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About infections

Types of infection

About parasitic infection


2.1. Deforestation

2.2. Replacement of forests with crop farming, ranching, small animals

2.3.Water bodies in disrupted areas

2.4. Human movement

2.5. Vector competence

2.6. Zoophyllic to anthrophyllic orientation

2.7. Water control projects

2.8. Road construction

2.9. Climate and parasitic disease

2.10. Temperature and rainfall

2.11. El NinÄo


3.1. Malaria

3.2. Leishmaniasis

3.3. Cryptosporidiosis

3.4. Giardiasis

3.5. Trypanosomiasis

3.6. Trematode

3.7. Tissue Nematodes



















A human or animal with an infection has another organism inside them which gets its sustenance (nourishment) from that person, it colonizes that person and reproduces inside them. The human with that organism (germ) inside is called the host, while the germ or pathogen is referred to as a parasitic organism. Another name for an organism that causes infection is an infectious agent. It is only an infection if the colonization harms the host i.e parasitic relationship. It feeds and multiply at the expense of the host to such an extent that the host’s health is affected adversely. The normal growth of the bacterial flora in the intestine is not an infection, because the bacteria are not harming the host.

In the light of the above this work shall enable us understand how parasitic infection causative agents like malarial parasite species and their vectors respond sharply to changes in the ecology of their habitat: deforestation, vegetation, density of human population, bodies of water and their locations and climate Africa and the world at large.

It will be good to indicate that this work is divided into 3 chapters with which the topic under study was exhausted. Chapter 1 was used to explain all basic terms, at chapters 2 and 3 the topic of research was dealt with in detail as the main body of the work.

The work also contained conclusion and references.










Parasitic Infections,



Density of Human Population,

 Water bodies




















Infection is the invasion of a host organism’s bodily tissues by disease causing organisms, their multiplication, and the reaction of host tissues to these organisms and the toxins they produce. Infections are caused by infectious agents such as viruses, viroids, and prions, microorganisms such as bacteria, nematodes such as roundworms and pinworms, arthropods such as ticks, mites, fleas, and lice, fungi such as ringworm, and other macro-parasites such as tapeworms. Hosts can fight infections using their immune system. Mammalian hosts react to infections with an innate response, often involving inflammation, followed by an adaptive response. Pharmaceuticals can also help fight infections.

The branch of medicine that focuses on infections and pathogens is known as infectious disease medicine.


From an epidemiological point of view BVD virus is extremely successful. It occupies a special place among viral pathogens thanks to its world-wide distribution and high rate of infection. It’s success is due to a combination of two well-known strategies, the “hit-and-run” strategy and the “infect-and persist” strategy. Both of these strategies are popular among viruses, however, they are rarely used in combination.

-Hit & Run (transient infection)

The hit and run strategy means that the viruses make use of a relatively short period of susceptibility to infection in their host population in order to multiply and thus for survival. Following the multiplying of the virus the hosts either develop antibodies (BVD) or else die from the disease (e.g. rabies, Ebola). By this strategy the virus robs itself of its own basis for survival and has to rely on continuously finding new susceptible hosts.

In the case of BVD, the hit and run strategy manifests itself in a transient infection which is frequently without symptoms. The animals then develop antibodies which protect them from a repeat BVD infection for the rest of their relatively short life. The hit & run strategy on its own turned out to be insufficient for the survival of BVDV, i.e. without PI animals, the virus will disappear sooner or later.

-Infect & Persist (persistent infection)

Viruses with the ability to persist in their host have an advantage: they simply wait until a new opportunity for infection presents itself. Various viruses, such as Lenti viruses or herpes viruses, use this strategy. However, the persistent infection caused by BVDV is unique in the sense that the virus simply evades the immune system of the host altogether by infecting the individual prior to attainment of immune competence. The virus refrains from damaging its host in such a way as to prevent development. The host develops an immune tolerance towards the virus, i.e. the immune system considers the virus to be part of the body.



A parasitic infection is a disease caused or transmitted by a parasite. Many parasites do not cause diseases. Parasitic diseases can affect practically all living organisms, including plants and mammals. The study of parasitic diseases is called parasitology.

Some parasites like Toxoplasma gondii and Plasmodium spp. can cause disease directly, but other organisms can cause disease by the toxins that they produce.

Although organisms such as bacteria function as parasites, the usage of the term “parasitic disease” is usually more restricted. The three main types of organisms causing these conditions are protozoa (causing protozoan infection), helminths (helminthiasis), and ectoparasites. Protozoa and helminths are usually endoparasites (usually living inside the body of the host), while ectoparasites usually live on the surface of the host. Occasionally the definition of “parasitic disease” is restricted to diseases due to endoparasites.

Causes of Infections

Mammals can get parasites from contaminated food or water, bug bites, or sexual contact. Ingestion of contaminated water can produce Giardia infections. Parasites normally enter the body through the skin or mouth. Close contact with pets can lead to parasite infestation as dogs and cats are host to many parasites.

Other risks that can lead people to get parasites are walking bare feet, inadequate disposal of faeces, lack of hygiene, close contact with someone who carries specific parasites, eating undercooked or exotic foods.


Symptoms of parasites may not always be obvious. Actually, such symptoms may mimic anemia or a hormone deficiency.[4] Some of the symptoms caused by several worm infestation can include itching affecting the anus or the vaginal area, abdominal pain, weight loss, increased appetite, bowel obstructions, diarrhea and vomiting eventually leading to dehydration, sleeping problems, worms present in the vomit or stools, anemia, aching muscles or joints, general malaise, allergies, fatigue, nervousness. Symptoms may also be confused with pneumonia or food poisoning.


The effects caused by parasitic diseases range from mild discomfort to death. The nematode parasites Necator americanus and Ancylostoma duodenale cause human hookworm infection which leads to anaemia and protein malnutrition. This infection affects approximately 740 million people in the developing countries, including children and adults, of the tropics specifically in poor rural areas located in sub-Saharan Africa, Latin America, South-East Asia and China. Chronic hookworm in children leads to impaired physical and intellectual development, school performance and attendance are reduced. Pregnant women affected by a hookworm infection can also develop aneamia which results in negative outcomes both for the mother and the infant. Some of them are: low birth weight, impaired milk production, as well as increased risk of death for the mother and the baby.


Albendazole and mebendazole have been the treatments administered to entire populations to control hookworm infection. However, it is a costly option and both children and adults become reinfected within a few months after deparasitation occurs raising concerns because the treatment has to repeatedly be administered and drug resistance may occur.

Another medication administered to kill worm infections has been pyrantel pamoate. For some parasitic diseases there is no treatment and in the case of serious symptoms, medication intended to kill the parasite is administered, while in other cases, symptom relief options are used.[8] Recent papers have also proposed the use of viruses to treat infections caused by protozoa.



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