*2.3.7 Parasitic worms*

Unlike the infectious agents discuss so far, parasitic worms also known as helminths are macro-parasites meaning they can be seen with the naked eye. They are highly differentiated multicellular organisms with complex life cycles. In some hosts (definitive hosts) they exhibit sexual reproduction and exhibit asexual reproduction in other hosts (intermediary host or vector). Helminths include the three groups of parasitic worms; nematodes or roundworms, trematodes or flukes, and cestodes or tapeworms. Nematodes are unsegmented worms with elongated rounded bodies pointed at both ends; mostly free-living but some are parasitic. Trematodes have external suckers usually for attaching to a host. Cestodes are ribbon-like flatworms.

#### *Plant Medicine and Infectious Disease DOI: http://dx.doi.org/10.5772/intechopen.103701*

While in the infected host, parasitic worms receive nourishment and protection while depriving their host of nutrients. Helminths are transmitted through water, food, soil, and vectors. An infected host can harbor the adult worm, immature stages, or their larval forms. Adult worms in their host produce eggs that can pass out through the stools of their host. Parasitic worms' infection severity depends on the number of parasites harboring in the host. Diseases can also be due to the inflammatory reaction to their eggs and larvae. Helminths are responsible for symptoms such as diarrhea, loss of appetite, fatigue, stomachache, anemia, skin rashes, fever, swellings, weakness, and weight loss [30].

#### *2.3.8 Plant medicines for parasitic worm infections*

The leaf extracts of *Adansonia digitata* exhibited anthelminthic activities [31]. *Sorghum bicolor* is considered anthelminthic in India. *Ocimum gratissimum* extracts have shown promising anthelminthic properties by their ability to inhibit glutathione S-transferases from parasitic nematodes [32]. *Momordica charantia* extract also has anthelminthic activity [33]. *Balanites aegyptiaca* also showed anthelminthic properties [34]. Plants are continuously screened and the list keeps on counting.

#### *2.3.9 Protozoa*

Protozoa are a group of one-celled eukaryotes minutes organisms either free-living or dependent on the host for support. Protozoa are non-photosynthetic and like animals depend on other matter for nutrients. Protozoa are more related to animals sharing common characteristics which include motility, lack of cell wall, etc. Their locomotive structures include the cilia (hairlike projections from the surface of their cell), flagella (a lash-like appendage that extends from the cell surface.). Some protozoa such as the amoeba moved by forming pseudopodia, a temporal outgrowth that is filled with cytoplasm flowing from the body of the cell. The parasitic protozoa form part of the major causes of infectious diseases ranging from asymptomatic to lifethreatening, depending on factors such as the nature of the pathogen and the immune status of the host organism. Parasitic protozoa can be classified based on whether they are responsible for systemic or local infections. Systemic protozoal infections include malaria, sleeping sickness, babesiosis, Chagas' disease, toxoplasmosis, and leishmaniasis. Protozoa such as *Entamoeba histolytica, Giardia lamblia* are responsible for intestinal parasitic infections. Intestinal protozoa infectious are transmitted usually by the fecal-oral route through direct contact with the infected agents by ingesting contaminated food or water [35, 36].

#### *2.3.10 Plant medicines for protozoa infections*

The efficacy of plants as a remedy for protozoal infections is remarkable. In the clinical world, plants have been the source of the clinically used antimalarial drugs; quinine from *Cinchona spp.* and artemisinin from *Artemisia annua* with the former being the blueprint for the generation of varieties of synthetic antimalarial agents. Plants agents that have been found to kill or inhibit protozoa infections happen to plants containing phytochemicals such as alkaloids and terpenes. There is a lot of scientific evidence backing the use of alkaloids and terpenes in the treatment of protozoal infections but that does not necessarily mean all plants with alkaloids or terpenes can be used for such purposes. This is because some of those agents might

have the efficacy to kill or inhibit the agents but might be harmful in man and should not be considered. Plants with efficacy against protozoa infections include *Cryptolepis sanguinolenta, Holarrhena pubescens, Alstonia boonei (Apocynaceae), Artemisia annua. Cryptolepis sanguinolenta* contained the alkaloid cryptolepine used in the treatment of malaria [37]. The plant has also shown potency in the treatment of amoebiasis [38]. *Holarrhena pubescens* contain conessine which has shown potency in the treatment of amoebic dysentery*. Alstonia* contains alkaloids such as villastonine which have shown an *in vitro* antiplasmodial activity. *Artemisia annua* contained sesquiterpene lactone artemisinin which has shown activity against malarial. Other plants used in protozoal infections include *Cinchona pubescens, Aloe vera, Phyllanthus niruri, Rauwolfia vomitoria, etc.*

## **3. Threats to plant's life**

It would not be doing enough still if our daily mission was to survive a plant life. Though that statement would not be more than fantasy when compared to what we see today, it would have survived mankind himself and his environment and created a livelihood in all his sector but would not still match all the benefits that he reaps from plants. I should say there are more bodies and resources towards the conservation of animal life than there are to survive plants life. Animals are important. They give us pet, food, leather, etc., and forms part of our society and they deserve the efforts to survive and protect them, but, are not plants that give us the ability to live to see our pets, eat meats, and use leather deserves much more attention? We do not need years of research (though they are available) to tell us hundreds of plants species are on the verge of extinction across the globe. Just a few years back, native African plants such as the *khaya senegalensis* were not easy to spot and now, it takes the journey of kilometers into a deep forest zone to spot one or two such plants. And this is happening across all the corners of the globe. If greater urgency and resources are not directed to curb the trend, it will happen earlier than expected—many species of plants will be finally extinct.

In this era where there is a rise in scientific interest in research assaying plants' phytochemicals and their potencies, it would not be long for plants to help us remedy diseases that synthetic products have failed to cure. This is happening and is not a fantasy. HIV-inhibitors named inophyllums have been isolated from *Calophyllum inophyllum*. *Ferula sumbol* has been found to contain coumarins that have shown anti-HIV activity [39]. But if these plants are extinct before they get to the laboratory, what is the hope of the world?

To talk of man involvements as threats to plants' lives, we can consider two separate concepts. One is his physical activities and two, his inactions. His activities include timber exploitations, agriculture, mining, industrialization, urbanization, etc. His inactions are his lack of concern towards the threats to plants' lives.

Man's conscious and unconscious activities threatened the lives of plants and many plants species are battling extinction as a result of such activities. Our desire for timber products instead of other variants is killing plants other than whetting our appetites. Mining, agriculture, and other activities are all gearing towards that path. All these activities result in habitat loss. The homes of these plants are converted into agricultural lands and places for livestock grazing. Industrial production and urbanization are rendering the natural habitats incapable of supporting plants life. Plants that were previously doing well in these habitats are killed in so doing reducing biodiversity.

#### *Plant Medicine and Infectious Disease DOI: http://dx.doi.org/10.5772/intechopen.103701*

Man's inaction that endangers plants lives on the other hand is the things he needed to do to immunized his physical activities that throw real danger on the plant's life that he is not doing. We are sending plants to extinction by choosing to do nothing. The logging of trees would not be so destructive as far as we replaced them. We could plant trees to replace those we cut. We could employ reafforestation to immunize deforestation. On an individual level, we could decide to plant trees in our environment as a means of providing shades, beautifying our environment, and in the process, preserving plant life. You could inform someone today of the importance of protecting plants' lives and helping spread the good news. Each and everyone can choose to do nothing or choose to do something. Whatever we choose to do, the process would not be easy. Choosing to protect plants' lives is hard. Doing nothing and watching nature fades away is hard. I am asking you today to choose your hard!

#### **3.1 Recommendations**

The journey to protecting plants' lives is everyone's job since everyone is affected positively by the presence of plants. Environmental protection agencies, governmental and non-governmental agencies, individuals, and the whole populace should awake and rethink all the practices that endanger plants species. New bodies aimed at preserving vegetations should be created and already existing ones should be strengthened. Governments, as well as individual philanthropists, should donate towards these bodies making sure they are well equipped to function. Sectors such as the farming sectors that are found of practices that endanger plants' lives should be monitored and those found guilty sanctioned. Frequent campaigned towards plants plantation should be encouraged as well as mass education on the benefits of protecting the vegetations.

Human resources are the center of all the types of resources in the sense that nothing will be meaningful and minimum rewards can be reaped from every resource without trained human resources to channel their course. Aside from preventing plants from extinction, experts should be trained to work and research on plants. Scientists already in the field should be well motivated and channels should be created for others to enter the field.

With the availability of plants and scientists to work on them, plants medicine will propel medicine to a horizon we never anticipated.

### **4. Conclusions**

The above concepts are not claiming all there is to medicinal plants and infectious diseases but it is enough to straighten the logs that were bent years ago. Medicinal plants worked magic for the ancient men and survived them and their generation. If care, enough urgency, and resources are directed towards the preservation of plants, medicinal plants will change the perspective of medicine and impacts generations to come. If we stay adamant and watched as many species of plants suffer extinctions, the world will lose this greater facet of nature and there will be no room to contain the mayhem. Diseases are with us. The world might record new outbreaks of infectious diseases, but with strategic plans that do not exclude interventions geared towards the wellbeing of medicinal plants, any kind of infectious disease can be easily controlled.
