Introduction

Parasitic infections are a major public health problem, with billions of people affected, resulting in the death of millions. Such infections may initially present mild symptoms in individuals but have the potential to escalate into severe or life-threatening conditions. Since the old times, before sciences were as involved as they are now, humans turned to nature for survival help. Therefore there has always been a modern vs traditional medicine "debate". 

The use of modern medicine alone has shown to not be adequate at times as an infection can easily come from the environment, water, and food. Moreover, with indiscriminate drug consumption, the resistance of parasites to existing drugs has increased. Consequently, traditional medicine, mostly medicinal plants, has been the protagonist in recent research as an alternative for treatment for parasitic infections. 

In this article, we will dive deeper into the understanding of parasites, their types, symptoms, risks, prevention, and treatment for such infections while focusing on natural antiparasitic remedies.

Understanding Parasites

Parasites are organisms that depend on another organism to survive and can affect all living organisms like humans, mammals, and even plants. They need to live on, in, or with another organism known as their "host". They utilise the resources of the host to sustain their functions of growing and multiplying. Therefore they rarely kill their host but can have life-threatening effects on his health. Parasites can be found anywhere in the environment like soil, water, food, blood, feces, and other living organisms.

Parasitic infection

While not all parasites are harmful to the host's body, some can directly cause disease to the host. A parasitic disease, otherwise called parasitosis, is an infectious disease caused or transmitted by the parasite to the host. 

How parasites enter the body of the host

Parasites can enter the body of the host through the skin, an open wound, insect bites, food, water, person-to-person contact, sexual contact, and rarely even through blood transfusions. 

Types of parasites

The three main types of parasites that can cause disease in humans are:

• Protozoa

Protozoans are one-celled organisms, so small that you can only see them with a microscope. Some species are free-living, meaning not parasitic. Protozoans are found in most habitats, mainly bodies of water and soil, with higher animals usually infected with one or more species. They feed and multiply in the human body. Their nutrition requires organic materials, as partticleor in solution. Parasites that destroy cells while feeding can lead to organ dysfunction and serious or life-threatening consequences.

To move, protozoans use pseudopods (false feet), cilia (hairlike structures), and flagella (whip-like structures), while some species with no locomotory structure are known to simply "glide" or not move. 

Protozoans can inhabit our intestines, tissues, and blood. Such organisms usually get transmitted by close person-to-person contact, insects that act as carriers, and through consumed contaminated bodies like water or food. 

A well-known highly infectious genus of protozoa is Plasmodium, which causes malaria. Malaria, for instance, is a mosquito-borne parasitic disease that if left untreated, can cause severe complications and eventually lead to the death of the host. 

• Helminths

Helminths are multicellular parasitic worms, varying from flatworms to tapeworms and roundworms, that usually reside in our gastrointestinal (GI) tract. In their adult stage, they are visible to the naked eye. Similar to protozoans, they can be free-living or parasitic. In contrast to protozoans, helminths can not multiply inside the human body. These parasites feed on the blood and the tissues of the host, often causing iron and protein loss. 

Flatworms, known as flukes (trematodes), are flat and leaf-shaped and can reside in our blood, lungs, bile duct, intestines, urinary bladder, liver, and gallbladder. They usually spread through infected water or aquatic animals.

Tapeworms (cestodes) are flat and elongated and live in the intestines. They reproduce by spreading their eggs in their host, which results in the infected feces of the host. The eggs can then be spread through contaminated water or food, undercooked meat, and through person-to-person contact due to contaminated hands. 

Roundworms (nematodes) are cylindrical, inhabiting the intestines as well as the GI tract, blood, lymphatic system, and tissues. They are found in almost all environments, mainly soil but also marine and freshwater habitats. They can be spread through infected feces and any physical means that can move soil particles, person-to-person contact, contaminated food, and arthropod vectors. 

• Ectoparasites

Ectoparasites are generally blood-sucking arthropods like fleas, ticks, lice, and mites, that live on the outside of their host. They serve as either as vectors carrying diseases through the blood but causing disease on their own. These organisms usually bite the host and attach to the skin, staying there for long periods of time. Depending on the type of ectoparasite, they can lay eggs on or off their host, after they have fed. Ectoparasitic infestations can cause vivid discomfort and itchiness. 

Fleas can jump onto their host and even get swallowed by them. However head and body lice can travel from person to person duringsexual contact or sharing personal things like bedsheets, hairbrushes, and towels. Moreover, ticks, fleas, and mites are mostly found in wooded, grassy, and leafy areas.

Symptoms

The infections parasites cause can range from no symptoms ormild to life-threatening, which highly depends both on the species and strain of the parasite, but also the resistance the host presents. Common symptoms and health risks associated with parasitic infections include: 

• Nausea and vomiting
• Loss or increase in appetite
• Diarrhea
• Bloody or mucus feces
• Body aches or cramps
• Muscle pain
• Abdominal pain
• Gas and bloating
• Digestion problems
• Weight loss
• Fever
• Chills
• Weakness 
• Sleeping problems
• Skin rashes and itching
• Fatigue
• Discomfort
• Organ failure
• Death

Risks and prevention

Although parasitic infections are prevalent among people, there are ways to minimise the risks of such occurrences. Significant risk factors for an event of parasitosis include: 

• Visiting areas that are known to accommodate or favor such organisms
• International traveling (e.g. traveler's diarrhea) 
• Poor hygiene and sanitation (food and water)
• A weakened immune system (e.g. HIV, AIDS)
• Bug bites
• Sexual contact
• Contaminated food, water, blood and feces 

Below are some suggestions on how to be protected against the odds of a parasitic infection and minimize its chances of occurrence:

• Ensure food hygiene - buy food from a reliable source, choose safe eating places, cook your food well, and avoid eating raw food
• Ensure personal hygiene - wash hands before consuming food, regularly bath or shower
• Take care of pets - clean them, provide anti-parasitic treatments
• Drink clean or filtered water, try bottled water or if not accessible, try boiling the water at your disposal 
• Wash your personal items like clothing, bedding, clothing, and accessories 
• Check for insects once you return home - vacuum carpets, mattresses, etc. 
• Use bug spray
• Practice safe sexual contact
• Avoid walking barefoot outside in mud or rainforest areas
• Avoid swimming in luckily contaminated bodies of water
• If you are known to have a weak immune system be extra careful

Testing methods

If a parasitic infection is suspected, numerous testing methods can be performed, according to the symptoms, and medical and travel history, such as:

• Physical examination: A healthcare provider will check your body for skin conditions like rashes, and itching and look for bite marks.
• Fecal (stool) examination: Focusing on parasites affecting your intestines, stools are examined under a microscope. The process follows the collection of stools, usually on different days, which will then be carefully checked for eggs (ova) or parasites (O&P test) present. 
• Enteroscopy/colonoscopy: When an O&P test can not determine the kind of parasite present, then an enteroscopy or colonoscopy examination should be performed. A gastroenterologist, a specialist in digestive system conditions, will use a tube with a camera attached to its end, called an endoscope, to look in the respective intestine. In the case of colonoscopy, the endoscope passes through the anus to the large intestine while during an enteroscopy, the tube enters through the mouth to the small intestine. Such a test will look for a parasite or other parasite-related abnormalities present, causing parasitosis symptoms. 
• Blood tests: By using a tiny needle, a small amount of blood will be taken to conduct either a blood smear or a serology test. The former is the examination of the blood drop under a microscope, for parasites present in blood, while the latter looks for antibodies or antigens produced in response to the presence of a parasite in our blood. 
• Imaging tests: If lesions have been created on any organs, an X-ray, magnetic resonance imaging (MRI), or computerised axial tomography (CAT) scan can be performed to examine if there are parasitic diseases present. 

Treatment of parasitic infections

The treatment for a parasitic infection depends on the type of parasite responsible for it, and it can be:

• Antibiotics
• Antiparasitic medicine (orally, intravenously, topically)
• Antiparasitic shampoos, lotions, creams

Besides the use of modern medicine, numerous natural remedies can be employed to aid in treating a parasitic infection or strengthening the immune system, some of which will be explored below. 

Effective natural antiparasitic remedies

Medicinal plants have always been explored as a constant source of natural disease treatments. Certain plants provide a rich source of botanical anthelmintics, drugs used to fight parasitic infections usually caused by worms in humans and animals. Therefore, herbal treatments, dietary adjustments, and essential oils can help fight parasites growing in our GI tract. Some examples, based on scientific research, are mentioned below.

Herbal treatments

Garlic: Garlic (scientifically, Allium sativum) is known to have antiparasitic abilities, as displayed by many studies against parasitic worms like Lernanthropus kroyeri, a gill parasite found on the cultured European sea bass,¹ protozoans Trypanosoma b. brucei and Leishmania tarentolae,² and other gastrointestinal parasites.³ In the second study mentioned, onion (Allium cepa) also displayed anti-parasitic activities.² 

Wormwood: A study examining wormwood's antiparasitic abilities, concluded it to be efficient against Hymenolepis nana, a common tapeworm infecting humans, and even comparable to an anthelmintic drug called praziquantel.⁴

Ginger: Recently, a study focusing on the potential anti-parasitic effects of ginger (Zingiber officinale) against protozoan Toxoplasma gondii showcased its efficacy as a therapeutic agent in the fight against toxoplasmosis, a chronic parasitosis, usually acquired by eating undercooked meat.⁵ Moreover, another study investigated the anti-parasitic mechanism of ginger against Ichthyophthirius multifiliis, a protozoan found in the fish species grass carp, and found it to be satisfactorily effective.⁶

Other herbs that have been classed as successful as potential anti-parasitic therapeutic agents are: aashwagandha, coriander, cinnamon, oregano, thyme, and more. 

Dietary adjustments

Probiotics & vitamins

The use of probiotics and prebiotics has been suggested when dealing with a parasitic infection. Probiotics are known to have immunomodulatory mechanisms and help maintain a healthy microorganism community. Many studies have focused on the relationship between the popular probiotic Lactobacillus bacteria strains and parasites. In one study Lactobacillus inhibited the proliferation of Giardia parasites,⁷ while in another the probiotic minimized or prevented the adherence of the same parasite to the mucosal surface.⁸ Several tracts and structures in our body are lined by mucosal membranes including the mouth, nose, eyelids, intestines, and more.

However, the impact of probiotics on parasites highly depends on the parasitic species, their stage and localisation, and also the administration scheme.

Another suggestion is to also take vitamin supplements, like vitamins A, C, selenium, and zinc, to boost the immune system and its resistance to invading parasites and the infections they can cause. 

Anti-parasitic foods 

Papaya: Papaya (Carica Papaya) seeds have been proven to cause a significant reduction in gastrointestinal infections. A study exploring a human parasitic infection caused by A. lumbricoides, one of the most prevalent intestinal helminths (a nematode), showed that papaya seeds cleared the infection.⁹ In the same study, researchers also discovered the antiparasitic abilities of honey, which since then have been backed up by additional research.

Pumpkin: Another proven anthelmintic food is pumpkin (Cucurbita pepo) seeds. A study investigating the action of pumpkin seed extract against two types of nematodes presented a significant reduction in worm burden.¹⁰ In addition, a study testing the effects of pumpkin seeds against a nematode Trichinella spiralis, highlighted pumpkin seeds as a promising alternative herbal drug, with a higher efficacy in combination with honey.¹¹

Other anthelmintic foods include asparagus, pomegranate, barberry, and more. 

Essential oils

Oregano oil: A research study testing Oregano (Origanum vulgare) against Echinococcus granulosus, a parasitic worm causing cystic echinococcosis (CE), also known as hydatid disease, along with thyme (Thymus vulgaris) suggested their anthelmintic properties.¹² In another study, oregano extract was investigated against Giardia lamblia, a protozoan known to cause giardiasis, anti-Giardia activity was observed, even suggesting oregano essential oil as an alternative for metronidazole, a commonly used antibiotic for such an infection.¹³

Other herbal essential oils with documented anti-parasitic activity are rosemary, cumin, dill, ginger, tea tree oil, and more. 

Summary

Parasitic infections remain a significant global health concern with modern medicine administration facing challenges like drug resistance. This phenomenon has led to a notable growing interest in natural remedies, with medicinal plants being the main focus, for treating parasitic infections. 

From protozoa to helminths and ectoparasites, this article explored the diverse types of parasites, their way of transmission, and their impact on human health. Diagnosis through various testing methods and preventive measures, including hygiene practices and dietary adjustments, have been highlighted.

Treatment options range from conventional medications to natural remedies like garlic, wormwood, and oregano oil, supported by scientific research. Their benefits include gentle relief with minimal side effects, sustainable and eco-friendly alternatives to conventional medications, cost-effectiveness compared to pharmaceutical treatments, and easy accessibility, seamlessly fitting into daily routines. 

Overall, the article emphasises the importance of holistic approaches in combating parasitic infections and underscores the potential of natural remedies as complementary or alternative treatments in modern healthcare practices. Lastly, please always consult a healthcare professional about health matters and do not rely solely on online sources.