ABSTRACT
This study, undertaken as a component of the global Dracunculiasis Eradication Program (DEP), was designed to provide molecular tools to distinguish Dracunculus medinensis, the nematode causing human dracunculiasis, from other tissue-dwelling nematodes, including other Dracunculus species that infect humans and other animals. DNA was extracted from D. medinensis and from a closely related species that infects North American carnivores, D. insignis, so that the genes coding for the small-subunit ribosomal RNA (18S rRNA) of the parasites could be amplified, sequenced and compared. Sequences were obtained for 20 specimens of D. medinensis (from humans in Pakistan, Yemen and six African countries endemic for dracunculiasis) and three of D. insignis (from raccoons trapped in the state of Georgia in the southern U.S.A.). All of the D. medinensis 18S-rRNA sequences were found to be 1819 bases long and identical. The three D. insignis 18S-rRNA sequences were also found to be identical to each other but were 1821 bases long and differed from the D. medinensis 18S- rRNA sequence at eight positions (representing a difference of 0.44%). The 18S-rRNA coding region of a Guinea worm extracted from a dog in Ghana was indistinguishable from that of the D. medinensis isolates from human cases. These results provide the basis for the molecular differentiation of D. medinensis that will permit the DEP to determine, rapidly and accurately, whether a worm recovered from an area considered dracunculiasis-free is a specimen of D. medinensis or not.
Subject(s)
Dracunculiasis/parasitology , Dracunculus Nematode/genetics , Genes, Helminth/genetics , RNA, Ribosomal, 18S/genetics , Animals , Base Sequence , DNA Primers/genetics , Humans , Phylogeny , Polymerase Chain Reaction/methods , RNA, Helminth/genetics , Species SpecificityABSTRACT
The results of analysis, by high-performance liquid chromatography coupled with electrochemical detection and by nano-electrospray-ionization, double quadrupole/orthogonal-acceleration, time-of-flight mass spectrometry, indicate that adult Dracunculus medinensis and Schistosoma mansoni both contain the opiate alkaloid morphine and that D. medinesis also contains the active metabolite of morphine, morphine 6-glucuronide. From these and previous observations, it would appear that many helminths are probably using opiate alkaloids as potent immunosuppressive and antinociceptive signal molecules, to down-regulate immunosurveillance responsiveness and pain signalling in their hosts.
