High intensity of Tunga penetrans infection causing severe disease among pigs in Busoga, South Eastern Uganda.

BACKGROUND: Towards the improvement of stakeholders' awareness of animal tungiasis, we report 10 unusual severe clinical cases of pig tungiasis which were associated with very high infection intensities of T. penetrans in an endemic area. RESULTS: Morbidity of ten pigs with high sand flea intensities detected during high transmission seasons in an endemic area in Busoga sub region, Uganda is described in detail. The cases of pigs presented with a very high number of embedded sand fleas (median = 276, range = 141-838). Acute manifestations due to severe tungiasis included ulcerations (n = 10), abscess formation (n = 6) and lameness (n = 9). Chronic morphopathological presentations were overgrowth of claws (n = 5), lateral deviation of dew claws (n = 6), detachment (n = 5) or loss of dew claws (n = 1). Treatment of severe cases with a topical insecticidal aerosol containing chlorfenvinphos, dichlorvos and gentian violet resolved acute morbidity and facilitated healing by re-epithelialisation. CONCLUSIONS: The presentations of tungiasis highlighted in this report show that high intensities of embedded T. penetrans can cause a severe clinical disease in pigs. Effective tungiasis preventive measures and early diagnosis for treatment could be crucial to minimize its effects on animal health.

Captures of Wild Ceratitis capitata, Bactrocera dorsalis, and Bactrocera cucurbitae (Diptera: Tephritidae) in Traps with Improved Multilure TMR Dispensers Weathered in California.

During 2012­2013, solid Mallet TMR (trimedlure [TML], methyl eugenol [ME], raspberry ketone [RK]) wafers impregnated with DDVP (2, 2-dichlorovinyl dimethyl phosphate) insecticide were weathered during summer (8 wk) and winter (12 wk) in five California citrus-growing counties (Kern, Ventura, Orange, Tulare, and Riverside). In addition, TMR wafers without DDVP and with a Hercon Vaportape II insecticidal strip were compared with TMR dispensers with DDVP at Exeter and Riverside. Weathered treatments were shipped every week (overnight delivery) to Hawaii and frozen for a later bioassay in a 1,335-ha coffee plantation near Numila, Kauai Island, HI, where Mediterranean fruit fly, Ceratitis capitata (Wiedemann), oriental fruit fly, Bactrocera dorsalis Hendel, and melon fly, Bactrocera cucurbitae Coquillett, were all present. We compared trap captures of the three species, C. capitata, B. dorsalis, and B. cucurbitae, for the five different weathering locations. Captures of C. capitata, B. dorsalis, and B. cucurbitae with Mallet TMR dispensers (with DDVP) were not significantly different for the five locations. Captures with the Mallet TMR dispenser without DDVP and Vaportape were similar to those for Mallet TMR with DDVP, although there were some slight location differences. In conclusion, based on these results, the Mallet TMR dispenser could potentially be used in California habitats where large numbers of detection traps are currently deployed. Use of Vaportape with dispensers would not require them to be registered with US Environmental Protection Agency (EPA). Dispensers for use as Male Annihilation Technique (MAT) devices will be tested further in Hawaii.

Sub-chronic exposure to arsenic and dichlorvos on erythrocyte antioxidant defense systems and lipid peroxidation in rats.

The effect of combined exposure to arsenic (25 ppm in drinking water) and dichlorvos (2.5 mg kg1, orally) for 56 days on biochemical variables, indicative of lipid peroxidation, antioxidant enzyme system and AChE activity in erythrocytes of rats, were examined. While arsenic caused a significant increase in AChE, DDVP produced marked depletion. Combined exposure to arsenic and DDVP produced no additional decrease in AChE activity, which was comparable to DDVP. Arsenic and DDVP also increased the levels of reactive oxygen species (ROS) and thiobarbituric acid reactive substances (TBARS), suggesting free radical generation. Interestingly, glutathione linked enzymes (GSH, GPx, GST and GR) significantly increased on arsenic and DDVP exposure. SOD activity also increased significantly in the individually exposed groups, while catalase activity remained unchanged. Blood arsenic level increased significantly on coexposure to arsenic alone and with DDVP exposed group. However, arsenic content in co-exposed group depleted marginally as compared to arsenic alone group, indicating possible arsenic redistribution. It might be concluded from the study that the combined exposure to arsenic and DDVP may lead to synergistic effects on certain biochemical indicators of oxidative stress like ROS, GSH and SOD, suggesting a more pronounced induction of lipid peroxidation in erythrocytes.

Joint toxicity assessment reveals synergistic effect of chlorpyrifos and dichlorvos to common carp (Cyprinus carpio).

Common carp (Cyprinus carpio) is an important aquaculture species. However, their production and health is sometimes threatened by pesticides. In common carp, extensive studies have been done for exposures of single pesticides, but effects of mixtures such as those of the commonly used chlorpyrifos and dichlorvos, are still unknown for this species. In the first phase of this work, an acute lethal exposure experiment was conducted to estimate 24 h to 96 h lethal concentrations (LC10-90) of chlorpyrifos, dichlorvos and their mixture. Compared to dichlorvos, chlorpyrifos was found to be highly toxic to the tested species. Joint toxicity assessment of these pesticides in binary mixtures was dominated by synergism. In the second experimental phase, common carp were exposed to sub-lethal concentrations (LD-10% and HD-50% 96 h-LC50) of individual pesticides and their mixture. General fish behaviors, buccal movements and feeding attempts by fish were recorded after 1 h, 24 h, 48 h, 72 h and 96 h whereas aerobic metabolism of fish was recorded for 0-24 h, 24-48 h 48-72 h and 72-96 h of exposure. All pesticide treatments elevated buccal movements and oxygen uptake in a dose dependent manner. Feeding depression was also observed by pesticide exposure. The augmented deleterious effect of these pesticides in a mixture suggests that joint toxicity assessment is critical to develop more realistic water quality standards and monitoring guidelines.

Effect of short-term exposure to dichlorvos on synaptic plasticity of rat hippocampal slices: involvement of acylpeptide hydrolase and alpha(7) nicotinic receptors.

Dichlorvos is the active molecule of the pro-drug metrifonate used to revert the cognitive deficits associated with Alzheimer's disease. A few years ago it was reported that dichlorvos inhibits the enzyme acylpeptide hydrolase at lower doses than those necessary to inhibit acetylcholinesterase to the same extent. Therefore, the aim of our investigation was to test the hypothesis that dichlorvos can enhance synaptic efficacy through a mechanism that involves acylpeptide hydrolase instead of acetylcholinesterase inhibition. We used long-term potentiation induced in rat hippocampal slices as a model of synaptic plasticity. Our results indicate that short-term exposures (20 min) to 50 microM dichlorvos enhance long-term potentiation in about 200% compared to the control condition. This effect is correlated with approximately 60% inhibition of acylpeptide hydrolase activity, whereas acetylcholinesterase activity remains unaffected. Paired-pulse facilitation and inhibition experiments indicate that dichlorvos does not have any presynaptic effect in the CA3-->CA1 pathway nor affect gabaergic interneurons. Interestingly, the application of 100 nM methyllicaconitine, an alpha(7) nicotinic receptor antagonist, blocked the enhancing effect of dichlorvos on long-term potentiation. These results indicate that under the exposure conditions described above, dichlorvos enhances long-term potentiation through a postsynaptic mechanism that involves (a) the inhibition of the enzyme acylpeptide hydrolase and (b) the modulation of alpha(7) nicotinic receptors.

Impaired mitochondrial functions in organophosphate induced delayed neuropathy in rats.

Acute exposure to organophosphates induces a delayed neurodegenerative condition known as organophosphate-induced delayed neuropathy (OPIDN). The mechanism of OPIDN has not been fully understood as it does not involve cholinergic crisis. The present study has been designed to evaluate the role of mitochondrial dysfunctions in the development of OPIDN. OPIDN was induced in rats by administering acute dose of monocrotophos (MCP, 20 mg/kg body weight, orally) or dichlorvos (DDVP, 200 mg/kg body weight, subcutaneously), 15-20 min after treatment with antidotes [atropine (20 mg/kg body weight) and 2-PAM (100 mg/kg body weight) intraperitoneally]. MDA levels were observed to be higher and thiol content was lower in mitochondria from brain regions of OP exposed animals. This was accompanied by decreased activities of the mitochondrial enzymes; NADH dehydrogenase, succinate dehydrogenase, and cytochrome oxidase. In addition, mitochondrial functions assessed by MTT reduction also confirmed mitochondrial dysfunctions following development of OPIDN. The spatial long-term memory evaluated using elevated plus-maze test was observed to be deficit in OPIDN. The results suggest impaired mitochondrial functions as a mechanism involved in the development of organophosphate induced delayed neuropathy.

Temporal changes in distribution, prevalence and intensity of northern fowl mite (Ornithonyssus sylviarum) parasitism in commercial caged laying hens, with a comprehensive economic analysis of parasite impact.

Establishment and spread of Ornithonyssus sylviarum were documented through time on sentinel hens (50 per house of 28,000-30,000 hens) in the first egg production cycle of three large commercial flocks (12 houses) of white leghorn hens. Mites were controlled using acaricide, and the impacts of treatment on mite populations and economic performance were documented. Mite prevalence and intensity increased rapidly and in tandem for 4-8 weeks after infestation. Intensity declined due to immune system involvement, but prevalence remained high, and this would affect mite sampling plan use and development. Early treatment was more effective at controlling mites; 85% of light infestations were eliminated by a pesticide spray (Ravap), versus 24% of heavy infestations. Hens infested later developed lower peak mite intensities, and those mite populations declined more quickly than on hens infested earlier in life. Raw spatial association by distance indices (SADIE), incorporating both the intensity and distribution of mites within a house, were high from week-to-week within a hen house. Once adjusted spatially to reflect variable hen cohorts becoming infested asynchronously, this analysis showed the association index tended to rebound at intervals of 5-6 weeks after the hen immune system first suppressed them. Large, consistent mite differences in one flock (high vs. low infestation levels) showed the economic damage of mite parasitism (assessed by flock indexing) was very high in the initial stages of mite expansion. Unmitigated infestations overall reduced egg production (2.1-4.0%), individual egg weights (0.5-2.2%), and feed conversion efficiency (5.7%), causing a profit reduction of $0.07-0.10 per hen for a 10-week period. Asynchronous infestation patterns among pesticide-treated hens may have contributed to a lack of apparent flock-level economic effects later in the production cycle. Individual egg weights differed with mite loads periodically, but could be either higher or lower, depending on circumstances and interactions with hen weight. Individual hen weight gains were depressed by high/moderate mite loads, but the heavier hens in a flock harbored more mites. This led to compensatory weight gains after mites declined. Tradeoffs between resource allocation to body growth or production versus immune system function appeared to be operating during the early and most damaging mite infestation period, when high egg production was beginning and the hens were gaining weight. The results were related to other studies of mite impact on domestic hens and to wild bird-ectoparasite studies. Much of the mite economic damage probably is due to engaging and maintaining the immune response.

Hematotoxic and hepatotoxic effects of dichlorvos at sublethal dosages in rats.

The present study was designed to understand the effects of sublethal concentrations of dichlorvos (DIC) on hematological constituent [red blood corpuscles, white blood corpuscles (WBC), mean cell volume, mean corpuscular hemoglobin, mean corpuscular hemoglobin concentration, platelet counts, hemoglobin and hematocrite levels] and serum damage marker enzymes (aspartate aminotransferase, alanin aminotransferase, alkaline phosphatase, and lactate dehydrogenase) in rats at subacute period under laboratory conditions. DIC at dosages of 5 and 10 ppm was administered orally to six male rats ad libitum during the tests for 4 weeks consecutively. According to the results, DIC treatments increased significantly the levels of serum marker enzyme activities, whereas they did not change hematologic constituent except for WBC number treated with both dosages of DIC. The observations presented led us to conclude that the administrations of subacute DIC induced the levels of damage marker enzymes and leukocytosis.

Acute toxicity of Nuvan, an organophosphate to freshwater fish Ctenopharyngodon idella and its effect on oxygen consumption.

The acute toxicity of Nuvan to the grass carp Ctenopharyngodon idella was determined using static and continuous flow through system for 24, 48, 72 and 96 hr. The median lethal concentration (LC50) values were 13.1, 10.9, 9.8 and 6.5 mg l(-1) respectively in static system and 10.7, 9.5, 8.0 and 7.5 mg l(-1) respectively in continuous flow through system. A reduction in oxygen consumption is observed when the fish is exposed to the toxicant and the mortality is due to effect of metabolism of energy synthesis.

Study of the principles in the first phase of experimental pharmacology: the basic step with assumption hypothesis.

BACKGROUND: Experimental pharmacology deals with effects of various test substances studied on different animal species which is aimed at finding out safe therapeutic agent suitable for public health as well as mechanism and site of action of a test substance. It is the basic step in the discovery of new drugs or studying the pharmacological actions of already developed one using both preclinical and clinical study designs in a stepwise phase of investigations. However, the investigations in the first phase of experimental pharmacology are usually concluded with assumption hypothesis without any adequate validation of the scientific evidence. Single dose acute toxicology had been conducted on Balb c mice with three different level of doses prepared from each of three different test chemicals (Dichlorvos, Chlorpyrifos and Cypermethrin) with known median lethal dose (LD50) to define the fundamental principles, cause of toxicity and investigation timeframe in the first phase of experimental pharmacology. METHODS: The methods used for data collection were: procurement of test chemicals, investigation of single dose acute toxicity on Balb c mice and quantitative immunoglobulins test. Data was thematically compiled for validation of the findings from each of the sources. RESULTS: The result showed that the dose had never limited the toxic property of tested chemicals but the magnitude of adverse effect and length of time at which adverse effect was manifested on treated Balb c mice. The toxicity of tested chemicals was however limited by the toxic reaction rate of a dose in the biological process of exposed Balb c mice. The toxic effect of tested chemicals became magnified within a short period of time when large amount administered orally. It also remained after a long period of time when small amount administered in the same route. CONCLUSION: Adequate investigation time for acute toxicity study was therefore essential for comprehensive analysis of pharmacological property of tested chemicals at different level of doses.

Organophosphate pesticide trichlorfon induced neurotoxic effects in freshwater silver catfish Rhamdia quelen via disruption of blood-brain barrier: Implications on oxidative status, cell viability and brain neurotransmitters.

The aim of this study was to evaluate whether rupture on blood-brain barrier (BBB) can be a pathway for trichlorfon-induced neurotoxic effects, and to investigate its implications on oxidative status, cell viability and brain neurotransmitters in silver catfish (Rhamdia quelen). The BBB permeability was increased in fish exposed for 24 h to 22 mg/L of trichlorfon compared to the control group, as well as in those exposed to 11 and 22 mg/L of trichlorfon for 48 h. Compared to the control group, brain reactive oxygen species and lipid peroxide levels were higher when exposed to 22 mg/L of trichlorfon and 11 and 22 mg/L of trichlorfon after 24 h and 48 h, respectively, while the antioxidant capacity against peroxyl radical levels was lower. Exposure to 22 mg/L of trichlorfon for 24 h reduced brain cell viability compared to the control group, together with 11 and 22 mg/L of trichlorfon for 48 h. Also, brain AChE, Na+ and K+-ATPase activities were reduced in those fish exposed to trichlorfon compared to the control group. Thus, the rupture of BBB can be considered an important pathway involved in trichlorfon-induced neurotoxic effects, which contributes to brain oxidative damage and important changes on brain neurotransmitters.

Acute toxic effects of inhaled dichlorvos vapor on respiratory mechanics and blood cholinesterase activity in guinea pigs.

Using a modified noninvasive volume-displacement plethysmography system, we investigated the effects of inhaled dichlorvos (2,2-dimethyl-dichlorovinyl phosphate, or DDVP) vapor on the respiratory mechanics and blood cholinesterase activity of guinea pigs. Data revealed significant dose-dependent changes in several pulmonary parameters. Animals exposed to a DDVP concentration of 35 mg/m(3) did not show any significant changes in frequency, tidal volume, or minute ventilation. However, animals exposed to 55 mg/m(3) DDVP showed significantly decreased respiratory frequency and significantly increased tidal volume with no significant changes in minute ventilation. Similarly, animals exposed to 75 mg/m(3) DDVP showed significantly decreased respiratory frequency along with significantly increased tidal volume. The decreased respiratory frequency was large enough in the high exposure group to offset the increased tidal volume. This effect resulted in significantly decreased minute ventilation by the end of exposure, which remained attenuated 10 min after exposure. An analysis of whole-blood cholinesterase activity revealed significantly decreased activity for both acetylcholinesterase (AChE) and butyl-cholinesterase (BChE). Peak inhibition occurred for both enzymes at the end of exposure for all three concentrations and rapidly recovered within several minutes of exposure. Analysis of blood samples using gas chromatography-mass spectroscopy (GC-MS) revealed that minute ventilation may only play a minimal role in the dosimetry of inhaled DDVP vapor.

Suicide attempt with injection of insecticide in both wrists.

Organophosphates that are commonly used in agriculture, houses, gardens, and in veterinary medicine worldwide, may be used for suicidal purposes. But suicide attempt with self-injection of organophosphates is rare. This article presents a case of a suicide attempt of a young man with self-injection of an organophosphate insecticide (dichlorvos) to both his wrists.

Cromakalim, a Potassium Channel Opener, Ameliorates the Organophosphate and Carbamate-Induced Seizure in Mice.

Organophosphates (OPs) and carbamates are acetylcholine esterase inhibitors (AChEIs), which can cause seizure and lethality. Anticonvulsant properties of potassium channel openers including cromakalim have been determined in previous studies. In the present experiment, the possible effect of cromakalim on the convulsion and death induced by OPs and carbamates was studied in mice. Dichlorvos (an OP, 50 mg/kg) and physostigmine (a carbamate, 2 mg/kg) were used to induce seizure in animals. Cromakalim at doses of 0.1, 10, and 30 µg/kg was injected 30 min before dichlorvos and physostigmine, and 5 min before glibenclamide (a potassium channel blocker, 1 mg/kg) administration. All injections were performed intraperitoneally. After drugs administration, the onset of convulsion, death, the severity of seizure, and rate of mortality were investigated. Results revealed that both dichlorvos and physostigmine induced seizure activity and lethality in 100% of the animals. Cromakalim at doses of 0.1, 10, and 30 µg/kg significantly increased the latency of both seizure and death (P<0.05). Also, cromakalim decreased the mortality rate induced by dichlorvos and physostigmine (P<0.05). On the other hand, glibenclamide blocked all aspects of the anticonvulsant effect of cromakalim (P<0.05). This study revealed for the first time that cromakalim (a KATP channel opener) diminishes the seizure and death induced by dichlorvos and physostigmine in mice, and introduces a new aspect to manage the patients who suffer from OPs/carbamates-induced seizure.

Polyphenol-Rich Fraction of Parquetina nigrescens Mitigates Dichlorvos-Induced Cardiorenal Dysfunction Through Reduction in Cardiac Nitrotyrosine and Renal p38 Expressions in Wistar Rats.

Parquetina nigrescens is commonly used to treat diseases in humans and animals in developing countries, including Nigeria. This study evaluates the effects of its polyphenol-rich fraction (prf) on dichlorvos-induced cardio- and renal toxicity. There were several factors assessed during this study, including cardiac and renal markers, serum myeloperoxidase and xanthine oxidase, and electrocardiograph (ECG) changes. The changes in electrocardiograph (ECG) were recorded. Immunohistochemistry of cardiac and renal p38 and nitrotyrosine was determined. Dichlorvos exposure caused a significant decrease in L-glutathione (reduced glutathione) and other antioxidant enzymes with increases in malondialdehyde, myeloperoxidase, advanced oxidation protein products, and protein carbonyl levels. It also brought about alterations in microanatomy of the heart and kidneys accompanied by increases in serum creatinine and urea levels. Exposure to dichlorvos induced prolonged QRS interval and shortened QT durations in rats. Immunohistochemistry revealed lower expressions of cardiac nitrotyrosine and renal p38 (mitogen-activated protein kinase; MAPK) in rats treated with prf of P. nigrescens. Combining all, prf of P. nigrescens demonstrated antioxidant as well as protective properties in the heart and kidneys of rats exposed to dichlorvos. It ameliorated dichlorvos-induced cardio- and nephrotoxicity giving credence to its use in ethnomedicine.

Adverse effect of organophosphate compounds, dichlorvos and chlorpyrifos in the reproductive tissues of transgenic Drosophila melanogaster: 70kDa heat shock protein as a marker of cellular damage.

The study highlights the adverse effects of organophosphate compounds dichlorvos and chlorpyrifos on reproduction in Drosophila. Freshly eclosed first instar larvae of Drosophila melanogaster transgenic for hsp70 (hsp70-lacZ) Bg(9) were fed on 0.015-150.0ppb dichlorvos and chlorpyrifos mixed food. Virgin flies eclosing from the normal and contaminated food were pair-mated to examine the effect of the test chemicals on reproduction of the exposed organisms. Expression of hsp70, sex peptide (SP or Acp70A), accessory gland protein (Acp36DE) and tissue damage was examined in reproductive organs of adult fly. Exposed organisms exhibited a dose-dependent significantly reduced reproductive outcome and males were found to be more sensitive than females. Hsp70 expression was restricted only within the testis lobes of male fly while it was not induced in the ovary of the female. In concurrence with absence of hsp70 expression in the accessory glands of male fly, tissue damage was evident in them. Acp70A and Acp36DE expression were found to be significantly downregulated at the higher concentrations of the test chemicals. The study suggests that (i) dichlorvos is more deleterious to fly reproduction compared to chlorpyrifos with an adverse effect on Acp70A and Acp36DE expression required to facilitate normal reproduction; (ii) hsp70 may be used as a marker of cellular damage against dichlorvos and chlorpyrifos in Drosophila.

Endometrial damage and apoptosis in rats induced by dichlorvos and ameliorating effect of antioxidant vitamins E and C.

We aimed to investigate the effect of subchronic administration of dichlorvos (DDVP) on endometrium and to evaluate ameliorating effects of a combination of Vitamins E and C against DDVP toxicity in the rat. Three groups of rats were used in the experiment. The first group was treated with 4 mg/kg DDVP; the second group was treated with 4 mg/kg body weight DDVP plus Vitamins E and C (DDVP+Vit); the third group was given only corn oil (control). DDVP and DDVP+Vit groups were given DDVP by gavage 5 days a week for 4 weeks at a dose level of 4 mg/kg day by using corn oil as the vechicle. Vitamins E and C were injected at doses of 50 mg/kg i.m. and 20 mg/kg body weight i.p. Histopathological and immunohistochemical examinations for caspase-3 and caspase-9 were accomplished in the endometrium. The level of malondialdehyde (MDA) increased significantly in the DDVP group compared with the control group (p<0.05). MDA significantly decreased in the DDVP+Vit group compared with the DDVP group (p<0.05). Administration of Vitamins E and C along with DDVP significantly reduced the histopathological changes and the extent of apoptosis. In conclusion, subchronic DDVP administration caused endometrial damage and that treatment with a combination of Vitamins E and C reduced endometrial damage caused by DDVP.

Efficacy of trimedoxime in mice poisoned with dichlorvos, heptenophos or monocrotophos.

The aim of the study was to examine antidotal potency of trimedoxime in mice poisoned with three direct dimethoxy-substituted organophosphorus inhibitors. In order to assess the protective efficacy of trimedoxime against dichlorvos, heptenophos or monocrotophos, median effective doses and efficacy half-times were calculated. Trimedoxime (24 mg/kg intravenously) was injected 5 min. before 1.3 LD50 intravenously of poisons. Activities of brain, diaphragmal and erythrocyte acetylcholinesterase, as well as of plasma carboxylesterases were determined at different time intervals (10, 40 and 60 min.) after administration of the antidotes. Protective effect of trimedoxime decreased according to the following order: monocrotophos > heptenophos > dichlorvos. Administration of the oxime produced a significant reactivation of central and peripheral acetylcholinesterase inhibited with dichlorvos and heptenophos, with the exception of erythrocyte acetylcholinesterase inhibited by heptenophos. Surprisingly, trimedoxime did not induce reactivation of monocrotophos-inhibited acetylcholinesterase in any of the tissues tested. These organophosphorus compounds produced a significant inhibition of plasma carboxylesterase activity, while administration of trimedoxime led to regeneration of the enzyme activity. The same dose of trimedoxime assured survival of experimental animals poisoned by all three organophosphorus compounds, although the biochemical findings were quite different.

Detoxification of Organophosphate Poisoning Using Nanoparticle Bioscavengers.

Organophosphate poisoning is highly lethal as organophosphates, which are commonly found in insecticides and nerve agents, cause irreversible phosphorylation and inactivation of acetylcholinesterase (AChE), leading to neuromuscular disorders via accumulation of acetylcholine in the body. Direct interception of organophosphates in the systemic circulation thus provides a desirable strategy in treatment of the condition. Inspired by the presence of AChE on red blood cell (RBC) membranes, we explored a biomimetic nanoparticle consisting of a polymeric core surrounded by RBC membranes to serve as an anti-organophosphate agent. Through in vitro studies, we demonstrated that the biomimetic nanoparticles retain the enzymatic activity of membrane-bound AChE and are able to bind to a model organophosphate, dichlorvos, precluding its inhibitory effect on other enzymatic substrates. In a mouse model of organophosphate poisoning, the nanoparticles were shown to improve the AChE activity in the blood and markedly improved the survival of dichlorvos-challenged mice.

A comparison of three different methodologies for evaluating Rhipicephalus (Boophilus) microplus susceptibility to topical spray compounds.

This study aimed to compare three different methodologies (Adult Immersion Tests, field trials with naturally infected animals, and a Stall Test using artificially infested cattle) to evaluate the efficacy of two topical formulations that we administered as whole body sprays (15% Cypermethrin+30% Chlorpyriphos+15% Fenthion-Colosso(®) FC 30, Ouro Fino Agronegócios; and 60% Dichlorvos+20% Chlorpyriphos-Ectofós(®), Vallée Saúde Animal Ltd.), against a susceptible strain of Rhipicephalus (Boophilus) microplus. To achieve this objective, two natural infestation trials were conducted, as well as two artificial infestation trials (Stall Tests) and two Adult Immersion Tests (AIT). The AIT results showed that both spray formulations achieved 100% efficacy against R. (B.) microplus fully engorged females. However, when observing results obtained by field trials (natural infestations) and Stall Tests, none of these topically applied compounds reached 100% efficacy or affected the reproductive capacity of the fully engorged female ticks. Additional studies must be conducted to compare these in vivo methodologies with different in vitro techniques, such as the Larval Packet Test. However, based on results obtained here, we can conclude that depending on the spray formulations used, the AIT can overestimate acaricidal efficacy and values of reproductive efficiency of such compounds against R (B.) microplus. Specifically, when dealing with spray formulations in the Stall Tests, the period of residual action can increase because these animals are sheltered from contact with environmental factors that might interfere with the efficacy of the products tested. It may be necessary to take in vivo trial results into consideration (such as field trials with naturally infested animals or Stall Tests) to standardize a specific in vitro assay, such as the Adult Immersion Test.