Opisthorchis spp. (O. viverrini, O. felineus) - Microscopic exam;; Molecular diagnosis (PCR); Species identification (PCR and sequencing).


Opisthorchis is a genus of platihelmintos tr ematodos the order Opisthorchiida, family Opisthorchiidae that affects people and mammals that feed on freshwater fish (fish - eating mammals). Your infection can lead to a carcinogenic process, so have called Carcinogenic flukes. The genus includes species Opisthorchis Opisthorchis viverrini, O. felineus, Opisthorchis gomtii and Opisthorchis parasiluri. From the point of view of human medicine the most important species are Opisthorchis viverrini and O. felineus, causing opisthorchiasis (similar to clonorchiasis for the infection of Clonorchis sinensis disease). Infection with this parasite, is endemic in Southeast Asia, mainly in Thailand, Lao People 's Democratic Republic, Cambodia and Vietnam, and also in Japan, China, and Taiwan.

In its adult stage, this parasitic trematode has a typical oval shape of the staves and grow up to 1.5 cm long and 0.7 cm wide. Cuticle does not have spicules. Eggs are oval, approximately 20-30 microns long and 15 microns in diameter, brown and opercula.

Opisthorchis biological cycle implies a definitive host where the adult worms, sexually mature, and two intermediate hosts (first and second), usually of the genus Bithynia aquatic snails and fish species fresh water, respectively. In the definitive host when the adult worms are mature, they expel eggs through feces and should reach the water, where they arrive and embryonated. Once in the water ingested by snails (first intermediate host), in which the phases of redias develop and after immature cercariae. After leaving the snail, cercariae remain in the water and are ingested by the fish, which encyst in connective tissue or muscle, as metacercariae.

Transmission occurs through ingestion of undercooked fish or smoked freshwater who are infected by the larval form of the parasite metacercaria. Fish that act as hosts secondary intermediaries are freshwater fish, which are sometimes found is river estuaries, the Ciprinidae Family (tents) When the definitive host ingests infected with metacercariae fish, they release the larval form that parasitize the liver of people or animals that act as definitive hosts, localized mainly in the bile, hepatic and pancreatic ducts and the gallbladder, although some species are also located in the gastrointestinal tract.

In animals, the infection can cause Opisthorchis enteritis and diarrhea, as well as damage to the liver and pancreas. In some cases, the infection goes without developing signs or symptoms. Severe cases are usually rare.

Infected people express some general symptoms including dyspepsia, fatigue, pain in the right upper quadrant, increasing the size of gallbladder imaging tests. Because adult worms lodge in the liver bile ducts, causes inflammation and fibrosis of surrounding tissues. When the infection is severe and chronic, patients present manifestations of some of the following processes: cholangitis, biliary coleecistitislitiasis, periportal fibrosis, obstructive jaundice, or even develop a biliary ductal cancer (cholangiocarcinoma). This type of carcinoma is potentially fatal. For this reason, Opisthorchis viverrini is classified as a carcinogen that can cause liver carcinoma. You should think of this parasitosis in patients with symptoms compatible resident in these countries, or who have traveled to such areas and have commented consumed uncooked fish or in indigenous patients who have consumed these imported uncooked fish.


Recommended tests for diagnosis:


The routine diagnosis is based on detection of eggs in the feces of the definitive host (eg humans or animals). Of the various methods for detecting the presence of helminth eggs in feces, the Kato-Katz method is of the recommended method. This method allows to know the intensity of infection. However it is a method with low sensitivity especially in light infections. This method also differentiates infection Opisthorchis viverrini, infection by other small flukes that eliminate eggs of similar size and morphology (oval and opercula), such as infection by Clonorchis sinensis or haplorchis taichui, so only you can find out how Opisthorchis - like eggs. This group of small trematode worms known as WIM: Minute Intestinal Flukes). To differentiate these species eggs one concentration method Telleman and then stained with iodine, potassium permanganate or methylene blue must be performed. However, because eggs are eliminated in feces intermittently, microscopic examination for eggs, can give false negative results. Another drawback is that microscopic examination experience required by the personnel performing microscopic observations. An alternative to know with certainty the infecting species is observed adults. This can be treated the patient with praziquantel (treatment of choice), and administering an oral laxative, to allow an examination of diarrheal stool for adults.

In addition, DNA can be detected in the faeces by molecular diagnostic methods (PCR) and species identification by sequencing. PCR tests have high specificity and sensitivity in cases of moderate or severe infections with more than 1,000 eggs per gram of faeces, but sensitivity decreases in infections with less than 1,000 eggs per gram of feces.

Tests in IVAMI:


  • Microscopic examination of eggs in feces.
  • Molecular diagnosis (PCR), to detect DNA Opisthorchis spp.
  • Molecular identification of species (sequencing).

Recommended sample:


  • Feces.


Preservation and shipment of sample:


  • Refrigerated (preferred) for less than 2 days.
  • Frozen: more than 2 days (for molecular diagnostics).


Delivery term:


  • Microscopic examination of stool: 24 hours.
  • Molecular diagnosis (PCR): 24 to 48 hours.
  • Molecular species identification (sequencing): 72 to 96 hours.

Cost of the test:

Consult ivami@ivami.com