STD parasites infected with viruses

Several parasites of humans

Last month’s case study about virophages, where a species of amoeba was found to be infected with a virus, which in turn was infected with a virus, was interesting but really pretty much an exercise in “Wow! That’s interesting” as opposed to something that might feel clinically important. Not so today! Via Boing Boing, from an article on Live Science, a report about viruses that infect Trichomonas, the causative agent of a very common venereal disease.

Trichomonads are interesting in their own right; they are eukaryotes like us, classified in the broad group of single-celled flagellated protozoans, however they are anaerobes. A little cursory research indicates that this class of protozoans lack fully functioning mitochondria. This suits the lifestyle of Trichomonas vaginalis, which colonizes the surfaces of the vaginal tract in humans. It is then transmitted between sexual partners and can spread through the population via non-monogamous means. On its own, Trichomonas infection is not particularly severe, however women infected with this organism are more susceptible to other STD infections, and pregnancies are significantly more risky with a high frequency of preterm complications and miscarriages.

Researchers at Harvard Medical School recently published their findings about Trichomonas in the medical journal PLOSOne, which have been summarized in the Live Science article above. They found that about 80% of clinical Trichomonas isolates were themselves infected with an endosymbiotic virus now called Trichomonasvirus. Comparison of disease between individuals infected with the virus-free Trichomonas tended to have less significant disease than those infected with virus-containing Trichomonas. This offered preliminary results to suggest that the virus conferred virulence traits to Trichomonas in the process of disease. This is not a new idea (virus-infected isolates of Vibrio cholerae are able to cause cholera, whereas virus-lacking isolates are avirulent), however this is one of the first demonstrations of this relationship with a eukaryotic pathogen and the development of disease. With this critical observation in mind, the researchers began to examine the mechanism.

They found that virus-infected Trichomonas was detected by Toll-like receptor 3 on the epithelial cells of the vaginal tract. According to lecture, TLR-3 is a pattern recognizing protein that specifically recognizes double-stranded RNA molecules, which is what the genome of Trichomonasvirus is composed of. Binding of TLR-3 triggers a cascade of soluble messengers including type I Interferon, resulting in an inflammatory cascade, which have previously been found to be involved in preterm labor and HIV susceptibility. Alarmingly, the standard of care for Trichomonas infection in women, the anti-protozoan antibiotic metridnazole, exacerbated these effects. The authors recommend that a new approach in the treatment of these infections might be necessary. Specifically targeting the virus infection of Trichomonas might help to avoid some of the complications of these STDs.

Bonus time, as I am becoming depressed over the lack of commenting here on the blog. Note that this will be a limited time offer, only through the end of this week (noon on Friday November 16.) For bonus credit on the clicker quiz–same deal as before–comment below by naming a protozoan disease of humans, and the etiologic agent of that disease. We will see some of these in lab this week, so this is timely. Duplicate entries will be disallowed!


About ycpmicro

My name is David Singleton, and I am an Associate Professor of Microbiology at York College of Pennsylvania. My main course is BIO230, a course taken by allied-health students at YCP. Views on this site are my own.

Posted on November 12, 2012, in Bonus!, Microbes in the News, The more you know and tagged , , . Bookmark the permalink. 33 Comments.

  1. Babesiosis is from the protozoal genus Babesia and can cause disease that tends to spring up during the warmer months of the year, and has become much more prevalent over the last decade. The cause of this is the well known parasitic vector, the tick. Many may go unaffected but for some it can be fatal. It often goes undiagnosed because the symptoms are similar to other diseases such as malaria. In just a short period of time, however, Babsiosis can cause jaundice, fatigue, kidney failure, etc. Treatment usually involves intense medical care which includes antimicrobials. Prevention for this is simple: check for ticks!

    Info from the CDC (2012) and Bauman (2011)

    • Babesia species can produce disease much like malaria, and the organism demonstrates a life style very similar to the malaria parasite. In fact, according to Wikipedia, Babeosis is referred to as the “malaria of the North East” because it’s endemic range is in the New England states. As Kaitlyn noted, it is not very common, however it is likely frequently under- or mis-diagnosed.

  2. Amoebiasis is a protozoan disease caused by Entamoeba histolytica. It secretes enzymes that dissolve the host’s tissues. Amoebiasis infection is spread by contact with feces, which can be found in contaminated food or water. Amoebiasis can occur without symptoms, but sometimes a person will experience bloody diarrhea and inflammation of the colon.

    • Also known as amoebic dysentery, in order to separate it from other forms of dysentery (which is actually a diagnosis, not a disease).

      Everyone will get the chance to spot Entamoeba in stool samples this week in lab.

  3. Giardiasis is a protozoan disease caused by the parasite known as Giardia intestinalis. This parasite is found in feces. Drinking contaminated water can also cause a Giardiasis infection. Symptoms include greasy stool, diarrhea, nausea, upset stomach and abdominal cramps.

  4. One protozoan disease is Leishmania. The original parasite of Leishmania is found in sand flies. This disease is hosted by both wild and domestic dogs and small rodents. From sand fly bites, humans become infected. Depending on the species, different effects can occur. These can range from large, painless ulcers to death. The best way to prevent this disease is spraying insecticide and destroying rodent habitation.

    • Leishmaniasis is one of the major protozoan diseases of sub-Saharan Africa and elsewhere in the tropics with 15 million new cases annually. Systemic infection results in depletion of macrophages, as the parasite infects and multiplies inside these critical immune cells. Patients can then become immunocompromised as macrophages diminish in numbers.

  5. Toxoplasmosis is a protozoan disease caused by Toxoplasma gondii. It doesn’t actually cause symptoms in most people who are infected but it can cause problems in someone with a compromised immune system or in babies born to mothers with toxoplasmosis. The symptoms are a lot like the flu and may include: aches, fever, fatigue, headache, sore throat and swollen lymph nodes.

  6. African Sleeping Sickness is caused by the protozoan in the Trypanosoma genus. Trypanosoma brucei rhodesiense in East Africa and Trypanosoma brucei gambiense in West Africa. It is usually carried out by infected tsetse flies and fly bites into humans. It can cause insomnia, confusion, seizures, weight loss, and irritability.

    • Members of genus Trypanosoma demonstrate a remarkable phenomenon called antigenic variation. As soon as a primary adaptive immune response occurs and produces antibodies, numbers of the organisms begin to diminish due to the effects of complement and phagocytes. Then, the organism essentially changes the antigens on its surface, and the antibody response no longer works! The patient gets sick again.

  7. Plasmodium falciparum is the Plasmodium species responsible for 85 % of the malaria cases. The three less common and less dangerous Plasmodium species are: P. ovale, P. malariae and P. vivax. Malaria infects over 200 million people annually, mostly in poor tropical and subtropical countries of Africa. Malaria is carried by Anopheles mosquitoes. Of the over 400 Anopheles species, only 30–40 can transmit malaria. After being bitten by an infected mosquito, symptoms usually begin within 10–30 days. Malaria can be uncomplicated or severe. Symptoms of uncomplicated malaria might include: chills, diarrhea, fever, headaches, muscle pain, nausea, sweating, vomiting, and weakness. The disease can turn into severe malaria, if there are serious organ failures or abnormalities in the bloodstream or metabolism. Symptoms of severe malaria might include: breathing difficulties, coma, confusion, death, focal neurologic signs, seizures, or severe anemia. Malaria is usually diagnosed by examining a blood sample under a microscope. There are also test kits that detect antigens of P. falciparum in the patient’s blood. These immunologic tests are known as rapid diagnostic tests (RDTs). Most malaria deaths occur in rural areas. Quick progression from illness to death can be prevented by fast and effective medication.

  8. Christa Gurriera

    Balantidium coli is a protozoan parasite in humans and causes a disease called balantidiasis. It is a parasitic species of ciliate protozoan and is the only member of ciliate phylum known to be pathogenic to humans. This disease occurs when someone eats food or water that is contaminated. The cysts can travel through the stomach and trophozoites form in the small intestine. They multiply by binary fission in the intestinal wall. The cysts can be formed either in the large intestine or outside the body. Symptoms include diarrhea containing blood, weight loss, and an inflammatory disorder of the intestine. This is diagnosed by finding trophozoites from a stool sample. This is treated with the antibiotic tetracycline, with guidance from your doctor. Prevention includes proper hygiene techniques.

    • People in today’s lab seemed very surprised at the method of diagnosis of all of these diseases of the gastrointestinal tract. All of the protozoan diseases in this lab’s slide box are GI-acquired and the method of diagnosis is a fecal smear!

  9. Enterobius vermicularis causes pin worm. This is very common in school aged children in America. This causes extreme itching in the anal region. It is spread by children itching the affected area and then touching things like other people and bedding. The eggs then get into another child and hatch in their intestines. The eggs mature in the colon and lay their eggs in the anal region at night time. The scotch tape method we used in lab on the molds a long time ago is used to diagnose this in children. They take a piece of tape and put it near the anus right after the child wakes up before bathing or going to the bathroom and then look for eggs.This disease is fully treatable by taking mebendazole or albendazole. They will often treat more than one family member and encourage the parents to keep the child’s bedding, and toilets very clean.


  10. Encephalitozoon cuniculi is a eukaryotic organism that can infect humans. In earlier times it was thought to be the cause of rabies and polio. Encephalitozoon cuniculi can be transmitted in body exudates or transplacentally. Effects are often minimal, but in the case of infection, can be fatal, especially in immunocompromised individuals. Symptoms of E. cuniculi are compared to be like those of a severe hangover. E. cuniculi antibodies can be detected through a titer test.

    • E. cuniculi is not actually a protozoan parasite, but a fungus, like the yeasts and molds we saw in this week’s lab. Due to their obligate intracellular lifestyle, they were originally classified with Protista, but have since been reclassified on the basis of genetic similarity to the Fungi.

  11. Chagas disesase is a protozoan disease of humans caused by Trypansoma cruzi. This infection is spread by insect vectors, blood transfusions, contaminated food and by mother to fetus. Signs and symptoms of Chagas disease include fever, fatigue, aches, diarrhea, vomiting, rash, and headache. It can be detected by microscopically examining a patients blood. Treatment for Chagas disease is antiparasitic treatment.

  12. Cryptosporidiosis, is a parasitic disease caused by Cryptosporidium. It affects the intestines and is typically an acute short term infection. It is spread through a fecal oral route, commonly through contaminated water. Symptoms include diarrhea in those with intact immune systems, those with immunocompromised systems, their symptoms are particularly severe and often fatal. Treatment is symptomatic, with fluid rehydration, electrolyte correction and management of any pain.

  13. Erica Stackhouse

    Isosporiasis is an uncommon diarrheal illness caused by the protozoan Isospora belli, from the subclass Coccidia. This disease is most commonly found in tropical and subtropical climates. This disease causes the worst symptoms in those who are immunocompromised, and is an AIDs-defining illness. The I belli is ingested in contaminated food or water, as well as ingestion of feces. Normally, symptoms include those of irritable bowel syndrome, and inflammatory bowel disease, such as extreme diarrhea in infants and children. This disease usually subsides within 2 to 3 days if treated, but if not a person may be infected for a long time, especially patients with AIDs who are diagnosed with it.

  14. Ashley Chenoweth

    Naegleria fowleri is also known as the “Brain eating ameba”. This protozoan lives in the warm water such as lakes and rivers and enters the body through the nose where it travels to the brain and causes PAM, or Primary Ambeic Meningoensephilitis which is fatal. People can also get infected with PAM from unchlorinated swimming pools. After infection of this protozoan, Naegleria fowleri moves from the cribiform plate to the olfactory bulbs of the brain where it begins to multiply.About 5-7 days later, patients begin to experience symptoms such as parosmia and anosmia due to the multiplication of the microorganism. Other symptoms include headache, nausea, vommiting, dileria an seizures as the infection progresses. About to weeks after exposure the patient dies of resperatory failure when the infection spreads to the spinal chord and stops the autonomic nerve cells from functioning. This is a fast acting infectinn, but is very rare.

  15. Trichomonas vaginalis is a protozoan that commonly causes vaginitis, or inflammation of the vagina. This happens through intercourse which causes the spread of this protozoa. This condition can be very painful to the person dealing with it, as it can cause them to experience vaginal itching, pains during intercourse, as well as urination, and possibly even vaginal discharge. This is also considered a sexually transmitted infection, which of course is passed along through sexual intercourse, however it is not able to be transmitted to a baby from the pregnant mother.

  16. Balamuthia mandrillaris is a protozoan that is morphologically similar to Acanthamoeba. This protozoan is often the cause of Granulomatous amoebic encephalitis (GAE), which is a serious brain infection. THis can be presented as headahces, sensitivity to light, nausea, vomiting, lethargy, or a low-grade fever. More extreme symptons would be behavioral changes, seizures, weight loss, partial paralysis, speech difficulties, or difficulties walking. This protozoan can be contracted by getting through skin wounds or cuts, or even breathing in dust that contains Balamuthia. This disease is rare, but when it is contracted is usually fatal.

  17. Cyclosporiasis is caused by the protozoan Cyclospora cayetanensis. It is an intestinal illiness. It causes watery, explosive diarrhea. A person can contract this by ingesting contaminated food, usually freash produce, or water.

  18. I also teach Micro to Allied Health students. I am very impressed with your website and students participation! Thank you
    LuAnn Hammersland

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