Sentinel Chicken Surveillance Program in Australia, July 2002 to June 2003

Detection of flavivirus seroconversions in sentinel chicken flocks located throughout Australia is used to provide an early warning of increased levels of Murray Valley encephalitis (MVE) and Kunjin (KUN) virus activity in the region. During the 2002-2003 season low levels of flavivirus activity were detected in northern Australia compared to previous years. MVE and KUN virus activity was detected in the Kimberley and Pilbara regions of Western Australia and the Northern Territory but not in north Queensland, New South Wales or Victoria. This is similar to the previous season. There were no reported cases of disease caused by either virus.     

Surface-based labeling of cortical anatomy using a deformable atlas

With regard to BHV1 eradication programs in cattle it is important to know whether sheep can be a reservoir of BHV1. We therefore performed an experiment that consisted of three phases. In phase 1, 10 sheep were inoculated with high doses of BHV1 and kept in close contact with 5 sheep and 5 calves. All inoculated sheep excreted BHV1 between 8 and 15 days post inoculation and seroconverted. Although BHV1 was isolated from the nasal mucosa of 3 out of 5 sentinel sheep, none of the sentinel sheep produced antibodies against BHV1. One sentinel calf excreted BHV1 through days 12-17; the remaining 4 calves excreted BHV1 between days 18 and 24 suggesting that the first calf was infected by sheep and the remaining 4 sentinel calves were infected by that calf and not by sheep. The bacic reproduction ratio (R0) of BHV1 between sheep and calves was estimated at 0.1, and among calves it was estimated at > or = 9. In phase 2, all inoculated sheep were treated with dexamethasone and kept in close contact with 5 sheep and 5 calves. All dexamethasone treated sheep re-excreted BHV1 over a 6- to 9-day period. None of the sentinel animals seroconverted. In phase 3, the sentinel sheep and calves of phase 1 were kept in two groups and were treated with dexamethasone. None of the sentinel sheep re-excreted BHV1, whereas 3 out of 5 sentinel calves did. It is concluded that while BHV1 infection in sheep is possible, BHV1 does not spread from sheep easily to cattle.     

Arboviruses and arbovirus infections in the forest steppe zone of Ukraine

New active natural foci of the tick-borne encephalitis, West Nile, California serologic group (CSG) and Batai viruses have been identified as a result of comprehensive virologic and serologic investigations in the forest-steppe zone of Ukraine. These observations were confirmed by the results of these pathogens study and identification of the corresponding antigens in natural biological substrates and in the blood of ill people. Several human pathogenetic viruses, including Inko, Snow hoc hare with CSG and Crimean hemorrhagic fever were found for the first time in the forest-steppe zone. Viruses populations circulating there are heterogeneous according to their genetic properties. New data concerning their ecology were obtained. A close etiological relation between the acute seasonal febrile diseases and the above mentioned arboviruses was found. Arboviral infections from 23.6% of the total amount of spring-summer-autumn febrile diseases. The West Nile fever (53.1%) is the leading arboviral infection in the forest-steppe zone. A quarter of all arboviral infections is represented by tick-borne encephalitis. Diagnostic preparations have been made and the available methods of laboratory diagnostics of the arboviral infections have been improved.     

Recent acute and subacute mycotoxicoses recognized in France

Successful investigation and prevention of mycotoxic problems requires close collaboration between scientists from several disciplines ranging from agronomists and technologists required during production of food and feeds, to toxicologists and pathologists examining the effects of mycotoxins on animals and man. Zootoxic metabolites following fungal infection result from four general mechanisms: (i) secondary fungal metabolism (mycotoxins, eg, aflatoxins); (ii) bioconversion of vegetal compounds (eg, dicoumarol); (iii) plant reactions (phytoalexins, eg, coumestrol); and (iv) plant-fungus associations (endophytes, eg, Acremonium/Festuca). In reported pathologic field cases, close cooperation through a selected veterinary network has allowed diagnosis of acute and subacute mycotoxicoses in France. Natural stachybotryotoxicosis may not be limited only to cold climates, but may also occur in mild and warm ones (eg, south west of France, Morocco). A considerable variation was observed in symptoms and lesions depending on toxin levels, ranging from a poor performance in a horse race to a general haemorrhagic syndrome. Several cases of acute equine leucoencephalomalacia, characterized by pathognomonic lesions and recently supported by fumonisin analysis, have been diagnosed in the southern part of France and other countries (eg, New Caledonia and the Ivory Coast). Facial eczema in sheep is endemic in the Basque country, as a result of specific bioclimatic and zootechnic conditions. Reproductive disorders in sheep, cattle, goats and rabbits have been associated with high levels of coumestrol in alfalfa, clover and their derivatives. A few cases of fescue foot disease, associated with the endophyte Acremonium, have been diagnosed recently. In addition, several nervous disorders may be due to unknown mycotoxins. These acute or subacute mycotoxicoses suggest a potentially widespread occurrence of low level toxins and insidious asymptomatic mycotoxicoses, and justify interdisciplinary research in order to improve diagnosis and preventative measures.     

United front--veterinary and medical collaboration

Four cases of concomitant animal and human Salmonellosis were investigated. Liaison took place between veterinary, public health medical and environmental health professionals. An epidemiological association between veterinary and medical disease outbreaks was established following cases in a dairy unit, a poultry unit, a calf rearing unit and one pig and dairy unit (on the same farm). In three cases clinical disease in animals preceded clinical disease in humans while in the fourth case, the poultry unit, salmonella isolations from poultry carcasses coincided with clinical salmonellosis in a human working with the live poultry. Important epidemiological factors are identified. The problems of delay in seeking veterinary advice, compartmentalisation of veterinary and medical practices, and the benefits of direct collaboration between veterinary and medical professionals in the event of a diagnosis of salmonellosis in animals and/or humans are highlighted. A collaborative reporting and liaison model is proposed.     

Vectors vs. humans in Australia--who is on top down under? An update on vector-borne disease and research on vectors in Australia

Australia has a diversity of vectors and vector-borne human diseases. Mosquito-borne arboviruses are of greatest concern, but there are issues with other vector and pathogen systems. Mosquitoes were responsible for more than 35,000 cases of Ross River virus during 1991-1997. Barmah Forest virus is increasing nationwide, and unidentified bunyaviruses suspected of causing illness have been isolated. Cases of Murray Valley encephalitis have occurred in 14 of the past 20 years in northern Australia. Dengue is a continuing problem for northern Queensland, with various serotypes being active. Japanese encephalitis has appeared in the Torres Strait Islands and threatens mainland Australia. Although malaria is eradicated, almost 1,000 cases are imported annually and occasional cases of local transmission occur. With ticks, paralysis in children occurs annually in eastern Australia. Tick typhus (Queensland Tick Typhus--Rickettsia australis) occurs down the east coast, and (Flinders Island Spotted Fever--Rickettsia honei) in Bass Strait and probably Tasmania. Lyme disease is reported but its presence is controversial. Fleas were responsible for a recent outbreak of murine typhus (Rickettsia typhi) in Western Australia. Mites cause scrub typhus (Orientia tsutsugamushi), and there was a recent fatality in the Northern Territory. Overall, resources for investigation and control of vector-borne disease have generally been meager. However, various avenues of basic and applied research have been pursued, and have included investigations into mosquito ecology, vector competence, disease epidemiology, and vector control. Disease surveillance programs vary between states, and mosquito control programs are organized and effective in only a few regions. There are concerns for import of vectors such as Aedes albopictus and export of pathogens such as Ross River virus; the former has occurred but the species has not become established, and the latter has occurred and has resulted in a major outbreak in the South Pacific. The predicted scenarios of increased temperature and rainfall with global warming are also causing concern for increases in vector-borne diseases, particularly the endemic arboviruses. Interest by health authorities is gravitating more towards epidemiological reporting and less towards public health action. In many respects, humans have much to do to get 'on top' of vectors and their pathogens 'down under' in Australia.     

Neutralizing antibodies protect against lethal flavivirus challenge but allow for the development of active humoral immunity to a nonstructural virus protein

Antibody-mediated neutralization of viruses has been extensively studied in vitro, but the precise mechanisms that account for antibody-mediated protection against viral infection in vivo still remain largely uncharacterized. The two points under discussion are antibodies conferring sterilizing immunity by neutralizing the virus inoculum or protection against the development of disease without complete inhibition of virus replication. For tick-borne encephalitis virus (TBEV), a flavivirus, transfer of neutralizing antibodies specific for envelope glycoprotein E protected mice from subsequent TBEV challenge. Nevertheless, short-term, low-level virus replication was detected in these mice. Furthermore, mice that were exposed to replicating but not to inactivated virus while passively protected developed active immunity to TBEV rechallenge. Despite the priming of TBEV-specific cytotoxic T cells, adoptive transfer of serum but not of T cells conferred immunity upon naive recipient mice. These transferred sera were not neutralizing and were predominantly specific for NS1, a nonstructural TBEV protein which is expressed in and on infected cells and which is also secreted from these cells. Results of these experiments showed that despite passive protection by neutralizing antibodies, limited virus replication occurs, indicating protection from disease rather than sterilizing immunity. The protective immunity induced by replicating virus is surprisingly not T-cell mediated but is due to antibodies against a nonstructural virus protein absent from the virion.     

Isolation of cytopathic small round virus (Aichi virus) from Pakistani children and Japanese travelers from Southeast Asia

Aichi virus was isolated in Vero cells from 5 (2.3%) of 222 Pakistani children with gastroenteritis but none was found in 91 healthy children. Aichi virus was also isolated from 5 (0.7%) of 722 Japanese travelers returned from tours to Southeast Asian countries and complained of gastrointestinal symptoms at the quarantine station of Nagoya International Airport in Japan. Of 5 Japanese travelers, 3 were returning from Indonesia, and 2 from Thailand or Malaysia. These results indicate that Aichi virus or a similar agent is endemic in Southeast Asian countries and is a cause of gastrointestinal symptoms in children in these areas or in Japanese travelers who visit there.     

The Hydrachnidae water mites of southwestern Siberia in relation to their participation in arbovirus circulation

The phenomenon of Hydrachnidae association with the tick-borne encephalitic viruses complex has been found out during the study of the role of the Hydrachnidae in the arboviruses circulation. We investigated the fauna, studied the quantity variation and trophic relations of these arthropods and blood-sucking Diptera. It was revealed no trophic relations between blood-sucking Diptera and mite species, where TBE strains were isolated from. On the basis of faunistic and virological study we suppose, that Hydroacarinae got an infection with the virus in the nymphal and imago stages, as well as larvae of mosquitos. Authors also note, that trophic relations between blood-sucking Diptera and chiggers (Trombidiidae) may be important in the arboviruses ecology.     

In utero medroxyprogesterone exposure after contraceptive failure

An investigation was conducted to assess the prevalence of Akabane virus antibodies in domestic ruminants from different ecological zones of Sudan. Neutralizing antibodies were demonstrated in sheep, goats and cattle sampled between 1979 and 1980 from El Obeid, Nyala, Kassala, Jonglei and Sennar. The highest prevalence was in Jonglei where 27% of six sheep, 36% of eleven goats and 47% of 90 cattle had antibodies to the virus. Although antibodies were demonstrated in 8% of 79 dams and 15% of 70 dams of two sentinel calf herds in Central Sudan at Shambat and Um Benein, respectively, none of their sentinel calves sampled between 1981 and 1983 had antibodies. Antibodies were subsequently detected in 8 (14%) out of 57 calves from Shambat and 5 (12%) out 40 from Um Benein of the random samples collected during 1985 from 1-3 year old calves. The implications of these results are discussed.     

Outcome criteria for lupus nephritis trials: a critical overview

OBJECTIVE: To study the clinical signs following bluetongue virus serotypes 1 and 3 infection in Poll Dorset sheep. DESIGN: A clinical and pathological study. PROCEDURE: Twenty Poll Dorset sheep were inoculated with bluetongue virus serotypes 1 or 3, each inoculum having a different passage history. The sheep were examined daily and their clinical appearance and rectal temperatures recorded. Heparinised and non-heparinised blood samples were taken at intervals for virological and serological study. Gross pathological findings were recorded for several sheep at necropsy and tissue samples were collected from three sheep for virological studies. RESULTS: All inoculated sheep developed clinical disease. The clinical signs and gross pathological changes varied considerably but were consistent with damage to the vascular endothelial system. There was a decline in the titres of infectious bluetongue virus and of antigen in tissues collected between 7 and 12 days after infection. CONCLUSIONS: The severity of disease was related to the speed of onset and duration of pyrexia and not the development or titre of viraemia. Generally, those animals with sensitive mouths, depression, coronitis, recumbency and reluctance to move were the most debilitated. Whole blood was the most reliable source of infectious virus from acutely and chronically infected and convalescent animals. However, tissue samples particularly spleen, collected from dead or killed animals suffering from either peracute or acute forms of disease were most appropriate for the rapid confirmation of a clinical diagnosis.     

Pathological and epidemiological aspects of the coexistence of maedi-visna and sheep pulmonary adenomatosis

Between 1982 and 1991, 159 sheep suffering from chronic respiratory disease were subjected to clinical, pathological, histopathological and serological examination. Maedi was diagnosed in 82 sheep and sheep pulmonary adenomatosis (SPA) in another 59. Forty-one of the latter (69.5 per cent) were seropositive for maedi-visna (MV) virus infection, but only six (10.2 per cent) showed concurrent lung lesions of maedi. Even disregarding the MV seronegative sheep and those younger than two years old, the rate of concurrent maedi lesions did not exceed 18 per cent. During a similar period, 5060 sheep from 161 flocks (86 of which also provided the 159 affected animals) were tested for antibodies to MV virus. The average seroprevalence of MV virus infection among flocks in which SPA was detected was 66.4 per cent, whereas in those in which SPA could not be demonstrated, and in those in which necropsies were not performed, the levels of MV virus infection were 55.1 per cent and 43.6 per cent, respectively. The effect of SPA on the seroprevalence of MV virus infection was independent of other factors, such as breed of sheep or the size of the flocks. These results provide evidence that SPA plays a role in the spread of MV virus infection, although a synergistic effect of the simultaneous infection on the expression of concurrent lesions does not seem to occur.     

Ruminant pestiviruses

The ruminant pestiviruses, bovine virus diarrhoea virus (BVDV) and border disease virus (BDV) are highly successful and important pathogens which infect ruminant species worldwide. Although the serological relationships among ruminant pestiviruses require further clarification, there is growing evidence for two antigenic groups, one of which predominates in cattle and one in sheep. The success of pestiviruses stems from the ability of the non-cytopathic (NCP) biotype of the virus to cross the placenta and establish a persistent infection (PI) in the developing foetus. This biotype should be regarded as the 'normal' biotype with the cytopathic (CP) biotype being an abnormal virus that is usually isolated only from PI animals dying from mucosal disease. Recent molecular evidence points to CP viruses arising from their NCP counterparts by recombination events that include the insertion of host RNA and/or the duplication of viral RNA sequences. However, the biological mechanism through which CP viruses kill cells remains unknown. Virtually all CP and NCP viruses cause only mild, transient clinical symptoms in healthy adult animals and stimulate a protective immune response. Despite the urgent requirement for a safe, effective vaccine, there is still no commercial vaccine that has been shown to immunize dams so that foetal infection is prevented. In the absence of an effective vaccine, reliable diagnostic techniques are essential to implement effective control measures. There is now a range of monoclonal antibody-based enzyme-linked immunosorbent assays for identifying PI or convalescent animals. These tests are specific, rapid, sensitive and reliable but may themselves become redundant as they are superceded by ever-increasing molecular biology-based techniques.     

Monthly distribution of menarche in three provinces of north Italy

The yellow fever (YF) virus is the prototype flavivirus. The use of molecular techniques has unraveled the basic mechanisms of viral genome structure and expression. Recent trends in flavivirus research include the use of infectious clone technology with which it is possible to recover virus from cloned cDNA. Using this technique, mutations can be introduced at any point of the viral genome and their resulting effect on virus phenotype can be assessed. This approach has opened new possibilities to study several biological viral features with special emphasis on the issue of virulence/attenuation of the YF virus. The feasibility of using YF virus 17D vaccine strain, for which infectious cDNA is available, as a vector for the expression of heterologous antigens is reviewed.     

Ticks, Lyme disease spirochetes, trypanosomes, and antibody to encephalitis viruses in wild birds from coastal Georgia and South Carolina

Ticks and blood samples were collected from wild birds mist-netted on St. Catherine's Island, Georgia, and at the Wedge Plantation in coastal South Carolina in 1994 and 1995. Immature stages of 5 species of ixodid ticks were recovered from 10 of 148 (7%) birds belonging to 6 species in Georgia, whereas 6 ixodid species were recovered from 45 of 259 (17%) birds representing 10 avian species in South Carolina. Borrelia burgdorferi sensu lato was isolated from 27 of 120 (23%) screened ticks (Ixodes scapularis and Ixodes minor) recovered from South Carolina birds, but from none of 16 screened ticks removed from Georgia birds. This spirochete was also isolated from 1 of 97 (1%) birds in South Carolina. In 1995, neither eastern equine encephalitis (EEE) virus nor St. Louis encephalitis (SLE) virus was isolated from any of 218 bird sera screened, but serum neutralizing antibodies were found to EEE virus in 4 of 121 (3%) sera and to SLE virus in 2 of 121 (2%) sera from South Carolina. No antibody to either virus was detected in 51 avian sera screened from Georgia. Trypanosomes (probably Trypanosoma avium) were isolated from 1 of 51 (2%) birds from Georgia and from 13 of 97 (13%) birds from South Carolina. Our data suggest that some wild birds may be reservoir hosts for the Lyme disease spirochete and for encephalitis viruses in coastal Georgia and South Carolina and that migrating birds can disperse immature ticks infected with B. burgdorferi.     

Responses of gibbons (Hylobates lar) to their mirror images

BACKGROUND: Hepatitis G virus (HGV) is a blood-borne flavivirus that may cause acute and chronic transfusion-transmitted infections. Patients with complement component 1 (C1) inhibitor (C1-INH) deficiency may acquire blood-borne infections through infusion of plasma concentrates. STUDY DESIGN AND METHODS: Serum samples from 84 patients with C1-INH deficiency (19 who received unmodified C1-INH concentrates, 23 who received steam-heated concentrates, and 42 untreated patients) were tested for HGV RNA and hepatitis C virus (HCV) RNA by a nested polymerase chain reaction (PCR). The samples were also tested for antibodies to the E2 envelope protein of HGV (anti-HGV) and to HCV with enzyme-linked immunosorbent assays. RESULTS: Nine (11%) patients had serum HGV RNA; that is, 7 (17%) of 42 patients previously treated with C1-INH concentrates and 2 of 42 previously untreated patients. HGV RNA was as common in the 19 patients treated with unmodified concentrates as in the 23 given steam-heated concentrates (16 vs. 17%, p = 0.60). Anti-HGV was more common among the recipients of unmodified concentrates than among those given steam-heated concentrates (26 vs. 0%, p = 0.014). HCV RNA was more frequently detected in treated patients than in untreated patients (33 vs. 7%, p = 0.005) and in the 19 recipients of unmodified concentrates than in the 23 treated with steam-heated concentrates (58 vs. 16%, p = 0.003). Only one HGV RNA-seropositive patient had elevated serum aminotransferase activity, compared to 11 with HCV RNA. CONCLUSION: HGV was transmitted by both unmodified and steam-heated concentrates, but it caused persistent viremia in a minority of the cases and was rarely associated with liver disease.     

Experimental malignant catarrhal fever (African form) in white-tailed deer

White-tailed deer (Odocoileus virginianus) were experimentally infected with the African form of malignant catarrhal fever (AMCF) virus by inoculation of whole blood from experimentally infected cattle, from whole blood obtained from a greater kudu (Tragelaphus strepsiceros) and from virus isolated in cell culture. The incubation period from AMCF in experimentally infected deer ranged from 13 to 18 days. Clinical disease was characterized by lacrimation, an elevated body temperature, conjunctivitis and swelling of the external lymph nodes. Histologic lesions were primarily characterized by widespread vasculitis and lymphadenopathy. The organs most severely affected were liver, lymphoid tissue, brain and lungs. Successful recovery and identification of AMCF virus was accomplished from one experimentally infected deer.     

v-representability for noninteracting systems

The Epstein-Barr virus (EBV) induces unlimited growth of B lymphocytes in vitro, a phenomenon known as immortalization. The elucidation of the mechanisms by which EBV de-regulates B-cell proliferation in vitro will permit an understanding of how the virus contributes in vivo to the genesis of Burkitt's lymphoma (BL) and of lymphoproliferations in immunosuppressed patients. At present, no single EBV immortalizing gene has been identified, and the hypothesis has been made that many viral genes cooperate in establishing an autocrine loop of secretion leading to immortalization. Constitutive expression of B-cell surface molecules such as CD21 and CD23, specifically implicated in the control of B-cell proliferation, is indeed induced at the surface of immortalized B lymphocytes. The expression of the viral nuclear antigen 2 (EBNA2) has been shown to be in part responsible for CD21 and CD23 up-regulation, and EBNA2 is suspected to be a transactivator of cellular genes, although this point remains to be demonstrated. The role of EBNA2 gene, independently of other viral genes, has been investigated by transfection into B-lymphoma lines, but conflicting results have been reported. To further investigate its role in the regulation of CD21 and CD23 molecules, we have compared the effects of EBNA2 expression in 2 sets of B-lymphoma lines infected with P3HR1 EBV strain, and/or transfected with EBNA2 gene. We report here that: (i) EBNA2 expression is not a sufficient condition to induce CD21 and CD23 upregulation, EBNA2's effects are highly dependent on the cellular context, and moreover can be modified by infection with P3HR1 virus; (ii) EBNA2 induces activation of CD23 expression in a very particular way, namely, an increased quantity of CD23 steady-state RNA coding for the form A of the protein, which is not detectable at the cell surface but directly secreted.     

Serum hepatitis G virus RNA in patients with chronic viral hepatitis

OBJECTIVES: The hepatitis G virus (HGV) is a newly described flavivirus that affects a high proportion of patients with chronic viral hepatitis: our objective was to determine what role HGV might play in the course of disease. METHODS: We evaluated stored serum samples from 108 patients with chronic hepatitis B and 99 patients with chronic hepatitis C who participated in trials of alpha-interferon or ribavirin for the presence of hepatitis B virus (HBV) DNA and hepatitis C virus (HCV) RNA by branched DNA and for the presence of HGV RNA by polymerase chain reaction (PCR), using primers from the NS5 region of the genome. RESULTS: Initially, 20 (19%) patients with hepatitis B and 11 (11%) with hepatitis C had HGV RNA in their serum. Patients with and without HGV infection were similar with regard to clinical features, laboratory tests, and hepatic histology. HGV RNA levels fell during interferon therapy and became undetectable in those receiving the highest doses; however, HGV RNA levels returned to pretreatment values when therapy was stopped. With ribavirin therapy, HGV RNA levels did not change. Two- to 12-yr follow-up serum samples were available from 17 initially HGV RNA-positive patients, of whom only 10 (59%) were still positive. CONCLUSIONS: HGV infection is common among patients with chronic hepatitis B and C but has little effect on the short-term course of disease or response to therapy. HGV RNA levels are suppressed but not eradicated by alpha-interferon and are unaffected by ribavirin treatment. Spontaneous loss of HGV RNA occurs over time in a proportion of patients.