Minimizing bias in a case-control study of farm injury

We report on our strategies to minimize bias in the FIRM study, a prospective case-control study of risk factors for serious farmwork-related injury. The study base is adult males working on farms in the catchment regions of 14 larger regional hospitals in one Australian state. Cases are identified on presentation to the emergency departments, while age-matched controls are recruited via random telephone survey. Eligibility criteria for cases include a maximum abbreviated injury severity score of at least 2, to minimize the potential for selection bias against those with less severe injuries treated outside the hospital system. An audit at one hospital showed that 93% of eligible patients identified in the electronic surveillance system had been approached regarding participation. Results to date show that 38% of those approached decline to have their contact details made available to researchers. Those who decline are asked to complete two key questions to enable comparison with those who participate. Control recruitment relies on telephoning regional households until an individual from the study base, satisfying the matching criteria, is identified. This process minimizes the potential for selecting against farm workers who may live off-farm. Ninety-four percent of age-matched eligible controls have participated to date. We are testing a dynamic pool of individuals identified as study base members but not matched on the first call to determine its effect on the probabilities of selection. Our strategies appear to be minimizing detection, selection, and response bias, thereby enhancing the validity of the study results.     

New techniques for breeding maize (Zea mays) varieties with fall armyworm resistance and market-preferred traits for sub-Saharan Africa

Deploying maize varieties with fall armyworm (Spodoptera frugiperda [J.E. Smith]; FAW) resistance, desirable product profiles (PPs) and climate resilience is fundamental for food and economic security in sub-Saharan Africa (SSA). This study reviewed and identified challenges and opportunities for effective and accelerated breeding of demand-led maize hybrids with FAW resistance and adaptation to the diverse agro-ecologies of SSA. Lessons were drawn on improving breeding efficiency through adequate genetic variation delivered via prebreeding programmes, speed breeding and a reduced breeding stage plan. Appropriate PPs aligned with demand-led breeding approaches were highlighted as foundations for variety design and commercialization. Challenges to accelerated FAW resistance breeding in maize included inadequate funds and modern tools; poor adaptation of some exotic donor parental lines; lack of information on FAW resistance among local varieties; lack of integration of molecular markers associated with FAW resistance and agronomic traits into selection plans; and limited infrastructure for FAW rearing and germplasm screening. Integration of modern breeding tools and scientific innovations were recommended for accelerated development and release of FAW resistant and market-preferred maize varieties.     

Insect herbivores and pathogens of Alnus species in Uganda

Published documentation of insect pests and pathogens associated with Alnus species in Africa is very scarce. We surveyed damaging insects and pathogens, and arthropod natural enemies on Alnus acuminata and A. nepalensis in Kabale and Mbale districts, Uganda between March 1999 and August 2000 in order to identify the range and relative abundance of arthropods and pathogens associated with the Alnus species. Frequently encountered damaging insects on the Alnus species included Apis mellifera, Apion globulipenne, a Systates sp. (Coleoptera: Curculionidae), Phymateus viridipes, a Lobotrachelus sp. (Coleoptera: Curculionidae), Coloborrtics corticina and some Chrysomelidae. Some species such as Aphis fabae, Parastictococcus multispinosus and a Cacopsylla sp. (Homoptera: Psyllidae) were observed feeding on other agroforestry tree species and/or crops although they generally occurred at low population intensities. Spiders and parasitic Hymenoptera were the most common natural enemies. Diseases were more severe in nurseries than in the field. Damping-off caused by Fusarium oxysporum, Septoria brown leaf spot and stem canker were the most serious diseases of Alnus. The array of damaging insects and pathogens indicates a potential danger to the cultivation of Alnus species in Uganda as adoption of the species for agroforestry continues to expand in the country. In view of the increasing demand for Alnus species for agroforestry in Uganda, regular pest monitoring and appropriate control strategies are necessary.This revised version was published online in November 2005 with corrections to the Cover Date.     

Impact of an experimental PRRSV and Streptococcus suis coinfection on the pharmacokinetics of ceftiofur hydrochloride after intramuscular injection in pigs

This study determined the impact of porcine reproductive and respiratory syndrome virus (PRRSV) and Streptococcus suis coinfection on the pharmacokinetic (PK) profile of ceftiofur hydrochloride in pigs after intramuscular (i.m.) injection. Eighteen clinically normal crossbred gilts were assigned by weight into a challenge group (10 pigs) and control group (eight pigs). Pigs in both groups received a single i.m. injection of ceftiofur hydrochloride (Excenel RTU Sterile Suspension; Zoetis) at a 5 mg/kg BW dose. Serial blood samples were collected to characterize the plasma concentration curve. After a 10 days drug washout period, the challenge group was inoculated with 2 mL of PRRSV isolate VR‐2385 (10^5.75 50% tissue culture infective doses per mL) intranasally and 8 days later inoculated S. suis. When clinical disease was evident, the second PK assessment began in both challenge and control groups. Coinfected pigs demonstrated lower values of AUC and C_MAX, but higher values of Cl/F and Vz/F indicating drug kinetics were altered by infection. The data from this study have implications on ceftiofur treatment regimens in diseased pigs.     

Feedback of 17 beta-estradiol on secretion of luteinizing hormone during different seasons of the year

The working hypothesis was that the amount of increase in secretion of luteinizing hormone (LH) that results from positive feedback of 17 beta-estradiol (E2) is dependent on season of the year in mature bovine females. Seven beef cows, ovariectomized approximately 2 mo before the initiation of the experiment, were used in the initial year (1983) of the study. Three of the ovariectomized cows (OVX-E2) received an sc E2 implant, which provided low circulating levels of E2. The remaining four cows (OVX) were not implanted. Blood samples were collected serially (at 10-min intervals for 6 h) at each spring and fall equinox and at each summer and winter solstice. This protocol was replicated with a different group of cows in 1985 (OVX-E2, n = 4; OVX, n = 6). Concentration of LH in blood serum was quantified in all samples. Concentration of E2 in blood serum was measured in pools of samples from each serial blood collection. Concentrations of E2 were higher (P less than .05) in the implanted cows. Mean concentration of LH and amplitude of pulses of LH were higher (P less than .05) at each season of the year in cows that were ovariectomized and implanted with E2 than in cows that were ovariectomized and did not receive E2. An effect of season of the year on mean concentration of LH was detected (P less than .01). No influence of season or E2 was detected for frequency of pulses of LH. There was no significant treatment X season interaction.(ABSTRACT TRUNCATED AT 250 WORDS)