Larvicidal activity of coumarin derivatives on Toxocara canis larvae, cytotoxicity analysis, and in silico bioavailability studies.

Human toxocariasis is a neglected anthropozoonosis with global distribution. Treatment is based on the administration of anthelmintics; however, their effectiveness at the tissue level is low to moderate, necessitating the discovery of new drug candidates. Several groups of synthetic compounds, including coumarin derivatives, have demonstrated bioactivity against fungi, bacteria, and even parasites, such as Dactylogyrus intermedius, Leishmania major, and Plasmodium falciparum. The aim of this study was to evaluate the effect of ten coumarin-derived compounds against Toxocara canis larvae using in vitro, cytotoxicity, and in silico tests for selecting new drug candidates for preclinical tests aimed at evaluating the treatment of visceral toxocariasis. The compounds were tested in vitro in duplicate at a concentration of 1 mg/mL, and compounds with larvicidal activity were serially diluted to obtain concentrations of 0.5 mg/mL; 0.25 mg/mL; 0.125 mg/mL; and 0.05 mg/mL. The tests were performed in a microculture plate containing 100 T. canis larvae in RPMI-1640 medium. One compound (COU 9) was selected for cytotoxicity analysis using J774.A1 murine macrophages and it was found to be non-cytotoxic at any concentration tested. The in silico analysis was performed using computational models; the compound presented adequate results of oral bioavailability. To confirm the non-viability of the larvae, the contents of the microplate wells of COU 9 were inoculated intraperitoneally (IP) into female Swiss mice at 7-8 weeks of age. This confirmed the larvicidal activity of this compound. These results show that COU 9 exhibited larvicidal activity against T. canis larvae, which, after exposure to the compound, were non-viable, and that COU 9 inhibited infection in a murine model. In addition, COU 9 did not exhibit cytotoxicity and presented adequate bioavailability in silico, similar to albendazole, an anthelmintic, which is the first choice for treatment of human toxocariasis, supporting the potential for future investigations and preclinical tests on COU 9.

Ozone and peroxone disinfection of Toxocara canis eggs in water.

Water pollution in developing countries continues to be a major health problem due to various anthropological activities that contribute to the spread of many parasitic diseases, including those caused by helminths. The aim of this study is to explore the ability of ozone and peroxone to disinfect drinking water contaminated samples with Toxocara canis eggs. The oxidants used were ozone and ozone-hydrogen peroxide combination. The treatment of Toxocara canis eggs was carried out in a 50 ml reactor with an operating volume of 10 ml. The pH conditions (5, 7 and 10) were varied for each treatment. The treatment effect was calculated by counting eggs and examining the condition of the larvae larval condition (whole, broken and hatched larvae) using an optical microscope. The experiment was carried out by exposing the eggs for 60 and 120 minutes to ozone and peroxone. The best results were obtained for helminths treated with the ozone/hydrogen peroxide combination at pH 10, with an inactivation of 79.2%. The synergistic effect of ozone combined with hydrogen peroxide allows higher helminth egg inactivation rates, demonstrating that advanced oxidation processes are a real alternative to apply in the inactivation of Toxocara canis eggs. The results obtained in this study show that the ozone and peroxone treatment could be a useful disinfection process to destroy or inactivate Toxocara canis eggs in processes commonly applied in water treatment.

Synergistic effects of using sodium hypochlorite (bleach) and desiccation in surface inactivation for Toxocara spp.

Toxocara cati and T. canis are parasitic nematodes found in the intestines of cats and dogs respectively, with a cosmopolitan distribution, and the potential for anthropozoonotic transmission, resulting in human toxocariasis. Spread of Toxocara spp. is primarily through the ingestion of embryonated eggs contaminating surfaces or uncooked food, or through the ingestion of a paratenic host containing a third-stage larva. The Toxocara spp. eggshell is composed of a lipid layer providing a permeability barrier, a chitinous layer providing structural strength, and thin vitelline and uterine layers, which combined create a biologically resistant structure, making the Toxocara spp. egg very hardy, and capable of surviving for years in the natural environment. The use of sodium hypochlorite, household bleach, as a disinfectant for Toxocara spp. eggs has been reported, with results varying from ineffective to limited effectiveness depending on parameters including contact time, concentration, and temperature. Desiccation or humidity levels have also been reported to have an impact on larval development and/or survival of Toxocara spp. eggs. However, to date, after a thorough search of the literature, no relevant publications have been found that evaluated the use of sodium hypochlorite and desiccation in combination. These experiments aim to assess the effects of using a combination of desiccation and 10% bleach solution (0.6% sodium hypochlorite) on fertilized or embryonated eggs of T. cati, T. canis, and T. vitulorum. Results of these experiments highlight the synergistic effects of desiccation and bleach, and demonstrate a relatively simple method for surface inactivation, resulting in a decrease in viability or destruction of T. cati, T. canis and T. vitulorum eggs. Implications for these findings may apply to larger scale elimination of ascarid eggs from both research, veterinary, and farming facilities to mitigate transmission.

Anthelmintic activity and chemical profile of native plant extracts from the Yucatan Peninsula against Toxocara canis.

Toxocara canis can produce the "larva migrans" syndrome in humans, and in puppies, it can cause severe digestive disorders. The most used treatments are based on anthelmintics, although there are reports of anthelmintic (AH) resistance. The Yucatan Peninsula has a great variety of plant species whose AH properties are still unknown. The objective of this study was to evaluate the in vitro AH activity of ethanolic (EE), methanolic (ME) and aqueous (AE) extracts from the leaves of five native plant species of the Yucatan Peninsula on T. canis eggs of dogs from Merida, Yucatan. As part of a screening, the EE of the plants Alseis yucatanensis, Calea jamaicensis, Cameraria latifolia, Macrocepis diademata, and Parathesis cubana were evaluated at doses of 2400 and 3600 µg/ml. The EE and AE of A. yucatanensis and M. diademata presented high percentages (≥ 91.3%) of inhibition of the larval development of T. canis after six days of exposure. The lowest LC50 and LC99 was presented by the ME from A. yucatanensis (255.5 and 629.06 µg/ml, respectively) and the ME from M. diademata (222.4 and 636.5 µg/ml, respectively), and the AE from A. yucatanenesis (LC50 of 535.9 µg/ml). Chemical profiling of the most potent AH extract (Alseis yucatanensis) was carried out by LC-UV-HRMS. Data from the ME and AE from this plant indicated the presence of the known glucosylngoumiensine, kaempferol 3,7-diglucosyde, uvaol, linoleic acid and linolenic acid together with unknown alkaloids. The EE, ME and AE from leaves of M. diademata and A. yucatanensis could be developed as natural alternatives to control T. canis.

Natural and Synthetic Naphthoquinones as Potential Anti-Infective Agents.

BACKGROUND: Naphthoquinones are a class of aromatic compounds relevant for their chemical characteristics, structural properties, and biological activity. These compounds are found in nature with a wide range of effects, highlighting their antibacterial, antifungal, and antiprotozoal properties. Additionally, naphthoquinones are used as a scaffold to obtain new derivatives with pharmacological potential, mainly compounds against parasitic diseases. OBJECTIVE: The purpose of this work was to carry out a comprehensive review of naphthoquinones and their derivatives obtained from both natural and synthetic sources, also, to analyze their biological activity against Leishmania spp. (Leishmaniasis), Trypanosoma cruzi (Chagas disease), Plasmodium falciparum (Malaria), Toxoplasma gondii (Toxoplasmosis), and Toxocara canis (Toxocariasis). All of these agents are responsible for relevant diseases worldwide. RESULTS: Natural naphthoquinones, such as plumbagin, diospyrin, burmanin, lapachol, lawsone and psychorubrin, show an antiprotozoal activity similar or enhanced antiprotozoal activity to reference drugs. Some naphthoquinones obtained by synthesis or semi-synthesis showed better biological activity or less toxic effects than natural compounds. CONCLUSION: In this review, natural and synthetic naphthoquinones showed antiparasitic activity, in most cases, with improved results than current drugs currently used in clinical trials. A modification of their structure with different functional groups can enhance their biological effects, improve solubility, and reduce undesirable side effects. Therefore, naphthoquinones are important molecules in the development of new chemotherapeutic agents against parasitic diseases.

Effectiveness of Credelio® Plus, a novel chewable tablet containing milbemycin oxime and lotilaner for the treatment of larval and immature adult stages of Toxocara canis in experimentally infected dogs.

BACKGROUND: The ascarid, Toxocara canis, is a common and important zoonotic intestinal nematode parasite that infects dogs globally. An effective treatment that kills any pre-patent stages of immature T. canis could additionally reduce or eliminate the development of patent infections that can result in clinical disease in infected dogs and would further reduce environmental contamination of eggs. Two randomized, blinded, GCP-compliant, pivotal laboratory dose confirmation studies were conducted to assess the effectiveness and safety of a new novel combination of lotilaner and milbemycin oxime tablets (Credelio Plus) administered orally to dogs that were experimentally infected with immature (L4 or immature adult [L5]) stages of T. canis. METHODS: The commercial tablet formulation of Credelio Plus® was administered in a time frame relative to inoculation with infective eggs. This allowed for effectiveness to be assessed against each specific immature stage of T. canis. In each study, dogs were randomized and allocated to one of four treatment groups. Each treatment group contained ten dogs that had been experimentally inoculated on Day 0 with infective T. canis eggs and then were dosed once on Day 14 or Day 24 using either placebo tablets or Credelio Plus tablets (IP) to provide minimum dosages of 0.75 mg/kg of milbemycin oxime and 20 mg/kg of lotilaner. All dogs were necropsied 5 or 6 days after their respective treatment. At necropsy, all nematodes recovered from the gastrointestinal tract were counted by species and stage. RESULTS: In both dose confirmation studies using geometric mean worm counts, effectiveness of Credelio Plus was ≥ 98.6% and ≥ 96.8% against L4 larval stage T. canis and immature adult [L5] T. canis in both studies, respectively. CONCLUSIONS: These studies demonstrated that the Credelio Plus combination tablet administered orally to dogs was highly efficacious against experimental infections with L4 and immature adult [L5] stages of T. canis.

Protective effect of the probiotic Lactobacillus acidophilus ATCC 4356 in BALB/c mice infected with Toxocara canis.

Human toxocariasis consists of chronic tissue parasitosis that is difficult to treat and control. This study aimed to evaluate the action of the probiotic Lactobacillus acidophilus ATCC 4356 on larvae of Toxocara canis and the effect of IFN-γ cytokine on parasite-host in vivo (1.109 CFU) and in vitro (1.106, 1.107, 1.108, 1.109 CFU) interactions. Four groups of six BALB/c mice were formed: G1 - L. acidophilus supplementation and T. canis infection; G2 - T. canis infection; G3 - L. acidophilus supplementation; and G4 - PBS administration. Mice were intragastrically suplemented with probiotics for 15 days before inoculation and 48 h after inoculation with 100 T. canis eggs. The inoculation of T. canis was also perfomed intragastrically. The recovery of larvae took place through digestion of liver and lung tissues; the evaluation of IFN-γ gene transcription in leukocytes was performed by qPCR. The in vitro test consisted of incubating the probiotic with T. canis larvae. The supplementation of probiotics produced a reduction of 57.7% (p = 0.025) in the intensity of infection of T. canis larvae in mice, whereas in the in vitro test, there was no larvicidal effect. In addition, a decrease in the IFN-γ gene transcription was observed in both, T. canis-infected and uninfected mice, regardless of whether or not they received supplementation. The probiotic L. acidophilus ATCC 4356 reduced T. canis infection intensity in mice, however, the probiotic did not have a direct effect on larvae, demonstrating the need of interaction with the host for the beneficial effect of the probiotic to occur. Yet, the proinflammatory cytokine IFN-γ did not apparently contributed to the observed beneficial effect of probiotics.

Efficacy of a chlorocresol-based disinfectant product on Toxocara canis eggs.

Toxocara canis is a common parasite of dogs and can cause zoonotic toxocariasis in humans. As a part of control programs for this agent, optimized hygiene including chemical disinfection is considered essential in the prevention and control of zoonotic toxocariasis in humans. However, commonly used disinfectants at present mostly fail to inhibit the embryogenesis and viability of T. canis eggs. To this effect, the present study was designed to evaluate the effect of a chlorocresol-based disinfectant product Neopredisan®135-1 (NP) on embryonic development of T. canis eggs in vitro and to investigate the infectivity of exposed eggs by assessing larval establishment in a mouse model. Under in vitro conditions, NP at a final concentration of 0.25, 0.50, 1, 2, or 4% all exhibited significant killing effect on T. canis embryogenesis compared with the control eggs (P < 0.05), regardless of contact times (30, 60, 90, or 120 min). Such killing activity increased in a concentration- and time-dependent manner, with a maximum killing efficacy of 95.81% at 4% concentration and 120 min exposure time. Comparisons between low and high concentrations and between short and long contact times concluded that a protocol using the 1% concentration of NP with a 90-min contact could be the most suitable for practical application. Additionally, the lower larval recovery in mice inoculated with eggs treated by either 0.25 or 0.5% NP than that from their corresponding controls (P < 0.05) verified once again that NP had an adverse impact on the larval development of T. canis eggs even at a low concentration. To the best of our knowledge, this is the first study to report the effect of the chlorocresol-based disinfectant NP on the embryonation and larval development of T. canis eggs, and the results presented here would contribute to environmental clearance and control of toxocariasis by providing an alternative disinfectant resource. However, it is highlighted that the clearance of the novel and existing sources of infection including larvated eggs in places treated with NP is not guaranteed and therefore continuous monitoring and additional disinfection are still required.

Efficacy of a new oral chewable tablet containing sarolaner, moxidectin and pyrantel (Simparica Trio™) against induced ascarid infections in dogs.

BACKGROUND: Ascarid infections are among the most prevalent intestinal parasitic infections occurring in dogs around the world, with Toxocara canis and Toxascaris leonina commonly observed. Toxocara canis can cause considerable disease in dogs and humans, and year-round prophylactic treatment and control in dogs is recommended. Elimination of immature stages of these parasites before egg-laying will reduce environmental contamination and the risk of infection for both dogs and humans. Studies were conducted to evaluate the efficacy of a novel, oral chewable tablet containing sarolaner, moxidectin and pyrantel (Simparica Trio™) against induced immature adult (L5) and adult T. canis, and adult T. leonina infections in dogs. METHODS: Six negative-controlled, masked, randomized laboratory studies were conducted. Two studies each evaluated efficacy against immature adult (L5) T. canis, adult T. canis, and adult T. leonina. Sixteen to 40 dogs were included in each study. Dogs experimentally infected with the target parasite were dosed once on Day 0 with either placebo tablets or Simparica Trio™ tablets to provide minimum dosages of 1.2 mg/kg sarolaner, 24 µg/kg moxidectin and 5.0 mg/kg pyrantel (as pamoate salt). Efficacy was based on the number of worms recovered at necropsy 7-10 days after treatment compared to placebo control. RESULTS: Based on geometric mean worm counts, efficacy of the sarolaner + moxidectin + pyrantel combination was ≥ 95.2% against immature adult T. canis, ≥ 97.3% against adult T. canis, and ≥ 89.7% against adult T. leonina. There were no treatment-related adverse events in any study. CONCLUSIONS: These studies confirm the efficacy of a single dose of a new oral chewable tablet containing sarolaner, moxidectin and pyrantel (Simparica Trio™) against immature adult and adult T. canis, and adult T. leonina infections in dogs.

Is routine disinfection efficient in preventing contamination with Toxocara canis eggs?

Toxocara canis (Werner, 1782) is a zoonotic nematode commonly parasitizing dogs worldwide with great public health importance as the aetiological agent of human toxocariasis. In this respect, the aim of this study was to evaluate the effect of six disinfectant products commonly used in kennels, veterinary clinics and as household cleaning products on the embryogenesis and viability of T. canis eggs. The composition of active ingredients in these commercial disinfectants was sodium hypochlorite (A); a mix of N-(3-aminopropyl)-N-dodecylpropan-1.3-diamine and didecyldimethylammonium chloride (B); sodium dichloroisocyanurate dehydrate (C); a mix of glutaraldehyde, quaternary ammonium compounds, benzyl-c12-18-alkyldimethyl and chlorides (D); a mix of 2-propanol, ethanol, benzalkonium chloride and glucoprotamin (E); a mix of pentapotassium bis (peroxymonosulphate) bis (sulphate), sodium C10-13-alkylbenzenesulphonate, malic acid, sulphamidic acid, sodium toluenesulphonate, dipotassium peroxodisulphate and dipentene (F). After dilution, the tested disinfectants had the maximal concentration recommended by the manufacturer in order to achieve a biocidal effect. Each product was tested on approximately 10,000 T. canis eggs, having five different contact times (5, 10, 15, 30, 60 min). Three replicates were tested for each diluted disinfectant and for each contact time. After the treatment, eggs were washed and incubated in distilled water at 27 °C for 2 weeks. None of the tested products had a significant inhibitory effect on the embryogenesis and viability of T. canis eggs, regardless of the contact time. Moreover, after 2 weeks, in all tested samples, eggs containing motile infective larvae were identified, showing that routinely used disinfectants do not eliminate risk of infection by T. canis.

Progesterone in vitro increases growth, motility and progesterone receptor expression in third stage larvae of Toxocara canis.

The in vitro effect of progesterone in T. canis larvae on their enlargement and motility were evaluated, together to the possible presence of progesterone receptors (PRs). T. canis larvae were cultured in RPMI-1640 with different concentrations of progesterone (0, 20, 40, 80, 400 and 800 ng/mL). Enlargement and increases in motility were dependent on the concentration only from 0 to 80 ng/mL (p < 0.05). The mean percentage of PR + cells in newly obtained larvae as measured by flow cytometry was 8.16 ± 0.4. The number of PR + cells increased depending on concentration from 0 to 80 ng/mL (p < 0.001). Cells obtained from larvae stimulated at any of the studied hormone concentrations showed greater mean fluorescence intensity when compared to non-stimulated cells. Additionally, the expression and location of PR + cells were determined in the larvae. The sequence of an amplicon (420-bp) obtained by PCR from T. canis larvae showed 100% homology with a gene fragment that codes for the PR of the dog. PR + cells were immunolocated using confocal microscopy in the intestinal region of the larvae that had been recently obtained. The results of this study show that T. canis larvae can recognize and respond to the presence of progesterone through a molecule possibly able to bind it. Since we previously observed a similar response to prolactin, we suggest that both hormones could participate sequentially in the reactivation of T. canis larvae in pregnant bitches.

Study of the Effect of Metal Complexes on Morphology and Viability of Embryonated Toxocara canis Eggs.

An organic salt and four metal complexes derived from azole were evaluated against embryonated Toxocara canis eggs (TCE). The new organic salt, (LH)+(FeCl4)-, where L = 3,5-bis(3,5-dimethylpyrazole-1-ylmethyl)toluene (5), a potential environmental disinfectant, was isolated as an air-stable yellow solid and characterized by elemental analysis, electrical conductivity, mass spectrometry, and infrared and ultraviolet/visible spectroscopy. In addition, the structure of 5 was determined by single-crystal X-ray diffraction. Compound 2 showed high anti-TCE activity. Interestingly, these compounds showed little effect on hepatocytes, indicating that they are not cytotoxic. These results will assist in the design of anti-TCE compounds.

Longitudinal study for anthelmintic efficacy against intestinal helminths in naturally exposed Lithuanian village dogs: critical analysis of feasibility and limitations.

The efficacy of anthelmintic treatment at 1, 3, and 6 month intervals was evaluated in a prospective controlled field study with naturally exposed Lithuanian village dogs by monthly coproscopy during 1 year. A placebo-treated control group (C) (n = 202) and groups treated with two broad-spectrum anthelmintics, febantel/pyrantel-embonate/praziquantel (Drontal® Plus, Bayer) (D1, D3, D6; n = 113-117) and emodepside/praziquantel (Profender®, Bayer) (P1, P3, P6; n = 114-119), were included. At the beginning of the study, eggs of Toxocara canis (4.02%) and T. cati (0.44%) identified morphometrically and/or molecularly and eggs of taeniid- (0.78%) and Capillaria-like eggs (5.03%) were present in the feces without significant differences in prevalence between groups. Significant decreases in excretion of T. canis eggs was found 1 month after the treatment with Drontal® Plus in February (D1) and with Profender® in October (P1), November (P1), December (P3), February (P1), and March (P1, P3), as compared to controls in the same months. The incidence of egg excretion per dog at least once a year was significantly lower in group P1 for T. canis (4.24%; p < 0.01) and in groups D1, P1 for taeniid eggs (0%; p < 0.01 and p < 0.001), when compared to controls (16.96 and 6.70%, respectively). A critical analyses of factors possibly responsible for intestinal passage of canine helminth eggs revealed that chained dogs excreted T. canis eggs more frequently 1 month after treatment compared to dogs in pens, particularly from November to March (p = 0.01). The incidence of single detection of T. cati eggs was significantly increased in chained dogs (12.46%) as compared to fenced dogs (1.08%; p = 0.0001).

Lactobacillus rhamnosus reduces parasite load on Toxocara canis experimental infection in mice, but has no effect on the parasite in vitro.

Human toxocariasis is a neglected global parasitic zoonosis. The efficacy of drug treatment for this disease has been hindered by the biological complexity of the main etiological agent, the nematode Toxocara canis. Experimental studies have shown the potential of probiotics to promote a reduction in the parasite load of T. canis larvae. This study aimed to evaluate the effect of probiotic Lactobacillus rhamnosus ATCC 7469 on the parasite load of BALB/c mice with acute toxocariasis and evaluate the direct effect of this probiotic on T. canis larvae in vitro. In vivo administration of probiotics reduced the parasite load of T. canis larvae by 53.3% (p = 0.0018) during the early stage of infection in mice. However, when analyzed in vitro, it was observed that the probiotic did not present a deleterious effect on the larvae, as approximately 90% of these remained viable. These results demonstrate the potential of the probiotic L. rhamnosus in the reduction of T. canis larvae in BALB/c mice and suggest it could be used as an alternative means for the controlling of visceral toxocariasis. However, further studies are required to elucidate the mechanisms of action promoted by this probiotic.

Flotation of Toxocara canis Eggs in Commercial Bleach and Effects of Bleach Treatment Times on Larval Development in These Eggs.

Toxocara canis is a common intestinal nematode of young dogs. Puppies contaminate the environment with large numbers of eggs that can embryonate and become infective in less than a month. Embryonated eggs are infectious for humans and other paratenic hosts. Most T. canis infections in humans are asymptomatic; however, migration of T. canis larvae in the eye and in the central nervous system can result in vision loss, blindness, and even death. The eggs of T. canis are highly resistant to harsh environmental conditions and routinely used chemical disinfectants. The objective of this study was to evaluate the effects of full-strength commercial bleach (5.25% sodium hypochlorite solution) treatment on development of T. canis eggs and to report our serendipitous finding that T. canis eggs in dog feces can float in passive fecal flotation tests using bleach. We also demonstrated that T. canis eggs could be identified using the McMaster's fecal eggs counting test using 100% bleach. Toxocara canis eggs collected from the feces of naturally infected 4-8 wk old puppies were treated with full-strength bleach (5.25% sodium hypochlorite solution) for 15 min, 30 min, 60 min, and 120 min; washed free of bleach smell by centrifugation; and resuspended in 0.1 N sulfuric acid solution to undergo larval development at room temperature for 18 days after exposure to bleach. Motile larvae were observed in T. canis eggs in all groups treated for 15-120 min and eggs continuously exposed to bleach for 18 days. Our results indicate that bleach may not be an appropriate disinfectant for dog kennels, cages, or laboratory utensils and work surfaces. Toxocara canis eggs are resistant to bleach treatment and continue to pose a risk for canine and human infections. Further study is needed to find the most appropriate methods for disinfection and removal of eggs to reduce the risk of transmission of this parasite.

The in vitro effect of prolactin on the growth, motility and expression of prolactin receptors in larvae of Toxocara canis.

The in vitro effect of prolactin (PRL) on the growth and motility of Toxocara canis larvae was assessed. Additionally, the expression and location of prolactin receptors (PRL-Rs) were determined in the larvae. Larvae of T. canis were incubated with different concentrations of PRL for different periods of time. The stimulated larvae accelerated their enlargement and increased their motility. The mean percentage of PRL-R+ cells in non-stimulated larvae, measured by flow cytometry was 7.3±0.3%. Compared with non-stimulated larvae, the mean fluorescence intensity (p<0.05) increased in larvae incubated with 40ng/mL of PRL for 10 days. A 465-bp length fragment was amplified from larvae gDNA by PCR. The sequence of this fragment showed 99% similarity with the gene fragment that codes for the PRL-R of the domestic dog. A high concentration of PRL-Rs was immune-located in the posterior region of the larval intestine; therefore, the intestinal cells in this region were most likely the targets for this hormone. Based on these results, PRL-Rs were identified in T. canis larvae, and the in vitro stimulation with PRL increased the number of these receptors, accelerated the growth and modified the activity of larvae. All of the above suggest that T. canis larvae are evolutionarily adapted to recognize the PRL of their definitive host and furthermore might explain the reactivation of tissue-arrested larvae during the gestation of bitches, which does not occur in gestating females of other species.

Toxocara canis: anthelmintic activity of quinone derivatives in murine toxocarosis.

Human toxocarosis is a chronic tissue parasitosis most often caused by Toxocara canis. The seroprevalence can reach up to 50%, especially among children and adolescents. The anthelmintics used in the treatment have moderate efficacy. The aim of this study was to evaluate the in vitro and in vivo anthelmintic activity of quinones and their derivatives against T. canis larvae and the cytotoxicity of the larvicidal compounds. The compounds were evaluated at 1 mg mL(-1) concentration in microculture plates containing third stage larvae in an Roswell Park Memorial Institute (RPMI) 1640 environment, incubated at 37 °C in 5% CO2 tension for 48 h. Five naphthoxiranes were selected for the cytotoxicity analysis. The cell viability evaluated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide and lactate dehydrogenase assays using murine peritoneal macrophages isolated from C57BL/6 mice revealed that the naphthoxiranes (1 and 3) were less cytotoxic at a concentration of 0.05 mg mL(-1). The efficacy of naphthoxiranes (1 and 3) was examined in murine toxocarosis also. The anthelmintic activity was examined by evaluating the number of larvae in the brain, carcass, liver, lungs, heart, kidneys and eyes. Compound (3) demonstrated anthelmintic activity similar to that of albendazole by decreasing the number of larvae in the organs of mice and thus could form the basis of the development of a new anthelmintic drug.

Toxocara canis: Larvicidal activity of fatty acid amides.

Considering the therapeutic potential of fatty acid amides, the present study aimed to evaluate their in vitro activity against Toxocara canis larvae and their cytotoxicity for the first time. Linoleylpyrrolidilamide was the most potent, with a minimal larvicidal concentration (MLC) of 0.05 mg/mL and 27% cytotoxicity against murine peritoneal macrophages C57BL/6 mice, as assessed by the MTT assay.