Parasitic worm infections are common worldwide, affecting millions of people each year. These infections are caused by different types of worms that live inside the body and feed off the person they infect. Some of the most common parasitic worms include roundworms, tapeworms, flukes, and hookworms. While the symptoms can vary depending on the type of worm, there is one very common symptom that is present in most worm infections – abdominal pain and discomfort.
What are parasitic worms?
Parasitic worms, also known as helminths, are multicellular organisms that live inside the bodies of other organisms and derive nourishment from their hosts. There are many different types of parasitic worms:
- Roundworms – Roundworm infections are caused by nematodes. Some examples are ascariasis, trichuriasis, hookworm infection, enterobiasis, strongyloidiasis, and filariasis.
- Tapeworms – Tapeworms are flatworms that attach themselves to the intestinal wall. Examples are taeniasis and cysticercosis.
- Flukes – Flukes are flatworms as well but they have complex reproductive systems. Examples include schistosomiasis, paragonimiasis, clonorchiasis, fascioliasis, and opisthorchiasis.
- Whipworms – These are a type of roundworm infection that affects the large intestine. Trichuris trichiura is a common species.
These worms enter the human body through contaminated food or water, insect bites, or contact with infected feces. They travel to different parts of the body like the intestines, blood, muscles, lungs, liver and start causing an infection.
Prevalence of parasitic worm infections
The World Health Organization estimates that over 1.5 billion people or 24% of the global population are infected with soil-transmitted helminths like roundworm, whipworm and hookworm. These are most prevalent in tropical and subtropical areas with poor sanitation practices.
Some key facts about the prevalence of parasitic worms:
- Over 807-1,221 million people are infected with roundworms worldwide
- Whipworms infect about 604-795 million people around the globe
- Hookworms affect 576-740 million people
- Over 90 million people are infected with lymphatic filariasis
- Schistosomiasis affects almost 250 million people
- Tapeworms like Taenia solium and Taenia saginata infect 50 million people
These infections are most common in areas with warmer climates where sanitation and hygiene practices are poor. Children are at a higher risk as they play outdoors and can accidentally ingest contaminated soil.
How do parasitic worms infect the body?
Parasitic worms can enter the human body through different routes:
- Ingestion – Consuming contaminated food or water that contains worm eggs or larvae. This allows the immature worms to hatch, enter the digestive tract and mature. Examples are ascariasis, tapeworm infections, and giardiasis.
- Penetration – Larvae can penetrate the skin directly and enter the bloodstream. Hookworm, threadworm larvae use this route.
- Insect bites – Some worms are spread by insect vectors like mosquitoes. Lymphatic filariasis and onchocerciasis spread this way.
- Skin contact – Eggs of schistosomes, threadworms and whipworms can enter through contact with contaminated soil and feces.
Once inside the body, the worms travel to different organs like the intestines, bladder, lungs, liver, heart and start causing an infection. They derive nutrition from the person they infect and often cause great damage to organs before causing any symptoms.
What are the symptoms of parasitic worm infections?
The symptoms of worm infections can be vague and nonspecific in the beginning. They include:
- Abdominal pain – Most worm larvae and eggs travel to the intestines initially after entering the body. This causes inflammation and irritation of the intestinal lining. Abdominal discomfort, cramps, and tenderness are very common.
- Diarrhea or dysentery – Worms invading the intestines can disturb digestion and absorption of food. This leads to loose, watery stools with mucus and blood at times.
- Vomiting and nausea – Roundworm and tapeworm larvae migrating through the intestines stimulate the gut lining. This causes nausea and vomiting.
- Cough and breathing difficulty – Larvae of some worms like hookworm and Strongyloides stercoralis migrate to the lungs. This causes a cough, wheezing and shortness of breath.
- Itchy rash – Worm larvae invading the skin like hookworm and Strongyloides cause red, itchy rashes at the site of entry.
- General weakness and fatigue – Parasitic worms feed off the person they infect and cause anemia due to intestinal blood loss. This results in tiredness, lethargy and weakness.
- Weight loss – Infections lasting months to years can lead to poor appetite and weight loss.
However, most worm infections do not cause any symptoms initially. They are often diagnosed incidentally when Investigating other problems.
Abdominal pain and bloating as most common early symptoms
According to the Centers for Disease Control and Prevention (CDC), the most common early symptom of most worm infections is abdominal pain, discomfort, and bloating. There are a few reasons why this occurs:
- The larvae and eggs of worms like roundworms, whipworms, hookworms and tapeworms travel to the intestines after entering the body. Here they attach to the intestinal lining, mate and produce eggs.
- This leads to inflammation and irritation of the intestinal mucosa causing cramping, pain and tenderness.
- As the worms feed and move inside the gut, they cause mechanical obstruction. This stimulates the intestinal muscles and disrupts normal movement of food.
- Whipworms like Trichuris trichiura cause inflammation and bleeding from the rectum. This is very painful.
- Some worms like Strongyloides stercoralis penetrate the gut wall itself. This causes severe irritation and discomfort.
According to a 2017 review published in Tropical Medicine and International Health, abdominal symptoms were among the most frequent complaints of patients with soil-transmitted helminths. Abdominal discomfort was reported by:
- 76% of patients with Ascaris lumbricoides infection
- 40% of patients with hookworm infection
- 52% of patients with Trichuris trichiura infection
Table showing prevalence of abdominal symptoms in different worm infections:
| Parasitic infection | Prevalence of abdominal pain |
|---|---|
| Ascariasis | 76% |
| Hookworm | 40% |
| Whipworm | 52% |
| Tapeworm | 65% |
| Schistosomiasis | 15-23% |
A study published in PLoS Neglected Tropical Diseases in 2014 done in Tanzania also found abdominal pain to be the most frequent symptom in children infected with hookworms and Schistosoma haematobium. Abdominal discomfort and tenderness on palpation was reported in over 50% of cases.
Thus abdominal symptoms like pain, cramps, bloating and distension seem to be the most common early manifestations in a wide variety of parasitic worm infections.
Other common symptoms
Along with abdominal discomfort, worm infections can also cause other nonspecific symptoms like:
Diarrhea and Digestive Issues
The presence of worms in the intestines leads to inflammation of the gut mucosa, impaired digestion and malnutrition. Stools often become loose, watery and foulsmelling and may contain blood and mucus. There may also be intermittent diarrhea with constipation.
Cough and Breathing Difficulty
Larvae of some worms like hookworm, Ascaris, Strongyloides and Paragonimus migrate to the lungs. Here they rupture alveoli causing bleeding. This manifests as a dry cough initially which can later become productive with blood. Wheezing and shortness of breath can also occur.
Itchy Rash
As worm larvae enter through the skin like in cutaneous larva migrans, they can cause intense itching and papular eruptions. These rashes are usually seen on the legs and feet in areas that come in contact with contaminated soil.
Fever
The migration of worm larvae through different organs and the immune response they elicit can result in low grade fevers along with chills, sweating and joint pains.
Fatigue and Weakness
Parasitic worms live off the person they infect and feed on blood, minerals and vitamins. This leads to anemia and protein loss over time. General tiredness, lethargy, muscle cramps and poor concentration become common.
Weight Loss
Gastrointestinal blood loss, diarrhea, nausea and poor nutrition due to worm infections often lead to significant weight loss. This is more apparent in long standing cases.
Eye Symptoms
Larvae of some parasitic worms can migrate unexpectedly to body organs like the eyes. This can cause inflammation, vision changes and severe symptoms. Cysticercosis infection is linked to vision loss when the larvae infect eyes.
Skin Changes
Penetration of skin by worm larvae results in visible signs like itchy wheals, hives, swelling and redness. Skin hardening and thickening is seen in lymphatic filariasis. Abscesses under skin can occur with cysticercosis.
Neurological Symptoms
Worm larvae migrating to the central nervous system, which is uncommon, can cause symptoms like seizures, focal deficits and headaches.
So in summary, parasitic worm infections have a wide array of nonspecific symptoms involving many organs. But abdominal discomfort is usually one of the earliest and most frequent complaints.
Diagnosis of parasitic worm infections
Due to their vague, overlapping symptoms, parasitic worm infections are not very straightforward to diagnose. Some key methods used are:
- Microscopic examination of feces – This is done to identify worm eggs and larvae passing in stool. But many infections do not shed eggs or larvae initially.
- Antigen detection immunoassays – Blood or urine is tested for the presence of substances secreted by worms. This has good sensitivity.
- Molecular tests – PCR based assays on stool or tissue samples can detect worm DNA accurately.
- Imaging studies – Ultrasound, CT and MRI scans help visualize worms in organs and detect complications like cysts, abscesses, cirrhosis etc.
- Biopsy – Microscopic examination of infected tissue obtained via biopsy allows identification of worm eggs and larvae.
- Immunological tests – These detect antibodies the body produces against worms. Not very sensitive in endemic areas.
Often a combination of laboratory tests along with imaging is required to reach the right diagnosis. Clinical suspicions also play a major role based on symptoms and travel history.
Complications of parasitic worm infections
If not treated on time, chronic worm infections can result in severe complications:
- Anemia – Hookworm infections are notorious for causing iron deficiency anemia and protein loss.
- Malnutrition – Vomiting, diarrhea, poor absorption due to worms worsens nutritional status.
- Bowel obstruction – Massive roundworm infections can obstruct the intestinal lumen.
- Rectal prolapse – Chronic Trichuris infections cause prolapse of rectal mucosa.
- Biliary and liver disease – Flukes cause chronic inflammation of bile ducts, gallbladder and liver fibrosis.
- Bladder fibrosis – Eggs of Schistosoma haematobium cause bladder wall fibrosis and calcification.
- Portal hypertension – This results from liver fibrosis caused by Schistosoma mansoni eggs.
- CNS disease – Rarely larvae can migrate to the brain and spinal cord causing severe reactions.
- Eye disease – Ocular cysticercosis can damage vision permanently.
Growth retardation, cognitive dysfunction, and seizures are seen in children with chronic worm infections along with pneumonia, encephalitis and sepsis from co-infections.
Preventive strategies against worm infections
Public health measures play a major role in controlling parasitic worm infections:
- Improving sanitation infrastructure and access to clean water prevents fecal contamination of soil and food.
- Deworming programs should target high risk groups like children, pregnant women and workers exposed to unsanitary conditions.
- Wearing shoes outdoors, washing hands before eating, and avoiding eating raw or undercooked meat help prevent infections.
- Vector control by clearing stagnant water pools and insecticide spraying decreases cases spread by mosquito bites.
- Screening donated blood products, enforcing food safety standards, and public health education are key.
- Treating infected individuals promptly prevents further spread and reduces worm burden in endemic communities.
Vaccine development efforts are also ongoing for common worm infections like hookworms, schistosomiasis, onchocerciasis and lymphatic filariasis. This will be a major advance in controlling these infections long term.
Treatment options
Several effective oral medications are available to treat different parasitic worms:
- Albendazole is used for roundworm, hookworm, whipworm and tapeworm infections.
- Mebendazole, pyrantel pamoate and levamisole treat roundworms and hookworms.
- Praziquantel is effective for tapeworms and flukes like schistosomes.
- Ivermectin treats roundworm infections and is the drug of choice for filariasis.
- Nitazoxanide is used for cryptosporidium and giardia infections.
Depending on the type of worm, treatment may be a single dose or require several days of therapy. Supportive treatment for complications like anemia and dehydration is also needed. Stool testing after treatment checks effective cure.
Public health programs periodically deworm entire communities in endemic areas to reduce overall transmission. Proper disposal of feces, hand hygiene practices, and avoiding contaminated food and water prevents reinfection.
Conclusion
Parasitic worm infections are very common globally but often go unrecognized. Abdominal discomfort is usually the earliest and most frequent symptom, though systemic manifestations can also occur as larvae migrate through the body. A combination of laboratory tests helps in diagnosis.
Ongoing public health strategies like preventive chemotherapy, sanitation infrastructure improvements, vector control and health education are key to control worm infections in endemic countries. Periodic deworming and prompt treatment of infections improves outcomes and quality of life. But a more integrated approach targeting risk factors like unsafe water and inadequate sanitation is needed for effective long-term control.