There are many different types of parasites, but they can be broadly classified into three main groups:

* **Protozoa:** These are single-celled organisms that can live in or on other organisms. Some protozoa, such as Giardia lamblia, can cause serious infections in humans.
* **Helminths:** These are multicellular organisms that can grow to be quite large. Some helminths, such as tapeworms and roundworms, can live in the human digestive tract for years.
* **Ectoparasites:** These are parasites that live on the outside of the host organism. Some ectoparasites, such as lice and ticks, can transmit diseases to humans.

Parasites can be transmitted in a number of ways, including:

* **Consuming contaminated food or water:** This is a common way to get protozoan and helminth infections.
* **Contact with contaminated soil or water:** This can also lead to protozoan and helminth infections.
* **Bites from infected insects:** This is a common way to get ectoparasite infections.
* **Sexual contact:** This can transmit some protozoan infections, such as Trichomoniasis.

Parasitic infections can cause a wide range of symptoms, depending on the type of parasite and the location of the infection. Some common symptoms include:

* **Diarrhea:** This is a common symptom of protozoan and helminth infections.
* **Abdominal pain:** This is another common symptom of protozoan and helminth infections.
* **Weight loss:** This can be a sign of a serious parasitic infection.
* **Fever:** This can be a sign of a serious parasitic infection.
* **Skin rash:** This can be a sign of an ectoparasite infection.

If you think you may have a parasitic infection, it is important to see a doctor for diagnosis and treatment. Treatment for parasitic infections varies depending on the type of parasite and the severity of the infection. However, most parasitic infections can be treated with medication.

Here are some tips to help prevent parasitic infections:

* **Wash your hands frequently with soap and water.**
* **Cook food thoroughly.**
* **Filter your water.**
* **Avoid contact with contaminated soil or water.**
* **Wear protective clothing when hiking or camping.**
* **Use insect repellent.**
* **Get tested for parasitic infections if you have traveled to a developing country.**