Worm infestation

WORM INVESTITION

3 groups 1. Cestoda 2. Nematoda 3. Trematoda

Tapeworm Infestation  (Cestoda)

1. Tapeworms are long, ribbon shaped and segmented worms . 2. These worms lack an intestinal tract but able to absorb nutrients through their integument. 3. The adult consists of a head (scolex) with suckers to attach the mucosa of the intestine; a neck; and a segmented body that contains both male and female gonads (proglottids).

DISEASE ACQUIRATION

Humans acquire tapeworm by eating undercooked beef infected with Cysticercus bovis, the larval stage of Taenia saginata (beef tapeworm), undercooked pork containing the larval stage of T. solium (pork tapeworm), or undercooked freshwater fish containing larvae of Diphyllobothrium latum (fish tapeworm). Usually only one adult tapeworm is present in the gut but up to ten have been reported.

CESTODA (TAPEWORMS) TYPES

The most important cestoda that infest humans are: 1. Taenia saginata 2. Taenia solium 3. Echinococcus 4. Diphyllobothrium (fish tapeworm) 5. Hymenolepis


1. Primary host: Humans are the primary host in all (adult live in intestine) except Echinococcus, in which the human is intermediate host (larva within tissues) and dogs are primary host (final host). 2. Intermediate Hosts: Cattle: T. Saginata, Pigs: T. Solium, Fishs: Diphyllobothrium, Human, sheep and others: Echinococcus. 3. Rarely the human becomes intermediate host for T. solium if he/she ingest eggs accidently.

LIFE CYCLE

The primary host (human or others) passes the mature segments containing ova which remain viable for Ws in the soil and may be consumed by intermediate hosts (cattle, sheep, pig, fishes) and change to larva in their tissues. When humans are the primary host, the adult cestode is limited to the intestinal tract. When humans are the intermediate hosts, the larvae are within the tissues, migrating through the different organ systems.

T. SaginataThe adult worm may be several meters long

T. Solium scolex with hooks and suckers

LIFE CYCLE OF T- SAGINATA

T. OvaThe ova of T. saginata and T. solium are indistinguishable microscopically.

Pigs intermediate host for T.solium

Cattles intermediate host for T. saginata

T. saginata


Most worms are solitary (AL- DODDA AL-WAHEDA), and worms may live 30 years and may reach 20 meters in length

C/ P. OF T. SAGINATA

1. produces little or no intestinal upset in human beings, but knowledge of its presence, by noting segments in the faeces or on underclothing, may distress the patient. . 2. some complain of nausea and upper abdominal pains, often relieved by food. A few patients eat to relieve symptoms.



4. In children, impaired appetite can cause nutritional consequences. 5. Some patients have symptoms suggestive of hypoglycaemia, namely dizziness and sweating. Pruritus ani is common. . 6. Eosinophilia up to 10 per cent can occur with any gut cestode.

DIAGNOSIS

Consider a stool examination for ova and parasites. that release eggs or worm segments directly into the stool (T saginata, Diphyllobothrium). Collecting 2-3 stool samples is necessary for detection of the parasite because eggs and parasite particles are released irregularly into the stool and may be periodically absent from stool during infection.

TREATMENT OF T. SAGINATA

1. Mebendazole (Vermox): 100mg PO, bid for 3days, second course if no response after 3-4 Ws. Also Albendazole can be given. 2. Niclosamide (Yomesan): 2g, is given to adults and older children as a single morning dose on an empty stomach; the tablets should be chewed. Children of 2 to 6 years should receive 1g, and those below 250mg. 3. The alternative is praziquantel, 5 to 10mg/kg as a single dose after a light breakfast. After either drug the proximal part of the worm disintegrates in the gut and the scolex cannot be found. Failure of proglottids to reappear within 3 to 4months indicates cure.

CONTROL

This can be very successful. Health education concerning raw beef, meat inspection, sanitation and hygiene on cattle farms, and proper sewage treatment and disposal. Mass treatment of herd contacts, or whole adult populations, are the most effective short-term measures when endemicity is high. T. saginata causes great economic loss to the beef industry in some developing countries.

C/ P. OF T. SOLIUM

1.T solium infections (adult worm) are usually asymptomatic; however, infected patients may have generalized complaints include epigastric or periumbilical discomfort; nausea; hunger, weight loss, anorexia, or increased appetite. So symptoms due to the adult worms are similar to those of T. saginata but are often milder and not associated with pruritus ani.


2. Cysticercosis is a clinical syndrome of expanding embryonal cysts that occurs with T solium. The cysticerci that develop with T solium infestations can be found anywhere in the body, but they mainly occur in the central nervous system (neurocysticercosis) causing seizures, brain cysts and calcification and skeletal muscles, causing local inflammatory responses and mass effects from the cystic growth.


Cysticercosis is a major health problem in Mexico, some South American countries, and to a lesser extent in Africa and Asia. In 1969, T. solium was introduced from Bali into the highlands of Indonesian and New Guinea, where the disease is now one of great importance.

Echinococcus infestations

The disease is common in the Middle East, North and East Africa, Australia and Argentina.


By handling a dog or drinking contaminated water, humans may ingest eggs . The embryo is liberated from the ovum in the small intestine and gains access to the blood stream and thus to the liver.



CLINICAL PICTURE

CLINICAL MANIFESTATION

A hydatid cyst is typically acquired in childhood and it may, after growing for some years, cause pressure symptoms. These vary, depending on the organ or tissue involved. In nearly 75% of patients with hydatid disease the right lobe of the liver is invaded and contains a single cyst. In others a cyst may be found in lung, bone, brain or elsewhere.


1. The patient remains asymptomatic until the cysts cause a mass effect on the organ, which can be 5-20 years after the initial infestation. 2. These cysts do not metastasize, but they may be disseminated by accidental spillage. 3.Most patients have single organ involvement and most will have a solitary cyst .


Hepatic form: 1. palpable R hypochondrial mass and jaundice can occur. 2. Rupture of liver hydatid cyst into peritoneal cavity may cause anaphylactic shock.

Pulmonary: 25% cystic rupture may result in symptoms of cough, chest pain, and hemoptysis. Crape-like material may be coughed. Rarely pneumothorax, with or without pleural effusion and anaphylaxis can occur following cyst rupture. Other organs: Brain, Kidney, Bone, Adrenal glands.

DIAGNOSIS

The diagnosis depends on the clinical, radiological and ultrasound findings in a patient who has lived in close contact with dogs in an endemic area. Complement fixation and ELISA are positive in 70-90% of patients.

HYDATID CYSTS OF LIVER AND LUNG

MANAGEMENT


Hydatid cysts should be excised wherever possible. Great care is taken to avoid spillage and cavities are sterilised with 0.5% silver nitrate or 2.7% sodium chloride. Albendazole (400 mg 12-hourly for 3 months) is used for inoperable disease, and to reduce the infectivity of cysts pre-operatively. Praziquantel 20 mg/kg 12-hourly for 14 days kills protoscolices perioperatively.

Prevention

Prevention is difficult in situations where there is a close association with dogs and sheep. Personal hygiene, satisfactory disposal of carcasses, meat inspection and deworming of dogs can greatly reduce the prevalence of disease.

Diphyllobothriasis

Is an infection that occurs from eating raw or undercooked fish infected with Diphyllobothrium species. Diphyllobothrium organisms are present in lakes, rivers, and deltas of freshwaters. Eskimos in western Alaska and the West Coast of the United States are frequent hosts. Also in finland



The cestode is not invasive, but it does absorb a large amount of vitamin B-12 and interferes with vitamin B-12 absorption from the ileum, producing a megaloblastic anemia that resembles pernicious anemia (clinically and hematologically). Patients may complain of neurologic symptoms resembling pernicious anemia (eg, paresthesias, difficulty with balance, dementia or confusional states).

Nematoda

Ascariasis


Ascariasis is an infection caused by Ascaris lumbricoides. Normally, the adult worms are located in the small intestine. In unusual circumstances, such as fever, irritation due to drugs, anaesthesia, and bowel manipulation during surgery, the worms may migrate to ectopic sites where they may give rise to severe disease.

GEOGRAPHICAL DISTRIBUTION

The distribution is cosmopolitan but the parasite occurs more frequently in moist and warm climates. In some rural tropical areas, the entire population may be infected. It is relatively more common in children, who also carry higher worm loads.

MORPHOLOGY

A mature worm is cylindrical with tapering ends. It is creamy white to light brown in colour. The female measures 20 to 35cm in length and 3 to 6mm in breadth. The male measures 12 to 31cm in length and 2 to 4mm in breadth and has a curved tail. The head has three lips at the anterior end.


The worm is able to maintain its position in the small intestine by the activity of somatic muscles. If the somatic muscles are paralysed by anthelminthics, it is expelled by peristalsis.

LIFECYCLE

The gravid female produces 200000 to 250000 eggs daily. These take 3 or 4 weeks to develop into the infective stage. The eggs are resistant to chemicals and low temperature and may remain viable for years in moist soil.


On ingestion, the infective larva hatches out in the small intestine and penetrates the intestinal wall to enter the portal circulation. From the liver it is carried to the heart and via the pulmonary artery to the lungs. In the lungs.


From the lungs the larva moves up to the bronchi and then through the epiglottis to enter the digestive tract. In the intestine, it becomes a sexually mature worm. The lifespan of an adult worm is approximately 1 year, after which it is spontaneously expelled. In hyperendemic areas, children are being continuously infected so that as some worms are being expelled, others are maturing to take their place.

CLINICAL ASPECTS

1. In the majority of cases, the infected individual remains asymptomatic. 2. May cause nutritional problems and hinders the normal development of children. 3. Occasionally, patients may develop fever, malaise, urticaria, intestinal colic, nausea, vomiting, diarrhoea, and central nervous disorders.


3. The migration of larval Ascaris through the lungs may produce pneumonitis and bronchospasm known as Loeffler's syndrome. Chest radiographs may show diffuse mottling and increased prominence of peribronchial markings. 4. There is generally high eosinophilia and the condition subsides after 7 to 10days unless reinfection occurs.


5.When large numbers of worms form a bolus and block the intestinal lumen producing signs and symptoms of acute intestinal obstruction (Rare).


6. When ectopic migration results in the entry of the worm into the appendix, common bile duct, or pancreatic duct (Also rare). When the biliary tract is invaded, there is severe colic, often followed by suppurative cholangitis and multiple liver abscesses resulting from the disintegration of the trapped worm and secondary bacterial infection.. When the worm impacts in the ampulla of Vater causing acute pancreatitis and pancreatic necrosis.

DIAGNOSIS

This is usually made by detecting Ascaris eggs in the faeces. Sometimes, the adult worms pass in the faeces or the nose or vomiting the worm in a sick child. Occasionally, adult worms are outlined in the intestines during barium-meal examination

TREATMENT

All positive cases, irrespective of the worm load, should be treated as even a few worms can undergo ectopic migration with dangerous consequences.



Pyrantel pamoate A single dose of 10mg/kg body weight is effective. It also effective against Enterobius vermicularis and hookworms.


Mebendazole It is given as 100mg twice daily for 3days, irrespective of age. The manufacturers now advise against this drug in children under 2 years of age as there is a report of severe neurological toxicity in a young child.


Levamisole hydrochloride This is probably the most effective antiascaris agent and produces rapid paralysis of the worm. It is administered as a single dose of 150mg for adults and 50mg for persons under 10kg. Side-effects are more common than with pyrantel and mebendazole. This drug has occasionally resulted in blood dyscrasias when used in prolonged treatment of autoimmune diseases and rheumatoid arthritis.


Piperazine salts These are widely used because of their low cost and high degree of efficacy which includes E. vermicularis, but not hookworm. The dose is 75mg/kg (maximum of 3.5 g) given as a single dose daily for two consecutive days. Prior fasting is not required. Occasionally, symptoms involving the central nervous system such as unsteadiness and vertigo have been reported.

PREVENTION AND CONTROL

As Ascaris eggs can survive in the soil for many years, prevention and control in the endemic areas is difficult. Mass chemotherapy given at intervals of 6months along with environmental sanitation can break the cycle. Prevalence rates of ascariasis and other soil-transmitted helminths are greatly reduced by improvement in housing. At a personal level, infection is prevented by eating only cooked food and by avoiding green vegetables and salads in countries where human faeces are used as a fertilizer and where this parasite is endemic.

Enterobiasis

Enterobiasis is a disease caused by Enterobius vermicularis infestation. Children are more often involved than adults. It occurs in groups such as families living together, and in army camps.

MORPHOLOGY

Enterobius vermicularis

Enterobius vermicularis OVUM

LIFECYCLE

The adults are mainly located in the caecal region and the female deposits its eggs on the anus and perianal skin. Direct person-to-person infection occurs by (inhalation and swallowing) of the eggs. In addition, autoinfection occurs by contamination of fingers. It may occur as a sexually transmitted disease among male homosexuals. There is no visceral migration and the larva matures into an adult in the lumen of the intestinal tract. The lifecycle of the parasite is completed in about 6 weeks. Unlike Ascaris and Trichuris eggs, which need many days of development in soil before becoming embryonated, Enterobius eggs are embryonated when passed, hence there is rapid transmission from person to person.

CLINICAL ASPECTS

The most common presenting symptom is pruritus ani. This can be very troublesome and occurs more often during the night. Persistent itching may lead to inflammation and secondary bacterial infection of the perianal region. Infected children may suffer from insomnia, emotional disturbance, anorexia, weight loss, and enuresis. Occasionally, adult worms may migrate, entering the female genital tract. Inside the uterus or the Fallopian tube they may get encapsulated and produce symptoms of salpingitis. In adolescents and children it is an important cause of vulvovaginitis. The parasite may also get lodged in the lumen of the appendix, leading to appendicitis. The lifespan of the parasite is 3 to 6 weeks.

DIAGNOSIS

The eggs are not usually found in the faeces. They are most easily found around the anus, by swabbing or using cellulose adhesive tape. The anal examination for eggs should be done before defecation or bathing. Sometimes intact worms are passed in the faeces and can be easily recognized by their size and shape.

TREATMENT

Attention to personal hygiene is an important part of treatment and prevention. The patient should be instructed to keep nails short and wash hands with soap and water after defaecating. The bed cover and sleeping garments should be changed every day and the floor in the bedroom kept clean. With these simple hygienic measures, infection will disappear on its own, due to the short lifespan of the parasite.


Many drugs are available to treat the infection and it is advisable to treat all the children and adults in the same household at the same time. Piperazine citrate is given in a dose of 65mg/kg for 7days. The course is repeated after 2 weeks. Piperazine is contraindicated in renal and liver disease and epilepsy. Pyrantel pamoate is equally effective in a single dose of 10mg/kg (maximum 1g) and its side-effect profile is better than piperazine. The drug is repeated after 2 weeks. Mebendazole is effective in a single dose of 100mg, repeated after 2 weeks. This drug is contraindicated in pregnancy. Pyrvinium pamoate is specific for E. vermicularis and is given in a single dose of 5mg/kg (maximum 350mg), repeated after 2 weeks. The main disadvantage of this drug is that it can stain garments and skin with a bright red colour.

The hookworms

Most infections by adult worms are due to 1. Ancylostoma duodenale 2. Necator americanus.



MORPHOLOGY AND LIFE CYCLE


Adult worms are greyish-white and measure 8 to 13mm in length; they taper at both ends. Anteriorly the worms are flexed dorsally, giving them their hooked appearance. They attach themselves to the wall of the jejunum by drawing mucosa into the buccal cavity. By means of lytic enzymes, anticoagulants, and pharyngeal pump, blood and tissue fluids are ingested. Worms move to new locations quite frequently, partly in response to host immunological responses. Females produce 5000 to 20000 eggs per day,


but output per worm declines as worm load rises. In the soil, development is temperature dependent. Under optimum conditions eggs hatch within 2 days and larvae develop to the infective stage in 5 days; they can persist in sandy soil for up to a month. Larvae penetrate host skin after soil contact, most commonly between the toes. After entry into dermal venules and lymphatics they are carried to the lung, where they penetrate the alveoli, ascend the bronchi and trachea, and after being swallowed, re-enter the gut where the final moult occurs. Eggs can appear in the faeces 50 to 60 days after cutaneous exposure.

HOOKWORM

HOOKWORM LIFECYCLE

HOOKWORM LIFECYCLE

HOOKWORMS (ADULT)



HOOKWORM MOUTH

HOOKWORM (ADULT)

HOOKWORM OVA

CLINICAL FEATURES ATTRIBUTABLE TO ADULT WORMS

In acute primary infections and in children, epigastric pain is common and may be associated with poor appetite and sometimes diarrhoea. Anorexia is an important mechanism leading to nutritional deficit in children.


Most patients present with slowly progressive iron-deficiency anaemia; such patients typically have no gut symptoms. Exertional dyspnoea may begin at haemoglobin levels of 8 g/dl, but may not be noted until it falls to 5 g/dl. Palpitations, weakness, and faintness on exertion are common; sometimes there is precordial pain or leg claudication. Tinnitus is common, and some patients are aware of their jugular vascular bruit.

MICROCYTIC HYPOCHROMIC

A puffy oedema of the face, arms, and hands is typical, and often unaccompanied by dependent oedema. In severe cases, mental apathy and depression are common, and in adults, amenorrhoea or impotence. Pica is common, especially in pregnancy, and geophagy can lead to acquisition of other soil-transmitted nematodes. Milder degrees of anaemia cause reduced physical-work performance in adults. In children, growth and development may be slowed and cognitive impairment can lead to reduced scholastic achievement. Assessment of cardiovascular status is essential in anaemic patients, to differentiate a well-compensated, high-output state from a dangerous low-output one.

FEATURES DUE TO LARVA

Cutaneous lesions take the form of migrating, itchy, red, papules, known as creeping eruption or cutaneous larva migrans. They commonly become vesiculated and excoriated, and this leads to bacterial pyoderma. In many endemic populations, lesions attributable to A. duodenale or N. americanus are either unnoticed or transient. Among estate workers the condition is known as ground itch prominent lesions occur in laboratory infections. Wheezy cough due to pneumonitis is more common with A. duodenale; symptoms can continue for many months after one exposure, owing to remobilization of larvae arrested in muscle. Lung symptoms are most prominent in heavy primary infections.

DIAGNOSIS

Stool microscopy will reveal eggs. It is useful to estimate the faecal egg count as this provides some measure of the intensity of infection. Haematological findings are microcytic hypochromic anaemia, eosinophilia, low serum ferritin and iron, raised serum transferrin, and reduced bone-marrow haemosiderin.

TREATMENT

Safe and effective anthelminthics are now available. A single 400-mg dose of albendazole, or mebendazole, 100mg twice daily for 3days, are both very effective. Alternatives are pyrantel, 10mg/kg daily for three or four doses, or bephenium, 5 g daily for three doses, the latter being less effective for N. americanus.


To replace iron reserves, oral ferrous sulphate will suffice in most patients, but several weeks of medication may be necessary. When compliance is doubted, consideration should be given to intramuscular iron dextran or iron sorbitol. When adequate precautions can be taken it is sometimes appropriate to use total-dose intravenous infusion of iron dextran.


Blood transfusion may be necessary in pregnancy, and when cardiac output is compromised. Packed, or sedimented, red cells should be used and normally only one or two units will be required. Frusemide may be necessary to cover the transfusion, but in other circumstances diuretics should be used with caution. Depletion of plasma volume in hookworm anaemia patients with hypoproteinaemia can compromise cardiac output. Even bedrest in formerly ambulant patients can lead to significant diuresis. Oral fluids must not be restricted. Chemotherapy should generally be avoided in pregnancy; such patients should be managed with iron replacement or iron supplements only.



CONTROL Population-based measures are necessary when endemicity and morbidity are high. Latrines are generally beneficial, but can create foci for transmission. Peridomestic drainage lowers the water table, and reduces risk of transmission around latrines. Provision of piped water limits the need to walk to surface-water sources and so reduces contact with soil polluted by promiscuous defaecation. Washing and cooking vegetables will reduce oral A. duodenale transmission. Where human excreta is used as fertilizer, composting and chemical ovicides are needed.


Cash-crop estates, plantations, and irrigation schemes provide opportunities for managed control. Safe latrines should be provided, together with subsidized footwear. Anthelminthic drugs can be deployed in several ways. Even when laboratory stool tests are not done, certain target groups can be treated empirically because of their likelihood of infection. Examples are: agricultural and sewage workers; clinic outpatients with pallor; anaemic blood donors; and children with protein-calorie malnutrition.


Drug (chemotherapy) prophylaxis: with Single-dose medication is best and possible with albendazole, 400mg, or mebendazole, 600mg can be used in special circumstances. The ascaricides levamisole and piperazine have little action against hookworm.


Chemotherapy should be repeated two or four times yearly timing at the end of the dry season is most efficient. Both metrifonate, used for Schistosoma haematobium control, and ivermectin, used for onchocerciasis control, will have significant activity against hookworm. In all interventions, community participation is essential and health education is necessary to reinforce the measures used.