The pharmacokinetics and metabolism of ivermectin in domestic animal species

The pharmacokinetic properties of drugs are closely related to their pharmacological efficacy. The kinetics of ivermectin are characterised, in general terms, by a slow absorption process, a broad distribution in the organism, low metabolism, and slow excretion. The kinetics vary according to the route of administration, formulation, animal species, body condition, age, and physiological status, all of which contribute to differences in drug efficacy. Characterisation of ivermectin kinetics can be used to predict and optimise the value of the parasiticide effects and to design programmes for parasite control. This article reviews the pharmacokinetics of ivermectin in several domestic animal species.     

Factors affecting the reproductive performance of Awassi sheep flocks in north-east of Jordan: An epidemiological study

A prospective cohort study was conducted using 32 randomly selected Awassi sheep flocks to identify factors hypothesized to be associated with the occurrence of pregnancy, twinning and fetal loss between August 2005 and May 2006 in the region of Al-Safawi (northeast of Jordan). Vitamins A and E and selenium concentrations were determined on 448 blood samples. Using the forward selection procedure of the logistic regression module, models with statistically significant risk factors (P?<?0.05) were constructed for three outcomes; pregnancy, twinning and fetal loss. Serum vitamin A concentration levels were associated with pregnancy (OR?=?2.26, 2.48), twinning (OR?=?6.49, 17.74) and fetal loss (OR?=?0.13, 0.19). Primiparous ewes were 48% less likely to become pregnant than fourth or higher parity ewes. The likelihood of twinning increased significantly in ewes up to the third parity. Ewes that were fed 700-900 g barley, 250-300 g wheat-bran per head per day and grazed on vegetables residues were 4.15 times more likely to have twins than ewes that were fed 600 g barley and 200 g wheat-bran per head per day. Fetal loss in first and second parity ewes was about 3 times more likely than that in third or higher-parity ewes. Ewes pregnant with twins were about 14 times more likely to have fetal loss than ewes carrying single fetus. Pregnant ewes of the stationary flocks were 37% less likely to have fetal loss than ewes of the semi-nomadic flocks. These results demonstrate that stationary Awassi sheep flocks had higher pregnancy and twinning rates and less pregnancy loss. Supplementation of vitamin A, providing sufficient quantity of dry feed and increasing ram: ewe ratio for primiparous ewes of semi-nomadic flocks is essential to improve Awassi sheep reproductive performance.     

Expression of toll‐like receptor 2 mRNA in bronchial epithelial cells is not induced in RAO‐affected horses

Reasons for performing study: Airway inflammation in recurrent airway obstruction (RAO) is triggered by housing affected horses in stables. It has been suggested that RAO is an allergic condition, but innate immune mechanisms are also involved. Fungal products activate innate immune mechanisms through toll‐like receptor 2 (TLR2). In human airway epithelium, TLR2 activation leads to interleukin (IL)‐8 production. This pathway is negatively regulated by the zinc finger protein A20. This study was performed to enhance understanding of innate immune mechanisms in RAO. Hypothesis: TLR2 and IL‐8 mRNA are elevated in RAO during stabling compared with controls. A20 mRNA is negatively associated with the numbers of airway inflammatory cells. Objectives: To determine TLR 2 , IL‐8 and A20 mRNA expression in lungs of stabled and pastured RAO‐affected and control horses. Methods: Airway obstruction and inflammatory cell counts in bronchoalveolar lavage were measured, and TLR 2 , IL‐8 and A20 mRNA expression quantified by qRT‐PCR in 6 RAO‐affected and 6 control horses, during and after exposure to hay and straw. Results: Airway obstruction and neutrophils were increased in RAO‐affected horses during stabling. While stabling increased IL‐ 8 , TLR2 and A20 mRNA were unaffected. TLR2 and A20 were significantly correlated (r = 0.83) and A20 mRNA was negatively associated with inflammatory cells. Potential relevance: Stabling does not lead to an increase in TLR2 expression. Other molecules or processes in the TLR2 cascade might be important in fungal‐induced airway inflammation. Equine epithelial‐derived A20 may be involved in modulation of airway inflammation.     

Effect of magnitude and direction of force on laryngeal abduction: Implications for the nerve‐muscle pedicle graft technique

Reasons for performing study: The nerve‐muscle pedicle graft technique is a treatment for recurrent laryngeal neuropathy (RLN), but the optimal placement of the pedicles within the cricoarytenoideus dorsalis (CAD) muscle is unknown. Hypothesis: The magnitude and direction of force placed on the muscular process of the left arytenoid cartilage affects the magnitude of laryngeal abduction. Methods: Five larynges were harvested from cadavers. Using increments of 0.98 N, a dead‐weight force generator applied a force of 0–14.7 N for 1 min each to the left muscular process at 0, 10, 20, 30, 40, 50, 60 and 70° angles. The rima glottis was photographed digitally 1 min after each force had been applied. Distances between biomarkers (Lines 1–4) and right to left angle quotient (RLQ) were used to assess the degree of left arytenoid abduction. Results: Increasing force from 0–14.7 N progressively and significantly increased the length of all lines and RLQ, indicating abduction. Furthermore, there was a significant interaction between force and angles. Applying forces of 7.84 N or greater (Lines 2–4 and RLQ) or 11.76 N or greater (Line 1) at angles 0, 10, 20 and 30° resulted in significantly greater abduction than applying the same forces at 40, 50, 60 and 70°. Angles of 0–30° correspond with the direction of pull exerted by the lateral compartment of the CAD muscle. Conclusion: In RLN, nerve‐muscle pedicle grafts should be placed preferentially in the lateral rather than in the medial compartment of the CAD muscle. Potential relevance: The information presented can be used to assist surgeons in the planning and application of the nerve‐muscle pedicle graft procedure.     

Protective antibody response produced by the chickens vaccinated with green coloured thermostable Newcastle disease virus

The efficacy of green-coloured (GC) I-2 Newcastle disease vaccine was determined in the present study. I-2 vaccine was mixed with a green coloured dye and stored at 4°C for 6 months while assayed for the virus infectivity at a monthly interval. Chickens were vaccinated with the GC vaccine by eye drop. Serum samples were collected from all birds before and after vaccination at weekly interval for 4 weeks and tested for haemagglutination-inhibition (HI) antibody against Newcastle disease virus (NDV). These chickens were challenged with NDV virulent strain four weeks after vaccination. The results showed that there was no difference between the infectivity titres of GC and uncoloured vaccines. However, chickens vaccinated with GC vaccine produced higher HI antibody titres than chickens vaccinated with uncoloured vaccine. Results from the challenge trial showed that all vaccinated chickens survived whereas all unvaccinated chickens died. The findings from this study have shown that the GC vaccine is safe and produced protective antibodies against NDV in vaccinated chickens. Wambura, P. N., 2008. Protective antibody response produced by the chickens vaccinated with green coloured thermostable Newcastle disease virus. Tropical Animal Health and Production.     

Interaction Between Entomopathogenic Fungi and Some Aphid Species in Thailand

Seven aphid species were screened with twelve entomopathogenic fungi for the selection of the most effective fungus. Beauveria bassiana CKB-048 caused the highest mortalities for all aphid species tested in their nymphal stage. The cowpea aphid (Aphis craccivora Koch) was chosen for further studies in its adult stage using B. bassiana CKB-048 as a biocontrol agent, and carbosulfan was used for a comparison in greenhouse testing. The mode of action of the fungal killing was studied by scanning electron microscopy. The endophytic colonization of the cowpea plant by B. bassiana CKB-048 was studied and confirmed using both stereo microscopy and transmission electron microscopy. The chitinase enzyme activity of cowpea plants after they were sprayed with the fungus or carbosulfan was found to fluctuate throughout five days. The lethal concentrations of B. bassiana CKB-048 suspensions that killed 50 % (LC₅₀) of A. craccivora was 6.69 × 10⁷ conidia/ml for the nymphs and 8.25 × 10⁷ conidia/ml for the adults. The time for lethality (LT₅₀) with a concentration of 2 × 10⁸ conidia/ml was 3.25 days for nymphs and 4 days for adults.     

Biological control of the millet head miner Heliocheilus albipunctella in the Sahelian region by augmentative releases of the parasitoid wasp Habrobracon hebetor: effectiveness and farmers’ perceptions

On-farm augmentative releases of the parasitoid Habrobracon hebetor (Say) for controlling the millet head miner (MHM) Heliocheilus albipunctella (de Joannis) were tested in Burkina Faso, Mali and Niger from 2007 to 2009. In addition, a survey of farmers’ perceptions of insect pests, with particular focus on MHM, and the biological control program (BCP) was carried out. There was a significant increase of MHM parasitization rate after the releases, with up to 97% mortality. The survey on farmers’ perceptions revealed a fair knowledge of the MHM and the ability of farmers to describe the pest and the damage it caused. Farmers claimed that the biocontrol agent H. hebetor is effective and perceived a significant gain in grain yield due to this control strategy. Implications of these findings for a large extension of the MHM biocontrol program are discussed.     

Biological control of botrytis bunch rot in organic wine grapes with the yeast antagonist Candida sake CPA‐1

The aim of this research was to confirm the efficacy of the yeast antagonist Candida sake CPA‐1 in suppressing botrytis bunch rot development, in an organic vineyard under Mediterranean conditions for two seasons, and compare its performance with that of two biologically based products currently registered for botrytis bunch rot control in New Zealand. In 2009, treatments applied were: commercial formulations of Ulocladium oudemansii (BOTRY‐Zen^®) and chitosan (ARMOUR‐Zen^®), C. sake CPA‐1 combined with the fatty acid‐based additive Fungicover^® and combinations of these products. All treatments were applied six times between early flowering and harvest and compared with an unsprayed control. In 2010, the treatments focused on C. sake and Fungicover and the number of applications was reduced from six to four. The population dynamics of U. oudemansii and C. sake were measured and wine quality tests were carried out in both seasons. Disease control achieved by C. sake treatments in 2009 were comparable to those achieved by BOTRY‐Zen and ARMOUR‐Zen. Applications of C. sake plus Fungicover between flowering and harvest significantly (P < 0·05) reduced botrytis bunch rot incidence and severity by 64% and 90%, respectively, compared with the untreated control in 2009, and by 67% and 89%, respectively, in 2010. Treatments did not adversely affect wine quality parameters after treated grapes were processed. Candida sake consistently provided effective control of botrytis bunch rot in grapes under different meteorological and disease pressure conditions, thereby improving its potential for future commercial applications.