Isolate-specific rat brain transcriptional responses to rat lungworm (Angiostrongylus cantonensis).

The rat lungworm (Angiostrongylus cantonensis) is an invasive parasite of rats that in accidental hosts, such as dogs and humans, causes eosinophilic meningitis. In Australia, only two distinct rat lungworm cox1 haplotypes have been detected in clinically affected dogs, with haplotype Ac13 implicated in most cases. Using locally sourced isolates, we enquired whether the brain migrating larvae elicit different host response in its natural host. We examined brain transcriptome, faecal shedding rates, and adult worm of A. cantonensis isolates representing two distinct cox1 haplotypes, SYD.1 and Ac13 (represented by isolate SYD.2), in experimentally infected Wistar rats. For SYD.1-infected rats, only one differentially expressed gene (DEG) was upregulated in the compared to controls. In contrast, the transcriptome of SYD.2-infected rats included 100 DEGs, with enrichment of functional terms related to immune response, neuroactivity, and signalling. Faecal shedding did not differ between SYD.1- and SYD.2-infected rats, but adult worm burdens were higher in the SYD.1 group. The increased immune response in SYD.2-infected rats provides evidence that there is strain specific virulence that is pronounced in its natural host. This study provides initial parasite-specific evidence explaining why clinically affected dogs are more frequently presented with A. cantonensis haplotype Ac13.