Extraction and analysis of moxidectin in wombat plasma and faeces

Sarcoptic mange in wombats results from a skin infestation by Sarcoptes mites and if untreated, results in a slow and painful death. Moxidectin is a pesticide used to treat internal and external parasites in cattle, but has shown to effectively treat other animals, including wombats. Two methods were developed to analyse wombat plasma, and methods were also developed to analyse faeces and fur. Moxidectin-D3 was used as an internal standard and behaved almost identically to moxidectin, resulting in recoveries of 95-105 % across the three matrices, even when matrix interferences caused signal suppression as high 20 %, or when moxidectin loss was high. This was presumably due to the high binding efficiency of plasma for MOX and MOX-D3. Moxidectin limits of detection were 0.01 ng/mL in plasma, 0.3 ng/g dry weight equivalent for faeces and 0.5 ng/g for fur. This study also developed a method to isolate plasma macromolecules, allowing the extraction of bound moxidectin for quantitative purposes, with an LoQ of 0.05 ng/mL. This method was subsequently used to determine that moxidectin was 97-99.4 % bound to lipoproteins in wombat plasma and 98-99 % bound in sheep, cow and horse plasma. The method reported for plasma was quick, cheap, and conducive to large sample batches, while providing high sensitivity. While faecal samples required additional cleanup steps to reduce the matrix effect, co-extracted matrix components such as undigested chlorophyll continued to result in ionisation suppression in the MS/MS. The methods reported here were used to monitor moxidectin in wombats treated with a single pour-on treatment, and confirmed that the moxidectin concentration in wombat plasma had decreased by more than 90 % by 28 days after application, while providing protection against sarcoptic mites over the majority of their life cycle. Clearance of moxidectin occurred via faecal elimination over the four week period and while moxidectin accumulated on fur due to application as a pour-on, concentrations declined rapidly by the four week period as fur fell out and was replaced by fresh fur that did not contain moxidectin.

Evaluation of Antiviral Activity of Ivermectin against Infectious Bovine Rhinotracheitis Virus in Rabbit Model

Infectious bovine rhinotracheitis (IBR) caused by bovine herpes virus 1 (BoHV-1) can lead to enormous economic losses in the cattle industry. Vaccine immunization is preferentially used to decrease its transmission speed and resultant clinical signs, rather than to completely stop viral infection. Therefore, a drug effective in treating IBR is urgently needed. Our previous work demonstrated that ivermectin significantly inhibited viral replication in a cell infection model. This study aimed to investigate its antiviral effects in vivo by using a rabbit infection model. The viral inhibition assay was first used to confirm that ivermectin at low concentrations (6-25 nM) could reduce viral titers (TCID50) significantly (p < 0.001) at 24 h post-infection. In rabbits, ivermectin was administrated with one to three doses, based on the recommended anti-parasite treatment dosage (0.2 mg/kg bodyweight) through subcutaneous injection at different days post-infection in the treated IBRV infection groups, while non-treated infection group was used as the control. The infected rabbits showed hyperthermia and other clinical signs, but the number of high-fever rabbits in the ivermectin treatment groups was significantly lower than that in the non-treated infection group. Furthermore, in ivermectin treatment groups, the cumulative clinical scores correlated negatively with drug doses and positively with delay of administration time post-infection. The overall nasal shedding time in ivermectin-treated groups was two days shorter than the non-treated challenge group. At the same time point, the titer of neutralizing antibodies in the treatment group with triple doses was higher than the other two-dose groups, but the difference between the treatment groups decreased with the delay of drug administration. Correspondingly, the serious extent of lung lesions was negatively related to the dosage, but positively related to the delay of drug administration. The qPCR with tissue homogenates showed that the virus was present in both the lung tissues and trigeminals of the infected rabbits. In conclusion, ivermectin treatment had therapeutic effect by decreasing clinical signs and viral shedding, but could not stop virus proliferation in lung tissues and trigeminals.

Development and validation of an LC-MS/MS method for the quantification of the anthelmintic drug moxidectin in a volumetric absorptive microsample, blood, and plasma: Application to a pharmacokinetic study of adults infected with Strongyloides stercoralis in Laos

Moxidectin is a promising candidate for addition to the lean repertoire of drugs against neglected tropical diseases (NTD) including strongyloidiasis. Pharmacokinetic (PK) and -dynamic studies are required to support its clinical development. Microsampling approaches enable PK studies in the challenging environments where NTDs are most prevalent, due to simplified collection and processing. We developed a liquid chromatography tandem mass spectrometry method for the sensitive quantification of moxidectin in human blood obtained by capillary sampling with the microsampling device Mitra® compared to blood and plasma obtained by venous sampling. Sample preparation consisted of protein precipitation, evaporation and reconstitution and also included phospholipid filtration for blood and plasma. Moxidectin was detected by multiple reaction monitoring (640.4 → 528.5 m/z) using a Luna C8(2) (30 × 2.0 mm, 3 µm particle size, 100 Å) analytical column with a gradient program of 6 min duration. Validation was performed with respect to accuracy, precision, sensitivity, selectivity, linearity, stability, recovery, and haematocrit influence with a limit of quantification of 0.5 and 2.5 ng/mL, for venous and capillary blood respectively. Moxidectin was stable up to 2 months at storage condition (blood and plasma: -20 °C, microsamples: room temperature), 3 cycles of temperature shift, for at least 4 h on the bench-top and 24 h in the autosampler (4 °C). Deviations of inter- and intra-assay accuracy and precision were smaller than 12.6% and recoveries were in the range of 80.7-111.2%. The method was applied to samples obtained from nine Strongyloides stercoralis-infected adults from northern Laos. A good agreement in the time-concentration profiles of moxidectin and a high consistency in PK parameters was found between the different matrixes and sampling strategies: e.g. identical time to reach maximal concentration of 4.0 h and a similar maximal concentration of 83.9-88.5 ng/mL of moxidectin. The simple and practical capillary procedure using Mitra® microsampling has been demonstrated to be suitable for PK studies of moxidectin and will pave the way for future PK studies.

Effects of verapamil on the pharmacokinetics of ivermectin in rabbits

This study was aimed to investigate the influence of verapamil-mediated inhibition of P-glycoprotein (P-gp) on the pharmacokinetics of ivermectin (IVM) given orally and subcutaneously (SC) to rabbits. Twenty New Zealand rabbits were allotted to 4 groups (n = 5) and received IVM either orally or SC (0.4 mg/kg) alone or co-administered with verapamil (2 mg/kg SC, 3 times at a 12-hr interval). Plasma, fecal, and urine samples were collected over 30 days after medication to assess IVM concentrations in these samples. No significant differences were observed in the pharmacokinetic parameters of IVM between oral and SC administrations. The area under the plasma concentration-time curve was higher (p < .05) after IVM (oral)/verapamil treatment, compared with oral IVM alone. Moreover, the time to the C_max of IVM was shorter (p < .05), whereas the elimination half-life and the mean residence time were longer (p < .05) in the presence of verapamil. The IVM/verapamil combination administered orally or SC reduced fecal IVM concentrations, compared with IVM alone. In conclusion, the significant changes by verapamil on the pharmacokinetics of IVM, likely due to the inhibition of a P-gp-mediated intestinal secretion, may change IVM's antinematodal activity.

The scabicide effect of moxidectin in vitro and in experimental animals: Parasitological, histopathological and immunological evaluation

Scabies is considered one of the commonest dermatological diseases that has a global health burden. Current treatment with ivermectin (IVM) is insufficient and potential drug resistance was noticed. Moxidectin (MOX), with a better pharmacological profile may be a promising alternative. The efficacy of moxidectin against Sarcoptes scabiei was assessed both in vitro and in vivo in comparison with ivermectin. For the in vitro assay, both drugs were used in two concentrations (50 μg/ml and 100 μg/ml). For the in vivo assay, twenty rabbits infected with Sarcoptes scabiei were divided into three groups: untreated, moxidectin-treated and ivermectin-treated with the same dose of 0.3 mg/kg once. Another four rabbits were used as a normal control non-infected group. Treatment efficacy was evaluated by clinical assessment, parasitological evaluation and histopathological examination of skin samples using Hematoxylin and eosin and toluidine blue for mast cell staining. Immune response was also assessed by immunohistochemical staining of CD3 T cells in skin samples. Our results showed that moxidectin had a high efficacy (100%) in killing mites when used in both concentrations (50 μg/ml, 100 μg/ml) in the in vitro assay. Concerning the in vivo assay, on day 14 post-treatment, all MOX-treated rabbits were mite-free with full clinical cure by the end of the study (D21) showing (100%) reduction of mites count. Also, marked improvement in the epidermis with absence of mites in skin samples were shown. Poor clinical and parasitological improvements were noted in the ivermectin-treated rabbits, when given as a single dose with a percentage reduction (60.67%) in the 2nd week and progressive increase in lesions and mites count in the 3rd week post-treatment. Regarding the immune response, MOX-treated group showed mild infiltration with both mast cells and CD3 T cells in comparison to severe infiltration with both types of cells in the untreated and IVM-treated group. On conclusion, our results demonstrated that a single dose of MOX was more effective than IVM, supporting MOX as a valuable therapeutic approach for scabies therapy.

Treatment of Sarcoptic mange infestation in rabbits with long acting injectable ivermectin

Sarcoptic mange infestation is one of the major constrains in commercial rabbit rearing due to their ability to produce negative impact on the growth rates and feed conversion efficiency. Ten adult rabbits presented with the history of anorexia, pruritis and crusty lesion in ear, face and legs were selected for the study. Skin scraping examination revealed presence of Sarcoptes scabiei. The subcutaneous administration of single dose long acting injectable Ivermectin (3.15% w/v) formulation at a dose rate of 700 mcg/kg body weight was found to be safe, effective and less time consuming for the management of Sarcoptic mange in naturally infested rabbits. The skin scrapings collected from all the rabbits under study on days 14 and 28 were negative on both instances indicating rapid elimination of S. scabiei with a single dose of long acting ivermectin. No relapse of infestation was observed in any of the rabbits under treatment during the 6 month observation period following the treatment.

Xenointoxication of a Rabbit for the Control of the Common Bed Bug Cimex lectularius L. Using Ivermectin

Human bed bug infestations have undergone a recent global resurgence. The human antiparasitic drug ivermectin has been proposed as a strategy to help control bed bug infestations, but in vivo data are lacking. We allowed separate populations of the common bed bug, Cimex lectularius L., to feed once on a rabbit before and after it was injected subcutaneously with 0.3 mg/kg of ivermectin, and bed bug morbidity and mortality were recorded. Ivermectin levels in the rabbit were measured using high-performance liquid chromatography and mass spectroscopy. Ivermectin blood levels of ∼2 ng/mL caused reductions in bed bug fecundity, and levels of >8 ng/mL caused bed bug death and long-term morbidity including reductions in refeeding, mobility, reproduction, and molting. Gut bacterial cultures from the fed bed bugs showed that ivermectin altered the bed bug gut microbiome.

Moxidectin and the avermectins: Consanguinity but not identity

The avermectins and milbemycins contain a common macrocyclic lactone (ML) ring, but are fermentation products of different organisms. The principal structural difference is that avermectins have sugar groups at C13 of the macrocyclic ring, whereas the milbemycins are protonated at C13. Moxidectin (MOX), belonging to the milbemycin family, has other differences, including a methoxime at C23. The avermectins and MOX have broad-spectrum activity against nematodes and arthropods. They have similar but not identical, spectral ranges of activity and some avermectins and MOX have diverse formulations for great user flexibility. The longer half-life of MOX and its safety profile, allow MOX to be used in long-acting formulations. Some important differences between MOX and avermectins in interaction with various invertebrate ligand-gated ion channels are known and could be the basis of different efficacy and safety profiles. Modelling of IVM interaction with glutamate-gated ion channels suggest different interactions will occur with MOX. Similarly, profound differences between MOX and the avermectins are seen in interactions with ABC transporters in mammals and nematodes. These differences are important for pharmacokinetics, toxicity in animals with defective transporter expression, and probable mechanisms of resistance. Resistance to the avermectins has become widespread in parasites of some hosts and MOX resistance also exists and is increasing. There is some degree of cross-resistance between the avermectins and MOX, but avermectin resistance and MOX resistance are not identical. In many cases when resistance to avermectins is noticed, MOX produces a higher efficacy and quite often is fully effective at recommended dose rates. These similarities and differences should be appreciated for optimal decisions about parasite control, delaying, managing or reversing resistances, and also for appropriate anthelmintic combination.