Larval migration of the ascarid nematode Toxocara canis following infection and re-infection in the gerbil Meriones unguiculatus

Abstract

A morphological and immunohistochemical study of larval migration patterns was performed in gerbils that were infected once (primary infected group) or twice (secondary infected group) with 1500 eggs of Toxocara canis. Animals from the primary infected and the re-infected group were killed at different times after infection, and larvae were counted in the intestines, liver, lungs and brain. Fragments of all organs were formalin fixed and paraffin embedded for histology and immunohistochemistry analyses (using polyclonal anti-Toxocara serum raised in rabbits infected with T. canis). In the primary infected group, larvae were more abundant in the intestine at 24 h, in the liver and lungs between 24 and 72 h and in the brain after 96 h; larvae predominated in the brain for up to 60 days after infection. In the re-infected group, an increase in the number of larvae in the liver and a reduction in the number of larvae in the brain was observed up to 60 days after re-infection. Inflammatory reactions were absent or limited. Eosinophils and loose granulomata were observed around the larvae and their antigens in the primary infected group and were more severe. Many eosinophils and typical epithelioid granulomata were observed around larvae in the re-infected group. These results demonstrate that the migration pattern of T. canis larvae in gerbils is similar to that in mice and rats, exhibiting a late neurotropic stage. In the re-infected group, there was histological evidence of an adaptive T-helper 2 (Th-2) response, and larvae were apparently retained within granulomata in the liver, without obvious signs of destruction.

Human Toxocariasis: 2010 to 2020 Contributions from Brazilian Researchers

“…The migration patterns of T. canis larvae in the gerbil Meriones unguiculatus were similar to the patterns already observed in mice and rats; however, in reinfected animals, more larvae were apparently retained within hepatic granulomas, without evident signs of destruction. 118 There are numerous references in the literature on behavioral changes in rodents experimentally infected with T. canis, which are associated with larvae located in the central nervous system. 119,120 Before reaching the nervous system, the larvae pass through muscle tissues, being able to determine alterations.…”

“…The migration patterns of T. canis larvae in the gerbil Meriones unguiculatus were similar to the patterns already observed in mice and rats; however, in reinfected animals, more larvae were apparently retained within hepatic granulomas, without evident signs of destruction. 118 …”

Atypical presentation of hepatic visceral larva migrans mimicking cancer and associated with ADAMTS13 deficiency–mediated thrombotic microangiopathy: A first report from Reunion Island

“…In our patient's case, the lack of any lung or lymphatic involvement therefore represented a puzzling difference, the origin of which could lie in an intense phenomenon of larval liver trapping [14]. Experiments carried out in animal models have demonstrated that the fate of Toxocara larvae entering the liver (see "Introduction") depends upon the size of the inoculum (number of ingested embryonated eggs) and the repetition of infection, in addition to genetic factors [15,16]. Following infection with smaller inoculums, larvae went freely through the liver.…”

Experimental Toxocara canis infection in chickens

“…In addition, the findings of this study are consistent with previous studies, the lungs from infected chickens appeared petechial hemorrhages on the surface. Interstitial pneumonia, the formation of dark to gray inflammatory nodules in the lung tissue as a result of migrating larvae, and the atelectatic area are also all observed lung abnormalities (Taira et al, 2003;Flecher et al, 2016). The lung injuries from infected chickens were unevenly distributed.…”