Trematode Ppt

[Juliane Bari]

Inall species, the first intermediate host is a freshwater snail. The second host differs according to species: for Clonorchis and Opisthorchis it is a freshwater fish and for Paragonimus it is a crustacean. Infection with\r\n Paragonimus spp can also result from the consumption of animals that feed on crustaceans e.g. raw wild boar meat. Fasciola spp. do not require a second intermediate host and can infect humans via the consumption of contaminated freshwater\r\n plants. The final host is always a mammal (Table 1).

Within countries, transmission is often restricted to focal areas and reflects behavioural and ecological patterns. Inadequate sanitation and food hygiene, limited access to safe drinking water, and cultural food preferences are all associated with an\r\n increased risk of infection. Cultural food sharing habits may also contribute to familial and community clusters of infection.

The true burden associated with these infections is unclear as public health awareness and availability of health facilities is often limited in affected populations. Estimates from the WHO Foodborne disease burden Epidemiology Reference Group (FERG)\r\n (2015) identified the 4 species of food borne trematodes as important causes of disability with an estimated annual total of 200 000 illnesses and more than 7 000 deaths per year, resulting in more than 2 million disability-adjusted life years globally.\r\n

The added economic impact of foodborne trematodiases is significant and is linked to losses in the livestock and aquaculture industries due to reduced animal productivity, as well as to restrictions on exports and reduced consumer demand.

The public health burden due to foodborne trematodiases is predominantly due to morbidity rather than mortality with early and light infections often going unnoticed. Chronic infections are associated with severe morbidity with symptoms reflecting the\r\n organ in which the adult worms are located in.\r\n

Acute infection with Opisthorchis spp and Clonorchis sinensis may be asymptomatic in light infections but clinical symptoms such as fever, right upper-quadrant pain may be seen with high parasite burdens due to obstruction of the gallbladder\r\n by the worm. Chronic infection from O. viverrini and C. sinensis resulting from protracted episodes of re-infection over time may be most severe, with chronic inflammation resulting in fibrosis the ducts and destruction of the adjacent\r\n liver parenchyma. These changes can result in cholangiocarcinoma, a severe bile duct cancer which is often fatal. For this reason, both O. viverrini and C. sinensis are classified as carcinogens. Data on chronic infections with O. felineus is sparse, and this parasite is not classified as a carcinogen.

Fascioliasis consists of an asymptomatic incubation period following ingestion of the parasite which is then followed by an acute and a chronic clinical phase. The acute phase of Fasciola infection begins when the immature worms penetrate the\r\n intestinal wall and peritoneum then puncture the liver surface and travel to the bile ducts. This process results in destruction of liver cells and causes internal bleeding. Symptoms can include fever, nausea, swollen liver, skin rashes and severe\r\n abdominal pain. The chronic phase begins when the worms reach the bile ducts, mature and start producing eggs. These eggs are released into the bile then reach the intestine before being evacuated in faeces. Symptoms can include intermittent pain,\r\n jaundice, anaemia, pancreatitis and gallstones. Chronic infections result in liver cirrhosis due to long-term inflammation.\r\n

Early stages of paragonimiasis may be asymptomatic. Once worms reach the lungs symptoms can be significant and include a chronic cough with blood stained sputum, chest pain, dyspnoea, and fever, and can result in complications of pleural effusion and\r\n pneumothorax. Symptoms and signs can be confounded with tuberculosis and should be considered in suspected tuberculosis patients that are not responding to treatment. Ectopic paragonimiasis is also common with cerebral paragonimiasis being most common.\r\n Symptoms associated with this include headaches, visual impairment, epileptic seizures and cerebral haemorrhage.

Foodborne trematodiases is suspected on the basis of the clinical picture, history of appropriate risk factors (consumption of raw fish, crustaceans, uncooked freshwater plants), detection of eosinophilia and typical findings on ultrasound, computed tomography\r\n (CT) or magnetic resonance imaging (MRI) scans. Confirmation of the diagnosis relies on different diagnostic techniques.

Control of foodborne trematodiases aims to reduce the risk of infection and control associated morbidity. An integrated One Health approach which links animal, human and environmental aspects should be used. Interventions such as information, education\r\n and communication on safe food practices, improved sanitation and veterinary public health measures should be implemented to decrease transmission rates and reduce risk of infection.

For the purposes of public health control, WHO recommends carrying out community diagnosis at the district level and implementing population-based preventive chemotherapy in areas where large number of people are infected. Individual case-management with\r\n treatment of people with confirmed or suspected infection is appropriate where cases are less clustered and where health facilities are available.

Preventive chemotherapy alone is insufficient to reduce prevalence. Factors such as poor sanitation and food hygiene, animal reservoirs and cultural eating habits contribute to high reinfection rates after treatment. As such, mass drug administration\r\n programmes should be part of a wider One Health approach incorporating community health education, veterinary and agricultural interventions, food safety and improved water, sanitation and hygiene.

In all species, the first intermediate host is a freshwater snail. The second host differs according to species: for Clonorchis and Opisthorchis it is a freshwater fish and for Paragonimus it is a crustacean. Infection with Paragonimus spp can also result from the consumption of animals that feed on crustaceans e.g. raw wild boar meat. Fasciola spp. do not require a second intermediate host and can infect humans via the consumption of contaminated freshwater plants. The final host is always a mammal (Table 1).

Within countries, transmission is often restricted to focal areas and reflects behavioural and ecological patterns. Inadequate sanitation and food hygiene, limited access to safe drinking water, and cultural food preferences are all associated with an increased risk of infection. Cultural food sharing habits may also contribute to familial and community clusters of infection.

The true burden associated with these infections is unclear as public health awareness and availability of health facilities is often limited in affected populations. Estimates from the WHO Foodborne disease burden Epidemiology Reference Group (FERG) (2015) identified the 4 species of food borne trematodes as important causes of disability with an estimated annual total of 200 000 illnesses and more than 7 000 deaths per year, resulting in more than 2 million disability-adjusted life years globally.

The public health burden due to foodborne trematodiases is predominantly due to morbidity rather than mortality with early and light infections often going unnoticed. Chronic infections are associated with severe morbidity with symptoms reflecting the organ in which the adult worms are located in.

Acute infection with Opisthorchis spp and Clonorchis sinensis may be asymptomatic in light infections but clinical symptoms such as fever, right upper-quadrant pain may be seen with high parasite burdens due to obstruction of the gallbladder by the worm. Chronic infection from O. viverrini and C. sinensis resulting from protracted episodes of re-infection over time may be most severe, with chronic inflammation resulting in fibrosis the ducts and destruction of the adjacent liver parenchyma. These changes can result in cholangiocarcinoma, a severe bile duct cancer which is often fatal. For this reason, both O. viverrini and C. sinensis are classified as carcinogens. Data on chronic infections with O. felineus is sparse, and this parasite is not classified as a carcinogen.

Fascioliasis consists of an asymptomatic incubation period following ingestion of the parasite which is then followed by an acute and a chronic clinical phase. The acute phase of Fasciola infection begins when the immature worms penetrate the intestinal wall and peritoneum then puncture the liver surface and travel to the bile ducts. This process results in destruction of liver cells and causes internal bleeding. Symptoms can include fever, nausea, swollen liver, skin rashes and severe abdominal pain. The chronic phase begins when the worms reach the bile ducts, mature and start producing eggs. These eggs are released into the bile then reach the intestine before being evacuated in faeces. Symptoms can include intermittent pain, jaundice, anaemia, pancreatitis and gallstones. Chronic infections result in liver cirrhosis due to long-term inflammation.

Early stages of paragonimiasis may be asymptomatic. Once worms reach the lungs symptoms can be significant and include a chronic cough with blood stained sputum, chest pain, dyspnoea, and fever, and can result in complications of pleural effusion and pneumothorax. Symptoms and signs can be confounded with tuberculosis and should be considered in suspected tuberculosis patients that are not responding to treatment. Ectopic paragonimiasis is also common with cerebral paragonimiasis being most common. Symptoms associated with this include headaches, visual impairment, epileptic seizures and cerebral haemorrhage.

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