Human Intestinal Worms – Symptoms, Pictures, Treatment

What Are Intestinal Worms (Helminths)?

Human intestinal worms are parasites that live in the human intestine, eat bowel content or suck blood from the intestinal wall.

Intestinal worms may cause severe, life threatening infection, predominantly in children in tropical and subtropical areas where people often defecate on the ground: in rural parts of Africa, Middle East, South Asia, Indonesia and Central and South America. In people from Mediterranean parts of Europe or south parts of North America, they usually cause a relatively mild disease.

Presence of parasites of any kind (including intestinal worms) in or on the body is called infestation.

Helminth is a medical term for intestinal worm.

Symptoms of Infestation With Intestinal Worms

Intestinal worms may live in someone’s intestine for years without causing any symptoms. General symptoms may appear few weeks or several months after infestation and include paleness, weakness, tiredness (from anemia due to lost blood sucked by worms), restlessness, disturbed sleep and weight loss (due to loss of nutrients used by worms). Abdominal symptoms can last from weeks to months and include:

Sources of Worm Infection

Worm eggs, shed in the stool of humans or animals infected with adult worms, can contaminate soil or water. Once outside the body, eggs need several days or weeks to develop into the infective stage (cysts) or immature worms (larvae) that may be ingested when you eat with soil-contaminated hands or when you eat raw unwashed vegetables. Another source of intestinal worms is undercooked infected meat of domestic pig, freshwater fish or wild animals (bear, walrus, etc.). One can also be infected by ingesting dog’s fleas that have ingested parasitic eggs. Children may contract infection from sandboxes contaminated with pets’ stool. Certain types of immature worms may penetrate through your skin during swimming or walking barefoot; when they reach the small or large intestine they grow into adult worms.

Common garden worms usually do not cause illness in human. 

How Intestinal Worms Cause Disease?

Adult worms, which may be from 1 millimeter to several meters long, invade the bowel wall and suck the blood from it, or live freely in the intestine and utilize nutrients from the bowel content. The result are small intestinal or colonic inflammation and ulcers, anemia, and protein, iron and vitamin (mainly A, C, B12) deficiency. Intestinal obstruction may occur in severe cases. Larvae may migrate to other organs (liver, spleen, bladder, muscles, lungs, brain), where they form cysts and trigger allergic inflammation.

Common Human Intestinal Worms

A. Roundworms (Nematode) (1)

  • The large roundworms (Ascaris lumbricoides) are found worldwide. They are several inches long and thick as a pencil (Picture 1).
  • Hookworms (Necator americanus, Ancylostoma duodenale) are mostly found in tropical areas; they are about a half of inch long; they may be contracted by walking barefoot – they penetrate through the skin. Once in the intestine, they suck blood from the intestinal wall.
  • Whipworm (Trichuris trichiura), causing trichuriasis
  • Threadworms
    • Strongyloides stercoralis
    • Pinworm or seatworm (Enterobius vermicularis) is half an inch long, white  worm; its egs cause anal itch.
  • Trichinella spiralis, causing trichinosis, may be acquired by eating undercooked contaminated pork meet. Parasites move from the intestine into muscles and other organs where they form cysts – encapsulated forms, which are hard to eradicate. Main symptoms are abdominal pain, muscular and joint pain, swelling of the eyes and skin rash.

Roundworm - Ascaris lumbricoides

Picture 1. Roundworm –Ascaris lumbricoides (several inches long)

B. Flukes (Trematoda)

  • Schistosoma mansoni causes intestinal schistosomiasis (bilharziasis), mainly in Africa, Middle East, Caribbean and South America. It is about half an inch long and 1 millimeter thick. Adult parasites live in intestinal veins and release eggs into the intestinal hollow. Diagnosis is by finding eggs in the stool and urine.

Swimmer's itch - schistosome dermatitis, caused by flukes

Picture 2. Schistosome dermatitis (swimmer’s itch) –
– a rash on the lower arm on the sites of parasite entry

C. Tapeworms (Cestoda)

  • Fish (broad) tapeworm (Diphyllobothrium latum) is contracted by infected freshwater fish; it may exceed 10 m; it appears in Europe, Russia and US.
  • Beef tapeworm (Taenia saginata) (Picture 3) and pork tapeworm (Taenia solium) may be contracted by undercooked beef or pork – mainly in rural areas, worldwide. Adult worms may be over 20 m long.
  • Dog tapeworm (Dipyllidium canium) is common in dogs and cats. Humans are (rarely) infected by ingesting dog fleas, infected with tapeworm larvae. Rice sized particles can be found in the stool.

Dog tapeworm - Taenia saginata

Picture 3. Beef tapeworm – Taenia saginata (several meters long)
(source: Wikimedia)

Trichicara cati or Trichicara canis can be attracted by ingesting eggs in cat’s or dog’s stool. After ingesting they develop into larvae that migrate through the body organs, like lungs. Common symptoms are fever and cough.

How Are Intestinal Worms Diagnosed?

If you suffer from unexplained abdominal bloating, diarrhea, weakness or weight loss, your doctor should suspect intestinal worms (or other intestinal parasites) as a possible cause. Diagnosis is confirmed by stool test for ova and parasites (O&P test). Hemoccult can reveal blood in the stool. Blood tests can reveal anemia (low ferritinand low red cells), low levels of vitamins A, C or B12, antobodies against certain worms, or elevated levels of eosinophils and IgEantibodies. Pinworm eggs from anal region can be collected by adhesive tape test.

Treatment of Intestinal Worms

A single dose of anti-worm drug, like mebendazole (safe for pregnant women), albendazole, diethylcarbamazine, ivermectin or praziquantel kills parasites in most cases. For some days after the healing, a stool-to-mouth auto-infection with eggs is still possible. Untreated infestations may last for years.

Prevention of Intestinal Worms

The following should prevent you from attracting intestinal parasites:

  • Wash the hands after visiting toilet, touching soil or pets, and before meal
  • Tell kids to avoid touching mouth and nose with their hands
  • Do not walk barefoot and swim in lakes in tropical areas
  • Avoid suspicious restaurants with poor hygiene
  • Cook meat and fish well


  1. Parasitic roundworms  (
  2. Bilharziasis  (
About Jan Modric (249 Articles)
Health writer

Please note that any information or feedback on this website is not intended to replace a consultation with a health care professional and will not constitute a medical diagnosis. By using this website and the comment service you agree to abide by the comment terms and conditions as outlined on this page

  • Hardik

    Hello there,

    I am 23 years Old. No matter how much i eat or consume i never gain weight and i am underweight. Anything i eat over my limit it comes out after an hour or so. I do have a gas problem happened recently. I am vegetarian and have my meals regularly. I have also tried increasing my diet weekly to consume more food but nothing is working still same weight etc. I was wondering is it because i might have worms etc?. I remember faintly when i was young at age of 7 i did had worms but not anymore havent seen lately.

  • Jan Modric


    worms or other intestinal parasites can be diagnosed with a stool test for parasites. Certain food intolerances, like celiac disease, lactose intolerance or fructose malabsorption can cause diarrhea. You may have specific diet trials (check links), lasting for 3-4 days each to see if it helps.

    Here’s an article about weight gain in vegetarians, but you should exclude above mentioned disorders before considering that.

  • k66

    I have had intense abdominal pain for about 3-4 weeks, just recently started having diarrhea, and I have gained weight. Been to the doctors and to the hospital, the assumed it was 1 of three things, bladder infection-negative, ovarian cists-negative, or kidney stones. The pain is still pretty intense at times it comes and goes but I always am in some kind of pain.
    Please give me some answers I am only 17 years of age and I am tired of feeling like a very aged women. Please give me some advice!!

  • Jan Modric


    intestinal parasites can be diagnosed by a stool test for parasites and treated by prescribed antiparasitic medications. Telling where exactly do you feel pain, are your kidneys tender when tapping them with a fist, and do you have any other symptoms, fever, nausea…could help to narrow down the possible causes.

  • Mr Shawn Bucc

    Hello Jan, I am a curios reader and I have a list of issues that i think may be parasites. It all started about 10 years ago when I drank river water in Jamaica. I was sick for a week straight after that. Since then I’ve had trouble breathing at times, my right ear pops like im on an airplane, my eye twitches sometimes, I feel pains in my midsection, I sometimes get short term blurred vision, I have an on and off chest pain and I also feel a crawling feeling up my back and in my midsection. I also get a bloated feeling in my midsection. I have also had pitorius rosea 2 years ago and I believe that it was connected to some form of parasite(s). I feel little itch pains all over that feel very strange and sometimes I have episodes where I feel things moving all arond my body and even up my spine to my brain. I would like to also note that my mouth gets very dry and my vision is worsening. I have had blood and stool test but the doctor has only diagnosed me with one thing. She said that my bilirubid levels were “slightly” higher than normal and I don’t have parasites. I do know that some parasites cause jaundis and I am VERY scared. Please help me. Do you think I may have parasites that theese tests missed? Thank You

  • Jan Modric

    Mr Shawn Bucc,

    to diagnose parasites in the liver, an ultrasound of the liver might be needed. If the itch is related to parasites, eosinophils (a type of white blood cells) and IgE antibodies in the blood could be elevated. A single negative stool test does not exclude parasites.

    On the other hand, you symptoms could be neurological (eye twitching, blurred vision, abnormal sensations), or due to a certain connective tissue disorder (like SLE). Specific blood tests can reveal them.

  • Megc

    Hi. I was treated for worms around age 7 (not sure what kind, but my anus itched.) Around 15, I had same problem, but was just embarassed, removed and cleaned regularly until I didn’t notice any more. I’m now 27 and have 3 children (ages 7, 4, and 4). My son told me about a month ago that he ate fleas off of holly (our dog) during one nap time. Not sure if that’s related other than I know dogs get worms. I’m sort of wondering if I never got rid of them though. I’ve had all sorts of re-curring health problems from vaginosis, bedwetting (my son started this about 6 months ago for no noticeable reason), itchy anus, ibs, mucus in stool. Anyway, i found worms in my sons rear last week as he complained that it itched. I went to the emergency room and they wrote us all a “deworm” prescription (just one pill, although I’ve read that it takes several doses sometimes.) I’m disturbed because the worms being treated are very small and white…but I just had a several inch long worm come out. I used to love eating raw groundbeef as a child (gross I know, but my mom let me and did as well) as well as eating sushi. I’m not sure if it’s related, but i’m trying to give any information that may be helpful. I was referred to as the “MS ethiopian” since my teens since I’m 5″8 and only 100lbs. Any help, knowledge, suggestions for ridding us of this (or multiple?) infestations? I don’t have health insurance and hesitate to go back for 1 pill if it’s not enough or there are other treatments. I’m freaking out. Please help.

  • Jan Modric


    certain types of antiparasitic medications require only one single dose; it could help if you can tell which exact med is it. Dog flies, raw meat, unwashed fruits and vegetables, drinking water from the river…can all be sources of intestinal parasites.

  • Norman

    I have had loose/soft stool and the occasional diarrhea for the past 2 months now, horrid smelling flatulence and breath, bloating (or I could just be gaining weight >.<), and I find myself tired halfway through the day despite getting a good night's rest often. Whenever I had diarrhea, it was always accompanied with fecal incontinence and I could not differentiate flatulence from stool during the time. Even during times without diarrhea it felt like a little came out whenever passing gas. It came to the point where I had to keep approx. 6-10 sheets of toilet paper folded up and held between my butt-cheeks just to make sure I didn't soil myself since I had to go to classes and couldn't get off campus until after at least 4 hours, which by then I would've already had an accident as it happened nearly every time I passed gas within those periods. No one in my family has had the same problems so we don't think it's the food, and allergies don't seem to be the culprit either since we've stuck to the same diet for nearly my entire life. I haven't been sent to a doctor since my family finds it pretty minor. Could this be caused by intestinal parasites?

  • Mr SB

    Hello Jan, It is Mr SB again from 11-14-10 and this comment is to update you on my progress. My symptoms are getting more wird. I now have a more monotored description. The pain starts in my chest then it works its way to my right ear (feels like im on a plane)then it works its way to my head. I still feel like there is movement in my head. I also still have eye twitching. The pain is never in more than one spots at the same time. It always moves. When I eat, the pain leaves my ear and moves to my stomach (where itching occurs). Also, my ultrasound of my liver came back. The doctor said my liver is enlarged. I am very concerned because the doctor acts like she dosen’t care. I am afraid that the river water I drank in Jamaica is catching up to me. Do you suggest any parasite cleanses that I can buy online or at a pharmacy? Thanks Jan!!!

  • Jan Modric


    yes, parasites would be possible. Other possible causes of diarrhea and “horrid smelling flatulence”:
    – a liver or bile duct disorder – in this case the stool would be whitish and/or foamy and/or sticky and floating (due to unabsorbed fats)
    – small intestinal bacterial overgrowth (SIBO)
    – overgrowth of a bacterium Clostridium difficile – this often results in a barnyard smelling gas.

    I strongly recommend you to visit a gastroenterologist.

  • Jan Modric

    Mr SB,

    elevated bilirubin and enlarged liver may speak for a liver disorder, so a gastroenterologist should be able to came to some conclusion. I’m not aware of any safe and effective non-prescribed antiparasitic medication. ear popping disappearing during eating may speak for an elevated pressure in the middle ear – an ENT could say if there is any underlying disorder.

  • LSC

    Hey Jan,

    I don’t know if I have worms or not but these are some wierd things that are happening to me. I can’t gain weight. I’m 117 right now. Ive had trouble sleeping because I feel tiny movements in my stomache and at times I tend to burp alot. I’ve been doing some research on my own and have found that these may be symptoms of worms I just wanted to know wht do you think of these symptoms?
    In my past I’ve been known to have a fast metabolism so I’m thinking it could be that or it could be an infestation.

  • Jan Modric


    fast metabolism itself may make gaining weight hard. Excessive burping may speak for a stomach infection with Helicobacter pylori, slow stomach emptying (gastroparesis), intestinal parasites, fructose malabsorption – you can find more details in this article about excessive burping.

  • j.collins

    a few weeks sgo i a mild case of food poisoning. since then ive had diarreha that comes suddenly and is almost always only water, followed by a day of constapation and then diarreha again. i have an itchy anus especially when laying in bed at night. im always tired and also have insomnia. i have an inconsistant appitite and have lost about 8 pound since this started. could it be anything other then a parasite?

  • Jan Modric


    food poisoning related diarrhea lasting for more than a week is usually caused by parasites. Bacterial or viral diarrhea usually heal on their own within a week. All other symptoms you’ve mentioned can also occur in intestinal parasites. I can’t exclude other causes, though. A gastroenterologist can confirm a diagnosis of parasites with a stool test.

  • me*

    i have a real hard time useing the bathroom. i cant poop. i looked at it today and it had tiny holes all through it, there was also somthing white in it to but i dont know what. can anyone tell me what to do. i feel tired and crappy all the time.

  • Jan Modric


    a gastroenterologist can order a stool test for parasites or some other test, if necessary.

  • ak

    hi Jan,

    today I found a red bit lodged in my stool that was just under 1cm long. being really curious as you can imagine I squeezed it a bit and it was hard but white in the inside a consistency like white bread?! Sorry this is gross but I’m totally confused here. I have not eaten anything that could cause this, and I don’t know what it is…? Could it be a worm egg of some sort (though I would think parasite eggs would be quite small!) Also the stool did have a strange odour unlike my other stools which tend to have a slightly metallic scent. Besides that the stool was normal in size and colour. Any ideas?

  • Liz

    I have IBS,but for past 2 wks I have been having severe intermitent abdominal cramps & either soft or very loose bowel movements. In bed at night I get strange feelings in my stomach, almost as if something is moving around inside. Yesterday while out shopping I had a very loose BM & when wiping myself noticed a flat beige wormlike thing approx.3″ long(looked almost like spaghetti)but was hard.I have had both blood & mucus in my stools & foul gas past 2 wks. Never had this many problems at once with my IBS. Diet has not changed

  • Kelly

    I just had a BM and found what looked to be a white round worm next to my stool. it was about 2 inches long. What should I do?

  • Dr. Chris

    Hi Kelly

    Many adults often report the sight of worms in the stool and it is usually some undigested food or other cause but not worms. This is not to say that this is definitely the cause in your case. If you could retrieve the “worm” then this would be helpful. Alternatively, see a doctor who may consider further investigations like a stool test to confirm the presence of an intestinal parasite or just commence with treatment anyway.

  • Dr. Chris

    Hi Liz

    Acute exacerbations with IBS is not uncommon and may account for some of your symptoms. However what needs to be excluded here is whether you have IBD and not IBS. Inflammatory bowel disease like Crohn’s disease or ulcerative colitis often appear as IBS in the early years. You need to investigate this immediately. “Worm-like things” in the stool are not often actual human intestinal worms. Undigested food, mucus and so on are more likely causes of “unusual sightings” in the stool. Nevertheless it is a possibility and your doctor may request a stool test to detect ova in the stool which will settle the matter as to whether it is an intestinal parasite.