Variation of diazinon and amitraz susceptibility of Hyalomma marginatum (Acari: Ixodidae) in the Rabat-Sale-Kenitra region of Morocco

In the present study, the acaricide susceptibility status of Hyalomma marginatum in Morocco was investigated in the Rabat-Sale-Kenitra region using the Larval Packet Test. The overall LC₅₀ value for diazinon and amitraz was 115 ppm (95% CI: [104; 125]) and 22 ppm (95% CI: [21; 23]), respectively. The LC₅₀ values varied significantly between the nine sampled locations (P<0.001) ranging from 75 ppm (95% CI: [65; 84]) in Ouelmes to 179 ppm (95% CI: [139; 201]) in Jorf El Melha for diazinon and from 18 ppm (95% CI: [15; 21]) in Skhirat to 28 ppm (95% CI: [24; 31]) in Ouelmes for amitraz. Sequencing of the target-site of diazinon, acetylcholinesterase 1 (AChE1), indicated that previously reported resistance mutations in AChE1 were absent in ticks from Jorf El Melha surviving 500 ppm diazinon. This study is the first report on the H. marginatum susceptibilty status to the most frequently used acaricides in Morocco and indicates that acaricide tick resistance is emerging.

Acaricide resistance status and identification of resistance mutations in populations of the two-spotted spider mite Tetranychus urticae from Ethiopia

The intensive use of pesticides is a common practice for the management of the two-spotted spider mite, Tetranychus urticae, in greenhouses and field farms of Ethiopia. However, incidence of resistance and possible resistance mechanisms in T. urticae populations from Ethiopia have not yet been studied. Here, we assessed the toxicity of various acaricides-bifenazate, abamectin, emamectin benzoate, profenofos, fenbutatin oxide, fenpyroximate, amitraz and chlorfenapyr-on T. urticae populations sampled from six flower greenhouse farms, three strawberry greenhouse farms, one field-grown vegetable farm and two wild populations. In parallel, all populations were screened for known target-site mutations. All tested populations were fully susceptible to bifenazate, abamectin, emamectin benzoate and profenofos, but resistant against fenbutatin oxide and fenpyroximate. Four populations showed considerable levels of resistance against amitraz and one population was resistant to chlorfenapyr. Several target-site mutations were identified in the tested populations, including G119S, A201S, T280A, G328A and F331W/C/Y in acetylcholinesterase and the F1538I and L1024V mutation in the voltage-gated sodium channel. The F1538I mutation was found in eight out of 12 populations, whereas the L1024V mutation was only found in two populations. The H92R mutation in the PSST subunit of complex I and the I1017F mutation in chitin synthase 1 was detected in half of the tested populations. The G326E and I321T mutations in the glutamate-gated chloride channel 3 were also detected, but more rarely, whereas mitochondrial cytochrome b mutations were not detected. The current study revealed multiple resistance patterns in Ethiopian T. urticae populations and together with the wide presence of target-site mutations, calls for the wise use of acaricides in the management of T. urticae in Ethiopia.

Methylation of selected CpG islands involved in the transcription of myeloperoxidase and superoxide dismutase 2 in neutrophils of periparturient and mid-lactation cows

It is generally accepted that intracellular killing of microorganisms by production of reactive oxygen species (ROS) in the phagosome of the neutrophil is an important arm of innate defense. High-producing dairy cows are prone to periparturient metabolic and infectious diseases. Both myeloperoxidase (MPO) activity and ROS production decrease the day of parturition. Several studies have demonstrated changes in the expression of genes involved in, for example, metabolism and defense in the circulating neutrophil during peripartum. In this study, we wanted to further characterize the periparturient neutrophil in terms of its oxidative killing capacity by analyzing the oxidative burst at 3 levels. First, the ROS phenotype was evaluated using chemiluminescence. The cows (sampled within 24 h after parturition and at 135 d in milk) showed a significantly slower production of ROS at parturition. Both primiparous (n = 13) and multiparous (n = 12) cows were included in this study, but parity did not affect the kinetics of ROS production. Second, the expression of 11 genes involved in ROS production was measured in the same cows: cytochrome b-245 α and β chain (CYBA, CYBB; coding for membrane-bound constituents of NADPH oxidase); neutrophil cytosolic factors 1, 2, and 4 (NCF1, NCF2, and NCF4); Rac family small GTPase 1 and 2 (RAC1 and RAC2; coding for regulatory proteins of NADPH oxidase); superoxide dismutase 2 (SOD2); catalase (CAT); myeloperoxidase (MPO; coding for enzymes involved in metabolizing downstream ROS); and spleen-associated tyrosine kinase (SYK; involved in signaling). During peripartum, a shift in expression in the oxidative killing pathway was observed, characterized by a downregulation of MPO and a simultaneous upregulation of the genes coding for NADPH oxidase. Third, as total DNA methylation is known to change during pregnancy, we investigated whether the observed differences were due to different methylation patterns. Promotor regions initiate transcription of particular genes; therefore, we analyzed the methylation status in annotated CpG islands of MPO and SOD2, 2 genes with a significant difference in expression between both lactation stages. The differences in methylation of these CpG islands were nonsignificant. High-throughput techniques may be necessary to obtain more detailed information on the total DNA methylation dynamics in bovine neutrophils and increase our understanding of how gene expression is controlled in neutrophils.

Distinct neutrophil C5a receptor inflammatory events in cows initiated by chemoattractant C5a and lipopolysaccharide around parturition and in mid lactation

In neutrophils, toll-like receptor and complement component 5a (C5a) signaling are critical pathways regulating innate immunity. In cows, not much is known about the second C5a receptor, complement component 5a receptor 2 (C5AR2). It is an interesting player in sepsis treatment because it is considered to have an anti-inflammatory effect during normal inflammation. Periparturient cows are prone to severe infections, and the objectives of this study were to investigate the expression and functionality of C5AR2 during peripartum. We investigated the effect of 2 major inflammatory stimuli, C5a and lipopolysaccharide (LPS), on the expression of a selected number of genes (C5AR1, C5AR2, TLR4, ITGAM, COX2, and CXCL8) and functions linked to these receptors. Overall, TLR4, ITGAM, and C5AR2, all of which are involved in early inflammation, showed a lower expression in periparturient cows. However, an overall lower expression seems not to be the only explanation for the increased risk of sepsis in periparturient cows. Normally, in response to inflammation and as seen in the mid-lactation group, the expression of these genes increases after stimulation with LPS. However, in periparturient cows, stimulation with LPS led to a decrease in expression of these receptors, indicating a different response of neutrophils in response to LPS during this period. A decrease in ITGAM (coding for CD11b) expression complicates correct neutrophil localization and phagocytosis. Its downregulation upon stimulation might be detrimental for adequate eradication of the pathogen and might increase the risk of an imbalanced inflammation; C5AR2 seems to play a central role in this altered response. In addition, myeloperoxidase (MPO) activity in periparturient cows is lower in response to C5a stimulation. It has been suggested that MPO plays an important role in neutrophil shutdown and, thereby, timely resolution of inflammation. A decreased MPO activity might thus prolong the inflammatory reaction of the neutrophils. This finding was supported by the increased viability of the neutrophils obtained from periparturient cows. Even after stimulation, we found a lower caspase-3 activity in this group, indicating that they might be activated for a longer time compared with the neutrophils from mid-lactation cows. Accordingly, these alterations might contribute to a temporal mismatch in inflammatory responses, as often seen in severe periparturient infections.