Additive larvicidal activity of albendazole combined with a hydroxyethylamine-derived compound against Toxocara canis larvae: An in vitro and in silico study.

Sesbania grandiflora is a slender tree. It is a common garden plant in Sri Lanka, which grows well in mid and low country. In Sri Lanka, Sesbania grandiflora is used as a home remedy, in treatment of worm infections in humans. Toxocara canis is a helminth parasite infecting dogs and other canids. It also causes toxocariasis in humans. Haemonchus contortus is a nematode that infects goats and causes anaemia, marked reduction in growth and reproduction, and even death. Using this information, in vitro larvae migratory inhibition assay was carried out on Toxocara canis and Haemonchus contortus larve. This study revealed 98.1% and 94.3% larvae migration inhibition with larvae of Toxocara canis and Haemonchus contortus respectively. Least number of migrated larvae was observed in the positive control Levamisole and all the larvae were dead after migration. In decoction of S.grandiflora, all the migrated Toxocara larvae were dead and Haemonchus larvae were dead or in Grade1 (inactive but occasional movement can be observed) condition. Inhibition of Toxocara larval migration and Haemonchus larval migration with decoction of Sesbania grandiflora and Levamisole are statically significant (p < 0.05). Since mean of LMI (larval migration inhibition) of Levamisole is greater than mean of LMI of Sesbania grandiflora with both larvae, Levamisole is more effective than Sesbania grandiflora. Based on these findings, the aqueous extract of leaves of Sesbania grandiflora is shows a statistically significant anthelmintic activity in in-vitro model.

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 1mg/mL, and compounds with larvicidal activity were serially diluted to obtain concentrations of 0.5mg/mL; 0.25mg/mL; 0.125mg/mL; and 0.05mg/mL. The tests were performed in a microculture plate containing 100T. 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 7-8weeks 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.

Toxocara canis: larvicidal activity and bioavailability analysis of 2-pyrimidinyl-hydrazone derivatives.

Toxocara canis, the causative agent of zoonotic toxocariasis in humans, is a parasitic roundworm of canids with a complex lifecycle. While macrocyclic lactones (MLs) are successful at treating adult T. canis infections when used at FDA-approved doses in dogs, they fail to kill somatic third-stage larvae. In this study, we profiled the transcriptome of third-stage larvae derived from larvated eggs and treated in vitro with 10 μM of the MLs - ivermectin and moxidectin with Illumina sequencing. We analyzed transcriptional changes in comparison with untreated control larvae. In ivermectin-treated larvae, we identified 608 differentially expressed genes (DEGs), of which 453 were upregulated and 155 were downregulated. In moxidectin-treated larvae, we identified 1,413 DEGs, of which 902 were upregulated and 511 were downregulated. Notably, many DEGs were involved in critical biological processes and pathways including transcriptional regulation, energy metabolism, neuronal structure and function, physiological processes such as reproduction, excretory/secretory molecule production, host-parasite response mechanisms, and parasite elimination. We also assessed the expression of known ML targets and transporters, including glutamate-gated chloride channels (GluCls), and ATP-binding cassette (ABC) transporters, subfamily B, with a particular focus on P-glycoproteins (P-gps). We present gene names for previously uncharacterized T. canis GluCl genes using phylogenetic analysis of nematode orthologs to provide uniform gene nomenclature. Our study revealed that the expression of Tca-glc-3 and six ABCB genes, particularly four P-gps, were significantly altered in response to ML treatment. Compared to controls, Tca-glc-3, Tca-Pgp-11.2, and Tca-Pgp-13.2 were downregulated in ivermectin-treated larvae, while Tca-abcb1, Tca-abcb7, Tca-Pgp-11.2, and Tca-Pgp-13.2 were downregulated in moxidectin-treated larvae. Conversely, Tca-abcb9.1 and Tca-Pgp-11.3 were upregulated in moxidectin-treated larvae. These findings suggest that MLs broadly impact transcriptional regulation in T. canis larvae.

Transcriptional responses to in vitro macrocyclic lactone exposure in Toxocara canis larvae using RNA-seq

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 120min). Such killing activity increased in a concentration- and time-dependent manner, with a maximum killing efficacy of 95.81% at 4% concentration and 120min 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.

Field evaluation of a rapid diagnostic test to detect antibodies in human toxocariasis

Human toxocariasis – A look at a neglected disease through an epidemiological ‘prism’

Ivermectin has shown potent activity against various nematodes. Evaluation of the efficacy of ivermectin against Toxocara canis larvae. In vitro assessment was conducted using larval migration inhibition test and scanning electron microscopy (SEM). In vivo, ivermectin was administered orally to mice at a single 0.2 mg/kg dose at 2 (group I), 7 (group II), or 15 days (group III) post-infection. Efficacy was evaluated through brain larval counts and histopathological examination of liver and brain. In vitro, ivermectin at concentrations of 10 μg/ml and 100 μg/ml inhibited larval migration by 8.5% and 87%, respectively. SEM showed cuticular damage after 24 and 48 hours with 100 μg/ml ivermectin. In vivo, brain larval counts significantly decreased in groups I and II (22.67 ± 5.41 and 37.17 ± 5.98), with no significant reduction in group III (130.5 ± 9.01). Histopathology of the liver at four weeks post-infection in groups I and II revealed numerous granulomas with degenerated larvae. The brain showed a marked reduction in larval presence and inflammation in groups I and II, while group III findings were similar to those of the control group. Ivermectin is effective against T. canis larvae during early migratory stages but shows limited efficacy against late-stage larvae.

In vitro anthelmintic activity of the crude hydroalcoholic extract of Piper cubeba fruits and isolated natural products against gastrointestinal nematodes in sheep

Although human toxocariasis ranks among the most common zoonotic infections worldwide, it remains relatively unknown to the public. The causal agents are the nematode parasites Toxocara canis and T. cati, whose definitive hosts are dogs and cats, respectively. When embryonated eggs are accidentally ingested by humans, larvae hatch in the small intestine, penetrate the intestinal wall and migrate, via the bloodstream, to the liver, lungs, muscles, eye and central nervous system. Although most human infections are asymptomatic, two well-defined clinical syndromes are classically recognised: visceral larva migrans (a systemic disease caused by larval migration through major organs) and ocular larva migrans (a disease limited to the eyes and optic nerves). Two less-severe syndromes have recently been described, one mainly in children (covert toxocariasis) and the other mainly in adults (common toxocariasis). Here, the current laboratory diagnosis, epidemiology and main clinical features of both the systemic and ocular forms of human toxocariasis are reviewed. New developments in serological diagnosis are described, the available seroprevalence data are analysed, and the results of relevant clinical studies that have been published over the last decade are explored, to provide an updated overview of this neglected but highly prevalent human infection.

A simplified method for hatching and isolating Toxocara canis larvae to facilitate excretory–secretory antigen collection in vitro

Veterinary RecordVolume 184, Issue 7 p. 224-225 Letters and notices Human toxocariasis and neutering cats Ian Wright, Corresponding Author Ian Wright info@esccap.org ESCCAP Secretariat, Malvern Hills Science Park, Malvern, Worcestershire,...

Human ocular toxocariasis (OT), caused by pet roundworm Toxocara canis (Nematoda Ascaridoidea), is a worldwide ocular parasitic infection that poses a severe threat to eyesight, especially in school-aged children. However, the infection process and pathological mechanism of Toxocara are difficult to study in the human body. This study was designed to explore long-term ocular manifestations in different rodents infected with Toxocara canis, uncovering the specific pathological mechanism and migration pathway of larvae after infection. The three types of experimental animals we selected were C57BL/6 mice, Mongolian gerbils and Brown Norway rats. Mice were randomly divided into five groups and infected orally with 1000, 2000, 4000, 8000 and 10,000 T. canis eggs; gerbils were randomly divided into four groups and infected orally with 1000, 2000, 4000 and 10,000 T. canis eggs; rats were randomly divided into three groups and infected orally with 2000, 6000 and 10,000 T. canis eggs. Their ocular changes were closely observed and recorded for at least 2months. We also enucleated the eyeballs of some animals to perform pathological sectioning and hematoxylin-eosin staining. After 3 dpi (days post-infection), hemorrhagic lesions, mechanical injury of the retina and larval migration could be observed in some infected animals. The ocular infection and mortality rates tended to be stable at 7 dpi. Larval tissue, structure disorder and inflammation could be observed in the pathological sections. In conclusion, the mice infected with 2000T. canis eggs and gerbils infected with 1000, 2000 and 4000T. canis eggs showing obvious ocular lesions and lower mortality rates could provide a basis for long-term observation.

Human toxocariasis is a widespread parasitic disease caused by ingestion of Toxocara canis or catis larvae or eggs. Parasitic diseases are uncommon in industrialized countries, yet this problem has not disappeared. Parasitic diseases can cause different syndrome (visceral larva migrans, ocular larva migrans) and the clinical features can be confusing. Severe organ involvement affecting the liver, lungs, nervous central system and eyes can lead to serious damage. We present a case of toxocariasis presenting with fever, desaturation and cholestatic hepatitis. Only the subsequent appearance of eosinophilia helped us to arrive at the correct diagnosis. Prompt diagnosis allowed specific therapy avoiding permanent complications.