Establishment of an Animal Model Scheme of Strongyloides stercoralis-Infected Meriones meridianus

Abstract

Studying parasitic nematodes, which generate a massive hazard to animal health, is more difficult than studying free-living nematodes as appropriate animal models are essential, and the relationship between parasites and hosts is extremely complex. Strongyloides stercoralis is an intestinal nematode parasite that mainly infects dogs, humans and other primates. Currently, S. stercoralis worms needed for research mainly rely on their natural host, the dog. This study explored a method of using Meriones meridianus as a model for S. stercoralis. The immunosuppressed M. meridianus were infected with S. stercoralis subcutaneously, and post-parasitic, first-stage larvae (PP L1) were detected in the faeces, with more larvae in female gerbils. In addition, parasitic females (PFs), third-stage larvae (L3s) and rhabditiform larvae were found primarily in the small intestines and lungs of infected gerbils. The PFs and auto-infective third-stage larvae (aL3s) obtained from M. meridianus are morphologically identical to those obtained from beagles and Meriones unguiculatus. Moreover, the infection of S. stercoralis caused changes to biochemical indicators in the serum and in the physiology of M. meridianus. The results demonstrated that M. meridianus can be infected by S. stercoralis, and this model provides a great tool for exploring the biological processes of this parasite and its interaction with the host.

Keywords: Meriones meridianus; Strongyloides stercoralis; animal model.

Figure 1

Number of post-parasitic first-stage larvae (PP L1s) of Strongyloides stercoralis recovered from faeces of female and male Meriones meridianus. There was no difference in the number of worms between the faeces of male and female M. meridianus. The abscissa is the time of sampling, and the ordinate is the number of larvae per gram of faeces. Three gerbils were used in each group.

Figure 2

Strongyloides stercoralis within the tissues of Meriones meridianus. (A) Parasitic female (PF), third-stage larvae (L3s) and rhabditiform larvae (L1 + L2) were isolated from Meriones meridianus infected with S. stercoralis. Meriones meridianus infected with 1000 iL3s were dissected 21 days after the infection, and 126 PF, 1120 L3 and 2842 rhabditiform larvae were isolated from the gerbil. (B) Distribution of S. stercoralis in the intestine of M. meridianus. HE staining shows that adult worms were observed and several eggs were present in the adult gonad. Red arrow: eggs inside the parasitic female (PF), Bar = 100 μm.

Figure 3

Morphological characteristics of a parasitic female (PF) and auto-infective third-stage larva (aL3) of Strongyloides stercoralis collected from an infected Meriones meridianus, Meriones unguiculatus and beagle. Differential Interference Contrast (DIC) of a PF and an aL3 of S. stercoralis. (A,A’) A PF worm from M. meridianus and the magnified display of its anterior end and tail. (B,B’) An aL3 larva from M. meridianus and the magnified display of its tail. (C,C’) An iL3 larva from M. meridianus and the magnified display of its tail. (D–F) PF, aL3 and iL3 from M. unguiculatus. (G–I) PF, aL3 and iL3 from a beagle. P: pharynx; E: egg; A: anterior end; T: tail; M: mouth; V: vulva. Bar = 100 μm.