BACKGROUND: Toxocariasis is a prevalent zoonosis disease caused by the closely 
related nematode species Toxocara canis and Toxocara cati which parasitise 
Canidae and Felidae respectively. In paratenic hosts, larvae of these worms 
cause multiple organ damage. However, how these paratenic hosts response to 
these worms and whether any common biomarker can be applied for diagnosis are 
still unclear.
METHODS: Excreted/secreted (E/S) antigens were prepared by culture of T. canis 
larvae in vitro. Using a western blot (WB) assay the humoral IgG responses, 
induced by Toxocara spp. larvae to the worm's E/S antigens in different infected 
hosts including mice, rabbits and human, were examined.
RESULTS: In a mouse model of toxocariasis, intraperitoneal injection of T. canis 
larvae induces inflammatory leukocyte accumulation in the liver and the lungs 
but not in the brain, although a remarkable number of larvae were detected in 
this organ. Mice and rabbits responded differently to Toxocara spp. resulting in 
distinct heterogenous WB band patterns. Mice and rabbits both responded to a 
33.1 kDa E/S constituent that turned out to be the most sensitive protein for 
serodiagnosis. Sera from human toxocariasis patients showed heterogenous WB band 
patterns similar to those observed in rabbits and all responded to the 33.1 kDa 
band.
CONCLUSION: 33.1 kDa E/S protein can be considered as a critical common 
biomarker for toxocariasis immuno-diagnosis in both paratenic animals and human 
and its specificity requires further investigation.