Intestinal and Other Parasites

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Amaebiasis

Amaebiasis in man is caused by the parasite Entameba histolytica. It is not a worm but a small motile single-celled organism which digests red blood cells (see Fig. 1). When this infestation is confined to the bowel it is called Amoebic Dysentery. The parasite tends to form abscesses elsewhere, especially in the liver, and the disease is then named after the organ which is infected, e.g. HEPATIC AMOEBIASIS.

This infestation has appeared in most parts of the world with outbreaks in Great Britain and the U.S.A. not being uncommon. It is most prevalent, however, in China and India. Amaebiasis has a great tendency to spread through families because of poor sanitation and unclean habits of members of the family. The cysts (and entamoebae) appear in the stools of the infested person and are transmitted by flies, rats, or by direct contact with the food of the next victim.

The parasites form small cysts and ulcers in the caeum and wall of the large bowel and rectum. Some of the parasites may be carried to the liver where they produce abscesses and symptoms of hepatitis.

Symptoms

Amoebiasis is a chronic disease. The incubation period is from one week to three months. Diarrhoea is usually the most obvious symptom and is mostly of the intermittent variety. The stools are copious and there is blood intermingled with the faces The smell is very offensive. Fever is very uncommon unless the liver is involved, but there is marked loss of weight. Vomiting rarely occurs, but there is often tenderness of the abdomen over the course of the large bowel. The complications are those of perforation of the bowel wall, haemorrhage, and exhaustion.

Diagnosis is made by examining the stools for cysts and for the motile amoebar. The appearance of the bowel wall can be examined by means of a sigmoidoscope (a tube with a light and with a magnifying lens, used to inspect the bowel via the anus). The blood shows a mild leucocytosis.

Treatment

Metronidazole (Flagyl) has greatly simplified of recent years the treatment of amoebic dysentery; 800 milligrammes (4 Flagyl tablets) thrice daily for 5 days will give a satisfactory clearance in acute attacks.
To protect the liver from invasion, the acute attack can, alternatively, be treated for about fourteen days with a combination of tetracycline, diloxanide furoate (Furamide), and chloroquine.
In severe attacks, especially in children and debilitated patients, the patient should be confined to bed and kept under the doctor's close care. Several treatments are available.

Metronidazole 800 milligrammes should be given three times a day for five days com-bined with tetracycline and diloxanide furoate as in treatment 2.

Emetine hydrochloride 65 milligrammes daily by intramuscular injection for about five days until the dysentery clears, together with tetracycline and diloxanide furoate.

Dehydroemetine 1.5 milligrammes per kilogramme of body weight by intramuscular injection for five to ten days combined with tetracycline and diloxanide furoate.

For hepatic amoebiasis, 400 milligrammes of metronidazole three times a day for five days should clear the condition.

An alternative combined treatment with emetine hydrochloride for 10 days, chloro-quine for 28 days, and diloxanide furoate for 10 days is also very effective.

General Management

In the acute condition, the patient needs kindly and careful nursing for he is usually much under-nourished. If emetine has been given, its toxic side-effects on the heart muscle will be much reduced if the patient remains strictly resting in bed. Once the diarrhoea is con-trolled he can be given a good mixed diet rich in any of the meat, fish, and dairy proteins. Vitamin content of the foods should be high. Fluids should be taken freely. Patients in bed should be given a bath daily or take one when ambulant.

Prevention

This is relatively simple and merely entails the washing of one's hands after toilet usage and before meals. All vegetables should be cooked and drinking water boiled. Proper methods of sanitation should be installed. Wire mesh on windows and doors, fly sprays and rat killers will exclude the vectors. Finally, carriers of the disease (but who show no obvious signs of it) should be treated thoroughly and kept from occupations which take them where food is prepared.

Worm Infestations

Worm infestations are very common in tropical and subtropical countries and create much misery. They have been a cause of suffering from ancient times as evidenced by the discovery of calcified eggs of Schistosoma in Egyptian mummies. Medical papyri around 1000 B.C. record the symptoms of blood in the urine due to worms and they noted the existence of tapeworms.

Certain worms gain admittance to their victim directly while others require a vector, e.g. the filarial parasite is transmitted to man by the bite of a mosquito.

The life-span of the different kinds of worms which may infest man vary greatly. In patients who have been inadequately treated, tapeworms have been known to survive for twenty years. In threadworms, the life cycle is two weeks.

General Diagnosis

Some worms or their eggs are easily seen in the faeces as are those of Ascaris lumbricoides (roundworms) and Toenia saginata (beef tapeworm). Others require a more meticulous search, using a miscroscope to inspect samples of blood, faeces, urine, skin, or muscle.

Certain tests may be made of a person's blood or his skin to detect the presence of worms in the tissues. One example is the Casoni test in which a small amount of substance is injected into the patient's skin and his response to the injections will show whether or not he has a hydatid infestation.

Ancylostomiasis (Hookworm Infestation)

Hookworm is common in tropical and sub-tropical countries and occasionally there is an outbreak in a city of Great Britain. This is especially true today as there are many migrants from tropical countries who arrive here bringing the parasite with them unknowingly.

The eggs pass out in the faeces of an infested person and, after a period of development in the soil, the larvae penetrate the human skin, from whence they migrate via the veins to the alimentary canal, especially the small intestine, and there they adhere to the bowel wall and extract blood (see Fig. 5).

Symptoms

The predominant symptoms are lethargy and weakness due to a severe anaemia. This anaemia leads to slow or retarded development in children. Abdominal pain and attacks of fever are not uncommon.

Treatment

Tetrachloroethylene is the drug of choice. The adult dose is 4 millilitres and may be given with a saline purgative, such as sodium sulphate. The dose for a child is 0-2 millilitres for each year of life. Two or more courses of treatment are required. It is important to remember that tetrachloroethy-lene deteriorates in a hot climate and so it must be stored in a cool dark place.

Bephenium hydroxynaphthoate has also been used with success against the hookworm. The dose is 5 grammes of granules for all ages; purgation is not needed. No food should be eaten for two hours after a dose.

The anxmia is corrected by the administration of iron-containing preparations, e.g. ferrous sulphate or ferrous gluconate tablets, and by eating a well-balanced diet.

Prevention

This is best achieved by good sanitation. Public Health authorities need to direct the placement of latrines and toilets away from habitations, and ensure adequate drainage. When living in an infested area it is advisable to wear strong thick boots.

Ascariasis (Roundworm Infestation)

Ascaris lumbricoides is not uncommon in Great Britain and is found in most parts of the world. It is a pale yellow worm up to 25 to 35 cm. in length. Infestation occurs as a result of eating contaminated food, the contamination usually being due to handling foodstuffs with unwashed hands. The eggs are swallowed and they hatch out in the duodenum and the embryos find their way to the lungs.

Symptoms

Vague digestive symptoms of nausea and malaise with occasional abdominal pain is usual. Sometimes a child will develop a cough and bronchopneumonia with the production of blood-stained sputum. The adult worm lives in the small intestine and remains there often without producing any symptoms.

Treatment

Piperazine is most effective. Piperazine citrate (Antepar) elixir is given to adults in a dose of 30 millilitres which contains 3 grammes of piperazine citrate. For a child under 20 kilogrammes of body weight a suitable dose is 16 millilitres.

This is given as a single dose at night, purgation being unnecessary. Piperazine adipate tablets (0-3 gra nine) may be used and the dosage employed is 100 milligrammes per kilogramme of body weight to a maximum of 4 grammes for children, and 4 grammes for adults. This medication is taken as a single dose with food. It may then be followed next morning by a saline aperient.

Tetramisole and levarnisole in single doses have been used successfully in South Africa, Ceylon, and South America.

Prevention

In endemic areas one must not eat uncooked vegetables, and the hands must be thoroughly washed before eating.

Cestodiasis(Tapeworm Infestation)

The tapeworm is a ribbon-shaped worm and inhabits the human intestinal tract. It does not have an alimentary tract of its own but absorbs its host's food from its surface. One end is called the scolex by which it is attached to the bowel wall. The remainder is composed of short segments jointed together, the last segments being full of eggs. These segments are known as proglottids.

Tcenia solium (PORK TAPEWORM)

This worm varies in length up to 12 feet. Its scolex or head consists of suckers and two rows of hooklets anterior to the suckers. Persons become infested by eating undercooked pork in which there are living tapeworm larvar (see Fig. 3).

Taenia saginata (BEEF TAPEWORM)

This is larger and may be several feet in length. The scolex is the size of a pin head and has four suckers. Persons become infested by eating undercooked infected beef.

Symptoms

In the acute phase the symptoms are fever, diarrhoea and colic, but these may vary, and there may be loss of weight and increased appetite. In the chronic phase there may be anxmia and the appearance of gravid proglottids (egg segments) in the faeces and underclothing.

Treatment

The most effective drug treatment is either niclosamide 2 grammes (Yomesan) or dichlorophen (Anthiphen) 6 grammes given on each of two successive days. Tablets are crushed or chewed before swallowing. If no gravid segments are passed three months later, the patient is cured. During, or for a few days after treatment, the hands of all in contact with the patient must be kept scrupulously clean.

Mepacrine and male fern have also been widely used against both types of tapeworm but treatments with them are more complicated procedures. Male fern (filix mas) is effective especially against Taenia solium although the treatment requires a long period. It is given as follows.

Method

For 48 hours an adult patient is given fluids only. Saline aperients are administered night and morning. On the third treatment morning 2-5 millilitres of fresh extract of male fern in capsules or in suspension is given at 6 a.m. and repeated at 6.15 a.m., and at 6.30 a.m. For the next half-hour the patient takes only sips of water, 60 millilitres of saturated sodium sulphate solution being given at 7 a.m. Proportionately smaller doses are given to children. By 9 a.m. the scolex should have been passed but, if not, an enema should be administered. Food may be given when the scolex is found, or in any event by 9.30 a.m. The patient should remain in bed during the whole day of treatment.

Prevention

Thorough cooking of meat, especially pork, is essential. Where Toenia solium is endemic, pork should not be eaten unless it comes from certified clean slaughter houses. Raw vegetables in tropical countries should be avoided. Scrupulous cleanliness is most necessary when dealing with patients who are infested. Medical aid should be obtained immediately tapeworm is suspected.

Cysticercosis

This is a complication that occurs in untreated cases of tapeworm. The eggs penetrate the tissues, and cysts occur in the muscles, under the skin, and sometimes even in the brain. Surgical treatment may be necessary in these cases.

Hyatid Cysts

These are caused by the Echinococcus granulosus, the tapeworm that infests dogs, sheep, and cattle. It affects man mostly through the dog. This tapeworm forms cysts which grow to a large size particularly in the liver and lungs, although the kidneys, stomach, brain and bones may be affected too, causing pressure symptoms.

Diagnosis

A Casoni test, given by subcutaneous injection of hydatid fluid from a sheep, is reliable in 85 per cent of cases in diagnosing the disease. On no account should the needle be inserted into the cyst itself.

The cysts may be removed surgically, but if so they must be removed whole.

Dracontiasis (Guinea Worm Infestation)

This disease is due to infestation with the parasite Dracunculus medinensis and is found in parts of India and Africa. The embryo worm is about 0.5 mm. in length and the adult female 30 to 100 cm. in length and 1.5 mm. in diameter. The embryo spends part of its life cycle in a fresh-water flea of the cyclops family and, since the water fleas inhabit open wells, they are often swallowed in the drinking water.

Symptoms

The worm matures in man's gut and usually travels to the lower extremities. After a time a small ulceration appears and the patient complains of a burning sensation and the desire to immerse the foot in water. If a drop of water is placed on the ulcer a whitish secretion appears and this contains a great number of guinea worm embryos.

Skin rashes, vomiting, malaise, diarrhoea, asthma, giddiness, and fainting may occur. These are probably due to the poisons produced by the worm. If the worm becomes damaged while lying in the leg the surrounding tissues may become very inflamed and cause damage to the muscles, joints, and tendons.

Treatment

Niridazole, 25 milligrammes per kilogramme body weight given twice daily for seven to ten days, destroys the worms by making degenerative changes in them. The extruding worm can then be wound around a thin clean stick during a period of several days. Pain is relieved and the ulcers heal rapidly.

Prevention

Drinking water needs to be protected from pollution by infected people. The cyclops can be killed easily by heating the water a few degrees above the temperature in which they live. Certain species of fish which eat cyclops may be introduced into infested wells.

For immediate use, water can be cleared of cyclops by the simple expedient of straining it through calico.

Enterobiasis (Threadworm or Pinworm Infestation)

This is due to intestinal infestation with a small white worm, Oxyuris vermicularis, from 2 to 13 millimetres in length. The female lays her eggs around the anal opening and her movements cause the intense itching which often occurs at night. The infestation occurs by eating raw vegetables, or other foodstuffs handled by infected persons whose unwashed hands or finger nails retain the eggs; or they may be passed by hand from child to child if hands are not well washed after using the toilet (see Fig. 4).

Symptoms

The symptoms in the child are digestive disturbances, irritability, mucus or slime in the stools, sleeplessness, and often grinding of the teeth.

Diagnosis is made by rubbing a small piece of cellophane, on a glass rod, over the anal orifice and then examining it under a micro-scope for the eggs. One may see the thread-worms themselves as fine pieces of cotton thread if one looks at the child's anus in the evening.

Treatment

A viprynium (Vanquin) tablet (50 milligrammes) for an adult and viprynium suspension for a child (a 5-ml spoonful) to be followed seven days later by another dose of a tablet or suspension will get rid of the worms. Viprynium colours the stools red and, if spilt, stains linen red.

Prevention

Hands should be washed frequently and well, especially before eating. Bedroom dust which may contain eggs should be kept to a minimum by frequent use of a vacuum cleaner on the bed, bedding, and floors. If there is more than one child in the house-hold it is advisable to treat the whole family to prevent cross-infection.

Filariasis

This disease is predominantly found in Africa and three of the filarial species of worms are of interest to man.

Onchocerca Volvulus. This is transmitted by a species of Simulium (biting gnat) and causes intense itching and thickening of the skin. Small lumps appear all over the body and may sometimes cause blindness. Lumps containing adult worms require surgical removal.

Wuchereria Bancrofti

This filaria causes a disease known as elephantiasis. Certain mosquitos are responsible for its spread. Gross swellings of the legs and external genitalia occur due to blockage of the lymphatics by the filarim. Bacterial infection often follows and antibiotics may be required to treat this. Treatment of the swellings may be surgical.

Loa loa

This is transmitted by the mangrove fly. The disease presents itself as transient localised swellings under the skin, known as calabar swellings. Sometimes the worm is seen to pass across the eye under the con-junctiva. A painful dermatitis with itching is associated with loaiasis.

Treatment

Mass treatment with diethyl-carbamazine over a period of three weeks is very effective medically. The dosage is 2 to 12 milligrammes per kilogramme body weight per day in three divided doses after meals. A small dose of 1 milligramme per kilo-gramme is given for three days then increased every 2 days until the 12-milligramme dosage is reached.

Unpleasant side-effects occur with treatment, such as fever, generalised itching, head-ache, painful joints, malaise, and nausea.

These are due to the allergic reactions of the patient to the destroyed filaria; in his tissues and are treated with antihistamine drugs such as promethazine hydrochloride. If the eyes are involved, then local hydrocortisone may be used with advantage.

Prevention

In endemic areas precaution is the only method of prevention. Mosquito nets must be used and gauze fixed to doors and windows. Spraying or dusting frequently with dicophane (DDT) is very effective in destroying insect vectors.

Schistosomiasis (Bilharzia)

Schistosomiasis is the cause of a great deal of suffering, especially in Africa and Egypt. Today it vies with malaria as a major scourge of mankind. Bilharz found in 1851 the organism responsible for the disease. Later it was found that this schistosome (Fig. 5) inhabited a fresh-water snail during part of its life cycle. The building of new waterways and dams has encouraged the spread of the snails (and the schistosomes) despite the finding of a chemical to destroy them.

So heavily infested can an irrigation area become, that even dewdrops in rice fields have been found full of the larval forms.

Symptoms

Some weeks after the larvae of the schistosome have pierced their way through the skin, symptoms of fever, abdominal pain, cough, skin rash and diarrhoea develop, accompanied by swelling of the spleen and liver. After months or years, cystitis occurs with passage of blood in the urine. Anaemia is very common.

Treatment

The well-tried elaborate treatment using sodium antimony tartrate is still employed and is effective despite its uncomfortable side-effects but it has largely given place to that using tablets of niridazole (Ambilhar); dosage is 25 milligrammes per kilogramme body weight daily for seven days)

Two new drugs are now being used-hycanthone in South America and metriphonate in East Africa. The cystitis leads to stones in the bladder, cancer, ulceration, and fistulm which will require surgical treatment.

Prevention

Bathing and washing in irrigation ditches or pools, in areas where the disease is prevalent, should be avoided. Ordinary clothes do not give protection. Rubber thigh boots and gloves are essential to persons who work in infested waters.

Drinking water should be filtered, sterilised by boiling, or stored out of contact with snails for two to three days. Chlorine concentrations used to kill ordinary bacteria do not kill the larvae. Public Health measures may be taken by spraying the land every year with Bayer 73 (Bayluscide) to kill the snails. Halazone, 1 part per million in water, will kill the cercariae.

Strongyloidiasis

Infestation by Strongyloides stercoralis occurs in tropical countries. It causes severe bouts of diarrhoea and often skin manifestations of a long-standing nature.

Treatment is dithiazanine 200 milligrammes three times a day far 14 days; or thiabendazole.

Prevention. As for Ancylostomiasis.

Trichiniasis

This disease is due to an infestation with Trichinella spiralis which comes from rats via the pig. After infested pork has been eaten, the embryos migrate to the muscles (see Fig. 6) of the body causing inflammation and rheumatic-like pains.

In severe cases, symptoms of gastric disturbances occur and may resemble ptomaine poisoning. Mild cases recover in about two weeks but severe cases are much more prolonged.

Treatment

Tetrachloroethylene followed by vigorous purgation. When the larvae disseminate, dangerous systemic disturbances occur. Corticosteroids are used to control these effects. Thiabendazole affords relief from symptoms caused by cysts in muscle.

Prevention

The first step is to prevent infested rats from passing on the parasite to pigs. This is done by eradicating the rats with poison, and by fencing the pigs carefully. All rubbish needs to be burned and garbage stored in rat-proof containers to prevent the rats breeding.

Secondly, a high standard of inspection must be maintained at the slaughter houses to prevent bad pork being sold to the consumer; and finally great care must be taken to cook pork thoroughly and so kill any possible worms. This applies particularly to pork sausages which are often undercooked.

Submitted By
Dr. R. A. Hoekelman Md

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