Epidemiological analysis, serological prevalence and genotypic analysis of foot-and-mouth disease in Nigeria 2008-2009

The epidemiological situation of foot-and-mouth disease virus (FMDV) is uncertain in Nigeria, where the disease is endemic, and the majority of outbreaks are unreported. Control measures for FMD in Nigeria are not being implemented due to the absence of locally produced vaccines and an official ban on vaccine importation. This study summarizes the findings of a 3-year study aimed at quantifying the seroprevalence of FMD, its distribution in susceptible species and the genetic diversity of FMDV isolated from the Plateau State of Nigeria. A 29% FMD prevalence was estimated using 3ABC enzyme-linked immunosorbent assay (3ABC ELISA). Farms with suspected FMD nearby, with contact with wildlife, that used drugs or FMD vaccines or with >100 animals, and animals of large ruminant species and in pastures other than nomadic grazing were significantly (P < 0.05) associated with FMD. Antibodies against five FMDV serotypes, (A, O, SAT1, SAT2 and SAT3) were detected by the virus neutralization test (VNT) at various titres (<100->800) from all tested sera from most parts of the region. This is probably the first report of the presence of FMDV SAT3 in Nigeria. Further studies to investigate the potential probable presence and prevalence of SAT 3 virus in Nigeria are required. Tissue samples collected from clinical animals were positive for FMDV. Virus isolates were sequenced and confirmed as serotype A. All of the isolates showed marked genetic homogeneity with >99% genetic identity in the VP1 region and were most closely related to a previously described virus collected from Cameroon in 2000. This study provides knowledge on the epidemiological situation of FMD in Plateau State, Nigeria, and will probably help to develop effective control and preventive strategies for the disease in Nigeria and other countries in the West African subregion.

Universality of the three-body parameter for Efimov states in ultracold cesium

We report on the observation of triatomic Efimov resonances in an ultracold gas of cesium atoms. Exploiting the wide tunability of interactions resulting from three broad Feshbach resonances in the same spin channel, we measure magnetic-field dependent three-body recombination loss. The positions of the loss resonances yield corresponding values for the three-body parameter, which in universal few-body physics is required to describe three-body phenomena and, in particular, to fix the spectrum of Efimov states. Our observations show a robust universal behavior with a three-body parameter that stays essentially constant.

Pathogenicity and molecular characterization of emerging porcine reproductive and respiratory syndrome virus in Vietnam in 2007

In 2007, Vietnam experienced swine disease outbreaks causing clinical signs similar to the 'porcine high fever disease' that occurred in China during 2006. Analysis of diagnostic samples from the disease outbreaks in Vietnam identified porcine reproductive and respiratory syndrome virus (PRRSV) and porcine circovirus type 2 (PCV-2). Additionally, Escherichia coli and Streptococcus equi subspecies zooepidemicus were cultured from lung and spleen, and Streptococcus suis from one spleen sample. Genetic characterization of the Vietnamese PRRSV isolates revealed that this virus belongs to the North American genotype (type 2) with a high nucleotide identity to the recently reported Chinese strains. Amino acid sequence in the nsp2 region revealed 95.7-99.4% identity to Chinese strain HUN4, 68-69% identity to strain VR-2332 and 58-59% identity to strain MN184. A partial deletion in the nsp2 gene was detected; however, this deletion did not appear to enhance the virus pathogenicity in the inoculated pigs. Animal inoculation studies were conducted to determine the pathogenicity of PRRSV and to identify other possible agents present in the original specimens. Pigs inoculated with PRRSV alone and their contacts showed persistent fever, and two of five pigs developed cough, neurological signs and swollen joints. Necropsy examination showed mild to moderate bronchopneumonia, enlarged lymph nodes, fibrinous pericarditis and polyarthritis. PRRSV was re-isolated from blood and tissues of the inoculated and contact pigs. Pigs inoculated with lung and spleen tissue homogenates from sick pigs from Vietnam developed high fever, septicaemia, and died acutely within 72 h, while their contact pigs showed no clinical signs throughout the experiment. Streptococcus equi subspecies zooepidemicus was cultured, and PRRSV was re-isolated only from the inoculated pigs. Results suggest that the cause of the swine deaths in Vietnam is a multifactorial syndrome with PRRSV as a major factor.

Magnetically controlled exchange process in an ultracold atom-dimer mixture

We report on the observation of an elementary exchange process in an optically trapped ultracold sample of atoms and Feshbach molecules. We can magnetically control the energetic nature of the process and tune it from endoergic to exoergic, enabling the observation of a pronounced threshold behavior. In contrast to relaxation to more deeply bound molecular states, the exchange process does not lead to trap loss. We find excellent agreement between our experimental observations and calculations based on the solutions of three-body Schrödinger equation in the adiabatic hyperspherical representation. The high efficiency of the exchange process is explained by the halo character of both the initial and final molecular states.

Evidence for universal four-body states tied to an Efimov trimer

We report on the measurement of four-body recombination rate coefficients in an atomic gas. Our results obtained with an ultracold sample of cesium atoms at negative scattering lengths show a resonant enhancement of losses and provide strong evidence for the existence of a pair of four-body states, which is strictly connected to Efimov trimers via universal relations. Our findings confirm recent theoretical predictions and demonstrate the enrichment of the Efimov scenario when a fourth particle is added to the generic three-body problem.

Collisions between tunable halo dimers: exploring an elementary four-body process with identical bosons

We study inelastic collisions in a pure, trapped sample of Feshbach molecules made of bosonic cesium atoms in the quantum halo regime. We measure the relaxation rate coefficient for decay to lower-lying molecular states and study the dependence on scattering length and temperature. We identify a pronounced loss minimum with varying scattering length along with a further suppression of loss with decreasing temperature. Our observations provide insight into the physics of a few-body quantum system that consists of four identical bosons at large values of the two-body scattering length.

Viral haemorrhagic disease of rabbits in Mexico: epidemiology and viral characterization

A fatal disease of rabbits was first reported in the People's Republic of China in 1984. Since 1986, the disease has been reported in most countries of Europe and in the Republic of Korea. In 1989 a similar disease, presumably linked to the importation of rabbit meat from the People's Republic of China, spread rapidly through ten states in Mexico; it was eradicated during the same year by "stamping-out" measures. In Mexico, as was the case in other outbreaks, morbidity and mortality reached 80-90% with few clinical signs. In pathogenesis studies, the primary sites of replication were in the small intestinal crypt and villous epithelium, hepatocytes and splenic lymphocytes. Many organs, including the lung and kidney, contained acutely infarcted tissue and haemorrhages resulting from a terminal disseminated intravascular coagulopathy. The disease and the characteristics of the virus isolated in Mexico are similar to isolates from Europe and the Republic of Korea. The comparative morphologic, from Europe and the Republic of Korea. The comparative morphologic, immunologic, and in situ nucleic acid hybridization evidence for a parvovirus aetiology are summarized.

Bioassay for specific DNA sequences using a non-radioactive probe

A novel method for detecting specific DNA sequences is described. The method uses a non-radioactive DNA probe, called a probe-vector, that can transform competent Escherichia coli cells at high efficiency only when it has hybridized to a specific DNA target, thus forming a circular, double-stranded, plasmid-like molecule. The probe-vector carries a plasmid origin of replication and a gene that confers antibiotic resistance on transformed E. coli. The output of the assay--colored bacterial colonies on an agar plate--is quantitative and proportional over a wide range of target concentrations. The utility of the probe-vector method for detecting hepatitis B virus (HBV) DNA in human serum is demonstrated. The assay can detect as little as 0.1 pg HBV DNA. The presence of an internal standard monitors DNA recovery and E. coli transformation efficiency for each sample. The assay has the potential to simultaneously measure the DNA of two or more pathogens within the same clinical sample.

Detection of HBV-DNA by in situ hybridization using a biotin-labeled probe

A biotin-labeled DNA probe specific for hepatitis B virus (HBV) nucleotide sequences was hybridized in situ to liver tissue of 20 patients; 16 were chronic carriers of hepatitis B surface antigen (HBsAg) and 4 had no markers of HBV infection. HBV-DNA was also analyzed in the serum and the liver of these patients by spot and Southern blot hybridization, respectively. Liver specimens from six carriers were positive for HBV-DNA both by in situ and Southern blot hybridization; ten carriers were negative by in situ hybridization, and two of these were positive by Southern blot technique. The staining was granular, mainly cytoplasmic, limited to liver specimens containing replicative forms of HBV-DNA, and associated with detection of HBcAg in hepatocytes by immunofluorescence. The sensitivity of this technique was not sufficient to detect few copies of integrated HBV-DNA. The hybridization procedure was specific, as results were constantly negative in liver specimens of patients without markers of HBV infection, and no reaction was observed using DNA probes lacking HBV-DNA sequences. Detection of HBV-DNA by in situ hybridization, using a biotinylated probe, is a rapid, reproducible, and specific histochemical method. Currently available biotinylated probes are advantageous when absolute sensitivity is not the limiting factor, and they also facilitate studies of the cellular and subcellular distribution of HBV nucleic acids.

Hepatitis B virus DNA (HBV-DNA) in anti-HBe positive sera

HBV-DNA measured by the spot hybridization technique, was found in the sera of 28 of 106 (26.4%) anti-HBe positive carriers of HBsAg. Dane particle-associated HBeAg, HBcAg and HBV-specific DNA-polymerase activity were found in the sera of nine (8.5%), five (4.7%) and two (1.9%) of these patients, respectively. All carriers with serum HBV-DNA had chronic liver disease and 18 had intrahepatic delta-Ag and serum anti-delta at titers higher than 1/5000. Intrahepatic HBcAg was detected in the nuclei of 90% of delta negative individuals; 50% of them also had cytoplasmic fluorescence. Only two of the 18 patients with intrahepatic delta-Ag (11%) had HBcAg in the liver. Viral nucleic acid was not found in the sera of 15 other patients with chronic hepatitis, seven of whom had intrahepatic delta-Ag. Serum HBV-DNA was also negative in the remaining 63 symptomless carriers of HBsAg lacking markers of delta infection. Interestingly, although DNA-polymerase negative, some sera gave autoradiographic spots of high optical density. HBV-DNA was detected in them at concentrations typical of sera which are usually both DNA-polymerase and HBeAg positive. Detection of HBV-DNA in serum represents the most direct and sensitive in vitro assay for assessing HBV infectivity and characterizes HBsAg carriers with HBV-related liver damage and ongoing HBV replication independently from the state of HBeAg/anti-HBe system. In the Mediterranean area, the majority of anti-HBe positive carriers with serum HBV-DNA have chronic liver disease and delta infection.

Use of T4 DNA polymerase replacement synthesis for specific labeling of plasmid-cloned inserts

A strategy employing T4 DNA polymerase replacement synthesis is described whereby only the insert portion of recombinant plasmids are radioisotopically labeled. Prior purification of the inserted DNA is not required. The recombinant plasmid is first digested with one or more restriction endonucleases selected to cleave the vector segment into fragments at least 30% shorter than the insert DNA segment. This mixture of fragments is then digested by the T4 DNA polymerase-associated 3' exonuclease in the absence of deoxynucleoside triphosphates (dNTPs) for a length of time which allows complete degradation of all fragments shorter than the insert. The remaining insert DNA, which is now partially single-stranded, is then resynthesized by addition of dNTPs, one or more of which is labeled. The resulting DNA is full length, double-stranded, and unnicked. The strategy is widely applicable, and reliably and reproducibly yields DNA of high specific activity. We have used this method to label more than 15 cloned inserts ranging in size from 3.2 to 25 kilobases.

Unrelatedness of factor VIII-derived non-A/non-B hepatitis and hepatitis B virus

A DNA hybridization assay was used to detect hepatitis B virus (HBV)-specific DNA sequences in extracted sera obtained from chimpanzees infected with HBV, hepatitis A virus (HAV), and a factor VIII-derived non-A/non-B (NANB) agent. The results did not reveal any HBV-DNA homology with sera obtained from animals infected with HAV or factor VIII-derived NANB. Sera obtained from two HBV-infected chimpanzees demonstrated that HBV-specific DNA could be detected during the acute phase of the disease. In addition, an HBV-specific DNA-dependent DNA polymerase assay did not demonstrate any statistically significant activity in 12 of 12 NANB acute-phase specimens or in 6 of 6 NANB chronic-phase specimens. These results suggest that the factor VIII-derived NANB agent is unrelated to HBV.

DNA-protein interactions in the Drosophila melanogaster mitochondrial genome as deduced from trimethylpsoralen crosslinking patterns

The location of proteins on the mitochondrial DNA (mtDNA) of Drosophila melanogaster was investigated by trimethylpsoralen photoreaction of embryos disrupted by gentle homogenization. After photoreaction, the mtDNA was isolated and the pattern of DNA crosslinking was determined by electron microscopy of the DNA under totally denaturing conditions. In contrast to nuclear DNA, which showed periodic crosslinks indicative of a nucleosome structure, most of each mtDNA molecule exhibited uniformly heavy crosslinking. A 10% region of the mtDNA was, however, protected from psoralen crosslinking in a distinctive manner: five uncrosslinked segments were closely clustered in the mtDNA. Four were 394 +/- 13 (SD) base pairs in size, while the fifth measured about 200 base pairs. These protected segments mapped within the A+T-rich region of the mtDNA, extending from the end of the A+T-rich region near the Bg1 II cleavage site to the center of the A+T-rich region. Protection of this part of the mtDNA from crosslinking was interpreted to be the result of association with proteins in the mitochondrion because mtDNA that was deproteinized before the photoreaction was uniformly crosslinked over its entire length. The origin of replication of the mtDNA is also located at the center of the A+T-rich region, which suggests that the protection from the psoralen photoreaction may be due to proteins involved in membrane attachment or replication.