Parasites are organisms that need other organisms to survive. In many cases, parasites feed off their host organisms. In some cases, a parasite does not cause any noticeable harm to its host. In others, however, the parasite reproduces, grows or invades the host’s organ systems, leading to sickness and eventual parasitic infection.
Malaria is the deadliest parasitic infection in the world, occurring mostly in tropical and subtropical regions of the globe. A close second for the most devastating of parasitic infections is schistosomiasis. Approximately 90% of individuals who require treatment for schistosomiasis live in South African.
All parasitic infections stem from one of three types of organisms:
Protozoa are the most common causes of parasitic infections. These single-celled organisms live within your body and, while there, multiply. Protozoa can cause several types of infections, including giardiasis and malaria. Giardiasis is a serious infection that you can contract by drinking water that is contaminated with Giardia protozoa. Malaria is a serious, sometimes fatal, disease that is caused by the plasmodium parasite, which is often transmitted to humans through the bite of an infected mosquito.
Ectoparasites are multi-celled organisms that feed off your skin. Ectoparasites are so common that most people are unaware they are parasites. Among others, they include insects and arachnids, such as fleas, ticks, mosquitoes and mites.
Helminths are another multi-celled organism that can live within and without your body. These parasites are actually just worms and include tapeworms, roundworms, flatworms and thorny-headed worms. Helminths typically make their way into humans via contact with animals and contaminated food.
Understanding what causes parasitic diseases is not enough to prevent them. It is crucial to understand how they are transmitted so that you can protect yourself and your loved ones.
For parasitic diseases, there are five main means of transmission:
When animals transmit diseases to humans, including parasitic disease, health organizations consider the disease “zoonotic.” Some parasitic zoonotic diseases are very common and can easily pass from animal to human through simple contact. One of the easiest ways to prevent the spread of parasitic zoonotic diseases is through proper handwashing.
The symptoms of parasite-borne zoonotic diseases vary significantly. Depending on the parasite in question and the strength of the immune system of the infected person, a zoonotic infection can present in mild or no symptoms, or it can cause severe illness. Middle of the road symptoms for these types of infections include fever, muscle aches and diarrhea.
People can contract zoonotic infections in several ways. Some of the more common means of transmission are as follows:
Food is one of the most common means of transmission of both protozoa and helminths parasites. Of the dozens of foodborne parasites to which you may be exposed, some of the more common include Giardia, Cryptosporidium, Cyclospora and Entamoeba. It is also not uncommon for humans to get roundworms and tapeworms from the foods they eat.
Though it is true that many of these parasites can also be transmitted via soil, water, animal-to-human and human-to-human contact, in developing countries, food is often the culprit. Types of food of which to be wary include the following:
Some foods are contaminated by the people who handle them. Others, however, are contaminated by the water supply that feeds them and the soil in which they grow.
Symptoms of foodborne parasites varies greatly. For instance, protozoa often cause gastrointestinal symptoms, such as nausea, vomiting and diarrhea. Helminthic infections, on the other hand, tend to cause more alarming symptoms, including diarrhea, abdominal pain, muscle pain, weight loss, skin lesions, cough, malnutrition, neurological disorders and more. Though these symptoms can be worrisome, know that treatment is available for most foodborne parasitic infections.
Insects are the most common culprit for transmitting the world’s most common parasitic infection: malaria. When an insect, such as the mosquito, transmits a disease of any kind, it is considered a “vector,” and the disease which it spreads is considered a “vector-borne disease.”
As vectors, insects can serve one of two roles. The first is as a mechanical vector. In this role, the insect is not essential to the parasite’s lifecycle. Rather, it merely carries the organism from one place, or one host, to the next. In the second role, the insect is an obligatory host. What this means is that the insect must carry the organism within itself so the organism can undergo development before being transmitted. Malaria parasites require obligatory hosts.
Vector-borne transmission can occur in one of two ways. In the first, the parasite enters the human host through the insect’s saliva, which the insect mixes with human blood during feeding. This is how malaria is spread. In the second, the parasite lives in the insect’s feces, which it typically leaves on its host immediately after enjoying a blood meal. Once a vector transmits a parasite, the disease-causing organism will circulate in the host’s blood, damaging organs and other body parts as it does so.
Some parasites are bloodborne, meaning they live in an infected person’s bloodstream and can be transmitted through exposure by a healthy person to an infected person’s blood. Some common examples of bloodborne parasites include the African trypanosomiasis, Chagas disease, malaria, babesiosis, leishmaniasis and toxoplasmosis. Because many vector insects tend to feed on the blood of animals, it is not uncommon for most bloodborne parasites to spread from host-to-host via insect bites.
That said, blood transfusions also come with the risk of parasite transmission. If such a risk is a possibility, healthcare teams will consider several factors before allowing blood transmission to take place. The most important of those factors are as follows:
Point number three is particularly important, as some parasites spend all or most of their lives in the bloodstream, while others use it simply to pass through to other parts of the body. Yet others spend the early days of infection in the bloodstream but then disperse to other parts of the body as time wears on, thereby bringing down the parasite concentration levels within the blood.
Finally, parasites can live in both natural and manmade water sources. For this reason, you should never consume anything but treated water, and you should take great care to keep water from entering your nose, eyes or mouth when swimming.
On a global scale, contaminated water is a serious issue that often leads to severe illness, pain, disability and death. Types of parasites that cause water-related illnesses around the world include giardiasis, Guinea worm, schistosomiasis, amebiasis and cryptosporidiosis. Though swallowing contaminated water is a major issue, it is important to note that you do not have to drink the water to become infected. In some cases, you merely have to come into contact with it. For instance, schistosomiasis can easily spread when a person has contact with or swims in a freshwater lake contaminated by the parasite. If a person infected with Guinea worm swims in or has contact with a water source used for drinking, they can easily spread the worm into the water and perpetuate the cycle of contamination and infection.
As mentioned above, drinking water sources can also become contaminated by urine or fecal matter from infected animals or humans. If infected soil makes its way into a water supply, the risk of contamination goes up as well.
Unfortunately, it is impossible to reduce your risk of parasitic infection entirely, as the sources of transmission are many. This makes it impossible to anticipate when and from where transmission will occur. That said, you can reduce your risk by taking a few key steps:
If you think you have a parasitic infection, consult with your doctor right away. Your doctor can run the appropriate tests, make a diagnosis and, if necessary, recommend an appropriate treatment plan. In doing so, he or she can help you rid your body of the parasite and, in the process, stop the spread of infection to others.