Pharmacotherapy/Treatment Of Worm (Helminth) Infection

Worms (helminth) are multicellular organisms that can infect the body. It can affect any part of the body including the intestines. There are different types of worms.

Symptoms Of Worm Infection

Symptoms vary depending on the worm involved. General symptoms include;

1. Abdominal pain

2. Gas/bloating

3. Fatigue

4. Dysentery

5. Poor appetite that can cause weight loss

6. Itchy around the anus at night and in some cases involve the vagina

7. Diarrhea, nausea and vomiting

8. Poor sleep pattern

9. Lack of concentration

10. Passing out worm in stool

Complications

1. Anemia

2. Intestinal blockage

Mode Of Transmission

Generally speaking, the worm or its egg passes through the stool. Poor hygiene leads to contamination of the environment including fingernails of infected people. Eating or drinking anything contaminated will lead to infection. Also, worms that can be contracted through the skin can be gotten from walking barefooted.

Read Also: Deworming drugs are not best taken at night

Diagnosis

1. Stool sample for analysis

2. Scratch tape test is the passing of a tap with adhesive to the anus several times to retrieve pinworm. It is done in the morning before bath to be able to get enough samples. The tap is placed under the microscope for evidence of eggs or worms.

3. Antibody test

4. Computer tomography (CT) scan of the abdomen

5. Abdominal x-ray

6. Magnetic resonance imaging (MRI) of the abdomen

7. Polymerase chain reaction (PCR) amplification is best for some like strongyloides stercoralis

Cause

There are three main categories of helminths: trematodes (flukes), cestodes (tapeworms) and nematodes (roundworms). Nematodes include threadworms (pinworms), ascariasis (roundworms), whipworms and hookworms. There are many other worms that are of less economic value. This post will focus on the worms of concern that can impact on life and death.

Intestinal worm (helminth)

Worms affect people of all ages but are more common in children. Maybe due to their poor hygienic nature. Latest estimates indicate that more than 880 million children are in need of treatment for these parasites. About 135000 people die annually from soil transmitted helminthiasis (SHT). In sub-Saharan Africa (SSA), there were 866 million people infected by STH as indicated by the World Health Organization estimate 2012: the respective number (prevalence) of people infected by hookworm, ascariasis lumbricoides, and trichuris trichiura was 117 million (13.6%), 117 million (13.6%), and 100.8 million (11.6%), respectively. According to a study performed in April 2008, the epidemiology of nematodes in developing regions of Asia, Africa, Latin and America as follows: ascariasis lumbricoides (807 millions), trichuris trichiura (604 millions), hookworm (576 millions) and strongyloides stercoralis (30–100 millions)

Nematodes

Roundworms

Roundworms are ascariasis lumbricoides. They are the largest and most common nematodes. The adult female is between 20-35cm in length. Adult males come between 15-30cm in length. They live in the lumen of the intestine. Females produce up to 240000 eggs per day. The eggs pass down with faeces. Fertile eggs become infective after 28 days to several weeks if the environmental conditions are favourable. Eggs survive in moist, warm and shaded soil.

Infections begin with ingested eggs. The eggs hatch, invade intestinal mucosa and are carried via the portal, then systemic circulation to the lungs. They live in the lungs for another 10-14 days before they penetrate the alveolar walls, ascend the bronchial tube to the throat. Again, they get swallowed and go back to the small intestine but this time as a mature roundworm.

The life circle is simple. It takes about 2-3 months from egg to adult and live for one to two years.

Pharmacotherapy/Treatment

1. Pyrantel pamoate

2. Albendazole

3. Mebendazole

Hookworm

This worm is the second most common cause of worm infection in humans. They are responsible for about 20 percent of worm infection worldwide. There are two species which are ancylostoma duodenale and necator americanus. Adult females achieve a length of 10-13 mm for ancylostoma duodenale and 9-11 mm for necator americanus.

They are more common in places that have the moist, warm climate like Africa, Asia and America. Necator americanus dominates America's while ancylostoma duodenale is found in the Middle East, north Africa and southern Europe.

Adult worms live in the lumen of the small intestine where they are attached to the intestinal wall. This leads to loss of blood of the host. Eggs pass through stool which then hatch in the feces or soil in 1-2 days. The larva grows in 5-10 days and becomes ready to infect humans. It can survive in this state for 3-4 weeks if the environment is favourable.

They penetrate the skin, enter the vein to the heart and lungs. They migrate to the pulmonary alveolar, ascend the bronchial tube to the pharynx before getting swallowed tuning into adult worms.

It takes about 5 weeks from infection to becoming an adult hookworm. They can live between 1-2 years and in some cases, several years. Ancylostoma duodenale species can be dormant in the intestine or mucosa. The skin is not the only route of infection as it can also be ingested leading to infection.

One of its major symptoms is chronic anemia.

Pharmacotherapy/Treatment

Albendazole

Whipworms

The third most common infectious worm is the whipworm called trichuris trichiura. It is a nematode affecting more than 400 million people. It can grow up to 4 cm in length. They live in the cecum and ascending colon. Female worms live in cecum sheds between 3000-20000 eggs every single day and pass out with stool. Infection is caused by ingestion of eggs which will later hatch in the small intestine releasing larva. The larvae mature and establish as adults in the colon. Adult worms fix their exterior portions threads into the mucosa. Females begin to release eggs 60-70 days after infection. Their lifespan is within a year. They can cause anemia, shock in the face or eyes, breathin, heart problems, chills, joint pain and muscle pain.

Pharmacotherapy/Treatment

Albendazole is the drug of choice

Pinworm

Another nematode of the species enterobius vermicularis which was previously known as oxyuris vermicularis. Adult females grow up to 8-13 mm and males have a length of 2-5 mm. They look like small threads of white cotton the size of a staple. With 40 million cases in the United States of America, USA and 10-50 percent in Australia children, humans seem to be the only host.

Adult worms live in the lumen of the human colon by attaching to the intestine lining. The female migrates at night to the anus where it lays its eggs in the skin of the perianal areas. The larvae in the egg develop in about 4 hours under optimal conditions. The larva hatch in the small intestine and adults establish themselves in the colon. They have a lifespan of 2 months and take about a month from infection to adult life.

Diagnosis is the use of anal swab or swub test with adhesives place over the anus to pick up eggs. The tape is viewed under the microscope. Also, stool, urine or vagina smear can be analysed forp presence of eggs. Adults can be found in anal and vagina area. Major symptoms is itchy anal and vagina area. Pinworms cannot be contracted from animals but pets around the house should be dewormed.

Another species less talked about is the strongyloides stercoralis. Causing the disease strongyloidiasis, an estimated 30–100 million people are infected worldwide. Strongyloidiasis is frequently underdiagnosed because many cases are asymptomatic. Affect most people with weak immune system. Infection is through the skin when walking barefooted. Strongyloides specie larvae penetrate the human host and reach the intestine where they mature into adults and produce eggs; the eggs hatch in the gut lumen and yield larvae that are evacuated in faeces. Some larvae are not excreted but reinvade the intestine or perianal skin to perpetuate the infection. Symptoms can show on in the skin as urticaria or in the lungs as wheezing.

Pharmacotherapy/Treatment

Pyrantel pamoate is suitable for enterobius vermicularis. However, Ivermectin, thiabendazole and albendazole are the most effective medicines for treating the strongyloides stercoralis. Albendazole is considered the least effective. Ivermectin, the drug of choice, is not available in all endemic countries.

Cestode

There are many species of cestode. The most prevalent of economic value are the tapeworm.

Tapeworms

Taenia saginata (beef tapeworm) and taenia solium (pork tapeworm) are the two types that cause human worm infection. Taenia solium is more prevalent in developing countries. This is because pigs are common in many developing countries. It is very rare in Muslim community. There are about 1000 new cases of tapeworm infection every year.

Humans are the only host of taenia saginata. The adult tapeworms are up to 25 m in length. They live in the small intestine where they attach their scolex to the wall of the intestine. They produce proglottids. Mature proglottids are at the end of the worm. Each worm has up to 1000-2000 proglottids. Each mature proglottid contains 80000-100000 eggs. They detach when ready and pass with stool. They eggs are released in the feces. Eggs can survive for years if the environmental conditions are favourable. They are ingested by animals where they migrate to the striated muscle. In the striated muscle, it develops into cysticercus (larva form of tapeworm). The larvae can survive for years. Human infection is possible when humans eat undercooked or raw infected meat.

Cystericus develop over 2 months into adults which can survive more than 30 years.

Taenia saginata length is 2-7 m with less than 1000 proglottids. Each proglottid contains about 50000 eggs and lives for about 25 years. Cystericus develop in striated muscle, brain and other tissues in other animals including pigs and humans.

Pharmacotherapy/Treatment

Tapeworm can disappear even without treatment with strong immune response. However, treatment is the use of praziquantel.

Trematodes

So many species fall into this. But they are not very important.

Fluke

They have the shape of a rounded leaf. They invade the liver and bile duct. They include fasciola, paragonimus, westermani, schistosomes, oriental liver flukes, heterophyes and metagonimus yokogawai

Pharmacotherapy/Treatment

Triclabendazole

Pharmacotherapy/Treatment

Triclabendazole or any other anthelmintic works.

Summary Of Pharmacotherapy/Treatment

1. Tapeworms treated with praziquantel. Praziquantel makes the tapeworm detach from the gut, dissolve and pass out.

2. Nematodes are treated with either ivermectin, mebendazole and albendazole.

3. Fluke treated with triclabendazole

The drugs are not effective against immature worms or eggs. Treatment should be repeated after two weeks when the immature worm and eggs would hatch and become mature to respond to treatment. In some cases, a single dose does the job. However, some treatment will require daily doses up to 8-28 days.

Macrocyclic lactones (ivermectin) can be used for adult and migrating larva This medication is used to treat certain parasitic nematode infections. Praziquantel is used for schistosomiasis, taeniasis, and major food borne trematodes. Oxamniquine is also a drug of choice for mass deworming when schistosomiasis is prevalent.

The world health organisation (WHO) recommend that annual treatment in areas where soil transmitted intestinal worms  (excluding threadworms) affect 20-50 percent of the population. Biannual is recommended if the infection rate is more than 50 percent. Now, the idea of deworming every 3 months is wrong.

Read Also: Treatment or Pharmacotherapy of parasitic skin infections

Prevention

1. Keep fingernails short at all times

2. Cook food properly. Cook meat to 72°c for cut meat and 71°c for ground meat. Freeze meat/fish to –20°c for at least 24 hours.

3. Wash fruit before eating. Peel outer skin fruit should be consumed immediately.

4. Simple hygiene

5. The use of shoes