7 diseases that are Spread By Animal Parasites

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Some diseases are caused by worms that live in the host as parasites. Some of these diseases are discussed here.

1. Trichinosis

The normal host of the trichinella is the pig. It can pass its entire life cycle in man, rat and pig Trichinella Spiralis is seen in men where.

2. Pork is eaten

The female worm penetrates the intestinal wall to lay about 500 larvae at a time. The larvae reach the muscles through the lymphatic system. They form cysts and find entry into a new host when im­properly cooked pork is eaten .The larvae may remain encysted for about eight months, after which they calcify and die. The male worm is 15mm long and 0.04 mm broad. The female worm is 3-4 mm long and 0.05 mm broad.

The disease caused by the worm is serious in man. It is characterised by fever preceded by diarrhoea. There may be severe pain in muscles accompanied by oedema. Intestinal inflammation is com­mon and in acute cases the intestinal haemorrhages may be fatal. The eosinophilic count of the blood increases in individuals suffering from trichinosis. The incubation period is 9 days. However, it may sometimes be as short as 2 days and as long as 28 days.

Preventive measures to be taken include proper cooking of pork preferably at high temperatures. There should be proper disposal of uncooked garbage and pigs should not be fed on infected waste meat.

3. Ascariasis (Round Worm Infection)

This disease is caused by Ascaris lumbricoides commonly known as round worm. The round worms get nourishment from the blood and lymph of the host. The female worm is 20-40 cms long while the male is only 15-25 cms long. The round worms have a well developed alimentary canal and are white or reddish in colour. The female lays a large number of eggs. It can lay upto 200,000 eggs each day. The eggs are not capable of producing infection and can live as long as one year. The larvae develop in about three weeks and find entry into the human system through improperly washed food and dirty hands.

The larvae are set free in the intestines. They pass through the intestinal walls into the blood vessels on the right side of the heart. From the heart the larvae go to the lungs, then to the trachea and down into the oesophagus and intestines. While passing through the lungs they often damage the tissue and cause pneumonia. The larvae become adult in the intestines two months after being swallowed.

A large number of worms can get tangled and cause intestinal obstruction, which may need surgical operation. Sometimes they may leave the intestines and go to the stomach and get vomited through the mouth and nose. Unlike other worms, some of the round worms move freely in the intestines. The life span of an adult worm is about a year only. The worms secrete toxic substances causing nervous symptoms.

The general symptoms of round worm infection are loss of appetite, paleness, and abdominal pain. It may sometimes cause vomiting as well as asthmatic attacks.

Preventive measures include a high standard of hygiene for all. Night soil should be carefully disposed of. Salads and fruits eaten raw should be washed preferably with potassium permanganate solution. The worm eggs can withstand cold but get killed at 50°C temperature. Proper cooking will thus destroy all eggs. Sick persons should be properly treated so that they do not become a source of infection to healthy persons.

4. Tape Worm Infection

There are various types of tape worms, but the common one is known as Taenia solium. The worm passes through two distinct phases-in pig and in man, both of which are termed hosts. Taenia solium has three parts: the head, neck and body. The worm has a distinct head or scolex of the size of a pin head. The scolex has four suckers and attaches itself to the host by the means of hooks on the rostellum. The body of the tape worm is known as strobila and has a number of segments known as proglottides. The segments away from the head in size. It is a flat ribbon-like worm of 1/2 cm to 4 meters in length.

The ripe segments can feed themselves and in due course separate from the main body. These appear as whitish bits in the stools. The segments contain fertilized eggs or ova.

The pig becomes the intermediary host, when it feeds on faecal matter. The eggs develop into embryos m the pig’s intestine. These embryos pass through the intestinal wall and lodge themselves in muscles. These can be seen as pearl like bladder worms in about ten weeks. When infected and undercooked pork is eaten the covering of the bladder worms is dissolved by digestive juices and the worms are set free. These attach themselves to the intestinal wall of the new host and become mature in 2-3 months. The entire cycle is repeated again and again.

Symptoms usually include loss of appetite, abdominal pain and failure to grow. Stool examination shows the presence of tape worm bits.

Preventive measures consist of thorough inspection and cooking of pork. Sanitary disposal of waste and personal sanitation are very important.

5. Hook-Worm (Ancylostomum duodenale) Infection

Hook-worm infections are common in India, Europe and Egypt. The male worm is about 8-11 mm. long and the female is 10-13 mm. long. The worm is thread-like, with a conical-shaped head. The eggs are passed out in the faeces and the larvae emerge in about 24 hours under suitable conditions of warmth and humidity. These feed on faecal matter and mature in 4-5 days. This is an infectious stage. The larvae attach themselves to the host by piercing through the epi­dermis. From here they reach the blood-stream through the lymphatic system. From the heart they go to the bronchial tubes, up the trachea and get swallowed. The larvae attach themselve to the intestinal wall by means of hooks and cause haemorrhages. They develop into adults in about four weeks time. They suck the blood of the host and repeat the cycle.

Oral infection is possible but is not the usual mode of infection. The disease is also known as ancylostmiasis.

Abdominal pain with alternating diarrhoea and constipation is a common feature. Sometimes it is accompanied by the facial puffiness and oedema in the legs. The tongue looks like a sheet of white blotting paper. The patient becomes anaemic and experiences general weakness.

The best method of prevention is to educate the public and promote sanitary habits. Sanitary latrines should be installed in villages. People should not walk about barefoot. Personal protection is very essential. Carriers should be isolated and treated property. Drinking water should be properly protected from contamination.

6. Thread- Worm

Thread-worm infestation is common among children. The female worm is about 8-13 mm. long while the male is usually half its size. The male worm dies after fertilizing the female. The female worms wander and emerge out at the anal end and deposit the eggs in the perineal skin and the surrounding folds. The eggs are colorless and transparent. They turn into tadpole larvae in 12-36 hours and become infective. In acute infections the worms can be seen as small bits of thread at the anal end and m the faeces. They cause excessive irritation and local rash. The worms may enter the vagina of the female patient and cause vulvo-vagtmtis.

The eggs develop into adults in three weeks time. They are picked up by the nails when the victim scratches and cause auto-infection. The eggs may also be sticking to the personal clothing and bed linen. Improper personal hygiene and disposal of wastes increases the incidence of infection considerably.

Thread-worm infection may cause cough, sleeplessness, disordered appetite, restlessness and in acute cases convulsions may also occur. Enuresis (uncontrolled passing of urine) is also quite common.

Personal cleanliness is very important to rule out the chance of auto-infection. Bed linen and patient’s clothing should be properly wasted and sunned. The anus can be smeared with dilute ammoniated mercury ointment before sleeping. Antihelminthics like piperazine can be given orally to get rid of the worm.

7. Flukes

Flukes are flat worms and the life cycle is completed in two hosts. The eggs are passed out in faeces and find their way into water. These are eaten by snails and form embryos within their bodies. The snails are eaten by fish and the embryos penetrate into the fish muscles. When undercooked fish is eaten the embryos find their way back into the man. Adult flukes are hermaphrodite (both male and female). Treatment for flukes is not very satisfactory, so prevention is prefer­able. The adult worms live in the portal blood vessels and the mesenteric veins. The three diseases caused are urinary schis­tosomiasis, rectal schistosomiasis and dropsical schistosomiasis.

Some of the preventive measures to be taken are sanitary disposal of faeces and urine, avoidance of bathing in dirty waters and filtera­tion of the drinking water. Measures should be taken to free the water supply from snails so that the intermediate hosts are eliminated.


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