Foodborne trematode infections

Fascioliasis diagnosis, treatment and control strategy

Diagnosis

Diagnosis of fascioliasis may be suspected on the basis of the clinical picture, on the anamnestic recall of consuming raw vegetables, on the detection of eosinophilia (blood eosinophil count >500–1000 per μl of blood), and on typical findings at ultrasound or computed tomography scans. Confirmation relies on different types of diagnostic techniques.

  • parasitological techniques to detect Fasciola eggs in stool samples; their cost and sensitivity may vary according to the type used; they can only be employed in the chronic phase; some of them allow quantifying intensity of infection (therefore estimating the severity of the infection);
  • immunological techniques to detect worm-specific antibodies in serum samples or worm-specific antigens in serum or stool samples; they are usually more sensitive than the commonly used parasitological techniques; detection of antibodies does not allow distinguishing between current, recent and past infections; their ability to quantify intensity of infection is disputed; stool tests are easier to perform and reportedly better accepted by individuals in endemic areas;
  • molecular techniques such as the polymerase chain reaction are still at experimental stage.

NB: Since fascioliasis is mainly prevalent in developing countries, the quality of diagnostic techniques is as important as their affordability and applicability in field settings.

Treatment

Triclabendazole, the only medicine recommended by WHO against fascioliasis, is active against both immature and adult parasites, and may therefore be employed during the acute and chronic phases. Cure rates are high , while adverse reactions following treatment are usually temporary and mild. The recommended regimen is 10 mg/kg body weight administered as a single dose in both clinical practice and preventive chemotherapy interventions. In clinical practice, where treatment failure occurs, the dosage may be increased to 20 mg/kg body weight in two divided doses 12-24 hours apart.

Control through triclabendazole

From a public health perspective, control of human fascioliasis mainly relies on timely treatment with triclabendazole, a measure that cures infected individuals and prevents development of advanced morbidity.

In areas where cases of fascioliasis occur sporadically, clinical case management of individuals reporting to their local hospital is sufficient to tackle the disease. Diagnostic protocols adapted to the socioeconomic environment of endemic areas should be adopted, and triclabendazole should be made available to peripheral health centres with the aim of increasing access to treatment.

In communities where cases are clustered, possibilities for implementing large-scale anthelminthic distribution (preventive chemotherapy) in subdistricts, villages or communities where the cluster occurs should be considered. Preventive chemotherapy in such foci can be implemented as targeted treatment of school-age children (5–14 years), usually the population with the highest prevalence and intensity of infection, or as universal treatment (mass drug administration, or MDA) of the entire resident population. In such areas, individual-level diagnosis is not necessary; decisions about treatment are rather based on an assessment of the public health relevance of the disease.

A number of countries are implementing control of fascioliasis through use of triclabendazole. The examples below show some of the different approaches implemented:

  • individual case-management following a simplified diagnostic protocol (in Viet Nam);
  • mass screenings in suspect areas followed by treatment of positive cases (in Egypt);
  • targeted treatment of high-risk population groups, particularly children, living in endemic areas (in Bolivia (Plurinational State of));
  • MDA to entire communities identified as highly endemic (in Peru).
Complementary public health interventions

Timely treatment with triclabendazole is the quickest way to control morbidity associated with fascioliasis. However, treatment should be complemented, where feasible, by implementing measures that aim to reduce transmission rates, including:

  • information, education and communication, promoting cultivation of vegetables in water free from faecal pollution and thorough cooking of vegetables before consumption;
  • veterinary public health measures, including treating domestic animals and enforcing separation between husbandry and humans;
  • environmental measures such as containment of the snail intermediate hosts and drainage of grazing lands.
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