The oral application of the Onderstepoort biological products fowl typhoid vaccine, its safety, efficacy and duration of protection in commercial laying hens

This project was undertaken to establish whether the Onderstepoort Biological Products Fowl Typhoid (OBPft) vaccine registered as an injectable vaccine was effective and safe when administered orally to commercial layers. Its efficacy and duration of protection were compared to the intramuscular injectable route. Commercial brown layer hens were used as they were found to be highly susceptible to Salmonella gallinarum infections. In the safety trial birds were euthanased at timed intervals spanning 4-weeks post vaccination. Necropsies were performed and samples were taken and tested. No clinical signs or mortalities could be attributed to the OBPft vaccine. No active shedding of the vaccine strain could be detected. Slight pathological changes were noted with both routes of vaccination; however these changes were transient, returning to normal within the observation period. The injected group showed a better serological response with the serum agglutination test than the orally vaccinated groups. In the duration of protection trial the two routes of vaccination were compared, the birds were challenged at three 8-week intervals post vaccination. All the unvaccinated birds died. The protection offered to the vaccinated groups was good when birds were challenged 8 and 16-weeks after vaccination. However, this dipped steeply by the challenge 24-weeks post vaccination. Statistically (ANOVA, p<0.05) it was found that there was no significant difference between the protection offered by either the oral or injected route of vaccination with the OBPft vaccine.Dissertation (MSc (Veterinary Science))--University of Pretoria, 2006.Production Animal Studiesunrestricte

Salt intake and regulation in two passerine nectar drinkers : whitebellied sunbirds and New Holland honeyeaters

Avian nectarivores face the dilemma of having to conserve salts while consuming large volumes of a dilute, electrolyte-deficient diet. This study evaluates the responses to salt solutions and the regulation of salt intake in whitebellied sunbirds (Cinnyris talatala) and New Holland honeyeaters (Phylidonyris novaehollandiae). Birds were first offered a choice of four sucrose diets, containing no salt or 25, 50 or 75 mM NaCl. The experiment was repeated using five sucrose concentrations (0.075 to 0.63 M) as the base solution. Both species ingested similar amounts of all diets when fed the concentrated base solutions. However, when birds had to increase their intake to obtain enough energy on the dilute sucrose diets, there was a general avoidance of the higher salt concentrations. Through this diet switching, birds maintained constant intakes of both sucrose and sodium; the latter may contribute to absorption of their sugar diets. A second, no-choice experiment was designed to elucidate the renal concentrating abilities of these two nectarivores, by feeding them 2 0.63 M sucrose containing 5-200 mM NaCl over a 4 h trial. In both species, cloacal fluid osmolalities increased with diet NaCl concentration, but honeyeaters tended to retain ingested Na+, while sunbirds excreted it. Comparison of Na+ and K+ concentrations in ureteral urine and cloacal fluid showed that K+, but not Na+, was reabsorbed in the lower intestine of both species. The kidneys of sunbirds and honeyeaters, like those of hummingbirds, are well suited to diluting urine; however they also appear to concentrate urine efficiently when necessary.This project was funded by the National Research Foundation of South Africa, the University of Pretoria and the Australian Research Council. The Gauteng Directorate of Nature Conservation granted permits to capture and house the sunbirds, and the Australian Department of Environment and Conservation approved our use of honeyeaters. All animal care procedures and experimental protocols adhered to institutional regulations of Murdoch University (R1137/05) and the University of Pretoria (EC013-07).http://link.springer.com/journal/360am2013ab201

Coloured and toxic nectar : feeding choices of the Madagascar giant day gecko, Phelsuma grandis

Coloured nectar is a rare phenomenon best known from islands and insular habitats. Islands are also known for lizard pollination, where coloured nectar potentially acts as a visual cue to attract pollinators, advertising the sweet reward. However, nectar may also contain secondary metabolites with toxic or deterrent effects. The aim of this study was to determine which factors are important as artificial nectar choice determinants to the Madagascar giant day gecko, Phelsuma grandis, an island pollinator: artificial nectar colour, artificial nectar colour saturation, artificial nectar conspicuousness and/or the presence of the alkaloid nicotine. Coloured artificial nectar and the darkest artificial nectar colour saturation were found to be important visual cues for the geckos, while the contrast between artificial nectar and petal colour was not. Geckos were deterred only by high nicotine concentrations (1000 lM in 0.63 M sucrose) and may even prefer low nicotine concentrations to sucroseonly solutions. Given their overall fondness for sugar solutions, Madagascar giant day geckos are likely to be important pollinators of Malagasy plant species that produce enough nectar to attract them, and plants with coloured nectar and/or secondary metabolites may have evolved those traits to attract the geckos in particular.This work was supported by the South African National Research Foundation (grant number 73671) and the University of Pretoria.http://onlinelibrary.wiley.com./journal/10.1111/(ISSN)1439-0310hb2013ab201

The integration of osmoregulation and energy balance in nectar-feeding birds

Nectar-feeding birds must ingest copious amounts of water due to their liquid diet. Large volumes of preformed water in the dilute diet mean that birds feeding on these diets risk the loss of solutes in order to excrete this water. Previous studies have found that on dilute diets (<0.25 mol.l-1), white-bellied sunbirds (Cinnyris talatala) are unable to maintain energy balance and lose excessive amounts of electrolytes via cloacal fluid. Therefore how these small nectarivores handle water and electrolytes is intricately linked with how they obtain energy from a nectar diet. Understanding the physiological mechanisms for handling water and electrolytes will reveal how nectarivorous birds can deal with a range of nectar diet concentrations. These mechanisms were investigated through a series of experiments that exposed birds to varying electrolyte and water loads through compensatory feeding (requiring birds to ingest greater volumes of energy-dilute diets than energy-concentrated diets). I tested the effect of adding electrolytes to a 0.1 mol.l-1 sucrose diet in white-bellied sunbirds (Cinnyris talatala) and New Holland honeyeaters (Phylidonyris novaehollandiae). Addition of salts (NaCl and KCl) enabled both species to drink significantly more of the dilute diet than in the absence of salt. On 20 mmol.l-1 combined salts, both sunbirds and honeyeaters consumed an extraordinary 8 times their body mass in fluid daily. KCl alone had no effect on consumption but a loss of Na+ clearly limits consumption of extremely dilute diets. Plasma Na+ levels, and sucrose assimilation efficiencies confirmed this, leading to the conclusion that Na+ depletion on very dilute salt-free diets interferes with water excretion or sugar digestion and/or assimilation. I then evaluated the behavioural responses of these two nectarivore species to salt solutions. Preference tests (simultaneously presenting birds with a range of diets with salt added and repeating this experiment with different sugar concentration base solutions) showed that both species ingested similar amounts of all diets when fed the concentrated base solutions (i.e. low total intake). However, when the birds had to increase their intake of more dilute sucrose diets to maintain energy balance, they avoided the higher salt concentrations. Through active diet switching, birds maintained constant intakes of both sucrose and sodium. To test renal concentrating abilities of these two nectarivores, I conducted no choice tests, by feeding them 0.63 mol.l-1 sucrose containing 5-200 mmol.l-1 NaCl over a 4 h trial. In both species, cloacal fluid osmolalities increased with diet NaCl concentration, but while sunbirds excreted all the Na+ ingested, honeyeaters retained sodium on the more concentrated diets. The kidneys of sunbirds and honeyeaters, like those of hummingbirds, are well suited to diluting urine; however unlike hummingbirds, sunbirds and honeyeaters also appear to concentrate urine efficiently when necessary. The final part of this thesis examined how these birds deal with excess preformed water loads on dilute nectar diets. I used the elimination of intramuscular-injected [14C]-L-glucose and 3H2O to quantify intestinal and renal water handling on diets varying in sugar concentration. Both species showed significant modulation of intestinal water absorption, allowing excess water to be shunted through the intestine on dilute diets and therefore reducing renal load. During the natural overnight fast, both sunbirds and honeyeaters arrested whole kidney function, shutting down GFR as another way of reducing renal load. Both sunbirds and honeyeaters are able to maintain osmotic balance on markedly different diet concentrations and hence preformed water loads, by varying intestinal water absorption as well as excretion via the intestine and kidneys.Thesis (PhD)--University of Pretoria, 2013.gm2013Zoology and Entomologyunrestricte

A comparison of the oral application and injection routes using the Onderstepoort Biological Products Fowl Typhoid vaccine, its safety, efficacy and duration of protection in commercial laying hens

This study was undertaken to establish whether the Onderstepoort Biological Products Fowl Typhoid (OBPft) vaccine registered as an injectable vaccine was effective and safe when administered orally to commercial layers. Its efficacy and duration of protection were compared with application by intramuscular injection. Commercial brown layer hens were used as they were found to be highly susceptible to Salmonella gallinarum infections. In the vaccine safety trial birds were euthanased at timed intervals spanning 4 weeks post-vaccination. Necropsies were performed and samples were taken and tested. No clinical signs or mortalities could be attributed to the OBPft vaccine nor could active shedding of the vaccine strain be detected. Slight pathological changes were noted with both routes of vaccination; however, these changes were transient, returning to normal within the observation period. The injected groups showed a better serological response with the rapid serum plate agglutination (RSPA) test than the orally vaccinated groups. In the duration of protection trial, birds were challenged at 3-8-week intervals post-vaccination. All unvaccinated birds died. Protection 8 and 16 weeks after vaccination was above 60%, by 24 weeks after challenge, the vaccine protection was below 30%. It was found that there was no significant difference (P < 0.05) in the protection offered by either the oral or injected route of vaccination with the OBPft vaccine

Reintroduction of the Extinct-in-the-Wild Spix’s Macaw (<i>Cyanopsitta spixii</i>) in the Caatinga Forest Domain of Brazil

We describe efforts to reintroduce the extinct-in-the-wild Spix’s Macaw (Cyanopsitta spixii) within its historical range in eastern Brazil. Twenty captive-reared Spix’s Macaws were released, along with 15 Blue-Winged Macaws (Primolius maracana), as heterospecific flocks in two events during the dry and rainy seasons of 2022. We monitored the release groups through daily observation and telemetry tracking from early June 2022 to early June 2023. We documented an overall first-year survival of 58.3% (CI: 37.8–78.7%), with 65% of Spix’s Macaws establishing a stable area of activity within 5 km of the release site, excluding any temporary long-distance forays. Eighty-five percent of released Spix’s Macaws exhibited flock cohesion, including interactions with and integration into wild Blue-Winged Macaw groups at the release site. Several released Spix’s Macaws formed pair-bonds with conspecifics and engaged in nest cavity exploration, breeding behavior, and territorial defense of nest sites, with three females also laying and incubating eggs. One nesting pair successfully hatched and reared chicks in an artificial nest cavity. These releases employed a novel reintroduction strategy using a surrogate species model, the sympatric Blue-Winged Macaw, to “mentor” and facilitate post-release adaptation by the target species and increase the total number of individuals in the release cohort. Lastly, participatory monitoring by local citizens is considered a way to engage and involve local communities in species and habitat conservation and potentially create new employment opportunities in the region

The sweet life: diet sugar concentration influences paracellular glucose absorption

Small birds and bats face strong selection pressure to digest food rapidly in order to reduce digesta mass carried during flight. One mechanism is rapid absorption of a high proportion of glucose via the paracellular pathway (transfer between epithelial cells, not mediated by transporter proteins). Intestinal paracellular permeability to glucose was assessed for two nectarivorous passerines, the Australian New Holland honeyeater (Phylidonyris novaehollandiae) and African white-bellied sunbird (Cinnyris talatala) by measuring the bioavailability of radiolabelled, passively absorbed l-glucose. Bioavailability was high in both species and increased with diet sugar concentration (honeyeaters, 37 and 81% and sunbirds, 53 and 71% for 250 and 1000 mmol l−1 sucrose diets, respectively). We conclude that the relative contribution of paracellular to total glucose absorption increases with greater digesta retention time in the intestine, and paracellular absorption may also be modulated by factors such as intestinal lumen osmolality and interaction with mediated glucose uptake. The dynamic state of paracellular absorption should be taken into account in future studies

Early antiretroviral therapy initiation and mortality among infants diagnosed with HIV in the first 12 weeks of life

AB Background: Based on clinical trial results, the WHO recommends infant HIV testing at age 4-6 weeks and immediate antiretroviral therapy (ART) initiation in all HIV-infected infants. Little is known about the outcomes of HIV infected infants diagnosed with HIV in the first weeks of life in resource-limited settings. We assessed ART initiation and mortality in the first year of life among infants diagnosed with HIV by 12 weeks of age. Methods: Cohort of HIV-infected infants in Kinshasa and Blantyre diagnosed before 12 weeks to estimate 12-month cumulative incidences of ART initiation and mortality, accounting for competing risks. Multivariate models were used to estimate associations between infant characteristics and timing of ART initiation. Results: 121 infants were diagnosed at a median age of 7 weeks (interquartile range 6-8). The cumulative incidence of ART initiation was 46% (95% CI: 36%, 55%) at 6 months and 70% (95% CI: 60%, 78%) at 12 months. Only age at HIV diagnosis was associated with ART initiation by age 6 months, with a subdistribution hazard ratio of 0.70 (95% CI: 0.52, 0.91) for each week increase in age at DNA PCR test. The 12-month cumulative incidence of mortality was 20% (95% CI: 13%, 28%). Conclusions: Despite early diagnosis of HIV, ART initiation was slow and mortality remained high, underscoring the complexity in translating clinical trial findings and WHO guidance into real-life practice. Novel and creative health system interventions will be required to ensure that all HIV infected infants achieve optimal treatment outcomes under routine care settings