Helminthic Diseases

  • Helminths are animals that belong to the phyla Platyhelminthes and Nematoda (Nemathel- minthes).
  • Many parasitic forms of this group, popularly known as parasitic worms, are endoparasites of gut and blood in human body and cause various diseases called as helminthiasis.

Taeniasis

  • Taeniasis is caused by Taenia solium (pork tapeworm) and Taenia saginata (beef tapeworm).
  • The adult parasites reside in the small intestine of human beings (primary host) and their larvae infest the muscles of the pig mostly (secondary host).

Mode of transmission

  • Human beings get infected by eating raw and inadequately cooked measly pork or beef containing cysticerci of tapeworm.

Symptoms

  • Taeniasis can be recognised by abdominal pain, nausea, anaemia, insomnia, increased appetite and indigestion. It results in increase of eosinophil cells in blood and nervous disorders like epilepsy.
  • While the hooks and suckers cause mechanical obstruction in the intestine, the toxins released by the tapeworm bring about the above-mentioned symptoms.

Prevention and treatment

  • This disease can be prevented if the pork / beef is fully cooked before eating and the faecal matter of infected human beings is destroyed in pits.
  • Camoquin and atabrin are effective in treating the disease.

Cysticercosis

  • Cysticercosis is caused by cysticercus (a larva of tape worm).
  • Cysticercus develops from another larva called onchosphere. The onchospheres reach the intestine where they develop into cysticerci.

Mode of transmission

  • Humans become infected on ingesting tapeworm eggs in contaminated food or drink.

Symptoms

  • The presence of cysticerci in the muscles causes pain and weakness; in the brain the symptoms are more serious, including mental deterioration, paralysis, giddiness, epileptic attacks, and convulsions, which may be fatal.

Prevention and treatment

  • One should avoid having contaminated food or drinks.
  • Praziquantel (PZQ) and albendazole are used to treat cysticercosis.

Fasciolopsiasis

  • Fasciolopsiasis disease is caused by the intestinal fluke Fasciolopsis fuelleborni in India. Snail acts as the intermediate host of this parasite.

Mode of transmission

  • Infection is acquired by eating infected water plants, particularly the water nuts, with metacercariae larvae.

Symptoms

  • The worms cause erosion of intestinal lining causing bleeding and pain. Diarrhoea, nausea and vomiting follow later.

Prevention and treatment

  • One should avoid eating infected water plants particularly water nuts.
  • Praziquantel and tetrachloroethylene are helpful in the eradication of these intestinal flukes.

Schistosomiasis

  • Blood flukes. Schistosoma mansoni, S. japonicum and S. haematobium cause this disease.

Mode of transmission

  • Infection is through the penetration of skin of man by the cercariae larvae which swim freely in water. Through blood circulation, cercariae reach lungs to become adult worms. Adults then get into blood stream.

Symptoms

  • Blood flukes cause asthmatic attacks, hepatitis, fever, sweating, diarrhoea, weight loss and lack of

appetite.

Prevention and treatment

* Sanitary disposal of all human faeces and urine are the preventive measures.

  • Antimony compounds are recommended for treatment.

Hydatid disease

Hydatid disease is caused by Echinococcus granulosus (the dog tapeworm or hydatid worm). It lives as an endoparasite in the intestine of dogs, cats, foxes and man.

Mode of transmission

  • Man acquires infection on eating food or drinking water contaminated with onchosphere – containing eggs.

Symptoms

  • The parasite liberates toxins which have harmful effect on the body and brain of the host.

Prevention and treatment

  • One should avoid having contaminated food or drinks.
  • The treatment of hydatid disease is same as that of taeniasis.

Opisthorchiasis (= Clonorchiasis)

  • Opisthorchiasis is caused by Opisthorchis (= Clonorchis) sinensis which inhabits the bile ducts.

Mode of transmission

  • Humans are infected by eating raw or under cooked fish which harbour metacercariae.

Symptoms

  • Adult flukes are found in biliary ducts, causing the thickening of duct walls, cirrhosis, and ultimately death.

Paragonimiasis

  • Paragonimiasis disease is caused by the lung fluke, Paragonimus westermani, found in lungs in encapsulated form.

Mode of transmission

  • Man acquires infection by eating raw or under-cooked crabs and crayfish infected with metacercarial cysts.

Symptoms

  • Lung flukes cause chronic cough with emission of bloody sputum. Heavy infections cause chest pain with pleurisy, shortness of breath, fever and anaemia.

Prevention and treatment

  • One should avoid eating raw or undercooked crabs and crayfish.
  • Emetine hydrochloride and sulpha drugs are recommended for the treatment of the disease.

Ascariasis

  • Ascariasis is caused by the common round worm Ascaris lumbricoides. It is a giant intestinal worm, white in colour with female worm longer than the male.
  • It is an endoparasite of the small intestine of human beings.

Mode of transmission

  • There is no intermediate host of the parasite, so man acquires infection by directly ingesting Ascaris eggs, with contaminated food or water.

Prevention and treatment

  • All freshwater fishes should be thoroughly cooked before eating to prevent the disease.
  • Gentian violet and chloroquine are helpful in curing this disease.

Female lays about 200,000 eggs daily that pass out with human faeces, and remain viable in the soil for several days.

It is more common in the children, because the latter are generally in the habit of eating soil and clay, which may be infected by the eggs of Ascaris.

ascariasis

Adult worms (1) live in the lumen of the small intestine. A female may produce approximately 200,000 eggs per day, which are passed with the faeces (2). Unfertilized eggs may be ingested but are not infective. Fertile eggs embryonate and become infective after 18 days to several weeks (3), depending on the environmental conditions (optimum: moist, warm, shaded soil). After infective eggs are swallowed (4), the larvae hatch (5), invade the intestinal mucosa, and are carried via the portal, then systemic circulation to the lungs (6). The larvae mature further in the lungs (10 to 14 days), penetrate the alveolar walls, ascend the bronchial tree to the throat, and are swallowed (7). Upon reaching the small intestine, they develop into adult worms (1). Between 2 and 3 months are required from the time of ingestion of the infective eggs to oviposition by the adult female. Adult worms can live 1 to 2 years.

Symptoms

  • Since a large number of adult Ascaris worms normally infest a single host, they obstruct the intestinal passage and thereby cause abdominal discomfort, like colic pains.
  • The patient may also suffer from impaired digestion, diarrohea and vomiting.
  • Worms sometimes penetrate the intestinal epithelium and reach certain vital organs like kidneys, spinal cord, brain or muscles causing injuries to the organs.
  • These worms produce toxins which cause irritation of mucous membranes, convulsions, nervousness etc.

Prevention and treatment

  • Ascariasis can be prevented by the following measures:

(i) Soil pollution, being the chief source of infection, should be prevented. People, especially children, should be made to observe sanitary habits.

(ii) Vegetables and fruits should be thoroughly washed before consumption.

(iii) Finger nails should be regularly cut to avoid accumulation of eggs below them and hands should be properly soap-washed before eating.

  • Infection can be treated with a dose of hexylresorcinol crystals in a gelatin capsule after about 12 hours of fasting.
  • Some antihelminthic drugs like oil of chenopodium, tetrachlorethylene, piperazine, hetrazan etc. are also used to treat this disease.

Filariasis (Elephantiasis)

  • Filariasis is caused by nematode, Wuchereria bancrofti (= Wuchereria = Filaria). Another species is W. malayi.
  • The adult worms are slender and a few centimetres long, males being shorter than the females.
  • Adult worms live in the lymphatic system and produce young ones called microfilariae.These are microscopic and can be seen in blood when it is collected at night and examined under a microscope.

Mode of transmission

  • The pathogen spreads from one human being to another through mosquitoes like Culex and to a lesser extent by Anopheles and Aedes.
  • When a mosquito sucks blood from an infected individual, the microfilariae which are harmless to man enter the stomach of the mosquito.
  • In about 10 to 20 days these microfilariae develop and grow to form infective larvae which now reach the mouth parts of the mosquito.
  • When an infected mosquito bites any person, the larvae are deposited on the skin from where they make their way into the skin.
  • Eventually they enter the lymphatic system where they develop into adults.

Symptoms

  • The disease passes through four stages in human beings:

(i) In the first stage, the patient has increased eosinosphils, enlarged lymph nodes and positive intraderma I parasite test.

(ii) Second or carrier stage is symptomless but the right blood examination can reveal the parasite.

(iii) Third stage is characterised by filarial fever, inflammation of lymph nodes (lymphadenitis), dilation of lymph vessels (lymphangiectasis) and reversible lymphoedema (excess fluid in tissues due to obstruction of lymph vessels) in various body parts.

(iv) The fourth or final stage is manifestated by lymphoedema accompanied by thickening of subcutaneous tissues and skin so that there is permanent swelling mostly of feet, legs, thighs, scrotal sacs, breast etc. It is called elephantiasis.

Prevention and treatment

  • The disease can be prevented by taking precautions against mosquito bites. It is also advisable to take prophylatic drugs in filaria prone areas.
  • The disease can be cured by drugs like hetrazan, albendazole and diethylcarbamazine (DEC).
  • Very large swellings can sometimes be removed by surgery.

Ancylostomiasis

  • Ancylostomiasis is caused by hook worms, Ancylostoma duodenale and Necator americanus which are parasites of the small intestine.

Mode of transmission

  • Female hookworms produce 5,000 to 10,000 eggs per day which pass out in stool.
  • Man acquires infection when eggs hatch and juveniles penetrate through soft skin of hands and feet.
  • They enter the blood vessels, and are carried to the heart and lungs, finally reaching the small intestine, where they develop into adult worms.

Symptoms

  • Gastro-intestinal disturbances, anaemia and nervous disorders are the characteristics of the disease.
  • Patient appears pale and weak; nausea and vomiting are also frequent. In severe cases, men become impotent and women cease to menstruate.

Prevention and treatment

  • Proper sanitation and hygienic conditions are the best methods of prevention.
  • Safe and effective drugs against ancylostomiasis are tetrachloroethane and carbon tetrachloride.

Enterobiasis (Oxyuriasis)

  • Enterobiasis disease is caused by Enterobius vermicularis (pinworm).
  • It is found in human caecum, colon or vermiform appendix. It is more common in children.

Mode of transmission

  • Female pinworms migrate out through the colon and rectum, and deposit enormous number of eggs in the skin folds around the anus.
  • Deposition of eggs around the anus causes intense itching, and when scratched, the eggs are picked up by the fingers, under the nails or in nail bed, from where they find their way to the mouth, and are swallowed, along with the food. The eggs hatch in the stomach and migrate to the colon, to develop into adult worms.

Symptoms

  • The disease causes intense itching of the anus, inflammation of mucous membrane of colon and appendix, nausea, abdominal pain and diarrhoea.

Prevention and treatment

  • Proper sanitation and hygiene are important to prevent the disease.
  • Piperazine is the most effective drug used in the treatment of this disease.

Trichinosis

  • Trichinosis is caused by Trichinella spiralis.
  • Adult worm lives as an endoparasite in human small intestine and some other mammals like pig, dog, cat, rat; however, its larvae are present in the striated muscles of the host.

Mode of transmission

  • Man becomes infected following ingestion of encysted larvae with raw or under-cooked pork.
  • In the intestine, larvae hatch out of cysts and develop into sexually mature adult worms.
  • The female worm, after copulation lays eggs that hatch into young larvae, which enter the blood stream and are carried to the striated muscles of the chest and the legs, where they form cysts.

Symptoms

  • Symptoms are nausea, vomiting, oedema of face and eyelids, fever, muscular pains, pain during chewing, swallowing, breathing and in moving arms and legs.

Prevention and treatment

  • This disease can be prevented by eating properly cooked pork.
  • Mebendazole or albendazole, decreases the likelihood of larval encystation, particularly if given within three days of infection.

Dracunculiasis

  • Dracunculiasis is caused by Dracunculus medinensis (guinea worm) that occurs in the subcutaneous tissue of man.

Mode of transmission

  • Man acquires infection by taking in water infected with Cyclops.
  • From Cyclops, the larvae escape into the human intestine. Then, the larvae bore their way to the subcutaneous tissue where they become adults.

Symptoms

  • The guinea worm causes itching, diarrhoea, nausea, vomiting and eosinophilia due to its toxic secretions in the human body.

Prevention and treatment

  • Avoid drinking water contaminated with Cyclops is the preventable measure.
  • Metronidazole may be used for treatment.

Trichuriasis

  • Trichuriasis is caused by Trichiuris trichiura, (whip worm).
  • It is an endoparasite of caecum, colon and vermiform appendix.

Mode of transmission

  • Eggs of the worm gain entry into the human body through contaminated drinking water, raw fruits and vegetables. In the intestine, the eggs hatch and the larvae develop into adult whip worms.

Symptoms

  • Nausea, vomiting, constipation, headache, slight fever, pains resembling appendicitis, anaemia and eosinophilia are its symptoms.

Prevention and treatment

  • One should avoid drinking contaminated water.
  • One should eat raw fruits and vegetables after properly washing them.
  • Osarsol (acetarsone) and dithiazanine are the effective drugs for expulsion of whip worms.

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