Taenia solium Taeniasis

1. Taenia solium Taeniasis / Cysticercosis Felipe Fregni

2. Questions What are the different forms of disease presentation in humans and how this contributes to the epidemiology of this disease? Although cysticercosis is related to extreme poverty, why the incidence of this disease is low in some poor areas, such as the northeast of Brazil? What are the important characteristics of the human carriers of t. solium that determine the persistence of the infection? Is eradication possible? What are the difficulties to implement a control program for cysticercosis? Is this disease only a consequence of extreme poverty?

3. Basics (1) Complex two-host life cycle Human beings are the only definitive host (small intestines - 2-4 meters long -800-1000 segments) Both humans and pigs can act as intermediate hosts (larvae or cysticerci) Most common in Latin America, Africa and India - 400,000 people have symptomatic neurocysticercosis in Latin America

6. Basics of the infection cycle Faecal-borne infection Tapeworm larval cyst (cysticercus) is ingested with poorly infected meat Larva escapes the cyst and attaches to the mucosa by the scolex Feces are contaminated with eggs (persist for several days in the environment) - consumed by pigs (eggs are hatched and form cysticerci Humans are the only definitive host Pigs - intermediate host (cysticercal stage) However; Humans - also can be the intermediate host - causing cysticercosis (neurocysticercosis) if they ingest eggs

9. Human infection - teniasis The scolex attaches to the mucosa and begins forming segments (proglotidds) After 2 months of infection, gravid proglottids begin to detach from the distal end - excreted in the feces Each segment contains 60,000 eggs Worm causes only minor inflammation to the intestine (mild symptoms - abdominal pain, distension, diarrhea and nausea - or none at all)

10. Human infection - cysticercosis Faecal-oral contamination with T. solium eggs from tapeworm carriers Internal autoinfection is also possible The invasive oncosphere (embryos) in the eggs are liberated by the action of gastric acid and cross the bowel wall (remember - cysticerci are too big to cross the bowel wall) They establish at small terminal vessels (muscles, brain, eye) where they grow of about the size of 1 cm in 2-3 months

11. Human cysticercosis Muscle - small, palpable, movable nodules - chests and arms - mild or no symptoms Ophtalmic cysticercosis - intraocular cysts floating freely in the vitreous humor - decreased visual acuity Neurocysticercosis - most symptoms are because of the inflammatory reaction associated with cyst degeneration (that may take years to happen) - epilepsy, hydrocephalus, encephalitis, meningitis

16. Diagnosis - teniasis Visualization of taenia eggs was the only diagnosis until recently - has poor sensitivity and difficult to differentiate from taenia saginata. Best diagnosis - coproantigen detection ELISA (detect taenia specific molecules in the feces - 95% sensitivity and 99% specificity) Options: not efficient and cheap test vs. efficient and expensive test

17. Diagnosis - cysticercosis Depends on the targeted organ: CNS - CSF immunology, neuroimaging (the scolex can be seen) Muscle - imaging, bx Eye - imaging (ultrasound) (serological exam - ELISA)

18. Treatment - teniasis Teniasis - relatively easy for intestinal disease - PO drugs - niclosamide and praziquantel. niclosamide is the choice as it is not absorbed; however, it is an expensive drug

19. Treatment - cysticercosis Neurocysticercosis is the main problem The problem of the cyst is the inflammatory reaction Use of parasiticide - debatable - aim is to reduce inflammation and scar tissue palliative treatment to control inflammation - corticosteroids, anti-histaminics

20. Treatment for pigs? Advantage - remove established infection and avoid economic losses at slaughter - diagnosis with tongue palpation Drugs do not lead to complete parasite elimination Drug residuals in pigs - is it safe? Vaccination for pigs: issues (i) appropriate formulation; (ii) production of a stable vaccine; (iii) understanding of efficacy; (iv) price

21. Epidemiology Affect millions of individuals - 2.5 million people worlwide carry the T. solium and 20 million are infected with the cysticerci Endemic villages - up to 25% are seropositive and 10-18% have CT findings suggestive of neurocysticercosis

22. Latin America and Brazil Average seroprevalence in Latin America is 10% Brazil estimates of 3 - 5.6% Human neurocysticercosis - estimates of 7% (Latin America) Swine cysticercosis - 17% of prevalence (Latin America)

23. Control of taeniasis and cysticercosis Pigs: Dommestic pig raising, tanieasis and human cysticercosis are intimally related - pigs are chep and easily marketable - convenient source of meat or money Pigs also eat pasture and garbage Endemic regions - 30-60% of pigs are infected

24. T solium is transmitted mainly in rural areas where pigs have access to untreated sewage or faeces and infected pork is widely available Tapeworm carriers and human porcine cysticercosis cluster in endemic areas In endemic areas, late onset epilepsy is a strong predictor for neurocysticercosis Autoinfection may play an important role Immunodiagnostic tests - show past exposure Human carriers: those living in rural areas in contact with pigs vs. those living in urban areas with no access to pigs but playing a role as a source of neurocysticercosis

25. OPEN TO DISCUSSION How to control taeniasis/cysticercosis? Potential difficulties for implementation?

26. AFTER THE DISCUSSION Methods for controlling taeniasis/cysticercosis Pig vaccination Pig treatment Human carriers mass treatment Health education

27. IMPORTANT: infected pigs and tapeworm carriers Abbatoir inspection and confiscation - however pigs are killed clandestinely in many areas and also misses mild infections Detection and treatment of tapeworm carriers or mass treatment (single dose - mild adverse effects) Treatment of pigs (relatively low efficacy and costs) Vaccines??

28. Mass treatment Pros - single dose, PO Cons - cost and acceptance Who to treat? Infection focus - any locality with a high prevalence of cysticercotic pigs? Any farm supplying cysticercotic pigs? Any patient with late onset epilepsy? Any case of detected or propable teniasis?

29. Health education Association of cysticercosis prevalence and insanitary rearing of pigs, inability to recognize infected pigs and insuficient knowledge of transmission Education: hand washing, defecating in fields, corralling of pigs Ex. Community in Mexico - although almost everybody could identify cysticercosis in pigs, only 0.7% knew how pigs were infected

30. Past experiences - health education Study in two rural communities (3000 inhabitants each): Community A - health education only Community B - health education and mass treatment (health education - promoted knowledge of transmission of taeniasis/cysticercosis, improved hygiene and sanitation) RESULTS - Community A Swine cysticercosis rate: Before: 2.6, 5.2, 4.8 (lingual examination, antibody detection and postmortem examination) After - 0, 2 and 0% (respectively) Human infection (coproantigen test): 0.78, 0.51 and 0.41% (before, one year later and after 42 months RESULTS - Community B Swine cysticercosis rate: Before: 4.1, 7.5, 9.3% After - 0.7, 3.2, 0.9% Human infection (coproantigen test): 0.79, 0.97 and 0.7%

31. Eradication Pros: human is the only carrier, there a relatively simple treatment Other issues: 1) Technical - lack of a simple diagnosis, lack of an easily available treatment (costs) 2) Societal: poor community cooperation and sanitary education 3) Political: low priorities and debatable strategy CDC - eradication cannot be achieved in the near future - only regional elimination

32. Difficulties to implement control programs (i) Taeniasis in humans may go unnoticed (ii) Taeniasis is also a mild infection, which does not prompt the carrier to get rid of a tapeworm even when it is diagnosed. (iii) Traditional laboratory diagnosis of tapeworm infection in humans has poor accuracy and other modern coproantigen tests have not been introduced to the market and are expensive (iv) Treatment rates are frequently low -appropriate medicines are not available in many endemic areas (v) Several human behavioral factors - traditional preferences for raw pork consumption and indiscriminate, unsanitary defecation, (vi) Inadequate local levels of information on taeniasis/cysticercosis (vii) There is clear economic motivation for small scale pork producers to minimize commercial losses associated with infected carcass condemnation at official slaughter

33. Political will The public health impact of human cysticercosis in some regions is serious (significant social and financial costs) Neurocysticercosis can potentially affect any person (rural or urban area) Contamination with eggs can also be common in urban centers Control measures can be implemented regionally Efficacy of schemes can be measured in sentinel or slaughtered pigs

34. Economic factors Pig production has doubled in the last 20 years in Africa Owners usually detect infection in vivo and them sell these cheaper pigs to unofficial slaughter houses or kill them at home

35. Is this disease only a consequence of poverty? Eradication of extreme poverty - would reduce subsistence pig rearing Achievement of universal primary school education - increase knowledge about risky behaviors in relation to T. solium transmission Gender equality and empowering women - decrease risk of taenia infection at home - reducing consumption of contaminated meat and personal hygiene Combating major infection diseases Improvement of sanitation