Everything you always wanted to know about toxoplasmosis

Toxoplasma, scientifically called Toxoplasma gondii, is a microscopic protozoan parasite. It is estimated that approximately one third of the population of the Czech Republic is infected with it. In Germany, the estimates are by 5–10% higher because there’s more raw meat in German cuisine and the numbers are even bigger for France. Once you become infected with toxoplasma, it’s for the rest of our life. The good news is that the parasite can’t really cause much harm to individuals with a fully functional immune system. All it does is slowly procreate in some of its host’s cells, which it rearranges into the so‑called tissue cysts for that purpose. Toxoplasma can reproduce sexually only in the gut of a cat. Through faeces, its oocysts are released to the soil, where they remain infectious for several months or even years. Any warm‑bloodied animal, including humans, can become infected with oocysts. Cats become infected by catching and eating an already infected animal.

Toxoplasmosis is a disease caused by a protozoan parasite known as toxoplasma. There are various forms of toxoplasmosis. Acute toxoplasmosis breaks out 1–3 weeks after the infection and its course tends to be asymptomatic. Its symptoms may sometimes resemble common viral diseases. Many patients experience swollen lymph nodes on their neck and under their jaw. In people with severe immunodeficiency, such as AIDS patients or those with organ transplants, an old latent infection may reactivate and take on a fatal brain form of the disease /it is more often the result of the reactivation of latent toxoplasmosis rather than of acute/recent infection/. In other people, acute infection subsides spontaneously in a matter of months and the disease changes into its most common form, the so called latent toxoplasmosis. Patients with latent toxoplasmosis have IgG toxoplasma antibodies in their blood (which is why they can’t become infected again) and dormant parasites in organs like brain, muscles or testicles. The most dangerous form of toxoplasmosis is called congenial toxoplasmosis. It occurs when a woman becomes infected during her pregnancy (which doesn’t happen very often) and the infection is transmitted through the placenta to the developing foetus. In the first trimester, the chances of transmission from a recently infected mother to her baby are approximately 15%, but the consequences can be grave (miscarriage, the child may be born with a serious developmental disability, including hydrocephalus or microcephaly). If the mother becomes infected in the third trimester, the risk of mother‑to‑child transmission is of up to 70%, but the consequences tend to be less serious and mostly functional, such as retinitis. The probability of transmitting the infection to the foetus as well as subsequent damage to the child can be reduced by administering medicine against acute toxoplasmosis both the pregnant mother and her new‑born child. Finally, the last form of toxoplasmosis is ocular toxoplasmosis with retinal damage mostly, but not exclusively, in consequence of congenial infection. The infection may cause repeated inflammation of the retina, leading to the loss of sight in the affected eye.

In the Czech Republic, the currently most common sources of infection are gloveless gardening and the consumption of raw, insufficiently washed vegetables (carrot, radishes). Oocysts may also be contained in the soil that your cat or dog brings to your house on their paws and in their fur. In many countries, the consumption of raw or semi‑raw meat is an important source of infection. However, this is not true for the Czech Republic because the infected meat doesn’t usually come from industrial production. It is often domestic production meat or game that contains the parasite, in which case you can become infected simply by manipulating with the meat or from vegetables cut on a cutting board that had previously been used for the meat. You can eliminate tissue cysts in any meat by heating it for 10 minutes at a minimum temperature of 65°C or by freezing the meat for a few days at a temperature of at least -18°C and possibly even by long‑term freezing at slightly above‑zero temperatures. Toxoplasma can also be transmitted through infected organ transplants. There are also many countries where poorly treated drinking water or unpasteurized goats’ or sheep’s milk is a significant source of infection. Some data suggest that toxoplasma may also be transmitted during unprotected sexual intercourse, which is why it is advisable to avoid this form of sex during pregnancy.

That’s not very likely. Cats can become infected only when they hunt outside or when you feed them raw meat. Moreover, they become infected only once in a lifetime, usually as kittens. The infected animal then excretes cysts for only about 10 days and those would have to ripe in the open air for more than a day to become infectious at all. People who regularly clean after their cats have practically nothing to worry about. That said, it is still not advisable to let your cat jump on your dining table. Pregnant women should also take the precaution of avoiding manipulation with cat excrement and minimise all intimate contact with their cat. Some data suggest that even cat bites and scratches can be a source of infection, which is why pregnant women should avoid activities that may lead to such injuries.

While it is possible to treat acute toxoplasmosis, its latent form, which may either be the result of a spontaneous change of the disease or of acute toxoplasmosis treatment, cannot be cured. In most cases, acute toxoplasmosis subsides before it is ever diagnosed. In some cases, toxoplasmosis treatment is absolutely necessary, like for immunocompromised people, such as patients who have undergone organ transplantation and take immunosuppressive drugs. Similarly, women, who became infected during pregnancy or shortly before getting pregnant, need to be treated. Toxoplasmosis can’t be treated with regular antibiotics against bacteria nor with antiviral drugs. Instead, specialised medicines are used (spiramycin, if necessary and only from the 16–18th week of pregnancy, combination of sulfadiazine and pyrimethamine accompanied by folinic acid, or clindamycin with pyrimethamine).

There is currently no vaccine usable for humans and the development of a vaccine for cats is only at its start. So up to this day (2016) there’s no vaccine against toxoplasmosis.

If you are a woman and you plan on having children in the future, then definitely yes. Knowing that you’re already infected and have toxoplasma antibodies in your blood means that you don’t have to worry about becoming infected during pregnancy and about your baby consequently developing congenial toxoplasmosis. The results of a pre‑pregnancy test on toxoplasmosis help your doctor to better decide on the right treatment for you as opposed to if they found out about the antibodies in your system only during the pregnancy. That’s because sometimes it’s hard to tell whether the mother‑to‑be had been infected before the pregnancy or whether the infection is recent and can endanger her baby. In such cases, the test should be repeated after an interval of a few weeks. That said, in the case of a newly acquired infection, it is imperative that you start the treatment immediately. If your pre‑pregnancy test results were negative, you should avoid all potential sources of infection during pregnancy and request toxoplasmosis test if you notice any suspicious symptoms (swollen glands on the neck or under the jaw). It is advisable, and in some countries even compulsory, that uninfected women repeat the blood tests several times during their pregnancy. For male patients, knowing whether they’re infected isn’t that important. But it can help them decide how strictly they should avoid potential infection sources.

Long‑term (lifelong) toxoplasma infection, the so called latent toxoplasmosis, isn’t dangerous even during pregnancy. Only a recent infection, acquired during the pregnancy or shortly before it, is. In such case, there’s a risk that the infection may transmit to the developing foetus and cause it serious damage. In the first trimester, the chances of transmission from a recently infected mother to the foetus are approximately 15%, but the consequences can be grave (miscarriage, the child may be born with a serious developmental disability, including hydrocephalus or microcephaly). If the mother becomes infected in the third trimester, the risk of mother‑to‑child transmission is of up to 70%, but the consequences tend to be less serious, such as retinitis. The likelihood of mother‑to‑child transmission of toxoplasmosis can be reduced by administration of medicine against acute toxoplasmosis (but not with regular antibiotics).

Definitely not. A cat that doesn’t leave the house, doesn’t hunt and isn’t fed raw meat will probably never become infected and poses no threat to a pregnant woman. It is very hard to become infected from your cat. Cats become infected only once in a lifetime and even then excrete cysts in their faeces for only about 10 days. A cat that doesn’t leave the house, doesn’t hunt and isn’t fed raw meat will likely never become infected. That said, it is best for pregnant women to avoid manipulation with cat faeces, garden soil, raw meat and to forbid her cat from jumping on the dining table or kitchen worktop. The floor should be mopped more often in houses with dogs and cats.

If you’ve been infected for more than a year and haven’t noticed any suspicious symptoms (swollen glands on the neck or under the jaw, faintness or recurring headaches) and you’re not heavily immunosuppressed, you almost certainly have the latent form of toxoplasmosis and can safely get pregnant. You actually have an advantage over uninfected women because there’s no risk of you becoming infected during your pregnancy and transmitting the parasite to your baby. If you’ve been recently diagnosed with acute toxoplasmosis (e.g. based on high levels of IgM and IgA antibodies) or have a well‑founded suspicion that you’re suffering from acute toxoplasmosis, consult your doctor and preferably also an infectious disease specialist before trying to conceive.

Definitely not. You most likely have the latent form of toxoplasmosis, meaning that you must have become infected some time ago, probably already in childhood, and the disease poses no threat to your baby. If test results confirm that the infection happened only after you got pregnant, in other words, that your antibody levels, including IgM or IgA antibodies, are extremely high, it is imperative that your doctor institute preventive treatment and monitor the development of the foetus closely. Abortion should be considered only if your doctor confirms that the infection has been transmitted to the foetus.

It may and may not be the case. To determine the exact phase of your disease, you need to know the results of all the laboratory markers (IgG, IgA, CFT/IIFR, IgG avidity, …) and it’s often necessary to have your blood taken repeatedly. The blood test results must always be interpreted by a professional—an infectious disease specialist or a diagnostician—experienced in the field. The results of your repeated blood tests allow them for example to determine whether antibody levels in your blood are rising or falling over time. To those residing in the Czech Republic, we recommend that they contact doctor Markéta Geleneky from the Infectious diseases clinic of the Prague hospital Na Bulovce or doctor Petr Kodym from the National Reference Laboratory for Toxoplasmosis in Prague.

Stay calm, not yet. Your doctor must first confirm that you really became infected only during your pregnancy, which tends to be unclear after the first test. Moreover, even if you did become infected only after getting pregnant, the chances of mother‑to‑child transmission with consequent damage to the foetus are relatively low. It the first trimester, the probability is only about 15%. Despite the risk being much higher during the third semester, some 70%, toxoplasma cannot cause developmental disabilities at this stage. Toxoplasmosis alone or the sole presence of antibodies in your blood are no reason for abortion. Only some developmental disabilities are.

Even when your baby becomes infected, it doesn’t have to mean that it will have serious developmental disabilities, especially if the transmission happened during the initial phases of your pregnancy. Toxoplasmosis alone is no reason for abortion, only some developmental disabilities are.

That depends on the type of damage to the foetus and, besides other things, on your family situation. In this respect, it is wise to heed the advice of specialists.

Toxoplasmosis test is a blood test that can be carried out in most diagnostic microbiology or parasitology laboratories. The test can be ordered by any GP, gynaecologist or infectious disease specialist, but they’re usually reluctant to do that based solely on the patient’s wish, when there’s no particular reason for the test. Such reasons include for example clinical symptoms of toxoplasmosis like swollen glands on the neck or under the jaw accompanied by symptoms similar to those of flu (especially during pregnancy). If it’s your doctor who orders the test, the costs will be covered by your health insurance company. In the Czech Republic, the diagnostic laboratory may charge more than 1,000 CZK per test depending on its price tariff. Private laboratories tend to ask private patients to pay at least half that price. The Prague laboratory led by professor Flegr, who works at the Faculty of Science of Charles University, organises free toxoplasmosis testing several times a year. It is intended primarily for the followers of the Pokusní králíci (meaning “guinea pigs”) website (pokusnikralici.cz). If you’re interested in getting yourself tested on toxoplasmosis, we can carry out the test after you’ve delivered a sample of your blood serum to our laboratory.
The vast majority of results are serologically negative or show low levels of toxoplasma antibodies, characteristic for latent form of toxoplasmosis. If the results of this “research” test fail to exclude for instance acute phase of toxoplasmosis, they must be confirmed by a thorough non‑anonymous “diagnostic” testing carried out by a specialized laboratory before drawing any conclusions. An infectious disease specialist then makes a diagnosis based on your results and clinical symptoms.

Most likely it does. You should try to keep it that way. However, there’s a small percentage of cases (about 5–9%) where the results aren’t clear enough. Moreover, in older people, toxoplasma antibody levels may be so low as to cause false‑negative results. Sometimes, a repeated blood taking and a new test may help, but more often the results remain unclear even after that. The interpretation of results should always be handled by specialists, such as those from the National Reference Laboratory for Toxoplasmosis of the National Institute of Public Health in Prague.

There’s a 99% chance that you have the latent form of toxoplasmosis, meaning that you have a dormant parasite in your body and low or medium IgG antibody levels in your blood. It is not necessary nor possible to treat latent toxoplasmosis. If your antibody levels are suspiciously high, and especially if they include IgM and IgA antibodies, you may be suffering from acute toxoplasmosis, in which case high‑risk patients (weakened immune system function, organ damage, pregnancy) should be treated. Needless to say, only a specialist can determine whether you really do suffer from acute toxoplasmosis and should start with a treatment or not. Pregnant women who have been diagnosed with acute toxoplasmosis (e.g. during a check-up test) should definitely be treated. Keep in mind that toxoplasmosis can’t be treated with regular antibiotics against bacteria nor antiviral drugs. Instead, specialised medicines are used (spiramycin if necessary and only from the 16‑18th week of pregnancy, combination of sulfadiazine and pyrimethamine accompanied by folinic acid, or clindamycin with pyrimethamine).

Yes. Toxoplasmosis increases your reaction time (infected people simply react slower), raising your chances of having an accident. That applies both to infected drivers and pedestrians. Infected people, especially those with a Rh‑negative blood type, should take special care when driving and may want to avoid working as professional drivers and air‑traffic controllers. The longer you’re infected, the slower your reactions get, but at the same time the likelihood of you having an accident decreases (you gradually get used to your increased reaction time).

Yes. Toxoplasmosis increases the possibility of you having schizophrenia, bipolar disorder and obsessive‑compulsive disorder. On the other hand, it also decreases the risk of unipolar depression and phobia. In any case, toxoplasma alone can’t trigger psychiatric diseases. Apart from being infected, you’d also have to be genetically predisposed to the disease. In the Czech Republic, the risk of a healthy person having schizophrenia is less than 1% and in people infected with toxoplasma, it is about 2.6 times higher. However, the numbers are approximately two times higher for bipolar disorder and at least three times higher for obsessive‑compulsive disorder. If you’re infected with toxoplasma and you get the impression that you can read other people’s minds, that they can read yours or even manipulate your thoughts, you have most probably developed a mental illness and should seek prompt medical attention. It is important that you do that immediately, while toxoplasma still hasn’t taken over your brain and you’re able to make your own decisions. The above said applies even if you’re not infected by toxoplasma. Remember that mental illnesses don’t distinguish between infected and uninfected people and can strike anyone.

Yes, it does. People infected with toxoplasma tend to be less tidy, reliable and don’t seek new stimuli that much. While infected women are friendlier and more sociable, infected men tend to be less sociable and more introverted. Infected men are distrustful, infected women, on the other hand, more trusting. Infected men don’t like following rules and social norms, infected women have a contrary tendency. With time, most of these behavioural changes intensify. But it should also be emphasised that the changes brought about by toxoplasmosis are small rather than significant. Either way, it is impossible to tell whether a person is infected based on their personality traits. That said, if there were two groups of 30 infected and 30 uninfected people and you asked them to complete a psychological questionnaire, you’d most probably be able to tell which group is which based on the results.

Research has shown that women with latent toxoplasmosis and high antibody levels, meaning those that most likely became infected in the two‑year period before getting pregnant, are twice as likely to give birth to a boy. By contrast, women with low antibody levels, meaning those who have been infected for a long time, are more likely to give birth to a girl. That said, a baby’s sex is influenced by many different factors, so it can’t really be said that women with latent toxoplasmosis tend to have boys.

The likelihood of becoming infected is the same in people with Rh‑positive and Rh‑negative blood type. The difference is that Rh‑negative individuals are much more susceptible to the effects of toxoplasmosis. To give an example, their reaction time increases almost immediately after infection and the difference is much bigger than in people that are Rh‑positive. That also means that Rh‑negative individuals are more likely to have an accident after becoming infected.

You can read more on the topic in Jaroslav Flegr’s book called Watch out for Toxo!: The Secret Guide to Practical Science. You can also find more information on www.toxoplasmoza.cz, the website of MUDr. Markéta Geleneky, who is the leading Czech specialist on congenial toxoplasmosis.

This website was created and is administered by a team of specialists led by professor RNDr. Jaroslav Flegr’s, CSc. of the Faculty of Science of Charles University. Our team has more than a quarter‑century of experience in the field of toxoplasmosis research. Yet, we’re biologist, not doctors. That’s why we would like to give our thanks to MUDr. Markéta Geleneky, RNDr. MUDr. František Stejskal, Ph.D. and RNDr. Petr Kodym, CSc., who have helped us with questions concerning the diagnosis and treatment of toxoplasmosis. The purpose of this website is to provide the public with objective information about the health risks associated with the infection caused by one of the most common parasites in the developed countries, a protozoan parasite called toxoplasma. Our aim is to disprove the inaccurate or downright distorting information spread about toxoplasma and toxoplasmosis in the press and on the internet. The basic information that you should remember after visiting this website is that the best scenario is to avoid becoming infected with toxoplasma in the first place. But, in case you do, there’s no reason to panic because, among other thing, about a third of the population of some developed countries, like the Czech Republic, is already infected. You should also keep in mind that in some countries, e.g. in the Czech Republic, the most common sources of infection do not include contact with cats but unwashed root vegetables and garden soil. It’s also worth remembering that becoming infected during pregnancy doesn’t usually lead to damage to the foetus. In other words, infection alone is no reason for abortion.