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

Abstract

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.

Seroprevalence of Toxoplasma gondii and Toxocara canis in a human rural population of Southern Rio Grande do Sul

“…The risk factors and behaviors in children include frequent contact with soil in playgrounds and schools, recreation rooms or sandboxes containing dog and cat feces, poor personal hygiene, geophagia, and the lack of parental supervision 5 , 6 . There are also other forms of transmission such as organ transplantation, blood transfusion, and vertical transmission in humans 7 - 10 .…”

Brain food: rethinking food-borne toxocariasis

“…Larval motility was reported as absent after 24 h freezing at −25°C, suggesting that the thermal death point for the larvae had been reached (Taira et al, 2011). This finding was supported by Dutra et al (2013), with a 100% reduction in larval viability following freezing of mouse liver tissue at −20°C, with larvae showing detrimental morphological changes including ruptured cuticles and internal organ degeneration (Dutra et al, 2013). In contrast, Sprent (1953) reported finding motile larvae in mice carcasses subjected to −20°C for 4 weeks, although the viability of these larvae was not assessed (Sprent, 1953).…”

“…In a similar study, chilling pig and poultry tissues at 4°C for 7 days had a significant effect on larval infectivity, but again infections could still be established in recipient pigs (Taira et al, 2004). Chilling infected mouse liver samples to between 0 and 4°C for 10 days was found to significantly reduce the intensity of infection in recipient mice (Dutra et al, 2013). These studies suggest the potential risk of Toxocara transmission by consumption of meat products is decreased by refrigeration, but the risk of human infection remains.…”

Saccharomyces boulardiireduces the vertical transmission ofToxocara canislarvae in mice

“…canis embryonated eggs (Epe, 2009; Amaral et al ., 2010). There are also specific measures to prevent infection with larvae present in the meat or viscera of bird and mammal species that have roles as paratenic hosts (Dutra et al ., 2013; Cardoso et al ., 2020).…”