Design and descriptive epidemiology of the Infectious Diseases of East African Livestock (IDEAL) project, a longitudinal calf cohort study in western Kenya

BACKGROUND: There is a widely recognised lack of baseline epidemiological data on the dynamics and impacts of infectious cattle diseases in east Africa. The Infectious Diseases of East African Livestock (IDEAL) project is an epidemiological study of cattle health in western Kenya with the aim of providing baseline epidemiological data, investigating the impact of different infections on key responses such as growth, mortality and morbidity, the additive and/or multiplicative effects of co-infections, and the influence of management and genetic factors. A longitudinal cohort study of newborn calves was conducted in western Kenya between 2007-2009. Calves were randomly selected from all those reported in a 2 stage clustered sampling strategy. Calves were recruited between 3 and 7 days old. A team of veterinarians and animal health assistants carried out 5-weekly, clinical and postmortem visits. Blood and tissue samples were collected in association with all visits and screened using a range of laboratory based diagnostic methods for over 100 different pathogens or infectious exposures. RESULTS: The study followed the 548 calves over the first 51 weeks of life or until death and when they were reported clinically ill. The cohort experienced a high all cause mortality rate of 16% with at least 13% of these due to infectious diseases. Only 307 (6%) of routine visits were classified as clinical episodes, with a further 216 reported by farmers. 54% of calves reached one year without a reported clinical episode. Mortality was mainly to east coast fever, haemonchosis, and heartwater. Over 50 pathogens were detected in this population with exposure to a further 6 viruses and bacteria. CONCLUSION: The IDEAL study has demonstrated that it is possible to mount population based longitudinal animal studies. The results quantify for the first time in an animal population the high diversity of pathogens a population may have to deal with and the levels of co-infections with key pathogens such as Theileria parva. This study highlights the need to develop new systems based approaches to study pathogens in their natural settings to understand the impacts of co-infections on clinical outcomes and to develop new evidence based interventions that are relevant

Field training in the South African Police Service

Study project (M.P.A.) -- University of Stellenbosch, 1995.Full text to be digitised and attached to bibliographic record

Measurement of concentrations of faecal glucocorticoid metabolites in free-ranging African elephants within the Kruger National Park

During the past several years, non-invasive monitoring of steroid metabolites in faeces of elephants has become an increasingly popular technique to generate more information about the causal relationship between hormones and behaviour in both living elephant species. This is important knowledge which can be used to optimise local conservation and wildlife management by finding new strategies for better elephant population management and control. In this context, however, information about an actual involvement of the hypothalamic-pituitary-adrenal axis during assumable stressful events is still limited, especially for wildlife populations. One difficulty in discovering such information is often the lack of reliable data for hormone baseline levels. Therefore, the aim of this study was to determine baseline concentrations of faecal glucocorticoid metabolites that could be expected within age classes and between seasons in African elephants (Loxodonta africana) in the Kruger National Park (KNP ). A total of 374 faecal samples were collected from randomly located family herds in the southern KNP between May 2002 and August 2005. The samples were analysed for immunoreactive concentrations of faecal glucocorticoid metabolites using a validated enzyme immunoassay for 3α,11oxo-cortisol metabolites(3α,11oxo-CM). All samples were grouped according to the estimated age class of the subject using a field method based on bolus diameter, and regarding the ecological season collected. No significant differences in faecal 3α,11oxo-CM concentrations were found across age classes (H3 = 7.54; p = 0.057), but the mean 3α,11oxo-CM concentration of samples collected in the dry season (n = 196) was significantly higher than in the wet season (n = 178) (u = 15206.50; p = 0.032), which indicates a possible physiological stress situation due to a decline in food quantity and quality. The information generated in this study represents a reliable data set for baseline concentrations of faecal glucocorticoid metabolites for elephants within the KNP and can be used to measure the stressrelated effects of translocations, management actions and the impact of chosen land use activities

A stochastic model accommodating the FAMACHA© system for estimating worm burdens and associated risk factors in sheep naturally infected with Haemonchus contortus

A previously developed multiple regression algorithm was used as the basis of a stochastic model to simulate worm burdens in sheep naturally infected with Haemonchus contortus over five consecutive Haemonchus seasons (November to January/February) on a farm in the summer rainfall region in South Africa, although only one season is discussed. The algorithm associates haemoglobin levels with worm counts in individual animals. Variables were represented by distributions based on FAMACHA© scores and body weights of sheep, and Monte Carlo sampling was used to simulate worm burdens. Under conditions of high disease risk, defined as the sampling event during the worm season with the lowest relative mean haemoglobin level for a class of sheep, the model provided a distribution function for mean class H. contortus burdens and the probability of these occurring.\ud \ud A mean H. contortus burden for ewes (n = 130 per sample) of approximately 1000 (range 51–28,768) and 2933 (range 78–44,175) for rams (n = 120 per sample) was predicted under these conditions. At the beginning of the worm season when the risk of disease was lowest (i.e. when both classes had their highest estimated mean haemoglobin levels), a mean worm burden of 525 (range 39–4910) for ewes and 651 (range 37–17,260) for rams was predicted. Model indications were that despite being selectively drenched according to FAMACHA© evaluation, 72% of the ewes would maintain their mean worm burden below an arbitrarily selected threshold of 1000 even when risk of disease was at its highest. In contrast, far fewer rams (27%) remained below this threshold, especially towards the end of the worm season.\ud \ud The model was most sensitive to changes in haemoglobin value, and thus by extrapolation, the haematocrit, which is used as the gold standard for validating the FAMACHA© system. The mean class haemoglobin level at which there was a 50% probability of worm burdens being ≤1000 worms was 7.05 g/dl in ewes and 7.92 g/dl in rams

Validation of the FAMACHA© eye colour chart using sensitivity/specificity analysis on two South African sheep farms

A validation study of the FAMACHA© system for clinical evaluation of anaemia due to Haemonchus contortus was conducted on two commercial sheep farms in the summer rainfall region of South Africa. In this region, the Haemonchus season lasts from October to April. On Farm 1 the system was tested over a period of five successive years in consecutive sets of young stud Merino replacement rams and ewes examined at intervals of 3–5 weeks over each Haemonchus season, under routine farming conditions. When FAMACHA© scores of 3, 4, and 5 and haematocrit values of ≤22%, ≤19%, and ≤15% were separately considered to be anaemic, sensitivity on Farm 1 ranged from a maximum of 83% for a haematocrit cut-off of ≤15%, to 40% for a haematocrit cut-off of ≤22%. Sensitivity increased to 93% when FAMACHA© scores of 2, 3, 4, and 5 were considered anaemic at a cut-off value of ≤19%, but the positive predictive value decreased to 0.43, indicating that many non-anaemic animals would be treated. The analysis indicated a high level of classification bias on Farm 1, with the animals consistently being classified one FAMACHA© category lower (i.e. less anaemic) than reality.\ud \ud On Farm 2 the test was conducted over two successive years in yearling rams evaluated at weekly to fortnightly intervals during each worm season. Every ram judged to be in FAMACHA© category 4 or 5 was bled for haematocrit determination, and it was only dewormed with effective anthelmintics if the haematocrit was 15% or lower. When FAMACHA© scores of 3, 4, and 5 and haematocrit values of ≤22% and ≤19% were separately considered to be anaemic on Farm 2, sensitivity ranged from 64% for a haematocrit cut-off of ≤22%, to 80% for a cut-off of ≤19%.\ud \ud For identical haematocrit cut-off values and proportions of the sampled flock considered to be diseased as for Farm 1, sensitivity was always higher for Farm 2. On the other hand, further analysis of the data indicated that the magnitude of the error on Farm 1 was very consistent on average over the entire trial period.\ud \ud The results of this study indicate that (i) persons introduced to the system should not only be trained, but also be evaluated for accuracy of application; (ii) the sensitivity of the FAMACHA© diagnostic system should ideally be evaluated at shorter intervals to avoid production losses due to failure to detect anaemic animals which may be at risk of death; (iii) that calibration of the FAMACHA© scoring is essential per individual evaluator, and (iv) that animals should be examined at weekly intervals during periods of the highest worm challenge

African Natural Plant Products Volume II: Discoveries and Challenges in Chemistry, Health, and Nutrition

Book chapterThe effect of rooibos (Aspalathus linearis) herbal tea consumption on the iron status of adults at risk for developing coronary heart disease was a secondary objective of a recent clinical study. After consuming six cups of rooibos daily for six weeks, serum iron, ferritin, transferrin, TIBC and Fe saturation were determined to assess the iron status of the participants. Dietary intakes were calculated with the use of dietary records completed during the study periods. No significant changes in these biochemical parameters were recorded after completion of the rooibos and control study periods. Results showed that consumption of rooibos tea did not adversely affect the iron status of this study population when taking into account the habitual dietary composition and genetic variation in the HFE gene affecting iron absorption

Systems Biology of Free Radicals and Antioxidants

Book chapterThe South African fynbos plant, Aspalathus linearis (Brum.f) Dahlg. (Fabaceae, Tribe Crotalarieae), is traditionally used as a herbal tisane referred to as rooibos or redbush. This plant has claimed medicinal properties based mostly on anecdotal evidence. Rooibos is naturally caffeine free and contains a unique blend of polyphenolic compounds. Based on its in vitro antioxidant potential, a few studies also suggest modulation of oxidative stress/damage by rooibos extracts in experimental animals. More recent studies have examined the bioactivity of rooibos in humans. Together, these factors have contributed to the popularity of this herbal tea as a health beverage, both locally and internationally. This chapter focuses on the in vitro antioxidant activity of rooibos and discusses recent animal and human studies