Abaca bunchy top virus, a new member of the genus Babuvirus (family Nanoviridae)

Two isolates of a novel babuvirus causing "bunchy top" symptoms were characterised, one from abaca (Musa textilis) from the Philippines and one from banana (Musa sp.) from Sarawak (Malaysia). The name abacá bunchy top virus (ABTV) is proposed. Both isolates have a genome of six circular DNA components, each ca. 1.0-1.1 kb, analogous to those of isolates of Banana bunchy top virus (BBTV). However, unlike BBTV, both ABTV isolates lack an internal ORF in DNA-R, and the ORF in DNA-U3 found in some BBTV isolates is also absent. In all phylogenetic analyses of nanovirid isolates, ABTV and BBTV fall in the same clade, but on separate branches. However, ABTV and BBTV isolates shared only 79-81% amino acid sequence identity for the putative coat protein and 54-76% overall nucleotide sequence identity across all components. Stem-loop and major common regions were present in ABTV, but there was less than 60% identity with the major common region of BBTV. ABTV and BBTV were also shown to be serologically distinct, with only two out of ten BBTV-specific monoclonal antibodies reacting with ABTV. The two ABTV isolates may represent distinct strains of the species as they are less closely related to each other than are isolates of the two geographic subgroups (Asian and South Pacific) of BBTV.

Henipavirus in Pteropus vampyrus Bats, Indonesia

The emergence of Nipah virus (NiV) in Malaysia in 1999 resulted in 265 known human infections (105 fatal), widespread infection in pigs (with >1 million culled to control the outbreak), and the collapse of the Malaysian pig export market. As with the closely related Hendra virus (HeV) that emerged in Australia in 1994 and caused fatal disease in horses and humans, bats of the genus Pteropus (commonly known as flying foxes) were identified as the major reservoir of Nipah virus in Malaysia. This report describes a serologic survey of Pteropus vampyrus in neighboring Indonesia.

Drosophila melanogaster mounts a unique immune response to the rhabdovirus Sigma virus

Rhabdoviruses are important pathogens of humans, livestock, and plants that are often vectored by insects. Rhabdovirus particles have a characteristic bullet shape with a lipid envelope and surface-exposed transmembrane glycoproteins. Sigma virus (SIGMAV) is a member of the Rhabdoviridae and is a naturally occurring disease agent of Drosophila melanogaster. The infection is maintained in Drosophila populations through vertical transmission via germ cells. We report here the nature of the Drosophila innate immune response to SIGMAV infection as revealed by quantitative reverse transcription-PCR analysis of differentially expressed genes identified by microarray analysis. We have also compared and contrasted the immune response of the host with respect to two nonenveloped viruses, Drosophila C virus (DCV) and Drosophila X virus (DXV). We determined that SIGMAV infection upregulates expression of the peptidoglycan receptor protein genes PGRP-SB1 and PGRP-SD and the antimicrobial peptide (AMP) genes Diptericin-A, Attacin-A, Attacin-B, Cecropin-A1, and Drosocin. SIGMAV infection did not induce PGRP-SA and the AMP genes Drosomycin-B, Metchnikowin, and Defensin that are upregulated in DCV and/or DXV infections. Expression levels of the Toll and Imd signaling cascade genes are not significantly altered by SIGMAV infection. These results highlight shared and unique aspects of the Drosophila immune response to the three viruses and may shed light on the nature of the interaction with the host and the evolution of these associations.

Review of bats and SARS

Bats have been identified as a natural reservoir for an increasing number of emerging zoonotic viruses, including henipaviruses and variants of rabies viruses. Recently, we and another group independently identified several horse-shoe bat species (genus Rhinolophus) as the reservoir host for a large number of viruses that have a close genetic relationship with the coronavirus associated with severe acute respiratory syndrome (SARS). Our current research focused on the identification of the reservoir species for the progenitor virus of the SARS coronaviruses responsible for outbreaks during 2002-2003 and 2003-2004. In addition to SARS-like coronaviruses, many other novel bat coronaviruses, which belong to groups 1 and 2 of the 3 existing coronavirus groups, have been detected by PCR. The discovery of bat SARS-like coronaviruses and the great genetic diversity of coronaviruses in bats have shed new light on the origin and transmission of SARS coronaviruses.

Infection with Menangle virus in flying foxes (Pteropus spp.) in Australia

Objective: To examine flying foxes (Pteropus spp.) for evidence of infection with Menangle virus. Design: Clustered non-random sampling for serology, virus isolation and electron microscopy (EM). Procedure: Serum samples were collected from 306 Pteropus spp. in northern and eastern Australia and tested for antibodies against Menangle virus (MenV) using a virus neutralisation test (VNT). Virus isolation was attempted from tissues and faeces collected from 215 Pteropus spp. in New South Wales. Faecal samples from 68 individual Pteropus spp. and four pools of faeces were examined by transmission EM following routine negative staining and immunogold labelling. Results: Neutralising antibodies (VNT titres ≥ 8) against MenV were detected in 46% of black flying foxes (P. alecto), 41% of grey-headed flying foxes (P. poliocephalus), 25% of spectacled flying foxes (P. conspicillatus) and 1% of little red flying foxes (P. scapulatus) in Australia. Positive sera included samples collected from P. poliocephalus in a colony adjacent to a piggery that had experienced reproductive disease caused by MenV. Virus-like particles were observed by EM in faeces from Pteropus spp. and reactivity was detected in pooled faeces and urine by immunogold EM using sera from sows that had been exposed to MenV. Attempts to isolate the virus from the faeces and tissues from Pteropus spp. were unsuccessful. Conclusion: Serological evidence of infection with MenV was detected in Pteropus spp. in Australia. Although virus-like particles were detected in faeces, no viruses were isolated from faeces, urine or tissues of Pteropus spp.

Field isolates of Tomato spotted wilt virus overcoming resistance in capsicum in Australia

In 2002 at Virginia, South Australia, capsicum cultivars having the Tsw resistance gene against Tomato spotted wilt virus (TSWV) developed symptoms typical of TSWV infection and several glasshouse-grown crops were almost 100% infected. Samples reacted with TSWV antibodies in ELISA. Virus isolates from infected plants induced severe systemic symptoms, rather than a hypersensitive reaction, when inoculated onto capsicum cultivars and Capsicum chinense genotypes ( PI 152225 and PI 159236) that carry the Tsw resistance gene. Isolates virulent towards the Tsw gene had molecular and biological properties very similar to standard TSWV isolates, including a hypersensitive reaction in Sw-5 (TSWV-resistant) tomato genotypes. Tsw-virulent isolates were found during surveys at Virginia in 2002 and 2004 in both TSWV-resistant and susceptible cultivars of capsicum and tomato.

Identification of two distinct bovine parainfluenza virus type 3 genotypes

The partial gene sequencing of the matrix (M) protein from seven clinical isolates of bovine parainfluenza virus type 3 (BPIV-3), and the complete sequencing of a representative isolate (Q5592) was completed in this study. Nucleotide sequence analysis was initiated because of the failure of in-house BPIV-3 RT-PCR methods to yield expected products for four of the isolates. Phylogenetic reconstructions based on the nucleotide sequences for the M-protein and the entire genome, using all of the available BPIV-3 nucleotide sequences, demonstrated that there were two distinct BPIV-3 genotypes (BPIV-3a and BPIV-3b). These newly identified genotypes have implications for the development of BPIV-3 molecular detection methods and may also impact on BPIV-3 vaccine formulations.

Absolute quantitation of Marek's disease virus and Herpesvirus of turkeys in chicken lymphocyte, feather tip and dust samples using real-time PCR

The further development of Taqman quantitative real-time PCR (qPCR) assays for the absolute quantitation of Marek's disease virus serotype 1 (MDV1) and Herpesvirus of turkeys (HVT) viruses is described and the sensitivity and reproducibility of each assay reported. Using plasmid DNA copies, the lower limit of detection was determined to be 5 copies for the MDV1 assay and 75 copies for the HVT assay. Both assays were found to be highly reproducible for Ct values and calculated copy numbers with mean intra- and inter-assay coefficients of variation being less than 5% for Ct and 20% for calculated copy number. The genome copy number of MDV1 and HVT viruses was quantified in PBL and feather tips from experimentally infected chickens, and field poultry dust samples. Parallelism was demonstrated between the plasmid-based standard curves, and standard curves derived from infected spleen material containing both viral and host DNA, allowing the latter to be used for absolute quantification. These methods should prove useful for the reliable differentiation and absolute quantitation of MDV1 and HVT viruses in a wide range of samples.

Cucumber mosaic virus infection of kava (Piper methysticum) and implications for cultural control of kava dieback disease

Cucumber mosaic virus (CMV) was found by reverse transcription polymerase chain reaction (RT-PCR) to be not fully systemic in naturally infected kava (Piper methysticum) plants in Fiji. Twenty-six of 48 samples (54%) from various tissues of three recently infected plants were CMV-positive compared with 7/51 samples (14%) from three long-term infections (plants affected by dieback for more than 1 year). The virus was also found to have a limited ability to move into newly formed stems. CMV was detected in only 2/23 samples taken from re-growth stems arising from known CMV infected/dieback affected plants. Mechanical inoculation experiments conducted in Fiji indicate that the known kava intercrop plants banana (Musa spp.), pineapple (Ananas comosus), peanut (Arachis hypogaea) and the common weed Mikania micrantha are potential hosts for a dieback-causing strain of CMV It was not possible to transmit the virus mechanically to the common kava intercrop plants taro (Colocasia esculenta), Xanthosoma sp., sweet potato (Ipomoea batatas), yam (Dioscorea alata), papaya (Carica papaya) or the weed Momordica charantia. Implications of the results of this research on a possible integrated disease management strategy are discussed.

Capsicum chlorosis virus infecting Capsicum annuum in the East Kimberley region of Western Australia

Capsicum chlorosis virus (CaCV) was detected in field grown Capsicum annuum from Kununurra in northeast Western Australia. Identification of the Kununurra isolate (WA-99) was confirmed using sap transmission to indicator hosts, positive reactions with tospovirus serogroup IV-specific antibodies and CaCV-specific primers, and amino acid sequence comparisons that showed >97% identity with published CaCV nucleocapsid gene sequences. The reactions of indicator hosts to infection with WA-99 often differed from those of the type isolate from Queensland. The virus multiplied best when test plants were grown at warm temperatures. CaCV was not detected in samples collected in a survey of C. annuum crops planted in the Perth Metropolitan area.

Carrot as a natural host of Watermelon mosaic virus

Carrot was confirmed as a new natural and experimental host of Watermelon mosaic virus by serology, host reactions and sequence comparisons of the coat protein.

Herpesviral haematopoietic necrosis virus (CyHV-2) infection: case studies from commercial goldfish farms

Herpesviral haematopoietic necrosis is a disease of goldfish, Carassius auratus, caused by Cyprinid herpesvirus-2 (CyHV-2) infection. Quantitative PCR was carried out on tissue homogenates from healthy goldfish fingerlings, broodfish, eggs and fry directly sampled from commercial farms, from moribund fish submitted to our laboratory for disease diagnosis, and on naturally-infected CyHV-2 carriers subjected to experimental stress treatments. Healthy fish from 14 of 18 farms were positive with copy numbers ranging from tens to 10(7) copies mu g(-1) DNA extracted from infected fish. Of 118 pools of broodfish tested, 42 were positive. The CyHV-2 was detected in one lot of fry produced from disinfected eggs. Testing of moribund goldfish, in which we could not detect any other pathogens, produced 12 of 30 cases with 10(6)-10(8) copies of CyHV-2 mu g(-1) DNA extracted. Subjecting healthy CyHV-2 carriers to cold shock (22-10 degrees C) but not heat, ammonia or high pH, increased viral copy numbers from mean copy number (+/- SE) of 7.3 +/- 11 to 394 +/- 55 mu g(-1) DNA extracted after 24 h. CyHV-2 is widespread on commercial goldfish farms and outbreaks apparently occur when healthy carriers are subjected to a sharp temperature drop followed by holding at the permissive temperature for the disease.

Weed spread prevention: simple activities for field operations.

This paper discusses how spread of weeds can be minimised by improved knowledge of the weed’s ecology and dispersal, and by better surveillance and treatment methods. Undertaking simple prevention activities reduces the risk of spreading weeds with minimal costs to projects and they noted that field staff and researchers can inadvertently become vectors of weed spread if they do not take adequate precautions. The authors describe several techniques that can be adopted and reference their observations to the eradication program for Siam weed, Chromolaena odorata.

Post capture necrosis of the feet caused by soft-catch traps – incidents, cause and prevention.

When recapturing satellite collared wild dogs that had been trapped one month previous in padded foothold traps, we noticed varying degrees of pitting on the pads of their trapped paw. Veterinary advice, based on images taken of the injuries, suggests that the necrosis was caused by vascular compromise. Five of six dingoes we recaptured had varying degrees of necrosis restricted only to the trapped foot and ranging from single 5 mm holes to 25% sections of the toe pads missing or deformed, including loss of nails. The traps used were rubber-padded, two–coiled, Victor Soft Catch #3 traps. The springs are not standard Victor springs but were Beefer springs; these modifications slightly increase trap speed and the jaw pressure on the trapped foot. Despite this modification the spring pressure is still relatively mild in comparison to conventional long spring or four-coiled wild dog traps. The five wild dogs developing necrosis were trapped in November 2006 at 5-6 months of age. Traps were checked each morning so the dogs were unlikely to have been restrained in the trap for more than 12 hours. All dogs exhibited a small degree of paw damage at capture which presented itself as a swollen paw and compression at the capture point. In contrast, eight wild dogs, 7-8 month-old, were captured two months later in February. Upon their release, on advice from a veterinarian, we massaged the trapped foot to get blood flow back in to the foot and applied a bruise treatment (Heparinoid 8.33 mg/ml) to assist restoring blood flow. These animals were subsequently recaptured several months later and showed no signs of necrosis. While post-capture foot injuries are unlikely to be an issue in conventional control programs where the animal is immediately destroyed, caution needs to be used when releasing accidentally captured domestic dogs or research animals captured in rubber-padded traps. We have demonstrated that 7-8 month old dogs can be trapped and released without any evidence of subsequent necrosis following minimal veterinary treatment. We suspect that the rubber padding on traps may increase the tourniquet effect by wrapping around the paw and recommend the evaluation of offset laminated steel jaw traps as an alternative. Offset laminated steel jaw traps have been shown to be relatively humane producing as few foot injuries as rubber-jawed traps.

Variation in acquisition of Fiji disease virus by Perkinsiella saccharicida (Hemiptera: Delphacidae).

Fiji leaf gall, caused the Fiji disease virus (genus Fijivirus, family Reoviridae, FDV), is a serious disease of sugarcane, Saccharum officinarum L., in Australia and several other Asia-Pacific countries. In Australia FDV is transmitted only by the planthopper Perkinsiella saccharicida Kirkaldy (Hemiptera: Delphacidae), in a propagative manner. Successful transmission of FDV by single planthoppers confined to individual virus free plants is highly variable, even under controlled conditions. The research reported here addresses two possible sources of this variation: 1) gender, wing form, and life stage of the planthopper; and 2) genotype of the source plant. The acquisition of FDV by macropterous males, macropterous females, brachypterous females, and nymphs of P. saccharicida from infected plants was investigated using reverse transcription-polymerase chain reaction to diagnose FDV infection in the vector. The proportion of individuals infected with FDV was not statistically related to life stage, gender, or adult wing form of the vector. The acquisition of FDV by P. saccharicida from four cultivars of sugarcane was compared to assess the influence of plant genotype on acquisition. Those planthopper populations reared on diseased 'NCo310' plants had twice as many infected planthoppers as those reared on 'Q110', 'WD1', and 'WD2'. Therefore, variation in FDV acquisition in this system is not the result of variation in the gender, wing form and life stage of the P. saccharicida vectors. The cultivar used as the source plant to rear vector populations does affect the proportion of infected planthoppers in a population.