RESUMO
Infection by the zoonotic fish-borne trematode, Opisthorchis viverrini, remains a crucial health issue in Thailand and neighboring countries. Recently, molecular analysis revealed two populations of putative O. viverrini: one found primarily in human hosts ("human-specific" population) and the other primarily in cats ("cat-specific" population). It is unclear how the infective stages (metacercariae) of these different populations circulate among definitive and reservoir hosts in nature. To gain an insight into this, mitochondrial cox1 and nad1 gene sequences of metacercariae from fish intermediate hosts were examined. None of 192 metacercariae from cyprinid fish in Lao PDR and Thailand had sequences typical of "cat-specific" O. viverrini, suggesting that cyprinid fish are not the main second intermediate hosts of this population. Interestingly, all 20 O. viverrini-like metacercariae from snakehead fish (Channa striata) shared 99.51-100% sequence identity with eggs from cats naturally infected in a previous study. Hence, we propose a modification of the known transmission dynamics of O. viverrini: consumption of metacercariae within snakehead fish provides another pathway for cats and (occasionally) humans to acquire infection. We also performed morphological comparisons of eggs, metacercariae, and adult flukes (raised in hamsters) of both Opisthorchis populations. The "cat-specific" population has eggs that are narrower and adults that are shorter and wider than in the human-specific population. The metacercaria of the "cat-specific" population is elliptical, while that of the "human-specific" population is oval, occasionally rounded. Our results confirmed that O. viverrini-like metacercariae from snakehead fish are the infective stages of the "cat-specific" fluke. This provides a new insight into the dissemination and transmission of each population in the second intermediate host. The identity of the cat-specific population is discussed.
Assuntos
Doenças dos Peixes , Opistorquíase , Opisthorchis , Animais , Opisthorchis/genética , Opisthorchis/classificação , Opisthorchis/fisiologia , Opisthorchis/anatomia & histologia , Opisthorchis/isolamento & purificação , Gatos , Humanos , Tailândia , Opistorquíase/parasitologia , Opistorquíase/veterinária , Opistorquíase/transmissão , Doenças dos Peixes/parasitologia , Doenças dos Peixes/transmissão , Filogenia , Metacercárias/genética , Metacercárias/anatomia & histologia , Metacercárias/isolamento & purificação , Laos , Doenças do Gato/parasitologia , Doenças do Gato/transmissão , Cyprinidae/parasitologia , Complexo IV da Cadeia de Transporte de Elétrons/genética , Análise de Sequência de DNA , Dados de Sequência Molecular , DNA de Helmintos/genética , NADH Desidrogenase/genéticaRESUMO
Mucin plays a crucial role in safeguarding mucosal tissues by obstructing the translocation of microorganisms. Mucosal tissue-dwelling parasites must devise a strategy to surmount this mucin barrier in order to establish colonization. In a recent discovery, it was observed that the liver fluke Opisthorchis viverrini secretes two mucinases, namely Ov-M60-like-1 and Ov-M60-like-2. Ov-M60-like-1 was previously characterized. Here, we study the Ov-M60-like-2 by utilizing the wheat germ expression system to produce recombinant proteins and conducted a functional analysis of its enzymatic activity on bovine submaxillary mucin (BSM). Subsequently, we delved deeper into understanding the role of this enzyme in host-parasite interactions by evaluating its mucinase activity on mucins from the bile duct of O. viverrini-infected hamsters. Through successful production of recombinant proteins using the wheat germ expression system, we observed that this enzyme displayed mucinase activity over a wide pH range (pH 2 to pH 10) against BSM. Our investigations revealed it ability to digest mucin from the bile duct. These findings suggest that Ov-M60-like-2 possess a mucinase activity, together with Ov-M60-like-1, enabling the liver fluke to successful colonization of the host's bile duct.