Abstract
The present study aimed to experimentally assess Nile tilapia as potential paratenic host of Toxocara spp. A total of 15 Nile tilapia (Oreochromis niloticus) were fed with 300 embryonated Toxocara canis eggs by oral gavage, while five others of the control group received distilled water. The fish were individually analyzed at 16, 24, 48, 72, and 240 h after inoculation. Water contamination was assessed, and tissue migration by liver, gastrointestinal tract (GIT), eyes, and central nervous system. A murine model was used as the paratenic host for egg infectivity assessment. Eggs and larvae were found in plastic tank water and fish GIT, ranging from 23 to 86% per fish. Eggs and larvae were recovered from the tank water (76.3%) and fish GIT (23.7%). The counting of eggs and larvae observed was negatively correlated with number of eggs and larvae in the water tank (rho = −0.698, p = 0.003). Shedding of embryonated eggs was first detected at 16 and up to 240 h, with significant egg and larvae yield decrease on water-shedding (p = 0.001) and in the GIT (p = 0.007). Although no T. canis larva was recovered in fish tissues, egg infectivity after fish GIT transit was experimentally confirmed by mice assessment. In conclusion, despite shedding viable embryonated eggs through the gastrointestinal tract, tilapias may not play a role as a suitable paratenic hosts for Toxocara spp., posing low risk of zoonotic transmission by fish meat consumption.
Highlights
The consumption of raw or inadequately cooked fish has been increasingly popular throughout the world [1, 2]
The counting of eggs and larvae observed in the fish gastrointestinal tract (GIT) was negatively correlated with the number of eggs and larvae identified in the water tank
Regression models have shown a statistically significant decrease over time in egg shedding into the water tank (p = 0.001) and the presence of T. canis eggs in the fish GIT (p = 0.007; Table 2 and Figure 1)
Summary
The consumption of raw or inadequately cooked fish has been increasingly popular throughout the world [1, 2]. Several parasitic zoonotic agents may be related to such fish and seafood consumption, including Anisakis spp. Contamination of fish-based dishes during handling may contribute to spreading zoonotic diseases [8]. Toxocarosis has been considered one of the most prevalent parasitic zoonoses, in vulnerable populations [9,10,11]. Despite the widely used term “toxocariasis,” toxocarosis has been the standardized nomenclature of this animal parasitic disease [10, 11]. Toxocarosis is among the six most important neglected parasitic infections in the USA, along with Chagas disease, cyclosporiasis, cysticercosis, toxoplasmosis, and trichomoniasis, due to its high prevalence, chronic and disabling characteristics, and a strong link with poverty [12]
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