection with E granulosus was detected in 76% of dingoes, whereas no infection was detected in domestic dogs in the study area. CONCLUSIONS: It was concluded that the sylvatic cycle of E granulosus in the study area was maintained mainly through predation of black-striped wallabies by dingoes, and that the verges of dense scrub were the main nidus of infection.

Role for erbin in bacterial activation of Nod2.

Intracellular peptidoglycan (PG) recognition in human cells is mediated by the NACHT-LRR proteins Nod1 and Nod2. Elicitation of these proteins by PG motifs released from invasive bacteria triggers signaling events, resulting in the activation of the NF-kappaB pathway. In order to decipher the molecular components involved in Nod2 signal transduction, we set out to identify new interaction partners of Nod2 by using a yeast two-hybrid screen. Besides the known interaction partner RIP2, the screen identified the leucine-rich repeat (LRR)- and PDZ domain-containing family member Erbin as a binding partner of Nod2. Erbin showed a specific interaction with Nod2 in coimmunoprecipitation experiments with human HEK 293T cells. Immunofluorescence microscopy with a newly generated anti-Nod2 monoclonal antibody showed that Erbin and Nod2 partially colocalize in human cells. Subsequent analysis of the Erbin/Nod2 interaction revealed that the LRR of Erbin and the caspase activating and recruiting domains of Nod2 were necessary for this interaction. No significant interaction was observed with a Walker B box mutant of Nod2 or a Crohn's disease-associated frameshift mutant of Nod2, indicating that complex formation is dependent on the activity of the molecule. In addition, a change in the dynamics of the Erbin/Nod2 complex was observed during Shigella flexneri infection. Furthermore, ectopic expression of increasing amounts of Erbin or short hairpin RNA-mediated knockdown of Erbin showed a negative influence of Erbin on Nod2/muramyl-dipeptide-mediated NF-kappaB activation. These results implicate Erbin as a potential negative regulator of Nod2 and show that bacterial infection has an impact on Nod2/Erbin complex formation within cells.

Cloning of a Heliothis virescens 110 kDa aminopeptidase N and expression in Drosophila S2 cells.

We previously identified a novel Heliothis virescens 110 kDa aminopeptidase N (APN) that binds Bacillus thuringiensis (Bt) Cry1Ac and Cry1Fa delta-endotoxins, and cloned an internal region of the 110 kDa APN gene (Banks et al., 2001). Here we describe the RACE-PCR cloning and sequence of a cDNA encoding 110 kDa APN. The 110 kDa APN gene was transiently co-expressed with green fluorescent protein (GFP) in Drosophila S2 cells using the pIZT expression vector. Enrichment of total membranes purified from S2 cells transfected with the 110 kDa APN gene had 3.3 fold increased APN enzymatic activity relative to enriched total membranes purified from S2 cells transfected with vector alone. Whereas the majority of S2 cells transfected with the 110 kDa APN gene bound rhodamine-labeled Cry1Ac toxin, no S2 cells transfected with vector alone bound rhodamine-labeled Cry1Ac toxin. This indicates that toxin binding to whole cells is APN mediated. However, flow cytometry and microscopy indicated that 110 kDa APN transfected S2 cells exposed to Cry1Ac or Cry1Fa toxin did not experience an increase in membrane permeability, indicating that APN transfected cells were resistant to toxin. This suggests while the H. virescens 110 kDa APN functions as a Bt toxin binding protein, it does not mediate cytotoxicity when expressed in S2 cells.

Instrumentation to evaluate neural signal recording properties of micromachined microelectrodes inserted in invertebrate nerve.

The design and characterization of instrumentation for application in evaluating the neural signal recording properties of probe-type microelectrodes, micromachined from silicon, are reported. Key aspects include the close matching of gain and frequency response between channels (better than 1%), flexibility in signal conditioning options, the ability to operate with a wide range of (microelectrode) recording site dimensions (4 microm x 4 micrm to 50 microm x 50 microm), and hence impedances, and the facility to monitor and store instrumentation settings on computer along with the recorded signals. Noise levels ranged from 3.7 microV rms for a 50 microm site, to 11.7 microV rms for a microm site, measured in saline. Close matching between channels was required to enable comparisons between different sites and different probes to be made with confidence; however, the instrumentation could be readily applied to less demanding applications.

Bacillus thuringiensis Cry1Ac and Cry1Fa delta-endotoxin binding to a novel 110 kDa aminopeptidase in Heliothis virescens is not N-acetylgalactosamine mediated.

We determined that Bacillus thuringiensis Cry1Ac and Cry1Fa delta-endotoxins recognize the same 110, 120 and 170 kDa aminopeptidase N (APN) molecules in brush border membrane vesicles (BBMV) from Heliothis virescens. The 110 kDa protein, not previously identified as an APN, contained a variant APN consensus sequence identical to that found in Helicoverpa punctigera APN 2. PCR amplification of H. virescens cDNA based on this sequence and a conserved APN motif yielded a 0.9 kb product that has 89% sequence homology with H. punctigera APN 2. Western blots revealed that the 110 kDa molecule was not recognized by soybean agglutinin, indicating the absence of GalNAc. A 125I labeled-Cry1Ac domain III mutant (509QNR(511)-AAA) that has an altered GalNAc binding pocket (Lee et al., Appl. Environ. Microbiol. 65 (1999) 4513) showed abolished binding to the 120 APN, reduced binding to the 170 kDa APN, and enhanced binding to the 110 kDa APN. Periodate treated H. virescens BBMV blots were also probed with 125I labeled-Cry1Ac and 509QNR(511)-AAA toxins. Both toxins still recognized the 110 kDa APN and a >210 kDa molecule which may be a cadherin-like protein. Additionally, 125I-(509)QNR(511)-AAA recognized periodate treated 170 kDa APN. Results indicate that the 110 kDa APN is distinct from other Cry1 toxin binding APNs and may be the first described Cry1Ac-binding APN that does not contain GalNAc.

Silicon-based microelectrodes for neurophysiology, micromachined from silicon-on-insulator wafers.

A process is described for the fabrication of silicon-based microelectrodes for neurophysiology using bonded and etched-back silicon-on-insulator (BESOI) wafers. The probe shapes are defined without high levels of boron doping in the silicon; this is considered as a step towards producing probes with active electronics integrated directly beneath the electrodes. Gold electrodes, of 4 microns by 4 microns to 50 microns by 50 microns are fabricated on shanks (cantilever beams) 6 microns thick and which taper to an area approximately 100 microns wide and 200 microns long, which are inserted into the tissue under investigation. The passive probes fabricated have been successfully employed to make acute recordings from locust peripheral nerve.

Japanese encephalitis.

Japanese encephalitis (JE) virus is a mosquito-borne flavivirus that can cause encephalitis and death in horses and humans. It is an emerging disease of international concern because it has been spreading into previously nonendemic areas. Major epidemics may occur where the virus moves into new areas, but many infections are subclinical. This article presents information on the virus, its epidemiology, and what little information has been published on the disease in horses. The methods available for the diagnosis and control of JE are described and issues raised, particularly for those countries faced with the threat of imminent incursions as the virus extends its range.

The value of circulating eosinophil count as a selection criteria for resistance of sheep to trichostrongyle parasites.

In merino sheep bred for either increased or decreased resistance to Haemonchus contortus, faecal worm egg counts (FEC) were lower in the resistant line (6,831 vs 17,645 epg, P < 0.01), and circulating eosinophils (EOS) were higher, but not significantly so (3.40 x 10(4) ml(-1) vs 1.40 x 10(4) ml(-1), P = 0.1 1). Another flock was artificially infected with Trichostrongylus colubriformis and significant genetic variation was found in both FEC (heritability 0.40 +/- 0.11) and EOS (0.19 +/- 0.08). In a third flock comprising tropical sheep breeds, a natural challenge with T. colubriformis resulted in significant sire effects on FEC (heritability 0.20 +/- 0.10) but not EOS (heritability inestimable). We conclude that EOS offers no advantage over FEC as it selection criterion for resistance.

Rotational grazing for control of gastrointestinal nematodes of goats in a wet tropical environment.

A preliminary experiment involving contamination of pasture plots with eggs of Haemonchus contortus, Trichostronglyus colubriformis and Oesophagostomum columbianum every month for a year established that in the tropical environment of the Pacific island of Tongatapu, hatching and development of all species was rapid and continuous, with a short survival on pasture (3-7 weeks) of the resulting infective larvae. These results indicated that a rotational grazing system consisting of ten paddocks grazed in sequence for 3.5 days at a time may permit a reduction in the frequency of anthelmintic treatment of goats. In comparison with an adjacent set-stocked flock which required treatment on three occasions during the year when mean flock egg counts exceeded 2000 eggs per gram (EPG), rotationally grazed goats generally maintained mean egg counts of less than 1000 EPG. Anthelmintic treatment was only given to rotationally grazed goats individually as they kidded, and there were indications that even this precaution was unnecessary. Because of the expense of frequent anthelmintic treatment and the resulting selection of strains of anthelmintic-resistant nematodes, rotational grazing of small ruminants through fencing, tethering or herding deserves further investigation as a nematode control option in wet tropical environments.

The application of risk assessment in animal quarantine in Australia.

This paper describes the ways in which the Australian Quarantine and Inspection Service (AQIS) uses risk assessment and risk management. Taking into account the need to meet both national and international obligations, AQIS has adopted a more systematic and transparent approach to import risk assessment by employing a procedure designed to examine each point along the importation chain at which an animal or animal product might become infected. The authors discuss the four principal factors influencing the risk involved and the three phases used by AQIS in assessing risk. Objective data are rarely available in the animal health field and most analyses rely, at least in part, on subjective estimates. The authors outline a way of overcoming this through the use of simulation, whereby probability distributions are used for many steps.

Development and survival of infective larvae of Haemonchus contortus and Trichostrongylus colubriformis on pasture in a tropical environment.

A trial to determine the seasonal pattern of egg hatching and larval survival on pasture was carried out in representative wet and dry zones of Fiji. Fourteen plots were established on parasite-free pasture at each of two sites. One plot at each site was contaminated every month with faeces from naturally infected goats containing a known proportion of Haemonchus contortus and Trichostrongylus colubriformis eggs. Pasture was sampled at regular intervals after contamination and infective larvae identified and counted. Larvae of both species developed throughout the year in the wet zone but development was more sporadic in the dry zone. Larval counts generally declined to below detectable levels within 9 weeks of contamination between September and March but longevity increased during the cooler weather from April to August. The comparatively short larval survival times noted in this experiment may present opportunities for manipulation of parasite population dynamics in the wet tropics.

Resistance to Meloidogyne hapla in Peanut.

Two hundred thirty-five cultivated varieties, breeding lines and plant introductions of Arachis hypogaea and 12 accessions of wild Arachis spp. were tested for resistance to Meloidogyne hapla. Eight of the cultivated peanut lines were only moderately susceptible and four of the wild peanuts exhibited resistance. No resistance-breaking M. hapla populations were found among 10 geographical isolates tested.