Epidemic potential of Zika virus in Australia: implications for blood transfusion safety.

BACKGROUND: Zika virus (ZIKV) is transfusion-transmissible. In Australia the primary vector, Aedes aegypti, is established in the north-east, such that local transmission is possible following importation of an index case, which has the potential to impact on blood transfusion safety and public health. We estimated the basic reproduction number (R 0 ) to model the epidemic potential of ZIKV in Australian locations, compared this with the ecologically similar dengue viruses (DENV), and examined possible implications for blood transfusion safety. STUDY DESIGN AND METHODS: Varying estimates of vector control efficiency and extrinsic incubation period, "best-case" and "worst-case" scenarios of monthly R 0 for ZIKV and DENV were modeled from 1996 to 2015 in 11 areas. We visualized the geographical distribution of blood donors in relation to areas with epidemic potential for ZIKV. RESULTS: Epidemic potential (R 0 > 1) existed for ZIKV and DENV throughout the study period in a number of locations in northern Australia (Cairns, Darwin, Rockhampton, Thursday Island, Townsville, and Brisbane) during the warmer months of the year. R 0 for DENV was greater than ZIKV and was broadly consistent with annual estimates in Cairns. Increased vector control efficiency markedly reduced the epidemic potential and shortened the season of local transmission. Australian locations that provide the greatest number of blood donors did not have epidemic potential for ZIKV. CONCLUSION: We estimate that areas of north-eastern Australia could sustain local transmission of ZIKV. This early contribution to understanding the epidemic potential of ZIKV may assist in the assessment and management of threats to blood transfusion safety.

No evidence for widespread Babesia microti transmission in Australia.

BACKGROUND: A fatal case of autochthonous Babesia microti infection was reported in Australia in 2012. This has implications for Australian public health and, given that babesiosis is transfusion transmissible, has possible implications for Australian blood transfusion recipients. We investigated the seroprevalence of antibodies to B. microti in Australian blood donors and in patients with clinically suspected babesiosis. STUDY DESIGN AND METHODS: Plasma samples (n = 7,000) from donors donating in at-risk areas and clinical specimens from patients with clinically suspected babesiosis (n = 29) were tested for B. microti IgG by immunofluorescence assay (IFA). IFA initially reactive samples were tested for B. microti IgG and IgM by immunoblot and B. microti DNA by polymerase chain reaction. RESULTS: Although five donors were initially reactive for B. microti IgG by IFA, none was confirmed for B. microti IgG (zero estimate; 95% confidence interval, 0%-0.05%) and all were negative for B. microti DNA. None of the patient samples had B. microti IgG, IgM, or DNA. CONCLUSIONS: This study does not provide evidence for widespread exposure to B. microti in Australian blood donors at local theoretical risk, nor does it provide evidence of B. microti infection in Australian patients with clinically suspected babesiosis. Given that confirmed evidence of previous exposure to B. microti was not seen, these data suggest that transmission of this pathogen is currently uncommon in Australia and unlikely to pose a risk to transfusion safety at present.

Ross River virus in Australian blood donors: possible implications for blood transfusion safety.

BACKGROUND: Emerging transfusion-transmissible pathogens, including arboviruses such as West Nile, Zika, dengue, and Ross River viruses, are potential threats to transfusion safety. The most prevalent arbovirus in humans in Australia is Ross River virus (RRV); however, prevalence varies substantially around the country. Modeling estimated a yearly risk of 8 to 11 potentially RRV-viremic fresh blood components nationwide. This study aimed to measure the occurrence of RRV viremia among donors who donated at Australian collection centers located in areas with significant RRV transmission during one peak season. STUDY DESIGN AND METHODS: Plasma samples were collected from donors (n = 7500) who donated at the selected collection centers during one peak season. Viral RNA was extracted from individual samples, and quantitative reverse transcription-polymerase chain reaction was performed. RESULTS: Regions with the highest rates of RRV transmission were not areas where donor centers were located. We did not detect RRV RNA among 7500 donations collected at the selected centers, resulting in a zero risk estimate with a one-sided 95% confidence interval of 0 to 1 in 2019 donations. CONCLUSION: Our results suggest that the yearly risk of collecting a RRV-infected blood donation in Australia is low and is at the lower range of previous risk modeling. The majority of Australian donor centers were not in areas known to be at the highest risk for RRV transmission, which was not taken into account in previous models based on notification data. Therefore, we believe that the risk of RRV transfusion transmission in Australia is acceptably low and appropriately managed through existing risk management, including donation restrictions and recall policies.

Hepatitis E virus RNA in Australian blood donations.

BACKGROUND: Hepatitis E virus (HEV) poses a risk to transfusion safety. In Australia, locally acquired HEV is rare and cases are mainly reported in travelers returning from countries endemic for HEV. The risk posed by HEV to transfusion safety in Australia is unknown; therefore, we aimed to measure the rate of current HEV infection in Australian blood donations. STUDY DESIGN AND METHODS: A total of 14,799 blood donations were tested for HEV RNA by transcription-mediated amplification, with confirmatory testing by reverse transcription-polymerase chain reaction. Viral load quantification and phylogenetic analysis was performed on HEV RNA-positive samples. RESULTS: One (0.0068%; 95% confidence interval [CI], 0.0002%-0.0376%) sample was confirmed positive for HEV RNA, resulting in a risk of collecting a HEV-viremic donation of 1 in 14,799 (95% CI, 1 in 584,530 to 1 in 2,657). The viral load in this sample was approximately 15,000 IU/mL, and it was determined to be Genotype 3. DISCUSSION: Our finding of 1 in 14,799 Australian donations positive for HEV RNA is lower than that from many other developed countries; this is consistent with the relatively low seroprevalence in Australia. As this HEV RNA-positive sample was Genotype 3, it seems likely that this infection was acquired through zoonotic transmission, either within Australia or overseas in a developed nation. HEV has the potential to pose a risk to transfusion safety in Australia; however, additional, larger studies are required to quantify the magnitude of this risk.

Detection of emergent strains of West Nile virus with a blood screening assay.

BACKGROUND: West Nile virus (WNV) is a threat to transfusion safety. WNV Kunjin strain (WNVKUN ) is endemic across parts of Australia; however, human infection is believed to be infrequent and is often associated with relatively minor symptoms. A virulent strain, closely related to WNVKUN (termed WNVNSW2011 ) was recently identified as the etiologic agent of encephalitis in Australian horses. The aim of this project was to investigate whether a commercially available WNV blood screening assay can detect different strains of WNVKUN , including the virulent WNVNSW2011 , in human blood donor samples. STUDY DESIGN AND METHODS: Plasma samples were spiked with four different strains of WNVKUN , as well as a prototype WNV strain, at high, medium, and low viral loads. Spiking was confirmed with real-time reverse transcription-polymerase chain reaction (RT-PCR), before testing with the Procleix WNV transcription-mediated amplification (TMA) blood screening assay (Grifols). RESULTS: All WNV strains used were detectable by RT-PCR after being spiked into plasma. Additionally, all viral spiked samples were reactive by WNV TMA. CONCLUSION: We experimentally demonstrate that a commercially available WNV blood screening assay can detect different strains of WNVKUN . Given that WNV can be transfusion transmissible, it is essential to confirm that emergent strains are detectable by existing blood screening methods.

Hepatitis E virus seroepidemiology: a post-earthquake study among blood donors in Nepal.

BACKGROUND: As one of the causative agents of viral hepatitis, hepatitis E virus (HEV) has gained public health attention globally. HEV epidemics occur in developing countries, associated with faecal contamination of water and poor sanitation. In industrialised nations, HEV infections are associated with travel to countries endemic for HEV, however, autochthonous infections, mainly through zoonotic transmission, are increasingly being reported. HEV can also be transmitted by blood transfusion. Nepal has experienced a number of HEV outbreaks, and recent earthquakes resulted in predictions raising the risk of an HEV outbreak to very high. This study aimed to measure HEV exposure in Nepalese blood donors after large earthquakes. METHODS: Samples (n = 1,845) were collected from blood donors from Kathmandu, Chitwan, Bhaktapur and Kavre. Demographic details, including age and sex along with possible risk factors associated with HEV exposure were collected via a study-specific questionnaire. Samples were tested for HEV IgM, IgG and antigen. The proportion of donors positive for HEV IgM or IgG was calculated overall, and for each of the variables studied. Chi square and regression analyses were performed to identify factors associated with HEV exposure. RESULTS: Of the donors residing in earthquake affected regions (Kathmandu, Bhaktapur and Kavre), 3.2% (54/1,686; 95% CI 2.7-4.0%) were HEV IgM positive and two donors were positive for HEV antigen. Overall, 41.9% (773/1,845; 95% CI 39.7-44.2%) of donors were HEV IgG positive, with regional variation observed. Higher HEV IgG and IgM prevalence was observed in donors who reported eating pork, likely an indicator of zoonotic transmission. Previous exposure to HEV in Nepalese blood donors is relatively high. CONCLUSION: Detection of recent markers of HEV infection in healthy donors suggests recent asymptomatic HEV infection and therefore transfusion-transmission in vulnerable patients is a risk in Nepal. Surprisingly, this study did not provide evidence of a large HEV outbreak following the devastating earthquakes in 2015.

Implications of dengue outbreaks for blood supply, Australia.

Dengue outbreaks have increased in size and frequency in Australia, and transfusion-transmitted dengue poses a risk to transfusion safety. Using whole blood samples collected during the large 2008-2009 dengue epidemic, we estimated the risk for a dengue-infectious blood donation as ≈1 in 7,146 (range 2,218-50,021).

Past and future epidemic potential of chikungunya virus in Australia.

BACKGROUND: Australia is theoretically at risk of epidemic chikungunya virus (CHIKV) activity as the principal vectors are present on the mainland Aedes aegypti) and some islands of the Torres Strait (Ae. aegypti and Ae. albopictus). Both vectors are highly invasive and adapted to urban environments with a capacity to expand their distributions into south-east Queensland and other states in Australia. We sought to estimate the epidemic potential of CHIKV, which is not currently endemic in Australia, by considering exclusively transmission by the established vector in Australia, Ae. aegypti, due to the historical relevance and anthropophilic nature of the vector. METHODOLOGY/PRINCIPAL FINDINGS: We estimated the historical (1995-2019) epidemic potential of CHIKV in eleven Australian locations, including the Torres Strait, using a basic reproduction number equation. We found that the main urban centres of Northern Australia could sustain an epidemic of CHIKV. We then estimated future trends in epidemic potential for the main centres for the years 2020 to 2029. We also conducted uncertainty and sensitivity analyses on the variables comprising the basic reproduction number and found high sensitivity to mosquito population size, human population size, impact of vector control and human infectious period. CONCLUSIONS/SIGNIFICANCE: By estimating the epidemic potential for CHIKV transmission on mainland Australia and the Torres Strait, we identified key areas of focus for controlling vector populations and reducing human exposure. As the epidemic potential of the virus is estimated to rise towards 2029, a greater focus on control and prevention measures should be implemented in at-risk locations.

Estimation of mosquito-borne and sexual transmission of Zika virus in Australia: Risks to blood transfusion safety.

BACKGROUND: Since 2015, Zika virus (ZIKV) outbreaks have occurred in the Americas and the Pacific involving mosquito-borne and sexual transmission. ZIKV has also emerged as a risk to global blood transfusion safety. Aedes aegypti, a mosquito well established in north and some parts of central and southern Queensland, Australia, transmits ZIKV. Aedes albopictus, another potential ZIKV vector, is a threat to mainland Australia. Since these conditions create the potential for local transmission in Australia and a possible uncertainty in the effectiveness of blood donor risk-mitigation programs, we investigated the possible impact of mosquito-borne and sexual transmission of ZIKV in Australia on local blood transfusion safety. METHODOLOGY/PRINCIPAL FINDINGS: We estimated 'best-' and 'worst-' case scenarios of monthly reproduction number (R0) for both transmission pathways of ZIKV from 1996-2015 in 11 urban or regional population centres, by varying epidemiological and entomological estimates. We then estimated the attack rate and subsequent number of infectious people to quantify the ZIKV transfusion-transmission risk using the European Up-Front Risk Assessment Tool. For all scenarios and with both vector species R0 was lower than one for ZIKV transmission. However, a higher risk of a sustained outbreak was estimated for Cairns, Rockhampton, Thursday Island, and theoretically in Darwin during the warmest months of the year. The yearly estimation of the risk of transmitting ZIKV infection by blood transfusion remained low through the study period for all locations, with the highest potential risk estimated in Darwin. CONCLUSIONS/SIGNIFICANCE: Given the increasing demand for plasma products in Australia, the current strategy of restricting donors returning from infectious disease outbreak regions to source plasma collection provides a simple and effective risk management approach. However, if local transmission was suspected in the main urban centres of Australia, potentially facilitated by the geographic range expansion of Ae. aegypti or Ae. albopictus, this mitigation strategy would need urgent review.

Hepatitis E virus infections in travellers: assessing the threat to the Australian blood supply.

BACKGROUND: In many developed countries hepatitis E virus (HEV) infections have occurred predominantly in travellers to countries endemic for HEV. HEV is a potential threat to blood safety as the virus is transfusion-transmissible. To minimise this risk in Australia, individuals diagnosed with HEV are deferred. Malarialdeferrals, when donors are restricted from donating fresh blood components following travel toanareain which malaria is endemic, probably also decrease the HEV risk, by deferring donors who travel to many countries also endemic for HEV. The aim of this study is to describe overseas-acquired HEV cases in Australia, in order to determine whether infection in travellers poses a risk to Australian blood safety. MATERIALS AND METHODS: Details of all notified HEV cases in Australia from 2002 to 2014 were accessed, and importation rates estimated. Countries in which HEV was acquired were compared to those for which donations are restricted following travel because of a malaria risk. RESULTS: Three hundred and thirty-two cases of HEV were acquired overseas. Travel to India accounted for most of these infections, although the importation rate was highest for Nepal and Bangladesh. Countries for which donations are restricted following travel due to malaria risk accounted for 94% of overseas-acquired HEV cases. DISCUSSION: The vast majority of overseas-acquired HEV infections were in travellers returning from South Asian countries, which are subject to donation-related travel restrictions for malaria. This minimises the risk HEV poses to the Australian blood supply.

A Comparative Study of Assay Performance of Commercial Hepatitis E Virus Enzyme-Linked Immunosorbent Assay Kits in Australian Blood Donor Samples.

Hepatitis E virus (HEV) is transfusion-transmissible and therefore poses a risk to blood transfusion safety. Seroprevalence studies are useful for estimating disease burden and determining risk factors. Considerable variability in the sensitivity of HEV antibody detection assays exists. This study aimed to compare the performances of commercially available HEV enzyme-linked immunosorbent assays (ELISA) in Australian blood donor samples. Plasma samples that tested positive (n = 194) or negative (n = 200) for HEV IgG (Wantai HEV IgG ELISA) were selected. Of the 194 HEV IgG positive samples, 4 were positive for HEV IgM (Wantai HEV IgM ELISA). All samples were tested with the MP Diagnostics: HEV IgG ELISA, total (IgG, IgM, and IgA) HEV antibody ELISA, and HEV IgM ELISA. Of the 194 Wantai HEV IgG positive samples, 92 (47%) tested positive with the MP Diagnostics HEV IgG ELISA (κ = 0.47) and 126 (65%) with MP Diagnostics total HEV antibody assay (κ = 0.65). There was poor agreement between Wantai and MP Diagnostics HEV IgM assays. This study demonstrated poor agreement between the assays tested. These observations are consistent with previous reports demonstrating significant variability between HEV ELISAs, highlighting that results of HEV serology should be interpreted with caution.

Epidemic Potential for Local Transmission of Zika Virus in 2015 and 2016 in Queensland, Australia.

INTRODUCTION: Zika virus could be transmitted in the state of Queensland, Australia, in parts of the state where the mosquito vectors are established. METHODS: We assessed the epidemic potential of Zika in Queensland from January 2015 to August 2016, and estimate the epidemic potential from September to December 2016, by calculating the temperature-dependent relative vectorial capacity (rVc), based on empirical and estimated parameters. RESULTS: Through 2015, we estimated a rVc of 0.119, 0.152, 0.170, and 0.175, respectively in the major cities of Brisbane, Rockhampton, Cairns, and Townsville. From January to August 2016, the epidemic potential trend was similar to 2015, however the highest epidemic potential was in Cairns. During September to November 2016, the epidemic potential is consistently the highest in Cairns, followed by Townsville, Rockhampton and Brisbane. Then, from November to December 2016, Townsville has the highest estimated epidemic potential. DISCUSSION: We demonstrate using a vectorial capacity model that ZIKV could have been locally transmitted in Queensland, Australia during 2015 and 2016. ZIKV remains a threat to Australia for the upcoming summer, during the Brazilian Carnival season, when the abundance of vectors is relatively high. Understanding the epidemic potential of local ZIKV transmission will allow better management of threats to blood safety and assessment of public health risk.

Mitigating the Risk of Transfusion-Transmitted Dengue in Australia.

Dengue viruses (DENV 1-4) are a risk to transfusion safety, with several transfusion-transmitted (TT) cases reported globally. DENV 1-4 are endemic in over 100 countries, with seasonal outbreaks occurring in northeastern Australia. To mitigate TT-DENV risk in Australia, fresh blood components are not manufactured from donors returning from any area (domestic/overseas) with known dengue transmission. Alternatively, TT-DENV risk may be mitigated using an appropriate blood donor screening assay. We aimed to determine the rate of dengue infection in donors during dengue outbreaks in Australia. Plasma samples were collected from blood donors during local dengue outbreaks. All samples were tested for the presence of DENV RNA and selected samples were tested for DENV antigen (nonstructural protein 1, NS1) with two assays. No donors residing in high risk areas had detectable levels of DENV RNA or NS1 and no cases of DENV viremia were detected in blood donors residing in areas of Australia experiencing DENV outbreaks. Definitive conclusions could not be drawn from this study; however, the lack of detection of DENV RNA or antigen in donations suggests that the current risk of TT-DENV is low and maintaining the fresh component restriction for "at-risk" donors is appropriate.

Hepatitis E virus: do locally acquired infections in Australia necessitate laboratory testing in acute hepatitis patients with no overseas travel history?

Hepatitis E virus (HEV) is emerging as a global public health threat. Water-borne HEV outbreaks are common in developing countries and are associated with genotypes 1 and 2. In industrialised countries, sporadic cases of zoonotic transmission associated with genotypes 3 and 4 are increasingly being reported. Transfusion- and transplantation-transmitted HEV have been documented, although ingestion of contaminated food is thought to be the major transmission route. Severe disease is possible and chronic hepatitis infection occurs in solid-organ-transplant recipients and in patients with immunosuppressive disorders. In Australia, HEV cases are mainly travellers returning from disease endemic countries. Indeed, there are few reported cases of locally acquired HEV. Pigs in Australia have been shown to be infected with HEV, which indicates the possibility of zoonotic transmission. The extent of locally acquired infection is not known, however it may be greater than expected and may necessitate laboratory testing in patients reporting no overseas travel.

Innate Immunity in Lobsters: Partial Purification and Characterization of a Panulirus cygnus Anti-A Lectin.

A lectin detected in haemolymph from the Australian spiny lobster Panulirus cygnus agglutinated human ABO Group A cells to a higher titre than Group O or B. The lectin also agglutinated rat and sheep erythrocytes, with reactivity with rat erythrocytes strongly enhanced by treatment with the proteolytic enzyme papain, an observation consistent with reactivity via a glycolipid. The lectin, purified by affinity chromatography on fixed rat-erythrocyte stroma, was inhibited equally by N-acetylglucosamine and N-acetylgalactosamine. Comparison of data from gel filtration of haemolymph (behaving as a 1,800,000 Da macromolecule), and polyacrylamide gel electrophoresis of purified lectin (a single 67,000 Da band), suggested that in haemolymph the lecin was a multimer. The purified anti-A lectin autoprecipitated unless the storage solution contained chaotropic inhibitors (125 mmol/L sucrose: 500 mmol/L urea). The properties of this anti-A lectin and other similar lectins are consistent with a role in innate immunity in these invertebrates.

Borna disease virus: evidence of naturally-occurring infection in cats in Australia.

In Europe, Borna disease virus (BDV) infection has been linked with staggering disease. The aim of this study was serological investigation for BDV infection in Australian cats. De-identified sera were obtained from domestic cats presented at various veterinary clinics. BDV antigen levels were measured by a monoclonal antibody-based ELISA. Antibody to BDV measured semiquantitatively by ELISA was detected in 0.8% of cats from South Australia and 3.2% of animals from NSW Confirmatory assays for ELISA positive samples included Western blot and immunofluorescence assay (IFA) with BDV-specific staining. Seven BDV-antigen positive sera (2.4%) were identified in sera from cats from New South Wales (NSW). In blinded testing, amongst a large number of negative results, repeat submissions over a seven-month period from a cat co-infected with Feline Immunodeficiency Virus (FIV) were BDV-antigen positive. Anti-BDV antibody detected in this cat by ELISA was confirmed by Western blot (p24/ p40/p56) and IFA. For 4 other anti-BDV ELISA-positive samples, specific reactions with BDV proteins were observed by Western blot. Ten other anti-BDV ELISA-positive samples were IFA positive. These data provide consistent serological evidence that, while horses in Australia are free of BDV infection, there may be a low rate of BDV infection in cats.

Human Borna disease virus infection in Australia: serological markers of infection in multi-transfused patients.

Borna disease virus (BDV) causes neurological disease in horses, however, there is no consensus as to the extent or significance of human infection. BDV antigen levels in plasma (BDVpAg) and anti-BDV were measured by ELISAs. Confirmation was by Western blot (WB), immunofluorescence assay (IFA) or BDV-peptide-epitope ELISA. For 42 volunteers psychiatrically-defined as non-depressed (82 samples) neither BDVpAg nor anti-BDV was detected. For 104 patients with diagnosed depression (290 samples) 1 was BDVpAg positive and 5 anti-BDV positive, one epitope-e8 positive and 4 IFA positive, with 96% concordance for repeat samples. No BDVpAg was detected in 214 pregnant women, 2 were anti-BDV positive, one WB-confirmed (p24/p40). For 219 donors 2 were BDVpAg positive with anti-BDV detected in 5 (2.3%) one IFA 1:10, another IFA 1:40/epitope-e8 positive. In multitransfused patients, 3/168 were BDV pAg positive, with 14/168 anti-BDV positive, 1 epitope-e8 positive, 2 WB positive and 1 IFA 1:10. In BDVpAg positive multi-transfused patients there was an elevated risk of transaminitis. In one case, a patient BDV-negative prior to transfusion was BDVpAg positive for several months posttransfusion (associated with transaminitis). These data provide serological evidence, supported by confirmatory assays and repeat-sample concordance, of BDV infection in Australia, particularly in multi-transfused patients.

Inactivation of two haemolytic toxin genes in Aeromonas hydrophila attenuates virulence in a suckling mouse model.

The contribution of two unrelated Aeromonas hydrophila beta-haemolytic toxins to virulence was assessed in a suckling mouse model. The first haemolysin gene, isolated from an A. hydrophila A6 cosmid bank, encoded a potential gene product of 621 amino acids and a predicted molecular size of 69.0 kDa. The inferred amino acid sequence showed 89% identity to the AHH1 haemolysin of A. hydrophila ATCC 7966, and 51% identity to the HlyA haemolysin of Vibrio cholerae EI Tor strain O17. The second haemolysin gene (designated aerA), which encodes aerolysin, a pore-forming toxin, was partially cloned by PCR for the purpose of mutant construction. This PCR product was a 1040 bp fragment from the C-terminal region of aerA. It is proposed that the 69.0 kDa V. cholerae-HlyA-like haemolysin gene be termed hlyA to contrast with the aerA terminology for the aerolysin. A suicide vector was used to inactivate both the hlyA and aerA genes in A. hydrophila A6. When assessed in the suckling mouse model, only the hlyA aerA double mutant showed a statistically significant reduction in virulence--a 20-fold change in LD50 (Scheffe test, P < 0.05). Cytotoxicity to buffalo green monkey kidney cell monolayers and haemolysis on horse blood agar were eliminated only in the hlyA aerA double mutants. This is the first report of cloning and mutagenesis of two unrelated haemolytic toxin genes in the same strain of a mesophilic aeromonad. For A. hydrophila, a two-toxin model provides a more complete explanation of virulence.