[Detection and identification for Gnathostoma sp. in imported Monopterus albus]
Objective:
To inspect the third stage larvae of Gnathostoma in imported Monopterus albus, and identify its species.
Methods:
Ten batches of M. albus imported to Shanghai were detected for nematode Gnathostoma from January 2010 to March 2011. Fifty-two M. albus imported from the Philippines (25), Indonesia (24) and Bangladesh (3) were sampled (3-10/batch), which were dissected, minced, and digested. The suspension was filtered with 10 mesh screen to take the deposit. The complete parasites were picked out under stereoscope followed by morphological identification. The rate and intensity of infection were calculated. Genomic DNA of Gnathostoma was extracted to amplify internal transcribed spacer region 2 (ITS-2) and cytochrome C oxidase subunit 1 (cox1) by PCR, the product of which was analyzed by electrophoresis and sequencing. The sequences were aligned with corresponding sequences in GenBank.
Results:
The third stage larvae of Gnathostoma were detected in M. albus from Indonesia and Philippines with infection rate of 36.0% (9/25) and 50.0% (12/24) and average infectiosity of 7.8 (70/9) and 2.8 (34/12), respectively. No Gnathostoma was found in M. albus imported from Bangladesh. Under microscope, the larvae showed one cephalic bulb with 4 rings of hooklets on it, cross striations and small spines on the body surface. The front body spines were bigger and denser, while the rear spines were smaller and sparser. It had 1 cervical papilla and 4 cervical capsules. Morphological characteristics were similar to the third stage larvae of G. spinigerum. PCR results showed that the length of the ITS-2 and cox1 PCR products was 647 bp and 441 bp, respectively. Sequence alignment analysis showed that the two PCR products had 99%-100% consistency with G. spinigerum ITS-2 (GenBank Accession No. AB181155 and Z97175) and cox1 (GenBank Accession No. AY501388, AB180099, and AB551552).
Conclusion:
All the larvae detected in M. albus imported from the Philippines and Indonesia have been identified as G. spinigerum.
