Origin of the West Nile virus responsible for an outbreak of encephalitis in the northeastern United States.

In late summer 1999, an outbreak of human encephalitis occurred in the northeastern United States that was concurrent with extensive mortality in crows (Corvus species) as well as the deaths of several exotic birds at a zoological park in the same area. Complete genome sequencing of a flavivirus isolated from the brain of a dead Chilean flamingo (Phoenicopterus chilensis), together with partial sequence analysis of envelope glycoprotein (E-glycoprotein) genes amplified from several other species including mosquitoes and two fatal human cases, revealed that West Nile (WN) virus circulated in natural transmission cycles and was responsible for the human disease. Antigenic mapping with E-glycoprotein-specific monoclonal antibodies and E-glycoprotein phylogenetic analysis confirmed these viruses as WN. This North American WN virus was most closely related to a WN virus isolated from a dead goose in Israel in 1998.

Comparative bioavailability of two sertraline tablet formulations after single-dose administration in healthy Thai volunteers.

OBJECTIVE: To compare the bioavailability of two sertraline tablet (50 mg) formulations (Serlift from Ranbaxy Laboratories Ltd., Gurgaon Haryana, India, as a test formulation and Zoloft from Pfizer Australia Pty Ltd., West Ryde, New South Wales, Australia, as a reference formulation) in 24 healthy Thai male volunteers under fasting condition. MATERIALS AND METHODS: A randomized, 2-treatment, 2-period, 2-sequence, single-dose, crossover study with a washout period of 3 weeks, was conducted in 24 healthy Thai male volunteers. Blood samples were collected at 0, 1, 2, 3, 4, 5, 6, 7, 8, 10, 12, 24, 36, 48, 72, 96 and 120 hours following drug administration. Plasma concentrations of sertraline were determined using validated LC-MS/MS method. Noncompartmental pharmacokinetics and statistical analyses were performed using SAS software for Windows, release 9.1 (SAS Institute Inc., Cary, NC, USA). RESULTS: The ratio of least square means and the 90% confidence intervals (CI) of the log-transformed data were 0.9950 (0.9111-1.0866) for Cmax, 1.0153 (0.9576-1.0764) for AUC(0-t) and 1.0110 (0.9510-1.0747) for AUC(0-infinity). In addition, the median tmax values for the test and reference formulations were similar (5.00 h). The 90% CI for Cmax, AUC(0-t) and AUC(0-infinity) were within the 0.8-1.25 interval of the US-FDA. CONCLUSIONS: The test formulation (Serlift, Ranbaxy Laboratories Ltd., Gurgaon, Haryana, India) is bioequivalent to the reference formulation (Zoloft, Pfizer Australia Pty Ltd., West Ryde, New South Wales, Australia) both in terms of rate and extent of absorption after single-dose administration under fasting condition.

Rapid diagnosis of avian influenza (AI) and assessment of pathogenicity of avian H5 and H7 subtypes by molecular methods.

Avian influenza (AI) is a highly contagious viral disease of poultry that is found worldwide. There are two forms of AI: a mild form called low pathogenicity avian influenza (LPAI), and a severe form called highly pathogenic avian influenza (HPAI). HPAI is associated with the H5 and H7 subtypes of AI virus (AIV) and is subject to Federal control and International reporting. A real-time reverse transcription-polymerase chain reaction (rRT-PCR) assay has been developed and validated that can help in the early detection of AI outbreaks. The rRT-PCR assay can also be used to identify infections caused by H5 and H7 subtypes of AIV New isolates of AIV must be characterized as LPAI or HPAI for reporting and control purposes. The criteria for classification of an AI virus as HPAI are defined by the World Organization for Animal Health (OIE); the definition includes a virulence and a molecular criterion. The virulence requirement for HPAI is defined as an AIV killing 75% or more of eight inoculated chickens within 10 days. The molecular criterion is the presence of multiple dibasic amino acids at the proteolytic cleavage site of the haemagglutinin (H) protein. All HPAI viruses isolated before 2002 fulfilled both the virulence and molecular criteria. Consequently, nucleotide sequencing of the H gene and deduction of the amino acid motif at the H cleavage site has been successfully used to assess the virulence of H5 and H7 AIVs rapidly. Since 2002, however, there have been three outbreaks of HPAI where the viruses responsible for the outbreaks have either fulfilled the virulence criterion or the molecular criterion, but not both.

Ecology and epidemiology of avian influenza in North and South America.

Wild waterfowl and shorebirds are known to be the natural reservoir for influenza A viruses. Surveillance studies in waterfowl and shorebirds in North America show that influenza A viruses are repeatedly recovered from these birds. However, the virus recovery is influenced by geography, season, age and species of birds. In addition to the natural reservoir, the live-bird marketing system (LBMS) in certain regions of the United States has been recognized as a man-made reservoir of influenza viruses and has been linked to several outbreaks of low pathogenicity avian influenza (LPAI) in poultry. Outbreaks of LPAI in commercial poultry is attributed to movement of infected birds, dirty or improperly cleaned crates, and contaminated vehicles from the LBMS to poultry farms. However, in the majority of outbreaks in poultry, the source of infection is suspected to be wild aquatic birds or the source is unknown. Since 2002, three outbreaks of highly pathogenic avian influenza (HPAI) have occurred in the Americas; one each in Chile (H7N3), United States (H5N2), and Canada (H7N3). In each of these outbreaks, a precursor virus of low pathogenicity mutated to become highly pathogenic after circulating in poultry. The HPAI viruses recovered from the three outbreaks had unique molecular and phenotypic characteristics that do not conform to other known HPAI viruses. These findings emphasize the need for monitoring wild and domestic bird species for presence of influenza A viruses.

Tumor-specific transplantation antigen(s) of bovine adenoviruses.

Protection against bovine adenovirus type 3-induced primary or transplantable tumors was studied in hamsters immunized with bovine adenoviruses, human adenovirus type 12 (A-12), simian adenovirus type 7 (SA7), or chicken-embryo-lethal-orphan (CELO) virus. Newborn hamsters inoculated with 2.3 times 10-5 plaqueforming units of bovine adenovirus type 3 were given injections of bovine serotypes 1, 2, or 3 during the latent period of tumor development. No hamsters immunized with type 3 and only 47% of those inoculated with types 1 or 2 developed tumors as compared to a control incidence of 90%. Primary tumors were not prevented when hamsters inoculated at birth with bovine adenovirus type 3 were immunized during the latent period with A-12, SA7, or CELO, even though 10-100 times more infectious virus was used. When adult hamsters were given injections of the bovine adenoviruses on 3 successive weeks and then challenged with graded doses of tumor cells, the three serotypes produced a 20-fold to 200-fold increase in the 50% tumor-producing dose of tumor cells. These studies indicate that bovine adenoviruses types 1, 2, and 3 induce cross-reactive transplantation antigens which, however, do not cross-react with those induced by oncogenic adenoviruses of either avian, simian, or human origin.

Humoral and cell-mediated immune responses in chickens with infectious bursal disease.

Primary and secondary immune responses to Newcastle disease virus (NDV) was evaluated in chickens infected with infectious bursal disease virus (IBDV) at one and 28 days of age. The geometric mean primary hemagglutination-inhibition antibody titers (GMT) of chickens infected with IBDV at one day of age was significantly lower (P less than or equal to 0.01) than those infected at 28 days of age. Infection with IBDV had no influence on secondary immune response to NDV. The effect of IBDV infection at one day of age on the cell-mediated immunity of chickens was evaluated by skin allograft acceptance or survival time. There was no significant difference between the percentage of grafts accepted in IBDV infected and noninfected control chickens. However, the mean graft survival time in the IBDV infected chickens was significantly longer (P less than or equal to 0.05) than those in the control group. This suggested a suppression of cell-mediated immunity due to IBDV infection.

PCR-based detection of an emerging avian pneumovirus in US turkey flocks.

Avian pneumovirus (APV) or turkey rhinotracheitis virus (TRTV) is an important respiratory pathogen of domesticated poultry in many countries in Europe, Africa, and Asia. Until recently, the United States was considered free of APV. In late 1996, an atypical upper respiratory tract infection appeared in turkey flocks in Colorado and shortly thereafter in turkey flocks in Minnesota. An avian pneumovirus (APV-US) that was serologically distinct from the previously described TRTV was isolated as the primary cause of the new syndrome. The nucleotide sequence of a fragment of the APV-US fusion gene was determined and used to develop a polymerase chain reaction-based assay that specifically detects APV-US viral nucleic acid sequences in RNA extracts of tracheal swabs and turbinate homogenates. The assay is highly sensitive in that it can detect <0.01 TCID50 of APV. The availability of this assay enables the rapid and accurate determination of APV-US in infected poultry flocks.

A modified enzyme-linked immunosorbent assay for the detection of avian pneumovirus antibodies.

Avian pneumovirus (APV) infection of turkeys in Minnesota was first confirmed in March 1997. Serum samples (n = 5,194) from 539 submissions to Minnesota Veterinary Diagnostic Laboratory were tested by a modified enzyme-linked immunosorbent assay (ELISA). Of these, 2,528 (48.7%) samples from 269 submissions were positive and 2,666 (51.3%) samples from 270 submissions were negative for APV antibodies. Most positive samples were from Kandiyohi, Stearns, Morrison, and Meeker counties in Minnesota. In addition, 10 samples from South Dakota were positive. The sensitivity and specificity of the ELISA test with anti-chicken and anti-turkey conjugates were compared by testing field and experimental sera. The ELISA test with anti-turkey conjugate was more sensitive than that with anti-chicken conjugate. The ELISA tests with antigens prepared with APV strains isolated from Colorado and Minnesota were also compared. No difference was detectable. Currently, the Minnesota Veterinary Diagnostic Laboratory uses an antigen prepared from the Colorado isolate of APV and a goat anti-turkey conjugate in the ELISA test.

Diversity of pilus subunits of Escherichia coli isolated from avian species.

Pili from 69 avian isolates of Escherichia coli from six diagnostic laboratories in the United States were characterized. Three new pilus types were identified in addition to the three types previously described. A majority of the E. coli isolates (53.6%) examined expressed the classical type 1 pili.

Differentiation of pathogenic and nonpathogenic Escherichia coli isolated from poultry.

Twenty-one isolates of Escherichia coli recovered from chickens and turkeys were evaluated for pathogenicity in 1-week-old chicks. Fifteen produced coli-septicemia (pathogenic) and six were innocuous (nonpathogenic). Both pathogenic and nonpathogenic E. coli were tested for their ability to selectively absorb Congo red (CR) dye incorporated into agar medium. Eight of 15 pathogenic E. coli (somatic antigen types O1, O78, O11, O88, and OX9) absorbed the dye and produced red colonies (CR+) between 48 to 72 hours of incubation. All serotypes of E. coli with homologous somatic antigen O78 were CR+, while those of O2 antigen were CR- (white colonies). Five of six nonpathogenic E. coli also were CR+. In contrast to pathogenic E. coli, however, nonpathogenic isolates absorbed CR early, between 18 to 24 hours of incubation. Although CR dye binding did not correlate well with pathogenicity, it may be an identifiable property of some serotypes of E. coli.

Biological and immunological characterization of pili of Escherichia coli serotypes O1, O2, and O78 pathogenic to poultry.

Pili of Escherichia coli serotypes O1, O2, and O78 pathogenic to poultry were isolated and purified by sucrose-density-gradient centrifugation. Each serotype expressed only one type of pilus. The pili of the three serotypes had similar densities and were morphologically similar by electron microscopy. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis, however, showed that they were slightly different in subunit molecular mass. Slide agglutination, immunodiffusion, and immunoblot tests were used to test for antigenic relationships between these pili and reference pili. Pili of serotype O78 were type 1, but pili of serotypes O1 and O2 were not, as once believed. However, pili of serotype O2 reacted positively with anti-type 1 serum in immunoblot assay, suggesting the presence of some common antigenic epitopes among these pili.

An outbreak of erysipelas in chukars.

A peracute severe outbreak of erysipelas in chukars (Alectoris chukar) caused 55% mortality. Pheasants and quails on the same premises were not affected. Possible sources of infection and pathogenesis are discussed.

Adhesin-receptor interactions mediating the attachment of pathogenic Escherichia coli to chicken tracheal epithelium.

Specific adherence of pathogenic Escherichia coli (serotypes O1, O2, and O78) to chicken tracheal epithelium was investigated using adherence-inhibition procedures. The role of pilus as adhesin was studied by blocking the pilus with antipilus antibodies. The nature of the host cell receptor was determined by blocking bacterial adhesion with specific carbohydrates or lectins and destroying the receptor with sodium metaperiodate. Antipilus antibodies to all three serotypes significantly (P less than or equal to 0.05) inhibited their adherence. Sodium metaperiodate considerably inhibited the adhesion of all three serotypes, indicating a role for monosaccharides in the host cell receptor. D-Mannose and its derivative methyl-alpha-D-mannopyranoside inhibited the adhesion of serotypes O1 and O78, indicating a role for these sugars in the host cell receptor; this was further supported by the inhibition of both serotypes after treatment of tracheal epithelium with concanavalin A. None of the sugars or lectins used inhibited adhesion of serotype O2.

Immunogenicity of an Escherichia coli (serotype O1) pili vaccine in chickens.

Immunogenicity of an oil-emulsified Escherichia coli (serotype O1) pili vaccine was evaluated in chickens. Chickens were vaccinated with 116 micrograms or 29 micrograms of pili protein and challenged with the homologous E. coli via the posterior thoracic air sac. Unvaccinated chickens were challenged to serve as positive controls or left unchallenged to serve as negative controls. Vaccinated chickens were protected against challenge because they suffered low or no mortality; had mild gross lesions in air sacs, pericardial sacs, and livers, and the scored values were significantly (P less than or equal to 0.05) lower than those in the positive controls; and eliminated E. coli from tissues more efficiently than the positive controls.

An outbreak of erysipelas in Coturnix quails.

A severe outbreak of erysipelas causing high mortality was observed in Coturnix breeder quails. Possible source(s) of erysipelothrix infection in the flock and subsequent infections due to Pasteurella multocida, Salmonella typhimurium, and Staphylococcus aureus are discussed.

Outbreaks of fowl cholera in quail.

Acute fowl cholera causing high mortality was diagnosed in three flocks of quail, one involving pharaoh quail (Coturnix coturnix) and two involving bobwhite quail (Colinus virginianus). The causative organism, Pasteurella multocida, was identified as type 3.

Dermal necrosis caused by Pasteurella multocida infection in turkeys.

Severe dermal necrosis caused by Pasteurella multocida Serotype 1 was diagnosed in three dressed turkey carcasses and two live turkeys from a commercial flock. The dressed carcasses were among several condemned at a processing plant. The isolate, P. multocida Serotype 1, produced progressive dermal necrosis when experimentally inoculated into injured skin of turkeys. The organism was reisolated from the dermal lesions. The turkey houses were found to be infested by mice; the skin injury and infection with P. multocida probably originated from mouse bites.

Pacheco's disease in psittacine birds.

Pacheco's disease, caused by a herpesvirus, was diagnosed in 20 groups of 47 psittacine birds received for necropsy. A tentative diagnosis, based on history and gross lesions, was confirmed by one or more of the following observations: Cowdry type A inclusions in the hepatocytes and cells of other affected tissues, pathogenicity of tissue suspensions for chicken embryos, cytopathic effects of herpesvirus in monolayers of chicken embryo fibroblasts, and demonstration of herpesvirus in cell-culture fluid by electron microscopy.

Hemorrhagic disease in canaries (Serinus canarius).

Two aviaries were diagnosed as harboring an infectious and fatal disease of canaries (Serinus canarius) characterized by acute hepatocellular necrosis and associated with megaloschizonts of a protozoan parasite and extravasation of blood into the thoracoabdominal cavity.

Immunogenicity of an Escherichia coli multivalent pilus vaccine in chickens.

Immunogenicity of an oil-emulsified Escherichia coli multivalent pilus vaccine was evaluated in 4-week-old chickens. The vaccine contained 180 micrograms of pilus protein from each of serotypes O1 and O78 and 170 micrograms of pilus protein from serotype O2. Chickens were vaccinated twice subcutaneously at 4 and 6 weeks old and challenged via the posterior thoracic air sac with E. coli serotype O1, O2, or O78 2 weeks after the last vaccination. Unvaccinated challenged chickens suffered 8% to 26% mortality; no vaccinated chickens died. Vaccinated chickens had very mild gross lesions in the air sacs, livers, and pericardial sacs and eliminated E. coli more efficiently than the unvaccinated challenged chickens. The results showed that a multivalent pilus vaccine protects chickens against active respiratory infection.