Evaluation of a commercially available ELISA kit for detection of antibodies to Anaplasma marginale and Anaplasma centrale in cattle in Australia and Zimbabwe

A newly available competitive inhibition ELISA kit for the serological diagnosis of anaplasmosis was evaluated in Australia and Zimbabwe. In Australia the performance of the test was compared with the card agglutination test (CAT).The assay was evaluated using negative sera collected from Anaplasma-free herds, positive sera from experimentally infected cattle and sera from Anaplasma marginale-endemic herds. The sensitivity and specificity of the ELISA in Australia were 100 % and 83,3 %, respectively, and the sensitivity and specificity of the CAT were both 100%. The agreement between the ELISA and CAT in the sera from endemic herds was 86,4 % (kappa = 0,718). The specificity of the ELISA in Zimbabwe was 100%. No meaningful estimate of sensitivity was possible in Zimbabwe because few known positive sera were available for testing, but all eight known positive sera that were available were clearly positive. We conclude that the ELISA is a useful alternative to the CAT for epidemiological studies.The ELISA kits have advantages over the CAT in that the ELISA is more robust and reagents are better standardized, but the kits are expensive.     

An Assessment of Hatchery Cohort Growth Rates of South African Abalone,Haliotis midae,Across Four Commercial Environments

The abalone, Haliotis midae (commonly referred to as “perlemoen”), is an important aquaculture species in South Africa, accounting for the highest percentage of total aquaculture production revenue. The industry largely makes use of wild, undomesticated broodstock and thus a consortium of top producers was formed to develop a genetic improvement program to increase efficiency and sustainability of the industry. As such, the current study aimed to evaluate growth trait performance (wet weight and shell length) of four hatchery‐derived cohorts of South African abalone, across four differing production environments. No significant cohort‐by‐location effects were found for weight and length traits; however, differences were detected between respective cohorts and locations. It is concluded that a single synthetic population comprised of all hatchery cohorts under a single breeding goal is suitable for production at all test locations. Furthermore, advances in artificial reproductive technologies, genetic markers, and individual identification hold promise for genetic improvement of the species.     

Dissipation of the defoliant tribufos in cotton-producing soils

Soil dissipation of the cotton defoliant tribufos was measured in laboratory incubations and on 0.2-ha research plots. Computed 50% dissipation time (DT(50)) using nonlinear and linear kinetic models ranged from 1 to 19 days. Data indicated that exchangeable soil aluminum inhibited tribufos-degrading soil organisms. Nevertheless, measured DT(50) values were 40 to 700 times less than the aerobic soil half-life (t(1/2)) values used in recent tribufos risk assessments. DT(50) values suggest that risk estimates were overstated. However, edge-of-field runoff concentrations measured on research plots exceeded invertebrate LOECs, thus some aquatic risk is indicated. Field data also suggested that volatilization may be a significant soil dissipation pathway. From this result, we conclude that volatilization should be included in simulation models used for pesticide registration. This will likely improve the accuracy of model outputs for products such as tribufos. Potential volatilization losses indicate a need to evaluate the atmospheric behavior of tribufos.     

Nitrogen Retention and Plasma Amino Acid Responses in Mature Geldings Fed Three Dietary Concentrations of Lysine

Six mature Quarter Horse geldings (age, 11.5 ± 4.7 years; body weight [BW], 526 ± 9.2 kg) were used in a replicated 3 × 3 Latin square design to determine the effects of three dietary lysine (Lys) levels on nitrogen (N) retention and plasma amino acid (AA) concentrations. The geldings were fed a basal diet of concentrate and Bermuda grass hay supplemented with synthetic essential amino acids (EAA) to meet estimated requirements for EAA. Geldings were fed one of three dietary treatments: (1) a basal diet deficient in Lys (L−; 0.027 g of Lys•kg⁻¹ BW•d⁻¹); (2) a basal diet supplemented with synthetic Lys to meet National Research Council (NRC; 2007) requirements (L+; 0.036 g of Lys•kg⁻¹ BW•d⁻¹); or (3) a basal diet supplemented at twice the recommended Lys requirement (2 × L; 0.070 g Lys•kg⁻¹ BW•d⁻¹). Horses fed the 2 × L diet had higher N intakes (P = .0056) than horses fed either the L− or L+ diet. However N retention (P = .63) was not different between treatments. Plasma Lys was greater (P < .0001) in 2 × L than L− and L+ diets. Plasma threonine (Thr; P < .01), methionine (Met; P = .03), and total plasma non-EAA (P < .05) concentrations decreased as dietary Lys increased. These results suggest N retention is not a good response criterion for evaluating the AA requirements of mature horses. However, plasma AA data indicated more efficient use of Thr and Met when horses were fed dietary Lys in concentrations greater than the current requirement recommended by the Nutrient Requirements of Horses (National Research Council, 2007).     

Necessary elements of precautionary management: implications for the Antarctic toothfish

We review the precautionary approach to fisheries management, propose a framework that will allow a systematic assessment of insufficient precaution and provide an illustration using an Antarctic fishery. For a single‐species fishery, our framework includes five attributes: (1) limit reference points that recognize gaps in our understanding of the dynamics of the species; (2) accurate measures of population size; (3) ability to detect population changes quickly enough to arrest unwanted declines; (4) adequate understanding of ecosystem dynamics to avoid adverse indirect effects; and (5) assessment of the first four elements by a sufficiently impartial group of scientists. We argue that one or more of these elements frequently fail to be present in the management of many fisheries. Structural uncertainties, which characterize almost all fisheries models, call for higher limit points than those commonly used. A detailed look into the five elements and associated uncertainties is presented for the fishery on the Antarctic toothfish in the Ross Sea (FAO/CCAMLR Area 88.1, 88.2), for which management was recently described as ‘highly precautionary’. In spite of having features that make the Ross Sea fishery ideal for the application of the precautionary approach, gaps in our knowledge and failure to acknowledge these gaps mean that current regulation falls short of being sufficiently precautionary. We propose some possible remedies.     

Sequencing of Culex quinquefasciatus establishes a platform for mosquito comparative genomics

Culex quinquefasciatus (the southern house mosquito) is an important mosquito vector of viruses such as West Nile virus and St. Louis encephalitis virus, as well as of nematodes that cause lymphatic filariasis. C. quinquefasciatus is one species within the Culex pipiens species complex and can be found throughout tropical and temperate climates of the world. The ability of C. quinquefasciatus to take blood meals from birds, livestock, and humans contributes to its ability to vector pathogens between species. Here, we describe the genomic sequence of C. quinquefasciatus: Its repertoire of 18,883 protein-coding genes is 22% larger than that of Aedes aegypti and 52% larger than that of Anopheles gambiae with multiple gene-family expansions, including olfactory and gustatory receptors, salivary gland genes, and genes associated with xenobiotic detoxification.     

A STUDY OF THE EPIDEMIOLOGY OF ANAPLASMA MARGINALE INFECTIONS OF CATTLE IN SOUTHERN QUEENSLAND: CLINICAL DISEASE AND THE PREVALENCE OF COMPLEMENT FIXING ANTIBODIES

SUMMARY A total of 386 clinical outbreaks of anaplasmosis were confirmed in Queensland south of the 22nd parallel over the period 1967 to 1976. Seventy-eight per cent of these outbreaks occurred during autumn and winter and only 6.8% involved cattle less than 1 year of age compared with 54.8% for cattle more than 3 years old. Dairy breeds were involved in 48.1% of 258 outbreaks compared with 51.9% for beef breeds. Bos taurus beef breeds were involved in 90.7% of 118 outbreaks compared with 9.3% for Bos indicus crossbreds. Approximately 3 times as much clinical disease per head of population was confirmed in tick (Boophilus microplus) infested southern Queensland south of the 25th parallel (south zone) than in areas between the 25th and 22nd parallel (north zone). A survey was conducted during 1975 in which 3,810 cattle from 241 herds were sampled on the basis of the distribution of the cattle population. The prevalence of CF reactors in tick-infested areas was 42.1% of 3,026 samples compared with 0.4% of 784 samples from tick-free areas. The prevalence in the north zone was 52.3% compared to 30.2% for the south zone and it also varied with the type of animal sampled. The prevalence in Bos taurus cattle was significantly greater than in Bos indicus types and it increased with age of the animal. No significant difference in susceptibility to infection attributable to sex could be demonstrated. Animals exposed to heavy to medium tick infestations had significantly more CF reactors than those exposed to light infestation. Higher stocking densities were associated with higher prevalence levels. Thus anaplasmosis is predominantly a disease of autumn and winter and of cattle greater than 1 year of age. Both clinical and subclinical infection occur only in tick-infested areas and B. microplus is considered to be the main, if not the only vector. Both clinical and inapparent infection are more frequent in Bos taurus than in Bos indicus types.     

Evaluation of an ELISA for detection of antibodies to Babesia bovis in cattle in Australia and Zimbabwe

An enzyme-linked immunosorbent assay (ELISA) for antibodies to Babesia bovis was evaluated in comparison with the indirect fluorescent antibody test (IFAT) in Australia and Zimbabwe. Positive and negative threshold values for the ELISA were set using sera from cattle of known infection status. Sensitivity and specificity estimates for the ELISA based on 158 positive sera from cattle experimentally infected with Australian isolates of B. bovis and 318 negative sera collected from B. bovis-free herds in Australia were 100% and 99.4%, respectively. The specificity of the assay in Africa, based on 328 sera from B. bovis-free herds in Kenya and South Africa, was 99.7%. The ELISA was compared with the IFAT using sequential sera from 16 calves experiencing primary B. bovis infections, and a total of 777 field sera collected from B. bovis-endemic herds in Australia and Zimbabwe. In primary infections, the ELISA and IFAT detected antibodies at or about the same time. With sera from endemic herds, the performance of the ELISA was at least comparable with that of the IFAT. Two hundred and fourteen of 221 sera that were negative by IFAT, were negative by ELISA, and 428 of 439 sera that were clearly positive by IFAT were positive by ELISA. Of 117 sera that gave equivocal (suspect or weak positive) results in the IFAT, 20 were positive by ELISA, 7 were suspect and 90 were negative. We conclude that the ELISA will be useful for epidemiological studies on B. bovis in Australia and Zimbabwe, and probably elsewhere.