Use of serology and real time PCR to control an outbreak of bovine brucellosis at a dairy cattle farm in the Nile Delta region,Egypt

Background

Bovine brucellosis remains one of the most prevalent zoonotic infections affecting dairy cattle in developing countries where the applied control programs often fail. We analyzed the epidemiologic pattern of bovine brucellosis in a dairy cattle herd that showed several cases of abortions after regular vaccination with RB51 (B. abortus vaccine). In 2013 thirty dairy cows, from a Holstein-Friesian dairy herd with a population of 600 cattle, aborted five months post vaccination by a regular RB51 vaccine. Blood samples were drawn from milking cows and growing heifers, as well as heifers and cows pregnant up to 6 months. These samples were collected in June 2013 (n?=?257) and May 2014 (n?=?263) and were tested by real time (rt)-PCR as well as serological tests, in particular Rose Bengal Test (RBT), Enzyme-Linked Immunosorbent Assays (ELISA) and Fluorescence Polarization Assay. Tissue specimens were also collected from an aborted fetus and cultured. Isolates were subjected to bacteriological typing tests at the genus and species levels.

Results

Five months post vaccination with RB51 vaccine, Brucella (B.) DNA was detected in blood samples of cows by rt-PCR. The serological tests also revealed the spread of Brucella field strains within the herd in 2013. Four Brucella isolates were recovered from specimens collected from the aborted fetus. These isolates were typed as follows: one B. abortus RB51 vaccine strain and three isolates of B. abortus field strain. The seropositive cows with positive rt-PCR might indicate an infection by the Brucella field strain; while the positive rt-PCR results from seronegative animals may either be due to circulating RB51 vaccine DNA in vaccinated animals or to circulating field strain in infected animals before seroconversion.

Conclusion

The results herein suggest that PCR can be a good supplementary tool in an outbreak situation, if an assay is available that can differentiate vaccine and field strains with a high analytical sensitivity. We recommend using RBT and ELISA in parallel in outbreak situations, to identify as many infected animals as possible during the initial screenings. This test procedure should be repeated for at least three successive negative tests, with one month interval.

     

Weaning of juvenile pikeperch, Stizostedion lucioperca L., and perch, Perca fluviatilis L., to formulated feed

Weaning success of pond‐cultured pikeperch and wild‐caught perch (mean length 51 and 48 mm respectively) was evaluated using different weaning techniques and different formulated feeds. Juveniles that were fed formulated feed grew as well as or better than juveniles that were weaned successively using zooplankton or yolk. Four different formulated feeds (agglomerated marine larvae feed, marine larvae feed, trout feed and a semi‐moist feed) were evaluated regarding specific growth rate (SGR), condition factor and a subjective stomach fullness estimate. The agglomerated marine larvae feed gave significantly better weaning performance than the other feeds regarding all parameters (SGR = 7.3% day^?1 and 3.4% day^?1 for pikeperch and perch respectively).     

Selection experiments with salmon: IV. Growth of Atlantic salmon during two years in the sea

Brood stock of Atlantic salmon were sampled from 37 rivers or riversystems (strains) for three consecutive years. Each strain was represented by several full- and half-sib families. During the freshwater period each full-sib family was reared separately and each group was given as equal environmental conditions as possible. Fingerlings large enough to become 1-year-old smolt were freeze-branded and smolts from the different strains were sampled and transported to five salmon farms along the Norwegian coast. This paper deals with body weight and length of Atlantic salmon after a growth period of 2 years in the sea.Significant differences between strains were found for all three year classes. The interaction farm × strain was significant but accounted for only a small part of the total variation. It is concluded that genotype × environment interaction can be ignored when planning a selection programme for Altantic salmon for Norwegian farming conditions. A significant interaction sire × dam was found for the 1972 year-class, implying the presence of non-additive genetic variation. The heritabilities for body weight and length estimated from sire components (year-class 1973 and 1974) were quite high: 0.31 and 0.28, respectively. Genetic correlations between body weight and length were close to unity. The heritabilities for condition factor ($\text{K=}\text{weight in g}\text{(length in cm)}{}^3\text{·100}$ were small and none of the sire components were significant. It is concluded that the combination of weight and length used in calculating the K-factor has minor genetic basis.Genetic variation in body weight of Atlantic salmon is high, and about three times as high as for body length.     

Heart and skeletal muscle inflammation in Atlantic salmon, Salmo salar L: a new infectious disease

Heart and skeletal muscle inflammation (HSMI) is a disease syndrome of unknown aetiology first observed in farmed Atlantic salmon, Salmo salar, in 1999. In the present study we have demonstrated for the first time that HSMI is an infectious disease. It was induced in Atlantic salmon post-smolts after injection with tissue homogenate from farmed Atlantic salmon previously diagnosed with HSMI. The lesions were also induced in cohabitating salmon given a corresponding injection without tissue homogenate. Six weeks post-challenge the fish that had been injected with tissue homogenate developed a serious epicarditis and myocarditis with mononuclear cell infiltrations in compact and spongy layers of the heart. Similar lesions were found in cohabitants after 10 weeks. The lesions were consistent with samples from field outbreaks of HSMI. No lesions were found in control fish. A viral aetiology is strongly suggested, as no difference in disease induction between an inoculum containing antibiotics and a non-treated inoculum was found. Further investigations are required in order to make conclusions regarding the cause and pathogenesis of HSMI.     

Nitrogen isotope analysis of free glycine in soil using isotope dilution mass spectrometry

To enable the estimation of production and consumption rates of free glycine in soils through ¹⁵N isotope dilution experiments, an isotope dilution mass spectrometric method was developed. The method, which enabled high precision N isotope ratio determination of glycine in soil extracts at δ¹⁵N levels up to 4000‰ and concentrations from approximately 2 μM, is based on the following steps: (i) addition of glycine spike to the soil extract, (ii) removal of humic substances and pre-concentration of glycine using solid phase extraction, (iii) derivatization of amino acids, (iv) separation of the derivatives using gas chromatography (GC), (v) their combustion to yield sample N₂ gas, and (vi) finally the use of N isotope ratio mass spectrometry (IRMS). Judging by uncertainty budget calculations, the precision obtained (SD=0.01-0.06 at% ¹⁵N) is sufficient for detecting differences in N isotopic ratios obtained in ¹⁵N isotope dilution experiments.     

Phosphatase activity, microbial phosphorus, and fine root growth in forest soils in the Sierra de Gata, western central Spain

Acid phosphatase activity (APA), labile P fractions and fine root growth were studied in an oak (Quercus pyrenaica Willd.) forest in the Sierra de Gata, in western central Spain. Soils in the region are acid and rich in organic matter, with low levels of extractable inorganic P but with a high proportion of organic P. In such soils, the activity of phosphatase enzymes is likely to be important for the control of P mineralization and P cycling and, consequently, can affect the availability of P for plant uptake. The biomass of fine roots was about 25-fold that of leaf litter, demonstrating a high allocation of C resources to the root system in order to compensate for a low availability of soil nutrients. The study compared plots fertilized with triple superphosphate (100 kg P ha^-1) to control (unfertilized) plots. Fertilizer application had no significant effect on APA and fine root density; however, there were significant differences in available and microbial P. Spatial and seasonal variations in the APA were related to plant root density and biotic demand. Seasonal differences in the APA may also be the consequence of changes in the amount of hydrolysable organic substrates at different times of the year.     

Monoclonal antibody-mediated tumor regression by induction of apoptosis

To characterize cell surface molecules involved in control of growth of malignant lymphocytes, monoclonal antibodies were raised against the human B lymphoblast cell line SKW6.4. One monoclonal antibody, anti-APO-1, reacted with a 52-kilodalton antigen (APO-1) on a set of activated human lymphocytes, on malignant human lymphocyte lines, and on some patient-derived leukemic cells. Nanogram quantities of anti-APO-1 completely blocked proliferation of cells bearing APO-1 in vitro in a manner characteristic of a process called programmed cell death or apoptosis. Cell death was preceded by changes in cell morphology and fragmentation of DNA. This process was distinct from antibody- and complement-dependent cell lysis and was mediated by the antibody alone. A single intravenous injection of anti-APO-1 into nu/nu mice carrying a xenotransplant of a human B cell tumor induced regression of this tumor within a few days. Histological thin sections of the regressing tumor showed that anti-APO-1 was able to induce apoptosis in vivo. Thus, induction of apoptosis as a consequence of a signal mediated through cell surface molecules like APO-1 may be a useful therapeutic approach in treatment of malignancy.