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.

Evaluation of the initial and chronic phases of toxocariasis after consumption of liver treated by freezing or cooling.

Human toxocariasis is a neglected parasitic zoonosis of worldwide distribution. The consumption of raw or undercooked meat and offal from paratenic hosts of the Toxocara canis nematode can cause infection in humans, but there have been a lack of studies examining specific prophylactic measures to combat this mode of transmission. The aim of this study was to evaluate the establishment of infection by T. canis larvae at the initial and chronic phases of visceral toxocariasis after the consumption of mouse liver subjected to cold treatment. This study was divided into two stages using groups (G) of five donor mice inoculated with 2,000 eggs of T. canis. Two days post-inoculation, the livers of donor mice in G1 and G2 were kept at -20 °C and between 0 and 4 °C, respectively, for 10 days. In the first stage of the study, the livers of mice from G1, G2, and G3 (control) were subjected to a tissue digestion technique and found to be positive for infection. In the second stage, which evaluated infection in mice that had consumed livers from donor mice, receiver mice of G4 and G7 were fed with livers of donor mice from G1 (freezing), receiver mice of G5 and G8 were fed with livers of donor mice from G2 (cooling), and receiver mice of G6 and G9 with livers from G3 (control). Then, the tissue digestion technique was performed for recovering larvae from organs and carcasses of mice, at 2 days (G4, G5, and G6) and 60 days after liver consumption (G7, G8, and G9). It was observed that freezing inhibited the viability of 100 % of the larvae, while cooling promoted 87.7 and 95.7 % reductions in the intensity of infection at 2 and 60 days after liver consumption, respectively. Under the studied conditions, cold treatment shows great potential to help control this parasitosis, both in the initial and chronic phases of toxocariasis.

ANTHELMINTIC ACTIVITY OF LAPACHOL, ß-LAPACHONE AND ITS DERIVATIVES AGAINST Toxocara canis LARVAE.

Anthelmintics used for intestinal helminthiasis treatment are generally effective; however, their effectiveness in tissue parasitosis (i.e. visceral toxocariasis) is moderate. The aim of this study was to evaluate the in vitro activity of lapachol, ß-lapachone and phenazines in relation to the viability of Toxocara canis larvae. A concentration of 2 mg/mL (in duplicate) of the compounds was tested using microculture plates containing Toxocara canis larvae in an RPMI-1640 environment, incubated at 37 °C in 5% CO2 tension for 48 hours. In the 2 mg/mL concentration, four phenazines, lapachol and three of its derivatives presented a larvicide/larvistatic activity of 100%. Then, the minimum larvicide/larvistatic concentration (MLC) test was conducted. The compounds that presented the best results were nor-lapachol (MLC, 1 mg/mL), lapachol (MLC 0.5 mg/mL), ß-lapachone, and ß-C-allyl-lawsone (MLC, 0.25 mg/mL). The larvae exposed to the compounds, at best MLC with 100% in vitro activity larvicide, were inoculated into healthy BALB/c mice and were not capable of causing infection, confirming the larvicide potential in vitro of these compounds.

Risk of infection by the consumption of liver of chickens inoculated with low doses of Toxocara canis eggs.

Experimental studies and registries of cases of human toxocariasis have shown that the consumption of raw or undercooked offal of the paratenic host of Toxocara canis may pose a risk of infection. Thus, we evaluated the risk of infection due to the consumption of liver of chickens inoculated with different doses of embryonated T. canis eggs. Doses were 5-100 times smaller than the ones previously employed in this type of study. Groups of five chickens were inoculated with 5000 (control), 1000, 500, 300 or 50 eggs of T. canis, and at 72 h post-inoculation, the liver of each bird was consumed by a BALB/c receptor mouse. Forty-eight hours after consumption, we examined the organs and carcasses of the mice for larvae of T. canis. All mice were positive for larvae, except the group that consumed the chicken liver inoculated with 50 eggs. This group contained only one positive mouse, in which the larva was lodged in the brain. In mice that consumed livers of chickens inoculated with ≥300 eggs, larvae concentration was primarily in the liver and lungs, characterizing the initial phase of infection. We conclude that the consumption of raw poultry liver, under the studied conditions, poses a risk of infection even with a low number of infected T. canis eggs.

ANTHELMINTIC ACTIVITY OF LAPACHOL, β-LAPACHONE AND ITS DERIVATIVES AGAINST Toxocara canis LARVAE / Atividade anti-helmíntica do lapachol, β-lapachona e derivados contra larvas de Toxocara canis

Anthelmintics used for intestinal helminthiasis treatment are generally effective; however, their effectiveness in tissue parasitosis (i.e. visceral toxocariasis) is moderate. The aim of this study was to evaluate the in vitro activity of lapachol, β-lapachone and phenazines in relation to the viability of Toxocara canis larvae. A concentration of 2 mg/mL (in duplicate) of the compounds was tested using microculture plates containing Toxocara canis larvae in an RPMI-1640 environment, incubated at 37 °C in 5% CO2 tension for 48 hours. In the 2 mg/mL concentration, four phenazines, lapachol and three of its derivatives presented a larvicide/larvistatic activity of 100%. Then, the minimum larvicide/larvistatic concentration (MLC) test was conducted. The compounds that presented the best results were nor-lapachol (MLC, 1 mg/mL), lapachol (MLC 0.5 mg/mL), β-lapachone, and β-C-allyl-lawsone (MLC, 0.25 mg/mL). The larvae exposed to the compounds, at best MLC with 100% in vitro activity larvicide, were inoculated into healthy BALB/c mice and were not capable of causing infection, confirming the larvicide potential in vitro of these compounds.

Os anti-helmínticos empregados no tratamento das helmintoses intestinais, de modo geral, são eficazes, porém nas parasitoses teciduais, como é o caso da toxocaríase visceral, a eficácia é moderada. Este estudo teve como objetivo avaliar in vitro a atividade do lapachol, β-lapachona e fenazinas derivadas da β-lapachona sobre a viabilidade de larvas de Toxocara canis. Os compostos foram testados na concentração de 2 mg/mL (em duplicata) em placas de microcultivo, contendo larvas de T. canis em meio RPMI-1640, sendo incubados, a 37 °C, em tensão de CO2 de 5%, por 48 horas. Na concentração de 2 mg/mL, quatro fenazinas, o lapachol e três derivados, apresentaram atividade larvicida/larvostática de 100%. A seguir, foi realizado o teste de concentração larvicida/larvostártica mínima (CLM). Os compostos que apresentaram os melhores resultados foram o nor-lapachol (CLM, 1 mg/mL), lapachol (CLM, 0,5 mg/mL), a β-lapachona e a β-C-alil-lausona (CLM, 0,25 mg/mL). As larvas expostas aos compostos, na melhor CLM 100% in vitro foram inoculadas em camundongos BALB/c saudáveis não sendo capazes de causar infecção, confirmando o potencial larvicida in vitro desses compostos.